| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 95 === Along with the vigorous development of the electronic products market and the consumer’s preference for products with smaller size, the structure of 3D stacked die package rapidly becomes popular. Thus the stacked behavior of the silicon dies always makes the coupling effect among materials more complicate. Such an issue has been seriously paid attention to the reliability and becomes a critical problem.
This research applies the ANSYS finite element software to analyze a twin die stacked package under a thermal cycling loading. The viscoplastic finite element analysis and the Darveaux theory are applied to investigate the solder joint reliability of the stacked die package. This research will verify a significant dependence between the fatigue life of the solder joint of the stacked die package versa the distribution of the accumulative strain energy density on the solder by the viewpoint of the average and the variance of the strain energy density among solders in accordance with a 3D slice model. Meanwhile, the Von Mises stress range at the substrate is investigated for the reliability of the solder joint. It can be expected a possibility where the fatigue life of the solder joint of the stacked package is not necessary to exist on the outmost solder ball, then an efficient and complete analysis can be obtained. Furthermore, by incorporating the simulation analysis, the viewpoint of the accumulative strain energy density among solder balls, the single-factor experiment as well as the Response Surface Method, the effects of the parameters of the stacked die package on the solder joint reliability are analyzed to promptly and accurately determine the optimal stacked die structure so as to enhance the reliability of the package.
The result of study shows that more accumulative strain energy density of # 4 solder ball (the outermost solder ball) makes itself fatigue life lower because the twin die stacked package can produce extra die edge effect on the die overhang area. In addition, for enhancing solder joint reliability of the twin die stacked package, thinner top die, thicker bottom die, thicker substrate, thinner PCB, lower molding compound Young’s modulus and lower substrate Young’s modulus are preferred by the analysis result of single factor; while the molding compound CTE is larger than the substrate CTE, location of the critical solder ball changes. Finally, by the F-test and the adjusted coefficient determination, the accuracy and applicability of these response surfaces are demonstrated after building response surface models in the aspect of geometry configurations as well as material properties. Furthermore, the optimal design is obtained with full-factor experiment and response surface model.
|
|---|
