review article properties and microstructures of sn-ag-cu

Review ArticleProperties and Microstructures of Sn-Ag-Cu-X Lead-Free SolderJoints in Electronic Packaging

Lei Sun and Liang Zhang

School of Mechanical and Electrical Engineering Jiangsu Normal University Xuzhou 221116 China

Correspondence should be addressed to Liang Zhang zhangliangjsnueducn

Received 6 October 2014 Accepted 23 November 2014

Academic Editor Hossein Moayedi

Copyright copy 2015 L Sun and L ZhangThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanicalproperties However there are also many problems that need to be solved for the SnAgCu solders such as high melting point andpoor wettability In order to overcome these shortcomings and further enhance the properties of SnAgCu soldersmany researcherschoose to add a series of alloying elements (In Ti Fe Zn Bi Ni Sb Ga Al and rare earth) and nanoparticles to the SnAgCusolders In this paper the work of SnAgCu lead-free solders containing alloying elements and nanoparticles was reviewed and theeffects of alloying elements and nanoparticles on the melting temperature wettability mechanical properties hardness propertiesmicrostructures intermetallic compounds and whiskers were discussed

1 Introduction

Tin-lead (SnPb) solders have been widely used in electronicpackaging However due to the increasing environmentaland human health concerns over the toxicity of lead govern-ments of many countries have established laws to prohibit theuse of Pb from electronic applicationTherefore investigationof lead-free solder has become an important research topic inthe field of electronic packaging

In recent years to replace the conventional Sn-Pb solderalloys several types of Sn-based lead-free solders such asSnAg SnCu SnZn SnBi SnIn and SnAgCu have beendeveloped Among series of lead-free solders SnAgCu hasbeen proposed as the most promising lead-free solder forreplacement of traditional tin-lead solder owing to its goodreliability excellent creep resistance and thermal fatiguecharacteristics [1ndash3] However there are still many unre-solved issues For example SnAgCu solder has a highmeltingpoint poor wettability coarser microstructures and so forthIn order to further enhance the properties of lead-freesolder two methods are taken The first method is to addalloying elements to the SnAgCu solder such as Ga elementwhich can improve the wettability And the addition of rareearth elements can enhance the comprehensive performance

Another method is to add micro- or nanoparticles It mainlycomprises of metal particles compound particles ceramicparticles the carbon nanotubes and the polymer particlesWith the changes of added particles in its type and sizethe properties of SnAgCu solder are different Not onlycan adding metal particles change the microstructure of thesolder but also there will be a new phase in the solder matrixwhile adding compound particles or ceramic particles cannotform a new phase

In this review we summarize the development of SnAgCusolder alloys and analyze the effects of adding the fourthelements on the melting temperature wettability mechanicalproperties hardness properties microstructures and inter-metallic compounds (IMC) At the same time we will alsodiscuss the Sn whisker and some suggestions have been putforward which maybe solve this issue

2 Melting Temperature

Melting temperature is an important factor for the devel-opment of new lead-free solders A promising solder alloyshould have a lowmelting temperature and a narrowmeltingrange [4] As we all know the eutectic SnPb has a meltingpoint of 183∘C while the SnAgCu solder melting point is

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 639028 16 pageshttpdxdoiorg1011552015639028

2 Advances in Materials Science and Engineering

217∘C 34∘C higher than that of the eutectic SnPb Such highmelting temperature will increase the reflowing temperatureand lead to thermal damage of the polymer substrate [5]Meanwhile it also enhances the dissolution rate and solubilityof Cu in the molten solder thus improving the rate of for-mation of IMCs This is the reason that the IMCs layerof SnAgCu thicker than Sn-Pb Hence some researchersexpect to add the fourth elements to decrease the meltingtemperature of SnAgCu solders

Trace amount of indium (In) added to the SnAgCu lead-free solder can change the melting behavior obviously Itwas shown in the literature [6] that adding 30 wt of Inthe solidus and liquidus temperatures decreased 217 and115∘C respectively as compared with 2194 and 2417∘C forthe Sn03Ag07Cu solder But the In is very expensive theaddition of In can increase the cost of lead-free soldersChuang et al [7] proposed that the effect of Ti on themelting point of Sn35Ag05Cu (SAC) solder alloy With theaddition of Ti element the melting temperatures changeslightly The liquidus temperatures are 22095 22086 and21947∘C for the SAC-xTi solder alloys with Ti contents of025 05 and 10 wt respectively Moreover the meltingrange is decreased from 466 to 288∘C Generally speakingthe narrow melting range of the solder means excellentthermal properties It is mainly attributed to the narrowmelting range explaining that solders exist as part liquidfor a very short time during solidification and can formreliable joints during the reflow process Figure 1 representsthe differential scanning calorimetry (DSC) curve of SnAgCubearing different manganese (Mn) and titanium (Ti) It isindicated that Sn30Ag05Cu solder has only one endother-mic peak yet it has two peaks for the Sn10Ag05Cu (SAC)solder Meanwhile worthy of notice is that the degree ofundercooling for proeutectic Sn was significantly affected bythe addition of trace alloying elements (Mn and Ti) intoSAC solder alloyThe SAC-05Ti sample showed an extremelysuppressed undercooling of only 4∘C [8] The addition ofFe into SnAgCu solder did not change much of the meltingtemperature [9]The DSC results demonstrated a single peakof Sn36Ag09Cu solder However there are two obviousendothermic peaks (220∘C and 235∘C) that appear for theSnAgCu-02Fe solder alloyThis shows that melting occurredover a range of temperatures It may be ascribed to the peaksoverlapped the first peak may indicate that the solder waspartially fused The addition of Fe most likely resulted inshifting of the melting point from the eutectic point to nearthe eutectic point and the melting point of the solder isin the range of 22287 to 230∘C which is higher than theSnAgCu solder melting point (217∘C)When adding 06 wtFe only a single endothermic peak at 22135∘C was foundshowing that it has a eutectic composition El-Daly et al[10] studied the DSC profiles of Sn10Ag03Cu solder TheDSC revealed two endothermic peaks between 2201∘C and2272∘C The two peaks indicated two steps in the meltingprocess of SnAgCu solder Based on the ternary SnAgCuphase diagram [11] the two steps were owed to the melting ofternary eutectic 120573-Sn + Ag

3Sn + 120578Cu

6Sn5phase and primary

120573-Sn However for SnAgCu solder containing Zn only oneendothermic peak appears in the DSC curve and the melting

22

20

18

16

14

12

10

8

6

4

2

0

Hea

t flow

(120583W

)

200 210 220 230 240 250 260

Temperature (∘C)

05Mn015Ti05Ti

305

105

015Mn

2∘Cmin

(a)

05Mn015Ti05Ti

305

105

015Mn

2∘Cmin

30

20

10

0

Hea

t flow

(120583W

)

180 190 200 210 220 230 240

Temperature (∘C)

minus10

minus20

minus30

(b)

Figure 1 DSC curves of the samples (a) upon heating and (b) uponcooling [8]

temperatures were 2228 and 2208∘C for the SAC-20Znand SAC-30Zn respectively The addition of Bi decreasesthe melting point of Sn38Ag07Cu (SAC) solder [12] It isfound that the solidus temperatures of SAC-20Bi and SAC-40Bi were 21308 and 20640∘C respectively However whenadding too much Bi solder joint peeling will appear DSCscan of low-Ag Sn05Ag07Cu (SAC) solder bearing Ni andthe results showed that the addition of Ni had little effecton the melting temperature [13] The peak temperatures ofSAC SAC-005Ni and SAC-01Ni solders were 2211 2229and 2234∘CMoreover the values of melting range were 126119 and 128∘C for the SAC SAC-005Ni and SAC-01Nirespectively It is very close to 115∘C for the SnPb solder [14]It was also reported in the literature [15]

Advances in Materials Science and Engineering 3

It is well known that the addition of a small amount of REelements in the metals can greatly enhance their properties[16] However it does not significantly alter themelting pointThe DSC curves of Sn39Ag07Cu and Sn39Ag07Cu05REsolders were studied by Dudek and Chawla [17] all soldersshow a single endothermic peak between 217∘C and 219∘Cshowing the onset of melting for the SnAgCu solder It isrevealed that the addition of RE elements into Sn39Ag07Cusolder did not affect the melting characteristics Moreoverit is also found that the addition of La exhibits minimalimpact while the addition of Ce and Y increases the onsettemperature by approximately 2∘C

Recently many researchers are also investigating theaddition of nanoparticles into SnAgCu solders for pro-viding better properties and microstructures Xiang etal [18] reported that the addition of Mn nanoparticlesdid not change significantly the melting temperature ofSn38Ag07Cu (SAC) solder alloyThe results showed that theonset melting temperatures of SAC-012Mn SAC-018Mnand SAC-047Mn composite solders were 217∘C 2173∘C and2175∘C respectively Small amounts of SiC nanoparticlesadded to the Sn38Ag07Cu solder do not change muchof the melting temperature The well-defined endothermicpeak shifts from 2199∘C to 2189∘C with the addition of02 wt SiC [19] Al

2O3nanoparticles have been added to

the Sn35Ag05Cu solder alloy During the heating processof the DSC analysis the Sn35Ag05Cu solder exhibited aeutectic alloy with a melting point of 2212∘C which hasbeen increased slightly with the increase of the amount ofnano-Al

2O3particles [20] To identify the effects of different

joint fabrication methods and the amount of TiO2addition

on the Sn30Ag05Cu (SAC) solder DSC analysis was usedDSC analysis was used The results showed that the meltingpoint of SAC solder and the solder bearing 1 wt TiO

2nano-

particles ranged from 217∘C to 21764∘C with only a eutecticpeak [21] A similar phenomenon in other studies on theSAC composite solders was observed [22] DSC analysis wascarried out to understand the influence of ZnO nanopar-ticles addition to the Sn35Ag05Cu (SAC) solder on itsmelting temperature From DSC results it is indicated thatthe melting temperatures of plain SAC solder and SAC-05ZnO composite solder were about 22118∘C and 22216∘Crespectively with only a eutectic peak [23] The meltingbehavior of Sn30Ag05Cu solder reinforced with nanosizedZrO2particles were studied by Gain and Chan [24] The

melting temperature was increased by less than 1∘C when theamount of ZrO

2nanoparticles was 1 wt

In summary adding alloying elements and nanoparticleon the melting temperature has little effect However thenew lead-free wave soldering and reflow oven that can makesoldering below 250∘C have been developed Therefore theabove elements added to the SnAgCu solder can meet therequirement of the present soldering process and there isno need to make adjustment in the current reflow processBesides in future research we may only need to ensure thatthe addition of elements can slightly influence the melting ofSnAgCu solders

3 Wettability

Wettability of solder can be defined as the ability of themolten solder to spread over on a substrate during the reflowprocess [25] For the reflow process the heating temperatureat a certain condition only a good wettability to the surfaceof the base material to form good wet spreading jointsnamely which is to form solder joints And the solder jointsbear the entire electronic device the role of mechanicalsupport and electrical connections thus the solder jointsdirectly determine the performance of electronic productsFor traditional SnPb solder due to the existence of Pbthe solder alloy owns better wettability But for lead-freesolders the wettability may be dropped obviously due tothe replacement of Pb In order to improve the wettabilityof solder the addition of alloying element is a hot researchinvestigator Generally there are many methods to measurethe wettability but the wetting balancemethod and spreadingmethod are considered the relatively versatile methods

