Tuan, One of the best references to tin whiskers is S.C Britton, Transactions of the Institute of Metal Finishing. 52, 95 (1974) which was also published by International Tin Research Insitute, London England as "Spontaneous Growth of Tin Whiskers on Tin Coatings, 20 Years of Observations" Publication No. 487. In general the thin tin coatings that are fine grained and bright as-plated are subject to tin whisker growth when subjected to compressive stresses. The fused coatings will also produce tin whisker growth if not thermally treated after fusion to induce larger stress-free crystal size. The stress-free may be negated by later applied stresses such as thermal CTE differences between the substrate and the coating. Lead in the greater than 2% by volume range will inhibit whisker growth. Also a nickel plate under the tin is better than a copper under the tin coating. A brass substrate is the worst. Thin pure bright tin platings either fuse or unfused are the prime prducers of tin whiskers. The type of tin pating bath that you used is important in suppressing whisker growth. The bright tin platings are the worst and matte methane sulfonic being one of the better ones. Lucent Technolgies has one out that they claim has a low-whisker probability. I would prefer to heat treat even the low probability coatings to increase crystal size and internal stress (this is also called annealing) Your description of tin whiskers growing out of a tin-lead deposit on instressed pads does not seem like tin whisker to me as it does not fit in any of the tests that others have run to produce tin whiskers over the last 50 years. Dendritic growths which are produced by electromigration seems to better fit with your description. Phil Hinton Hinton "PWB" Engineering *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************