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Pb-Free Wave Soldering
Project
Denis Barbini, Vitronics Soltec,
ChairPaul Wang,
Microsoft, Co-Chair
APEX 2007
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Phase I Project ParticipantsPhase I Project Participants
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Denis BarbiniVitronics Soltec, Inc.Stratham, NH, USA
Paul WangMicrosoft, Inc.
Mountain View, CA, [email protected]
Peter BioccaITW Kester, Inc.Allen, TX, USA
Quyen ChuJabil, Inc.
San Jose, CA, [email protected]
Tim DickCisco Systems, Inc.San Jose, CA, [email protected]
Denis JeanPlexus, Inc.
Neenah, WI, [email protected]
Stuart LonggoodDelphi CorporationKokomo, IN, USA
Chrys SheaCookson Electronics, Inc.
Jersey City, NJ, [email protected]
Keith SweatmanNihon Superior, Inc.
Nihon Superior Co., Ltd.Osaka, Japan
Mike YuenFoxconn, Inc.
Houston, TX, [email protected]
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2007 iNEMI Wave Roadmap2007 iNEMI Wave Roadmap
Courtesy: iNEMI
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Lead Free Wave Soldering Project GoalsLead Free Wave Soldering Project GoalsThis investigation looks to determine the impact of process parameters and materials on the wave
soldering process and solder joint formation.
This study aims to provide insight into the process issues that one will encounter so that arational implementation strategy for a robust lead free wave soldering process can be achieved.
The Phase I iNEMI Lead Free Wave Soldering Project focused on three critical areas: • Materials Selection
Fluxes, alloys, components, and board complexity.• Process Optimization
Defined “Window of Opportunity” based on flux amount, preheat temperature, contact time, soldertemperature, wave configuration, and atmosphere.
• Solder Joint Yield Defined failure levels and defect types using inspection criteria – IPC class 3 combined with best practices, yield determined by hole fill characterized by 5DX data analysis.
The result of Phase I is to lay the foundation for a broader effort to characterize thereliability of through-hole joints on a test vehicle specifically designed to test the norms andpractices used in tin lead wave soldering and develop new standards for lead free wavesoldering.
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Getting StartedGetting Started““brainstormingbrainstorming””
Experimental design and execution
Equipment setup and data reporting
Materials
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Design of Experiment for Phase IDesign of Experiment for Phase I• Taguchi Methodology Chosen
–Time and cost efficient for studying multiple variables.–DoE based on standard Taguchi L18 (21 x 37)orthogonal array.
• Variable Selection–Brainstorming to collect list of possible variables for wave solder process. This represented perspectives of many areas of assembly.–Review by team members to prioritize list.–Discussion and consensus vote to pick final selection.
Inner Array VariablesAtmosphere,
conveyor speed, preheat temperature,
flux quantity, flux type, chip wave,
solder temperature, board thickness
Outer Array Noise FactorsSAC 305, Sn100C, SACx, SnPb,
CuOSP finish,Pb-free HASL finish
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Machine ConfigurationMachine ConfigurationDelta Wave Solder machineFluxer:Spray fluxer FC7 for Alcohol and OAFC16 for VOC free Pump supply system
Preheat configuration:Forced convectionForced convection Calrod Profiles Attributes
Flux amount and penetrationMass measurement and pH paperPreheating Temp:ECD Super Mole Contact Time:ECD Wave Rider
Solder pot configuration:Chip wave Main wave
