Automatic optical inspection (AOI) is an optical structure test for printed circuit boards that can detect a relatively large number of defects, but fewer than with the functional test( FT) or the in-circuit test( ICT). On the other hand, the AOI test is not as cost and time intensive as the other test methods mentioned.
High- resolution photos are taken during the AOI test, which also makes the test reproducible. There are also AOI test systems that take stereoscopic 360° images, or images taken from different angles.
With the AOI test, mechanically defective components can be detected, in addition to press-fit defects, placement defects in SMD component assembly and through-hole technology( THT), solder defects, but not all solder bath defects.
In addition, the AOI test cannot check defects on hidden chip connections, which are located below the chips, as is the case with BGA chips. Another problem is the polarity of components such as tantalum capacitors or electrolytic capacitors, which cannot be detected and checked from the top view in the case of axially installed components. This problem can be solved with AOI systems that can take pictures from different angles. Defective electrical components cannot be detected with the AOI test.