LAUSR

The effects of micro solder joint geometry on intermetallic compound (IMC) growth and electromigration during thermal aging and current stressing have been investigated using three groups of specimens: sandwich structure with solder layer of 10 μm to 50 μm, wire butt with solder layer of 60 μm to 240 μm, and solder ball with diameter of 200 μm to 500 μm, each having Cu/Sn/Cu structure. The results indicated that the geometrical size of the micro solder joint clearly affected the interfacial element diffusion and IMC evolution. Furthermore, when the solder layer thickness was less than 30 μm, the growth rate of the IMC layer decreased significantly with decreasing solder layer thickness, because Sn element was nearly exhausted in the micro solder joint during thermal aging.