A simple but comprehensive prototype model developed to automate the inspection of wedge bonds in the IC assembly process is described. The defects associated with the bond quality are classified into four categories: size, shape, position, and dimension. The bond is inspected sequentially for each category of defects and is rejected without further processing when any defect is detected. The procedure adopted in the prototype is as follows. A global thresholding technique automatically binarizes the intensity image of the bond. Simple features such as the pixel count, minimum enclosing rectangle, centroid, and median are used to verify the specifications related to the size and shape. An intelligent scanning technique inspects the position-related specifications in addition to identifying the wire and tall positions of the bond. The dimensions of the bond are determined using projection information. Most importantly, this model is capable of determining the wire position, which is useful in inspecting wire-related defects. Experiments conducted on actual sample ICs have shown a 100% success rate.
"Prototype model for automatic integrated circuit bonding inspection," Journal of Electronic Imaging 4(3), (1 July 1995). https://doi.org/10.1117/12.210719