Thermo-mechanical analysis of a wafer level packaging by induction heating

In this paper, a non-linear and one-directional coupled finite element framework has been implemented to simulate induction heating process of wafer-level packaging. Based on numerical results of induction heating, thermally-caused warpages and stresses of the single-sided ceramic wafer have been evaluated. Some primary experiments have also been conducted to verify the numerical method. Using three-dimensional models, the temperature distribution, thermally-caused warpages and stress in the single-sided ceramic wafer subjected to induction heating can be clearly defined. In addition, the temperature-dependent material properties are considered in the modeling. From the finite element analysis, it is found that the induction heating is selective, that is, the temperature in the wafer is lower than that of Cu-loops during the induction heating process; the temperature variation on the Cu-loops, as well as the difference of the temperature between the Cu-loops and the wafer is related with the wafer material properties; the maximum thermal-stresses caused by the induced Joule heating occur on the middle-edge areas of the single-sided ceramic wafer. On the other hand, in order to prove the soundness of the framework established in this paper, the test results obtained by infrared radiometer are compared to that achieved from the proposed numerical analysis method. It is shown that the temperature variation and locations of initial cracks caused by thermal-stresses during the induction heating are in a good agreement with those obtained from the test.