The circuit board design and test points are not used in the production of PCB boards, but after the PCBA is completed, ICT tests are performed to test whether the circuit board soldering has problems and whether the performance meets the requirements.
The circuit board also needs to be tested during PCB production to see if the circuit is open or short-circuited. This is useful for the needle bed, testing against each network point.
The bare board PCB is okay, but when the PCBA is good, it is different, and the components are all soldered. Especially for SMT components, if a needle bed is used, the SMT components are easily damaged if the needle is stuck, what should I do? It is necessary to add additional test points on each circuit network for the needle bed to connect. In this way, the needle bed will not damage the SMT components, and the needle bed will be pressed to a flat test point. The test will be more accurate. In the early years, it was stipulated that 90% of the network should be tested.
There are some shortcomings in testing with a needle bed that are unavoidable. There is a limit to the size of the needle and the minimum distance between the needle and the needle. It may be somewhat difficult for high-density circuit boards.
There are still so many test points, it is really stretched for high-density circuit board space, and it is definitely unrealistic. Now there are a lot of non-test points, there are other test methods. Such as JTAG test, X-REY test, AOI test. However, these tests cannot replace ICT tests 100% in some places.