Comprehensive Guide To AOI: Automated Optical Inspection
Printed Circuit Boards (PCBs) are getting smaller and more complicated. They might have millions of soldered joints and a variety of small components. Errors are more likely to occur because of the increased complexity. To ensure that your clients are satisfied, you need to incorporate PCB inspection methods in your projects. There must be a reliable approach to inspect PCB problems and ensure that they perform as intended.
AOI: An Overview
Automated Optical Inspection (AOI) is a technology that may be used to identify even the tiniest of flaws on a densely packed circuit board. Many light rays and sensors, occasionally even video cameras, are part of an AOI system. A PCB is illuminated from various angles by the light sources, and the cameras take photographs or videos to provide a comprehensive image for evaluation.
An Automated Optical Inspection (AOI) is a standard method for determining the quality of a product. The PCB’s quality and performance may be tested for both catastrophic failures and minor errors when using a scanner. Several minor flaws might occur, such as misplaced components or incorrect soldering.
AOI comes in handy throughout the entire production process. It may be used to check bare circuit boards, solder paste, and soldering processes before and after reflow. A PCB board’s design can be harmed at any stage, and AOI can assist in discovering errors before a defective board is put into production.
The majority of AOI occurs in post-production, though. The reason for this is that an AOI system may simultaneously check for a wide range of problems using a single system. A single thorough inspection may be completed in a fraction of the time it takes to inspect at each process stage.
Using AOI as the last check is advantageous to speed up production and ensure that deadlines are met. It’s also possible to send faulty boards back for revision in the post-production stage while the rest of the panels continue to move forward.
The Function Of AOI
The following are some of the advantages of using AOI in PCB manufacturing:
- Assuring Excellence – AOI ensures that your PCB products work as expected. Your customers will be more satisfied, your reputation will be enhanced, and you’ll have more confidence in the value of the service you’re providing.
- Complex Board Evaluation – AOI can inspect complex board designs with a level of precision that the human eye cannot match.
- Streamlining Procedures – Finding problems quickly with AOI can assist in discovering patterns of errors and altering your procedures before you crank out hundreds of boards with the same issues. A study found that it is only 10 times more expensive to detect a problem in a freshly produced board, but it is 1,000 times more expensive to find a defect in an already deployed board. Your manufacturing processes will run more smoothly if you catch mistakes early on.
- Customizability – Although AOI is a fully automated procedure, the operator may configure the scanner’s settings to specify what to examine for. With a few simple adjustments, you can identify the problems you’re looking for.
How Is AOI Compared to Other Inspection Methods?
AOI has many benefits over other methods for detecting PCB flaws. The following list compares AOI to a variety of different types of visual inspection:
- Automated X-ray Inspection (AXI)
Instead of using light imaging, AXI employs X-rays to check the PCBs. Companies frequently use AXI to analyze exceptionally complicated or densely populated boards. A component can obstruct another because the light utilized for AOI bounces off surfaces. It’s possible to see all the layers of material using an X-ray, which goes through them.
AXI is cutting-edge technology, but its biggest drawback is its high cost. For the most part, AXI is not worth employing unless for extremely complex or heavily clustered boards because of its expensive cost
- Automatic Laser Test (ALT) Measurement
PCBs are scanned and measured using lasers instead of typical light imaging. The ALT system employs the placement of the lasers to determine the precise location and height of PCB components and their reflectivity.
As with AOI, problems in the ALT system may be discovered by comparing the actual measurements to a blueprint or set of requirements. Although interference can render the results unreliable, the solder paste’s position and quantity may be determined by using ALT measurements.
- In-Circuit Testing (ICT)
When a PCB has been built, an electrical probe is used for in-circuit testing to see how well it will work. It uses an electrical current to ensure that all of the parts are properly installed and functioning. It checks for shorts and open circuits and capacitance and resistance, among other things.
ICT provides a smaller amount of soldering information than AOI since it employs an electrical current instead of an image. Electronic components and soldering faults that impact circuitry can be evaluated; however, they do not provide much information regarding insufficient or excessive soldering. In-circuit testing is less reliable than AOI when it comes to today’s smaller PCBs.