Effects of temperature and current density on (Au, Pd, Ni)Sn4 redistribution and Ni-P consumption in Ni/Sn3.0Ag0.5Cu/ENEPIG flip chip solder joints

The Ni/Sn-3.0Ag-0.5Cu/ENEPIG solder joints were used to investigate the effects of temperature and current density on (Au, Pd, Ni)Sn₄ redeposition and Ni-P consumption during electromigration (EM). In as-soldered state, (Cu, Ni)₆Sn₅ type IMCs formed at both the Sn3.0Ag0.5Cu/Ni and Sn3.0Ag0.5Cu/Ni-P interfaces. Temperature and current density played an important role in (Au, Pd, Ni)Sn₄ redeposition and Ni-P consumption. When the solder joints were applied with lower current density (0.9×10³ A/cm²) at lower temperature (85°C), no obvious Ni-P consumption observed. (Au, Ni, Pd)Sn₄ particles still formed in the solder even after EM for 200 h, no (Au, Ni, Pd)Sn₄ particle was observed at both cathode and anode interfaces. When the solder joints were applied with higher current density (1.0×10⁴ A/cm²) at higher temperatures (150 and 180°C), the (Au, Ni, Pd)Sn₄ phases preferred to redeposition only at the anode interface while no (Au, Ni, Pd)Sn₄ was detected at the cathode interface; Ni-P consumption was significantly affected by current direction, i.e., when the Ni-P layer was the cathode side, the consumption of Ni-P was significantly enhanced; when the Ni-P layer was the anode side, no obvious Ni-P consumption was observed.