Nitrogen:Inerting Blanket system betweenwaves: 30-50-80 l/min
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Test Vehicle Test Vehicle ““SkateSkate””(Cookson Design)
No connection Shorter spokes on WW Longer spokes on WW Direct to ground plane(Cookson Design)
Board Specification–64 mil–93 mil–135 mil–CuOSP–HASL
Alloys–SAC 305–SACX–Sn100C–SnPb
Components–QFP’s, SOT, Passives–PCI, Berg Stick
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Experimental ExecutionExperimental Execution
SpeedFt/min
(cm/min)1 5 N2 4.5 (138) med med OA on 255 0.0622 1 N2 3 (92) low low Water on 255 0.0623 16 Air 6 (183) low high Alcohol on 255 0.0944 12 Air 2 (61) high med Alcohol on 255 0.1355 14 Air 3.5 (107) med high Water off 255 0.1356 9 N2 6 (183) high low OA off 255 0.0947 10 Air 3 (92) low high OA off 265 0.0628 2 N2 3 (92) med med Alcohol off 265 0.0949 15 Air 4.5 (138) high low Alcohol on 265 0.062
10 7 N2 5 (152) low med Water on 265 0.13511 6 N2 4.5 (138) high high Water on 265 0.09412 17 Air 5 (152) med low OA on 265 0.13513 13 Air 4.5 (138) low med OA on 275 0.09414 4 N2 3.5 (107) low low Alcohol off 275 0.13515 8 N2 6 (183) med high Alcohol on 275 0.06216 11 Air 3 (92) med low Water on 275 0.09417 3 N2 2 (61) high high OA on 275 0.13518 18 Air 6 (183) high med Water off 275 0.062
Board Thickness
Flux Quantity
Flux Type
Chip Wave Solder Temp (°C)
Actual Run Order
DOE Standard
OrderAtmospher
e
Preheat Temp
Required for logistics reason
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Data CollectionData Collection““working hardworking hard””
Bridging
Through Hole Penetration
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Analysis: Bridging with SAC 305Analysis: Bridging with SAC 305
SAC 305 on SAC 305 HASL
Total shorts on HASL: 299
SAC 305 on OSP
Total shorts on OSP: 451
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5DX Measurement Calculation5DX Measurement Calculation
Confirmed by select cross sectioning and typical X-Ray techniques
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Through Hole Inspection CriteriaThrough Hole Inspection Criteria
No defect DefectS3-25%
DefectS3-25%S1-50%
DefectS3-25%S1-50%S4-75%
DefectAll Slices
DefectS2-0%
DefectS3-25%S1-50%S4-75%
DefectS4-75%
Void
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AnalysisAnalysis““interestinginteresting””
Influence of process parameters and materials
Optimized Process
Confirmation
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Occurrence of Bridging on QFPOccurrence of Bridging on QFP
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Determination of Optimized Parameters for Minimal BridgingDetermination of Optimized Parameters for Minimal BridgingSm
alle
r the
Bet
ter AirN it rogen
30
20
10
H ighMediumLow H otW armC ool
H ighMediumLow
30
20
10
33551880330 Of fOn
275265255
30
20
10
0.1350.0940.062
A tm osphere B elt speed P rheat tem p
F lux am ount F lux ty pe C hipw av e
S older tem p B oard thckn
Bridging SAC305 - HAL boards
Smal
ler t
he B
ette
r A i rNi tro g e n
4 0
3 0
2 0
Hig hM e d iu mL o w Ho tWa rmCo o l
Hig hM e d iu mL o w
4 0
3 0
2 0
3 3 5 51 8 8 03 3 0 O ffO n
2 7 52 6 52 5 5
4 0
3 0
2 0
0 .1 3 50 .0 9 40 .0 6 2
A tm o sp h e re B e l t sp e e d P rh e a t te m p
Flu x a m o u n t Flu x typ e Ch ip wa ve
S o l d e r te m p B o a rd th ckn
B ridging SAC305 - O SP boards
General RemarkFor the PCI connector, as the board thickness increased, the lead protrusion decreased.For the Berg Stick connector, the lead protrusion was kept constant over the three board thicknesses by mechanical means.
Bridging was found to be correlated to lead protrusion.