The addition of a small amount of In into SnAgCu solderwas investigated by Moser et al [26] The wetting anglewas decreased from 37∘ to 22∘ with the addition of 75 atof In The wetting balance tests were conducted in air toshow the wettability of Sn36Ag09Cu-xFe by Fallahi et al[9] It is found that the addition of 02 wt Fe increasedthe wetting force and reduced the wetting angle Howeverthe Fe was added to more than 06 wt which resultedin a lower wettability Zn element was incorporated intoSn38Ag07Cu solders by Zhang et al [27] The wettabilityof SnAgCu solders can be improved with the addition ofZn When the content of Zn was up to 08 Sn38Ag07Cusolder got the smallest angle However with the addition of3Zn wetting angle was the largest This can be attributedto the Zn is easily oxidized the formation of oxide residueduring soldering may worsen the wettability of SnAgCusolder The addition of trace amount of Bi into SnAgCusolders can change the wetting behavior Rizvi et al [28]demonstrated by experiment that the effect of 10 wt Bion the wetting behavior of Sn28Ag05Cu solder comparedwith Sn-37Pb alloy It is indicated that the wetting behaviorof Sn28Ag05Cu10Bi solder is less than that of the traditionSnPb solder for all flux types and solder bath temperaturesHowever due to a high soldering temperature promotethe diffusion process thus reducing the wetting angle andimproving of the wetting behavior Moreover the wettingbehavior of Sn28Ag05Cu10Bi solder on Ni substrate waslower than that on Cu substrate Researchers attribute toNi atoms diffused into the solder through the intermetalliccompounds (IMCs) much slower than did the Cu atomsMoser et al [29] have also investigated the effect of Bi onthe SnAgCu solder under Ar-H

2protective atmosphere and

found that the Ar-H2atmosphere can better decrease the

surface tension and improve the wettability It is due to inertgas may protect the solder decreases the chance of liquidsolder in contact with oxygen Sn05Ag07Cu solder bearingGa elementwas researched by Luo et al [30]The results showthat the wetting time and wetting forces vary as a function ofGa when the Ga was added to the Sn05Ag07Cu solder upto 05 resulting in a decrease in the values of mean wetting


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0

Wet

ting

angl

e (∘)

Wet

ting

forc

e (m

N)

12

10

8

6

4

2

0

Wetting angleWetting force

Sn-Ag-Cu Sn-Ag-Cu-005RE

Sn-Ag-Cu-01RE

Sn-Ag-Cu-025RE

Figure 2 Wetting angle and force of Sn35Ag07Cu-xRE [35]

time (the wetting force exhibits the increase trend) With afurther increase of Ga addition increase of the wetting timecan be found Because of the surface-active feature of Ga Gawould accumulate at solder interface in themelting state thenthe surface tension of the liquid solder was decreased [31]Hence the new composite solders showed better wettabilityLu et al [32] confirmed that the addition of Mg element intoSnAgCu solder alloy worsens the wetting behavior becauseMg is very prone to oxidation and the formation of oxidefilm increases the surface tension of the liquid solder thushindering the solder from spreading over the Cu substrate

Rare earth (RE) elements have been called the ldquovita-minrdquo of metals which means that a small amount of REelements can obviously enhance the properties of metals[33] In a series of performance of lead-free solder thewettability of adding rare earth elements is the most obviousimprovement Yu et al [34] has investigated the effect ofRE elements (Ce and La) on the SnAgCu solder wherethe soldering temperature was 250∘C and RMA flux wasused It is found that the wetting angle of Sn25Ag07Cuis higher than Sn35Ag05Cu because of the higher meltingpoint of Sn25Ag07CuAndwhenRE is less than 01 wt thewetting angle of Sn35Ag07Cu decreased with RE increasesWhereas the content is higher than 01 wt thewetting anglewill increase Similar result was found by Law et al [35]Figure 2 shows that the wetting angle was decreased withthe addition of RE elements However an excessive amountof RE element addition the wetting angle will increase Theheavy rare earth element Y can improve the wettability ofSn38Ag07Cu solder and the spreading areas increased andthe contact angles decreased as the content of Y increasedWhen adding 015 wtY the spreading areas and thewettingangles reached the peak but when Y exceeded 015 wtthe wettability of the composite solder decreased obviously[36] Trace rare earth element Er was incorporated intoSn38Ag07Cu solder which can change the wetting behavior[37] When the content of Er is less than 025wt thespreading areas will increase with the addition of Er elementHowever as the content of Er element continues to increase

Sn-Yb particleSolder

Cu substrate

Figure 3 Schematic of Yb effect on wetting angle [40]

up to 10 wt the spreading areas will decrease The wettingbehavior of SnAgCu solder is improved with the addition ofPr element Gao et al [38 39] found that trace amount ofPr and Nd addition could remarkably improve the wettingbehavior of Sn38Ag07Cu solder where the optimal wettingbehavior was achieved as the RE content is about 005wtbecause of the lower surface tension caused by RE elementsThe addition of Yb into SnAgCu was investigated by Zhanget al [40] As a result the contact angles decreased as thecontent of Yb increasedWhen the addition of Yb was 005the contact angle can decrease to the peak value but as theYb content exceeded 005 the contact angles increasedobviously Due to the higher affinity Sn of rare earths in thesolder alloys Firstly the Sn tend to react with Yb to form Sn-Yb particles and the reaction is easy to go on when the Sn-Yb particles adhere to the substrate to nucleate particularlyfor the nucleation of particles at the triple point in Figure 3when the particles exist at the triple point the balance amongthe gas solid and liquid will be broken Effects of additionof rare earth element Ce atmosphere and temperature onthe wetting behavior of SnAgCu-xCe solders were studied byWang et al [41] The results indicate that with the addition ofCe thewetting behavior of Sn38Ag07Cu solders is improvedobviously With the addition of 003 to 005 the wettingtime is about 07 s at 250∘C which is very close to the Sn-Pbsolder Moreover in N

2atmosphere the wetting behavior of

SnAgCu solder is extremely improved Due to the oxidationof molten solder and substrate is inhibited in N

2atmosphere

Furthermore Zhao et al [42] also found that the spreadingarea was increased with the increasing of the content of CeWhen the Ce addition is 01 the Sn30Ag28Cu-Ce has themaximum spreading area of 24280mm2 However as thecontent of Ce is over 01 the spreading areas will decrease

In a word the addition of rare earth elements can changethe wetting behavior there are two reasons leading to theresult in one aspect rare earth is a surface-active element thatcan reduce the surface tension of liquid solder In the otheraspect rare earth is liable to oxidation thus the formationof excessive amount of oxide residue during soldering maydeteriorate the wettability of the solder thereby affecting thespreading properties [43]

Currently with the advancement of nanotechnologythrough the years more and more researchers try to addnanoparticles to improve the comprehensive performance ofSn-Ag-Cu lead-free solders

The addition of Mn nanoparticles into SnAgCu solderworsens the wetting behavior With the addition of 047wtof Mn nanoparticles the wetting angle of SnAgCu solder was


increased from 1071∘ to 256∘ and the spreading rate of thesolder was also reduced from 889 to 774 It is causedby the increased viscosity for the addition of nanoparticlesduring soldering [18] Tay et al [44] found that the addition ofNi nanoparticles alters the wettability of Sn38Ag07Cu solderalloy Results showed that the addition of Ni nanoparticlesinto SnAgCu solder leads to thewetting angle increasing from193∘ to 299∘ For Sn38Ag07Cu solder bearing Co nanopar-ticles the effect of Co nanoparticles on wettability was foundby Yoon et al [45] With the Co nanoparticles addition con-centration increasing the wetting angle increased and thespreading rate decreased Similar effects were reported byHaseeb et al [46 47] Al

2O3nanoparticles can significantly

change thewetting behavior of Sn35Ag05Cu solderThewet-ting angle of SnAgCu solder was decreased with the additionof Al2O3nanoparticles a minimum angle of 289∘ can be

found with 05 nano-Al2O3particles addition [20] Li et al

[48] produced Sn30Ag05Cu solders bymechanicallymixingTiO2nanoparticles and pointed out that trace amount of

TiO2nanoparticles can effectively affect the wetting behavior

of Sn30Ag05Cu solder It is clear that the wetting time canbe decreased by 537 and the wetting force can be increasedby 376 with the addition of 025TiO

2particles Liu et

al [49] studied the addition of graphene nanosheets (GNSs)into Sn30Ag05Cu solders using the powder metallurgy Theresults show in SAC-xGNS solder that with GNSs additioncontent increasing the contact angle was decreased Whenthe content of GNSs was 01 the contact angle can bedecreased by 155 Nai et al [50] investigated the effect ofnonreactive and noncoarsening foreign enhancements on thewettability of SnAgCu solder It is found that the wettingangles were reduced by 157 and 198 with the additionof 004 and 007 of carbon nanotubes (CNTs) Han et al[51] also found that the addition of trace amount of Ni-coatedcarbon nanotubes (Ni-CNTs) did significantly improve thewettability of SnAgCu solder

In conclusion the addition of nanoparticles did notsignificantly affect the wettability of SnAgCu solders andmay even deteriorate the wetting angles However accordingto Kripesh et al [52] the wetting quality is considered asldquovery goodrdquo when the value is 0∘ lt 120579 lt 20∘ For the value20∘ lt 120579 lt 40∘ it is considered as ldquogood and acceptablerdquoThe wetting behavior is ldquobadrdquo when 120579 gt 40∘ Therefore withthe addition of nanoparticles the wetting angle of SnAgCucomposite solder is in the acceptable range Moreover differ-ent researchers obtained different result It may be attributedto solder composition soldering temperature processingatmosphere flux type substrate metallurgy and so on

4 Mechanical Properties

The mechanical property is an important index to evaluatesolder properties It plays a vital role in the reliability of solderjoints

The effect of In element on the tensile strength of low-Ag Sn03Ag07Cu solder was studied by Kanlayasiri et al [6]With the 30 wt In added the tensile strength of SnAgCuincreases approximately by 79 The addition of Ti can

Table 1 Tensile strength of Sn35Ag07Cu-xSb [55]

Ageing time (h) SAC SAC-08Sb SAC-20SbUTS (MPa) UTS (MPa) UTS (MPa)

0 4663 5238 4455200 3973 4762 4597400 3482 4371 3980600 3309 4529 3605

remarkably increase the mechanical properties of SnAgCusolder However with the addition of Ti being over 10 wtthe mechanical properties of Sn35Ag05Cu were decreaseddue to the appearance of coarse Ti

