Pattern matching: Using this techniques the AOI system stores information of both good and bad PCB assemblies, matching the obtained image to these.Template matching: Using this form of process the AOI, automated optical inspection system compares the image obtained with the image from a "golden board".Using this comparison the AOI system is able to detect and highlight any defects or suspect areas.ĪOI uses a number of techniques to provide the analysis of whether a board is satisfactory or has any defects: The automated optical inspection, AOI system uses the captured image which is processed and then compared with the knowledge the machine has of what the board should look like. In this way the AOI machine is able to build up a picture of the board The board is light by several light sources and one or more high definition cameras are used. They achieve this by visually scanning the surface of the board.
AUTO VISUAL LIGHTING MANUAL
As such they are able to perform all the visual checks performed previously by manual operators, and far more swiftly and accurately. They can also detect incorrect components, missing components and incorrectly placed components. They are able to detect a variety of surface feature defects such as nodules, scratches and stains as well as the more familiar dimensional defects such as open circuits, shorts and thinning of the solder. In this way a rapid response can ensure that problems are recognised quickly and rectified before too many boards are built with the same problem.Ĭomparison of the major defect detection capabilities of AOI, AXI and ICTĪOI, automatic optical inspection systems use visual methods to monitor printed circuit boards for defects. Additionally process problems in the solder and assembly area can be seen early in the production process and information used to feedback quickly to earlier stages. With faults costing more to fix the further along the production process they are found, this is obviously the optimum place to find faults. In this way they can be used to catch problems early in the production process. Automated optical inspection systems can be placed into the production line just after the solder process. One of the solutions to this is to use automated or automatic optical inspection systems. AOI, automatic optical inspection is an essential tool in an integrated electronics test strategy that ensure costs are kept as low as possible by detecting faults early in the production line. With the marketplace now requiring high volume, high quality products to be brought to market very quickly very reliable and fast methods are needed to ensure that product quality remains high. Even when it was an accepted approach, it was realised that it was not particularly effective as inspectors soon tired and poor and incorrect construction was easily missed. This increase in the complexity of boards also means that manual inspection is not a viable option these days. Even relatively average boards have thousands of soldered joints, and these are where the majority of problems are found. The introduction of surface mount technology, and the subsequent further reductions in size mean that boards are particularly compact. Need for AOI, automatic optical inspectionĭespite the major improvements that have been made, modern circuits are far more complicated than boards were even a few years ago. Automatic optical inspection, AOI enables fast and accurate inspection of electronics assemblies and in particular PCBs to ensure that the quality of product leaving the production line is high and the items are built correctly and without manufacturing faults. See also: ATE basics In-Circuit test, ICT Functional test, FATE Developing test strategyĪutomatic or automated optical inspection, AOI, is a key technique used in the manufacture and test of electronics printed circuit boards, PCBs. PCB inspection techniques Automated optical inspection, AOI Automated X-ray inspection, AXI Design for AOI test Automatic optical inspection, AOI systems Key points for AOI, automatic or automated optical inspection systems used in electronics PCB printed circuit board manufacture.