Automated Optical Inspection: understanding the process and which method to choose.

Automated optical inspection (AOI) is a form of automated visual inspection used in the production of printed circuit boards (PCBs), LCDs, and transistors. A camera autonomously examines the product being tested for quality issues and catastrophic failures (such as missing components) (e.g. fillet size or shape or component skew).?

Because it is a non-contact test method, it is frequently employed in the manufacturing process. It is used throughout the manufacturing process at many stages, such as bare board inspection, solder paste inspection (SPI), pre-reflow, post-reflow, and other stages.

AOI is crucial to the creation of PCBs. It ensures that every board can deliver the high performance needed in intricate electrical applications.

When AOI finds a PCB defect, the board is flagged to be sent back for repairs. There are several methods by which this process might take place. The results of the AOI may not meet some facility specifications, such as the requirement that all lines on a board must be larger than a certain size. In this situation, people can examine the results and choose which boards need to be sent back for more work. Alternatively, AOI can contrast the real PCB with a CAD rendering of an ideal PCB. When the actual board deviates from the ideal design, AOI can automatically find those areas and highlight them.

Knowing which AOI method to choose

There are three main types of AOI methods that one can consider. It is best to determine the exact needs of your specific manufacturing process when deciding on the route to take to achieve proper AOI.?

2D AOI

2D optical AOI systems are what are typically referred to as the traditional form of AOI. This process has been around for quite some time and it is still used by many manufacturers globally. The process uses a range of high-quality cameras with precise lenses to inspect circuit boards for defects.

One of the most reliable products in this regard is the Nordson YESTECH BX. This product features 5 megapixel cameras with proprietary lightning to deliver accurate scanning and inspection. It also boasts a trademarked “AutoTrain” functionality which allows for quick setup and installation so that manufacturers can take full use of the solution the product offers right out of the box.

3D AOI

Of course, as industries become more mature, newer forms of AOI have been developed. 3D AOI is one such case of improvement in the field of AOI. 3D AOI inspects assembled printed circuit boards and other electronics in three dimensions.?

A 3D AOI system uses side and vertical cameras to view the entire board. Because of this, 3D AOI can detect when components are reversed or skewed. Defects including a surplus of solder joints and uneven solder can be detected by more intelligent systems. These systems depend on multi-stage lighting to give the machine vision lens enough light. The best illumination is circular because it prevents shadows from being a potential source of erroneous calls. One advantage of 3D AOI is that it may detect flaws as small as 10 ppm. This lessens the chance of approving constructed boards when there are genuinely minute flaws that should lead to failure.

One of the best products to consider if you wish to use 3D AOI is the Vi Technology 5K SPECTRO 3D Automated Optical Inspection Machine. This product features high-speed linear motors with closed-loop high-resolution linear encoders for accurate flaw detection. Further to this, it features custom designed ultra-low distortion telecentric lenses which further lead to enhanced accuracy and reliability.

X-Ray AOI

The technology of automated X-ray inspection (AXI) is built on the same ideas as automated optical inspection (AOI). Instead of using visible light to automatically inspect things that are generally hidden from view, it uses X-rays as its source.

AXI has a significantly wider range of applications than AOI, which is typically linked with electronics production because of its widespread use in PCB manufacturing. It includes everything from inspecting the condition of alloy wheels to finding bone fragments in processed meat.

A product to consider if you are looking for AXI solutions is the GE Phoenix X|aminer. This product, from Waygate Technologies, is an easy to use entry-level microfocus AXI system with a strong performance that is designed for the special needs of the high-resolution inspection of electronic assemblies, components and PCBs. Due to its new combination of CsI flat panel detectors and computed tomography (CT), the system provides significantly better signal-to-noise ratio, sharpness and life-imaging capability.?

Where to find these and other products

Omnigo offers all of the above products, and a whole lot more! Contact us today for expert advice on AOI and AXI devices.