Application of silicon stress sensor in flip chip packaging system

Flip chip packaging system consists of different materials in the connecting parts, and has an undesirable stress distribution on the chips. Large residual strain will lead to a deterioration of the circuit performance, and researchers are working to reduce the residual strain in the packaging system. In our work, a silicon stress sensor chip is fabricated to measure the stress distribution in flip chip packaging system, and four point bending method is used to calibrate the piezoresistance coefficients. The effects on residual strain caused by chip size, location, underfills, and the packaging process are tested, and a relationship between the parameters above and stress distribution is discussed.