PCB Tech - A remedy for short circuit of batch fixed-position circuit boards

A remedy for short circuit of batch fixed-position circuit boards

Under normal circumstances, the PCB circuit board has a short circuit, the remedy is to cut the short circuit with a knife, and then apply a layer of insulating solder mask to complete it. When there is a short circuit in a fixed place in batches, it is very troublesome to cut it by hand, time-consuming and laborious, and the quality is very insecure. When the circuit board is short-circuited after the circuit board is soldered, and the circuit board is short-circuited, and it is a short circuit in a fixed place, it is a A very headache problem. When this kind of problem occurs, the whole batch is often scrapped, and the valuable components are disassembled to reduce the loss. But the cost is still very staggering, and many circuit board manufacturers cannot afford it. In many cases, customers and circuit board manufacturers just broke up, and some of them were even left by legal means. The following recommends a simple and easy way for everyone, I hope it can help, is to use the method of CNC engraving machine, install the engraving knife on the CNC milling machine of the circuit board, make the path milling data, and short-circuit the fixed Place, use the engraving machine to carve out the correct line. All steps have been verified in actual batches in Panxin PCB Factory.

The first step: Check and analyze the situation of the problem board, and prepare for the follow-up. The surface of the circuit board on which the components are welded is generally uneven, and the fixed short-circuit area can be displayed horizontally and openly, which is convenient for the cutter of the milling machine to work. In order to make the circuit board with the device flat on the platform of the milling machine, sometimes it is necessary to make a jig, on which some positioning pins are installed according to the condition of the board, and the area corresponding to the raised device should be hollowed out on the jig. In this way, the circuit board can be flat and fixed on the platform of the milling machine.

Step 2: Engineers make the path that the carving knife needs to cut according to the short circuit. Engineering personnel in general circuit board factories have this skill.

The third step: The operator of the milling machine adjusts the depth of the engraving knife. Since the cutting edge of the engraving knife is in a V-shaped row, the deeper the knife, the wider the path cut on the circuit board. Some short circuit boards are very Precision, adjust the depth of the knife not too deep, but a shallower knife tip often fails to touch the circuit board, or touches but does not completely cut the short-circuited copper foil. So be sure to ask an experienced milling machine master to debug. This is very important and directly affects the quality of the cut.

The fourth step: the inspection of the electrical performance of the processed circuit board. Some of the cut copper foil of the circuit board may turn up or not completely cut in place, and need to be inspected and processed.

Step 5: Apply a layer of solder mask ink to the cut area and bake it to solidify.

Although the above method is a last resort, the author has tried the effect very well, and the cutting accuracy can reach the minimum line width of 0.4 mm. If the accuracy of the milling machine is sufficient, the problem of line width and line distance with an accuracy of 0.3 mm can be dealt with.
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