Improving Moldability by Regulating Thixotropy of Epoxy Molding Compounds

In terms of the epoxy molding compound (EMC) fluid, flash length and the formation of the air trap void during molding is highly related to the moldability and rheological properties, which are influenced by the thixotropy of the fluid. It is of significance to study the moldability and rheological properties to provide theoretical guidance for the molding processing. In this work, the relationship between the thixotropy and moldability of the EMC fluid was systematically investigated, and the thixotropy of EMC can be regulated by the introduction of fumed silica in EMC. The thixotropy of the EMC fluid at 175 ^°C was characterized by a rotational rheometer, and the moldability can be reflected by the flash length test as well as the air trap void inspection with the real package. The rheological results show that with the increase of the fumed silica, the area of thixotropic loop of the EMC fluid is increased, indicating that the thixotropy of the EMC fluid is enhanced with the addition of the fumed silica. The flash length test results display that the flash length of the EMC fluid becomes shorter with increasing the fumed silica. The scanning acoustic microscope (SAM) results of the real package exhibit that when the content of the fumed silica is 0.3wt%, the air trap void defect ratio in package is also less, indicating that this addition amount is the optimal content for moldability. The moldability of EMC can be improved by regulating the thixotropy.