Reliability Analysis Of Wafer Level Package

The development trend of electronic product is toward lighter, thinner, smaller, and high density. The wafer level packages meet both the trend and low cost requirement. The wafer level packages get popular in market. A number of companies around the world are developing or have begun offering devices processed and packaged in the wafer format.During various of numberical analysis methods, Finite element method is usually used for packaging field. Finite element method describes packaging size, material, boundary condition and load through describing geometry and elements. However, when analyzing the packaging structure, it will result in the fatigue phenomenon because the materials character will vary with the temperature, and Solder Ball also results in fatigue phenomenon because of the dismatch problems about structure' CTE. So when using finite element method to analyze the problem of packaging thermal fatigue, the working is too difficult. It must micronize the elements at the solder ball part so as to get the right solder ball strain state. However, the process of micronizing the elements and computing the material character demands will waste lots of time. The purpose of the third chapter in this paper try to find a right method of micronizing solder ball so as to get the right solder ball strain state and save the computing time of the program. Firstly, the structure of this paper adopts a model with simple packaging structure for testing the solder ball grid, and test part adopts the Pao'double-beam for the model Simulation. The purpose of test not only finds a way of solder ball mincronizing, but also through comparing the test data, confirm the right of the Simulation method. Any way, it uses the error evaluation option of the finite element analysis software ANSYS to be a reference target of analyzing the reliability of the results. The fourth chapter in this paper analyzes the reliability of the WLCSP model, and designs and analyze the reliability of the WLSP.One critical issue of wafer level package failure is the fatigue damage of solder joints. The damage is caused by the mismatch of coefficients of thermal expansion for materials inside the package. In this study, reliability analysis of solder joints on wafer level package under temperature cycle test is performed by nonlinear of solder joint on double beam are compared with experimental measurements to verify the model. Both Coffin-Manson and Modified Coffin-Manson equations are used to predict the fatigue life of solder joints on the package under temperature cycle test. Furthermore, the effect of solder ball layout and stress relax buffer layer material on the fatigue life of solder joints is studied.