本研究旨在探討添加Sb元素(0.5、1.0、1.5、2.0wt.%)對Sn-1.5Ag-0.7Cu(SAC157)低銀無鉛銲料熔點、微結構及機械性質的影響。利用高溫熱儲存試驗(150℃，225hrs)對銲料的抗熱性進行評估，並與商業化無鉛銲料Sn-3.0Ag-0.5Cu(SAC305)作比較。
實驗結果顯示，Sn-1.5Ag-0.7Cu-xSb銲料熔點隨著Sb添加量的增多而升高，固液區間亦逐漸上升。添加Sb後，SAC-0.5Sb的微觀結構與SAC157相似仍含有網狀共晶組織且部分Sb會固溶於析出物中形成Ag3(Sn,Sb)和Cu6(Sn,Sb)5。隨著Sb含量增加，網狀共晶組織逐漸瓦解，析出物Ag3(Sn,Sb)的形貌從細長帶狀變為長條板片狀。高溫熱儲存後，Sb的固溶量增加，銲料析出物有所粗大。此外，添加Sb可通過細化晶粒和阻礙Sn原子擴散而減小SAC銲料IMC層的生長。SAC-1.0Sb擁有最小IMC層厚度，而隨著Sb添加量增多IMC層的厚度有所回升。高溫熱儲存後，銲料IMC層厚度有所增加，但添加Sb之銲料增長幅度較小，表明Sb可抑制高溫下SAC銲料IMC層生長。
機械性質方面，銲料的硬度與剪切強度均隨著Sb添加量的增多而升高。高溫熱儲存後，所有銲料的硬度均有所下降，但添加Sb之銲料下降幅度較小，顯示具有較好的抗熱性。在低週疲勞試驗中，SAC-0.5Sb、SAC-1.0Sb的疲勞壽命較SAC305、SAC157有所提升，原因主要為Sb具有固溶強化的作用。此外，當Sb添加量小於1.0wt.%時，銲料IMC層較薄，裂紋主要從銲料內部生長。隨著Sb添加量增多，IMC厚度增加，促使裂紋向IMC層生長形成混合破壞模式或IMC層破壞模式，導致銲料疲勞壽命降低。而高溫熱儲存後，銲料強度降低，IMC層厚度增長，界面粗糙度升高，導致銲料易於IMC層處產生脆性斷裂，降低整體疲勞壽命。
綜合銲料固液區間、微結構、界面層量測與疲勞壽命，研究結果顯示Sb添加量為0.5-1.0wt.%時可提升低銀SAC銲料之性能。

The purpose of this study is to investigate the effect of Sb addition (0.5, 1.0, 1.5, 2.0wt.%) on melting point, microstructure and mechanical properties of Sn-1.5Ag-0.7Cu (SAC157) low silver lead-free solder. Thermal resistance of the solder is evaluated using a thermal storage test (150℃, 225hrs) and compared with commercial lead-free solder Sn-3.0Ag-0.5Cu (SAC305).
The experimental results show that the melting point of Sn-1.5Ag-0.7Cu-xSb solders increases with the addition of Sb, and the solid-liquid interval increases gradually. After adding Sb, the microstructure of SAC-0.5Sb is similar to that of SAC157, which still contains network eutectic structure, and some Sb will dissolve in precipitates, forming Ag3(Sn,Sb) and Cu6(Sn,Sb)5. With the increase of Sb content, the eutectic structure of the alloy gradually disintegrates, and the morphology of Ag3(Sn,Sb) changes from strip-like to flake-like. After thermal storage, the solid solution of Sb is increased and the precipitates become coarse. Moreover, the addition of Sb can reduce the growth of SAC solder IMC layers by refining the grains and hindering the diffusion of Sn atoms. SAC-1.0Sb has the minimum IMC layer thickness, and as the amount of Sb increases, the thickness of the IMC layer picks up. After thermal storage, the thickness of solder IMC layer increases, but the growth rate of solder with Sb addition is small, indicating that Sb can inhibit the growth of SAC solder IMC layer at high temperature.
In terms of mechanical properties, the hardness and shear strength of solder increase with the addition of Sb. After thermal storage, the hardness of all solders decreases, but solders with Sb addition decrease slightly which show better thermal resistance. In the low cycle fatigue test, the fatigue life of SAC-0.5Sb and SAC-1.0Sb is higher than that of SAC305 and SAC157. The main reason is that Sb has the effect of solid solution strengthening. In addition, when the amount of Sb addition is less than 1.0wt.%, the solder IMC layer is thinner, and the crack mainly grows from the internal solder. As the amount of Sb increases, the thickness of IMC layer increases, which results in the growth of crack in the IMC layer, causing the mixed fracture mode or the IMC fracture mode, depressing the fatigue life of solder. However, after thermal storage, the strength of solder decreases and the thickness of IMC layer, the roughness of the interface increases, which lead the initial crack to the brittle IMC layer, and reduces the overall fatigue life.
Taking all the results into consideration, the addition of Sb at 0.5-1.0wt.% can better improve the properties of low silver SAC lead-free solder.

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