Causes and analysis of PCB micro-shorting and short-circuiting

Currently, PCB short circuit and micro-short circuit is inevitable, usually PCB manufacturers push the micro-short circuit and short circuit problems to PC tester suppliers, thus promoting the development of high-voltage PC testers. However, the same 100% pass rate cannot be guaranteed with a high voltage board tester.

Sometimes a board passes the first low voltage test. The second 300V high-voltage test with a short circuit, the third time was also determined to be a short circuit.

how to test pcb board with a multimeter,With a multimeter for resistance file measurement system short circuit point between the two lines of the soldering plate point for short circuit, the average resistance value of 6.7 ohms, so it should be recognized as a completely different short circuit in China rather than a micro-short circuit, and then with a high magnification can be checked whether the short-circuit failure phenomenon, but can not accurately and timely check the existence of a short-circuit point (it should be the finished product of the enterprise has a soldermask ink reasons).

From the test process and its resistance value can be considered: etching side of the edge, and then through the abrasive plate process will be the edge of the decomposition of the formation of bridges, and then printed on the green, so that the bridge is not completely short-circuited. So the first test of low voltage naturally can not measure the bridge short circuit. The second time for high-voltage first measure its tiny short circuit, and then high-voltage breakdown soldering (because the copper wire is very small, so you do not need a lot of power to do short-circuit soldering. If the tester manufacturer would increase the allowable power of its short-circuit test current to burn the bridge, we would hardly see this phenomenon). As a result, a third low-voltage computerized tester can detect short-circuit points with a resistance averaging only 6.7 ohms.

As mentioned earlier, the 300V high voltage board tester also complained of a short. Examining the returned bad shorted boards, I saw that the third bad shorted board measured for the same reason. Because resistance welding (green oil) silkscreen will aggravate the insulation of the bonded copper wires, can not be measured with a high-voltage computer tester,pcblink 1oz vs 2oz Copper in the semi-finished product handling, assembly, wave soldering, testing process will be bridged to form a short circuit. Sometimes the short circuit board measured by low voltage tester is bent and tapped, sometimes the short circuit will disappear. When there is no high-voltage computer board tester, because of uneasiness, the tested ok board will short-circuit again. Most of the problems are in the side etching of soldermask ink, pattern making, and pre-treatment lines. The first two processes are difficult to solve this problem, the main thing is to ensure that the pattern making line width and line spacing, to prevent some of the lines are too close to ensure that the quality of the side etching when etched. Reduced the generation of micro-short circuit phenomenon in the high-voltage test.

multimeter PCB short circuit

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