Understanding and Preventing PCB Damage: A Comprehensive Guide

Estimated reading time: 8 minutes

There are many common PCB defects, but one of the most serious is a burnt component. A burnt circuit board is a destructive problem that can lead to significant PCB damage. It can be hard to repair and difficult to find the real source of the problem. What causes a PCB to burn out? In this article, we’ll explore the causes, show you how to fix it, and discuss PCB troubleshooting techniques to prevent it from happening again.

What Causes a Board to Burn?

Before we look at the PCB failure analysis process, we need to understand the reasons a board might burn. A burnt spot on a board is often not the original defect. It is usually a symptom caused by other problems on the PCB.

There are three main reasons a PCB will burn:

• Extreme heat
• Improper component spacing
• Component failure or technician error

Extreme Heat

It is natural to think that a PCB exposed to high temperatures is more likely to burn. Most boards used in high-temperature areas are built to handle the heat. They often have a high Tg. Tg means glass transition temperature, the point where the board material starts to soften. A typical high-Tg board can handle 170°C. For safe operation, a board should be used in an environment that is at least 25°C cooler than its Tg. This is an important part of preventing PCB overheating and mitigating environmental damage.

Thermal imaging can be a valuable tool in identifying potential hot spots on a PCB before they lead to damage. Regular visual inspection can also help detect early signs of heat-related issues. Additionally, burn-in testing can be employed as part of PCB troubleshooting techniques to identify potential weaknesses in the board’s thermal management.

Why is the Tg value of PCBs important?

During production, PCBs are exposed to high temperatures. For instance, temperatures during soldering (reflow or wave soldering) can rise to more than 200°C. Additionally, the PCB itself may heat up while operating, particularly for high-power devices or high-density designs.

In these high-temperature conditions, a PCB substrate with an inadequate Tg value may soften and expand, resulting in:

• Reduced dependability: The metal holes that join the top and bottom layers are brittle.
• Delamination: The substrate may peel between layers or between the substrate and copper foil.
• PCB bent: may deform and affect functionality.

But accidents can happen. A machine can overheat. A board could be exposed to a direct flame. This will be very bad for your components. Most electronic parts do not work well above 70°C. So, designing for high-temperature applications is difficult but very necessary.

Components Are Too Close

Another major cause of a burnt board is when parts are placed too close together. This is known as improper component spacing. Components that do not have enough space around them can get very hot. This heat can then affect the parts next to them, especially components that are sensitive to heat. Improper trace routing can also lead to open circuits and signal integrity issues.

Proper component placement is crucial in preventing heat-related issues. Ensuring adequate spacing between components allows for better heat dissipation and reduces the risk of thermal damage. Additionally, using high-quality components through careful component quality control can help mitigate the risk of heat-related failures and reduce electromagnetic interference. Implementing effective EMI shielding techniques can further protect sensitive components from interference.

In simple terms, you want to avoid putting too many parts in a small area. Giving components more space is a good idea. It can lower costs and make production faster. It also helps you avoid expensive mistakes that can cause problems later.

Component Failure and Technician Error

The design stage is the most important part of making a PCB. A small mistake in the design can have big consequences. For example, a designer might choose the wrong type of diode or capacitor for the circuit. This type of component failure can easily lead to a burnt board.

PCB soldering defects can also contribute to component failure. Improper soldering techniques or the use of incorrect materials can create weak connections that may fail under stress or high temperatures. Both lead-free soldering and cold soldering techniques require careful attention to prevent issues such as solder bridges. In-circuit testing can help identify these problems before they lead to board failure.

A board can also burn because it lacks proper protection. Not having the right fuse should be a major concern. The top priority should be adding overcurrent protection for circuit boards. A fuse will blow and cut the circuit if too much current flows through it, preventing electrical overstress. Also, high-voltage protection diodes can save a board from burning during a lightning strike or other power surge.

Other causes are related to human mistakes. This is often called a technician error causing board failure. If a technician connects the board incorrectly, it can burn. Connecting it to the wrong type of power supply will cause a burn out. Also, if the installation instructions are confusing or missing, a technician might connect the board the wrong way.

Next Step: PCB Failure Analysis

Performing a PCB failure analysis is key to improving your product. It helps prevent future defects and addresses potential PCB manufacturing defects. Advanced techniques such as scanning electron microscopy and x-ray inspection can reveal hidden issues like via failures and interconnect defects. Here are some questions we suggest you ask to solve the problem of a burnt component defect:

• Do you need higher-quality parts?
• Do you need a better coating?
• Do you need to improve your component spacing?
• How can you make installation easier for technicians?
• Does the board have protection against too much current?

Higher-Quality Parts

Low-quality parts will likely give you low-quality results. The easiest way to prevent defects is to use good components. This is true now and for the future.

Always have your design reviewed by your board manufacturer before production. They can act as a second pair of eyes. They might find a mistake that you missed.

You can find reliable PCB design services on PCBINQ.COM to help your PCB boards work properly.

Better Coating

A missing or incorrect coating is not a direct cause of a burnt PCB, but it can create problems. This is where conformal coating for PCB protection is important. If dust or dirt gets near a component that is already hot, the particle might catch fire.

There are four common ways to apply a coating: brushing, spraying, dipping, and selective coating. Each method has its own benefits. There are also different coating materials, like acrylic and silicone resin. Make sure you understand what kind of coating and material is best for your PCB to prevent PCB quality issues. Consider factors like corrosion resistance and different surface finishes to enhance the board’s durability.

Better Spacing

An overcrowded board is more likely to burn. It also creates challenges for manufacturing. Sometimes, preventing a defect is as simple as making sure there is enough space on the PCB. Providing better spacing for high-voltage and high-current traces can also lower the risk of a burnt PCB.

Proper spacing is crucial for effective thermal management. It allows for better heat dissipation and reduces thermal stress on components. This is particularly important for high-power or densely packed boards.

Besides spacing, make sure the PCB has proper heat sinks and wide enough traces. Depending on the application, your PCB might need thicker copper layers to handle the current. Always double-check these details. Proper implementation of ground planes and power planes can significantly improve the board’s thermal performance and electrical characteristics.

Clear Instructions for Technicians

The designer and manufacturer know the best way to install a PCB. But the person in the field might not. To avoid failures from technician error, manufacturers can do a few things.

First is clear installation documentation. This manual should explain the correct connection information for each PCB. Another method is more visual. It involves coding the connectors. Manufacturers can use different colors or numbers to clearly mark the PCB connectors. They can also provide a key so the technician knows exactly which wire goes where.

How to solve PCB defects?

PCB defects, like a burnt component, can be a major problem. But working with an electronics contract manufacturer who has experience with PCB assembly can make all the difference. They can help you find the root cause of the issue and build a more reliable product for the future.

Implementing design for reliability principles during the PCB design phase can significantly reduce the likelihood of defects and improve overall product performance. This includes considering factors such as temperature extremes that the board may encounter during its lifecycle. Adhering to IPC standards and following best practices in manufacturing processes can further enhance the quality and reliability of PCBs.

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