近年來，消費性電子產品的發展有朝向輕量化、微小化及可攜化之趨勢，針對可攜帶式電子構裝產品，常因人為疏忽或搬運時而掉落地面，而造成產品的破壞與失效。其中，錫球是最容易產生缺陷的地方，無鉛材料接點比起含鉛材料接點來較硬且脆，容易在衝擊負載下因為吸收衝擊能量而破壞，造成構裝元件的失效，如何提升無鉛錫球在衝擊負載下的可靠度便成為相當熱門的研究方向。 本研究將採用ANSYS 10.0 套裝分析軟體，根據JEDEC 規範將TFBGA構裝體施予最大1500G作用時間0.5ms之加速度衝擊負載，其中，錫球考慮彈塑性材料模式，其它材料皆以彈性模型描述之。在分析時導入全域/局部有限元素分析法及有限網格區域法，以有效改善網格分割造成結果準確性及收斂性的問題。並透過支撐點激勵法，將掉落測試時之接觸撞擊過程，轉換為等效支撐點激勵負載，以簡化分析。
在本文中考慮錫球之上、下墊片半徑、高度、材料，印刷電路板之楊氏係數、質量密度、厚度，基板之楊氏係數、厚度、錫球配置、構裝尺寸，晶片之尺寸、厚度，封膠之楊氏係數、厚度等因子，進行單一因子分析，以評估各因子對構裝結構抗衝擊可靠度的影響，然後將上述各因子利用田口品質設計，建立直交表進行實驗，並經誤差統合，找出最佳化的參數組合，以提升TFBGA構裝體之可靠度。 由單一因子分析結果顯示， 藉由減少晶片厚度、減少上錫球墊半徑、增加下錫球墊半徑、減少錫球配置及構裝尺寸、減少基板厚度、減少封膠厚度、減少封膠楊氏係數及含鉛錫球合金(Sn-37Pb)，皆能有效提高TFBGA構裝體可靠度。最後，利用田口品質工程所得最佳製程參數之錫球於印刷電路板側交界面上正向應力平均值為80.9Mpa，而原始製程參數設計為189.74Mpa，減少57%對提高抗衝擊能力有明顯之改善。

In recent years, the consuming electronic products have been developed with the tendency of less weight, miniature and portability. The failure of such mobile electronic devices usually results from the drops onto the ground during the shipping processes or the neglect under user’s operating. Thus solder ball is the most fragile part in an electronic package. The solder joints made of lead-free material are harder and crisper than those made of lead-contained materials so as to be easily broken due to the impact loading which absorbs the impact energy and leads to the malfunction of the package. Therefore, the improvement of the reliability of the solder ball made of lead-free material under an impact loading becomes a popular research issue. This study applies ANSYS 10.0 software for analysis. Based on JEDEC standard, TFBGA is loaded by a peak acceleration of 1500G at 0.5ms pulse duration. The solder ball is assumed as an elastoplastic model while other components are assumed to be linear elastic. Both the global/local finite element method and the finite grid region method are introduced to improve the accuracy and the convergence during the meshing process. Meanwhile the contact impact process during the dropping test is translated into the effective support excitation load on the PCB through the support excitation scheme to simplify the analysis. The single-factor experiment is conducted to predict the impact on the reliability of TFBGA in which the factors considered include upper pad radius, lower pad radius, standoff and material of the solder ball, the Young’s Modulus and mass density and thickness of the PCB, the Young’s Modulus and thickness of the substrate, the layout of the solder ball, the size of the package, the size and thickness of the die, the Young’s Modulus and thickness of the compound. Moreover, the Taguchi Method is applied to establish an orthogonal chart for the experiment and to minimize the deviations so as to obtain an optimal parameter combination and upgrade the reliability of the TFBGA package.
The result of the single-factor analysis shows that the reliability of the TFBGA package can be improved by reducing the thickness of the die, the upper pad radius of the solder ball, the layout of the solder ball, the
size of the package, the thickness of the substrate, the thickness and the Young’s Modulus of the compound and increasing the upper pad radius of the solder ball and the lead-contained material of the solder ball. Finally, by an optimal parameter design of the Taguchi Method, the average stress of the solder ball at PCB side surface becomes 80.9Mpa which shows a 57% reduction compared to the original stress of 189.7Mpa. As a result, the impact reliability of the TFBGA package has been significantly improved.

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