本研究目的為藉由觀察在電遷移效應下的Zn-25Sn合金微結構及機械性質、拉伸性質變化探討Zn-25Sn合金通電後造成性質變化的機制，將Zn-25Sn合金施加3000-5000 A/cm2之電流密度通電2-60分鐘後，利用液態氮急速冷卻試片以維持通電處理後之微結構。實驗結果顯示隨電流密度增加，試片的硬度及電阻率皆在通電5分鐘時達到最大值，但隨著通電時間增長，硬度與電阻率有下降的趨勢，此外，通電後拉伸數據顯示隨通電時間增長時變化並不明顯。通電後XRD繞射分析結果顯示，通電後主要結晶面之應變量雖不大，但可觀察到其繞射峰積分面積有所下降，因此推斷電流對材料晶格造成破壞。晶粒尺寸的數據結果顯示，在通電過後晶粒有微幅度的上升，但變化量仍在誤差範圍內。由於沒有相變、析出物的產生，也沒有觀察到固溶行為及晶粒細化之現象，因此歸納出硬度變化的主因應為應變強化，綜合分析析出物的產生、固溶行為及晶粒細化現象，試片體積在通電過後沒有明顯變化，推論影響電性的主因為晶粒結構重新排列與差排密度的變化，但仍須進一步的實驗分析確認。

This study investigated the effect of current stressing on the mechanical properties, electrical properties and microstructure of high temperature Zn-25Sn solder alloys. The Zn-25Sn specimens were subjected to 3000~5000 A/cm2 direct current stressing for 2~60 mins and then quenched in liquid nitrogen to freeze the microstructure.

The results showed that the magnitudes of hardness and resistivity reached the maximum after 5 mins of current stressing, and declined with prolonged current stressing. The tensile properties and the grain size did not have an obvious variation. The XRD results indicated that the peak intensity of main crystal planes would decrease after current stressing, and it might be attributed to the lattice distortion induced by current stressing.

The variation in microstructure may affect the properties of Zn-25Sn. Since there was no phase transformation, precipitates, solid solution behavior and grain refinement, it was concluded that the main mechanism of the hardness change was strain strengthening. The volume change of the specimen after current stressing is not significant. The resistivity was affected by the rearrangement of grain and the change of dislocation density, but it should be confirmed by further experiment.

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