Evaluating plastic assembly processes for high reliability applications using HAST and assembly test chips

We demonstrate the use of HAST and Assembly Test Chips (ATCs) to evaluate the susceptibility of epoxy molding compounds to moisture induced corrosion of Al conductors. We show that the procedure is sufficiently sensitive to discriminate between assembly processes used by different molding facilities. Our data show that the location in time of the “knee” in the failure distribution is dependent on material properties of the epoxy. Reducing the failure rate in the early or “extrinsic” region of the time-failure distribution is key to achieving high reliability. We examine the failure modes in the extrinsic region for test chips encapsulated with a number of high quality molding compounds in an attempt to better understand this region