Some micro short circuit, short circuit board products, to ensure the customer complaints to the customer does not flow into the common low voltage measuring machine computer test. Usually, circuit board manufacturers have the problem to computer measuring machine suppliers, so as to promote the development of computer measuring machine. But with high pressure measuring machine also can not guarantee the qualified rate of 100%.
Sometimes for the first time, low voltage test circuit circuit board testing of all OK, and then test second 300V high voltage short circuit test. Third times and common low voltage test, short circuit board second times measured also for determination of short circuit. With a multimeter resistance profile measuring the short-circuit point between two lines of welding inventory for the short circuit, the average resistance value is 6.7 ohms. It should be regarded as short instead of micro short circuit. Then use the high magnification check short-circuit phenomenon can not accurately check out the short-circuit point (should be finished with solder ink).
From test procedure and its resistance value can be identified as: etching lateral erosion produce process along, and then by the process of grinding plate so that the protruding along the fault down forming a bridge between the conductors, reprinted on the green makes the bridge is not completely short-circuit bridging. This is the first test of low pressure natural bridge could not be detected in short circuit. The second pressure first measure the micro short circuit, and high voltage breakdown welding (because the wire is very small so it does not need to be great power can do welding to form a short circuit. If testing machine manufacturers can improve the short-circuit test current charge Xu power will be able to burn the bridge contact. It is hard for us to see this phenomenon). So third computer test machine to test low voltage short circuit, and its resistance value is only an average of 6.7 ohms.
Is the simplest and most economical and feasible method for purchase of new grinding machine or improving existing grinding machine, adopting swing grinding brush and with volcanic ash polishing brush or low mesh nylon brush, and then the high-pressure washing, especially washing section, are the best filtering device, to prevent causing short circuit of the foreign body pollution to the surface, grinding machine to undercut the copper wire and projecting edge removal (sticky machine also has certain removal effect). At the same time, the purchase of new computer testing machine should be used for high pressure, can reduce the circuit board micro short circuit and short circuit. This short circuit phenomenon usually appears in a single panel and high density circuit board.