Microstructural study of copper free air balls in thermosonic wire bonding

Authors:
C. J. Hang;C. Q. Wang;Y. H. Tian;M. Mayer;Y. Zhou
Affiliations:
State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China and Centre for Advanced Materials Joining, University of Waterloo, Waterloo, On ...;State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China;State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China;Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1;Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Venue:
Microelectronic Engineering
Year:
2008

Citing 0
Cited 2

Effect of electronic flame off parameters on copper bonding wire: Free-air ball deformability, heat affected zone length, heat affected zone breaking force

Microelectronic Engineering
A hybrid intelligent approach for optimizing the fine-pitch copper wire bonding process with multiple quality characteristics in IC assembly

Journal of Intelligent Manufacturing

Quantified Score

Hi-index	2.89

Visualization

Abstract

Copper wires are increasingly used in place of gold wires for making bonded interconnections in microelectronics. In this paper, a microstructural study is reported of cross-sectioned free air balls (FABs) made with 23@mm diameter copper bonding wire. It was found that the FAB is comprised of a few columnar grains and a large number of fine subgrains formed within the columnar grains around the periphery of the FAB. It was determined that conduction through the wire was the dominant heat loss mechanism during cooling, and the solidification process started from the wire-ball interface and proceeded across the diameter then outward towards the ball periphery. The microstructure of the Cu ball bond after thermosonic bonding was investigated. The result showed that the subgrain orientations were changed in the bonding process. It is evident that metal flow along the bonding interface was from the central area to the bond periphery during thermosonic bonding.