PCB short circuit analysis and prevention methods

During the PCB manufacturing process, engineers and technicians are exposed to a variety of potential risks that could compromise the integrity of each board. Short circuits are one of the most troublesome and destructive PCB common problems that can occur on a circuit board. This FS Tech Blog article discusses several methods for detecting and fixing PCB short circuits. Keeping these things in mind will help you make changes that will hopefully save your work.

Short circuit burnt PCB board
Figure 1: Damaged PCBA board due to short circuit

Subtle mistakes lead to PCB shorts

This can happen anywhere along the framework of a board, and when it does, it can have several disastrous consequences. There are many reasons for a PCB short circuit, misalignment when installing components, secondary damage caused by rework, and it can also be caused by a minute particle that becomes lodged between the pins of an IC chip. The construction and installation of PCBs are vulnerable to the danger posed by short circuits, which can cause the circuitry to overheat and even destroy PCB components. Either a solder bridge connecting neighbouring pins or vias is to blame, or a badly built PCB board is to blame for the issue. For finding the cause of the short circuit, we need to conduct a PCBA failure analysis according to the specific situation.

How to find short circuit on pcb

The results of a short circuit might range from immediately observable damage to mistakes that will not become apparent until the product is put through further testing. On the other hand, sometimes more subtle shorts might develop between the input pins or other components, and the harm caused by these shorts will not become apparent until you run the starting tests. Following are some methods to identify PCB board short circuit.

Visual Inspection

Manual detection of PCB shorts
Figure 2: Visually Inspecting a PCB

Examining the surface of the PCB very closely is the first thing you should do when trying to find short circuits on a PCB. During the examination of the circuit board, you should make use of a magnifying glass or a microscope with a modest magnification if you have access to either of these tools. It will be easier to keep track of where damage may occur if you begin by tracing the circuitry from the power supply, as this will be the starting point. Keep a look out for any whiskers around solder joints and pads since they might cause shorts if you do not watch out for them. If there has previously been a short, there may be evidence of it in the form of burn scars or scorching. These will stand out against the green background of the board because they will have the colour of a scorch mark, which is brown.

Thermal/Infrared Camera Inspection

PCB picture under thermal/infrared camera
Figure 3: Thermal Inspection of PCB Short Circuit

Using a thermal imaging camera to find the location of a PCB short isn’t affordable for all businesses, but it’s undeniably effective. Since short circuits generate a great deal of heat, a thermal camera may be used to pinpoint exactly where on the board the problem lies. Turn the power on and look for any component or solder joint that is much hotter than the others; these are the sites of your shorts. Set the current to the lowest possible setting. The sooner the short is detected, the less harm it may inflict.

Comprehensive PCB short circuit detection method

There are many ways to find PCB shorts here.The first step is to inspect a circuit board with a reliable eye. In addition to this step, there are numerous more techniques(need to use pcb short finder).

Digital Multimeter – the most common pcb short circuit finder

Digital Multimeter
Figure 4: Short Circuit Testing with Digital Multimeter

Checking the resistance between the various points in the circuit is one way to determine whether there is a short circuit on a circuit board. If a visual check does not offer any hints as to the position of the short circuit or the source of it, you should take a Multimeter and attempt to trace down the physical place on the printed circuit board where the problem is occurring. The strategy of using a Multimeter has mixed ratings in most electrical communities; yet, tracing your short circuit test locations might assist you determine what is not the issue in your system.

The possibility of internal or external bridging exists if an exceptionally low resistance is detected between two conductors that should be in different circuits.

Testing Short Circuit relative to Ground

The presence of a short that involves a grounded route or ground plane is of particular significance. Multilayer printed circuit boards (PCBs) that include an inner ground plane will have a return channel through a via near the components. This return path offers a handy spot to check all other vias and pads on the surface layer of the board. Place one probe on a ground connection and move the other probe around the board to contact with various conductors.

Destructive Testing

Destruction of PCB in order to detect short circuit
Figure 6: Destructive Testing of PCB

If none of the preceding tests provide any results, you will need to conduct the ultimate test, which involves physically disassembling your board. You will be able to determine whether these are the issues by removing each component one at a time and then doing Multimeter tests on the pads that are now exposed. This is an extreme kind of testing, and it ought to be saved for when all other options have been exhausted. In time, you will be able to determine which components of the board are missing, which in turn created a short. Testing with a Multimeter will not reveal every problem with a component but doing so will enable you to remove the problematic component and then replace it later.

Frustrating as they may seem, short circuits are quite common. Hopefully, you will be able to identify and fix these issues with the aid of the diagnostic tools quickly and easily.

How to Prevent PCB Short Circuit

Make sure you have thorough in-circuit test rule checking, for mistakes, design flaws, and manufacturing tolerances, if you do not want to have to go through the agony of hunting out short circuits. To avoid PCB short circuits, you should investigate their causes thoroughly. Sometimes, electrical shorts occur in the production or PCB assembly process. A hairline short is produced when even a tiny amount of copper is left behind at the end of the manufacturing process. It is possible for a short circuit to occur during the reflow soldering process. 

Sometimes malfunctioning components, rather than the PCB board itself, are to blame for the short. To fix the problem, just take out the broken part.

When working with PCBA, routine responsibilities include rewriting designs and changing components as required. With the FS Tech’s Turnkey PCBA Service, it is possible to save both time and money by cooperating with a partner who is skilled in PCBA testing, assembly, and production.

Short circuit is one of the most common PCB faults and not the only one. We need to pay attention to every link in the design, manufacturing and use process. Here are some articles on the topic of faults:

PCBA fault analysis and defect resolution measures

How to desolder components from PCBA

PCB Component Placement Orientation Guidelines

PCB CAF Troubleshooting Guide

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