In-circuit testing, or ICT, is an extremely robust testing method that measures each component on a printed circuit board to ensure it is correct and in place. It is intended specifically for printed circuit boards that are unlikely to have revisions, and while it is an extremely effective method of PCB testing, it is not ideal for all applications.

  ICT is conducted by testing a populated Multi-layer PCB with electrical probes, testing aspects like open and short circuits, resistance, and capacitance. This is often done with a tool called a bed of nails tester, which are laid out in a way that matches the design of the printed circuit board.

  In-circuit testing provides some of the best results to ensure that your Multi-layer PCB is functionally sound, and is well suited for larger connections and ball grid arrays. It is also one of the most expensive testing methodologies available due to the cost of assembly bed of nails fixtures, and must be chosen early in the manufacturing process. Thus, it is mostly used for products for design-for-manufacturing as the objective.

  ICT also does not test for continuity through connectors. However, this can be resolved by pairing it with the correct inspection methodologies.