| Summary: | 碩士 === 中華大學 === 機械工程學系碩士班 === 100 === The trend of electronic products today is moving toward further miniaturization, high functionality and improved performance. To accomplish this, new packaging needs to be able to integrate more dies with greater function, higher I/O counts, smaller pitches, and greater heat densities, while being pushed into smaller and smaller footprints. The package-on-package (PoP) is one of the 3D packaging solutions, which typically integrates a high-density digital logic processor at the bottom package with high capacity memory dies on the top package. However, the surface mount between top and bottom package encounters the bump collapsed problem in the manufacture process when the interconnection pitch is less than 0.4 mm. Instead of traditional interconnection bumps, the high copper pillar (HCP) structure is an alternative technology to meet the smaller pitch requirement.
This study focuses on the thermal-mechanical performance of the PoP package with high copper pillar structure under temperature loadings. In this study, a 3-D half symmetrical nonlinear finite element model of a PoP package was developed using ANSYS finite element simulation. A temperature cycling test in the range of -55 °C to 125 °C was conducted by three cycles. The mechanical property of SAC and SnAg leadless solder are considered as Anand viscoplastic behavior. The stress, plastic strain and plastic work distributions in each component of the package were investigated.
Due to the complicate PoP package structure, the 3-D equivalent global model and local submodeling technique were applied. The equivalent global model is capable of addressing cirtical component failure locations. Individual local solder ball is then used to predict the perfoemance in detail.
To investigate the dimension of HCP to the PoP performance, An L4(2×3) Taguchi matrix was developed to investigate the effects of copper pillar height, pitch and diameter on each component performance. Two levels were chosen for each parameter to cover the ranges of interest. The results show that the best combination to a total of 11th different physical behaviors. These could be used as guides for PoP and further similar 3-D stack packages design.
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