How to test circuit boards with short circuit
Some single-sided circuit boards with micro-short-circuit and short-circuit phenomena cannot be guaranteed with ordinary low-voltage computer test boards. Once they flow into the hands of users, it will affect our own credibility. The development of high-voltage computer testing machine guarantees the quality of PCB circuit boards and 100% pass rate. Next, the board manufacturer talks about the test process.
The first time the low-voltage test of the single-sided circuit board was OK, and the second time the 300V high-voltage test tested for short circuits. The third time was retested with ordinary low voltage, and the short-circuit board measured in the second time was also determined as a short circuit. Use a multimeter resistance file to measure the short-circuit point. The pad between the two wires is short-circuited, and the average resistance is 6.7 ohms. Therefore, it should be considered as a complete short circuit rather than a micro short circuit. Then use a high magnification magnifier to check the short circuit phenomenon. 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 of the single-sided circuit board and its resistance value, it can be identified that: the etched side etch produces a flange, and then the flange is broken by the grinding process to form a bridge between the wires, and then the green oil is printed to make the bridge incomplete. Short-circuit bridging. In this way, for the first single-sided circuit board test, it is naturally impossible to detect the bridge short circuit for low voltage. The second time is 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 a large power to be welded to form a short circuit. If the tester manufacturer can increase its short circuit test current, With sufficient power, the bridge point can be blown, and it is difficult for us to see this phenomenon). So the third low-voltage computer 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 rocking brush and use a volcanic ash throwing brush or a low mesh nylon brush, and then use high pressure washing, especially the water washing section It is best to have a filtering device to prevent foreign objects that can cause short circuits from contaminating the surface of the board again. The mill can remove the copper wires and protrusions formed by side corrosion (the dust sticker also has a certain removal effect). High-voltage machines should be used for newly purchased computer testers for single-sided circuit boards, which can reduce the occurrence of micro-short circuits and short circuits. This short-circuit phenomenon usually occurs in single-sided boards and high-density circuit boards.
