This paper proposes an automated visual inspection system for Printed Wiring Boards (PWB's) . This system has employed both the feature extraction method and the design rule checking method.
The feature extraction method has been designed to detect micro defects, and compresses the defect data by the defect code chain in order to reduce the false alarms.
The design rule checking method has been designed to detect dimensional errors of lands by using the compression techniques of the reference data.
They are carried out in parallel, and real time processing has been possible.
As a result, it has been proved that the system satisfies the required resolution and accuracy, and detects all the fatal defects completely at the video rate.

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This paper reports the results of the practical investigation on Laser Direct Imaging, abbreviated as LDI here, in views of the application to printed wiring board fabrication. The studies are based on the operation of LDI apparatus newly developed, which utilizes 488 nm wavelength of Argon laser oscillation.
Firstly, the measurements of the physical properties of a laser dryfilm photoresist such as optical, photosensitive, and thermal characteristics, have been made, and the test pattern panels have been processed through the processes from lamination to development including LDI, so that the fundamental compatibility of the dryfilm resist properties with LDI apparatus has been confirmed.
Secondly, 4 layer boards are prototyped with LDI to evaluate the practicability of LDI application to PWB fabrication. Additionally, the raw cost of the panels with LDI has been estimated, and shown comparatively with the conventional phototool method. The economical advantage of LDI is commented on more positively as the production lot becomes more diversified and smaller in size, while the breakeven point of LDI with the phototool method being illustrated.

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[in Japanese]

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[in Japanese]

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