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|Wire Bonding UPH and Stitch Bond Improvement using 20 Micron Insulated Wire with Security Bump|
|Keywords: insulated wire, security bump, UPH|
|Bump bonding is a variant of the ball bonding process that is commonly used in the microelectronic industry to make bumps on dies that will later be flip-chip bonded. In this study, security bumps are for strengthening the stitch bonds of a 20 micron diameter insulated Au wire bonding process. The optimized ball and stitch bond parameters combined with the security bumps placed upon the stitch bonds substantially improve the second bond strength. A comparison of pull test results for stitch bonds without and with security bumps shows up to 50 % increase of the stitch pull force if security bonds are used. The average pull force without security bump is 3.4 gf, while it is up to 5.1 gf with security bumps. The effect of varying the relative position of security bumps to the stitch bonds is investigated and the window with the best results is determined to be ranging from 15 to 27 micron position shift towards the ball bond. The number of kinks in the looping with insulated wire is reduced from 4 (as originally required with bare wire to avoid shorts) to 2 (if wires touch, shorts are avoided by the wire insulation). Compared to the original process with bare wire, the overall UPH improvement of the insulated wire process including security bump and reduced number of kinks is 4%.|
|Chunyan Nan , PhD Student
University of Waterloo
Waterloo, Ontario N2L3G1,