A pattern inspection system for high-density printed wiring boards

This paper describes an automatic inspection system for high-density copper paste patterns on green sheets (unsintered inner layers of multilayer ceramic boards). We devised a high-speed laser sensing method to measure pattern thickness by triangulation simultaneously with pattern width. We implemented an original «Radial Matching Algorithm (RMA)» using high-speed electronic image processing circuits (7.7 GOPS: Gigaoperations per second) to process acquired pattern data instantaneously to detect defects. The system can inspect a 300 mm-square area 3-dimensionally within 3 minutes at a 5-μm resolution, and has contributed to increased yield and lower production costs for multilayer ceramic wiring boards