New and novel failure analysis technique of COL package device with WBC non conductive epoxy and The failure mechanisms of the electrical shorting of the die back to the lead

Chip on Leads or COL is a package without the Die Flag or Die Attach Pad (DAP), where the Die is bonded directly on the leads using non-conductive epoxy as the electric isolation material between the die back and the leads. Problem arises when the electrical isolation between the die back and leads has failed. Identifying the electrical short path between the die back and the leads is a challenge for failure analysis of COL package. One need to understand the device bill of material (BOM), bonding diagram and package structure before this COL die back to lead short failure mode can be confirmed by a method of combination of die isolation from the package and micro-probing. Thermal-Induced-Voltage-Alteration (TIVA) was then used to locate the physical bridging between die back and lead. This paper entails the challenge in identifying the electrical shorting path on bench, the TIVA and progressive FIB technique. Failure mechanisms are also discussed.