comparacion de au lashed pdni contact

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Proceedings of the 56th IEEE HOLM 2010 Conference on Electrical Contacts, September 2010This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by

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Comparison of Hard Au versus Hard Au Flashed PdNi as a Contact Finish

Marjorie Myers

Tyco Electronics, Harrisburg, PA – USA

AbstractThis work addresses the comparison of hard Au versushard Au flashed PdNi contact finishes. Extensivequalification and re-qualification data are available, butthis testing varies greatly and by definition is designed to‘pass’ or ‘fail’ a connector design. Since this type of testingdoes not specifically compare variations in finish

parameters, the ability to directly compare such data setsrelative to finish performance is limited. In addition, PdNihigh speed plating chemistries have evolved since the1980’s when they were first developed and qualified inresponse to increases in gold metal prices. Therefore, thetesting was done to provide product level data comparingthe two gold based finishes. To specifically compare finish

performance, as opposed to connector performance; usingcurrent industry accepted testing conditions and finishvariations. To better understand the contact performanceimplications of interchanging these two gold based

finished.

Keywords: Hard Gold, Palladium-Nickel, Low LevelContact Resistance, Durability, Contact Performance

I. INTRODUCTION

The hard gold (Au) vs. hard gold flashed Palladium-Nickel (PdNi) question is not a new one. There isconflicting assessments of whether hard Au and PdNiperform equivalently or not. Extensive qualification and re-qualification data is available, but this testing by definitionis designed to ‘pass’ or ‘fail’ a part and/or meet customerdemands – not directly compare variations in finishparameters. Also, this testing is done under a great varietyof conditions and finish parameters. In the literature, thereis seemingly conflicting data for testing done using manydifferent sample/testing combinations – many times notdirectly comparable. In addition, PdNi high speed platingchemistry has evolved between the 1980’s when the firstPdNi platings baths were developed in response to theincrease in gold metal price. Most of the data in the

literature was generated using these original PdNi platingchemistries. The issue is that there was no set of finishlimited data that compares the finishes under conditionscurrent product has to meet.

II.BACKGROUND, INDUSTRY REQUIREMENTS,ISSUES

As the cost of Au spiked in the 1970’s, Pd was pursued asan alternative ‘noble’ finish that could be deposited usingthe high speed plating processes prevalent in the connectorindustry.

Pd is not as ‘noble’ as Au; it has catalytic characteristics,and will react with chlorine containing environments toform resistive films on contact surfaces where exposed.This leads to a potential risk for frictional and/or frettingpolymerization generated insulating films being formed oncontact interfaces under organic vapor conditions [1]. Anissue inherent to electrodeposited pure Pd is the potentialincorporation of any hydrogen generated at the cathodeduring the deposition process (e.g., at plating processefficiencies less than 100%) leading to formation ofunstable beta phase Pd. Subsequent release of theincorporated hydrogen causes the beta phase within thedeposit to transform to the more stable alpha phase. Thistransition generates stress within the Pd deposit greatenough to exceed the yield point and cause spontaneousmicrocracking of the deposit [2] [3] [4] [5]. This couldoccur just after plating or some time afterwards dependingon the level of incorporated hydrogen and rate at which thehydrogen evolves. These crack sites can lead to excessivelocalized corrosion and inferior durability.

Through the 1980’s, the connector and plating chemistryindustries worked to develop a high speed electrodepositedPd based alloy finish that would not exhibit microcrackingwith a contact performance characteristics comparable tohard Au. It was determined that adding sufficient levels ofNi (a minimum of 10%) to the Pd electrodepositsuppresses hydrogen uptake and the formation of the lessstable beta phase thereby suppressing the risk ofmicrocracking. Additionally, the Ni tends to suppress theformation of frictional/fretting polymers sometimesassociated with the pure Pd deposits [6] [7] [8] andpossibly reduce porosity of the deposit as compared to hardgold platings [9] [10]. Adding Ni to the deposit alsoreduces the corrosion resistance of the deposit. Using PdNiin the finish is not strictly a complete replacement for hardAu.


