COMPARISON OF MECHANICAL FATIGUE FRACTURE-BEHAVIOR OF EUTECTIC SN-AG SOLDER WITH AND WITHOUT CU6SN5 INTERMETALLIC PARTICULATE REINFORCEMENT

A first step in developing reliable models for the microstructural beh avior of solder is to understand the deformation mechanisms that opera te under service conditions seen in actual solder assemblies. In servi ce, solders experience complex loading conditions, such as creep and f atigue, under several possible modes, including tension, shear, and to rsion. Of these loading conditions, the isothermal mechanical fatigue fracture behavior of non-composite eutectic Sn-Ag and composite eutect ic Sn-Ag solder containing 20 V% Cu(6)S5(n) is examined in this paper Single shear lap solder joints of both spiders were fabricated using c opper substrates and subjected to isothermal mechanical, cantilever be nding fatigue at a frequency of 50 Hz. The fracture surfaces of non-co mposite eutectic Sn-Ag solder joints exhibited ductile, mixed mode (I and II) fracture behavior and step-type fatigue striations that origin ated at a local region. The fracture surfaces of the composite eutecti c Sn-Ag solder containing 20 V% Cu6Sn2, exhibited cleavage of the Cu6S n5 particulate reinforcement and ductile, Mode I fracture of the eutec tic matrix with no single origin of initiation co; responding to homog eneous ductile fracture.