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Interactions of Process Parameters on BridgingInteractions of Process Parameters on Bridging
To avoid bridgingSelect a proper flux, amount, and inert soldering environment
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How to Minimize Bridging Based on Process and MaterialsHow to Minimize Bridging Based on Process and Materials
Recommended SettingsAtmosphere: NitrogenBelt speed: Med/HighPreheat temp: CoolFlux amount: High
Chip wave: OffSolder temperature: 265ºC
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Open Joints/Skip on SOTOpen Joints/Skip on SOT’’ss
•The orientation of the SOT is a critical design factor. (1.5x more defects)
•Chip wave operation results in improved soldering results.(Double wave former prevents shadow effects)
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Hole Fill Defect AnalysisHole Fill Defect Analysis
SAC 305
SpeedFt/min
(cm/min)HASL OSP
1 5 N2 4.5 (138) med med OA on 255 0.062 0.0 0.02 1 N2 3 (92) low low Water on 255 0.062 2.0 2.73 16 Air 6 (183) low high Alcohol on 255 0.094 41.0 44.04 12 Air 2 (61) high med Alcohol on 255 0.135 32.7 200.05 14 Air 3.5 (107) med high Water off 255 0.135 399.0 394.36 9 N2 6 (183) high low OA off 255 0.094 48.0 44.37 10 Air 3 (92) low high OA off 265 0.062 0.0 0.08 2 N2 3 (92) med med Alcohol off 265 0.094 3.0 0.09 15 Air 4.5 (138) high low Alcohol on 265 0.062 0.0 0.0
10 7 N2 5 (152) low med Water on 265 0.135 358.3 350.311 6 N2 4.5 (138) high high Water on 265 0.094 0.3 0.312 17 Air 5 (152) med low OA on 265 0.135 56.3 47.313 13 Air 4.5 (138) low med OA on 275 0.094 6.0 25.014 4 N2 3.5 (107) low low Alcohol off 275 0.135 56.7 80.315 8 N2 6 (183) med high Alcohol on 275 0.062 2.3 3.016 11 Air 3 (92) med low Water on 275 0.094 1.7 37.017 3 N2 2 (61) high high OA on 275 0.135 58.7 55.018 18 Air 6 (183) high med Water off 275 0.062 1.0 1.0
Board Thickness
SAC 305Flux Quantity
Flux Type
Chip Wave Solder Temp (°C)
Actual Run Order
DOE Standard
OrderAtmospher
e
Preheat Temp
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Response: Mean CountAverage Number of Holes per Board w/<75% Fill
SAC305
020406080
100120140160180200
N2
Air
Slow Med
Fast
Coo
lW
arm
Hot
Flux
Flux
Med
Flux
Wat
erA
lcoh
ol OA
Chi
p O
nC
hip
Off
255
265
275
0.06
20.
094
0.13
5
305OSP
Impact of Process Impact of Process Parameters on Hole Parameters on Hole
FillFill
SAC 305SAC 305
Response: Mean CountAverage Number of Holes per Board w/<75% Fill
SAC305
020406080
100120140160180200
N2
Air
Slow Med
Fast
Coo
lW
arm
Hot
Flux
Flux
Med
Flux 33
018
6833
55
Chi
p O
nC
hip
Off
255
265
275
0.06
20.
094
0.13
5
305HASL
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Confirmed Optimized ProcessConfirmed Optimized Process
Alloy Atmosphere Speed Preheat Temperature
Flux Amount Flux Type Solder
TemperatureBoard
Thickness
(ft/min) (°C) (°C) (mil)SAC 305 N2 3 130 Med Alcohol 265 62, 93, 135
SACx N2 3 110 Med Alcohol 265 62, 93, 135SN100C N2 3 110 Med Alcohol 265 62, 93, 135
• Process was confirmed by soldering at the defined process settings and materials.
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Confirmation ResultsConfirmation Results
• Process confirmation was not positive for the 135 mil board indicating the influence of board complexity and lead protrusion.
No connection Shorter spokes Longer spokes Direct to G.P.
Board Thickness SAC305 SACx Sn100C
62 mil 0 0 093 mil 0 0 0
135 mil 2 7 3
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TrendsTrends““learning as we golearning as we go””
Points of Interest
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Influence of Copper TieInfluence of Copper Tie--InIn
Short spoke; no tie-in; long spoke; direct tie-in
Root Cause Analysis• An un-optimized process will
produce such results.• Board complexity – thickness
and layers – will significantly influence the process’ window of opportunity.
