When 3:30 PM - 5:00 PM Nov 06, 2009
Where 1670 CSE
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Whisker Growth in Lead-Free Electronic Components


William Boettinger, NIST

The conversion to Pb-free solders in the electronics industry presents significant challenges to the materials community. One challenge involves finding a nontoxic, affordable and manufacturable solder finish on electronic components that maintain solderability during storage. The co-electrodeposition of ~3% Pb with Sn has been used for 40 years to prevent Sn whisker growth from solder finishes, yet no substitute has been found. Sn whiskers are single crystals that grow from their base from electrodeposits in response to compressive residual stress. They are ~ 3 um in diameter and have lengths up to 10 mm. Whiskers present an electrical shorting risk for high reliability electronics used in military, space, nuclear and medical devices.

We report efforts to understand this phenomenon as well as the more benign phenomenon of hillock growth so that mitigation strategies can be suggested: 1) examination the microstructure of the Sn electrodeposits, 2) measurement of the compressive stress vs. time in electrodeposits and 3) modeling of whisker and hillock growth.