| Summary: | 碩士 === 長庚大學 === 機械工程研究所 === 94 === The purpose of this study is to investigate the stress analysis and failure behavior of the optic-electronic package, molded with three different molding-compounds (M.C.s), under thermal cycle test (TCT). First, the failure modes of package after TCT are documented by red-ink immersion, surface acoustic microscopy and optic microscopy. The material properties of three M.C.s and Ag-epoxy are determined by dynamic mechanical analyzer, thermal mechanical analyzer, differential scanning calorimetry and Twyman-Green (T/G) interferometry. Then, the stress distributions of package under TCT due to mismatch of CTE of materials and stress field of the peel test sample under mechanical and thermal loading are understood by linear and nonlinear finite element analysis (FEA). Further, the shadow moiré system is used for investigating the effect of chemical shrinkage on package and peel test sample. Moreover, the peel stress and strength are calculated quantitatively to predict the package whether they fail or not. Finally, moisture diffusion on peel strength of material interface between M.C. and alloy194 is studied.
The results show that delamination is occurred in packages with M.C.-B and -C, but not M.C.-A. The material properties of M.C.s and Ag-epoxy were obtained successfully by experiments. From FEA, it is found that the large peel stress at material interface is dominant in the package. From nonlinear FEA with considering chemical shrinkage, the maximum peel stresses of the package under TCT are 62.8, 65.4 and 75.6MPa for M.C.-A, -B and -C, respectively. On the other hand, from the peel tests, the average of maximum peel strengths between three different M.C.s and alloy194 are 88.1, 65.4 and 53.8MPa, respectively, including the effect of chemical shrinkage. The failure of the packages can be predicted by comparing with the maximum peel stresses and maximum peel strengths. Furthermore, the peel strength between M.C.-A and alloy194 doesn’t decrease after 85℃ and 85%RH condition.
|
|---|
