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Lead Free Process GroupLead Free Process Group

Jasbir BathSolectron Corporation

Process Team Leader01-17-01

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AcknowledgementsAcknowledgements

• NEMI Lead Free Process Team

– Len Poch, Maurice Davis Universal Instruments

– Jeff Schake DEK USA Denis Barbini Vitronics-Soltec

– Oliver Bast Orbotech Steve Martell Sonoscan

– Mark Walz, Terry Leahy, Harold Hyman SRT/Genrad

– Jeremy Jessen Agilent

– Jana Coustineau Alcatel Frank Grano SCI

– Chuck Woychik IBM

– Al Gickler Johnson Manufacturing

– Ray Altieri Indium Corp.

– Dennis Bernier Kester Solder

– Rob Herber Alpha Metals

– Brian Bauer Heraeus

– Thilo Sack Celestica

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AgendaAgenda

• Paste Evaluation (Solectron Milpitas)– Paste printability, X-ray inspection, Reflow

profile, Cross-sections, Pull/Shear tests

• NEMI Reliability Test board builds(Universal Instruments) - Printability,Placement, Reflow, Electrical Inspection

• X-ray inspection- Agilent Technologies

• Sonoscan Inspection

• AOI Inspection (Orbotech)

• BGA/ CSP rework (SRT/Genrad)

• Wave soldering evaluations (Vitronics-Soltec)

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Paste Evaluation (Paste Evaluation (SolectronSolectron, Milpitas, CA), Milpitas, CA)

• Evaluate five Sn3.9Ag0.7Cu and five Sn37Pb solder pastes.Choose one SnPb and one SnAgCu paste for use on NEMIreliability test boards.

• Evaluation criteria:

• High Paste volume and good consistency of print on testboard on 16mil, 20mil QFP pads, 0402 chip pads, 1mm,1.27mm pitch BGA pads.

• Reflow with tin-lead coated components and lead-freecomponents placed on test board: visual inspection of jointsafter reflow (nitrogen atmosphere used in reflow oven). Testboard- OSP surface finish, 62mil FR4 board

• X-ray inspection: X-ray defect report for lead-free and tin-leadpaste soldered boards

• Cross-sections of selected components

• Pull tests/ Shear tests

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas){-Max{-Max Vol Vol 16mil pads: 3840Cumils} 16mil pads: 3840Cumils}

16mil pitch pad Paste Volume and Standard Deviation of Volume

0

500

1000

1500

2000

2500

3000

3500

0 1 2 3 4 5Paste Number

Pas

te V

olu

me

(Cu

mils

)

AverageVolume SnPb

Stdev SnPb

AverageVolumeSnAgCuStdev SnAgCu

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)

50mil pitch BGA Paste Volume and Standard Deviation Paste Volume

0

1000

2000

3000

4000

5000

6000

0 1 2 3 4 5Paste Number

Pas

te V

olu

me

(Cu

mils

)

AverageSnAgCu

Stdev SnAgCu

Average SnPb

Stdev SnPb

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)SnAgCuSnAgCu Paste 4 (left): Paste 4 (left): SnPbPaste SnPbPaste 5 (right) 5 (right)

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)

X-ray defect report for SnPb and SnAgCu solder pastes

0

200

400

600

800

1000

1200

1400

0 1 2 3 4 5

Paste Number

Def

ect

Nu

mb

er

Defect reportNo.SnPb

Defect reportNo.SnAgCu

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)

Summary

Print scoresX-ray scoresSolderability Total Other commentsSnPb Paste 1 6 1 2 9SnPb Paste 2 0 2 3 5SnPb Paste 3 2 2 2 6SnPb Paste 4 1 2 3 6

SnPb Paste 5 4 3 3 10

SnAgCu Paste 1 3 0 1 4 Stencil Life issueSnAgCu Paste 2 1 0 1 2SnAgCu Paste 3 2 1 1 4

SnAgCu Paste 4 4 1 1 6SnAgCu Paste 5 1 1 1 3

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)NiPdNiPd QFP QFPSnPbSnPb Paste 5 (left): Paste 5 (left): SnAgCuPaste SnAgCuPaste 4 (right) 4 (right)

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Paste Evaluation(SLR Milpitas)Pure Sn1206Paste Evaluation(SLR Milpitas)Pure Sn1206SnPbSnPb Paste 5 (left): Paste 5 (left): SnAgCuPaste SnAgCuPaste 4 (right) 4 (right)

