OPTICAL INSPECTION OF SOLDER JOINTS

摘要

A new method of optical inspection of populated printed circuit boards (PCB), specifically of component leads and solder joints, is provided. At least a portion of the PCB being tested is illuminated with a beam of collimated light. A light detecting device detects specular reflection from the features being examined on the PCB for diagnostically useful patterns. For example, each properly soldered gull-wing lead produces three detectable reflections, each properly soldered J-type lead produces two detectable reflections, and each properly soldered rectangular lead produces one detectable reflection. Other PCB features produce other diagnostically useful reflections. An anomalous reflection indicates, for example, improper soldering or a misplaced component. The invention can be configured to inspect a plurality of leads simultaneously, allowing increased throughput.