| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 103 === In recent years, the mainstreams of electronic products are gradually moving to small size, lightweight and multi-functions. To satisfy abovementioned requirements, putting the most of chips in a limited space is a possible way. However, the semiconductor miniaturization has suffered a bottleneck in the development of a 2D packaging technology. In other words, the traditional 2D packaging technology cannot meet the use requirements in the future. Consequently, the developed trend of packaging configuration along the vertical density has attractively paid attention. It implies that a 3D-ICs packaging technology at least has a stacking framework with two chips. Due to the above-mentioned structure is more complex and has a high heterogeneity, the relevant issues of mechanical reliability under the applying of thermo-mechanical loads are easily derived to induce. For this reason, a novel thin-type 3D-ICs packaging structure under the loads of the thermal cycling test investigated by a finite element analysis is proposed in this research. Two different configurations with regard to the molding materials used in the present package are separately analyzed. For the underfill type architecture, the parametric studies of major designed factors such as the thickness of stacked chip, TSV radius, and TSV pitch, are systematically performed. For the packaging constructuin with an arrangement of bi-layerd molding materials, the influence of glass transition temperature (Tg) of molding material on the stress/strain impacts of TSV and microbumps are discussed. Moreover, the predicted approach of microbump fatigue life is utilized to acquire the optimal combination composed of the structural dimensions and materials design parameters. In the meanwhile, the root cause affects structural reliability is also analyzed.
From the analytic results presented in this research, it is found that a higher thermal fatigue cycles of microbump can be obtained while a thinner stacked chip, or a smaller TSV radius, or a larger TSV pitch, are separately taken into account. In addition, when talking about the Tg effect of molding materials, the suggestion of its mechanical characteristics is made and explained as follows. A lower magnitude of Young''s modulus and coefficient of thermal expansion (CTE) for molding material under the situation of its operated temperature is less than Tg is recommended to obtain a higher fatigue life of microbump. On the other hands, a higher Young''s modulus and CTE is suggested as the the operated temperature is larger than Tg.
Throgh the simulated estimation of finite element analysis, this investigation explores the mechanical reliability issues of novel thin-type 3D-ICs packaging structure in actual applications. The related failure mechanisms are also identified and discussed, separately. Therefore, all the results and contributions presented in this thesis can be an important guideline with regard to the in-depth analysis and fabrications of packaging vehicles in the future.
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