If a PCB is already going through ICT and some additional inspection method is desired to increase first pass test yield rates, what are the advantages/disadvantages of AOI vs XRay? The most common problems seen are missing or skewed components and insufficient solder. ICT coverage is not 100%, due to board space and frequency limitations.
We have found a significant number of PBGA problems associated with physical deformation of the package. Deformations such as dishing (potatoe chipping) and delamination under the die (popcorning). These can be detected by x-ray by the variation pattern of the ball bonds, I doubt that AOI would detect these process related problems. Cold solder joints frequently appear in the x-ray image as irregularly shaped bonds again can easily detected by AOI.