IC Solder Joint Inspection Based on an Adaptive-Template Method

In this paper, an integrated circuit (IC) solder joint inspection algorithm is proposed based on an adaptive-template method. To the best of our knowledge, it is the first time to utilize the adaptive-template scheme for IC solder joint inspection. First, a number of qualified solder joint images are used to construct a dictionary. Then, we formulate the construction of the adaptive template for each IC solder joint as an optimization problem, which is solved by the elastic net. The defects can be inspected by the difference image between the IC solder joint image and its corresponding adaptive template. We propose a weighting scheme to highlight the defects in the solder joint images, in which different weights are given to different pixel locations in the difference images. Finally, the weighted defect score is defined to evaluate the quality of the solder joint image. Experimental results indicate that the proposed method is superior to the existing methods in terms of omission rate and error rate.