Effect of Diamond Additions on Wettability and Distribution of SnAgCu Composite Solder

Diamond/SnAgCu composite solder bumps were prepared on Cu pad by mechanically incorporating diamond particles into Sn3.0Ag0.5Cu (SAC) solder powders, mixing with flux and reflowing at 260 °C for 60 s. The spreading areas of composite solder were calculated and the distributions of copper-coated diamonds were characterized. When diamond additions were below 3 wt%, the spreading area decreased with diamond additions, and the diamonds distributed mainly at the interface between solder and Cu pad; however, when additions were beyond 4 wt%, the discharge of diamond particle occurred, and the spreading area increased due to the reduction of surface energy.