10 October 2007 Real-time system for measuring three-dimensional shape of solder bump array by focus using varifocal mirror
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Proceedings Volume 6716, Optomechatronic Sensors and Instrumentation III; 671606 (2007) https://doi.org/10.1117/12.754177
Event: International Symposium on Optomechatronic Technologies, 2007, Lausanne, Switzerland
Abstract
This paper describes a real-time system for measuring the three-dimensional shape of solder bumps arrayed on an LSI chip-size-package (CSP) board presented for inspection based on the shape-from-focus technique. It uses a copper-alloy mirror deformed by a piezoelectric actuator as a varifocal mirror enabling a simple, fast, precise focusing mechanism without moving parts to be built. A practical measuring speed of 1.69 s/package for a small CSP board (4 x 4 mm2) was achieved by incorporating an exclusive field programmable gate array processor to calculate focus measure and by constructing a domed array of LEDs as a high-intensity, uniform illumination system so that a fast (150 fps) and high-resolution (1024 x 1024 pixels/frame) CMOS image sensor could be used. Accurate measurements of bump height were also achieved with errors of 10 μm (2σ) meeting the requirements for testing the coplanarity of a bump array.
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Akira Ishii, Haruka Tai, Jun Mitsudo, "Real-time system for measuring three-dimensional shape of solder bump array by focus using varifocal mirror", Proc. SPIE 6716, Optomechatronic Sensors and Instrumentation III, 671606 (10 October 2007); doi: 10.1117/12.754177; https://doi.org/10.1117/12.754177
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