Why add test points to circuit board design?
Circuit board design and test points are not needed in the production of PCB board, but after the completion of PCBA, ICT test is conducted to test whether there is a problem in the welding of circuit board and whether the performance meets the requirements.
During the production of PCB, the circuit board also needs to be tested to see whether the circuit is open or short circuit. This can be used as a bed of needles to test against various network points.
If it just is bare PCB there is no a problem. But if PCB assembly process is finished, it is different, the components are welded. Especially for SMT components, if you use a needle bed, it is easy to damage the SMT components by poking them with a needle, then what should you do?
It is necessary to add test points on each line network to connect the needle bed. In this way the pin bed will not damage the SMT element and the pin bed will be pressed to a flat test point. The test will be more accurate.
In the early years, there are provisions for 90% of the network to add test points. Some of the drawbacks of using a needle bed for testing are unavoidable. There is a limit to the size of the needle and the minimum spacing between the needles. This may be difficult for high density circuit boards.
There are so many test points, for the high-density circuit board space, is really limited, certainly is not realistic. Now there are a lot of untested points, there are other ways to test. Such as JTAG testing, X-REY testing, AOI testing. But these tests are not a 100% substitute for ICT testing in some places.
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