1. If it is manual welding, develop good habits. First, visually inspect the PCB before welding, And use a multimeter to check whether the key circuits (especially the power supply and ground) are short circuited; secondly, use a multimeter to test whether the power supply and ground are short circuited every time a chip is welded; in addition, do not throw the soldering iron randomly during welding. If the soldering tin is thrown on the welding leg of the chip (especially the surface bonding element), it is not easy to find it.

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

3. Short circuit found. Take a board to cut the line (especially suitable for single / double-layer boards). After cutting, power on each part of the functional blocks respectively and eliminate part by part.

4. Use the short-circuit positioning analyzer.

5. If there is a BGA chip, all solder joints are covered by the chip and cannot be seen, Moreover, it is a multi-layer board (more than 4 layers). Therefore, it is best to separate the power supply of each chip and connect it with magnetic beads or 0 ohm resistance in the design. In this way, when there is a short circuit between the power supply and the ground, disconnect the magnetic beads for detection, and it is easy to locate a chip. Due to the great difficulty of BGA welding, if it is not automatic welding by the machine, the two adjacent power supply and the ground will be short circuited if you pay little attention.

6. Care must be taken when welding small surface mount capacitors, especially the power filter capacitors (103 or 104), which are in large quantity and are easy to cause short circuit between power supply and ground. Therefore, the best way is to test the capacitance before welding.