2Sn3in the eutectic colonies

[7] Fe element can increase the shear strength of SnAgCusolder Fallahi et al [9] found that the shear strength ofSn36Ag09Cu solder was 29Mpa with the addition of Febeing 02 wt and 06wt the shear strength was raised upto 40MPa and 53MPa When 08 wt of Zn was added tothe Sn38Ag07Cu solder the tensile force of SnAgCu solderjoint can be improved by 10 With further increase of Zncontent the tensile force decreases evidently It is attributedto the fact that Zn has stronger affinity for oxygen and anexcessive amount of Zn addition will form superfluous Zn-oxidesTherefore the mechanical properties of SnAgCu-xZnsolder joints were decreased [27] The similar strengtheningeffect of Zn on the tensile strength of SnAgCu was alsofound by Song et al [53] Bi element can also improve themechanical properties of SnAgCu solder When the additionof Bi was 20 wt an improvement of 47 of the ultimatetensile strength (UTS) was achievedWhen the addition of Biwas 40 wt the UTS was almost 2 times that of SnAgCusolder [12] Ni can enhance the mechanical properties ofSn20Ag05Cu solder which was studied by El-Daly and El-Taher [54] It is found that the ultimate tensile strength (UTS)and yield strength (YS) both increased with the increasingamount of Ni The tensile strength of SnAgCu solder jointbearing Sb was investigated by Li et al [55] as shown inTable 1 Results showed that the addition of Sb can obviouslyimprove the tensile strength of SnAgCu solder alloys andjoints during the ageing time The reason could be attributedto solid solution hardening and particle hardening Luo et al[30] reported that the shear strength of Sn05Ag07Cu solderjoint can be improved with the addition of Ga When theaddition of Gawas up to 05 wt shear strength gives a 179increase

Adding an appropriate amount of rare earth elementsmainly containing Ce and La elements can remarkablyincrease the mechanical properties of SnAgCu solder [34]as shown in Figure 4 Moreover with the increasing of Agthe tensile strength is also improved The strength ofSn38Ag07Cu solder joint was improved with Y additionHowever when the Y content exceeds 015 wt the strengthof joint has a dramatical decrease [36] With the addition ofEr the shear strength of Sn38Ag07Cu solder was improvedsignificantly When the Er addition is up to 01 wt givena 18 increase compared with SnAgCu solder [37] Themechanical properties of Sn38Ag07Cu solder joint bearing


70

65

60

55

50

45

120590(M

Pa)

Sn-25Ag-07CuSn-35Ag-07Cu

Sn-25Ag-07Cu-01RESn-25Ag-07Cu-025RE

Figure 4 Tensile properties of SAC-RE [34]

Pr was studied by Gao et al [38] Both the pull force andshear force were gradually increased with the increase ofPr content When the Pr addition is up to 005wt thesesamples showed 185 and 194 higher on the pull forceand shear force respectively However when the Pr contentwas over 025wt the results showed a sharp decline in thestrength of SnAgCu solder The simple enhancement effectwas found in SnAgCu bearing Nd the pull force and shearforce of the solder joint give 194 and 236 increase [39] Asa surface-active element rare earth Yb can also improve thetensile strength of Sn38Ag07Cu solder joints inQFPdevicesWhen the Yb content was up to 005wt the tensile forcewas increased by 254 [40]

The addition of Fe microparticles to the SnAgCu solderpaste was investigated by Yan et al [56] It is found that bythe addition of 10 wt Fe micoparticles the shear strengthof SnAgCu solder can be improved by 39 Gain et al[57] develop a series of Sn35Ag05Cu composite soldersreinforced with different weight percentages (0 05 1 and3wt) of Al nanoparticles The Sn35Ag05Cu compositessolder joints containing 3wt Al nanoparticles consistentlydisplayed a higher shear strength than that of originalSnAgCu solder joints and a low Al nanoparticles contentas a function of reflow cycles and aging time because of asecond phase dispersion strengthening mechanism by theformation of fine Sn-Ag-Al IMC as well as a controlledfine microstructure Tsao et al [58] studied the effects ofAl2O3doping on the properties of Sn35Ag05Cu solders

They found that by the addition of 1 wt Al2O3 the shear

strengths increased by 144 and 165 after 1 cycle and 8cycles of reflow TiO

2nanoparticles can improve the tensile

strength of Sn30Ag05Cu solder When the TiO2nano-

particles content was 01 wt the tensile strength can beenhanced from 487MPa to 532MPa [59] Roshanghias etal [60] revealed that the 02 yield stress and UTS bothincreased with addition of CeO

2nanoparticles It is mainly

attributed to the presence of CeO2nanoparticles in the

Sn35Ag07Cu solder matrix acting as obstacles for disloca-tion motion resulting in enhancement in the applied stressrequired to move dislocations TiB

2nanoparticles can also

enhance the mechanical properties of SnAgCu solder whenthe addition of TiB

2was 3 vol an improvement of 23 for

UTS and 26 for YS was observed [61] Yang et al [62] foundthat the addition of 005wt Ni-coated carbon nanotubes(Ni-CNTs) can improve the tensile strength of SnAgCu solderslabs and joints It is due to CNTs as reinforcements act asan obstacle to suppress the initiation of dislocation motionin the SnAgCu solder matrix Kumar et al [63] also reportedthat the addition of single-wall carbon nanotube (SWCNT)can improve the mechanical properties of Sn38Ag07Cusolder Results showed that the ultimate tensile strength ofSAC-10SWCNT was about 50 higher than that of theplain SnAgCu solder The addition of graphene nanosheets(GNSs) can improve the tensility of Sn-Ag-Cu solder Withthe content of 003wt GNS the ultimate tensile strengthwas increased approximately 10 [49]

In a word the addition of alloying elements and nanopar-ticles can significantly enhance themechanical properties andimprove the reliability of SnAgCu solder However when theaddition is excessive the negative effect can be found obvi-ously It is attributed to the characteristic of the material Forexample an excessive amount of rare earth additionwill formsuperfluous RE-oxides which will degrade the mechanicalproperties of the solder joint For the nanocomposite solderthe addition of nanoparticles can act as nucleation in themolten solder thus improving themechanical properties Buttoo much addition can reduce the mechanical propertieswhich can be attributed to the agglomeration of nanopar-ticles Therefore selecting the appropriate content is veryimportant

5 Hardness Properties

The measurement of hardness especially Vickers micro-hardness is a usual method to characterize the mechanicalproperties of solder The microhardness of the solder is oftenconnected with how the metallic material resists wearing orabrasion It also determines the applicability under variouscircumstances [64]

Adding In element to the SnAgCu solder will affectits microhardness by changing its microstructure Whenthe addition of In was 30 wt the microhardness ofSn03Ag07Cu solder was increased by 81 [6] The additionof Ni and Zn into Sn20Ag05Cu solder was reported by El-Daly and El-Taher [54] It is found that the microhardnessof SAC-005Ni and SAC-05Zn solders was increased to 122and 126Hv respectively as compared with 114Hv of Sn-Ag-Cu solder Lin et al [8] investigated the effects of Ti and Mnaddition on hardness of Sn-Ag-Cu solder alloy as shown inFigure 5The experimental results indicated that the hardnessvalues of Ti

2Sn3and MnSn

2were 91 plusmn 02 and 89 plusmn 01GPa

Moreover the Youngrsquos moduli determined from nanoinden-tation experiments were as follows 1517 plusmn 2GPa for Ti

2Sn3

and 1439 plusmn 1GPa for MnSn2 The intermetallic compounds

induced by alloying elements were obviously harder andstiffer than Cu

6Sn5andAg

3SnTherefore enhanced hardness


12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)

Cu6Sn5 Ag3Sn MnSn2 Ti2Sn3

Hardness (Gpa)Modulus (Gpa)

Figure 5 Nanoindentation results of the intermetallic phases [8]

of SnAgCu solder was achieved in this trial by adding Ti andMn The rare earth La can also influence the microhardnessof Sn30Ag05Cu solder which was investigated by Zhou etal [65] With the addition of La the microhardness of 120573-Snand eutectic area was enhanced from 138 to 164Hv and from168 to 188Hv respectively With the Al and Ni nanopar-ticles addition the hardness of SnAgCu solder can also beimproved [66]The addition of Cu Ni andMo nanoparticlesinto Sn38Ag075Cu solder was studied by Mohankumar andTay [67] The results showed that with Cu Ni and Moaddition concentration increasing hardness was enhancedMeanwhile it is also found that theMonanoparticles increasethe hardness value apparently higher than Ni and Cu Thehardness values of SnAgCu composite solders follow a trendwith Mo gt Ni gt Cu The amount of Al

2O3nanoparticles

can enhance the microhardness of Sn35Ag05Cu solderand increase the range of from 85 to 523 [20] TheCeO2nanoparticles can alter the microhardness value of

Sn35Ag07Cu composite solders It is found that the increaseof the amount of CeO

2can increase the microhardness

value [60] The researchers attributed this to the presenceof hard CeO

2nanoparticles reinforcement in the solder

matrix as well as higher constraint to the localized matrixdeformation The Sn38Ag07Cu solder containing 005wtSiC nanoparticles can increase the microhardness by 44compare with the plain solder [19] The microhardness ofSn30Ag05Cu bearing POSS molecules was studied by Shenet al [68] The microhardness increased with the increaseamount of POSS molecules Furthermore with the additionof 5 wt POSS the microhardness of SnAgCu solder wasreduced which can be attributed to the agglomeration ofPOSS molecules and the appearance of a coarse lath-shapedstructure in solder matrix

6 Microstructures

Material properties depend on the microstructure The typ-ical microstructures of SnAgCu lead-free solder alloys aremade up of primary 120573-Sn grains platelet-type Ag

3Sn and

Figure 6 The microstructure of SnAgCu solder [69]

scallop-type Cu6Sn5[69] (Figure 6) According to a disper-

sion strengthening mechanism uniform microstructure haspositive effects on the enhanced mechanical properties of thesolder joint

Kanlayasiri et al [6] have found that by the additionof In into SnAgCu solders the Sn-rich phase and the inter-metallic compounds become much finer and more uniformTi element can change the microstructure of Sn35Ag05Cusolder With the addition of 10 wt Ti the grain sizeof 120573-Sn was about 48 plusmn 17 120583m and the width of theeutectic area was 12 plusmn 04 120583m as compared with 248 plusmn59 120583m and 68 plusmn 28 120583m for the Sn35Ag05Cu solder Itwas attributed to the unique properties of active elementTi which can enhance appearance of heterogeneous inter-metallic compounds and a morphological change of IMC[7] Shnawah et al [70] compared the Sn30Ag05Cu solderwith Sn10Ag05Cu solder and found that the Sn30Ag05Cuhas smaller primary 120573-Sn dendrites and wider interdendriticregions than Sn10Ag05Cu In addition with the additionof Fe element a large FeSn

2intermetallic compound was

formed and caused a weak interface with the 120573-Sn matrixTrace amount of Mg into SnAgCu solder will cause theeutectic phases to become coarsened and the fraction ofeutectic microstructure will decrease [32] The addition ofAl can change the microstructure of Sn10Ag05Cu solderResults showed that the primary 120573-Sn dendrites were refinedand the interdendritic regions were enlarged Moreover theformation of Ag

3Sn and Cu

6Sn5intermetallic compounds

was suppressed And the Ag3Al and Al

2Cu intermetallic

compounds were found [71] Zhang et al [27] in their studyon Zn-doped SnAgCu solder found that Zn can significantlyrefine the dendrite 120573-Sn and when the Zn was 08 thedispersed Cu-Zn intermetallic compounds was formed Themicrostructure and mechanical properties of low Ag-contentSn05Ag07Cu solder doped with Ni element have beeninvestigated by Hammad [72] It is found that adding 005Nican refine the microstructure of Sn05Ag07Cu solder andcan reduce the sizes of Sn-rich phase Meanwhile the Ag

