Effect of polycrystalline Cu microstructures on IMC growth behavior at Sn/Cu soldering interface

This paper investigated the morphologies of intermetallic compounds (IMCs) forming between pure Sn solders and different polycrystalline copper substrates with microstructures of fiber structure, equiaxed crystal and columnar crystal respectively as well as the effect of Cu microstructures on IMC growth kinetics. The results showed that when multiple IMC grains could be accommodated in a single grain area of substrates, the IMC growth behavior on some grains of polycrystalline substrates was similar to that on single crystalline substrate of same orientation. The difference on polycrystalline Cu substrates was that IMCs with different morphologies appeared alternately. Furthermore, the IMC distribution at soldering interface was stripy on fiber structure and blocky on equiaxed crystal substrates. With increasing of reflow temperature or time, IMCs with different morphologies followed their own growth behavior. In addition, the grain growth rate of IMCs on columnar crystal substrate was higher than that on the other two substrates due to different Cu supply and diffusion abilities.