本研究主要探討添加不同的B含量(0.0010wt.%、0.0025wt.%、0.0050wt.%)對於Sn-1.5Ag-0.7Cu-0.05Ni(SAC157-0.05Ni)低銀無鉛銲料的微結構及機械性質影響。以及高溫熱儲存下(150℃，225hrs)銲料的抗熱能力，研究結果與目前Sn-1.5Ag-0.7Cu(SAC157)低銀銲料進行比較。
研究結果顯示SAC157-0.05Ni銲料內添加B元素後，共晶組織有變細緻且密集之趨勢，特別在添加0.0025wt.%時趨勢最為明顯，強度硬度隨之升高，後續使用SEM進行微觀分析，發現其細緻共晶組織主要為Ag3Sn，隨著B添加量增加其Ag3Sn形態也隨之改變，添加0.001wt.%時銲料Ag3Sn主要型態為板片狀，添加至0.0025wt.%時，銲料Ag3Sn型態轉變為長條帶狀，而當添加量至0.005wt.%時Ag3Sn維持長條帶狀，但於板片Ag3Sn附近發現含B的四方柱體相， IMC層研究發現，IMC層厚度隨著B添加，厚度有降低趨勢，時效試驗顯示B的添加可阻礙Sn擴散進入IMC層形成新的(Cu,Ni)6Sn5，促使(Cu,Ni)6Sn5在時效下厚度僅有微幅的增加，研究成果證實B可抑制高溫下SAC157-0.05Ni銲料IMC層的生長。
機械性質方面，經由銲點剪切試驗可得知，當銲料添加B後，延性皆有明顯提升的趨勢，時效前後的低週疲勞試驗結果顯示，添加B的銲料疲勞壽命皆較SAC157及SAC157-0.05Ni有所提升，原因主要為添加B有晶粒細化的作用，可使銲料擁有較佳的延性，使裂紋生長緩慢，且B的添加可有效抑制熱儲存後IMC層的成長及減緩析出物粗大化現象，因此有助於提升低銀SAC157-0.05Ni銲料的機械性質及疲勞壽命。

The The purpose of this study was to investigate the effects of addition of boron element (0.0010, 0.0025, 0.0050wt.%) on the microstructure, and mechanical properties of Sn-1.5Ag-0.7Cu-0.05Ni (SAC157-0.05Ni) low-silver lead-free solder. The heat resistance of the solder was evaluated using a high-temperature heat storage test (150°C, 225 hrs) and compared with boron-free solder Sn-1.5Ag-0.7Cu (SAC157).
When B element is added to SAC157-0.05Ni solder, the eutectic structure tends to be fine and dense, especially when 0.0025 wt.% of B is added. SEM is used for microscopic analysis. SEM micrographs showed that the fine eutectic structure is mainly precipitate Ag3Sn. The morphology of Ag3Sn changes with the addition of B. When 0.001wt.% is added, the main form of solder Ag3Sn is plate-like. When the amount is increased to 0.0025wt.%, Ag3Sn’s morphology changes to a long strip shape, while it maintains a long strip shape when boron addition reaches 0.005 wt.%. While observing microstructure of SAC157-0.05Ni-0.005B, a tetragonal column phase containing B, namely Cuboidal, is found near plate-like Ag3Sn. In terms of IMC thickness, it is found that addition of B can hinder the diffusion of Sn into the IMC layer and reduce the growth of (Cu, Ni)6Sn5 after aging, indicating that B can suppress the growth of the IMC layer of SAC157-0.05Ni solder at high temperature.
In terms of mechanical properties, it can be seen from the solder joint shear test after boron addition, the ductility of the solder is obviously improved. The low cycle fatigue test results before and after the heat storage show that the fatigue life of the solder added with B is better than that of SAC157 and SAC157-0.05Ni, mainly because B has the effect of grain refinement, which can make the solder having better ductility and slower crack growth. In addition, the addition of B can effectively inhibit the growth of the IMC layer after heat storage and coarsening of precipitates. In conclusion, addition of boron to solder SAC157-0.05Ni significantly improve its mechanical properties and fatigue life.

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