Compression Molding Encapsulants for Wafer-Level Embedded Active Devices: Wafer Warpage Control by Epoxy Molding Compounds

Fan-out wafer level packaging technology (FOWLP) is one of the advanced packages in semiconductor industry. Recently, its interest has been raised due to the benefits such as thin package, board fan-out capability, high I/O, substrate-less process, integration of passives into structure, good thermal resistance, and electrical performance. Despite these many advantages, FOWLP is reluctant to be applied packaging industries due to the difficulty of controlling wafer warpage. Its broad molding area causes warpage control of FOWLP to be more difficult than other packages. The relationship between molding area and warpage have trade-offs, which have to be optimized beforehand in order to ensure successful subsequent processing. In order to control both factors, it is necessary to study the properties of Young's modulus, coefficient of thermal expansion (CTE), glass transition temperature (Tg), and flow-ability for wafer level mold compounds of interest. In this paper, our group introduces an evaluation tool based on all above parameters and explains how to optimize warpage of FOWLP based on this tool.