本研究旨在探討0.0050wt.%、0.0100wt.%、0.0150wt.%對 Sn-1.5Ag-0.7Cu (SAC157)低銀無鉛銲料顯微組織與硬度、強度、延性等機械性質產生之影響，觀察150℃，225小時高溫熱儲存試驗前後銲料性能之變化，並與未添加B之SAC157銲料進行比較。
實驗結果顯示當SAC157添加B元素後，銲料組織分布隨B添加量上升而逐漸緻密，且在高溫熱儲存試驗後添加B之銲料中共晶組織可保持原有結構，經掃描式電子顯微鏡與能量色散X-射線光譜技術分析共晶組織形貌與成分，發現B添加使共晶組織中主要強化相Ag3Sn形貌發生轉變，隨B添加量上升由SAC157中板片狀逐漸細化為0.0150wt.%添加量下之細長條帶狀，提升散布強化效果。而觀察熱儲存前後銲點界面金屬間化合物(Intermetallic Compound, IMC)層形貌與厚度變化可知，B添加可以減緩迴銲時IMC層Cu6Sn5晶粒粗大現象，獲得較平坦之IMC層形貌，並降低迴銲後IMC層厚度，在熱儲存期間亦可抑制IMC層成長速度，提升材料抗熱性。
機械性質方面，對共晶組織進行維克氏硬度試驗之結果顯示，B添加對共晶組織內金屬間化合物造成之細晶效果可提升其散布強化能力，使銲料硬度隨B添加量增加而上升，並抑制熱儲存後因金屬間化合物粗大化而造成之硬度下降。而銲點剪切試驗亦顯示銲點強度與延伸量在添加B後均較SAC157高。
綜合上述實驗結果，B添加可改善銲料微結構分布與形貌，強化銲料硬度、強度、抗熱性等性能表現，進而提升銲點可靠性。

The purpose of this study was to investigate the effect of boron addition (0.0050、0.0100、0.0150wt.%) on microstructure, microhardness, strength and ductility of low-silver lead-free solder Sn-1.5Ag-0.7Cu (SAC157). Observed the differences in solder properties before and after the high temperature heat storage test (150 ℃, 225hours) and compared with boron-free SAC 157 solder.
The experimental results show that the microstructure distribution of solder becomes finer and denser with the increase of B addition, and the eutectic structure of the solder added with B can maintain the original structure after the high temperature heat storage test. Analyzed the morphology and composition of the eutectic structure by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy(EDS), it was found that the addition of B changes the morphology of the main strengthening phase Ag3Sn in the eutectic structure. As the increased of B addition, the flake-like Ag3Sn in SAC157 was gradually refine into a thin strip-like morphology in 0.0150 wt.%B added solder. Observing the morphology and thickness of the Intermetallic Compound (IMC) layer at the solder joint interface after thermal storage, it was found that the addition of B can reduce the coarsening of Cu6Sn5 grains during reflow, obtain a flat IMC layer morphology, and reduce the thickness of the IMC layer. During the thermal storage, the growth rate of the IMC layer can also be suppressed, improve the heat resistance of the solder.
In terms of mechanical properties, the Vickers hardness test on the eutectic structure shows that refinement effect of the intermetallic compound in the eutectic structure can enhance the dispersion strengthening ability, increase microhardness and restrain the microhardness decrease after thermal storage. The shear test also showed that shear strength and ductility of the solder joint were higher than SAC157 after adding B.
Based on the results, the addition of B can improve the distribution and morphology of the solder microstructure, enhance the hardness, strength, heat resistance performance of the solder, thereby improving the reliability of the solder joint.

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