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Bond pad pitch is defined as the center-to-center distance between the bond pads of a die. Fine pitch refers to smaller-than-normal spacing between the bond pads. Due to rapid strides in die shrinking trends, the actual definition of what fine pitch is changes from one point in time to the next. In the early 90's, fine pitch meant 3.5-4 mils; in the mid 90's, it was 3.1 mils; and in the late 90's (during which the study was done), it was 2.8 mils (70-micron). This study dealt with the development of 70-micron pitch capability for the wirebonding process. The study was able to conclude the following: 1) control of the impact parameter is important in fine pitch wirebonding; 2) bond velocity and tip offset plays a major role in small ball formation; 3) contact threshold also has an impact on ball formation. The study was also able to establish the process capability for fine pitch wirebonding.
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