本研究旨在探討B添加量在0.015 wt.%、0.020 wt.%、0.025 wt.%時，對低銀無鉛銲料Sn-1.5Ag-0.7Cu (SAC157)之顯微組織、固液相區間、硬度、強度，及銲料延性等機械性質的影響，研究並觀察高溫熱儲存在150℃，225小時下之銲料及銲點性能變化，並與未添加B之SAC157銲料比較。
研究結果中發現，添加B銲料之固液相區間會微幅上升，而在顯微組織變化中SAC157銲料添加B對組織有細化之效果，銲料之共晶組織由鬆散狀變為緻密網狀結構，並在高溫熱儲存下仍能保持原有結構。而在掃描式電子顯微鏡(SEM)觀察下，發現B顆粒散佈於初析β-Sn與共晶組織內部，使共晶組織中金屬間化合物Ag3Sn型貌由分散之大板片狀轉變為緻密之細長條狀，且有抑制Cu6Sn5生長之功效，使共晶組織組成變為以Ag3Sn為主，而在0.025 wt.%B添加下組織型變則趨於穩定，整體散佈強化效果有所提升。而觀察熱儲存前後銲點之IMC層形貌與厚度變化，發現B添加具有減緩IMC層中Cu6Sn5晶粒粗大效果，使IMC表面趨於平坦且厚度降低，並在熱儲存過程中降低原子擴散速率，及抑制IMC層成長，使銲點抗熱性提升。
在硬度觀察中，整體銲料硬度由較軟之初析β-Sn所主導，隨B添加量上升使金屬間化合物散佈強化效果提高而有硬度提高之趨勢，熱儲存晶粒粗大現象被抑制減緩而使硬度下降幅度趨緩。在銲點剪切試驗中亦發現B添加能使銲點延性、韌性提高，使銲點之可靠度提升。
綜合以上實驗結果，SAC157銲料添加B可改善銲料之顯微組織，使金屬間化合物之散佈強化效果提升，進而強化銲料之硬度、延展性，及韌性等機械性質，使銲點之可靠度進一步提升。

This study tried to figure out the difference when the boron addition amount is 0.015 wt.%, 0.020 wt.%, and 0.025 wt.% on microstructure, microhardness, strength, ductility, and temperature gap between solidus and liquidus point of Low Silver Lead-free Solder of Sn-1.5Ag-0.7Cu(SAC157). Observed the differences in solder properties through the high temperature heat storage test (150 C, 225 hours).
The phase transition temperatures of the B added solder will increase slightly, and the addition of boron in SAC157 solder has the effect of refining the structure, and the eutectic structure of the solder changes from loose to net-work structure. Under the Scanning Electron Microscope(SEM) observation, it was found that the boron particles were dispersed in the primary β-Sn and the eutectic structure, so that the morphology of the intermetallic compound Ag3Sn in the eutectic structure changed from a dispersed large plate to a dense one. And the structure change tends to be stable with the addition of 0.025 wt.% B, and the overall dispersion strengthening effect is improved. After thermal storage, it is found that the addition of boron has the effect of slowing down the coarsening of Cu6Sn5 grains in the IMC layer, making the IMC surface smooth, and reducing the atomic diffusion rate during thermal storage, so that the heat resistance of the solder joint is improved. In the Vickers hardness test, the overall solder hardness is dominated by the softer primary β-Sn. As the amount of boron increases, the dispersion strengthening effect increases and the hardness increases. With boron particle suppress the grain growth, the hardness decrease slow down after thermal storage. In the shear test, it was also found that the addition of boron can improve the ductility and toughness of the solder joint, and improve the reliability of the solder joint.
Based on the above experimental results, the addition of boron in SAC157 solder can improve the microstructure of the solder, enhance the dispersion strengthening effect, and then strengthen the mechanical properties of the solder, such as hardness, ductility, toughness, and further enhance the reliability of the solder joint.

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