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Proceedings of the 56th IEEE HOLM 2010 Conference on Electrical Contacts, September 2010 2

Through the development of the PdNi finish, it wasdetermined that the use of a Ni underplate and a hard Auflash overplate are required to get acceptable durabilityperformance [1] [4] [5] [11]. The Au flash also has theadded advantages of attenuating the potential risk ofgenerating chloride films and frictional polymers. Inaddition, the Au flash greatly improves the solderability of

such deposits [ 12] [13] and improves fretting performance[14]. The process of developing the PdNi deposits alsogenerated the recommendation to use a lubricant wheneverpossible to further enhance durability as well as inhibitcorrosion and cause any frictional/fretting polymer thatmay form to be non-adherent and therefore easily removedwith wipe [4] [5] [8] [9].

Because the alloy composition of high speedelectrodeposited PdNi can fluctuate with process variation,the plating process requires a relatively large acceptablecomposition range. The term ‘PdNi’ as used in theconnector industry has come to mean the industry standardof a nominal 20 ± 10wt%Ni finish Pd alloy plating with a

hard Au flash top plate and a minimum 1.25 micron Niunderplate. A minimum of 10wt% Ni to preventmicrocracking and a maximum of 30wt% Ni to allow forprocess fluctuations but limit the effect of oxidation of anyexposed Ni within the Pd alloy [11] [13] [15].

A. PdNi high speed plating bath processes:

The dual metal high speed plating chemistries for PdNiare inherently more complex and can be more difficult tocontrol in a production environment than the simpler hardAu chemistries [16] [17] [18]. The initial high speed ‘highammonia’ PdNi plating bath formulation used up into the1990’s were palladium chloride based and required a high

level of ammonia and a pH on the order of 8.0 [7] [12][16] [17] [18] [19]. These baths tended to corrode stainlesssteel, the high pH could potentially lead to passivation ofthe Ni underplate and adhesion problems, and ammoniaodors could be prohibitive to personnel if the air handlingsystems were insufficient. This chemistry was used togenerate the samples for most of the PdNi connector finishperformance qualification work in the 1980’s.

In the mid 1990’s, the next generation, or ‘low ammonia’PdNi high speed palladium sulfate plating chemistries wereintroduced and have gained wide acceptance within theindustry. These chemistries require significantly lowerlevels of ammonia, generally run at a lower pH (~ 7.0), and

have better process control characteristics [3] [20].Therefore the risk of stainless steel corrosion and thepotential for nickel passivation/poor adhesion are no longersuch a potential problem. This is the bath predominantlyused in the industry at this point.

There is a ‘no ammonia’ high speed plating chemistrythat runs at a pH on the order of 4.5 and is considered tohave none of the minimal risk for Ni passivation/adhesionissues. It was introduced prior to the Pd price spike that

started just prior to 2000, but at that point the industryswitched back to mostly using hard Au finishes. Therefore,at this time, this formulation is available, but has limitedconnector production process history. Reference [21] hassome information comparing the plating bath formulations.

Other Pd alloy finishes were developed, but have notgained acceptance for use in the connector industry. PdAg

formulations were pursued in the 1980’s, but they didn’tprove to have stable enough performance for use in theconnector industry [8], though why was never fullyunderstood . A PdCo high speed formulation wasintroduced in the 1990’s [22]. What was really attractiveabout PdCo is that it has none of the thicknessmeasurement issues associated with not being able todetermine the Ni/Pd deposit ratio over a Ni deposit.Unfortunately, it did not prove to exhibit consistent enoughcharacteristics to be adopted by the industry before theprice of Pd spiked around 2000 [23] [24]. PdCo isavailable through Enthone, but it is not industry accepted atthis point and is not proven for connector applications.

