
5. Inspection of bare PWBs
There are several possibilities, appliances and algorithms when inspecting bare PWBs
optically. These are able to inspect the copper wire-patterns on a PWB surface with high
precision. Optical inspection gives rapid and reliable results regarding the quality of the
PWB. Electrical detection methods, (e.g. ICT, Flying Probes) are slower and more expen‐
sive. Bare PWB inspecting AOIs have a special name: Automatic Optical Test (AOT)
systems. There are several research and survey papers about this topic [31]-[43] and two
manufacturers now have AOT machines [44]-[49]. In Table I a comparison between these
appliances is shown.
Figure 1. The three main part of an AOI system
Figure 2. Example for: a) linear barcode b) DMC
Materials Science - Advanced Topics390
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