PCB circuit board short circuit is a very common problem in the production of circuit boards. There are generally two situations in which a short circuit occurs. One is that the PCB board has reached a certain service life. The second situation is that the inspection work is not in place in the production of PCB circuit boards. However, these small mistakes in the production of circuit boards may cause components to burn out, which is very harmful to the entire PCB board and may cause scrapping. Therefore, it is extremely important to check and control it during the production process. So what are the common types of PCB board short circuit? What are the places we need to pay attention to when checking the circuit board short circuit in PCB circuit board production?
一、Common types of circuit board short circuits
1. Short circuit can be divided into functionalities: soldering short circuit (such as tin connection), PCB circuit board short circuit (such as residual copper, hole deviation, etc.), circuit board inner layer micro short circuit, device short circuit, assembly short circuit, ESD/EOS Breakdown, electrochemical short circuit (such as: chemical residue, electromigration), short circuit caused by other reasons.
2. Short circuits can be classified according to wiring characteristics: line-to-line short circuit, line-to-surface (layer) short circuit, and face-to-face (layer-to-layer) short circuit.
二、the circuit board short circuit inspection needs to pay attention to these points
1. Open the PCB board design drawing on the computer, light up the short-circuited network, and see which is the closest and easiest to connect to one piece. Pay special attention to short circuits inside the IC.
2. If it is manual welding, it is necessary to develop good habits:
①Before soldering, check the PCB circuit board visually, and use a multimeter to check whether the key circuits (especially the power supply and ground) are short-circuited.
② Do not shake the soldering iron when soldering. If you throw the solder on the solder pins of the chip (especially surface mount components), it will not be easy to find out.
③Every time a chip is soldered, use a multimeter to test whether the power supply and ground are short-circuited.
3. A short circuit is found. Take a board to secant (especially suitable for single/double-layer boards), and after secanting, electrify each part of the functional blocks separately, and gradually eliminate them.
4. Use the short circuit location analysis instrument. Common ones are: Singapore PROTEQCB2000 short circuit tracker, Hong Kong Lingzhi Technology QT50 short circuit tracker, British POLARToneOhm950 multi-layer board circuit short circuit detector, etc.
5. Check by increasing the current: use low voltage and high current below 5V, and 3-5A high current. Under normal circumstances, the position of heat is short circuit. However, there is a low risk of doing so, and it is generally not used.
6. If there is a BGA chip, since all solder joints are covered by the chip and cannot be seen, and it is a PCB multilayer board (more than 4 layers), it is best to separate the power supply of each chip during design, and use magnetic beads or OΩ The resistance is connected, so that when there is a short circuit between the power supply and the ground, the magnetic bead detection is disconnected; it is easy to locate a certain chip. Due to the difficulty of BGA soldering, if it is not automatically soldered by the machine; a little carelessness will short-circuit the two solder balls of the adjacent power supply and ground.
7. Be careful when soldering small-sized surface-mount capacitors; especially the power filter capacitors (103 or 104), which are large in number and can easily cause a short circuit between the power supply and the ground. Of course, sometimes if you are unlucky, the capacitor itself is short-circuited, so the best way is to check the capacitor before welding.
