Japanese firm says new additive limits tin whiskers

December 5, 2007 – C. Uyemura & Co., an Osaka-based supplier of metal plating chemicals, has developed an additive that prevents formation of “tin whiskers” on circuit boards and other electronic components, according to the Nikkei Business Daily.

Circuit boards historically have been plated with tin-lead plated finish to prevent oxidation and improve soldering, but the switch to tin plating has exacerbated the problem of “tin whiskers,” needle-like crystals of metal that can grow spontaneously on tin-finished surfaces, potentially causing current leakage and shorting due to bridges. Using materials other than tin-silver for plating avoids the problem, but these materials can be up to twice as expensive.

The company says its new additive, “GRX-70,” a mix of surfactants and organic compounds, doesn’t entirely eliminate the tin whiskers, but it does help limit their length to just 3-5 microns, or half the usual size, the paper notes. The smaller, evenly sized crystals better distribute the force of expansion that occurs at the interface between a component’s tin plating and copper wiring, the force behind whisker growth.

Samples of the additive are now being sold at roughly 2000 yen/liter (~US $18).


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