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Proceedings Paper

Research on enhancing signal and SNR in laser/IR inspection of solder joints quality
Author(s): Zhengjun Xiong; Xuezhong Cheng; Xiande Liu
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Paper Abstract

The quality of electronic products is directly dependent upon that of solder joints on printed circuit boards (PCB's). The inspection of solder joints quality by use of both Laser and Infrared technology is an advanced technique. However, small signal and low signal-to-noise ratio (S/N) require the system to have a high sensitivity to temperature changes. In order to overcome them, in this paper, two methods to enhance signal and S/N in certain laser beam power and warming time are proposed and experimented. The theoretical analysis and experiment results show that: (1) When laser beam is injected into the solder joints at a certain angle with the normal of their surface, the signal and S/N increase, in general, the increment is 2-3 times. (2) When the solder joints is located at a position with a distance from the focus of thr optics, where the solder joints are just full of the field of view of the optical system, the S/N can be improved. In this case, the requirement on the stability of working is largely loosened.

Paper Details

Date Published: 1 March 1991
PDF: 6 pages
Proc. SPIE 1467, Thermosense XIII, (1 March 1991); doi: 10.1117/12.46453
Show Author Affiliations
Zhengjun Xiong, Huazhong Univ. of Science and Technology (Singapore)
Xuezhong Cheng, Huazhong Univ. of Science and Technology (China)
Xiande Liu, Huazhong Univ. of Science and Technology (China)

Published in SPIE Proceedings Vol. 1467:
Thermosense XIII
George S. Baird, Editor(s)

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