1. If it is manual welding, it is necessary to form a good habit. First, visually check the PCB board and check whether the key circuits (especially the power supply and ground) are short circuited with a multimeter before welding. Second, use a multimeter to check whether the power supply and ground are short circuited each time a chip is welded. In addition, do not throw the soldering iron randomly when welding. If the soldering tin is thrown on the soldering foot of the chip (especially It's a surface mount element), which is not easy to find.
2. Open the PCB on the computer, light up the short-circuit network, and see where is the nearest, and it is most likely to be connected to one piece. Pay special attention to the internal short circuit of IC.
3. A short circuit was found. Take a board to cut the wire (especially suitable for single / double board). After cutting the wire, power on each part of the function block separately, and exclude some parts.
4. Use short-circuit location analyzer, such as: Singapore proteqcb2000 short-circuit tracker, Hong Kong Smart technology qt50 short-circuit tracker, UK polartone ohm950 multi-layer board circuit short-circuit detector, etc.
5. If there is a BGA chip, because all the solder joints are covered by the chip and cannot be seen, and it is a multi-layer board (more than 4 layers), the power supply of each chip is separated during the design, and connected with a magnetic bead or 0 ohm resistance. In this way, when the power supply is short circuited to the ground, the magnetic bead detection is disconnected, and it is easy to locate a chip. Due to the difficulty of BGA welding, if it is not automatic welding, the adjacent power supply will be short circuited to the two welding balls.
6. Be careful when welding the small size surface mount capacitance, especially the special power filter capacitance (103 or 104), which has a large number, can easily cause short circuit between the power supply and the ground. Of course, sometimes bad luck, will encounter the capacitor itself is short-circuit, so before welding, first test the capacitance.
