Effect of solder volume on diffusion kinetics and mechanical properties of microbump solder joints

This study, mainly emphasis on effects of solder volume on interfacial diffusion kinetics and mechanical properties of Sn/Cu microbump solder joints. Different thicknesses i.e. 12 μm Sn (electrodeposited) and 100 and 200μm Sn is screen printed over 14 μm thickness Cu under bump metallization (UBM). The diameter of Cu UBM used in this study is 50, 110 and 240μm respectively. Solder joints are subjected to multiple reflows up to 10^th reflow at 245, 265 and 285°C for 60, 90 and 135 seconds under nitrogen atmosphere in a reflow oven. Morphology and diffusion kinetics have been studied with reference to reflow temperatures, multiple reflows and reflow time. Interfacial Cu-Sn intermetallic growth rates and activation energies were determined. Micro-mechanical properties of microbump solder joints, nanoindentation experiments with CSM method have used to determine the elastic modulus and hardness of the microbump solder joints.