封裝體立體堆疊(Package On Package, POP)是成長最迅速的封裝技術之一，即利用測試好的封裝體(Package)在厚度方向透過回焊(reflow)的方式堆疊起來，形成三維系統級封裝(3D System in Package, 3D SiP)的封裝架構以達到高密度封裝與縮小封裝規模的目的，例如動態隨機存取記憶體(Dynamic Random Access Memory, DRAM)或靜態隨機存取記憶體(Static Random Access Memory, SRAM)的堆疊應用。
本研究利用有限元素分析軟體ANSYS 建立底層可堆疊甚薄精細間距球柵陣列(Package Stackable Very Thin Fine Pitch BGA)疊合晶片級封裝(Chip Scale Package, CSP)有限單元分析模型，其中構裝體含有六個組件，分別為錫球(Solder Ball)、晶片(Chip)、封膠(Molding Compound)、基板(Substrate)、熱通孔(Thermal Via)、印刷電路板(Print Circuit Board, PCB)，進行熱傳與熱應變模擬分析。
熱傳分析方面，構裝體與外界初始溫度為50℃，在自然對流與強制對流的情況下，以Ellison熱對流理論為基礎模型建立數學公式，並且經由改變晶片瓦數，觀察其熱傳行為；熱應變分析方面，錫球材料的黏塑性特性以Anand模型模擬，成形樹脂材料的黏塑特性以Maxwell模型模擬，其他部分則以彈性體模擬，模擬構裝體承受-40℃到125℃熱循環負載下的變形行為，並研究改變材料參數對構裝體的影響，各別針對最大錫球等效應變量作分析，找出錫球最容易受到破壞的部位，最後再配合modified Coffin-Manson equation求其疲勞壽命。

Package-On-Package(POP), one of the most growing technology of package, is a member of the System in the Package (Sip) family. It is constructed by stacking individually assembled and tested packages in a three-dimensional tower-like structure through solder joints to have higher packaging density and size shrinkage, such as Dynamic Random Access Memory(DRAM) or Static Random Access Memory (SRAM) stacking applications.
This research uses three dimensional model simulation to analyze the thermal-mechanical and heat transfer behavior of a Package Stackable Very Thin Fine Pitch Ball Grid Array (PSVFBGA) stacked on top of a Chip Scale Package (CSP) by applying the finite element analysis of the commercial software ANSYS . The package body components have six parts, including solder ball, chip, molding compound, substrate, thermal via, and printed circuit board (PCB).
For the heat transfer analysis, the beginning temperature of POP and surrounding area is 50℃. In case of the natural convection and force convection, the natural heat transfer coefficient and force heat transfer coefficient can be calculated by the Ellison equation, and then change the chip power to study the thermal behavior. For the analysis on the thermal-mechanical behavior, the solder ball is modeled using viscoplastic Anand's model, the viscoplastic behavior of the molding compound is simulated by the Maxwell model, the others simulated as linear elastic. In the finite element analysis, the transformation behavior of the package body was carried out under a -40 ℃ to 125 ℃ thermal cycling environment. At the same time, the maximum equivalent strain was calculated in order to find the weakness part of the assembly, and we can thus understand the influence on the strain field by changing material properties. Finally, the solder ball reliability was estimated by the widely accepted modified Coffin-Manson equation, and the thermo-mechanical behaviors of the solder ball were appropriately presented.

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