If it is manual welding, it is necessary to develop good habits. Firstly, visually inspect the PCB board before welding, and use a multimeter to check whether key circuits (especially power and ground) are short circuited; Secondly, every time a chip is soldered, use a multimeter to measure whether there is a short circuit between the power supply and ground; In addition, do not throw the soldering iron indiscriminately during soldering. If the soldering tin is thrown onto the solder pins of the chip (especially surface mount components), it is not easy to detect.

2. Open the PCB diagram on the computer, light up the short circuit network, and see where it is closest to where it is most likely to be connected. Pay special attention to internal short circuits in the IC.

3. A short circuit was found. Take a board to cut the thread (especially suitable for single/double layer boards), and after cutting the thread, power on each part of the functional block separately, and exclude some parts.

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

If there is a BGA chip, as all solder joints are covered by the chip and cannot be seen, and it is also a multi-layer board (more than 4 layers), it is best to separate the power supply of each chip during design and connect it with magnetic beads or 0 ohm resistors. This way, when there is a short circuit between the power supply and ground, the magnetic beads can be disconnected for detection, making it easy to locate a certain chip. Due to the high difficulty of BGA welding, if it is not automatically welded by the machine, a slight carelessness will cause a short circuit between the adjacent power supply and the two welding balls on the ground.

6. When welding small-sized surface mount capacitors, be careful, especially when there are many power 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.