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Title: Effects of process parameters on bondability in thermosonic copper ball bonding
Authors: Xu, Hui
Liu, Changqing
Silberschmidt, Vadim V.
Wang, Honghui
Issue Date: 2008
Publisher: © IEEE
Citation: XU, H....et al., 2008. Effects of process parameters on bondability in thermosonic copper ball bonding. IN: 58th Electronic Components and Technology Conference, (ECTC 2008), Lake Buena Vista, FL, 27-30 May, pp. 1424 - 1430
Abstract: Thermosonic copper ball bonding is an absorbing interconnection technology that serves as a viable and cost saving alternative to gold ball bonding. Its excellent mechanical and electrical characteristics make copper ball bonding attractive for high-speed, power devices and fine-pitch applications. However, copper is easily oxidized and harder than gold, which causes some critical process problems in connection with bondability. In this study, a 50 mum copper wire with purity of 99.99% was bonded on aluminum metallization with thickness 3 mum using an ASM angle 60 automatic thermosonic ball/wedge bonder. Experimental studies of copper free air balls (FABs) formation and bonding process were conducted to establish the bonding mechanism and to explain the effects of process parameters on bondability. A micro-slipping model was proposed to account for the effects of the ultrasonic power and bonding force on bondability. It was found that the bondability was determined by a slip area at the bonding interface. The occurrence of bonding only at the periphery of the contact area between FAB and aluminum metallization was attributed to partial slips at the bonding interface. Variation in the ultrasonic power and bonding force that lead to different stick-slip modes, can effect bondability in the ultrasonic bonding process. It is important to set a proper bonding time to achieve interatomic bonding without causing fatigue rupture of microjoints. It was also found that preheating of the chip to a certain temperature can improve bondability.
Description: This is a conference paper [© IEEE]. It is also available at: http://ieeexplore.ieee.org/ Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Version: Published
DOI: 10.1109/ECTC.2008.4550164
URI: https://dspace.lboro.ac.uk/2134/5337
ISBN: 9781424422302
ISSN: 0569-5503
Appears in Collections:Conference Papers (Mechanical and Manufacturing Engineering)

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