B. Alloy content variations and thickness measurementlimitations:

The wide range of acceptable Pd content (20 ± 10wt%Ni) and fluctuation across a part required by processingdegrades the capability of the X-ray Fluorescence (XRF)technique to accurately measure PdNi deposit thickness,much less over the required Ni underplate. The XRFthickness measurement technique calculates thickness bycomparing the number of X-rays counts characteristic ofeach element in the deposit to that of a set of knownthickness comparable standards with a specific PdNi alloycontent (e.g., 20wt%Ni). XRF techniques cannot

differentiate Ni atoms within the PdNi from the Ni atomsin the Ni underplate to accurately determine the Pd contentof the PdNi plated over a Ni underplate. Deviations of thePd content of the PdNi layer, and Ni layer thickness, awayfrom the known standard set also degrade the accuracy ofsuch a measurement. This limitations issue is well knownin the industry, but XRF is still the available non-destructive high speed process control method andnecessarily used to generate the contacts for this study.

C. Reported PdNi contact performance:

As PdNi was introduced and marketed as a contact finishusing mostly the ‘high ammonia’ deposition processes, the

suppliers reported either ‘equal or superior’ contactperformance compared to the hard Au finishes [1] [7] [8][12] [19] [9] [10] [25]. This ‘better durability’characteristic was attributed to the reported reducedporosity, and that electrodeposited PdNi is inherentlyharder than hard Au. A lot of the PdNi testing datareported during this development and validation processwas done using normal forces in the range of 150 - 300grams force – higher than is typically used today.


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Literature and internal company contact performancedata from the end users were not as consistent and notnecessarily as positive [14] [16] [23] [24] [18] [26]. PdNihas worked well in many applications. It is not clearlyunderstood if these different performance results have beendue to process, deposit characteristics, or other connectordesign parameters.

III. TESTING PROCEDURES AND CONNECTORS

The idea for this work was to compare Au and PdNifinishes while limiting the influence of non-finish platingprocess and connector design factors: in a way that wouldbe most useful for the connector community. Therefore, atesting procedure was developed using Lean Design for SixSigma (LDFSS) tools with input from various connectorengineering interests Development, Product,Manufacturing, Technology, Testing, and Sales/Marketing.The final DOE style/statistical analysis test procedure

incorporated connector design factors, productionprocesses, and data analysis.

Necessarily, there were two similar but separate testgroups: one lubricated and one unlubricated toaccommodate different durability levels. In order tocomparatively evaluate finish performance as a function offinish, thickness, and finish mixing under corrosive gas and

durability exposures, beam finish and flat finish weredesignated as 2 level attribute factors and total preciousmetal thickness and durability cycles were designated assingle centerpoint, 2 level continuous factors. TABLE Ishows the parameter ranges used. The various finishcombinations tested are listed as a 4 digit pattern (e.g., 11-+). Patterns mean the combination of beam finish, flatfinish, thickness, and durability. The first digit is the beamfinish and the second digit is the flat finish: 1 = Au or 2 =PdNi. The third digit is the finish thickness level and thefourth digit is the durability level. Thickness (third digit)and durability (fourth digit) are designated as either ‘-’ =Level 1, ’+‘ = Level 2, or ‘0’ = center levels.

TABLE ITESTING FACTORS

Lubricated UnlubricatedVariables Data Type Level 1 (-) Level 2 (+) Center (0) Level 1 (-) Level 2 (+) Center (0)Durability continuous 0 100 50 0 20 10precious metal thickness continuous 0.25 µm 1.40 µm 0.83 µm 0.25 µm 1.40 µm 0.83 µmFlat Finish attribute Au PdNi Au PdNiBeam Finish attribute Au PdNi Au PdNi

a) Receptacle connector b) Housing c) Receptacle contact surface

d) Header connector e) Header pin array f) Header contact surface

g) Receptacle chicklet beam mating deflection – 6 one way, 6 the opposite directionFigure 1: header/receptacle connector system micrographs


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A. Test Connector:

It was decided to use an existing 12x12 (total of 144replicate contacts per connector) array connector system(instead of lab created samples) to do this testing to makethe results more useful to the engineering community(figure 1). Each contact pair consists of a single formed

beam mated to a flat pin. Each contact has 2.77 mm wipeat a nominal normal force in the range of 80-50 gramsforce, is press-fit mountable, and has an existing postassembly lubrication method. Additionally, the header hasa relatively open pin array allowing for minimal gasshielding in the unmated state.

