Novel sheet molding compound technology for wafer-level packaging to overcome wafer warpage issue

We report the sheet molding compound (SMC) technology to solve the wafer warpage problem that occurs after the compression molding process, which is a critical technical problem in wafer-level packaging (WLP) process. Wafer warpage is known to be caused by the mismatch of coefficients of thermal expansion (CTE) between carrier wafer and molding compound. An effective method to improve the warpage involves reducing the molding thickness, which induces thermal shrinkage volume of molding compound. Liquid molding compound (LMC) has been used in the compression molding process for WLP; however, a thin molding process with LMC causes flow marks. In this report, the relationship between flow mark and wafer warpage is studied by the difference of molding compound type, LMC and SMC, respectively and feasibility of reducing warpage by thin molding was verified with each process.