Automated optical inspection (AOI)

Automated optical inspection (AOI) is an automated visual inspection of printed circuit board manufacture where a camera autonomously scans the device under test for both catastrophic failure (such as missing component) and quality defects. 

It is commonly used in the manufacturing process because it is a non-contact test method. It guarantees the high reliability of Multi-CB multilayer circuit boards. 

It is especially important for the following application areas:

．Line width violations

．Spacing violation

．Excess copper

．Missing pad

．Short circuits

．High frequency

．High power loads 

Advantages

Depending on its visual methods, the AOI test can be used to detect a lot of surface defects, such as opens, shorts, incorrect components, missing components, etc.

The following are the advantage of the AOI test:

．Multiple inspection objects - AOI test works perfectly not only for PCBs but also for PCB assembly. For PCB, defects are checked such as shorts, opens, and insufficient solder. For PCB assembly, 

．Low cost -Compared with Automatic X-ray Inspection (AXI), AOI is less expensive when inspecting solder joint defects. 

．Good Flexibility –AOI test can be arranged in any stage of the manufacturing process according to needs and cost tolerance capacity. To reduce the corresponding cost and increase inspection efficiency, it's better to do the AOI test after reflow soldering. Because most of the defects are the result of the failure in the welding process. The good flexibility performance of the AOI test leads to a reduction in cost. Because once a problem is found, manufacturing or assembly parameters can be modified immediately so that subsequent products can be produced correctly