Effect of transfer pressure on die attach film void performance

With the development of high density packages, the space from die edge to bond finger is shrunk and challenge comes into being for liquid-type adhesive correspondingly due to its bleed-out. Die attach film (DAF) as alternative has being widely used with its good control of bleed, consistent bond line thickness (BLT) and simplified operation. However void at the interface between die and substrate is one of major concerns. There are many factors contributed to void performance including DAF material property, substrate surface condition, die attach parameters and so on. In this paper, the effect of transfer pressure on void performance in a ball grid array plastic package is focused on. Simultaneously the characteristic of DAF void and its formation/reduction mechanism also are investigated. It was found that the DAF voids occur at substrate/film interface with fixed location and similar pattern. They can be reduced significantly by enhancement of transfer pressure during molding process, which can be explained that gap on substrate surface is filled furthest by film under high transfer pressure.