3Sn

and (Cu Ni)6Sn5intermetallic compounds were uniformly

distributed in the Sn matrix However the addition of 01Niinto Sn05Ag07Cu solder cause the formation of relativelyhigh fraction of the primary 120573-Sn and the intermetalliccompounds appeared abrasive within the matrix El-Dalyet al [73] added Ni element to the Sn30Ag05Cu solder


Figure 7 Sn-Nd phase [39]

alloy and observed a similar phenomenon Chen and Li[74] reported that the addition of Sb into SnAgCu soldercan obviously improve the microstructure and propertiesof lead-free solder It was indicated that some of the Sbpowders were fused in the 120573-Snmatrix (Sn-rich phase) someof them participate in the form of Ag

3(Sn Sb) and the

rest fused in the Cu6Sn5IMC layer With the addition of

Sb both thickness and grain size of IMC were decreasedFurthermore the results reveal that Sn35Ag07Cuwith about10 wt Sb solder system exhibited the smallest growth rateand gives the most prominent effect in retarding IMC growthand refining IMC grain size It is due to Sb element has higheraffinity to Sn and it will reduce the activity of Sn by formingSn-Sb compound leading to a reduced driving force for Cu-Sn IMC formation A heterogeneous nucleation effect forrestricting the IMC growth due to Sb addition is proposed

In general trace rare earth addition had little influenceon the melting temperature but can remarkably refine themicrostructures of SnAgCu lead-free solders Law et al [35]noted that by adding RE into Sn38Ag07Cu solder the grainsize of120573-Sn phaseswas refined and reduced to about 5ndash10120583mrespectively as compared with 10ndash20120583m of Sn38Ag07Cusolder It is mainly because RE is active elements whichcan accumulate the interface of intermetallic particles [75]Therefore the addition RE elements affect themicrostructureof SnAgCu solder Nevertheless the addition of an excessiveamount of RE elements would cause the appearance of a largenumber of the RE compounds whose the shape is similarto a ldquosnowflakerdquo [76] Shi et al [37] studied the influence ofrare earth Er on the microstructure and property of SnAgCusolder and found that addition of 025Er into Sn38Ag07Cureduces the size of Ag

3Sn and Cu

6Sn5intermetallic com-

pounds particles The addition of Pr and Nd has a significanteffect on the microstructure of SnAgCu solder The 120573-Sndendrites and the intermetallic compounds growth wererefined Meanwhile with the change of rare earth contentthemicrostructures of SnAgCu-xPr (Nd) solders changeThereason is attributed to Pr and Nd atoms tending to react withSn atoms to formRESn

3compound (Figure 7) and uniformly

dispersed fine RESn3particles can act as heterogeneous

nucleation sites for solidification Furthermore the Cu6Sn5

and Ag3Sn phase growth attaches to primary RESn

3phase

thus the microstructure of SnAgCu solder becomes finerHowever an excessive amount of RE added can form bulk

RESn3phase and deteriorate the mechanical properties of

SnAgCu solder joint [38 39] Zhang et al [40] added 005Ybto the Sn38Ag07Cu solder and observed that the sizesof Sn and eutectic microstructures were obviously reducedto become finer particles and the eutectic phase furtherspread to form network areas It is due to the absorptionof Yb with a high surface free energy on the grains duringsolidification during solidification However when addingYb to 01 the microstructure will become coarser than thatof Sn38Ag07Cu005Yb Moreover the Sn-Yb particles canbe observed based on scanning electron microscopy (SEM)testing Dudek and Chawla [17] investigated the microstruc-ture and mechanical behavior effects of adding La Ce and Yto the Sn39Ag07Cu solder It is found that the addition of LaCe and Y into SnAgCu solder can refine the microstructuresand reduced the thickness of the intermetallic compoundsof SnAgCu solder With a further increasing RE content theLaSn3 CeSn

3 and YSn

3intermetallic compounds formed

Gain and Chan [66] found that the incorporation of Aland Ni nanoparticles suppressed the formation of Cu

3Sn

IMC layer and refined IMC grains The possible reasoncould be attributed to very fine Sn-Ni-Cu IMC and Sn-Ag-AlIMC particles respectively in the SnAgCu-05Ni solder andSnAgCu-05Al solder joints Moreover they were uniformlydistributed in the 120573-Sn matrix Zhang et al [77] also havereported that the addition of Al nanoparticles into SnAgCucomposite solder can decrease the average size of IMCs andthe spacing between them obviously The addition of smallpercentage of Fe microparticle into Sn30Ag05Cu solderalloy had a change on the microstructure of solder jointClearly the microstructure was refined and the FeSn

2phase

was appeared With the addition of Al2O3nanoparticles

can influence the microstructure of SnAgCu solder ballFigure 8 shows that the volume fraction of the eutecticcolony was broader and Ag

3Sn was refined [58] It is due

to the adsorption effect and high surface free energy ofthe Al

2O3nanoparticles on the grain surface during solid-

ification process [20] Tang et al [59] reported that theaddition of trace amount TiO

2nanoparticles can influence

the microstructure of Sn30Ag05Cu solder and the size andspacing of Ag

3Sn decrease significantly When the content of

TiO2nanoparticles was 01 wt the Ag

3Sn grains size and

spacing were decreased by 5776 and 5231 With a furtherincrease of TiO

2addition the microstructure was similar

to TiO2-free noncomposite solder matrix It was attributed

to the agglomeration and segregation of TiO2nanoparticles

in the solders because the van der Waals forces causedTiO2nanoparticles to become entangled with each other as

they approached about 01 wt therefore the Ag3Sn grains

size will not decrease more Liu et al [19] developed theSn38Ag07Cu solder bearing SiC nanoparticles It can beseen that the growth and size of the IMCs in the compositesolder matrix decrease significantly However when thecontent of SiC nanoparticles was 02 wt the IMCs sizedid not decrease For the addition of SrTiO

3nanoparticles

into Sn30Ag05Cu solder very fine needle-shaped Ag3Sn

spherical-shape Cu6Sn5and AuSn

4IMCs were found in the

solder matrix The reason might be explained by the secondphase reinforcement SrTiO

3nanoparticles and promoted


(a) (b)

(c)

Figure 8 (a) SAC (b) SAC-05Al2

O3

and (c) SAC-10Al2

O3

[58]

a high nucleation rate in the eutectic during solidification[78] Fawzy et al [23] investigated the effect of ZnO nanopar-ticles on the microstructure of Sn35Ag05Cu solder Afteradding ZnO nanoparticles the volume fraction of Ag

3Sn and

Cu6Sn5IMCswas suppressedmeanwhile the120573-Sn grain size

was reduced by 22 The effects of addition ZrO2nanopar-

ticles on the microstructure of SnAgCu solder on AuNimetallized Cu pads were investigated by Gain et al [79] ASn-Ni-Cu IMC layer was found in both SnAgCu plain solderand SnAgCu-ZrO

2solder and with the number of reflow

cycles the IMC layer thickness was increased As the contentof ZrO

2nanoparticles increased AuSn

4 Ag3Sn and Cu

6Sn5

IMC particles and ZrO2nanoparticles were homogeneously

distributed in the solder matrix Therefore adding a smallamount of ZrO

2nanoparticles refined the microstructure

of the composite solder Adding POSS molecules to theSn30Ag05Cu composite solder can decrease the grains sizesand space lengths of Ag

3Sn IMCs As the POSS content

increases further themicrostructure of SnAgCu solder has nosignificant change [68] The graphene nanosheets (GNSs) asthe additive into SnAgCu solder can restrict the grain growthand lead to finer IMC grains With the addition of 003007 and 010GNS the average size of the IMCs wasreduced to 135 120583m 124 120583m and 121 120583m as compared with196 120583m for the Sn3Ag05Cu solder [49] For SAC-SWCNTcomposite solders with increasing SWCNT additive theaverage sizemorphology of the secondary phase was sharplyreduced [63] Due to CNT being a ceramic material the sur-face diffusion of the Ag

3Sn can be suppressed by the exceed-

ingly quicker translations of ceramic materials through thetemperatures that are produced while the sintering reactiontakes place [80] Han et al [51] and Yang et al [62] alsohave reported the influence of Ni-coated carbon addition on

the microstructure of Sn35Ag07Cu nanocomposite solderIt is found that the morphology of Ag

3Sn and Cu

6Sn5was

uniformly distributed in the solder matrixIn short the addition of the fourth elements can sig-

nificantly change the microstructure of SnAgCu soldersHowever their principles are different Some researchersby adding alloy elements produced the intermetallic com-pounds which alloying elements react with Sn thus refiningthe microstructure of SnAgCu solder Other researcherschoose to add some low solubility and diffusivity in Sn suchas Al2O3 TiO2 SiC and POSS Meanwhile we also found

that the addition of elements has a critical value When morethan a critical value will cause harm to the properties ofsolder joint

7 Interfacial Reactions

Interfacial reaction is soldersubstrate systems which are ofparticular importance to themanufacturability and reliabilityof electronic packaging [81] During soldering the solderalloys react with the substrate to form intermetallic com-pounds (IMCs) at the interface [82] such as Cu

6Sn5 Cu3Sn

and other IMCs Figure 9 shows the IMC layers formedbetween the solder and substrate after soldering [83] It iswell known that a thin IMC layer is desirable to achieve agoodmetallurgical bound at the interface However excessiveIMC growth may have a detrimental effect due to the brittlenature of IMC [84]Therefore knowledge of themorphologygrowth behavior and properties of IMC is crucial for under-standing of the reliability of the solder interconnection

The formation of IMC is divided into two stages one stagewhich is Cu

6Sn5forms first at the interface during soldering

and the other which is Cu3Sn will form between Cu

6Sn5


Figure 9 The microstructure of IMC layer at the interface betweensolder and copper [83]

Figure 10The sample was aged at 150∘C for 100 h Cu6

Sn5

had scal-lop-like shape and Cu

3

Sn is more of layer type [85]

and Cu by solid-stage reaction and the Kirkendall voids wereobserved in the Cu

3Sn layer (Figure 10) which is attributed to

the faster diffusion of Cu atoms compared to that of Sn atomsthrough the interface [85]

From the brief review we will find how to suppress thegrowth of IMC Some researchers study only the liquid-stageand some study the solid-stage while others study both

Below we shall review that the addition of the fourthalloys into SnAgCu lead-free solders influences the interfacialmicrostructure

The effect of solid state reactions betweenSn30Ag04Cu70In composite solder and Cu substratewas studied by Lejuste et al [86] The experimental resultsshowed that two IMCs layers Cu

6(Sn In)

5and Cu

3(Sn In)

were formed at the interface Meanwhile they found thatthe growth coefficients of Cu

6(Sn In)

