Cu 5μm 與 Cu 5μm╱Ni 3μm 金屬墊層覆晶銲錫凸塊之電遷移研究

Abstract

在消費性電子產品走向輕、薄、短、小的趨勢中，需要高密度銲錫接點輸入/輸出數目。覆晶封裝是目前在高電流密度IC元件上的重要封裝之一。隨著積體電路之元件密度與功能迅速提升，封裝元件的操作溫度與電流密度亦持續攀升，銲錫接點的可靠度已經成為重要的課題。近來因為環境保護的考量，在封裝上無鉛銲錫的使用逐漸地取代傳統的有鉛銲錫。 本研究探討在銅鎳墊層與銅墊層的無鉛覆晶錫銀銲錫接點於140℃的溫度下，通以電流0.8A，之電遷移行為及其破壞機制。利用凱文結構來觀測銲錫凸塊在電遷移下電阻變化情形，不同金屬墊層所造成的破壞機制將個別被討論。

As the consumer electronic products move toward lighter, slimmer, shorter and smaller, we need higher solder input/output joint density. Flip Chip Technology is one of the most important packaging methods for high current density IC devices, Since the current density and the operation temperature in the packaged devices rise substantially with the increase in device density and functionality for integrated circuits, the reliability of solder joints has become a critical issue on device reliability. In Flip-Chip packaging, lead-free solders are replacing traditional SnPb solders gradually due to environmental concern . In this study, we fabricated two kinds of Pb-free SnAg solder joints with under-bump-metallizations (UBMs) of 5-μm Cu/3-μm Ni and 5-μm Cu. Both sets of solder joints were subjected to electromigration tests by 0.8A at 140℃.The electromigration behavior and the mechanism which causes the damage of the bumps were monitored at various stages of electromigration. The Kelvin probes were employed to monitor the changes for the bump resistance during the electromigration tests and the mechanisms which cause damage to the joints were discussed for these two different solder joints, respectively.