How to deal with the short circuit of circuit board, circuit board and PCB?

How to deal with the short circuit of circuit board, circuit board and PCB?

SometiMES, when the circuit board is tested with low voltage for the first time, it is all OK. When the circuit board is tested with 300V high voltage for the second time, there is a short circuit. The third time, the common low voltage was used for retesting, and the second time, the short-circuit board was also determined as short circuit. Use a multimeter to measure the resistance of the short circuit point. The welding between the two wires is short circuited. 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 detected (it should be the reason that the finished product has solder resist ink).

From the test process and its resistance value, it can be determined that: the edge is produced by etching side erosion, and then the edge is broken by grinding plate process to form a bridge between the wires, and then the bridge is not completely short circuited when green oil is printed. In this way, the bridge short circuit cannot be detected when the first test is low voltage. The second time, for high voltage, it is first detected that it is a micro short circuit, and then high-voltage breakdown welding (because the copper wire is very SMAll, it does not require much power to weld to form a short circuit. If the manufacturer of the testing machine can increase the allowable power of its short circuit test current, it can burn off the bridge contact, which is difficult to see this phenomenon). So the third time, the 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 economically feasible method is to purchase a new plate grinder or improve the existing plate grinder, use a swing grinding brush and a pozzolanic polishing brush or a nylon brush with low mesh size, and then use high-pressure washing. In particular, the water washing section is preferably equipped with a filter device to prevent foreign matters that can cause short circuits from polluting the plate surface again. The plate grinder can remove the copper wires and protruding edges formed by side corrosion (the dust sticking machine also has a certain removal effect). At the same time, the newly purchased computer testing machine should be a high-voltage machine, which can reduce the occurrence of micro short circuit and short circuit on single side PCB. This short circuit phenomenon usually occurs in single panel and high-density PCB.

PCB manufacturers, PCB designers and PCBA manufacturers explain how to deal with short circuits in PCB, PCB and PCB.