5layer were similar to

those of plain SnAgCu solders while the growth coefficientsof Cu

3(Sn In) layer were found to be clearly lower than

those for the SnAgCu solders Therefore it is indicatedthat the addition of In element can suppress the growth ofIMC layer during thermal aging The 08 Zn addition intoSn38Ag07Cu solder can retard the growth of Cu-Sn IMC inliquidsolid state reaction and analyzes the reasons resultingin this situation It is mainly caused by an accumulation of Znatoms at the interface [27] Wang et al [87] also found thatthe growth of IMC was significantly reduced by the 02 Znaddition into SnAgCu solder The addition of 1 wt Bi intoSn28Ag05Cu solder was studied by Rizvi et al [28] showingthat 1 wt Bi addition could restrict the excessive formationof IMC during the soldering reaction and thereafter in aging

condition After a few days of aging the morphology ofthe IMC layer between the SnAgCu-Bi solder and the Cusubstrate transformed from the scallop type to the planartype and the intermetallic growth rate of SnAgCu-Bi wascalculated as 191 times 1017m2s compared with 221 times 1017m2sfor the SnAgCu solder Adding a small amount of Ni alloyingto the Sn30Ag05Cu (SAC) solder can also reduce the IMClayer thickness Comparing the SAC-Ni with the SAC itwas found that the IMC thickness of SAC-Ni compositesolder exhibits a slight change after aging whereas the IMCthickness of SAC was markedly increased by approximately60 compared to that at the as-reflowed state [15] Chenand Li [74] proposed that adding Sb can also restrain theIMC growth because of the formation of Sn-Sb compoundMa et al [88] reported that Co reinforced Sn30Ag05Cucomposite solder suppressed the growth of IMC layer Itis attributed to Co particles which can attract Sn and Cuto form Co-Sn or Co-Cu IMCs during the reflow processAfterwards Co close to the interfacial layer can hinder Cufrom being available for formation of the IMC layer andthereby reduce its growth rate Luo et al [30] demonstratedthat a minor Ga addition has the ability to inhibit the growthof interfacial intermetallic compounds (IMC) It is foundthat with the addition of 05 Ga the thickness of IMClayer is 589 thinner than that of the plain soldersubstrateIMC layer It is explained that Ga can reduce the activity ofSn thus depressing the growth of Cu

6Sn5and the excessive

reaction of the interfaceThe addition of trace amount of RE elements (mainly Ce

and La) into SnAgCu solder was investigated by Law et al[35] The research achievement shows that a layer of Cu

3Sn

was observed between the Cu6Sn5IMC layer and Cu pad

At the same time there are many Kirkendall voids betweenCu3Sn IMC layer and the copper substrate However with the

addition of RE the growth of IMLwas significantly inhibitedRare earth Y element can show an effective influence on theinterfacial growth of IML in SnAgCu solder With the addi-tion of Y the thickness of IMLwas reduced and the growth ofthe IML was suppressed during the high-temperature aging[36] Gao et al [39] note that the addition of Nd can changethe growth of intermetallic layer When the addition of Ndwas 005 the thickness of IML reduced by 458 comparedwith the plain solder jointThe reasonmay be attributed to theformation of Sn-Nd compound thus retarding the growth ofthe Cu

6Sn5IMC during the soldering The advantage of rare

earth Yb addition into SnAgCu solder was shown by Zhanget al [40] who found that 005 Yb addition into SnAgCualloy suppressed the growth of IMC and the morphology ofCu6Sn5layer can be changed to a relatively flat morphology

Small amounts of La were added to the SnAgCu lead-freesolder for studying the growth of the IMC layer between thesolder and the Cu substrate Comparing the SnAgCu solderthe IMC thickness has reduced by approximately 60 withadding trace amount of rare earth La [89] Liu et al [90]investigated the effects of addition of Ce on the formation andgrowth of interfacial IMCs between the SnAgCu solder jointand Cu substrate It is found that the thickness of interfacialIMC can be reduced during the soldering and aging with theaddition of Ce into SnAgCu solder


(a) (b)

(c) (d)

Figure 11 SEMmicrographs of ((a) and (b)) SnAgCu and ((c) and (d)) SnAgCu-1TiO2

solder joints on Ag metallized Cu pads after ((a) and(c)) 8 and ((b) and (d)) 16 reflow cycles [21]

Adding trace amounts of Fe microparticles can restrainthe growth of intermetallic compounds (IMCs) During liq-uid state reaction Fe can effectively suppress the growthof Cu

6Sn5and Cu

3Sn layer However during the reflow

process Fe trended to retard the growth of the Cu3Sn layer

Moreover the total thickness of IMCs for the SnAgCu-Fecomposite solder was similar to that for the plain SnAgCusolder [91] Xiang et al [18] reported the positive effect ofMn nanoparticles on the SnAgCu solder for restricting thegrowth of intermetallic compounds after first and six timesof reflow However for Cu

3Sn thickness the addition of Mo

nanoparticleswas not affecting itThe addition ofAl nanopar-ticles can alter the growth of interfacial IMCbetween SnAgCusolder alloys and Cu substrate with 1 cycle and 16 cycles ofreflow [57]When the content of Al nanoparticles was 3wtthe thickness of the IMC decreased from 28 120583m to 24 120583mwith one flow cycle After 16 reflows the thickness of the IMCdecreased from 67 120583m to 61 120583m Ni nanoparticles can alsoinfluence the thickness of IMC layer With the addition ofNi nanoparticles the morphology of Cu

6Sn5changes from a

scalloped structure to a planar type after reflow In additionthe growth of (Cu Ni)

6Sn5enhanced and that of Cu

3Sn was

suppressed [44] Haseeb et al [46 92] investigated the effectof Mo and Co nanoparticles additions on the morphologyof interfacial IMCs between Sn38Ag07Cu solder and Cusubstrate It is found that the addition of Mo nanoparticlescan decrease the thickness and diameter of Cu

6Sn5 However

the addition of Co nanoparticles can enhance the growthof Cu

6Sn5and suppress the growth of Cu

3Sn Due to the

fact that Co nanoparticles dissolved in Cu6Sn5 then change

the intermetallic compounds composition Nevertheless Monanoparticles remain intact without any chemical changeor recognizable physical and segregate preferentially at theinterfaces Therefore they hinder the path for diffusion andrestrict the intermetallic compound growth Chan et al[93] developed a novel composite solder by incorporatingZn nanoparticles into Sn38Ag07Cu solder and these Znnanoparticles were found to havemuch decreased theCu

6Sn5

IMC thickness When the addition of Zn nanoparticles was03 no Cu

5Zn8can be observed while with the addition

of 08 Zn nanoparticles Cu5Zn8can be observed and

exhibited 153 120583m thickness After one reflow Cu3Sn was not

noticeable After 6 reflows the Cu6Sn5thickness was reduced

with the addition of Zn When the addition was 08 Znthe thickness of Cu

6Sn5reduced from 411 120583m to 097 120583m

Meanwhile the Cu5Zn8IMC thickness was increased to

172 120583m and the Cu3Sn was found to have a thickness of

056 120583m Tsao and coworkers [58] showed that small amountsof Al2O3nanoparticles into SnAgCu solder suppressed the

growth of the IMC thickness during the reflow cycles Gainet al [21] found that the addition of TiO

2into SnAgCu solder

reduced the IMC thickness after thermal cycling as shownin Figure 11 When ZrO

2nanoparticles were added to the

SnAgCu solders it is found that the intermetallic compounds(IMCs) can be depressed [24] Fouzder et al [78] studiedSn30Ag05Cu composite solder with 90ndash110 nm SrTiO

3rein-

forcement particles and reported significant reduction theIMC layer thickness With the content of 005wt SrTiO

3


Figure 12 SME image of Sn whisker shorting two legs [97]

the IMC thickness was decreased from 67 120583m to 58 120583m aftersixteen reflow cycles Nai et al [94] added carbon nanotubes(CNTs) to the Sn35Ag07Cu solder alloy Results revealedthat with the addition of CNTs the nanocomposite solderexhibited a lower diffusion coefficient thus the growth ofIMC layer was retarded Han et al [95] also reported a similareffect of Ni-CNTs on the interfacial IMC

8 SN Whiskers

In past reports the addition of rare earth (RE) elementshas showed many beneficial effects However with furtherresearch Pb-free solder containing rare earth encounteredunexpected problems namely Sn whisker For electronicdevice tin whiskers formation is fatal and easily causes shortcircuits as well as system failures because whiskers can growto a length exceeding several hundred microns and thesetin whiskers are nearly pure single crystals with excellentelectrical conductivity [96] Figure 12 [97] shows a scanningelectron image of whiskers on the legs of a lead frame wherea very long whisker can be observed to have bridged a pair ofthe legs

In recent years rare earths were wildly used in the Pb-free solders to enhance solderability However as a surface-active element the reactive nature of rare earth elementswith oxygen and accelerate tin whisker growth in a rareearth element-containing solder alloy [98] Hao et al [99]found that 10 Er doping could form whiskers and themorphology of the Sn whiskers changes from rod-like tothread-like with the storage temperature increases from 25∘Cto 150∘C Dudek and Chawla [100] also investigated the effectof 2 wt Ce La or Y additions on the whiskering behaviorof Sn39Ag07Cu It is found that oxidation of RESn

3causes

compressive stresses that ultimately result in the formation ofSn whiskers Moreover the size of the RESn

3has a significant

impact on oxidation and whiskering

2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)

CeSn3+O2997888rarr CeO

2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)

According to the existing literature we find that previousresearch added too much rare earth elements into SnAgCu

20120583m

Figure 13 SnAgCu-Ce surface whisker [101]

solder and the minimum addition amount of the rare earthwas 1 thus providing large RESn

3phase for whiskers

growth In order to prevent rapid whisker growth Chuangand Lin [101] showed that 05 Zn addition into SnAgCusolder refined the microstructure and suppressed whiskergrowth Figure 13 shows SnAgCu-Ce surface whisker

Although the addition of alloying elements can suppressthe rapid growth of tin whiskers in RE-containing soldersit does not inhibit the emergence of tin whiskers We thinkwhiskers formation is mainly due to an excess of rare earthelementsTherefore researchers should control the content ofrare earth It is attributed to addition of trace amounts of rareearth elements RE phase formation is limited thereby havingdifficulty in providing the driving force for whisker growth

9 Conclusions

With the addition of alloying elements and nanoparticles thewettabilitymechanical properties and hardness properties ofSnAgCu solder and solder joints were enhanced obviouslyHowever excessive elements can decrease these propertiesfor example when adding excessive amounts of rare earthelements the tin whiskers will appear And with the additionof excessive amounts of nanoparticles metal nanoparticleseasily react with matrix thus the phenomenon of graingrowth occurs and affects the reliability of solder intercon-nections For inert nanoparticles for example Al

2O3 ZrO2

SiC and so on they are prone to agglomeration and causethe effect of dispersion strengthening to be lost Thereforeselecting the appropriate additive amount is very importantIn addition the alloying elements and nanoparticles canrefine the microstructure of SnAgCu solders and the retard-ing effect of elements on the intermetallic compounds in thesoldercopper is also demonstrated

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (no 51475220) the Natural Science


Foundation of Jiangsu Province (BK2012144) and theNaturalScience Foundation of the Higher Education Institutions ofJiangsu Province (12KJB460005)

References

[1] S Xu A H Habib A D Pickel andM E McHenry ldquoMagneticnanoparticle-based solder composites for electronic packagingapplicationsrdquo Progress in Materials Science vol 67 pp 95ndash1602015