B. Test Method:

The test method is based on industry acceptedqualification procedures that noble metal finished productare required to ‘pass’ in order to maximize the relevance ofthe results to the connector community (an adapted form ofthe finish relevant part of EIA 364 1000A.01A, test group

4 (TG4)) [27]. The degradation methods used to stress thefinishes are durability and Class IIa Mixed Flowing Gas(MFG) exposure. Thermal ageing was omitted because the

lubricants were to be evaluated in the ‘as-applied’ state.

TABLE IIEXPOSURE PROCEDURE

Lubricated UnlubricatedTest or Examination(number denotes order in test sequence) Level 1 Level 2 centerpoint Level 1 Level 2 centerpointLLCR 1,3,5,7,9,

111,3,5,7,9,

11,131,3,5,7,9,11,

131,3,5,7,

9,111,3,5,7,9

,11,131,3,5,7,9,

11,13

PRE Durability (100 cycles) 2PRE Durability (50 cycles) 2PRE Durability (20cycles) 2PRE Durability (10 cycles) 2

Unmated Class IIA MFG, (5 days) 2,4,6,8 4,6,8,10 4,6,8,10 2,4,6,8 4,6,8,10 4,6,8,10

Post Durability (100 cycles) 12Post Durability (50 cycles) 12Post Durability (20 cycles) 12Post Durability (10 cycles) 12Number of boards 4 4 2 4 4 2

Exposure cycles 4 2

Four durability/5 day class IIa MFG LLCR measurementcycles were done for the lubricated samples and two weredone for the unlubricated samples. All MFG exposureswere done in the unmated state to minimize the effect ofhousing shielding. TABLE II shows the exposureprocedure used. The numbers in Table II representexposure sequence order.

C. LLCR measurement:The main ‘performance metric’ required by TE

customers in most precious metal plated signal contactapplications is low and stable Low Level Contact

Resistance (LLCR). LLCR current and voltage levellimitations avoid altering (e.g. reducing) the measuredresistance of the contact interface through electrical and/orthermal breakdown. Using LLCR measurement exclusivelyalso leads to the risk of getting ‘opens’ or unreadablecontact interfaces under LLCR conditions. This factlimited subsequent data analysis options in some cases.Delta LLCR (change in LLCR from initial values) is usedin the data analysis to exclude the variable bulk resistance

inherent to product resistance measurements (maximum ~35 milliOhm (m Ω)). Since the measurement system couldread no greater than 200 m Ω in the LLCR state, any deltaLLCR readings above 150 m Ω were considered to be‘open’.

IV. RESULTS AND ANALYSIS

When possible, the following analysis was done usingAnova and Tukey-Kramer HSD means comparisons. Todetermine if any differences in the delta LLCR

performance of the different finish combination/exposuresis statistically significant. This could be done with all thelubricated delta LLCR data ( as-durability cycled, 5 day,10day, 15day, and 20 day MFG exposures) and the as-durability cycled, 5 day, and 10 day exposure unlubricateddelta LLCR data. Data in the statistical comparisons arerepresented as data points, quantiles centered on themedian (red boxes), and Means Anova (green diamonds),and Tukey Kramer HSD (red circles).


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A . Means comparison statistical analysis of the effect ofnon-finish contact position factors afterdurability/corrosive gas exposure

Statistical means comparison analysis was done todetermine if the effects of non-finish factors such as outeredge header row position (increased relative corrosive gasflow – figure 1d white arrow), proximity to a headerhousing wall (reduced corrosive gas flow – Figure 1d), andbeam deflection direction (figure 1g) were significant.

Each test board set holds two connectors adjacent toeach other so each header has one outer edge of contactswith no outside nearest neighbor (12 contacts total perconnector). Therefore, these outer edge pins experience agreater flow of the corrosive gases within the MFG testchamber than the inner pins in the unmated state. It wasdetermined that there was no statistical significance toposition among the inner pins; but there was an overallstatistical difference trend for the contacts located in theouter positions. Figure 2a shows an example of such ananalysis showing that the outer row positions hadsignificantly higher delta LLCR values. The Anovadiamonds and the Tukey Kramer circles visually illustrate

the statistical differences. This effect was most significantfor the thinner finish combinations.A few of the center and thick finish combination data setsexhibited significant differences between the outer row andinner row data, but with a means difference on the order ofa fraction of a m Ω. Based on these results showing thestatistical significance associated with the outer pin

positions, especially for the thin platings data, all outer rowdata was excluded from for further analysis reducing thedata set size from 144 to 132 replicates.

