電化學沉積法於超細間距微無鉛銲錫凸塊的開發

Abstract

本研究於超細間距20μm，直徑12μm的孔洞依序電鍍銅、鎳及錫銀合金於指定規格：銅厚度5μm，鎳厚度3μm，錫銀合金5μm，作為無鉛銲錫凸塊以及凸塊下金屬層的製備。錫銀合金的成份為Sn-2.5 wt% Ag，電鍍完成後經由迴銲將凸塊熔成球形，再以高解析度電子微探儀分析其中組成，我們發現電流密度會對錫銀合金凸塊表面形貌造成巨大的影響，無鉛銲錫凸塊經由配方和參數的調整可以成功電鍍，填孔率超過99.5％，並且成分誤差控制在0.2 wt%之內。

In this study, a Cu/Ni UBM and lead-free solder for 20 μm pitch micro-bump has been attempted to fabricate via consecutive electroplating of Cu, Ni and binary SnAg in specification on a patterned wafer. The targeted thickness of Cu and Ni are 5 μm and 3 μm for the preparation of UBM, and the thickness of the SnAg solder bump is 5 μm with 2.5 wt% Ag composition. After the electroplating process, the solder undergoes a reflow process to obtaining spherically-shaped bumps. Electron Probe Micro-analyzer (EPMA) is carried out to evaluate relevant material properties. We observe a strong effect for the plating current density on the resulting bump morphologies. After adjusting relevant parameters, the formation of 5 μm Cu/3 μm Ni/5 μm Sn-2.5 wt% Ag bumps can be successfully fabricated, and the spherically-shaped solder balls are confirmed with composition variation within 0.2 wt% deviation.