Check and prevent 6 aspects of PCB circuit short circuit

Difficult Problems:

How to check and prevent short circuit of PCB board?

Short circuit of pcb circuit board is the most common problem. There are two cases of short circuit. One is that the pcb circuit board has reached a certain service life. The second case is that the inspection work in the pcb board production is not in place. However, the small mistakes in these productions are very harmful to the entire pcb circuit board, which is likely to cause scrapping. So how do we check and prevent the short circuit of the board, the following small series to introduce to you.

1. Found a short circuit. Take a board to cut the line (especially suitable for single/double board secant, then power each part of the function block separately, part of which is excluded.

2, small size surface mount capacitor must be careful when soldering, especially the power supply filter capacitor (103 or 104), the number is large, it is easy to cause the power supply and ground short circuit. Of course, sometimes the luck is not good, the capacitor itself is short-circuited, so the best way is to check the capacitance before soldering.

3. If it is artificial welding, it is necessary to develop good habits.

(1) First, visually inspect the PCB board before soldering, and use a multimeter to check whether the critical circuit (especially the power supply and ground) is short-circuited;

(2) Use a multimeter to measure whether the power supply and ground are short-circuited each time a chip is soldered.

(3) Do not smash the soldering iron during soldering. If the solder is soldered to the soldering legs of the chip (especially surface-mount components), it is not easy to find.

4. Open the PCB diagram on the computer, illuminate the short-circuited network, and see where it is closest to it. It is most likely to be connected. Pay special attention to the internal short circuit of the IC.

5. Use short-circuit positioning analyzer, such as: CB2000 short-circuit tracker, QT50 short-circuit tracker, ToneOhm950 multi-layer board short-circuit detector.

6. If there is a BGA chip, since all the solder joints are invisible by the chip cover, and it is a multi-layer board (more than 4 layers), it is best to separate the power of each chip at the time of design, using magnetic beads or 0 ohms. The resistor is connected so that when the power supply is shorted to the ground, the magnetic bead is detected and it is easy to locate a certain chip. Due to the difficulty in soldering the BGA, if it is not the machine's automatic soldering, the adjacent power supply and ground solder balls will be short-circuited with a little care.

The inspection work of the pcb circuit board can not be ignored. Every step must be done properly. It must be treated with care. No suspicious points can be placed in the production process. This can reduce the rework rate and product scrap rate and avoid unnecessary. loss.