Analysis of the stress state in QFN package during four bending experiment utilizing piezoresistive stress sensor

This paper reports a comprehensive study on four point bending experiment and its correlation with numerical simulation. As test vehicle we have used a board with 16 QFN components soldered on the top and bottom side of the PCB. Each QFN had two piezoresistive stress sensors. Each sensor has 60 stress sensing cells, in total 120 per QFN. In our study we have investigated the stress state in the QFN utilizing piezoresisitve stress sensor and compare it with numerical model. Stress analysis showed that components very close to the edge are exposed to the slightly higher stress (20%) as the other components placed in the center of the PCB. In case of numerical simulation, we have found that the most important on accuracy is the exact geometry.