PCB Tech - How to check and prevent short circuit of PCB circuit board?

PCB circuit board short circuit is the most common problem. There are generally two situations for short circuit. One is that the PCB circuit board has reached a certain service life. The second situation is that the inspection work in the production of PCB circuit boards is not in place. But these small mistakes in production are very harmful to the entire PCB circuit board, and it is likely to cause scrap. So how do we check and prevent short circuit boards? Youliang will introduce to you.

1. A short circuit is found. Take a board to cut the line (especially suitable for single/double-layer board cut lines after each part of the functional block is energized separately, and part of it is excluded.

2. Be careful when welding small-size surface-mount capacitors, especially power supply filter capacitors (103 or 104), which may 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.

3. If it is manual welding, develop a good habit.

(1) First, check the PCB board visually before soldering, and use a multimeter to check whether the key circuits (especially the power supply and the ground) are short-circuited;

(2) Every time a chip is soldered, use a multimeter to test whether the power supply and the ground are short-circuited;

(3) Don't throw the soldering iron randomly when soldering. If you throw the solder onto the solder feet of the chip (especially surface mount components), it will not be easy to find.

4. Open the PCB diagram on the computer, light up the short-circuited network, and see which place is closest to it. It is most likely to be connected. Pay special attention to the short circuit inside the IC.

5. Use a short-circuit location analyzer, such as: CB2000 short-circuit tracker, QT50 short-circuit tracker, ToneOhm950 multi-layer circuit short-circuit detector, etc.

6. If there is a BGA chip, it is invisible because all the solder joints are covered by the chip, and it is a multilayer circuit board (above 4 layers),

Therefore, it is best to separate the power supply of each chip during the design and connect it with magnetic beads or 0 ohm resistors. In this way, when the power supply and the ground are short-circuited, the magnetic bead detection is disconnected, and it is easy to locate a certain chip. Because the welding of BGA is very difficult, if it is not automatically welded by the machine, a little carelessness will short-circuit the adjacent power supply and the ground two solder balls. The inspection work of PCB circuit boards cannot be ignored. Every step must be inspected carefully, and any suspicious points must not be overlooked in the production process. This can reduce the rework rate and product scrap rate, and avoid unnecessary loss.