The Interfacial Reaction on Pd-Coated Cu Wire Bonds Under Current Stressing

• Main Authors: Zheng-XueTsai, 蔡政學
• Other Authors: Kuo-Chang Lu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/87407535661362624100

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 100 === The influence of palladium in the interfacial reactions of copper wire bonding under current stressing is reported in this study. At the as-bonded step, Pd dissolved into a Cu ball bond and then gathered at the edge of the Cu ball, forming an anti-oxidation layer. The growth rate of IMCs under current stressing depends on the type of wire bonds and the direction of the current. The interfacial reaction at the anode, where electrons flow from Cu wire bonds to the Al pad, is faster than that of the cathode, where electrons flow from the Al pad to Cu wire bonds. This is probably because the dominate diffusion species in Cu-Al IMCs is copper. Results show that the existence of Pd restrained the growth rate of IMCs due to the formation of the Pd-enriched layer near the interface at the anode which acted as a diffusion barrier; however, a notch was formed at the cathode and the effect on the IMC growth rate could be neglected there. This may be the reason why Pd-coated copper wires show better bonding reliability than pure copper wires in the wire bonding process.