Microstructure coarsening during static annealing of 60Sn4OPb solder joints: III intermetallic compound growth kinetics

The growth of the total (Cu3Sn+Cu6Sn) intermetallic compound layer in Cu60S n4OPb solder joints during static annealing at 50 degreesC to 150 degreesC was described by the equation h = h(o) + A(o) exp(-Q(a)/RT)t(p) with h(o) = 0-0.3 mum, p=0.38-0.70, A(o)= 1.9x10(-4)-3.4x10(-4) m/s(p), and Q(a) = 25.5-30.9 kJ/mole. These constants are within the range of those ob tained by others and give values of D-o and Q which are in reasonable accor d with those for the diffusion coefficients in Cu3Sn and Cu6Sn5 determined in diffusion couples. The deviation of the values of the time exponent p fr om the ideal of 0.5 for diffusion growth may be due to inaccuracies or erro rs pertaining to the measured thickness (especially h(o)) and the complex n ature of the diffusion process.