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Lead-Free Solder Process Development

Greg Henshall (Editor), Jasbir Bath (Editor), Carol A. Handwerker (Editor)
ISBN: 978-1-118-10274-9
284 pages
March 2011, Wiley-IEEE Press
Lead-Free Solder Process Development (1118102746) cover image
"Lead-free Solder Process Development," covers a list of key topics including: legislation, soldering fluxes, SMT, wave, rework, alloys, component finishes, reliability, EDXRF, and standards. It is intended as a reference guide to engineers in the industry who are or who will be migrating to lead-free soldering. It is not intended to be an exhaustive review of the literature but to be a practical reference guide for selected, key subject areas. Each subject area is discussed by those who have conducted work in the field and can provide insight into what are the most important areas to consider. The book gives updates in areas for which research is ongoing, and addresses new topics which are relevant to lead-free soldering.

A practicing engineer will find the book of use as it goes into these topics in sufficient detail to make it informative and a good practical guide to address issues of concern in these areas. Chapters on Soldering Fluxes, Component Finishes, Alloys, EDXRF and certain areas on reliability have not been covered in sufficient detail in previous books, so the proposed book will be a timely reference for engineers in the field. The lead-free solder process window has been found to be smaller than for tin-lead, so a specific chapter is dedicated to Six Sigma process methodologies to help engineers approach lead-free soldering processes with better evaluation and process methodologies.

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Technical Reviewers.




1. Regulatory and Voluntary Drivers for Environmental Improvement: Hazardous Substances, Lifecycle Design and End of Life (John Hawley).

1.1 Introduction.

1.2 Substances of Environmental Concern.

1.3 Design for Environment/Energy Efficiency.

1.4 Recycling and Take-back.

1.5 Summary.

1.6 References.

2. Lead-free Surface Mount Technology (Jasbir Bath, Jennifer Nguyen and Sundar Sethuraman).

2.1 Introduction.

2.2 No-clean and Water-soluble Lead-free Pastes.

2.3 Solder Paste Handling.

2.4 Board and Stencil Design.

2.5 Screen Printing and Printability of Lead-free Solder Pastes.

2.6 Paste inspection.

2.7 Component Placement (Paste Tackiness).

2.8 Reflow Soldering and the Reflow Profile.

2.9 Effect of Nitrogen versus Air Atmosphere during Lead-free Reflow.

2.10 Head-in-Pillow Component Soldering Defect.

2.11 Solder Joint Visual Inspection.

2.12 AOI (Automated Optical Inspection).

2.13 X-ray Inspection.

2.14 ICT/Functional Testing.

2.15 Conclusions.

2.16 Future Work.

2.17 Acknowledgements.

2.18 References.

3. Lead-free Wave Soldering (Dennis Barbini and Jasbir Bath).

3.0 Introduction.

3.1 Wave soldering process boundaries.

3.2 Soldering temperatures on the chip and main soldering waves.

3.3 Alloys for Lead-free Wave Soldering.

3.4 The function of nitrogen in wave soldering.

3.5 The effect of PCB Design on wave solder joint formation.

3.6 Standards related to wave soldering.

3.7 Conclusions.

3.8 Future work.

3.9 Acknowledgements.

3.10 References.

4. Lead-free Rework (Alan Donaldson).

4.1 Introduction.

4.2 Surface Mount Technology (SMT) Hand Soldering/Touch-up.

4.3 BGA/CSP Rework.

4.4 BGA Socket Rework.

4.5 X-ray.

4.6 Through-hole Hand Soldering Rework.

4.7 Through-hole Mini-pot/Solder Fountain Rework.

4.8 Best Practices and Rework Equipment Calibrations.

4.9 Conclusions.

4.10 Future Work.

4.11 References.

5 Lead-Free Alloys for BGA/CSP Components (Gregory A. Henshall).

5.1 Introduction.

5.2 Overview of New Lead-Free Alloys.

5.3 Benefits of New Alloys for BGAs and CSPs.

5.4 Technical Concerns .

5.5 Management of New Alloys.

5.6 Future Work.

5.7 Summary and Conclusions.

5.8 Acknowledgements.

5.9 References.

6 Growth Mechanisms and Mitigation Strategies of Tin Whisker Growth (Peng Su).

6.1 Introduction.

6.2 Role of stress in whisker growth.

6.3 Understanding standard acceleration tests.

6.4 Plating process optimization and other mitigation strategies.

6.5 Whisker growth on board-mounted components.

6.6 Summary.

6.7 References.

7. Testability of Lead-Free Printed Circuit Assemblies (Rosa D.Reinosa and Aileen M. Allen).

7.1 Introduction.

7.2 Contact Repeatability of Lead-Free Boards.

7.3 Probe Wear and Contamination.

7.4 Board Flexure.

7.5 Conclusions.

7.6 Acknowledgments.

7.7 References.

8. Board-Level Solder Joint Reliability of High Performance Computers under Mechanical Loading (Keith Newman).

8.1 Introduction.

8.2 Establishing PWB Strain Limits for Manufacturing.

8.3. SMT Component Fracture Strength Characterization.

8.4 PWB Fracture Strength Characterization.

8.5 PWB Strain Characterization.

8.6. Solder Joint Fracture Prediction – Modeling.

8.7. Fracture Strength Optimization.

8.8 Conclusions.

8.9 Acknowledgments.

8.10 References.

9. Lead-Free Reliability in Aerospace/Military Environments (Thomas A. Woodrow and Jasbir Bath).

9.1 Introduction.

9.2 Aerospace/Military Consortia.

9.3 Lead-Free Control Plans for Aerospace/Military Electronics.

9.4 Aerospace/Military Lead-Free Reliability Concerns.

9.5 Summary and Conclusions.

9.6 References.

10. Lead-Free Reliability in Automotive Environments (Richard D. Parke).

10.1 Introduction to Electronics in Automotive Environments.

10.2 Performance Risks and Issues.

10.3 Legislation Driving Lead-Free Automotive Electronics.

10.4 Reliability Requirements for Automotive Environments.

10.5 Failure Modes of Lead-free Joints.

10.6 Impact to Lead-free Component Procurement and Management.

10.7 Change versus Risks.

10.8 Summary and Conclusions.



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GREGORY HENSHALL is Master Engineer at Hewlett-Packard Company in Palo Alto, California. He has more than twenty years' experience in materials research and development, including twelve years of experience with soldering alloys and electronics manufacturing and nine years focused on lead-free technology. Dr. Henshall currently serves as chair for the iNEMI (International Electronics Manufacturing Initiative) Lead-Free Alloy Alternatives Project.

JASBIR BATH is the owner of Bath Technical Consultancy LLC in Fremont, California. He has over fifteen years' experience in research, design, development, and implementation in the areas of soldering, surface mount, and packaging technologies working for companies including Flextronics International/Solectron Corporation and ITRI (International Tin Research Institute). Bath has been chair of various iNEMI lead-free consortia involving OEMs, EMS, and component and material supplier companies on alloy selection, assembly, and rework.

CAROL A. HANDWERKER is the Reinhardt Schuhmann Jr. Professor of Materials Engineering at Purdue University, Indiana. Previously, she was chief of the Metallurgy Division at the National Institute of Standards and Technology (NIST), where she participated in the NCMS (National Center for Manufacturing Sciences) Lead-Free Solder Project and co-chaired the iNEMI Lead-Free Alloy Selection Team. Dr. Handwerker is currently active on the iNEMI Technical, Research, and Environmental Leadership Steering Committees, as well as a participant in a range of iNEMI project teams.

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