高鉛和共晶銲料之介面電遷移研究

Abstract

本論文利用Si 特有之V 型凹槽，迴流共晶與高鉛兩種銲錫合金，來模擬複合式銲料之結構，並研究電流方向、通電溫度對電遷移效應的影響。 藉由此種方法，我們發現通電方向的不同，會有不同的電遷移現象。我們所使用的電流密度均固定為5.7×104A/cm2，如果電子流方向是由共晶流到高鉛的話，會比電子流由高鉛流到共晶更快損壞而形成斷路，且其破壞點均是發生在共晶銲料靠陰極端處。對溫度效應來說的話，在150°C的電遷移效應較室溫及80°C來的明顯且快速，會在約一天左右就產生巨大的孔洞而斷路。另外在150°C 下之主要擴散元素為鉛而在室溫及80°C 之下則為錫。 比較特別的是在150°C之下不管有無通電，在高鉛及銅的介面處均會有一約幾micron的小細縫產生，推測應是高鉛與銅之熱膨脹係數差異所造成，但是並不嚴重到影響其電性。

The electromigration behavior in high-Pb/eutectic composite solder lines were studied in this experiment. Using Si V-grooves, we simulated the composite solder structure by reflowing the two solders into it. Electromigration effect was studued as a function of temperature, and stressing direction. Various of electromigration damage was observed when current direction or stressing temperature changed. If the electron flux was passed from the eutectic solder side to the high-Pb solder side, hillocks formed at the eutectic/high-Pb solder interface and the voids appeared at the cathode side. When the electron flux was passed from the high-Pb to the eutectic solder side, the hillock accumulated at the anode side near the Cu/eutectic solder interface, and voids were formed at the cathode side both at room temperature and 150°C. We observed a trench along Cu/high-Pb interface whether stressing or not at 150°C. The depth is about several microns. But, the trench is not found at Cu/eutectic solder interface; it may due to the eutectic solder is more ductile than high-Pb solder.