Lead-Free Soldering

Lead-Free Soldering



The past few years have seen major developments in soldering materials and processes for electronics assembly manufacture due to the movement from tin-lead to lead-free soldering. The removal of lead from electronics solders due to environmental considerations first developed with proposed US legislation in the early 1990s. At that time, the alternatives had not been fully explored, so a ban on the use of lead in electronic solders was put on hold. However the seed was sown for development with various projects initiated during the 1990s in Europe, the Americas, and Asia. Based on government pressures, Japan OEMs began to move to lead-free solder products from 1998 and this, combined with the European Union ROHS (Restriction of Hazardous Substances) legislation enacted in 2006, drove the global manufacture of electronics consumer products with le- free solders. From 1998 to the present, the development of lead-free solder materials and processes has progressed to such an extent that development work moving forward will typically only concentrate on lead-free solders and components rather than tin-lead solders and components. This book aims to give the latest information on development of the lead-free soldering materials and processes and identify where more work is needed. The chapters of the book describe legislation, alloys, reflow, wave, rework, reliability, backward and forward process compatibility, PCB surface finishes and PCB laminates, and standards affecting the general lead-free soldering arena.



Published by
Published 26 June 2007
Reads 5
EAN13 9780387684222
License: All rights reserved
Language English
Table of Contents
Preface List of Authors Introduction
Chapter 1: Lead Restrictions and Other Regulatory Influences on the Electronics Industry 1.1Introduction 1.2A Regulatory Tour of Europe 1.3A Regulatory Tour of Asia 1.4Regulatory Tour of the Americas 1.5Business Impacts and Conclusions Chapter 2: Fundamental Properties of Pb-Free Solder Alloys 2.1 Search for a Pb-Free Alternative to Sn-Pb Eutectic 2.2 Primary Alloy Design Criteria 2.3 Solder Alloy Solidification and Microstructural Development 2.4 Melting Behavior 2.5 Solidification Behavior 2.6 Wetting and Solderability 2.7 Pb-Free Solder Mechanical Behavior and Solder Joint Reliability Chapter 3: Lead-Free Surface Mount Assembly 3.1Introduction 3.2Solder Paste Alloy 3.3Screen Printing Process 3.4Component Placement 3.5Reflow Soldering 3.6Solder Joint Inspection and Acceptance Criteria Chapter 4: Lead-Free Wave Soldering 4.1Introduction
v xi 1
5 5 6 14 16 17 21 21 21
25 25 44 58
62 75 75 75 76 77 78 82 91 91
viii Table of Contents
4.2Lead-Free Wave Solder Alloy Alternatives 4.3Wave Solder Equipment Recommendations 4.4Process Recommendations 4.5Solder Joint Characterization 4.6Design Considerations Chapter 5: Lead-Free Rework 5.1Introduction 5.2Lead-Free Hand Soldering SMT Rework 5.3Lead-Free SMT Rework of BGA/CSP Soldered Joints
92 94 98 102 110 117 117 117 124 5.4Lead-Free Pin-Through-Hole (PTH) Hand Solder Rework 135 5.5Lead-Free Pin-Through-Hole Mini-Pot Rework Soldering 138 145 145 146 153 173 173 177 182 187 190 192 199 199 200 202 206 209 212 221 221 222 271 271 271
Chapter 6: Lead-Free Solder Joint Reliability 6.1Introduction 6.2General Trends 6.3SAC Solder Joint Reliability Case Study Chapter 7: Backward and Forward Compatibility 7.1Introduction 7.2Reliability of BGA/CSP Backward Compatibility 7.3Estimation of Mixed Composition Liquidus Temperature 7.4Chip Component and Lead-Frame-Component Backward Compatibility 7.5Forward Compatibility 7.6Press Fit Connector Interconnections Chapter 8: PCB Laminates 8.1Introduction 8.2Types of Stress in Printed Wiring Boards 8.3Laminate Material Test Methods 8.4Accelerated Thermal Stress Testing 8.5Accelerated Thermal Stress Test Methods 8.6HATS Test Methods – A Case Study Chapter 9: Lead-Free Board Surface Finishes 9.1Introduction 9.2Process Overview Chapter 10: Lead-Free Soldering Standards 10.1Introduction 10.2IPC and JEDEC Standards
10.3IEC Standards 10.4Japan (JEITA) Standards 10.5Other Standards Conclusions Index
Table of Contents ix
279 280 281 285 291