Why Components Fail and How to Identify Them

Component failure modes offer a predictable approach to maintenance

Technician constructing electric component part

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Parts fail and things break. It's a fact of engineering as well as life. Some component failures can be avoided by good design practices, but many are simply out of your hands. Identifying the offending component and why it might have failed is the first step in refining the design and increasing the reliability of a system that experiences repeated component failures.

Technician constructing electric component part
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Causes of Component Failure

There are numerous reasons why components fail. Some failures are slow and graceful, offering time to identify the component and replace it before it fails completely. Other failures are rapid, violent, and unexpected.

Some of the most common reasons for components to fail include:

  • Aging
  • Bad circuit design
  • Cascading failure
  • Change in the operating environment
  • Connected incorrectly
  • Connection failures
  • Contamination
  • Corrosion
  • Electrical stress
  • Electrostatic discharge
  • Manufacturing defect
  • Mechanical shock
  • Mechanical stress
  • Overcurrent
  • Over-temperature
  • Overvoltage
  • Oxidation
  • Packaging defects
  • Radiation
  • Thermal stress

Component failures usually follow a trend. In the early life of an electronic system, component failures are more common and the chance of failure drops as they are used. The reason for the drop in failure rates is that the components that have packaging, soldering, and manufacturing defects often fail within minutes or hours of first using the device. This is why many manufacturers include a several hour burn-in period for their products. This simple test eliminates the risk of a bad component slipping through the manufacturing process, resulting in a broken device within hours of a purchase.

After the initial burn-in period, component failures typically bottom out and happen randomly. As components age, natural chemical reactions reduce the quality of the packaging, wires, and the component. Mechanical and thermal cycling also take their toll on the strength of the component. These factors cause failure rates to increase as a product ages. This is why failures are often classified by either their root cause or by when they failed in the life of the component.

You can reduce the risk of catastrophic error with routine inspection of parts known to fail after a certain amount of time or usage. For example, in the aviation industry, core components get replaced when they've functioned for a specific number of hours, regardless of whether the component shows signs of stress or degradation.

How to Identify a Failed Component

When a component fails there are a few indicators that can help identify the component that failed and aid in troubleshooting the electronics.

  1. Visually inspect the component for damage. The most obvious indicator that a specific component has failed is through a visual inspection. Failed components often have burnt or melted areas, or they have bulged and expanded. Capacitors are often found bulged out, especially electrolytic capacitors around their metal tops. Integrated circuit (IC) packages often have a small hole burned in them where a hot spot on the component vaporized the plastic all the way through the IC package.

  2. Check for smoke or smells. When components fail, a thermal overload often occurs, causing the magic blue smoke and other colorful smoke to be released by the offending component. The smoke also has a very distinct smell and varies by the type of component. This is often the first sign of a component failure beyond the device not working. Often the distinct smell of a failed component will stay around the component for days or weeks, which can aid in identifying the offending component during troubleshooting.

  3. Listen for failure sounds. Sometimes components make a sound when they fail. This happens more often with rapid thermal failures, over-voltages, and over-current events. When a component fails this violently, a smell often accompanies the failure. Hearing a component fail is rarer, and it often means that pieces of the component will be found loose in the product, so identifying the component that failed may come down to finding which component is no longer on the PCB or in the system.

  4. Test individual components. Sometimes the only way to identify a component that has failed is to test it. This process can be very challenging on a PCB because often other components influence the measurement. Because all measurements involve applying a small voltage or current, the circuit will respond to it and readings may be thrown off. If a system uses several subassemblies, replacing them is often a great way to narrow down on where the issue with the system is located.