I. Introduction
With merits like high encapsulation efficiency, high density and small form factor, FBGA packages (See Fig. 1) become widely used in IC products. Package encapsulation is done through a molding process where EMC will have chemical reaction under a high temperature and high pressure condition. However, the molding process of FBGA will induce package warpage, which can not only impact the follow-up assembly process, but also degrade product reliability [1][3]. Package warpage is typically caused by both thermal shrinkage and chemical shrinkage. Warpage due to thermal shrinkage results from CTE (Coefficient of Thermal Expansion) mismatch between constituent materials; while chemical shrinkage induced warpage results from the polymerization conversion of EMC during curing; and PMC process can also affect warpage through chemical aging [4][6]. Schematic of FBGA Unit