Internal stress state of TQFP subjected to liquid thermal shock using piezoresistive silicon stress sensor

As autonomous driving is becoming reality, more advanced solutions to enhance reliability of safety relevant systems are demanded. One of such solutions is to consolidate prognostics and health management concepts. It can be accomplished by understanding the failure, recognizing it from the field signals, and eventually predicting it. This study focuses on the second step, namely recognizing the failure from sensor signals. The test vehicle used in the study is a Thin Quad Flat Package (TQFP) mounted on a printed circuit board (PCB). The package contains 8 piezoresistive stress sensors which replaces the functional die. The test vehicle is subjected to liquid thermal shock testing conditions, and the stress state changes inside the package are recorded by stress sensors. Each sensor contains 60 stress-measuring cells, which provides the internal stress state of the package with high resolution and accuracy. The internal stress state is used to identify the failure times and locations.