In this research, thermal deformations of CSP assemblies under power cycling were investigated using high sensitivity moirö interferometry and finite element analysis and the results under power cycling were compared with those under chamber cycling which is obtained from the same techniques. To observe the thermal deformations during chamber cycling, a moirö test was performed for the isothermal loading condition from 125℃ to 25℃. In the case of power cycling, the actual operating condition was simulated using a thermal chip in the package and the real-time moirö interferometry technique was used to measure the steady-state thermal deformation. The results show that the assembly bends in the opposite direction in power cycling as compared to its bending under chamber cycling. In addition, the test results obtained from the moirö interferometry technique were compared with the predicted values obtained from the finite element analysis. It is shown that the deformation values predicted from the finite element analysis have a good agreement with those obtained from the test. The FEM results show that the shear deformations of solder joints are almost same but the normal deformations are fundamentally different between the chamber cycling and the power cycling.