Statistical analysis was also done to determine if the dataassociated with any particular row parallel to the headerwalls was significantly different. It was determined thatthere was none, even for the 24 contacts located in the tworows located adjacent to the housing walls for all thesample types tested. Similarly, no statistical significanceassociated with receptacle beam deflection direction wasfound in the data. The Anova diamonds and Tukey-Kramercircles in figure 2b show the data are statisticallyindistinguishable.

d e

l t a L L C R ( m O h m

)

d e

l t a L L C R ( m O h m

)

a) outer row proximity comparison- statistically different

b) header wall proximity / deflection directioncomparison – no statistical difference

Figure 2: Examples of means comparison statistical analysis of the lubricated, 4 cycle (20 day MFG), level 1 durability, delta LLCR data:thin Au mated to thin Au comparing position factors

B. Means comparison statistical analysis of platingcombinations in the as-durability cycled (pre MFGexposure) delta LLCR data and 1 cycle (5 days MFG total)exposure delta LLCR data – comparing lubrication statesand thickness

A similar means comparison analysis was done on the‘as-durability cycled’ data to determine if the various thickand thin PdNi and Au combinations are statistically

different prior to MFG exposure (figure 3). This type ofcomparison was also done for the ‘1 cycle’ (5 day MFG)delta LLCR data (figure 4). This statistical comparisoncould not be done for any exposure greater than ‘1 cycle’(5 day MFG) exposure because of the level of ‘openLLCR’ data points in the unlubricated ‘2 cycle’ (10 daysMFG) exposure data.

Figures 3 shows there are statistically significantdifferences between the different finish combinations for

both the thick and thin combinations in the as-durabilitycycled state. The thin plating lubricated samples exhibiteda statistically lower delta LLCR than the unlubricated deltaLLCR data (figure 3a). There are also statisticallysignificant differences within the thicker plating deltaLLCR data (figure 3b), but there is no statistically lowertrend differentiation between the lubrication states. Thereality is that the level or range of these differences wouldnot be functionally significant in the vast majority of

connector applications. Comparison of the corresponding‘1 cycle (5 day MFG) with durability cycling’ data infigures 4a (thin) and 4b (thick) illustrates how dramatic aneffect the use of a lubricant can have on delta LLCRperformance after MFG exposure. There is also anindication that the unlubricated PdNi mated to PdNi (“22”)delta LLCR data is lower and not statistically different thanthe lubricated data at this 5 day exposure for both the thinand thick platings.


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a) thin plating ‘as durability’ cycled b) thick plating ‘as durability’ cycledFigure 3: Means comparison of the as-durability cycled delta LLCR data for both the thin and thick platings: lubricated vs. unlubricated(Au/Au = ‘11’, Au/PdNi = ‘22’, PdNi/Au = ‘21’, PdNi/PdNi = ‘22’)

d e

l t a L L C R

( m O h m

)

1 1

− +

1 2

− +

2 1 −

+

2 2 −

+

L 1

1 −

+

L 1 2 −

+

L 2 1 −

+

L 2 2 −

+

a) thin plating ‘1 cycle’ MFG with durability cycling b) thick plating ‘1 cycle’ MFG with durability cyclingFigure 4: Means comparison of the ‘1 cycle (5 day MFG) with durability cycling’ exposure data for both thin and thick plating delta LLCRdata: lubricated vs. unlubricated (Au/Au = ‘11’, Au/PdNi = ‘22’, PDNi/Au = ‘21’, PdNi/PdNi = ‘22’)

The main conclusions that can be drawn from thestatistical comparisons of figures 3 and 4 are that Au and

PdNi perform similarly and lubrication has a strong effecton improving delta LLCR performance. There may be astatistical significance to PdNi improving delta LLCRperformance, but not to a level that could be engineeredinto a design consistently.

