Printed Circuit Board Inspection System PI/1

Abstract

An automatic printed circuit board (PCB) inspection system called PI/1, is described in this paper. The system can inspect PCB artwork and inner layers to find trace faults such as open circuits, short circuits, pin holes, fine lines and narrow line spaces. PI/1 uses a line scan camera with 1024 pixels resolution to take images. The whole image can be obtained by the help of a scanning mechanism in the X and the Y directions. Continuous pictures can be taken without blurring, and the resolution is between 1/2 to 2 mils. The inspection method used in PI/1 is a type of design rule checking. It does not require a reference image and can tolerate changes in the inspection environment due to illumination and PCB positioning. The inspection algorithm has been implemented into a special hardware and the inspection speed is about 4 x 106 pixels/sec.