Automated Inspection System for Electronic Devices Mounted on Printed Circuit Boards Using Light-Section Method

An automated system has been developed to visually inspect surface mount devices (SMDs) on printed circuit boards (PCBs). The location of an SMD is recognized from range data detected by the light section method. Since the PCB surface is treated as the base height in a recognition task, its accurate determination is extremely important, especially for reliable inspection of small SMDs such as 1005 chip components (1.Ommx 0.5mm) and the fine pitch leads of LSIs. However, the light section method is adversely affected by noise in the form of secondary reflection that results in partially incorrect range data. To determine the accurate base height from the waveform without the influence of noise, we adopted statistical techniques that approximate the PCB surface as a straight line. This paper describes the inspection algorithm and provides a brief explanation of the automated inspection system.