The Pd distribution and Cu flow pattern of the Pd-plated Cu wire bond and their effect on the nanoindentation

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• 作者：Yu-Wei Lin^a ; Ren-You Wang^a ; Wun-Bin Ke^a ; I-Sheng Wang^a ; Ying-Ta Chiu^a ; ^b ; Kuo-Chang Lu^a ; ^{gkclu@mail.ncku.edu.tw} ; Kwang-Lung Lin^a ; ^{matkllin@mail.ncku.edu.tw} ; Yi-Shao Lai^b
• 关键词：Copper wire bond ; Ball bond ; Solid solution ; Pd plating ; Flow pattern
• 刊名：Materials Science and Engineering ; A
• 出版年：2012
• 期刊代码：61_09215093
• 类别：ms
• 出版时间：1 May, 2012
• 卷：543
• 期：Complete
• 页码：152-157
• 文件大小：1528 K

摘要

The Pd plating on the 20 渭m Cu wire dissolves in the free air ball (FAB) and the Cu ball bond during the wire bonding process without forming intermetallic compounds. The limiting supply of Pd and the short bonding process, 15 ms of thermosonic bonding, result in uneven distribution of Pd in the as produced Cu ball bond. Also, the Pd-rich phase may accompany small voids formed within the FAB and the wire bond, and following the direction of semi-solid Cu flow. The Pd distribution, as evidenced by the focused ion beam (FIB) and wavelength dispersive X-ray spectroscopy (WDS) mapping, reveals the whirlpool flow pattern of Cu within the FAB and the ball bond. Pd distributes within the copper ball through convective transport by the copper flow. Additionally, hardness measurements by nanoindentation testing show that the Cu ball bond is harder in the regions where Pd exists.