銲錫材料在使用時可能因機械振動而造成損害，且銲點是在通電狀態下運作，因此銲錫材料在通電處理前後之機械性質變化值得進行探討。故本實驗研究通電處理對Sn-9Zn-xCu(x=0, 0.2, 0.5, 0.7, 1.0wt%)無鉛銲錫合金之振動破壞阻抗影響。

　　在通電前試片之金相觀察顯示，隨著Cu含量的增加，組織中散佈的共晶富Zn相隨之減少，Cu-Zn化合物(CuZn5)及富Sn相則增加。在高Cu含量試片(0.7Cu及1.0Cu)可觀察到大量樹枝晶狀初晶β-Sn。通電前之振動試驗結果顯示，少量的添加Cu會使振動性質變差，當Cu含量達0.7wt%以上時，將得到較佳的振動性質。而添加Cu元素所形成之初晶富Sn相，其層狀變形現象會主導制振性及等出力值條件下之振動破壞阻抗。此外，由SEM觀察得知晶出第二相(富Zn相、富Sn相和CuZn5)在本合金系統中對裂縫傳播方面有正面的影響。

　　在通電後之試驗方面，為簡化實驗，本研究選擇振動性質較佳的1.0Cu試片進行通電試驗，並探討其因電流效應引起的機械性質變化。拉伸試驗結果顯示，拉伸強度有隨通電時間增加有先上升而後下降的趨勢，通電7小時強度最高；到通電11小時則有下降現象。和同時間及溫度(120℃)之熱處理試片比較，強度上升可能是因電流效應所影響。在振動試驗方面，隨著通電時間的增加，試片有較高的共振頻率及初始偏移量，使得裂縫有較高驅動力前進而導致振動壽命下降。顯示通電處理會使得試片振動破壞阻抗下降。

　Solder joints are applied usually in the electric surrounding and may suffer damage due to mechanical vibration. So it is worthy of looking into the properties under different electrical current conditions. The objective of present study is aimed on the current effect for vibration fracture resistance in Sn-Zn-XCu (X=0.2, 0.5, 0.7, 1.0wt%).

　Samples with no current applied observed that rich-Zn phases decreased meanwhile the Cu-Zn compounds and Sn-rich phases became much more with increasing Cu element additions. At high Cu content (0.7, 1.0wt%), a plenty of dendritic primary Sn-rich appeared in the matrix. Then specimens followed by vibration test. Vibration properties was deteriorated with a little Cu additions but it was improved when Cu content over 0.7wt%. The layer-like deformation of the primary Sn-rich phase was the major factor affected the vibration resistance of damping capacity and constant force conditions. Otherwise, the second phase (contain: rich-Zn, rich-Sn and CuZn5) had positive contribution to crack propagation.

　For simplicity, the 1.0wt% Cu samples was selected to discuss the current effect inasmuch as its proper vibration properties. The current effect was carried out by tensile and vibration test. With increasing duration the current applied the sample attained greater tensile strength initially but got worse subsequently, its optimum strength was reached at 7hr then degenerated at 11hr. To compare with modify sample, i.e. heat treatment in 120℃ and hold for the same time with no employee current. The enhance strength may ascribed to the current effect. In the aspect of vibration experiment, specimens achieved a greater resonance frequency as well as the initial deflection which promoted cracks propagated forward easily. In conclusion, specimens experienced the current treatment resulted in decreasing the vibration fracture resistance.

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