When you’re designing for space, defense, or high-reliability aviation systems, the standards are different. Every component must function not just well—but flawlessly—under pressure, extreme temperatures, vibration, and long mission durations. And yet, even in these high-stakes applications, some parts get overlooked in the design phase.
Relays are often one of them.
It’s easy to think of relays as simple switches. But in military and aerospace environments, selecting the wrong relay can jeopardize the entire system. So, what actually makes a relay aerospace-ready? And how can design engineers spot the difference between a general-purpose part and one engineered for mission-critical performance?
Let’s take a closer look.
What Makes a Relay Aerospace-Grade?
For a relay to be viable in aerospace or defense systems, it must meet strict performance, environmental, and reliability standards that go far beyond typical commercial specs. Here are the key attributes to look for:
MIL-Spec Compliance
MIL-PRF-83536 is a common performance specification for electromechanical relays used in defense and aerospace. Compliance means the relay has passed extensive qualification testing for contact reliability, temperature range, vibration resistance, shock, dielectric strength, and more.
Hermetic Sealing
Relays exposed to wide temperature swings or corrosive environments must be sealed to prevent internal degradation. Hermetically sealed relays ensure performance stability over time, particularly in space and high-altitude applications where atmospheric pressure is low or non-existent.
Wide Temperature Operation
Commercial-grade components may handle –40°C to 85°C. Aerospace relays? Often rated for –70°C to +125°C or more. Performance must remain consistent regardless of thermal cycling or sudden temperature changes.
Vibration and Shock Tolerance
Relays in aerospace systems must survive intense launch conditions or combat environments. Vibration tolerance up to 30G and mechanical shock ratings around 200G are common targets for aerospace-qualified parts.
Long-Term Supply Stability
Aerospace programs can last decades—from design to deployment and beyond. Engineers need assurance that the parts they specify today will be available (or at least supported) long into the future.
Case in Point: Microchip’s BR235 and BR235D Power Relays
Microchip recently introduced its BR235 and BR235D series of 25A electromechanical relays as part of its aerospace and defense component portfolio. These devices serve as a good example of what engineers should look for when specifying relays for mission-critical systems.
Here’s how they align with the criteria mentioned above:
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MIL-PRF-83536 qualified and ISO-9001 certified
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Hermetically sealed to maintain long-term reliability
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Designed to operate from –70°C to +125°C
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Withstand 30G vibration and 200G shock
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Offered in multiple configurations to fit different mechanical and electrical design needs (e.g., suppressed/non-suppressed, 6–48 VDC or 115 VAC coils, tin or gold contacts, J-hook or straight terminals)
This level of design flexibility is critical for engineers integrating relays into tightly constrained or pre-existing architectures.
Just as important: Microchip backs these components with a long-term supply commitment, addressing a common concern when other suppliers deprioritize lower-volume or high-rel materials over time.
Why It Matters
The role of a relay may seem minor in the broader scope of a satellite payload or a flight-control subsystem. But reliability failures—even at the relay level—can lead to costly redesigns, system downtime, or in worst-case scenarios, mission failure.
And while design engineers are no strangers to MIL-SPEC datasheets, it’s not just about ticking boxes. Understanding how and why certain specs matter in real-world environments helps teams make smarter, longer-lasting design choices.
So whether you’re building a defense radar system, a high-altitude drone, or a spacecraft subsystem, remember: not all relays are created equal—and not all suppliers treat aerospace reliability as a priority.
Conclusion
When selecting relays for aerospace and defense applications, performance specs matter—but so does supply assurance, flexibility, and the support of a partner that understands your environment. Tools like Microchip’s BR235 series offer a blueprint for what to look for: not just performance under pressure, but confidence over time.
