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Previous chapters of this book have discussed the wetting behavior of near-eutectic Sn-Pb solders. These alloys are the most common in electronic applications and are deserving of the greatest attention. However, there are many applications where the properties of these alloys can be improved. A composite solder, or a solder that contains second-phase dispersions of particles, could improve solder joint properties. The area where composite solders could have the greatest impact is in improving the mechanical properties of the joint. However, the wetting behavior of the solder cannot be compromised for the sake of the mechanical properties -good wetting behavior is a necessity. Therefore, for a composite solder to be useful for electronic packaging applications mechanical properties, wetting and manufacturability must be optimized.

The challenge of keeping pace with emerging microelectronic device technologies has become increasingly difficult, and the fundamental limits of existing printed wiring board (PWB) technologies are becoming increasingly apparent. As a result, the domestic PWB industry now faces serious foreign competition from large, well-financed firms. The 1990 worldwide market for PWBs was $25.2 billion and has grown by just under 10% per year since 1988. North America’s demand is 28.5%, Japan’s is 27.6%, and Europe’s is 20.7%. The market is expected to grow to over $35 billion in 1993. The PWB industry in the U.S. consists of approximately 930 large companies. Of those, 600 have revenues of less than $5M/ year and 200 have revenues of between $5M and $25M/year. PWB technology is now approaching limitations that will have a profound effect on the ability to provide a means of utilizing the ever-increasing functionality that integrated circuits possess and promise. In addition, these limitations and increasing foreign competition will force many U.S. PWB companies out of business. One of the limiting processes referred to above is the age-old method of soldering.

Although solder technology’s roots are buried in antiquity, solder processing innovations are occurring at a faster pace than at any time in history. There are three primary drivers for this: rapidly changing design requirements, increasingly stringent process and product reliability requirements, and environmental issues. Improving solder processes to meet the needs of electronic manufacturing, while addressing a heightened awareness of environmental issues, including compliance to governmental regulations, is a great challenge to technologists supporting solder processes and will require the best efforts of multidisciplinary teams.