IC Component Sockets
IC Component Sockets
Weifeng Liu and Michael PechtWiley Interscience216 pp.;12 chapters with illustrations and photographs
Keywords: Electronic engineering, Books
As the authors suggest this is one of the first books dealing solely with socketing technology (Plate 4). It's amazing the science in socket design that some engineers take for granted. In many applications sockets are a necessity although, for cost reasons, many designers want to avoid their use. By reading this text the correct socket type, lead form and product can be selected.
Plate 4 Liu and Pecht have written one of the first books to deal solely with socketing technology
The first chapter deals with the types of sockets, their function and the market share by type. Interesting to note that in 1999 the sale of sockets was$960 million. In 2001 the sale of PGA sockets increased to $652 million with a projection of a fivefold increase in the demand for LGA sockets. The bulk of sales are in the US, but with a growing demand in China.
Chapters 2 and 3 deal with the contact properties, contact force and contact resistance. Explanation of the surface contact and the impact it has on pin insertion force and current carrying capability are discussed. With the move to lead-free a little more discussion on the solder finish and body moulding would have been useful. With the increasing interest in through hole reflow the issues of body compatibility with reflow could have been discussed. In addition it would have been interesting to illustrate the type of problems that can be seen during incorrect socket usage. Problems like body distortion; socket pin float;wetting of the contact and pin; and flux contamination could have been included. The problems of poor contact design on BGA sockets could have been illustrated. BGA ball damage on standard and burn-in sockets would have been an area of interest to discuss.
The issues associated with tin whisker growth is discussed. This has become a major point of discussion due to the introduction of lead-free. Tin is one of the favoured finishes in the industry due to its cost and ease of use. There are tests for whisker growth and many recommendations on the elimination of the problem, but tin whiskers still grow.
Chapter 9 provides a good introduction to some of the failure modes and this features the different corrosion mechanisms like oxidisation, pore, creep,stress and galvanic corrosion. Some of the common finishes associated with lead-free are discussed in this chapter and it is interesting to see the comparisons on different contact plating options. Generally most engineers only seem concerned with the plating on the solder contact rather than the electrical interfaces. Engineers should remember that meeting the requirements of WEEE and RoHs must consider the complete socket which includes the contact, body, pin and plated surfaces.
The final chapter provides a full listing of standards and specifications for sockets and related topics. Appendix A features a terms and definitions section and a very useful list of socket suppliers and contacts for future reference.
