A Design Data-Based Visual Inspection System for Printed Wiring

Until very recently, printed wiring board (PWB) fabrication relied on electrical testing and visual inspection by humans to provide feedback for process control. The low efficiency of visual inspection is often a severe problem for printed wiring board manufacturers. During the past few years, considerable work has been done both in industry and research institutions to solve inspection problems with image-analysis techniques. However, many of these efforts have focused on satisfying the needs of a limited set of users. This makes them vulnerable to changes in fabrication technology and the geometrics of wiring patterns. In the factories of the future, computer-aided design (CAD) data will be the source of all the control information for the fabrication processes. Accordingly, the primary goal of the work presented here has been to devise an approach that can be integrated to CAD data-driven production environments. The main result is the CAD data-based verification of wiring patterns. Other important objectives have been high throughput, low cost, and compact implementation. From the developmental point of view, the goal has been to build a functionally complete experimental system that can be upgraded to run at the speed of image acquisition by adding standard hardware.