The effect of Bi on the IMC growth in Sn-3Ag-0.5Cu solder interface during aging process

The solder materials used to make the solder joints for this study are: eutectic Sn-3Ag-0.5Cu solder; Sn-3Ag-0.5Cu-1Bi solder; and Sn-3Ag-0.5Cu-3Bi quaternary solder. In order to study the microstructure evolution and the IMC growth kinetics, the solder joints were aged isothermally in a resistance oven at 150/spl plusmn/5/spl deg/C with different periods of 0, 50, 100, 250, 500, and 1000 hours. The result show that: the morphology of IMC changes from scallop-like to planar in the aging process; the mean thickness of IMC layer solder joints is found to increase linearly with the square root of aging time, namely the growth of IMC is controlled by atom diffusion; the IMC growth rate decreased as Bi content increased. For the solders discussed above, the comparative IMC growth rate sequence from fast to slow is Sn-3Ag-0.5Cu > Sn-3Ag-0.5Cu-1Bi > Sn-3g-0.5Cu-3Bi.