Cratering on thermosonic copper wire ball bonding

Copper wire bonding offers several mechanical and electrical advantages as well as cost saving compared to its gold wire predecessor. Despite these benefits, silicon cratering, which completes the fracture and removal of bond pad underlayers, has been a major hurdle to overcome in copper wire bondin...

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Bibliographic Details
Published in:Journal of materials engineering and performance 2002-06, Vol.11 (3), p.283-287
Main Authors: Wei, Tan Chee, Daud, Abdul Razak
Format: Article
Language:English
Subjects:
Applied sciences
BONDING
Copper
CRATERS
Electric power generation
Electric wire
ELECTRICITY
Electronics
Exact sciences and technology
Fracture mechanics
Gold
HARDNESS
Materials engineering
Microelectronic fabrication (materials and surfaces technology)
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Silicon
WIRE
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Summary:Copper wire bonding offers several mechanical and electrical advantages as well as cost saving compared to its gold wire predecessor. Despite these benefits, silicon cratering, which completes the fracture and removal of bond pad underlayers, has been a major hurdle to overcome in copper wire bonding. Copper wire is harder than gold, and thus needs greater ultrasonic power and bond force to bond it onto metal pads such as aluminum. This paper reports a study on the influence of wire materials, bond pad hardness, and bonding-machine parameters (i.e., ultrasonic power and bond force) on silicon cratering phenomenon. Ultrasonic power and z-axis bond force were identified as the most critical bonding machine parameters in silicon cratering defects. A combination of greater bond force and lower ultrasonic power avoids silicon cratering and gives the desired effects. Results also show that a harder bond pad provides relatively good protection from silicon cratering.
ISSN:1059-9495
1544-1024
DOI:10.1361/105994902770344088