本研究係探討共晶錫鋅球柵式陣列構裝銲錫接點，於通電條件之下，電遷移效應(Electromigration)對於銲錫接點結構產生之影響，本實驗試片以兩個接點為一組進行通電，電子流方向互為相反，另選一接點不通電，只進行高溫時效實驗以作為通電實驗之對照組，進而瞭解通電對於銲錫接點為結構之影響。實驗前試片先研磨拋光至欲進行實驗之接點的一半，實驗是在環境溫度120℃下進行，通電接點通以0.75A電流，換算成平均電流密度為3.06x103 A/cm2，於不同通電時間將實驗暫停，將試片取出後，利用掃瞄式電子顯微鏡(SEM)進行表面微結構之觀察，以及藉由能量散佈光譜儀(EDS)分析其組成。
在高溫環境下發現新的富鋅相在表面產生，這是由於鋅傾向往表面擴散形成氧化鋅，擴散至表面之鋅原子會聚集形成新的富鋅相，由於鋅原子擴散受到電子風力作用，所以在不同電子流方向接點中形成之位置也不相同。另外，鋅原子會傾向擴散至界面與鎳層發生界面反應以降低自由能，當電子流方向與鋅原子往界面方向擴散相同時，會加速鎳鋅界面反應；反之，當方向相反時則會抑制界面反應，鎳鋅界面反應的產物為Ni5Zn21。在通電實驗中，由於基板與電路板中之銅線路尺寸大小差不多，不會造成銲錫接點中明顯熱梯度的產生，所以在本實驗中並不考慮熱遷移效應(Thermomigration)對銲錫接點之影響。

The present work investigated the behavior of electromigration in the Pb-free eutectic Sn-9Zn BGA (Ball Grid Array) solder joint at 120℃. In order to observe electromigration in situ, the joints were cross-sectioned in half, and polished before the current stressing. The average current stressing density applied was 3.06x103 A/cm2. The solder joint were examined at specified period of current stressing using SEM (Scanning Electron Microscope) and EDX (Energy Dispersive X-ray).
The electron wind force affected the diffusion direction of the Zn atoms. At higher ambient temperature, the Zn diffused toward the free surface, combining together to form new Zn rich phase and transforming into ZnO. The position of new Zn rich phase was different in the opposite electron direction joint. Besides, the Zn atoms diffused to the interface in order to react with the Ni layer. When the electron wind force direction was the same as the diffusion direction of the Zn atoms, the Ni-Zn interfacial reaction would be accelerated, whereas the interfacial reaction would be inhibited. Ni5Zn21 was formed during interfacial reaction. Because no temperature gradient exists across the solder joint, thermomigration behavior did not come into picture in the present study.

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