The influence of solder on the thermal stress in a FCOL device

摘要

Early package level failures mainly showing as passivation crack under the copper pillars were observed in a commercial product of flip chip on leadframe (FCOL). The failures are caused by higher stresses that are related to the shape of solder profile and the thickness of intermetallic compound (IMC). To understand the influences of the two factors, the finite element analysis was performed for the measured solder profiles in SEM images of failure analysis and the different IMC thickness. From numerical results, it suggests that an increased effective solder thickness under refined inline process and controlling the IMC thickness within an appropriate range would significantly contribute to reducing stresses at the die side.