Printed circuit boards, or PCBs, are essentially the lifeblood of the devices we use every day. Cellphones, TVs, cars, street lights and so many other devices rely on PCBs, which is why it can be extremely disruptive when one fails.
PCBs fail for a litany of reasons, sometimes even before they’ve been shipped for use. By understanding the causes of PCB failure, it’s easier to prevent future failures and enjoy more productive PCB testing.
6 Causes of PCB Failures
Here are the most common causes of PCB failures:
- Burnt components (a type of defect)
- Environmental factors like heat and humidity
- Soldering issues
- Human error
- Old age
Here are the underlying factors for each:
Defects are the most prevalent cause of PCB failure. Often occurring during the PCB assembly process, several things can cause a board defect.
PCBs are extremely sensitive to electrostatic discharge (ESD), and though we can only feel ESD in the thousands of volts, the smallest discharge can cause a component defect. This can be latent (meaning the PCB remains functional but suffers downgraded reliability) or catastrophic (meaning permanent damage has been done.)
Other potential defects include:
- Misaligned layers
- Short circuits
- Crossed signals
Reliable PCB manufacturers take several precautions to eliminate electrostatic discharge on the production floor. This includes ESD-safe smocks, shoe grounders, and dissipative floor and work surfaces.
2. Burnt Components
A type of defect, burnt components are a common occurrence because PCBs are subject to high temperatures. The probability of a burnt component increases exponentially if there’s insufficient space surrounding it, but size and shape also factor in how much heat a component can withstand before burning up.
3. Environmental Factors
Circuit boards are sensitive to outside factors as well. Heat and humidity can cause expansion in PCBs, resulting in warping and potentially damaged soldered joints. This is why PCB manufacturing is usually done in a climate-controlled environment where humidity is kept at a safe level.
Foreign debris that comes into contact with a board can have adverse effects as well. Plenty of things can find their way into your assembly and cause overheating, such as:
- Hair (yuck)
4. Soldering Issues
Solder is a key ingredient in the PCB process. It’s what maintains the contact between a component and circuit, but it can occasionally become contaminated and result in a board failure.
If there is too much moisture in the solder, it can become conductive and cause short circuiting.
5. Human Error
Design engineers, assemblers, quality engineers, and seemingly countless others are involved in the production cycle. So it’s not a surprise that human error plays a part in more than a few PCB failures. There is shortage of honest (or lazy) mistakes that can harm a PCB, including:
- Misreading a schematic
- Incorrectly installing components
- Placing traces too close together, resulting in a short
- Poor soldering
The good news? Most of these errors can be fixed with rework, but it can cost you both time and money.
PCBs tend to age more like humans than fine wine. As they get older, they begin to break down.
Components begin to fail after reaching the end of their expected life cycle, and the PCB must be fixed or replaced with a new one. Often, a board can be fixed for a fraction of the price of a new PCB, making contract manufacturers that offer aftermarket services a valuable asset to have on hand.