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Automated Optical Inspection (AOI) for PCB Testing and its Benefits

 Jul 22, 2019

Automated Optical Inspection

One cannot imagine electronic gadgets without PCBs. But, it is crucial that the PCBs fitted in various devices and components work without any issues. Hence, there are various testing methods that they go through before being incorporated in any device. One of the important testing methods is AOI. Automated optical inspection or AOI is primarily a type of visual inspection method performed by PCB assembly manufacturers to point out the quality-related defects. It is done with the help of a camera which scans through the PCB to detect the possibility of catastrophic failure. It is a non-contact autonomous method implemented at various stages throughout the process such as pre and post reflow, application of solder paste, and so on. This inspection method is certainly useful as it helps prevent failures that may occur when the PCB becomes functional. For PCB assembly manufacturers, fabricators, and service providers, this is one of the crucial steps in testing PCB assemblies and fabrication. This post discusses this method in detail along with its benefits.

Why AOI is Superior to Manual Inspection

PCBs used to undergo manual inspection, and they still do. However, given the increasing complexity of PCBs, only manual inspection is not enough. Quite obviously, with manual inspection, errors such as missing or wrongly mounted parts may not be identified. Thus, an automated microscopic view is essential to detect minute flaws. Here are some factors, which depict why AOI is superior to manual inspection:

  • AOI is a method that identifies errors in real time and at a faster speed.
  • It also provides relevant empirical data that is important from the point of view of documentation, process control, and avoid the same errors in the future.
  • This is crucial for increased production volumes of PCBs and increasing number of complex electronics devices.
  • AOI deploys various strategies to test a PCB including all its components, soldered joints, and so on.
  • You can program it to test if your PCB matches the stipulated requirements.
  • It uses a pattern of matching algorithms to identify and record functional as well as flawed PCBs. This way, you get a pattern which when analyzed can help determine trends and lead to process improvement.
  • With AOI, you can be sure about the functioning of your PCB.

Attributes and Working of AOI

Automated optical inspection is a method which scans through the board. Here are a few attributes of AOI and the way it works:

  • It comprises a couple of high definition cameras and high-end lighting systems which include infrared, UV, and LED.
  • The images that are captured in the cameras have tremendous clarity owing to the effective lighting system.
  • It has an inbuilt software that processes a comparison of the required parameters with that of the captured image. This way, it is easy to identify even the minutest errors or abnormalities in the PCB.
  • AOI uses various algorithms such as pixel counting and inspection to view and analyze the image from different angles and points of view.
  • Other algorithms include blob analysis, template matching, and object recognition among others. Various newer methods are being developed owing to the increasing demand for PCBs in the market.
  • Vectoral imaging technology is one of them being used for PCB and assembly inspection. It is a pattern search technology based on geometric figure extraction.

Benefits of AOI for PCB Inspection

From the above-mentioned pointers, we by now certain benefits of AOI for PCB inspection. Here are some benefits listed:

  • Detection of Visual Defects: AOI can accurately detect surface defects on the board such as stains, missing or wrongly mounted components, soldering flaws, and scratches. Human eyes can easily miss any of these obvious defects as they are extremely minute.
  • Flexibility: The best part of AOI is that it can be applied and run through at any stage of the process and can be carried out multiple times if required.
  • Detection of Defects in PCB Assemblies: AOIs can accurately determine flaws not just in single PCBs but also PCB assemblies. Inspection of PCB assembly includes identifying defects in values, polarity and component soldering among others.
  • Cost Effectiveness: AOI is cost effective when compared with a few other inspection methods such as X-ray inspection. Also, AOI is cost effective for the PCB manufacturer in the long run as it helps prevent the repetition of flaws and increase production values.
  • Reliability: There is no doubt that AOI is a very reliable method that gives accurate output.

If you are looking for tested and good-quality PCBs or assemblies, it is crucial that you source them from a reputed manufacturer. Accelerated Assemblies offers solutions on prototypes PCB assemblies. The company employs AOI to ensure error-free products.

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