[2] J Keller D Baither U Wilke and G Schmitz ldquoMechanicalproperties of Pb-free SnAg solder jointsrdquo Acta Materialia vol59 no 7 pp 2731ndash2741 2011

[3] A A El-Daly and A M El-Taher ldquoEvolution of thermalproperty and creep resistance of Ni and Zn-doped Sn-20Ag-05Cu lead-free soldersrdquo Materials amp Design vol 51 pp 789ndash796 2013

[4] A A El-Daly and A E Hammad ldquoEnhancement of creepresistance and thermal behavior of eutectic Sn-Cu lead-freesolder alloy by Ag and In-additionsrdquoMaterials and Design vol40 pp 292ndash298 2012

[5] M R Shalaby ldquoEffect of silicon addition on mechanical andelectrical properties of Sn-Zn based alloys rapidly quenchedfrom meltrdquo Materials Science and Engineering A vol 550 pp112ndash117 2012

[6] K Kanlayasiri M Mongkolwongrojn and T Ariga ldquoInfluenceof indium addition on characteristics of Sn-03Ag-07Cu solderalloyrdquo Journal of Alloys and Compounds vol 485 no 1-2 pp225ndash230 2009

[7] C L Chuang L C Tsao H K Lin and L P Feng ldquoEffects ofsmall amount of active Ti element additions on microstructureand property of Sn35Ag05Cu solderrdquo Materials Science andEngineering A vol 558 pp 478ndash484 2012

[8] LW Lin JM Song Y S Lai Y T Chiu N C Lee and J Y UanldquoAlloying modification of Sn-Ag-Cu solders by manganese andtitaniumrdquoMicroelectronics Reliability vol 49 no 3 pp 235ndash2412009

[9] H Fallahi M S Nurulakmal A F Arezodar and J AbdullahldquoEffect of iron and indium on IMC formation and mechanicalproperties of lead-free solderrdquo Materials Science and Engineer-ing A vol 553 pp 22ndash31 2012

[10] A A El-Daly A E Hammad G S Al-Ganainy and MRagab ldquoInfluence of Zn addition on the microstructure meltproperties and creep behavior of low Ag-content Sn-Ag-Culead-free soldersrdquoMaterials Science and Engineering A vol 608pp 130ndash138 2014

[11] D A Shnawah M F M Sabri and I A Badruddin ldquoAreview on thermal cycling and drop impact reliability of SACsolder joint in portable electronic productsrdquo MicroelectronicsReliability vol 52 no 1 pp 90ndash99 2012

[12] M L Huang and L Wang ldquoEffects of Cu Bi and In onmicrostructure and tensile properties of Sn-Ag-X(Cu Bi In)soldersrdquoMetallurgical andMaterials Transactions A vol 36 pp1439ndash1446 2005

[13] E A Hammad ldquoEvolution of microstructure thermal andcreep properties of Ni-doped Snndash05Agndash07Cu low-Ag solderalloys for electronic applicationsrdquo Materials amp Design vol 52pp 663ndash670 2013

[14] A A El-Daly and A E Hammad ldquoElastic properties andthermal behavior of Sn-Zn based lead-free solder alloysrdquo Jour-nal of Alloys and Compounds vol 505 no 2 pp 793ndash800 2010

[15] W X Dong Y W Shi Y P Lei Z D Xia and F Guo ldquoEffectsof trace amounts of rare earth additions on microstructureand properties of Sn-Bi-based solder alloyrdquo Journal of MaterialsScience Materials in Electronics vol 20 no 10 pp 1008ndash10172009

[16] CM LWu and YWWong Lead-Free Electronic Solders 2007[17] M A Dudek and N Chawla ldquoEffect of rare-earth (La Ce and

Y) additions on the microstructure and mechanical behaviorof Sn-39Ag-07Cu solder alloyrdquo Metallurgical and MaterialsTransactions A vol 41 pp 610ndash620 2010

[18] K K Xiang A S M A Haseeb M M Arafat and Y X GohldquoEffects of Mn nanoparticles on wettability and intermetalliccompounds in between Sn-38Ag-07Cu and Cu substrate dur-ing multiple reflowrdquo in Proceedings of the 4th Asia Symposiumon Quality Electronic Design pp 297ndash301 July 2012

[19] P Liu P Yao and J Liu ldquoEffect of SiC nanoparticle additions onmicrostructure and microhardness of Sn-Ag-Cu solder alloyrdquoJournal of Electronic Materials vol 37 no 6 pp 874ndash879 2008

[20] L C Tsao S Y Chang C I Lee W H Sun and C HHuang ldquoEffects of nano-Al

2

O3

additions on microstructuredevelopment and hardness of Sn35Ag05Cu solderrdquo Materialsand Design vol 31 no 10 pp 4831ndash4835 2010

[21] A K Gain Y C Chan and W K C Yung ldquoMicrostructurethermal analysis and hardness of a Sn-Ag-Cu-1 wt nano-TiO2

composite solder on flexible ball grid array substratesrdquoMicroelectronics Reliability vol 51 no 5 pp 975ndash984 2011

[22] S Y Chang C C Jain T H Chuang L P Feng and L C TsaoldquoEffect of addition of TiO

2

nanoparticles on themicrostructuremicrohardness and interfacial reactions of Sn35AgXCu solderrdquoMaterials amp Design vol 32 no 10 pp 4720ndash4727 2011

[23] A Fawzy S A Fayek M Sobhy E Nassr M M Mousaand G Saad ldquoTensile creep characteristics of Snminus35Agminus05Cu(SAC355) solder reinforced with nano-metric ZnO particlesrdquoMaterials Science and Engineering A vol 603 pp 1ndash10 2014

[24] A K Gain andY C Chan ldquoGrowthmechanism of intermetalliccompounds and damping properties of Sn-Ag-Cu-1 wt nano-ZrO2

composite soldersrdquoMicroelectronics Reliability vol 54 no5 pp 945ndash955 2014

[25] S K Ghosh A SM A Haseeb and A Afifi ldquoEffects of metallicnanoparticle doped flux on interfacial intermetallic compoundsbetween Sn-30Ag-05Cu and copper substraterdquo in Proceedingsof the IEEE 15th Electronics Packaging Technology Conference(EPTC rsquo13) pp 21ndash26 Singapore December 2013

[26] Z Moser P Sebo W Gąsior P Svec and J Pstrus ldquoEffect ofindium on wettability of SnndashAgndashCu solders Experiment vsmodeling Part Irdquo Calphad vol 33 no 1 pp 63ndash68 2009

[27] L Zhang J G Han C W He and Y H Guo ldquoEffect of Znon properties and microstructure of SnAgCu alloyrdquo Journal ofMaterials Science Materials in Electronics vol 23 pp 1950ndash1956 2012

[28] M J Rizvi Y C Chan C Bailey H Lu andM N Islam ldquoEffectof adding 1 wt Bi into the Sn-28Ag-05Cu solder alloy onthe intermetallic formationswithCu-substrate during solderingand isothermal agingrdquo Journal of Alloys and Compounds vol407 pp 208ndash214 2006

[29] Z Moser W Gasior K Bukat et al ldquoPb-free solders part 1wettability testing of Sn-Ag-Cu alloys with Bi additionsrdquo Journalof Phase Equilibria and Diffusion vol 27 no 2 pp 133ndash1392006

[30] D X Luo S B Xue and Z Q Li ldquoEffects of Ga additionon microstructure and properties of Sn-05Ag-07Cu solderrdquo


Journal of Materials Science Materials in Electronics vol 25 no8 pp 3566ndash3571 2014

[31] N S Liu and K L Lin ldquoThe effect of Ga content on thewetting reaction and interfacial morphology formed betweenSnminus855Znminus05Agminus01AlminusxGa solders and Curdquo Scripta Materi-alia vol 54 no 2 pp 219ndash224 2006

[32] S Lu F Luo J Chen and B H Wang in Proceedings of theInternational Conference on Electronic Packaging Technology ampHigh Density Packaging 2008

[33] C M L Wu D Q Yu C M T Law and L Wang ldquoPropertiesof lead-free solder alloys with rare earth element additionsrdquoMaterials Science and Engineering R Reports vol 44 no 1 pp1ndash44 2004

[34] D Q Yu J Zhao and L Wang ldquoImprovement on themicrostructure stability mechanical and wetting propertiesof Sn-Ag-Cu lead-free solder with the addition of rare earthelementsrdquo Journal of Alloys and Compounds vol 376 pp 170ndash175 2004

[35] C M T Law C M L Wu D Q Yu L Wang and J K LLai ldquoMicrostructure solderability and growth of intermetalliccompounds of Sn-Ag-Cu-RE lead-free solder alloysrdquo Journal ofElectronic Materials vol 35 no 1 pp 89ndash93 2006

[36] H Hao J Tian Y W Shi Y P Lei and Z D Xia ldquoPropertiesof Sn38Ag07Cu solder alloy with trace rare earth element yadditionsrdquo Journal of ElectronicMaterials vol 36 no 7 pp 766ndash774 2007

[37] Y Shi J Tian H Hao Z Xia Y Lei and F Guo ldquoEffects ofsmall amount addition of rare earth Er on microstructure andproperty of SnAgCu solderrdquo Journal of Alloys and Compoundsvol 453 no 1-2 pp 180ndash184 2008

[38] L L Gao S B Xue L Zhang et al ldquoEffect of praseodymiumon the microstructure and properties of Sn38Ag07Cu solderrdquoJournal of Materials Science Materials in Electronics vol 21 no9 pp 910ndash916 2010

[39] L L Gao S B Xue L Zhang Z Sheng G Zeng and F JildquoEffects of trace rare earth Nd addition on micro structureand properties of SnAgCu solderrdquo Journal of Materials ScienceMaterials in Electronics vol 21 no 7 pp 643ndash648 2010

[40] L Zhang X Y Fan Y H Guo and C W He ldquoPropertiesenhancement of SnAgCu solders containing rare earth YbrdquoMaterials amp Design vol 57 pp 646ndash651 2014

[41] J X Wang S B Xue Z J Han et al ldquoEffects of rare earthCe on microstructures solderability of Sn-Ag-Cu and Sn-Cu-Ni solders as well as mechanical properties of soldered jointsrdquoJournal of Alloys and Compounds vol 467 pp 219ndash226 2009

[42] X Y Zhao M Q Zhao X Q Cui and M X Tong ldquoEffect ofcerium onmicrostructure andmechanical properties of Sn-Ag-Cu system lead-free solder alloysrdquo Transactions of NonferrousMetals Society of China vol 17 no 4 pp 805ndash810 2007

[43] Z G Chen Y W Shi Z D Xia and Y F Yan ldquoProperties oflead-free solder SnAgCu containing minute amounts of rareearthrdquo Journal of ElectronicMaterials vol 32 no 4 pp 235ndash2432003

[44] S L Tay A S M A Haseeb M R Johan P R Munroe andM Z Quadir ldquoInfluence of Ni nanoparticle on the morphologyand growth of interfacial intermetallic compounds betweenSn-38Ag-07Cu lead-free solder and copper substraterdquo Inter-metallics vol 33 pp 8ndash15 2013

