Investigation on failures of plastic package devices with unidentifiable defects related to deficient molding process

Chip with bonding wires and lead frame of a plastic encapsulated device is sealed with molding compound to prevent any foreign matters from getting inside. This work is completed during the process called as molding process, which is a very important link in device encapsulating. However, under the influence of equipment, environmental factors or raw material, some encapsulation defects might arise due to deficient molding process. Some of these defects could not be identified by appearance inspection and electrical parameter test in the device factory. The devices with these unidentifiable package defects would flow into the market and usually lead to product failures when the devices are used by consumers. This paper will analyze some failure cases of those to show what these defects are and study how the failure happen.