Microstructure Evolution of Sn-3Ag-3Bi-3In/Cu Lead-free Solder Joints during Interval Aging

摘要

The microstructure evolution of Sn-3Ag-3Bi-3In/Cu lead free solder joints was investigated over interval aging mode to simulate the real application environment.The solder joints were aged at 150 °C for 48h,96h,144h,196h and 240h,respectively.Results demonstrate that the IMC layer of Sn-3Ag-3Bi-3In/Cu solder joints evolves from scallop shape to layer shape and becomes thicker simultaneously with increasing aging time.It is noteworthy that the IMC layer is composed of only Cu6(Sn,In)5 phase without Cu3(Sn,In)phase during interval aging for various aging time.As a result,the reliability of Sn-3Ag-3Bi-3In/Cu solder joints can be improved due to the lack of Cu3(Sn,in)phase which is detrimental to reliability over interval aging mode.Moreover,it is observed that diffusion control mechanism is fit for the growth of IMC layer of all solder joints over both interval and continious aging mode.Further,the growth formula of IMC layer of Sn-3Ag-3Bi-3In/Cu solder joints is revealed as X=2.56+0.062t~(1/2),in addition,the diffiision coefficient of is obtained as 0.02491μm~2/h.