Automatic optical inspection or AOI uses visual methods to check if there’s any defect on printed circuit boards. It can detect various defects, for example, knots, scratches, stains, open circuits, shorts, etc. Besides, incorrect components, missing components, and wrongly placed components are also can be found out. AOI performs reliably and accurately, so it is widely used to perform the visual checks.
For bare PCB inspection, AOI may detect line width violation; spacing violation; excess copper, missing pad-a feature that should be on the board is missing; shorts circuits; cuts; hole breakage-a drilled hole is outside of its landing pad; wrong mounting components identified.
For printed circuit board with components, AOI may inspect its area defects; component offset; component polarity; component presence or absence; component skew; excessive solder joints; flipped component; height defects; insufficient solder joints; lifted leads; paste registration; severely damaged components; solder bridges; tombstoning; volume defects; wrong part. Besides, AOI can be used in the following locations in the SMT lines: post paste, pre-reflow, post-reflow, or wave areas.