Microstructural, compositional and hardness evolutions of 96.5Sn–3Ag–0.5Cu/TiC composite solder under thermo-migration stressing

A 96.5Sn3Ag0.5Cu (SAC305) lead-free composite solder containing 0.1 wt% titanium carbide (TiC) was prepared using the powder metallurgy method and a thermal migration (TM) experiment was then carried out. A temperature gradient generating device was designed and a TM sample with an asymmetric sandwich structure was prepared in order to achieve this. The microstructure, the composition and the mechanical properties of both the SAC305 and SAC305/TiC solder joints were investigated under a temperature gradient of 1070 K/cm that was generated by the TM device that had been designed. The results showed that the addition of a TiC reinforcing phase was able to effectively inhibit both the diffusion and migration of the Cu atoms, and that this affected the distribution of the Cu6Sn5 intermetallic compounds (IMC) under the thermal migration conditions in the solder joint. It has also been shown that, compared with the plain SAC305 solder joint, the interconnect interface of the composite solder joint was relatively intact after 600 h of thermal loading. The results of the nanoindentation test also showed that the addition of the TiC reinforcing phase was able to significantly weaken the distribution gradient of the hardness of the solder joint caused by element migration.