Automated Inspection of Ic Printed Mark Defects (Ii)—defect Detection

The study develops a defect detection system for the IC printed marks. The system can be divided into two main parts, namely, image pre-processing and defect detection. Image pre-processing includes binary image operation, image rotation, image segmentation and thinning operation. Defect detection includes character searching, characteristic extraction, characteristic comparison, image mapping and defect identification. As for the performance of this system, it can recognize the seven kinds of most common IC printed mark defects. For a case of 15mm and 8mm IC chip with 16 printed marks, the recognition speed averages about 0.54 seconds for each chip, and the accuracy is 99.5% for distinguishing a good/bad chip and 98.25% for distinguishing the defect types. In addition, the study proposes a two-stage character searching method, which is quicker than the image projection and segmentation method. Moreover, when the defect types do not need to be distinguished, the research suggests the character searching method coupling with the normalized cross correlation scheme; however, when distinguishing the defect types is necessary, the study proposes the characteristic comparison method. Both have the better results.