本研究主要目的為探討不同In添加量(1,2,3,5,10wt%)對Sn-1.5Ag-0.7Cu-0.05Ni低銀無鉛銲料對銲點性質的影響。實驗內容包含顯微組織、剪切試驗、硬度分析以及IMC層厚度量測以及熱儲存150℃(100、225hrs)前後觀察顯微組織變化、硬度以及IMC層量測觀察。
根據實驗結果顯示，In的添加能夠固溶於β-Sn、Ag3Sn、(Cu,Ni)6Sn5形成β-(Sn,In)、Ag3(Sn,In)、(Cu,Ni)6(Sn,In)5，又隨著添加量提升，β-Sn與析出物有逐漸粗大化的現象，共晶組織粗大化的現象也造成析出空間逐漸受到擠壓，形成較多的橢圓狀的Ag3(Sn,In)析出物，形貌也從長條狀逐漸轉變為短條狀甚至是橢圓顆粒狀。
在熱儲存前可以發現機械性質會隨In元素的添加隨之上升，隨著熱儲存時間的增加，各銲料之微硬度皆呈現下降的趨勢。In添加量在5wt%以下的銲料，其微硬度之變化相似，對抵抗軟化皆有一定的限度，但在添加量10wt%In的銲料卻在熱儲存225小時以後，微硬度出現較大幅下降的趨勢。在剪切試驗中，添加1wt%時，有提高剪切強度並也提升延性，而超過1wt%添加量，剪切強度雖固有提升，但延伸量下降，添加量越多，下降得更明顯並轉為脆性。IMC層厚度觀察，以添加1-3wt%In皆能抑制IMC層成長，超過1wt%，厚度逐漸上升，不管有無熱儲存，添加5wt%In以上時，IMC層厚度皆超過4μm，添加於10wt%時，更是高達6μm以上，實驗結果表明以1wt%的添加為最有效抑制IMC層生成。
綜合上述各項實驗結果，本研究以1wt%In的添加於SACN銲料是最佳參數，能夠提升機械性質並抑制IMC層厚度。

The main purpose of this study is to explore the effect of different Indium addition (1,2,3,5,10wt%) on the properties of solder joints of Sn-1.5Ag-0.7Cu-0.05Ni low-silver lead-free solder. The contents of the experiment include observation of microstructure, shear test, hardness analysis, and IMC layer thickness measurement, as well as observation of microstructure changes, hardness, and IMC layer measurement before and after heat storage at 150°C (100, 225hrs).
According to the experimental results, the addition of In can be dissolved in β-Sn, Ag3Sn, (Cu, Ni)6Sn5 to form β-(Sn,In), Ag3(Sn,In), (Cu,Ni)6(Sn,In)5. With the increase of In addition, β-(Sn,In), Ag3(Sn,In), (Cu,Ni)6(Sn,In)5 gradually become coarser. It causes the precipitation space of the eutectic structure to be gradually compressed and causes discontinuity, forming more elliptical Ag3(Sn, In) precipitates, the morphology has gradually changed from long strips to short strips or even oval granular shapes.
Before thermal storage, it can be found that the mechanical properties will be improved with the addition of In element. As the thermal storage time increases, the microhardness of each solder tends to decrease. The microhardness of solders with In addition below 5wt% has similar changes in microhardness and has a certain limit to resistance to softening. However, after 225 hours of heat storage for solders with 10wt% In addition, the microhardness decreases significantly trend. In the shear test, the addition of 1wt% increases the shear strength and also increases the ductility. If the addition amount exceeds 1wt%, the shear strength is inherently improved, but the elongation decreases. The more the addition, the more obvious the decrease, and then it turns to brittleness. Observation of the thickness of the IMC layer shows that the growth of the IMC layer can be suppressed by adding 1-3wt% In. The thickness of the IMC layer increases gradually when it exceeds 1wt%. Regardless of whether there is heat storage or not, the thickness of the IMC layer exceeds 4μm when the In is added above 5wt%. When the temperature is as high as 6μm or more, the experimental results show that the addition of 1wt% is the most effective way to suppress the formation of the IMC layer.
Based on the above experimental results, in this study, the addition of 1wt% In to SACN solder is the best parameter, which can improve the mechanical properties and suppress the thickness of the IMC layer.

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