COMPOUND GROWTH IN PLATINUM/TIN-LEAD SOLDER DIFFUSION COUPLES

摘要

The two types of reactions that occur between 60/40 tin-lead solder and platinum were explored: (1) solid-state diffusion, in which the intermetallic compound PtSn4 was observed to form; and (2) dissolution. Both bulk and thin-film couples were used and the extent of reaction in each was revealed by optical and scanning electron microscopy methods. Solid-state compound growth followed parabolic kinetics with an effective activation energy of 23 kcal mol(-1) (96.2 kJ mol(-1)). Diffusion of platinum through PtSn4 appears to limit compound growth. Dissolution of platinum wires in solder resulted in a linear decrease in wire diameter with time. The process occurred with an activation energy of 20.4 kcal mol(-1) (85.4 kJ mol(-1)) and was attributed to Pt-Pt bond breaking assisted by strong chemical interaction with tin. [References: 15]