Lead-Fee Soldering in Electronics—Science, Technology and Environmental Impact Print E-mail
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Written by Bob Willis   
Thursday, 13 May 2004 19:00

ImageEdited by Katsuaki Suganuma
11 chapters, 342 pages with photographs, tables and diagrams
ISBN 08247 4102 1

Here is another multi author textbook to hit the streets on lead-free, surely more will follow in the coming months as we move closer to July 2006. Katsuaki is the author of other titles like Lead-Free Handbook and I believe a Hand Soldering Guide which has only been circulated in Japan, hence Japanese only. He is based in Osaka University and I had the pleasure of meeting him in Japan with the SMART Group Mission. He was also the engineer to do some of the first work on fillet lifting on through hole lead-free joints. I have featured his first text book in past review pages, a limited review as the text was in Japanese, now as promised is this new book.

Authors contributing to the book include Kay Nimmo, Bill Plumbridge, Carol Handwerker, Tetsuro Nishimura and Masao Hirano amongst others. There is a nice section on tin whiskers which I found very interesting, like most people the subject has been done to death so it's good to see a different approach. Yun Zhang covers the topic in relatively simple terms and describes a variety of process experiments. His final conclusions are there are still many unknowns, a solution can work for one application but end up not working for others. It was also interesting the coverage given to the application of whiskers on demand.

Carol Handwerker from NIST covers material science; our own Kay Nimmo and Bill Plumbridge cover alloy selection and material performance. All of which are fundamental in understanding and comparing what we know about tin/lead solders and what we don't about lead-free. Each will have spent many hours producing the material and researching different data sets that exist.

One chapter is written by Shinichi Fujiuchi who represents one of the larger contract manufacturers in the world, Sanmina - SCI. Shinichi outlines the reflow assembly process including solder paste performance. An interesting topic that this reviewer was not aware was the reason that solder paste with zinc print wonderfully well for a short period of time then turn to a block of concrete. Apparently the zinc reaction products degrade the flux and other elements in the vehicle increasing the viscosity. One supplier has been investigating a coating process to reduce this effect, another application for OSP coatings?

Shinichi also covers a new solderability test procedure for components using solder paste in conjunction with a wetting balance. The technique is used to more closely mimic the process used in production. It will be interesting to see if solderability test equipment suppliers like Concoat look at this test procedure in the future as an option to the solder globule. It was a little disappointing that the reflow process was not covered in much detail with most attention paid to the materials.

The book again guides the user to the inevitable choice of tin/silver/copper as the lead-free alternative but with the use of tin/copper family for wave soldering and manual assembly based on cost. I guess my criticism with the book is the translation in a couple of chapters, which makes it difficult to follow the flow, but still worthy of review.


 

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