1990年代以後，由於鉛具毒性加上嚴格立法禁止鉛基銲料的使用，促進了無鉛銲料，例如錫-銀-銅（SAC）合金的發展。然而，錫-銀-銅合金依然存在許多問題或未知特性，透過添加第四種合金─鉍可改善錫-銀-銅銲料之物理及化學特性，如熔點、機械性質、可靠度等。銲料的可靠性在電子封裝中起著至關重要的作用，故鉍的添加如何影響銲錫球之微結構與機械性質等引起廣大之研究興趣。
本研究針對通電前及通電後不同鉍添加量之SAC305-Bi銲錫球進行分析，利用通電實驗模擬銲錫球真實應用至故障之情形。首先，透過EDS成分分析及EBSD結晶結構分析來完成相鑑定。接著分析通電前後不同鉍添加量銲錫球之形貌、介金屬化合物厚度及晶粒尺寸等，並以合理之擴散機制解釋。最後，利用奈米壓痕測輛銲錫球基底之機械性質，並以合理之機制解釋。探討鉍添加對銲錫球顯微結構及機械性質造成之影響。
實驗結果顯示，鉍添加能使通電前銲錫球基底之晶粒細化並能抑制介金屬化合物Ag3Sn及Cu6Sn5。但鉍的添加卻會促進通電過程中之電遷移現象，使介金屬化合物Cu6Sn5及Cu3Sn之成長速率上升。鉍添加也會使銲錫球基底之硬度提高。

In the semiconductor industry, the reliability of solder balls plays an important role. Electromigration(EM) is one of the important tests to measure the lifetime of solder balls in microelectronic packages. In this study, the microstructure, mechanical property and the atomic diffusion behavior of SAC305-Bi solder balls were investigated. The microstructure has been characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and electron backscattering diffraction (EBSD).Nanoindent was used to measure the mechanical properties of tin matrix. The growth rate of Cu6Sn5 and Cu3Sn with 2 and 3 wt% bismuth-doping are larger than that of 1wt% bismuth-doping. Bismuth addition hardens the tin matrix.

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