Study on Sn-2.3Ag Electroplated Solder Bump Properties Fabricated by Different Plating and Reflow Conditions

In this study, the properties of electroplating plating Sn-2.3Ag solder bumps fabricated by several plating and reflow conditions have been investigated through destructive (bump shear/pull) test, X-ray diffraction analysis, focused ion-beam (FIB) cross-section images, and SEM inspections. The metal compositions, plated plateau surface morphologies, plated pillar microstructures, and plated grain orientations of the as- plated pillar samples show strong dependence on different plating current densities in plating process. The reflow process then took place to re-organize the metallurgy of Sn-Ag solder bumps. It has been found that the cooling rate dominates the grain orientation in reflow process, and the inter-metallic compounds (IMC) microstructure is also been found affected by the reflow profile. The thickness of IMC increases with increasing melting time. Changing cooling rate can directly change the reflowed bump surface grain distribution. From the results of destruction test, it shows that the microstructure of the IMCs can essentially change the bump shear and bump pull failure modes and strengths. In the final part of the study, multi-times reflow has applied to verify different reflow profiles impacts on solder properties.