15微米鎳/錫銀銲錫/鎳微凸塊之電遷移研究

Electromigration in Ni/SnAg/Ni Microbumps with 15μm Solder Height

李昱瑾(Yu-Jin Li) ； 陳智(Chih Chen)

《鑛冶：中國鑛冶工程學會會刊》 62卷2期 (2018/06) Pp. 74-78

https://doi.org/10.30069/MM.201806_62(2).0007

摘要

在本研究中，我們採用雛菊鏈狀結構（每個鏈結中有40個微凸塊）來做電遷移測試。微凸塊每層厚度依序為5μm銅、2μm鎳、15μm共晶錫銀銲錫、2μm鎳、5μm銅；接點之直徑為30μm。微凸塊被通以六萬安培每平方公分的電流密度。利用有限元素分析法得到的模擬結果顯示，電流在銲錫中分布相對均勻，代表在這個結構中電流聚集效應不是造成破壞的主要機制。在本次實驗結果中，我們觀察到在通電前期（電阻上升率20%以前）介金屬化合物長得很快，然而隨著通電時間的增加，不只有介金屬化合物的生成，還形成薄餅狀的連續的孔洞，代表此結構存在早期破壞之風險。除此之外，大多數在陽極發現的連續孔洞有嚴重的金屬墊層溶解的現象。孔洞的生成指出目前電遷移在鎳/錫銀銲錫/鎳微凸塊中依舊扮演著重要的角色。

關鍵字

電遷移 ； 微凸塊

並列摘要

In this study, we used daisy chain structure (40 bumps per chain) for electro migration experiments. The thickness of each layer of the microbumps was Cu:5μm / Ni:2μm / Eutectic SnAg Solder:15μm / Ni:2μm/ Cu:5μm; the diameter of the solder joint was 30μm. Microbumps were stressed with a current density of 6 x 10^4 A/cm^2. Our simulation analysis result showed that the current distributed homogeneously in the solder indicating the current crowding effect was not the major failure mechanism in this structure. We observed that as the electric current stressing time increased, continuous voids were formed with the IMCs indicating the risk of early structure failure. Most of the continuous voids were found at the cathode with serious UBM dissolution. The location of voids formation indicated that the electromigration was an important reliability issue in Ni/SnAg/Ni microbumps.

並列關鍵字

electromigration ； microbump