What is the cause of the PCB short circuit and how to detect it?

Have you ever encountered a situation where your smartphone suddenly becomes a hand warmer or stubbornly refuses to charge? Or your computer malfunctions and shuts down suddenly without any warning. A short circuit in the PCB is likely to be the source of the problem. A PCB short circuit is any bad connection between two points in an electronic circuit through which current bypasses the normal current path. This can be a very headache, causing electronic products to not work properly, or even damage the entire equipment. Therefore, it is very important to find it in time. In this blog, we will guide you to understand the cause of PCB board short circuit and ways to detect and avoid this problem. Let's continue reading.

Common causes of PCB short circuit

External pollution: Over time, dust and moisture can damage the PCB. They introduced substances that corroded the circuit board, or added conductive materials that changed the way the circuit board worked, causing a short circuit.

Conductive anode wire (CAF): Salt or metal fragments stuck in the PCB layer may cause problems. When the voltage is high, they will begin to react, forming conductive wires in the glass fiber. This is called CAF and may cause a short circuit in the inner layer of the PCB.

Poor welding: If the welding is wrong, a short circuit may occur. Placing parts too close, not aligning well, or using too much solder paste can create a short circuit path.

PCB design errors: Some short circuits occur due to design errors. Failure to check the design or simulate production well may lead to poor layout, no gaps between traces, or incorrect placement of parts.

The main way to find PCB short circuit

Visual inspection

Use a magnifying glass to view the PCB and check for any problems, such as welding connections between pins, copper areas that are not completely etched, or tiny short circuits. Visual inspection is usually the first step in identifying the location of the short circuit.

Use a multimeter

Use a multimeter to locate the physical location of the short circuit. Starting from the power supply, test each set of traces and PCB pads. They should display resistance readings. If you encounter a reading, it indicates that there is a circuit. Also test the circuits, because low readings between them may indicate a bridge.

Use a thermal imager

If you can, using the camera will be very helpful. Short circuits often cause heat generation. Power up the PCB. Use the camera to identify parts or joints that are hotter than other parts or joints, and point to locations where short circuits may occur.

Check the components relative to the ground

In a PCB with a ground vias or ground plane, you can check for a short circuit by grounding one pin of the multimeter and touching the other pin on the assembly. A low resistance reading may mean that there is an interruption in the power path, although some components will naturally have resistance when grounded.

Check each component separately

To verify the functionality, use a multimeter to test each component separately. Read the resistance readings on the pads and pins. Check the connection between the component and the ground. Defective components may not be easily identified by inspection.

Destructive testing

As a last resort, physically disassemble the PCB by removing the components and re-running the multimeter test on the exposed pad. This may help identify the component or area that caused the short circuit. Please note that this is an extreme form of testing and can only be used as a last resort because it may further damage the PCB.

How to prevent PCB short circuit?

Prevention is an active measure, which is suitable for short-circuiting during PCB design, construction and operation.

First, best practices will help designers ensure that the separation and insulation between conductors and other electrical equipment is done correctly. In this way, no unwanted bridges will be formed.

Secondly, after PCB manufacturing and operation, daily maintenance and inspections are required. It should be cleaned regularly to remove dust, moisture and other conductive particles. However, appropriate tools and cleaning solutions should be used to avoid PCB damage.

Third, testing and troubleshooting are also important preventive measures. Multimeters are very useful for identifying incorrect connections or short circuits on the PCB. System testing methods from power supplies to various other components and connections can help identify potential problems before they become long-term problems.

Finally, strict quality control in the manufacturing process and compliance with industry standards and best practices can greatly reduce the risk of short circuit. Manufacturers should also consider environmental factors, such as providing appropriate shielding or housings for PCBs to ensure that they are not affected by external factors.

Final thoughts

The prevention and detection of PCB short circuits are very important to ensure the reliability and service life of electronic equipment. Short circuit may be one of the many causes caused by design problems or environmental factors, but the risk can be greatly reduced by actively taking measures. Following industry best practices in design, strict quality control in the manufacturing process, regular inspections and maintenance are all very important preventive measures.