C. Means comparison statistical analysis of the effect of plating combinations for the lubricated 4 cycle (20 days MFG) exposure delta LLCR data and mean and maximumvalue comparison of the lubricated as-durability cycled, 5day, 10 day, 15 day, and 20 day MFG delta LLCR data

Figure 5 shows the means comparison of all lubricateddelta LLCR data after the most severe 4 cycle (20 days

MFG total) exposure. The samples are labeled using their‘pattern’ designation as described previously. Thoughdoing this means comparison of all the data sets at thesame time requires assuming an equal variance among thedata sets (not always true), it still gives statisticalcomparison and doing so helps illustrate data trends.

In this ‘worst case’ 20 day MFG exposure for all thethickness and durability levels, there were 4 sets

(designated by patterns) that were significantly differentand higher than the rest of the data sets - distinguished infigure 5 by arrows and a dotted box. The data setsindicated by the arrows (Level 2 durability thick: Au beammated to a Au flat and Au beam mated to a PdNi flat)exhibited a statistically significant increase in delta LLCR.Whether that is ‘good’ or ‘bad’ depends on what level ofperformance is needed in an application. The data setssurrounded by the dotted box (thin PdNi beam mated to athin Au flat) exhibited an increase in the number if highvalues (median and mean values diverge) – a much worsecase for connector performance.

To get a more general view of these lubricated results

including the lower exposure levels, figure 6 shows a graphshowing all the maximum values for all the conditions andexposure levels tested – with a range of 0 - 10 m Ωs. Thisgives a ‘near-far’ view for an overall comparison in thecontext of a 10 m Ω maximum delta LLCR limit. Thisrepresentation indicates a clear differentiation between thethicker platings (thick and center) and the thin platings.

40 cycles durability 200 cycles durability 40 cycles durability 200 cycles durability

LubricatedUnlubricated

20 cycles durability 100 cycles durability


20 cycles durability 100 cycles durability

Lubricated

Unlubricated



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The thicker finish delta LLCR performances for thedifferent combinations and exposures are similar in thecontext of most connector applications. Differences greaterthan a couple of m Ωs can only be seen within themaximum delta LLCR thin finish data. There are some

greater than 10 m Ω maximum delta LLCR increasesassociated with the thinner finishes in the 15 day and 20day exposure states.

d e

l t a

L L C R ( m O h m

)

1 1 +

+

1 1 +

−

1 1 −

+

1 1 −

−

1 1 0

0

1 2 + +

1 2 +

−

1 2 −

+

1 2 −

−

1 2 0

0

2 1 +

+

2 1 +

−

2 1 −

+

2 1 − −

2 1 0

0

2 2 +

+

2 2 +

−

2 2 −

+

2 2 −

−

2 2 0

0

Figure 5 Anova and Tukey-Kramer means comparison of the lubricated delta LLCR data after 4 cycles (20 day MFG) exposure comparingall data sets (Au/Au = ‘11’, Au/PdNi = ‘22’, PdNi/Au = ‘21’, PdNi/PdNi = ‘22’)

Figure 6 Mean and maximum value data comparison of lubricated delta LLCR data for all exposures and conditions – 0 to 10 mΩ range.

Beam: AuFlat: Au

Beam: PdNiFlat: Au

Beam: AuFlat: PdNi

Beam: PdNiFlat: PdNi

all lubricated data

beam Au/Au flat

beam Au/PdNi flat

beam PdNi/Au flat

beam PdNi/PdNi flat

lubricated data


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Figure 7: Cumulative ranking comparing the unlubricated 2 cycle (10 day MFG) delta LLCR data for the various combinations tested

D. Cumulative comparison plots for the unlubricated 10day MFG exposure delta LLCR results

Because of the prevalence of LLCR ‘opens’ (defined as> 150 m Ω) in the unlubricated delta LLCR data, it couldnot be analyzed statistically. To compare relative finishperformance, figure 7 shows cumulative plot ranking ofthis data. In this figure, all LLCR values of 150 m Ω orgreater were entered as ‘150’ m Ω and considered to be‘open’: an upper ceiling associated with the LLCRtechnique necessarily used in this testing for previouslydiscussed reasons.

