Automated Optical Inspection tool using the LPKF PCB mechanical prototyping machine

Automated optical inspection (AOI) of assembled PCB's is one of the most widely spread non-destructive testing method used in mass-production of electronic systems. Some great advantages of the AOI mechanism is the fact it is a non-contact test method and the AOI inspection is much more reliable and repeatable than manual visual inspection. Fast video processing algorithms and precise mechanical systems are supporting this cost-effective method for investigating electronics assemblies. The authors will present how to convert the LPKF prototyping machine for PCBs into an AOI machine. The LPKF machine is equipped with a grayscale camera used for calibration procedures. Since this camera is already available we can use it for AOI purposes without extra costs. In this way we will add a new feature to the LPKF machine, we will considerable reduce the testing costs (no extra hardware needed) and we will assure an automated way to test PCBs. We automated this process by using CAD manufacturing files. The CAD environment generates production files which later are imported in our tool for testing purposes. The tool can make both SMT inspection like area defects, component offset, component polarity, component presence/absence, excessive solder joints, flipped component, etc. and PCB inspection like line width violations, spacing violation, access copper, missing pad, shorts circuits, cuts, etc.