Many engineers do not want to see a short circuit in the PCBA. What should I do if the immersion gold fr-4 PCB is a short circuit test and short-circuited? Why is there a short circuit on the circuit board, and if there is a short circuit, how can we troubleshoot it?
There are usually two short-circuit situations. First, the hasl lead PCB has reached a certain service life. The second situation is that the inspection work in the production of the fr4 multilayer PCB is not in place. However, these small errors in production have caused great harm to the entire PCB circuit board and are likely to lead to scrap. So how do we check and prevent short circuits on the board?
1. Open the electronic printed circuit diagram on the computer, light up the short-circuited network, and see where the closest one is, which is most likely to be connected to one piece. Pay special attention to the short circuit inside the IC.
2. Use a short-circuit location analyzer, such as Singapore PROTECH CB2000 short-circuit tracker, Hong Kong Lingzhi Technology QT50 short-circuit tracker, British POLAR ToneOhm950 multi-layer board short-circuit detector, etc.
3. Be careful when soldering small surface mount capacitors, especially power filter capacitors (103 or 104), which are large in number and can easily cause short circuits between power and ground. Of course, sometimes with bad luck, the capacitor itself will short out, so the best way is to test the capacitor before soldering.
4. If it is manual welding, develop a good habit. First, visually inspect the custom-made PCB before soldering, and use a multimeter to check whether the key circuits (especially the power supply and ground) are short-circuited; secondly, after each chip is soldered, use a multimeter to measure whether the power supply and ground are short-circuited; In addition, do not throw the soldering iron at will when soldering. If solder gets thrown on the feet of the chip (especially surface mount components), it’s hard to find it.
5. If there is a BGA chip, since all the solder joints are covered by the chip and invisible, and it is a multi-layer board (more than 4 layers), it is best to separate the power supply of each chip during design, and use magnetic beads or 0 ohms. Resistor connection, so that 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. Due to the difficulty of soldering the BGA, if it is not automatically soldered by the machine, it will short-circuit the adjacent power supply and the two solder balls of the ground if you are not careful.
6. If a short circuit is found, take a board to cut the copper circuit board (especially suitable for single-layer/double-layer boards). After cutting, energize each part of the function block separately and eliminate it part by part.