The results for all the thick finish plating combinationswere similar for this unlubricated data with no durabilitycycling.

There is clear differentiation between the combinationtypes for the thick and center thickness data with durabilitycycling (20 and 40 cycles) with an indication that usingPdNi plated beams (header) may improve delta LLCRperformance after two cycles (10 days MFG) exposure inthe unlubricated state. When looking at the thin finish data,the thick and center thickness trend appears to reverse inthat using Au as the beam (header) finish with durabilitycycling may lead to better delta LLCR performance for the

thinner unlubricated deposits. Different applications have adifferent assessment of what ‘failure’ means. Maximumdelta LLCR requirements can be as wide as multiple Ohms

to as tight as 10 m Ω. For the thin plating that experienced40 durability cycles: neither of the PdNi beam platedcontacts would have ‘passed’ if a 10 m Ω maximum deltaLLCR was applied. What one ‘calls’ failure will effectconclusions about comparative performance.

E. Alloy content variation/thickness measurementlimitation and implications:

To minimize PdNi plating process variability, both theheader and receptacle contacts were plated on one line overthe course of one day to maintain the chemistry as much aspossible. Because the surface area and geometries of theheader and receptacle contacts were significantly different,the agitation and current density levels and distributionwere also different. These facts can lead to high speedPdNi deposition process alloy content variation (20wt%Ni± 10%) and further measurement issues as discussedpreviously. TABLE III lists the thickness measurementsused to control the plating ESR process as the targetthickness levels were generated – as would be done forproduct. The XRF data shows reasonable correlationbetween the measured XRF and targeted values.

οοοο beam Au/Au flat

beam Au/PdNi flat

++++ beam PdNi/Au flat

x beam PdNi/ PdNi flat

unlubricated data


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Knowing that there are limitations to the accuracy ofXRF thickness measurement technique applied to PdNiplatings, limited Focused Ion Beam (FIB) analysis of thePdNi layer thicknesses was done afterwards. FIB is adestructive method used to make perpendicular cuts into asurface under vacuum (~ of micrometers) from whichdeposit thickness measurements can be made.FIB is not

widely available and is not appropriate for the productionenvironment. The FIB measurements show that there wasreasonable correlation between the XRF and FIB analysisfor the receptacle (beam) contacts, but not for the header

(flat) contacts. All the header deposits were substantiallythicker according to the FIB analysis. This data shows thatconclusions that PdNi is ‘more durable’ or ‘less porous’may be more an indication of a thicker deposit. Since thePd content can vary across a single part and with thedifferent agitation and current density distributions acrossdifferent part geometries, the fact that the plating two

different geometries (receptacle and header) resulted indifferent overall thickness ranges is not unexpected.

TABLE IIIPLATING THICKNESS DATA

Measured Thickness values vs. target values ( µµµµm) Hard Au ( (µµµµm) Receptacle Header thickness description thick center thin thick center thintarget thickness 1.40 0.83 0.25 1.40 0.83 0.25average Au (XRF) 1.41 0.97 0.26 1.46 0.65 0.33PdNi (µµµµm ) Receptacle Header

thickness description thick center thin thick center thinaverage PdNi (XRF) 1.38 0.70 0.22 1.33 0.74 0.24average Au (XRF) 0.09 0.09 0.09 0.08 0.07 0.07target thickness 1.40 0.83 0.25 1.40 0.83 0.25average Au+PdNi (XRF) 1.47 0.79 0.31 1.42 0.81 0.31

average PdNi (FIB) 1.76 1.07 0.38 2.57 1.83 0.83

V. CONCLUSION

The purpose of this work was to compare finish relatedperformance factors with an understanding of how the

results could be affected by non finish and uncontrollablefactors. The main general conclusion that can be drawnfrom this work, in the context of general connectorperformance requirements, is that the different Au andPdNi combinations exhibited at times statistically differentresults but functionally similar performance. This data alsoconfirms the strong recommendation to use a lubricantwhich has a strong positive effect on maintaining lowLLCR.

