One of the most troublesome problems encountered in the maintenance of electronic products is the short circuit. The short circuit damage to PCBA is quite large, ranging from burning components to PCBA scrapping. We only try to avoid the short circuit, we must grasp every step of production, and not miss every suspicious point.
1. If it is artificial welding, it is necessary to develop a good habit. First, visually inspect the PCB board before soldering, and use a multimeter to check whether the critical circuit (especially the power supply and the ground) is short-circuited. Second, each time the chip is soldered. Use a multimeter to measure whether the power supply and ground are short-circuited. In addition, do not smash the soldering iron during soldering. If the solder is soldered to the soldering legs of the chip (especially surface-mount components), it is not easy to find.
2. Open the PCB on the computer, illuminate the short-circuited network, and see where it is closest to it, the easiest to connect. Pay special attention to the internal short circuit of the IC.
3. A short circuit was found. Take a board to cut the line (especially for single/double board). After secant, each part of the function block is energized separately, and some parts are excluded.
4. Use short-circuit positioning analyzer, such as: Singapore PROTEQ CB2000 short circuit tracker, Hong Kong Lingzhi QT50 short circuit tracker, UK POLAR ToneOhm950 multilayer board short circuit detector.
5. Care must be taken when soldering small-sized surface-mount capacitors, especially power supply filter capacitors (103 or 104), which can easily cause short-circuit between power and ground. Of course, sometimes the luck is not good, the capacitor itself is short-circuited, so the best way is to check the capacitance before soldering.
6. If there is a BGA chip, since all the solder joints are invisible by the chip cover, and it is a multi-layer board (more than 4 layers), it is better to separate the power of each chip at the time of design, using magnetic beads or 0 ohms. The resistor is connected so that when the power supply is shorted to the ground, the magnetic bead is detected and it is easy to locate a certain chip. Because the BGA is difficult to solder, if it is not the machine's automatic soldering, the adjacent power supply and ground solder balls will be short-circuited with a little care.