- Jan 09, 2018 -
PCB circuit board Short - circuit inspection and prevention
One of the most common problems in the maintenance of electronic products is short circuit, which causes great harm to PCBA, ranging from burning components to PCBA scrapping. We can only avoid short circuit as far as possible. Must grasp every step of production, check every suspicious spot.
1. If it is welding by hand, to form a good habit, first of all, before welding to check the PCB board, and use multimeter to check the key circuits (especially power and ground) whether short circuit; Secondly, each time a chip is welded with a multimeter to determine whether the power supply and the ground are short-circuited; In addition, do not throw soldering iron, if the solder to the chip solder foot (especially the surface components), it is not easy to find.
2. Open the PCB diagram on the computer, light up the short-circuited network, and see where the nearest place is most easily connected to one. Pay special attention to the IC internal short circuit.
3. It is found that there is a short circuit phenomenon. Take a board to cut the wire (especially suitable for single / double layer board), after cutting each part of the functional block is separately electrified, part of the elimination.
4. Use short circuit location analyzer, such as: Singapore PROTEQ CB2000 short circuit tracker, Hong Kong Ling Chi Technology QT50 short circuit tracker. UK POLAR ToneOhm950 multilayer circuit short circuit detector and so on.
5. Be careful when welding small size watch mount capacitors, especially power filter capacitors 103 or 104, which can easily cause a short circuit between the power supply and the ground. Of course, sometimes bad luck. The capacitance itself will be encountered short circuit, so the best way is to check the capacitance before welding.
6. If there is a BGA chip, because all solder joints are not visible by the chip, and the multilayer board is more than 4 layers, it is best to divide the power supply of each chip in the design, using magnetic beads or 0 ohl resistance connection. When there is a short circuit between the power supply and the ground, the magnetic bead detection is disconnected, and it is easy to locate a certain chip. Because of the difficulty of BGA welding, if not machine automatic welding. If you don't pay attention, you will short the adjacent power source and the two solder balls.
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