26 January 2016 Development of an AOI system for chips with a hole on backside based on a frame imager
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Proceedings Volume 9903, Seventh International Symposium on Precision Mechanical Measurements; 99031F (2016) https://doi.org/10.1117/12.2211942
Event: Seventh International Symposium on Precision Mechanical Measurements, 2015, Xia'men, China
Defects exist for a few of IC chips during fabrication and packaging. The cost for follow-up processes can be reduced if chips with defect size of impacting chip quality can be inspected and removed during the earlier sorting process. Products will be more cost-effective and competitive. According to the inspecting requirements for microphone chips, developed AOI system has to detect the boundary flaws and hole-inside defects with size of greater than criteria from chips backside. Both the length and width of chip size are less than 5 mm and there’s depth difference between the surface of chip backside and the hole-inside membrance. Thus image acquisition device is designed and implemented by an area scan imager and a telecentric lenses with a coaxial LED lighting module. Therefore we can ignore the image radiometric and geometric calibration, and keep off the shadow inside the rim of hole. An algorithm to detect defects and derive their size based on the edge pixels statistic distribution and binary chip edge image is selected. Developed AOI system then can meet the requirements of real-time defect inspection with high accuracy and performance.

Frame opto-mechanical device has the spatial resolution of 5μm and FOV of 6.4 x 5.1 mm. And defect inspection can be completed within 150 ms for the chip size of 2.5 x 3.0 mm. The processes of image acquisition and defect inspection can be accomplished during the chip sorting process to satisfy the real-time online inspection. Inspected chips are placed in GO/NG trays in real-time according to their quality. From the verification results compared with the ones by microscope, the inspection accuracy is better than system requirements. The over kill rate is less than 0.3% and 3% for chip boundary flaws and hole-inside defects respectively. But it still can’t be inspected correctly for the hole-inside defects of only one membrance breakage. In the future, we will improve the illumination and detecting algorithm to solve this imperfection. Inspection systems have been integrated into our customer’s chip sorters, and successfully delivered to and accepted by end-users for online operations. Our system also can be accommodated to other customer’s chip sorters with specific requirements for chip backside inspection.
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Ming-Fu Chen, Ming-Fu Chen, Chih-Chung Chou, Chih-Chung Chou, Chun-Chien Lien, Chun-Chien Lien, Rui-Cian Weng, Rui-Cian Weng, } "Development of an AOI system for chips with a hole on backside based on a frame imager", Proc. SPIE 9903, Seventh International Symposium on Precision Mechanical Measurements, 99031F (26 January 2016); doi: 10.1117/12.2211942; https://doi.org/10.1117/12.2211942

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