In the microelectronics industry, many solder junctions rely upon reaction
between a copper substrate and a molten tin-based alloy. For the tin/copper
system, interfacial continuity is afforded by the formation of the eta (Cu
6Sn5) and epsilon (Cu3Sn) phase intermetallic compounds. The eta grows in a
scalloped morphology along the tin interface with whiskers emanating from
their tops. This article quantitatively describes the unusual growth behavi
or of the eta phase scallops and whiskers formed during reaction of liquid
tin with a solid copper substrate.