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PCB circuit board inspection and prevention of short circuit
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Electronics repair experience one of the most problem is short-circuited , harm caused by a short circuit on the PCBA quite large , small burn components , large PCBA scrapped. We only try to avoid short circuit , we must grasp miss every suspicious spot every step of production , check.
1 If it is manual welding , to develop good habits , first of all, to be visually inspected again before soldering PCB board and use a multimeter to check whether the short circuit critical circuit ( especially power and ground ) ; secondly , finished a chip on each welding multimeter test the power and ground are shorted ; addition, do not mess soldering iron rejection , if the solder flung chip solder feet ( especially surface-mount components ) , not easily found .
2 Open PCB diagram on the computer , lights shorted network from the nearest place to see what the most likely to be connected to the piece. Particular attention to the IC internal short circuit.
3 found that a short circuit . Take a plate to secant ( especially for single / double plate ) , secant function blocks after each part separately energized, part by part excluded.
4 Use shorted positioning analyzers, such as: Singapore PROTEQ CB2000 shorted tracker , Euro RSCG Hong Kong Science and Technology QT50 shorted tracker , British POLAR ToneOhm950 MLB Road shorted detectors and so on.
5 small size surface mount capacitor welding must be careful, especially in the power supply filter capacitor ( 103 or 104 ) , quantity, it is likely to cause a short circuit power and ground . Of course, sometimes bad luck , will encounter the capacitor itself is short-circuited , so the best way is to weld before the first capacitance detection again.
6 If there BGA chips, since all joints are covered with invisible chip , and it is the multilayer ( Layer 4 and above) , it is best in the design of each chip's power split open , with beads or 0 Euro resistor is connected , so that when the power shorted to ground , disconnect bead detection , it is easy to locate a particular chip. As the BGA soldering is difficult, if not automatic welding machine , little attention will put two adjacent power and ground balls shorted.
1 If it is manual welding , to develop good habits , first of all, to be visually inspected again before soldering PCB board and use a multimeter to check whether the short circuit critical circuit ( especially power and ground ) ; secondly , finished a chip on each welding multimeter test the power and ground are shorted ; addition, do not mess soldering iron rejection , if the solder flung chip solder feet ( especially surface-mount components ) , not easily found .
2 Open PCB diagram on the computer , lights shorted network from the nearest place to see what the most likely to be connected to the piece. Particular attention to the IC internal short circuit.
3 found that a short circuit . Take a plate to secant ( especially for single / double plate ) , secant function blocks after each part separately energized, part by part excluded.
4 Use shorted positioning analyzers, such as: Singapore PROTEQ CB2000 shorted tracker , Euro RSCG Hong Kong Science and Technology QT50 shorted tracker , British POLAR ToneOhm950 MLB Road shorted detectors and so on.
5 small size surface mount capacitor welding must be careful, especially in the power supply filter capacitor ( 103 or 104 ) , quantity, it is likely to cause a short circuit power and ground . Of course, sometimes bad luck , will encounter the capacitor itself is short-circuited , so the best way is to weld before the first capacitance detection again.
6 If there BGA chips, since all joints are covered with invisible chip , and it is the multilayer ( Layer 4 and above) , it is best in the design of each chip's power split open , with beads or 0 Euro resistor is connected , so that when the power shorted to ground , disconnect bead detection , it is easy to locate a particular chip. As the BGA soldering is difficult, if not automatic welding machine , little attention will put two adjacent power and ground balls shorted.