[45] J-W Yoon S-W Kim and S-B Jung ldquoIMC morphologyinterfacial reaction and joint reliability of Pb-free Sn-Ag-Cusolder on electrolytic Ni BGA substraterdquo Journal of Alloys andCompounds vol 392 no 1-2 pp 247ndash252 2005

[46] A S M A Haseeb and T S Leng ldquoEffects of Co nanoparticleaddition to Sn-38Ag-07Cu solder on interfacial structure afterreflowand ageingrdquo Intermetallics vol 19 no 5 pp 707ndash712 2011

[47] S L Tay A S M A Haseeb and M R Johan ldquoAddition ofcobalt nanoparticles into Sn-38Ag-07Cu lead-free solder bypaste mixingrdquo Soldering and Surface Mount Technology vol 23no 1 pp 10ndash14 2011

[48] Y Li C X Zhao Y Liu and Y Wang ldquoEffect of TiO2

addition concentration on the wettability and intermetalliccompounds growth of Sn30Ag05CundashxTiO

2

nano-compositesoldersrdquo Journal of Materials Science Materials in Electronicsvol 25 no 9 pp 3816ndash3827 2014

[49] X D Liu Y D Han H Y Jing J Wei and L Y Xu ldquoEffect ofgraphene nanosheets reinforcement on the performance of Sn-Ag-Cu lead-free solderrdquo Materials Science and Engineering Avol 562 pp 25ndash32 2013

[50] S M L Nai J Wei and M Gupta ldquoLead-free solder reinforcedwithmultiwalled carbon nanotubesrdquo Journal of ElectronicMate-rials vol 35 no 7 pp 1518ndash1522 2006

[51] Y D Han SM L Nai H Y Jing L Y Xu CM Tan and JWeildquoDevelopment of a Sn-Ag-Cu solder reinforced with Ni-coatedcarbon nanotubesrdquo Journal of Materials Science Materials inElectronics vol 22 no 3 pp 315ndash322 2011

[52] V Kripesh M Teo C T Tai G Vishwanadam and Y C MuildquoDevelopment of a lead free chip scale package for wirelessapplicationsrdquo in Proceedings of the 51st Electronic Componentsand Technology Conference pp 665ndash670 June 2001

[53] H Y Song Q S Zhu Z G Wang J K Shang and M LuldquoEffects of Zn addition onmicrostructure and tensile propertiesof Sn-1Ag-05Cu alloyrdquoMaterials Science and EngineeringA vol527 no 6 pp 1343ndash1350 2010

[54] A A El-Daly and A M El-Taher ldquoImproved strength of Niand Zn-doped Sn-20Ag-05Cu lead-free solder alloys undercontrolled processing parametersrdquo Materials amp Design vol 47pp 607ndash614 2013

[55] G Y Li B L Chen X Q Shi S C K Wong and Z F WangldquoEffects of Sb addition on tensile strength of Sn-35Ag-07Cusolder alloy and jointrdquo Thin Solid Films vol 504 no 1-2 pp421ndash425 2006

[56] Y F Yan J H Zhu F X Chen J G He and D X Yang ldquoCreepbehavior on Ag particle reinforced SnCu based compositesolder jointsrdquo Transactions of Nonferrous Metals Society vol 16pp 1116ndash1200 2006

[57] A K Gain T Fouzder Y C Chan A Sharif N B Wong andW K C Yung ldquoThe influence of addition of Al nano-particleson the microstructure and shear strength of eutectic Sn-Ag-Cu solder on AuNi metallized Cu padsrdquo Journal of Alloys andCompounds vol 506 no 1 pp 216ndash223 2010

[58] L C Tsao R W Wu T H Cheng K H Fan and R SChen ldquoEffects of nano-Al

2

O3

particles on microstructure andmechanical properties of Sn35Ag05Cu composite solder ballgrid array joints on SnCu padsrdquo Materials amp Design vol 50pp 774ndash781 2013

[59] Y Tang G Y Li and Y C Pan ldquoEffects of TiO2

nanoparticlesaddition on microstructure microhardness and tensile proper-ties of Snminus30Agminus05CminusxTiO

2

composite solderrdquo Materials ampDesign vol 55 pp 574ndash582 2014

[60] A Roshanghias A H Kokabi YMiyashita YMutohM Reza-yat and H R Madaah-Hosseini ldquoCeria reinforced nanocom-posite solder foils fabricated by accumulative roll bondingprocessrdquo Journal of Materials Science Materials in Electronicsvol 23 no 9 pp 1698ndash1704 2012


[61] S M L Nai J Wei and M Gupta ldquoInfluence of ceramicreinforcements on the wettability and mechanical properties ofnovel lead-free solder compositesrdquo Thin Solid Films vol 504no 1-2 pp 401ndash404 2006

[62] Z B Yang W Zhou and P Wu ldquoEffects of Ni-coated carbonnanotubes addition on the microstructure and mechanicalproperties of Sn-Ag-Cu solder alloysrdquo Materials Science andEngineering A vol 590 pp 295ndash300 2014

[63] K M Kumar V Kripesh and A A O Tay ldquoSingle-wallcarbon nanotube (SWCNT) functionalized Sn-Ag-Cu lead-freecomposite soldersrdquo Journal of Alloys and Compounds vol 450no 1-2 pp 229ndash237 2008

[64] XHu Y C Chan K Zhang andKC Yung ldquoEffect of graphenedoping on microstructural and mechanical properties of Sn-8Zn-3Bi solder joints together with electromigration analysisrdquoJournal of Alloys and Compounds vol 580 pp 162ndash171 2013

[65] Y C Zhou Q L Pan Y B He et al ldquoMicrostructures andproperties of Sn-Ag-Cu lead-free solder alloys containing LardquoTransactions of Nonferrous Metals Society of China vol 17supplement 1 pp s1043ndashs1048 2007

[66] A K Gain and Y C Chan ldquoThe influence of a small amountof Al and Ni nano-particles on the microstructure kinetics andhardness of Sn-Ag-Cu solder on OSP-Cu padsrdquo Intermetallicsvol 29 pp 48ndash55 2012

[67] K Mohankumar and A A O Tay in Proceedings of 6th Elec-tronics Packaging Technology Conference 2004

[68] J Shen C F Peng H G Yin and J Chen ldquoInfluence of minorPOSS molecules additions on the microstructure and hardnessof Sn3Ag05Cu-xPOSS composite soldersrdquo Journal of MaterialsScience Materials in Electronics vol 23 pp 1640ndash1646 2012

[69] L Zhang and K N Tu ldquoStructure and properties of lead-freesolders bearingmicro and nano particlesrdquoMaterials Science andEngineering R Reports vol 82 pp 1ndash32 2014

[70] D A Shnawah M F M Sabri I A Badruddin S B MSaid T Ariga and F X Che ldquoEffect of ag content and theminor alloying element fe on the mechanical properties andmicrostructural stability of Sn-Ag-Cu solder alloy under high-temperature annealingrdquo Journal of Electronic Materials vol 42no 3 pp 470ndash484 2013

[71] M F M Sabri D A Shnawah I A Badruddin S B M SaidF X Che and T Ariga ldquoMicrostructural stability of Snndash1Agndash05CundashxAl (x = 1 15 and 2 wt) solder alloys and the effectsof high-temperature aging on their mechanical propertiesrdquoMaterials Characterization vol 78 pp 129ndash143 2013

[72] A E Hammad ldquoInvestigation of microstructure and mechani-cal properties of novel Sn-05Ag-07Cu solders containing smallamount of NirdquoMaterials amp Design vol 50 pp 108ndash116 2013

[73] A A El-Daly A M El-Taher and T R Dalloul ldquoEnhancedductility and mechanical strength of Ni-doped Sn-30Ag-05Culead-free soldersrdquo Materials and Design vol 55 pp 309ndash3182014

[74] B L Chen and G Y Li ldquoInfluence of Sb on IMC growth inSn-Ag-Cu-Sb Pb-free solder joints in reflow processrdquoThin SolidFilms vol 462-463 pp 395ndash401 2004

[75] Q Zhai J S K Guan and G Y Shang Alloy Thermo-Mech-anism Theory and Applications Metallurgy Industry PressBeijing China 1999

[76] Z G Chen Y W Shi Z D Xia and Y F Yan ldquoStudy on themicrostructure of a novel lead-free solder alloy SnAgCu-RE andits soldered jointsrdquo Journal of ElectronicMaterials vol 31 no 10pp 1122ndash1128 2002

[77] L Zhang X Y Fan Y H Guo and C W He ldquoMicrostructuresand fatigue life of SnAgCu solder joints bearing Nano-Alparticles in QFP devicesrdquo Electronic Materials Letters vol 10no 3 pp 645ndash647 2014

[78] T Fouzder I Shafiq Y C Chan A Sharif and W K C YungldquoInfluence of SrTiO

3

nano-particles on the microstructure andshear strength of Sn-Ag-Cu solder on AuNi metallized Cupadsrdquo Journal of Alloys andCompounds vol 509 no 5 pp 1885ndash1892 2011

[79] A K Gain Y C Chan and W K C Yung ldquoEffect ofadditions of ZrO

2

nano-particles on the microstructure andshear strength of Sn-Ag-Cu solder on AuNi metallized CupadsrdquoMicroelectronics Reliability vol 51 no 12 pp 2306ndash23132011

[80] K Upadhya in Proceedings of the Symposium Sponsored by theStructural Materials Division of TMS Annual Meeting 1993

[81] J X Liang T B Luo A M Hu and M Li ldquoFormation andgrowth of interfacial intermetallic layers of Sn-8Zn-3Bi-03Cron Cu Ni andNi-W substratesrdquoMicroelectronics Reliability vol54 no 1 pp 245ndash251 2014

[82] K N Tu and K Zeng ldquoTin-lead (SnPb) solder reaction in flipchip technologyrdquoMaterials Science and Engineering R Reportsvol 34 no 1 pp 1ndash58 2001

[83] G Zeng S Xue L Zhang L Gao W Dai and J Luo ldquoA reviewon the interfacial intermetallic compounds between Sn-Ag-Cu based solders and substratesrdquo Journal of Materials ScienceMaterials in Electronics vol 21 no 5 pp 421ndash440 2010

[84] T Laurila V Vuorinen and J K Kivilahti ldquoInterfacial reactionsbetween lead-free solders and common base materialsrdquoMateri-als Science and Engineering R Reports vol 49 no 1-2 pp 1ndash602005

[85] W Peng E Monlevade and M E Marques ldquoEffect of thermalaging on the interfacial structure of SnAgCu solder joints onCurdquo Microelectronics Reliability vol 47 no 12 pp 2161ndash21682007

[86] C Lejuste F Hodaj and L Petit ldquoSolid state interactionbetween a SnndashAgndashCundashIn solder alloy and Cu substraterdquo Inter-metallics vol 36 pp 102ndash108 2013

[87] F-J Wang F Gao X Ma and Y-Y Qian ldquoDepressing effectof 02wtZn addition into Sn-30Ag-05Cu solder alloy onthe intermetallic growth with Cu substrate during isothermalagingrdquo Journal of Electronic Materials vol 35 no 10 pp 1818ndash1824 2006

