the impact of lead-free soldering processes on defense industry electronic assembly practices

The Impact of Lead-free Soldering Processes on

Defense Industry Electronic Assembly

Practices

Dave HillmanRockwell Collins

SMTA Huntsville Chapter 2011

The goal of Today’s Presentation/Discussion: Educate – Entertain - Engage!

Impact of Lead-free Soldering Processes on Defense Industry Electronic Assembly Practices

Agenda:

• Background

• Specifications

• Lead-free Topics of Interest - in no particular order!

Graph Source: ELECTRONICS INDUSTRIES MARKET DATA UPDATE, Spring 2010

Whenever there is a challenge, there is an opportunity…………..

The Predominate Component Surface Finish Is……

Graph Courtesy of CALCE Consortium, 2009ish

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Lead-Free Transition = In

creasing Difficulty

Military and Aerospace sectors have little influence on the global transition to Lead-

Free (<1% Market Share)

Influence of Lead-free Soldering on the Defense Industry Products

Military/Aerospace Electronic Products Characterization:

• Life Critical & Flight Critical Applications• Extremely Stable Qualified Material Lists• Significant Use Life ~ 20-30 Years Not Uncommon• Manufacturing Mode: High Mix/Low Volume• Design Cycle Mode: Deliberate and Long ~ 12 Months• Customer Certification

* Nothing is set in stone – and there is no guarantee that “legacy” products will have infinite exemption or exclusion status

Graphic source: M. Kelly, SMTAI 2007, “Case Study: Qualification of a Lead-free Card Assembly &^ Test Process of a Server Complexity PCBA


Agenda:

• Background

• Specifications

• Lead-free Topics of Interest (in no particular order!

LEAP WG Actionable Deliverables

GEIA-STD-0005-1, Performance Standard for Aerospace and High Performance Electronic Systems Containing Lead-free Solder

Used by aerospace electronic system “customers” to communicate requirements to aerospace electronic system “suppliers”

GEIA-STD-0005-2, Standard for Mitigating the Effects of Tin Whiskers in Aerospace In High Performance Electronic Systems

GEIA-STD-0005-3, Performance Testing for Aerospace and High Performance Electronic Interconnects Containing Lead-Free Solder and Finishes

Used by aerospace electronic system “suppliers” to develop reliability test methods and interpret results for input to analyses

GEIA-HB-0005-1, Program Management / Systems Engineering Guidelines For Managing The Transition To Lead-Free Electronics

Used by program managers to address all issues related to lead-free electronics, e.g., logistics, warranty, design, production, contracts, procurement, etc.

GEIA-HB-0005-2, Technical Guidelines for Aerospace and High Performance Electronic Systems Containing Lead-Free Solder and Finishes

Used by aerospace electronic system “suppliers” to select and use lead-free solder alloys, other materials, and processes. It may include specific solutions, lessons learned, test results and data, etc.

GEIA-HB-0005-3, Rework and Repair Handbook for Aerospace and High Performance Electronic Systems Containing Heritage SnPb and Lead-Free Solder and Finishes

GEIA-HB-0005-4, Impact of Lead Free Solder on Aerospace Electronic System Reliability and Safety AnalysisUsed to determine, quantitatively if possible, impact of lead-free electronics on system safety and certification analyses, using results from tests performed per GEIA-STD-0005-3

GEIA-STD-0005-1, Performance Standard for Aerospace and High Performance Electronic Systems Containing Lead-free Solder (Published)

*Used by aerospace electronic system “customers” to communicate requirements to aerospace electronic system “suppliers” – Lead-free Control Plan


GEIA-STD-0005-2, Standard for Mitigating the Effects of Tin Whiskers in Aerospace In High Performance Electronic Systems (Published)

*Tin Whisker Protocols and Procedures


GEIA-HB-0005-2, Technical Guidelines for Aerospace and High Performance Electronic Systems Containing Lead-Free Solder and Finishes

* Used by aerospace electronic system “suppliers” to select and use lead-free solder alloys, other materials, and processes.

200 cycles: SnPb (left) and SAC (right)


Project documents, test plans, test reports and other associated information will be available on the web:

NASA-DoD Lead-Free Electronics Project:

http://www.teerm.nasa.gov/projects/NASA_DODLeadFreeElectronics_Proj2.html

Joint Test Protocol

Project Plan

Final Test Reports

Super Resource

Influence of Lead-free Soldering on the Defense Industry Products:The Basis for Understanding Lead-free Soldering – The “One” Cell


Agenda:

• Background

• Specifications

• Lead-free Topics of Interest

(In No Specific Order!)

Influence of Lead-free Soldering on the Defense Industry Products: Process Robustness: Alloy Proliferation

Graph Source: W. Liu and N. C. Lee, “Novel Sacx Solders with Superior Drop Test Performance”, SMTAI 2006

Influence of Lead-free Soldering on the Defense Industry Products: Process Robustness: Alloy Proliferation

Graph Source: G. Henshall et al, “iNEMI Pb-Free Alloy Proliferation Project” SMTAI 2008.

The Material Engineers are still playing in the sandbox………

Influence of Lead-free Soldering on the Defense Industry Products: Process Robustness

Graphic Source: The Lead Free Electronics Manhattan Project – Phase I, Contract # N00014-08-D-0758


Photos Courtesy of Celestica


Left Photos courtesy of NPL/Bob Willis

Equipment Issues - Wave Solder• Molten Tin is Corrosive!