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)

Pull force for NiPd QFP leads before and after ageing (-40°C to 125°C, 1000

cycles)

0.00.51.01.52.02.53.0

Average

Pu

ll F

orc

e (l

bs)

Sn37Pb

SnAgCu

Sn37Pb(After ATC)

SnAgCu(After ATC)

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Paste Evaluation(Paste Evaluation(SolectronSolectron Milpitas) Milpitas)

Shear force (lbs) before and after ageing(-40°C to 125°C, 1000 cycles)

for pure tin coated 1206 chip

0.0

5.0

10.0

15.0

Average

Sh

ear

Fo

rce(

lbs) Sn37Pb

SnAgCu

Sn37Pb(AfterATC)SnAgCu(AfterATC)

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NEMI Reliability Test Board Builds (UniversalNEMI Reliability Test Board Builds (UniversalInstruments SMT Lab, Binghamton, NY)Instruments SMT Lab, Binghamton, NY)

• DEK 265 Screen Printing Machine(plus SVS pasteinspection machine)

• Universal GSM placement machine

• Vitronics-Soltec reflow oven(10 zone) in Nitrogenatmosphere(<20ppm O2)

• 208CSP, 169CSP, 256PBGA, 256CerBGA,48TSSOP and 2512 resistor boards

• Lead-free Paste Component peak temperatures240-247°C(Time over 217°C: 61-90sec)

• Tin-lead Paste component peak temperatures 209-220°C(Time over 183°C: 83-88sec)

• 62 mil thick High Tg (170°C) FR4 board,Immersion Ag surface finish

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X-ray Inspection (X-ray Inspection (AgilentAgilent, Loveland, CO), Loveland, CO)

• X-ray inspection of boards (Agilent 5DX)

• Initial observations:

• Lead-free paste with tin-lead components> voidingthan

• lead-free paste with lead-free components> voidingthan

• tin-lead paste with tin-lead components

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AOI Inspection (AOI Inspection (OrbotechOrbotech, Santa Ana, CA), Santa Ana, CA)

• AOI inspection of lead-free and tin-lead TSSOP(NiPd/SnPb) and2512(Sn/Sn10Pb) resistor boards

• Evaluate and compare solder jointshape/geometry and wetting for:

• (1)Lead-free paste soldered withlead-free component

• (2) Lead-free paste soldered withtin-lead component

• (3) Tin-lead paste soldered with tin-lead component

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GenradGenrad/SRT (/SRT (WestfordWestford,MA),MA)

• Rework NEMI 208CSP(0.8mm pitch) and256PBGA(1.27mm pitch) lead-free and tin-leadboards using SRT Summit 1100HR Plus machine

• Develop BGA/CSP rework profiles for lead-freepaste with lead-free and tin-lead components andcompare with profile for tin-lead paste with tin-lead component boards

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BGA/CSP SRT/BGA/CSP SRT/GenradGenrad Rework Rework

• Additional control features were used to reworkthe SnAgCu solder alloy.

• “Positive air” feature was used to keep thetemperature of the top of the BGA to a moremodest temperature.

• Maximum BGA top surface temperature (purpleline) kept to 212°C

• while the solder joint was raised to 243°C andkept over melting point (217°C) for 74 seconds.

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SonoscanSonoscan(Elk Grove Village, IL)(Elk Grove Village, IL)

• Inspect BGA/CSP and TSSOP components pre-assembly, post-assembly and post-thermalcycling for package delamination and otheranomalies

• 208CSP and 169CSP post-assembled tin-lead andlead-free boards inspected so far: No majoranomalies

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Process TimelinesProcess Timelines

• NEMI Reliability test board builds: Complete:November 2000

• X-ray inspection: To be complete by Jan. 2001

• BGA rework evaluations: Complete by Jan/Feb.2001

• AOI inspection: Complete by Jan/Feb. 2001

• Sonoscan inspection:

• Pre-build: Completed Oct 2000

• Post-build: Complete by Jan/Feb 2001

• Post-thermal cycling: Complete by June 2001

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Wave Solder Overview (Wave Solder Overview (VitronicsVitronics--SoltecSoltec,,Binghamton, NY)Binghamton, NY)