An automated method for inspection of IC bonds

The continuing increase in packing density of VLSI circuits requires that the inspection process be completely automated. The paper suggests a new method for automatic inspection of that part of the wire bond where the wire connects to the bond pad on the chip. A popular type of bonding (connected to bond pad) known as "ball bond" is considered. Although several approaches for ball bond inspection have been introduced, they do not reveal efficient results. The suggested method consists of five steps: (1) enhance the edges using Binomial and the modified Laplace filter; (2) binarize the image: (3) extract center point of the ball bond; (4) extract the ball bond boundary; (5) fit the ellipse using direct ellipse-specific fitting. Experimental results illustrate that the proposed method performs the inspection of ball bond more fast and accurately as compared to the conventional ball bond inspection methods. In addition, our method finds the size and orientation of the ball from the bond image containing the part of the ball.