本研究探討不同初始晶粒尺寸的純錫薄帶經循環通電後其電性與機械性質的變化，並以背向散射電子繞射技術(Electron Backscatter Diffraction, EBSD)與高解析度穿透式電子顯微鏡(High Resolution-Transmission Electron Microscope, HR-TEM)觀察試片之微結構，以瞭解不同初始晶粒尺寸之純錫薄帶經通電後材料性質變化之機制。本研究將純錫薄帶分別以60℃、100℃及140℃進行退火熱處理，並且皆以6000A/cm2的電流密度針對三種不同初始晶粒尺寸的純錫薄帶進行循環通電處理。本研究發現初始晶粒尺寸較大的試片經通電後會越晚發生再結晶，其原因推測為初始晶粒尺寸越大的試片，晶粒內能容納的差排數量較多，相同通電條件所產生的差排密度較小，因此需要通電較長時間達到再結晶所需的臨界差排密度。本研究亦發現造成純錫薄帶通電後片電阻值變化的主要原因為晶粒尺寸，且隨著初始晶粒尺寸越大，片電阻值上升的幅度越大。此外，不論初始晶粒尺寸為何，造成純錫薄帶通電後微硬度值變化的主要機制皆為晶界強化，且隨著初始晶粒尺寸越大，晶界強化的影響亦隨之增加。

The present study investigated the changes of electrical and mechanical properties of the pure Sn strips with different initial grain sizes after the cyclic direct current stressing treatment. Electron Backscatter Diffraction (EBSD) and High Resolution-Transmission Electron Microscope (HR-TEM) was used to investigate the microstructure of the specimens, and the mechanism of the material properties variation. The pure Sn strips were annealed at 60°C, 100°C and 140°C, respectively. The specimens with three different grain sizes were subjected to a cyclic direct current stressing treatment at room temperature with 6000 A/cm2 for the duration time (denoted as tD) and cycle number (denoted as n) designed by the experiment. The experimental results showed that the specimen with larger initial grain size would need longer electrical treatment to initiate recrystallization. The behavior was ascribed to the smaller dislocation density generated in the larger grains under the same electrical current stressing conditions. It takes a longer time to achieve critical dislocation density required for recrystallization. This study also found that the sheet resistance variation of the pure Sn strips subjected to electrical current stressing was governed by grain size. The larger the initial grain size, the greater the increase in the sheet resistance value. In addition, no matter what the initial grain size is, the main mechanism that causes the change of the microhardness value of the pure Sn strips after electrical current stressing treatment is grain boundary strengthening. The influence of grain boundary strengthening increases with the increase of the initial grain size.

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