Visual inspection system to detect connector tilts in PCBAs

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Date
2005
Authors
Vithyacharan, Retnasamy
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Abstract
AVI’s are playing important roles in quality inspection in the electronic industry. Most existing AVIs are single overhead camera and are incapable detecting 3D defects. This thesis presents the development of a single camera visual system to detect tilt of a Peripheral Component Interconnect (PCI) connector on a Printed Circuit Board Assembly (PCBA). The visual system developed consists of a personal computer, digital camera, slide projector and a mirror. The problem in the current research and the objective is to detect tilt in a PCI connector using a single overhead camera. The distortion severity in the imaging system was initially studied to decide the need for camera calibration. An equation was formulated experimentally to determine the scaling factors at different height levels of object surface for converting image pixel coordinates into physical dimension. The slide projector was used for projecting sinusoidal fringes onto the surface under study. Phase-shifting was achieved using a mirror mounted on rotary stage. Since the light source used is non-collimated, i.e. the incident angle varies along x-, y- and z- directions, a calibration exercise was carried out to obtain an equation for the incident angle of the beam along the length of the object surface for different object height levels. Solid glass blocks were initially used in place of actual PCI connectors to test and verify the system. The phase-shifting technique was applied to calculate the tilt angles on the glass blocks and later applied to the actual connectors. This visual system developed using phase-shifting technique demonstrates successful tilt detection and measurement in a PCBA. Compared to existing system the proposed system uses single overhead camera , noncollimated light source and phase shifting technique to detect tilt on a connector mounted to a PCBA.
Description
Master
Keywords
Mechanical Engineering , Printed Circuit Board Assembly
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