Development of Bump Support Film (BSF) for expanding the size of WLCSP

Solder joint crack is increasing with increasing of warpage caused by larger Wafer Level Chip Size Package (WLCSP). In this study, we studied new Bump Support Film (BSF) made of back grind tape and thermosetting epoxy resin, which covers the bottom of bumps by heat lamination. We succeeded to form the BSF without voids at the bottom of the bumps by optimizing the thickness of thermosetting epoxy resin layer. We also succeeded to remove residues of BSF at top of the bumps by dicing process. In addition, the board level test of IC chip with BSF shows no electrical defect after reflow process.