(Photo Sources:“Lead-Free Technology and the Necessary Changes in Soldering Process and Machine Technology”, H. Schlessmann, APEX 2002 Conference Proceedings and “Real Life Tin-Silver-Copper Alloy Processing”, A. Rae et al, APEX Conference Proceedings, 2003

Corroded Solderpot Hardware Corroded Wave Solder Impeller


Equipment Issues - Soldering Irons

(Photos “Under The Plating”, American Hakko Products Technical Report, July 2002)

18,000 Soldering Hits!

(Sn63 Solder Alloy !)


• Equipment Issues - Soldering Irons

• Available Temperatures Ranges Seem Useable

• Tip Maintenance Becomes More Critical

• Use of Hot Air Systems Gaining Ground

(Graph Source: “Dissolution rates of iron plating on soldering iron tips in molten lead-free solders”, Takemoto et al, Soldering & Surface Mount Technology, Vol. 16, No. 3, 2004


Influence of Lead-free Soldering on the Defense Industry Products: Mixed Metallurgy

Test Results: Solder Joint Failure @ 137 Cycles for SAC BGA in SnPb Reflow Process


Large AgSn Platelets

Influence of Lead-free Soldering on the Defense Industry Products: Mixed Metallurgy – New Physics ???


Pb PhasePb Phase

SAC BGA Reworked with SAC Solder Paste, Original Solder Joint was SnPb, Magnified View of Crack with Pb Phase Present- Failed after 822 Thermal Cycles

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WeibullSnAgCuBi/SnCu

W2 RRX - SRM MED

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SnAgCuBi/SnPb

W2 RRX - SRM MED

F=25 / S=0

Key: Solder Alloy/Component Finish

Mixed Metallurgy• Interaction of lead and bismuth in a bismuth containing LF solder

alloy: Joint Council on Aging Aircraft (JCAA)/ Joint Group on Pollution Prevention (JGPP) LF Solder program.

• Solder Alloy Included in Test Program:

– Sn3.4Ag1.0Cu3.3BiWith SnCu and SnPbTSOP Component

– Weblink:http://acqp2.nasa.gov/JTR.htm)

What is HOP – incomplete coalescence of the BGA solderball and the solder paste deposit

Head On Pillow (HOP)

Head On Pillow (HOP)Graph Source: P. Su, “Effects Of Component Warpage On Board Assembly Defects And Effective Mitigation Measures”, SMTAI 2010

Graph Source: P. Su, “Effects Of Component Warpage On Board Assembly Defects And Effective Mitigation Measures”, SMTAI 2010


Head On Pillow (HOP) – Component Warpage

Incorrect Solder Paste Deposit


Head On Pillow (HOP) – Incorrect Reflow

Pad Cratering

Graphic Courtesy of B. Roggeman, Unovis Consortium

Pad Cratering

Fillet Lifting and Shrinkage Voids

Fillet Lifting and Shrinkage Voids Are An Inspection Issue, Not A Reliability Issue

• Conformal Coating– Silicone

Conformal Coat Photo Shown Here.

– NOT a Cure-All, Lower Risk.

– Conformal Coating Only Captures and Does Not Eliminate.

Tin Whiskers

Photo Courtesy of Bob Ogden

Tin Whiskers

Chart Courtesy of Dr. Tom Woodrow, “CALCE Part Reprocessing, Tin Whisker Mitigation and Assembly Rework Symposium”, 2008

• Conformal Coating Thickness Plays a Role

• Have You Characterized Your Coverage Consistency?

• References You Should Read:• 2010 CALCE 4th Tin Whisker Symposium, Hunt/Wickham

Tin Whiskers

• Soldering Process– Assembly

Processes Will Cover Pure Tin on Small Parts with Solder

– There Are Geometry Limitations Dependent on Component Construction

– Where Is Your Process Data???

Tin Whiskers

The Concept of a System of Risk Mitigation

Chart Courtesy of CALCE Consortium

An Example:

• Automotive Industry segment: Unintended Consequences of Pure Tin Surface Finishes

Photo Source: NASA Engineering and Safety Center Technical Assessment Report, TI-10-00618, “Technical Support to the National Highway Traffic Safety Administration (NHTSA) on the Reported Toyota Motor Corporation (TMC) Unintended Acceleration (UA) Investigation”, January, 2011.

Rules Of a Tin Whisker Mitigation Plan

Graphic Courtesy of D. Pinsky, Reference: “Controlling Tin Whisker Risk: Implementation of Appropriate Mitigations”, IPC Tin Whisker Conference 2010

(Data courtesy of Nihon Superior/K. Sweatman

Influence of Lead-free Soldering on the Defense Industry Products: Copper Dissolution

ENIG – 1.5mil Copper – 60 Sec ImSn – 1.5mil Copper – 60 Sec

Influence of Lead-free Soldering on the Defense Industry Products:Copper Dissolution

Impact of Lead-free Soldering Processes on Defense Industry Electronic Assembly Practices: Conclusions

* The implementation of lead-free soldering technology is achievable if conducted in a measured, controlled, methodical manner.

* We need significant coordination and collaboration within the military/aerospace industry segment to avoid non-value added efforts

Questions ?

the impact of lead-free soldering processes on defense industry electronic assembly practices

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