使用在共晶錫鉛銲錫薄膜的電遷移效應研究複合式晶鬚之成長

Abstract

本實驗中我們利用Blech 結構，同時配合聚焦離子束(Focus Ion Beam)蝕刻製作出不同長度之錫鉛銲錫膜來進行晶鬚成長之研究與 分析。實驗所製作之銲錫薄膜厚度約略為2.3 μm，經電流測試後在 試片中發現了晶鬚成長。之後我們利用聚焦離子束(Focus Ion Beam) 與穿透式電子顯微鏡(Transmission Electron Microscope)分析其晶鬚 之成長方向與成份分佈。 在電流密度5 × 104 A/cm2 的驅使下，即使在100oC 的環境我們 仍可在共晶錫鉛薄膜中發現晶鬚的成長。據先前文獻指出於較低的 壓縮應力下，鉛將吸收部分應力，因此無晶鬚成長。然而在我們的 實驗結果中，晶鬚會成長於5 × 104 A/cm2 之較大電流密度。依據實 驗觀察發現，成長之晶鬚為複合式晶鬚，且成長出之複合式晶鬚大 部分皆是以鉛相部份先行成長，爾後出現錫相部份。根據穿透式電 子顯微鏡繞射圖形分析，共晶錫鉛成長之複合式晶鬚在鉛相晶鬚部 份之成長方向為[1 1 2]、[2 1 1]、[1 1 0]與[1 1 1]。

By using Blech structure, we study the whisker growth and analyze composite whiskers. In this study, eutectic SnPb solder stripes were prepared on a Ti metal layer by reflowing process. Focused ion beam (FIB) was employed to fabricate the blech stripes and to prepare cross-sectional specimen for analysis by transmission electron microscopy (TEM). Eutectic SnPb solder stripes with various lengths were prepared, and the thickness of the solder stripes was approximately 2.3 μm. Under electromigration at 5 × 104 A/cm2 and 100 °C, we have grown composite Pb/Sn whiskers, in which a whisker of Pb grows first , followed by the growth of a whisker of Sn. In some cases, small Sn islands are embedded in the Pb whiskers. We propose that under low stress the Pb will be able to absorb the stress and reduce the driving force of spontaneous Sn whisker growth from the eutectic SnPb solder. III But under a larger driving force provided by electromigration, Pb and Sn whiskers can grow. The orientation of the Pb part in composite whisker is [1 1 2]、[2 1 1]、[1 1 0] and [1 1 1].