This work also helps explain the fact that there areconflicting reports about relative performance of Au vs.PdNi finishes. The influence of the difficulties inmeasuring and controlling PdNi alloy levels in the

production environment cannot be ignored. The reality isthat one can try to exclude all non finish related factors(e.g., processing and measurement), but they still will playa role.

Even though there were processing related factors thatcould not be completely controlled, the overall conclusionof this work is that Au and PdNi are effectively equivalentfor most lubricated connector application requirements atequivalent thickness.

ACKNOWLEDGEMENT

The author wishes to acknowledge the assistance andsupport of the personnel within the various organizations

of TE who assisted in getting this work done.

REFERENCES

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[4] J H. Whitley, "Amp-Duragold plating," A publication of

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testing requirements for Pd-Ni alloy coatings of electricalcontacts,” Plating and Surface Finishing, vol. 79, no. 9, pp.56-61, 1992.

[11] M. Antler and M. Feder, "Friction and wear ofelectrodeposited palladium contacts: thin film lubricationwith fluids and with gold," IEEE Transactions onComponents, Hybrids, and Manufacturing Technology , vol.9, issue 4, pp. 485-491, 1986.

[12] E. J. Kudrak, J. A. Abys, H. K. Straschil, I. Kadija, J. J.Maisano, "Palladium and palladium alloy plating for the1990’s," presented at Connectors ’93 , May 19, 1993.

[13] TE document 212-6, “AMP Duragold, palladium and itsalloys.”

[14] C. A. Morse, N. R. Aukland, N.R.; and H. C. Hardee, "Astatistical comparison of gold and palladium-nickel platingsystems for various fretting parameters," Proceedings of theForty-First IEEE Holm Conference on Electrical Contacts ,pp. 33-51, 1995.

[15] AMP document 112-49, “Plating, Palladium-Nickel, 80-20% Alloy, Electrodeposited”.

[16] I. Wei, “The process variation of palladium-nickel alloyplatings - a screening study,” a publication of AMP

Incorporated, RN# 424, 1989.[17] I. Wei, “Guidelines for process control of palladium

plating,” a publication of AMP Incorporated, RN# 450, 1991.

[18 ] T. Sullivan, "Palladium nickel alloy plating as a replacementfor gold at Harrisonburg, VA," A publication of AMP

Incorporated , RN #491, 1993.

[19 ] S. W. Updegraff, "Better than gold: A palladium-nickelcoating system for high reliability connectors," Proc. 33rd

Electronics Components Conference IEEE CHMT Soc. , pp.425-431, 1983.

[20] J. A. Abys, H. K. Straschil, I. Kadija, E. J. Kudrak, and J.Blee, “The electrodeposition and material properties ofpalladium-nickel alloys,” Metal Finishing, vol. 89, no. 7,pp. 43-52, July 1991.

[21] W. Zhang, M. Clauss, J Guebey, and F. Schwager, "Low-ammonia, high-speed palladium-nickel electroplatingprocess for connector applications," Metal Finishing , vol.65, No. 1, pp. 33-37, March 2009.

[22] J. A. Abys, G. G. Breck, H. K. Straschil, I. Boguslavsky andG. Holmbom, “The electrodeposition & material propertiesof palladium-cobalt,” Plating and Surface Finishing, vol.86, no. 1, pp. 108-115, 1999.

[23] “Evaluation of the performance of new platings forconnector contacts,” a test report from Battelle to AMP, Jan1999.

[24] A. Sullivan, “Characterization of the corrosion resistanceand tribological performance of a novel palladium-cobaltsystem,” a publication of AMP Incorporated , RN# 551,1997.

[25] “GXTTM

plating is better than gold,” a test report from FCI,Jan 1999.[26] I. Wei I and S. Keister, “The process variation of sel-rex

palladex GV palladium-nickel alloy plating,” a publicationof AMP Incorporated, RN# 432, 1989.

[27] “EIA 364 1000.01A - Environmental Test methodology forassessing the performance of electrical connectors andsockets used in controlled environment applications, April2006.”

comparacion de au lashed pdni contact

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