PCB Tech - Circuit board short circuit detection method

PCB circuit board short circuit inspection method

1. When the circuit board is received, if it is soldered manually, it must develop a good habit. First, check the PCB circuit board visually before soldering the circuit board, and check the key circuits (especially the power supply and ground) with a multimeter. ) Whether it is short-circuited; secondly, use a multimeter to test whether the power supply and ground are short-circuited every time a chip is soldered; in addition, do not throw the soldering iron randomly, if you throw the solder onto the solder feet of the chip (especially surface mount components), It is not easy to find.

2. Open the PCB circuit board diagram on the computer, light up the short-circuited network, and see which place is closest to it, which is the easiest to be connected. Pay special attention to the short circuit inside the IC.

3. A short circuit is found. Take a board to cut the wires (especially suitable for single-sided PCB/double-sided circuit boards), and power on each part of the functional blocks separately after cutting the wires, and remove some of them.

4. Use short-circuit locating analyzers, such as: Singapore PROTEQCB2000 short-circuit tracker, Hong Kong Lingzhi Technology QT50 short-circuit tracker, British POLARtoneOhm950 multi-layer board short-circuit detector and so on.

5. If there is a BGA chip, since all the solder joints are covered by the chip and invisible, and it is a multilayer circuit board (PCB board with more than 4 layers), it is best to separate the power supply of each chip during the design and use magnetic Bead or 0 ohm resistor connection, so when there is a short circuit between the power supply and the ground, disconnect the magnetic bead detection, it is easy to locate a certain chip. Because the welding of BGA is difficult, if it is not automatic welding by the machine, a little carelessness will short-circuit the adjacent power supply and the ground two solder balls.

6. Be careful when welding small-size surface-mount capacitors, especially power supply filter capacitors (103 or 104), which can easily cause a short circuit between the power supply and the ground. Of course, sometimes with bad luck, the capacitor itself is short-circuited, so the best way is to test the capacitor before welding.