Development of newly bump support film (BSF) for WLCSP

Solder joint crack is increasing with increasing of warpage caused by larger Wafer Level Chip Size Package (WLCSP). Bump Support Film (BSF) were proposed as a protect material for preventing a solder joint crack of bumps. The BSF was constructed of a back grind tape and Bump Support Layer (BSL) which was composed of thermosetting epoxy resin. One of the key points of forming the BSL on a wafer which have bumps on circuit surface is to remove organic residues of BSL on the bump top for keeping a good electric connection. In this study, we selected a plasma cleaning process as a removal method of the slightly amount of BSL residue on the bump top. We succeeded to optimize a plasma condition for a good electric connection, and quantify the removal amount of BSL residue by XPS analysis.