Size and boundary effects on the growth and morphology evolution of interfacial intermetallic compound of Sn0.3Ag0.7Cu/Cu micro-bump joints

In the present study, Sn0.3Ag0.7Cu spherical solders with diameter in the range of 10~50 μm were assembled on the flux-coated Cu metallization and then reflowed at temperature of 250°C to form Sn0.3Ag0.7Cu/Cu micro-bump joints, and the size and boundary effects on the growth and morphology evolution of interfacial intermetallic compound (IMC) of micro-bump solder joints were studied. Results show that the growth behavior of interfacial IMC grains in micro-bump solder joints is significantly influenced by the solder joint size and boundary, the size of interfacial IMC grains increases with the decrease of the solder joint size (i.e., the decreasing diameter from 50 to 10 μm). In micro-bump solder joints with small size, the proportion of surface diffusion channels in the total diffusion channels (including the IMC lattice, surface diffusion channel and the channels between the IMC grains) is much higher than that of the joints with large size, the growth of IMC is controlled by the surface diffusion mechanism when the size of solder joints is very small.