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 100°C to room temperature and the other is from room temperature to 100°C. 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.