Environment-friendly electronics: lead free technology
Dr Jennie S HwangPublished by Electrochemical Publications, Port Erin, Isle of Man, British Isles, IM99 8HDTel: 01624 834941 Fax 01624 835400,URL: http://www.elchempub.com,email: info@elchempub.com31 chapters, 879 pages, 586 figures,182 tables,ISBN 0 901150 40 1Price £119, US$238
Keywords: Environment, electronics, environmentally friendly lead-free solder
Although the toxicity of lead has been known for many years and programmes to remove it from everyday products such as petrol and paints have been largely successful, its use in electronics has continued unabated until very recently. Lead is a key component in the solders used in electronics assembly and it imparts numerous favourable attributes to these materials - lead based solders have played their part in enabling the proliferation of electronics in all walks of life. However, in recent years, there has been growing concern about the impact of end-of-life electronics on our environment and this has lead to new regulations and legislation that are beginning to have a major influence on the electronics industry as we know it.
One draft piece of legislation in particular has perhaps done more to seal the fate of lead in electronics than any other and this is the now notorious WEEE (Waste from Electrical and Electronic Equipment) directive. This draft directive first appeared several years ago and has gone through many iterations in an attempt to define a piece of legislation that will encourage the recycling and reuse of end-of-life electronics. Whilst no one would object to the adoption of such laudable aims, the early drafts of this directive also sought to proscribe the use of various familiar and useful substances, one of which was lead. Although the WEEE directive has moved on and the lead ban is now covered by another directive, this single piece of draft legislation effectively initiated the end of the use of lead in electronics assembly.
Once the world began to understand the ramifications of this legislation, the search was on for suitable viable alternatives. Some people initially protested that it was not possible to replace lead in solders and that there was no sensible, logical reason to do so, but the industry soon became intimately involved with the assessment of many alloys featuring a wide range of exotic and not so exotic elements. Although lead itself will not be banned in solders until 2006 or possibly later, the global electronics industry is already making the transition. Japanese companies have been leading the way, largely for commercial reasons and the rest of the world is not far behind.
In the midst of all this frenetic activity we come to the subject of the review, the almost 900 page book by Dr Jennie Hwang on lead-free technology. This huge work is the first to tackle the subject on such a large scale and in so much detail. The topic is an increasingly complex one with a proliferation of sometimes conflicting data and there is the very real danger of information overload. The author is therefore to be commended for undertaking the task of pulling the information available into a coherent single source that will provide a useful reference work for anyone involved in lead-free.
At a first glance a technical book of this nature with 879 pages may appear to represent a daunting task for even the most dedicated reader. However, Dr Hwang is conveniently broken it into 31 chapters that take us logically through various aspects of the subject. The book begins with three chapters that provide a solid introduction covering the purpose of the work, industry trends and an overview of the legislation and environmental issues that have initiated the move away from lead. These are followed by a chapter detailing the fundamental technology of soldering with particular reference to established conventional lead containing solders. This gives a good overview of the important subject areas that need to be considered and evaluated whether the solder to be used is lead based or lead-free and it provides a useful entree for what follows. However, before moving on to the series of chapters covering lead- free solders in detail, there is a chapter listing the patents covering the fifty or so lead-free solder compositions. Whilst this chapter is very useful in helping the reader to understand what material choices may be made, my preference would have been to place this chapter at the end of the book. Once this chapter has been passed there follow thirteen chapters covering the main alloy systems that have been proposed as alternatives to conventional tin-lead and clear comparisons with the existing technology are made, so that the implications of using each alternative can be readily understood. This series of chapters begins with the binary systems and progresses through the ternary and quaternary systems to the more complex multielement systems. The section then concludes with a chapter on the low and high temperature solders.
Having given the reader a detailed exposition covering all the major solder systems, Dr Hwang then uses the remaining chapters to cover many of the important issues that relate to the use and implementation of lead-free technology. There are chapters covering component and board finishes,reliability, application considerations and even the design of experiments for evaluating lead- free solders. And that is not all! There are still more chapters giving much additional useful information. For example, despite the main focus being on lead-free solders, a chapter is dedicated to the conductive adhesives that offer another alternative to solders for certain applications. This book certainly offers a 'one stop shop' for anyone seeking a detailed appraisal of lead-free technology.
So are there negatives with this book? Certainly, from a personal perspective, it is easy to say that one might have approached a work of this type in a different way, but in reality how many people would have had the time,expertise and commitment to undertake such a mammoth task? In that context, any minor criticisms seem almost churlish. However, as it is the task of the reviewer to give a balanced appraisal, I will briefly mention a few points that may be of interest. Firstly, the title really doesn't do justice to the content of the book, something more focussed would have better indicated that this book is mainly about lead-free solders. Secondly, I would like to have seen more information on the practicality and difficulties of moving to lead- free assembly. One of the key concerns that many people have raised with me relates to the issues around practical implementation of lead-free technology and the additional measures that must be taken to enable successful conversion of equipment and processes without compromising productivity, yields and reliability. Thirdly, the world of lead-free technology is changing rapidly and the amount of data available continues to grow. A book of this type can only hope to represent the situation at the time of writing and it is quite likely that some chapters of the book will need revising in the future in the light of new experiences. Finally, I also have to say that in some of the chapters the style of writing gives one the distinct impression that quantity comes second to quality. Nevertheless, these are minor quibbles and it is difficult, for example, to see how much more information could be included without having to divide the book into two or more volumes.
Dr Hwang is an established expert in this area and she has authored many publications and patents during her career. Although she has clearly contributed the majority of this book, she has also called on other experts to make significant additional contributions to the book. The use of these additional inputs strengthens the overall message conveyed by the book and helps to emphasise the importance and magnitude of the task industry faces in moving to lead-free. The book itself is published to the usual high standards expected from Electrochemical Publications, with good quality paper and printing. In fact, at the price of £119 this book, with nearly 900 pages, represents something of a bargain. For anyone even remotely involved with electronics assembly, the move to lead-free technology is a subject that cannot be ignored. This book provides a valuable source of useful information on most of the key aspects of this new technology and Dr Hwang and the other contributors are to be congratulated for the huge amount of work they have undoubtedly undertaken to produce this excellent tome. I can wholeheartedly recommend it as a valuable reference work.
Martin GooseyShipley Europe Ltd, Coventry, UKMarch 2002