[88] L M Ma F Tai G C Xu F Guo and X T Wang ldquoEffectsof processing and amount of co addition on shear strengthand microstructual development in the Sn-30Ag-05Cu solderjointrdquo Journal of Electronic Materials vol 40 no 6 pp 1416ndash1421 2011

[89] M A Dudek R S Sidhu N Chawla and M RenavikarldquoMicrostructure and mechanical behavior of novel rare earth-containing Pb-free soldersrdquo Journal of Electronic Materials vol35 no 12 pp 2088ndash2097 2006

[90] X Liu L F Wang J Wang and Y Lv in Proceedings of the 11thInternational Conference on Electronic Packaging Technalogy ampHigh Density Packaging 2010

[91] X Y Liu M L Huang N Zhao and L Wang ldquoLiquid-state and solid-state interfacial reactions between Sn-Ag-Cu-Fe composite solders and Cu substraterdquo Journal of MaterialsScience Materials in Electronics vol 25 pp 328ndash337 2014

[92] A S M A Haseeb M M Arafat and M R Johan ldquoStabilityofmolybdenumnanoparticles in Sn-38Ag-07Cu solder during


multiple reflow and their influence on interfacial intermetalliccompoundsrdquo Materials Characterization vol 64 pp 27ndash352012

[93] Y H Chan M M Arafat and A S M A Haseeb ldquoEffects ofreflow on the interfacial characteristics between Zn nanopar-ticles containing Sn-38Ag-07Cu solder and copper substraterdquoSoldering and Surface Mount Technology vol 25 no 2 pp 91ndash98 2013

[94] S M L Nai J Wei and M Gupta ldquoInterfacial intermetallicgrowth and shear strength of lead-free composite solder jointsrdquoJournal of Alloys and Compounds vol 473 no 1-2 pp 100ndash1062009

[95] Y D Han H Y Jing SM L Nai L Y Xu CM Tan and JWeildquoInterfacial reaction and shear strength of Ni-coated carbonnanotubes reinforced Sn-Ag-Cu solder joints during thermalcyclingrdquo Intermetallics vol 31 pp 72ndash78 2012

[96] G T Galyon ldquoAnnotated tin whisker bibliography and anthol-ogyrdquo IEEE Transactions on Electronics Packaging Manufactur-ing vol 28 no 1 pp 94ndash122 2005

[97] K N Tu Solder Joint Technology Materials Properties andReliability Springer Series in Materials Science Springer 2007

[98] T-H Chuang ldquoRapidwhisker growth on the surface of Sn-3Ag-05Cu-10Ce solder jointsrdquo Scripta Materialia vol 55 no 11 pp983ndash986 2006

[99] H Hao Y W Shi Z D Xia Y P Lei and F Guo ldquoOxidization-induced tin whisker growth on the surface of Sn-38Ag-07Cu-10Er alloyrdquoMetallurgical and Materials Transactions A vol 40no 8 pp 2016ndash2021 2009

[100] M A Dudek and N Chawla ldquoMechanisms for Sn whiskergrowth in rare earth-containing Pb-free soldersrdquo Acta Materi-alia vol 57 no 15 pp 4588ndash4599 2009

[101] TH Chuang andH J Lin ldquoInhibition of whisker growth on thesurface of Sn-3Ag-05Cundash05Ce solder alloyedwith Znrdquo Journalof Electronic Materials vol 38 no 3 pp 420ndash424 2009

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


217∘C 34∘C higher than that of the eutectic SnPb Such highmelting temperature will increase the reflowing temperatureand lead to thermal damage of the polymer substrate [5]Meanwhile it also enhances the dissolution rate and solubilityof Cu in the molten solder thus improving the rate of for-mation of IMCs This is the reason that the IMCs layerof SnAgCu thicker than Sn-Pb Hence some researchersexpect to add the fourth elements to decrease the meltingtemperature of SnAgCu solders

Trace amount of indium (In) added to the SnAgCu lead-free solder can change the melting behavior obviously Itwas shown in the literature [6] that adding 30 wt of Inthe solidus and liquidus temperatures decreased 217 and115∘C respectively as compared with 2194 and 2417∘C forthe Sn03Ag07Cu solder But the In is very expensive theaddition of In can increase the cost of lead-free soldersChuang et al [7] proposed that the effect of Ti on themelting point of Sn35Ag05Cu (SAC) solder alloy With theaddition of Ti element the melting temperatures changeslightly The liquidus temperatures are 22095 22086 and21947∘C for the SAC-xTi solder alloys with Ti contents of025 05 and 10 wt respectively Moreover the meltingrange is decreased from 466 to 288∘C Generally speakingthe narrow melting range of the solder means excellentthermal properties It is mainly attributed to the narrowmelting range explaining that solders exist as part liquidfor a very short time during solidification and can formreliable joints during the reflow process Figure 1 representsthe differential scanning calorimetry (DSC) curve of SnAgCubearing different manganese (Mn) and titanium (Ti) It isindicated that Sn30Ag05Cu solder has only one endother-mic peak yet it has two peaks for the Sn10Ag05Cu (SAC)solder Meanwhile worthy of notice is that the degree ofundercooling for proeutectic Sn was significantly affected bythe addition of trace alloying elements (Mn and Ti) intoSAC solder alloyThe SAC-05Ti sample showed an extremelysuppressed undercooling of only 4∘C [8] The addition ofFe into SnAgCu solder did not change much of the meltingtemperature [9]The DSC results demonstrated a single peakof Sn36Ag09Cu solder However there are two obviousendothermic peaks (220∘C and 235∘C) that appear for theSnAgCu-02Fe solder alloyThis shows that melting occurredover a range of temperatures It may be ascribed to the peaksoverlapped the first peak may indicate that the solder waspartially fused The addition of Fe most likely resulted inshifting of the melting point from the eutectic point to nearthe eutectic point and the melting point of the solder isin the range of 22287 to 230∘C which is higher than theSnAgCu solder melting point (217∘C)When adding 06 wtFe only a single endothermic peak at 22135∘C was foundshowing that it has a eutectic composition El-Daly et al[10] studied the DSC profiles of Sn10Ag03Cu solder TheDSC revealed two endothermic peaks between 2201∘C and2272∘C The two peaks indicated two steps in the meltingprocess of SnAgCu solder Based on the ternary SnAgCuphase diagram [11] the two steps were owed to the melting ofternary eutectic 120573-Sn + Ag

3Sn + 120578Cu

6Sn5phase and primary

120573-Sn However for SnAgCu solder containing Zn only oneendothermic peak appears in the DSC curve and the melting

22

20

18

16

14

12

10

8

6

4

2

0

Hea

t flow

(120583W

)

200 210 220 230 240 250 260

Temperature (∘C)

05Mn015Ti05Ti

305

105

015Mn

2∘Cmin

(a)

05Mn015Ti05Ti

305

105

015Mn

2∘Cmin

30

20

10

0

Hea

t flow

(120583W

)

180 190 200 210 220 230 240

Temperature (∘C)

minus10

minus20

minus30

(b)

Figure 1 DSC curves of the samples (a) upon heating and (b) uponcooling [8]

temperatures were 2228 and 2208∘C for the SAC-20Znand SAC-30Zn respectively The addition of Bi decreasesthe melting point of Sn38Ag07Cu (SAC) solder [12] It isfound that the solidus temperatures of SAC-20Bi and SAC-40Bi were 21308 and 20640∘C respectively However whenadding too much Bi solder joint peeling will appear DSCscan of low-Ag Sn05Ag07Cu (SAC) solder bearing Ni andthe results showed that the addition of Ni had little effecton the melting temperature [13] The peak temperatures ofSAC SAC-005Ni and SAC-01Ni solders were 2211 2229and 2234∘CMoreover the values of melting range were 126119 and 128∘C for the SAC SAC-005Ni and SAC-01Nirespectively It is very close to 115∘C for the SnPb solder [14]It was also reported in the literature [15]









2nano-





3 Wettability







60

50

40

30

20

10

0

Wet

ting

angl

e (∘)

Wet

ting

forc

e (m

N)

12

10

8

6

4

2

0



Sn-Ag-Cu-01RE

Sn-Ag-Cu-025RE





Cu substrate





2atmosphere













2particles Liu et








0 4663 5238 4455200 3973 4762 4597400 3482 4371 3980600 3309 4529 3605






70

65

60

55

50

45

120590(M

Pa)






















2Sn3and MnSn



2Sn3



6Sn5andAg



12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











2nano-





3 Wettability







60

50

40

30

20

10

0

Wet

ting

angl

e (∘)

Wet

ting

forc

e (m

N)

12

10

8

6

4

2

0



Sn-Ag-Cu-01RE

Sn-Ag-Cu-025RE





Cu substrate





2atmosphere













2particles Liu et








0 4663 5238 4455200 3973 4762 4597400 3482 4371 3980600 3309 4529 3605






70

65

60

55

50

45

120590(M

Pa)






















2Sn3and MnSn



2Sn3



6Sn5andAg



12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




60

50

40

30

20

10

0

Wet

ting

angl

e (∘)

Wet

ting

forc

e (m

N)

12

10

8

6

4

2

0



Sn-Ag-Cu-01RE

Sn-Ag-Cu-025RE





Cu substrate





2atmosphere













2particles Liu et








0 4663 5238 4455200 3973 4762 4597400 3482 4371 3980600 3309 4529 3605






70

65

60

55

50

45

120590(M

Pa)






















2Sn3and MnSn



2Sn3



6Sn5andAg



12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











2particles Liu et








0 4663 5238 4455200 3973 4762 4597400 3482 4371 3980600 3309 4529 3605






70

65

60

55

50

45

120590(M

Pa)






















2Sn3and MnSn



2Sn3



6Sn5andAg



12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




70

65

60

55

50

45

120590(M

Pa)






















2Sn3and MnSn



2Sn3



6Sn5andAg



12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




12

10

8

6

4

2

180

160

140

120

100

80

60

40

Har

dnes

s (G

pa)

Mod

ulus

(Gpa

)





2O3nanoparticles







6 Microstructures


3Sn and







3Sn and Cu



2Cu intermetallic


3Sn






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






3(Sn Sb) and the




3Sn and Cu







3phase




3 and YSn



3Sn


2phase











3Sn grains size and








3nanoparticles







(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c)


O3

and (c) SAC-10Al2

O3

[58]


3Sn and







4 Ag3Sn and Cu

6Sn5










3Sn and Cu

6Sn5was






6Sn5 Cu3Sn





6Sn5




Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Sn5


3








6(Sn In)

5and Cu

3(Sn In)


6(Sn In)









3Sn








(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)




6Sn5and Cu






6Sn5changes from a



3Sn was


6Sn5 However



3Sn Due to the



6Sn5












2into SnAgCu solder




3rein-


3




8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






8 SN Whiskers



3causes


3has a significant


2LaSn3+3

2O2997888rarr La

2O3+ 6Sn (1)


2+ 3Sn (2)

2YSn3+3

2O2997888rarr Y

2O3+ 6Sn (3)


20120583m



3phase for whiskers



9 Conclusions


2O3 ZrO2




Acknowledgments




References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





References





















2

O3





2
































2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
























2












2

O3




2






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






















3



2

































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



review article properties and microstructures of sn-ag-cu

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