Investigation of Peeling Behavior of UV Curable Pressure Sensitive Adhesive for Bump-Wafer

In this study, the peeling process of UV-curable pressure sensitive adhesive tape from bump wafer is investigated through the use of finite element analysis, observation of high speed video, and actual wafer back-grinding process testing. In our experiment, a large deformation of adhesive is observed at the edge of bottom of bump, appearing on the side of the bump opposite tape-peeling direction when observed with high speed microscope video. The largely deformed adhesive creates a string shaped elongation. The adhesive residue is caused by the fracture of the adhesive string. We investigated how to generate the adhesive string in the tape-peeling process through the use of finite element analysis. In this analysis, a cohesive element is introduced into the adhesive layer. The analytical result shows the adhesive string at the same position of experiment and the stress distribution is different between the string part and the other area of adhesive. The influence of peeling angle and bump size is also investigated by the same finite element model. As a result, higher peeling angle and smaller bump sizes shows a shorter adhesive string, which lowers the risk of adhesive residue.