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Get SMART: Tin Whiskers Eliminated!
Thursday, September 09, 2010 | John Burke, RoHSUSA.com

John Burke.jpgEarlier I promised to bring you details of current trends of the various discussion groups in the industry. I had no idea at the time that one of the greatest breakthroughs in electronics manufacturing technology since the European introduction of RoHS would come from people on my own tin whisker mail forum that are actively involved in the research and "search for a cure" in the area of tin whiskers would be the major focus of my next article.

Since before the introduction of RoHS in 2006, the industry has been searching for answers on preventing tin whisker formation on electronics assemblies. There seemed to be no way to prevent them; the best that could be hoped for was to "mitigate" the risk with a variety of means, only a few of which were available to the actual users of the components.

The problem was around before the legislation was put into place, and NASA for years has had an excellent Web site up and running with many examples and case studies of the phenomenon. Tin plating of components had of course been around for many years before the RoHS legislation impacted the global electronics community, but the switch to tin as a solderable finish for over 85% of all components, particularly fine-pitch applications, raised the risk probability of failures due to tin whisker shorting.

The real impact on the high reliability electronics manufacturing industry was not fully realized until it became apparent that in the case of Sn/Pb terminated components, the entire component industry switched to alternate plating materials--mostly tin plating and halted production of the historic Sn/Pb terminated components. In retrospect this was bound to happen given that most electronics components are NOT used in high-reliability devices, and given the cost of running two lines of inventory for tin/lead and non-tin/lead product lines.

Since the switch from tin lead as a component termination finish, many companies have set up as new ventures or existing companies are seeing a much increased volume of business in the area of converting SAC alloy-terminated and tin-terminated components back to a tin/lead finish for reliability purposes in specific market areas.

Most telling in the area of reliability impact is the exemption in the original RoHS legislation for the use of tin/lead in telecommunications equipment which lead to the terminology RoHS5 and RoHS6 to distinguish between the assemblies using the telecommunications Pb exemption (RoHS5) and those not using it and complying to the RoHS Pb limits for homogenous compounds (RoHS6).

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