Contents


Preface

This book deals with some of the most advanced research observations and their applications in electronic device manufacturing in a very concise and structured way. It will help readers to gain in-depth knowledge about lead-free solder and its significance. Generally, the electronics world has been shifting towards lead-free electronic devices because of strict rules, government legislation, and serious health

and environmental issues arising out of the use of lead in electronic devices.

the electronics world recently.

materials development.

It is now a great challenge for academia and industry to study and analyze lead-free solder joints and to recommend the manufacturing of reliable lead-free electronic devices. Moreover, the task becomes more complicated when miniaturization hit

All five chapters were written by acclaimed researchers from all over the world describing detailed and necessary facts and figures on all aspects and scopes of lead-free soldering, its application, and the immense possibilities of advanced

*Chapter 1* gives a general overview and discusses the need for lead-free solder research. It also proposes some of the very recent observations towards achieving reliable lead-free solder joints. Kar et al. observe very interesting effects of using multilayers of Sn for controlling intermetallic compounds growth at the lead-free solder join interface. *Chapter 2* describes the importance of intermetallics in leadbased and Pb-free solder alloys starting from their formation, characteristics, and effects on material joints. Since the growth of intermetallics over time is determined by solid-state diffusion rules and varies from system to system, readers will get a broad overview of the interaction of intermetallics with substrates and will be able to determine the exact effect on solder properties. The chapter explains how the mechanical properties and growth kinetics of intermetallics at the solder joint interface can be altered by the addition of rare earth elements. *Chapter 3* discusses the soldering of metallic and ceramic materials by lead-free active Sn and Bi-Inbased solders. Readers will gain detailed knowledge of the possibilities of soldering ceramic materials, which is limited due to the poor wettability of ceramic substrates with commercial solders at classical soldering technologies because of the different thermal expansions of soldered materials. This chapter describes how the technology of soldering with active solders is selected for joining ceramic materials along with applications of ultrasound for mechanical activation of solders, which disrupts the surface oxides, changes the surface energy of ceramic materials, and supports the diffusion processes in the interface. *Chapter 4* explains the room temperature formation of intermixing layers between a Cu/glass stack. For fabricating highly reliable Cu/glass structures, atomically scaled interface bonding is currently necessary. This chapter describes how these nanoscale ZnO adhesion layers are prepared and used for reducing the processing temperature so that it does not affect the packaging technologies. *Chapter 5* discusses ways of improving lead-free micronsized solder joint cracks. These can be used in flex-on-board interconnections, which have become very popular in mobile electronics applications. However, crack formation within these micron-sized solder joints remains a major problem, which
