Reaction Diffusion in Pb Free Solder-Cu System

Reaction diffusion in liquid Pb free solder- and solid Pb free solder- pure Cu systems has been investigated in the temperature range between 397 K and 563 K. The Pb free solder of which composition is 95.7 mass% Sn, 2.8 mass% Ag, 1.0 mass% Bi and 0.5 mass% Cu and 99.99 mass% oxygen free Cu has been used. In the liquid Pb free solder-pure Cu system, as soon as the solder melted down, an intermetallic compound phase formed preferentially, and grew with increasing diffusion time. Only the phase exists in the experimental time up to 120 seconds. The layer thickness of the phase obeyed the parabolic law. On the other hand, in the solid Pb free solder-pure Cu system two intermetallic compounds  phase and ’ phase form and grew with increasing diffusion time, although the  phase forms after an incubation time at low temperature. The layer thickness of these intermetallic compounds obeyed the parabolic law. The growth rate of ’ phase is greater than that of the  phase. The growth kinetics of the intermetallic compounds and the diffusion behavior in the ’ phase have been investigated.