How To Identify a Short Circuit on PCB? Answered!

When constructing a PCB, you can face many problems that can damage the board, one of the most damaging and troublesome disasters a PCB can face is a short circuit. The short circuit can happen anywhere along with the board’s framework and result in devastating effects.

From destroyed components to overheating circuitry, short circuits are a dangerous threat to PCB assembly and construction; however, there are several ways to find and fix them, protecting your PCB from their consequences.

How To Identify a Short Circuit on PCB?

Several signs help you identify a short circuit on a PCB; they can vary from undetectable errors to visual damage; the undetectable errors can be detected using certain tests. For example, you can hear a “pop” sound or see an arcing in components when having a short circuit.

The visual errors are much easier to be detected as they can be very obvious; however, short circuits can occur between the input pins and other components. When the short circuits happen in the mentioned parts, they become impossible to be noticed unless you run a test on the board.

The many years of production and development of PCBs have resulted in several tests that can be used to identify a short circuit. For example, you can use digital multimeters, thermal cameras, and ground testing to identify a short circuit on PCB, and there are more specific tests.

Types of Tests for Identifying Short Circuits on PCB

Visual Test

The visual test should be done using a visual aid and a magnifying glass; you will begin by following the power source’s circuitry. Following the circuitry will make the task easier as you will be able to detect any damage and where it may occur. Pay attention if there are any whiskers around solder pads and joints, as they can result in shorts.

If short circuits have already occurred, you will notice scorching or burn marks while scanning the board; they will appear as brown marks against the board’s green. When scanning the board, pay attention if any soldered joints are cracked, as they may cause several issues.

In addition, if you notice that there are places where the solder has leaked out of place and come in contact with other components. The next sign to look for is by checking the vias in your design; you need to ensure that your plates are solid if your design requires plates.

 If your design doesn’t require plates, you will need to ensure that there are no plates because if the vias in your design are poor, it can cause short circuits and damage to other components throughout the board.

Digital Multimeter Test

The digital multimeter should be your next step if the visual test fails to reveal anything about the short circuit’s location or cause. You will need to get a digital multimeter and try to check for the physical area of the problem; it may not pinpoint the exact location of the short but will tell you where to look.

Like the previous test, you will need to start from the power source and test each pair of neighboring pads and traces. The multimeter should read a high resistance for each neighboring connection; if the multimeter reads a low resistance, then this is the short circuit you are looking for.

If you can’t find any problems in the neighboring joints, you will need to start testing on the other connections or unconnected circuits. The reading between the unconnected circuits will detect bridging.

Thermal Camera Test

Thermal cameras are considered the best and the fastest option to choose from, as they will immensely detect short circuits. Short circuits generate excessive heat output and using the thermal camera, you will be able to detect the part which produces the most heat in your board.

First, you will need to power on the board and then, using the thermal camera, start scanning the board to locate which component or joint is producing more heat than other parts, and this will be the one responsible for the short circuit you are looking for. However, thermal cameras are expensive and not an available option in every company, but if you can afford them, you should use them as they will help you immediately.

Testing Components Relative to Ground

Grounded plane or via can be found in multiplayer PCBs; they can be used to identify short circuits. In this test, you will need a multimeter; take one of the multimeter’s pins and put it on the ground, and using the other pin, start testing the connections between components on the board to check which one is disrupting power.

You will need to pay attention to an important thing when doing that test: most components have a low resistance with the ground via. Therefore, you might confuse between a functional connection and a short circuit if you are not paying enough attention.

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Testing Components Individually

In the previous test, you tested the connection between the components on the board; in this test, you will be testing the component themselves. A flawed component can look like a functional one; therefore, it’s difficult to predict if the component has an issue before your install it.

Using a digital multimeter, start testing the components; however, the problem can be in the layout of your board because if the joints of your components are too close to each other, this can lead to a short circuit. Therefore, you will need to test the resistance on the pins and pads of your components to ensure they are functioning properly.

If you have reached this point and there are still no issues, the next thing is to test the connection between the pads or the pins and the ground; this step will ensure no issues.

Destructive Testing

The last test to use if you still have not found any issues is the destructive testing; you will need to physically dismantle your board. Start by removing every component on your board, exposing the pads in the board, and then use the multimeter to test these pads to see if the problem is in them.

This test is considered extreme and should be only used if it’s your only remaining option. It will make you see which of the board’s parts has caused the short circuit through its absence.

What Causes a Short Circuit on a PCB?

As discussed earlier, short circuits can be destructive for PCBs, and you must take precautions to avoid short circuits on your PCB. Short circuits can be formed during the assembling or manufacturing process of the PCB, where during fabrication, a thin line of copper remains.

As a result, the thin line of copper creates a hairline short circuit, a short circuit can also occur during reflow soldering. If two pins are very close to each other, the soldering paste can accidentally connect them. In addition, during PCB designing, mistakes might happen, like connections between traces of different nets.

Dysfunctional components can be the reason for short circuits, and the short circuits’ issues are solved by removing them. Short circuits on PCB can happen for many reasons beyond your control, like assembly and manufacturing mistakes; however, you can reduce the chance of shorts by using the right software to design and analyze the PCB.

Conclusion

To summarize, short circuits can happen for many reasons, some of which can be beyond your control, like assembly and manufacturing mistakes. The designing process of the PCB can also result in short circuits if not well maintained; you should use the right software for designing and analyzing the PCB to avoid any shorts.

You can use many tests to identify a short circuit on your PCB; for example, you can use visual signs like burnt components, blown capacitors, a cracked IC, or brown marks on the board’s green. Meanwhile, the other tests will require tools like a digital multimeter or a thermal camera.

The last option is destructive testing, where you remove each component on the board and test the exposed parts to know where the problem is. Destructive testing should be your last resort if all tests fail to reveal the short circuit’s location or reason.