Does Reliable Mean Repairable?

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Today, we rely on electronics for many critical applications, from medical devices to aerospace and automotive systems. The safety and reliability of these devices are of utmost importance, which is why good design practices and selecting the right high-reliability electronic components are essential.

Reliability is one of the most critical factors in any electronic system. Engineers often rely on various screening levels for high-reliability electronic components, including AEC-Q, COTS, MIL-PRF, JAN, and more, to ensure reliability. However, one factor is often overlooked but is equally essential in the reliability equation: repairability.

When a component fails, the ability to repair or replace it quickly can be the difference between a minor inconvenience and a catastrophic failure. In most cases, entire boards and sub-assemblies are swapped out, and the old ones are trashed. Choosing panels or sub-assemblies designed to be serviced means that some parts are socketed, connectors are readily accessible and cannot be soldered, and items that may have low life expectancy or fail when stressed—like electrolytic capacitors—are easy to remove and replace.

That's why it's essential to consider repairability when selecting high-reliability electronic components. Some high-reliability parts may be difficult or impossible to repair, requiring complete replacement instead. In contrast, other components may be more easily repaired or replaced, which can be critical for maintaining the system's reliability.

<>In many cases, a high-end modular board processor does not offer user support for board-level repair, and no chip makers support chip repair. User interaction with a board or sub-assembly is limited to firmware updates. In a "disposable" world, little time is spent troubleshooting, and fixing is not part of a product's planned life cycle.

One way to ensure repairability is to select components with a history of being repairable or replaceable. For example, components with standardized interfaces, such as connectors or modular components, are often more easily replaceable than custom-built components. Another way to ensure repairability is to select components from manufacturers supporting repair or replacement. Some manufacturers offer repair or replacement services for their parts, ensuring that even if a part fails, it can be repaired or replaced quickly and easily.

Harsh environments do not lend themselves to field repair. A highly trained astronaut/technician will not repair a board in space (yet). They will swap it out. The same is true for an industrial factory machine. The line downtime is costly. It's challenging to wait two days for a replacement board or module if you can swap out the failed component and return it online in a few hours. If you do stock replacement boards or modules, a quick fix means swapping, not repairing.

However, repairability is just one factor when selecting high-reliability electronic components. Engineers must also consider the criticality of the system, environmental factors, and cost. By carefully weighing these factors, engineers can choose the appropriate components and ensure the reliability and safety of their electronic systems.

Good design practices for your board and system design will make your design more reliable and robust. Here, component selection is key. One important consideration is the criticality of the system. In safety-critical applications like aerospace or medical devices, the consequences of component failure can be severe. In these cases, selecting components that have undergone rigorous testing and screening is essential to ensure maximum reliability. For example, components that meet MIL-PRF screening levels have undergone extensive testing to withstand harsh environments and extreme conditions.

Environmental factors are also critical considerations when selecting high-reliability electronic components. For example, components used in aerospace applications must be able to withstand extreme temperatures, radiation, and other environmental factors. Similarly, components used in automotive systems must withstand the harsh conditions of the engine compartment, including high temperatures and vibration. Reliability standards for aerospace and automotive use dictate most of these required part screenings and design practices.

Cost is also a factor that must be considered when selecting high-reliability electronic components. It is more costly and labor-intensive to use removable screws and washers than it is to pop rivet a board to a chassis. But, it is much easier for a field technician to repair an assembly when it is screwed instead of riveted.

Not all components, or even boards, are repairable. Fine pitch high pin count chips are not easy to remove and replace safely outside a factory. This includes flatpacks and ball grid array packages. Putting these components on removable mezzanine boards is problematic where size is essential. What's more, you introduce more connections when using a mezzanine board, and the higher the number of connections, the lower the reliability.

While selecting the most expensive components may be tempting, this isn't always necessary. Instead, engineers should carefully weigh the component's cost against the system's criticality and the component's expected lifetime. In some cases, selecting a lower-priced part with a shorter expected lifetime may be more cost-effective, mainly if repairability is straightforward.

While repairability is important, it's essential to remember that not all components can or should be repaired. For example, integrated circuits are often sealed, making repair impossible. However, by selecting components with standardized interfaces or from manufacturers who offer repair or replacement services, engineers can ensure that repairability is a key factor in the reliability equation.

Selecting the correct reliability rating for high-reliability electronic components is critical for the success of any application. However, repairability is often overlooked in the reliability of electronic boards and sub-assemblies. By considering reparability and selecting system components that are easily repairable or replaceable, engineers can ensure that their systems are reliable and easily maintainable.