Measurement of creep and relaxation behaviors of wafer-level CSP assembly using Moire interferometry

In this paper the creep and relaxation behaviors of a wafer-level CSP assembly under two types of thermal loading conditions were investigated using high sensitivity moire interferometry. One is a thermal load from 100degreesC to room temperature and the other is from room temperature to 100degreesC. In the second case, the real-time technique was used to monitor and measure the shear deformations of solder joints and the warpage of the assembly during the test. For the real-time measurements of thermal deformations, a small-sized thermal chamber having an optical window was developed. In addition, the test results obtained from the moire interferometry measurements were compared with the predicted values obtained from finite element analysis. It is shown that the deformation values predicted from finite element analysis have a good agreement with those obtained from the tests.