Development of Double Side Protection Process with Bump Support Film (BSF) and Backside Coating Tape for WLP

Wafer Level Package (WLP) demand has been increasing in proportion to cost competitive device's demand year by year. In order to manufacture the WLP which has higher reliability efficiently, assembly processes with Bump Support Film (BSF) and Backside coating tape has been developed. The BSF consists of Back Grinding tape (BG tape) for getting a function as a wafer thinning and Bump Support Layer (BSL) which is formed on circuit side around the bump for preventing a bump cracking. In addition, the BG tape has bump absorption layer which is thick enough for applying to various bump pitches, heights and chip geometries. In this paper, two main investigations are reported. One is process evaluation with Test Element Group (TEG) and Substrate. The other is comparison of reliability after Thermal Cycle Test (TCT). As a result, we succeeded in forming BSL with a little of residue at the bump top with bump absorption layer which has higher elastic modulus at the large deformation region than that of BSL, and one minute of plasma etching as cleaning of bump surface. We also succeeded in manufacturing double side protected package which has higher reliability than a package without protection at wafer level.