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Influence ofInfluence ofLead ProtrusionLead Protrusion
Hole fill and Bridging are directly affected and trends were quantified
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ConclusionsConclusionsThis investigation determined the impact of process parameters and materials on the
wave soldering process and solder joint formation.
This study provided insight into the process issues that one will encounter during so that a
rational implementation strategy for a robust lead free wave soldering process can be achieved.
Phase I of this project provided information of each of the critical areas that was the focus.
Materials SelectionThe interaction of the various materials on the formation of defects was quantified.
Process OptimizationDetermined and tested the optimized process based on materials and parameter control.
Solder Joint Yield Defined failure levels and defect types using inspection criteria – IPC class 3 combined with best practices, yield determined by hole fill characterized by 5DX data analysis.
The result of Phase I was to lay the foundation for a broader effort to characterize thereliability of through-hole joints on a test vehicle specifically designed to test the
norms and practices used in tin lead wave soldering and develop new standards for lead free wavesoldering.
28
Phase IIPhase II““the end goalthe end goal””
Unique Board Design
Fixed Process
Lead Free Solder Joint Performance
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GTLO Test VehicleGTLO Test Vehicle
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T e s t C o n d i t i o n A l l o y T h i c k n e s s S u r f a c e F i n i s h
O S PN i A u
I m m A gH A S LO S PN i A u
I m m A gH A S LO S PN i A u
I m m A gH A S LO S PN i A u
I m m A gH A S LO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A u
I m m A gH A S LO S PN i A u
I m m A gO S PN i A u
I m m A gH A S LO S PN i A u
I m m A gO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S PN i A uO S P
0 . 0 9 3
0 . 0 9 3
S n C u N i0 . 0 6 2
0 . 0 9 3S A C x
0 . 0 6 2
0 . 0 9 3
S n P b
0 . 0 6 2
S A C
0 . 0 6 2
S A C
0 . 0 6 2
S n C u N i0 . 0 6 2
I n i t i a l A n a l y s i s ( X - s e c t i o n , X - r a y , P u l l ,
S h e a r , e t c … )
0 . 0 9 3S A C x
0 . 0 6 2
0 . 0 9 3
0 . 0 9 3
0 . 0 9 3
A T C - 4 0 t o 1 2 5 C
S n P b
0 . 0 6 2
0 . 0 9 3
0 . 0 9 3A T C 0 t o 1 0 0 C
S n P b0 . 0 6 2
S A C0 . 0 6 2
0 . 0 9 3
0 . 0 9 3D r o p
S n P b0 . 0 6 2
S A C0 . 0 6 2
0 . 0 9 3
0 . 0 9 3
V i b r a t i o n
S n P b0 . 0 6 2
S A C0 . 0 6 2
S n C u N i0 . 0 6 2
0 0 9 3
ScopeScope
Interest Test Alloy Thickness Surface FinishCore - Baseline - - - -Temp Age -40 to 125C SAC 0.093 OSPSelective Solder -40 to 125C SAC 0.093 OSPother -40 to 125C SAC 0.093 OSP
• 600 boards• 300,000 components• 3 alloys, 4 finishes, 1
flux, 2 thicknesses
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AcknowledgementsAcknowledgements
• The authors and project members would like to gratefully thank the following people for support during the execution of Phase I and its analysis: John Norton, Norm Faucher, Gerjan Diepstraten, and Bruce Quigley for build support, Ursula Marquez de Tino for the many cross sections, Sam Greenfield for performing all of the 5DX analysis.
• The authors would also like to thank the management of each participating company for their support in this endeavor. Without their continued support, this project would not have achieved its Phase I goals.
Lead-Free Rework
Optimization Project
Project Chair: Jasbir Bath Solectron Corporation
Project Co-Chair: Craig Hamilton, Celestica
IPC APEX 2007February 20 , 2007