Solder ball height and substrate coplanarity inspection is essential to the detection of potential connectivity issues in semi-conductor units. Current ball height and substrate coplanarity inspection tools such as laser profiling, fringe projection, and confocal microscopy are expensive, require complicated setup and are slow, which makes them difficult to use in a real-time manufacturing setting. Therefore, a reliable, in-line ball height and substrate coplanarity measurement method is needed for inspecting units undergoing assembly.

J. Li, B. L. Bennett, L. J. Karam and J. S. Pettinato, “Stereo Vision Based Automated Solder Ball Height and Substrate Coplanarity Inspection,” in IEEE Transactions on Automation Science and Engineering, vol. 13, no. 2, pp. 757-771, April 2016.