Study of underfill dispensing for a large-die package

The major function of underfill is to reduce stress from coefficient of thermal expansion (CTE) mismatch and protect bump. For three-dimensional integrated circuit (3DIC) demand, large TSI die size is market trend due to the requirements of functionality and performance in electronic device. It is a bottleneck that time required for capillary flow out of the underfill in the large die package. The suitable combination of material, flow temperature and dispensing pattern may cause the maximum benefit. In this research, a large die with normal C4 bump structure is used to study the underfill type, flow temperature and dispensing pattern. Two kinds of underfill were chosen to study in this paper. The resin type is amine for Underfill A and phenol for Underfill B. The flow temperature is chosen depend on the properties of underfill. Pattern study is one of the key factors for underfill encapsulated. Underfill filling and flowing capability is determined by scanning acoustic tomography (SAT).