High speed and high accuracy inspection of in-tray laser IC marking using line scan CCD with a new calibration model

• Published in: Optics and laser technology 2011-02, Vol.43 (1), p.218-225
• Main Authors: Lin, Chern-Sheng, Tsung Huang, Jui, Wei, Tzu-Chi, Yeh, Mau-Shiun, Chen, Der-Chin
• Format: Article
• Language: English
• Subjects: Accuracy; Algorithms; Calibration; Calibration model; Charge coupled devices; Exact sciences and technology; Fundamental areas of phenomenology (including applications); High speed; Image forming and processing; Imaging and optical processing; Inspection; Integrated circuits; Laser marking; Lasers; Line scan CCD; Optics; Physics; Position (location)
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2010.06.017

This study used a high-speed high-resolution line scan CCD, and a Delta motor drive module to provide position feedback in a laser marking system. Based on a novel algorithm, image processing of the high-speed CCD scan was allowed the accurate determination of the laser marking location. This system was calibrated using a template, and a novel 1-D calibration model of the line scan CCD was developed. The relevant position of each IC in the tray was obtained based on the calibration algorithm. Gain and offset calibration, sub-pixel calculation, and normalized checks were performed in this automatic optical inspection system. The total processing time for laser correction marking, scanning and identification was about 2∼2.5 s, the positioning accuracy was×9 μm, and the industrial specification and process capability index Cpk reached over 1.2.