Delamination analysis of electronic package assemblies with insulated metal substrate

Electronic packages are multi-layered structures with a large number of interfaces. Under certain conditions, some interfaces could delaminate, resulting in failures. Reliability tests on flip chip assemblies of L8AA daisy chain die on insulated metal substrate (IMS) have revealed that the lifetime is mainly determined by the material interfaces. The dominating end of life failure mechanism is interfacial fracture between underfill and passivation layers. A fundamental understanding of these failure mechanisms and the experimental characterization of associated material properties are a key requirement in order to develop an optimal package design with an extended life time of the interconnect system. For flip-chip assemblies, packages with LMS substrate are much more prone to interface delamination than packages with FR-4 substrate. Cracks in the packages with IMS substrate are not catastrophic. In this paper, finite element approach, incorporated with interface fracture mechanics method, has been used to investigate the interface failure phenomenon. Excellent agreements have been obtained between experimental data and the simulation results.