PCB circuit board short circuit inspection and prevention

One of the most common problems encountered in the repair of electronic products is the short circuit. The damage caused by the short circuit to the PCBA is quite large, from the burning of components to the PCBA being scrapped. We only try to avoid the occurrence of short circuits, we must grasp every step of production, and do not miss every suspicious point during inspection.

1. If it is manual soldering, develop good habits. First, visually check the PCB board before soldering, and use a multimeter to check whether the key circuits (especially power and ground) are short-circuited. Second, each time you solder a chip, Use a multimeter to test whether the power supply and ground are short-circuited. In addition, don't shake the soldering iron when soldering. If you throw the solder on the chip's soldering feet (especially surface-mounted components), it will not be easy to find.

2. Open the PCB drawing on the computer and light up the short-circuited network to see where it is closest to. It is easiest to be connected to one piece. Pay special attention to the internal short circuit of the IC.

3. Short circuit was found. Take a board to cut the line (especially suitable for single / double-layer boards). After the cut, power on each part of the function block separately, and some parts are excluded.

4. Use short circuit positioning analyzers, such as: Singapore PROTEQ CB2000 short circuit tracker, Hong Kong Lingzhi Technology QT50 short circuit tracker, UK POLAR ToneOhm950 multi-layer board short circuit detector, etc.

5. Be careful when soldering small-sized surface-mount capacitors, especially the power supply filter capacitors (103 or 104). The large number of capacitors can easily cause short circuit between power and ground. Of course, sometimes bad luck, you will encounter the capacitor itself is short-circuited, so the best way is to test the capacitor before welding.

6. If there is a BGA chip, since all solder joints are covered by the chip and invisible, and it is a multilayer board (more than 4 layers), it is best to separate the power of each chip during design, using magnetic beads or 0 ohms. Resistor connection, so that when a short circuit occurs between the power and ground, the magnetic bead is disconnected and it is easy to locate a certain chip. Due to the difficulty of welding the BGA, if it is not automatically welded by the machine, a little carelessness will short the two adjacent power balls to the ground.