Curing Analysis of a Flip-Chip-on-Board Electronic Package

Abstract

A curing analysis of a Flip-Chip-On-Board (FCOB) assembly is reported in this paper. It is very important to understand the curing process of the FCOB assembly because a good curing scheme may obtain full mechanical and thermal properties of the epoxy. In order to do numerical simulations of the curing process, it is essential to establish the cure kinetic equations of the epoxy. Differential Scanning Calorimetry (DSC) tests were performed to collect experimental data. It was shown that the cure reaction satisfies the Arrhenius relation. It also was verified experimentally that the chemical curing reaction may be incomplete at lower isothermal cure temperatures. Various cure kinetic equations were used to fit the experimental cure data. The results show that the kinetic equations can be used to predict other DSC experiments quite well. Two FEM models of the FCOB assembly, associated with the two different curing schemes, were analyzed by use of the FEM software ABAQUS. The cure kinetic equations were implemented in a user subroutine to update the heat generation due to the chemical reaction of the epoxy. Due to the part’s thinness, the results show that both the temperature and the degree of cure are distributed very uniformly over the FCOB assembly in the whole curing process, and that the history responses are almost independent of the sizes of the models. It is also proved numerically that the proposed curing scheme is better in that it may have the epoxy more fully cured.