Silver barrier layers to minimize whisker growth in tin electrodeposits

摘要

The invention relates to a method of reducing tin whisker formation in a plated substrate that includes a surface layer comprising tin. The method includes providing on electroplatable portions of the substrate (a) an underlayer comprising silver or (b) a barrier layer that passes a mechanical load test when the surface layer, after 48 hours of contact with a 1 mm hemispherical tip that carries a load of between 500 to 2000 g, exhibits no whiskers having a length of greater than 5 microns. The underlayer or barrier layer, whichever is present, is provided in a thickness sufficient to prevent formation of intermetallic compounds between the substrate and surface layer so that the surface layer exhibits reduced whisker formation compared to the same surface layer deposited directly upon the substrate. Typically, the underlayer or barrier layer includes 50 to 100% by weight silver or similar ductile material.