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Test method of single side circuit board for short circuit phenomenon

2023-04-02

The quality of some single-sided circuit boards with micro short circuit and short circuit can not be guaranteed by ordinary low-voltage computer board measuring machine. Once they flow into the hands of users, it will affect our own reputation. The development of high-voltage computer board measuring machine ensures the quality of PCB circuit board and 100% qualified rate. Next, let's talk about the test process.


When testing the single-sided circuit board with low voltage for the first time, the circuit board test is all OK, and the short circuit is tested with 300V high voltage for the second time. For the third time, the ordinary low voltage is used for retest, and the short circuit board measured for the second time is also determined as short circuit. Use the resistance gear of multimeter to measure the short-circuit point. The welding between two wires is short-circuit, and the average resistance is 6.7 ohms. Therefore, it should be considered as complete short circuit rather than micro short circuit. Then check the short circuit with a high-power magnifying glass, and the short circuit point cannot be accurately checked (it should be the reason why the finished product has solder resist ink).


From the test process of single-sided circuit board and its resistance value, it can be determined that the protruding edge is produced by etching side etching, and then the protruding edge is broken by the plate grinding process to form a bridge between the wires, and then printed with green oil, so that the bridge is not a complete short-circuit bridge. In this way, the first single-sided circuit board test is low voltage, so it is naturally impossible to detect the bridge short circuit. The second is high voltage. First, it is a micro short circuit, and then high voltage breakdown welding (because the copper wire is very small, it can be welded to form a short circuit without great power. If the tester manufacturer can increase the allowable power of its short circuit test current, it can burn out the bridge contact, we can hardly see this phenomenon). Therefore, the third low-voltage computer board tester can test the short-circuit point, and its resistance value is only 6.7 ohms on average.


The simplest and most economical and feasible method is to purchase a new plate grinding machine or improve the existing plate grinding machine, adopt rocking grinding brush, volcanic ash throwing brush or nylon brush with low mesh, and then wash it with high pressure. Especially, the water washing section should have a filter device to prevent the foreign matter that can cause short circuit from polluting the plate surface again. The plate grinding machine can remove the copper wire and protruding edge formed by side corrosion (the dust sticking machine also has a certain removal effect). High voltage tester shall be selected for single-sided circuit board and newly purchased computer tester, which can reduce the occurrence of micro short circuit and short circuit of circuit board. This short circuit phenomenon usually occurs in single panel and high-density circuit boards.