What Goes Into Rugged Electronics Design?

| Created: June 15, 2021

Try searching for “rugged electronics” on the internet, and you’ll probably find a lot of videos showing people stepping on their smartphones. Rugged electronics need to take a punch mechanically, but there is more that goes into a rugged system than being able to survive a drop on the pavement. This is as much about enclosure design as it is about component selection and manufacturing choices.

Mil-aero designers often use the term “harsh environment” to describe a number of scenarios where an electronic device’s reliability and lifetime will be put to the test. If you want to make your next product truly rugged, it helps to adopt some of their strategies in your PCB layout. In this article, we’ll look at some of the design strategies used in mil-aero designs, as well as strategies used for industrial designs.

What Qualifies as a Harsh Environment in Rugged Electronics?

The term “environment” as defined in some industry standards can refer to anything from actual environmental conditions (temperature, humidity, etc.) to the mechanical environment (e.g., vibration) or electrical environment (noise, potential for ESD). Rugged electronics are typically designed to withstand one or more conditions typically found in harsh environments:

Excessively high or low temperatures
Extreme and frequent temperature cycling
Moisture and high/low pressure
Mechanical vibration or shock
Electrical discharge at high voltage/current
Particulates, such as dust
Oxidizing or explosive gases

This is a pretty extensive and mind-boggling list. Generally, you can’t design a single device to withstand every factor in the above list. Harsh environments are difficult to deal with simply because there is such a broad range of factors that can destroy an electronic device. These problems could affect the board, components, the overall PCBA, or all of the above.

Some Ruggedization Strategies

The table below summarizes some of the solutions you can implement in your design to make it more rugged and better withstand the above list of environmental factors.

Environmental Factors	Design Strategies
High temperatures	Combination of conduction cooling (chassis/heat sink), use thermal interface materials and fans, spread out hot components, use ceramics or metal-core PCBs, liquid cooling
Low temperatures	Use ingress protection to prevent condensation, apply DC heating to bring components within normal operating temperature range
Extreme thermal cycling	Use high Tg laminates, don’t use stacked vias.
High pressure environments	Plan to also design for extreme temperatures, select appropriate components that will not implode, use conformal coating and fill the enclosure with an inert gas or insulating liquid
Mechanical vibration or shock	Opt for through-hole components where possible, design the board so its lowest order resonant vibration frequency is at least triple the expected shock frequency, solder large ICs directly to the board instead of using sockets or grid arrays
Electrical discharge	Keep earth ground close to your chassis and TVS grounds, use ESD protection circuits
Particulates	Use conformal coatings to prevent ESD, use a high pressure sealed enclosure to keep out particulates
Corrosion from moisture or oxidizing gases	Use conformal coatings with the appropriate chemistry, design a sealed enclosure with high pressure rating
Explosive gases	Eliminate any component that could create an intended spark during operation (e.g., relays), apply ESD protection measures

From the above table, it should be clear that ruggedization spans beyond the board level. Some solutions can only be implemented at the board level, while others require considering everything from board to components and the enclosure. Some of the industry standards that govern these solutions include:

Ingress Protection (IP) standard, which limits moisture ingress in rugged electronics
MIL-S-901D, specifying high-impact mechanical shock requirements for equipment on ships
MIL-STD-810G, specifying testing requirements for military equipment that has been commercially adopted
National Electrical Manufacturers Association (NEMA), specifying enclosures, cabinets and housings
National Fire Protection Association (NFPA), specifying a range of requirements on electronics in certain environments to ensure fire suppression or containment
Potentially Explosive Atmospheres (ATEX), NFPA 497, and HazLoc, specifying design requirements to prevent explosion when a device is deployed in an environment containing explosive gases

Your Enclosure and Mounting Style Matter

So far, we’ve only discussed the electrical design, the physical layout, and the PCBA. Obviously, designing rugged electronics requires more than just putting a thicker plastic case around the PCB and calling it a day. The enclosure, board mounting style, and fixtures will play a major role in determining reliability and in combating some of the environmental factors listed earlier.

One simple way to address mechanical shock and vibration alongside potential electrical/thermal factors is to use a shock-mounting with a vibration damper. The damper shown below is hobby-grade, but it has a very similar structure to the mounts used in quadcopter drones.

Rugged electronics vibration damping — *Example vibration damping mount. This type of multi-platform mount is often used on drone copters.*

Other aspects of enclosure design and mounting will need to consider the specific environmental factor you need to address. Accommodating an environment with a high pressure gas will not use the same strategy that is used in a high pressure liquid environment, even though both of these are enclosure-level solutions that rely on pressure equalization. Rugged electronics design is a great example where the electrical design team needs to closely communicate with the mechanical team to ensure the ruggedization strategy does not interfere with electrical requirements.

Final Thoughts on Rugged Electronics

The last piece of advice I can give around rugged electronics is that you won’t won’t always be deploying a device in a scenario that comprises the entire list of harsh environments. Therefore, the first step in designing rugged electronics is to consider the specific environmental factors that could damage the product and focus on these in your design. For example, don’t worry about designing protection from oxidizing gases if your chief worry is temperature cycling (although you might get this protection as a side benefit). Focus on what matters for your design and you can still produce something that is compact and cost-effective.

With the best PCB design tools in Altium Designer®, you can design high-quality rugged electronics, including your enclosure and fabrication data. For enclosure design, you can use the MCAD CoDesigner extension to easily import your board into Autodesk Inventor, Solidworks, or PTC Creo. When you’ve finished your design, and you want to release files to your manufacturer, the Altium 365™ platform makes it easy to collaborate and share your projects.

We have only scratched the surface of what’s possible with Altium Designer on Altium 365. Start your free trial of Altium Designer + Altium 365 today.

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About Author

Zachariah Peterson has an extensive technical background in academia and industry. He currently provides research, design, and marketing services to companies in the electronics industry. Prior to working in the PCB industry, he taught at Portland State University and conducted research on random laser theory, materials, and stability. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensors, and stochastics. His work has been published in over a dozen peer-reviewed journals and conference proceedings, and he has written 2500+ technical articles on PCB design for a number of companies. He is a member of IEEE Photonics Society, IEEE Electronics Packaging Society, American Physical Society, and the Printed Circuit Engineering Association (PCEA). He previously served as a voting member on the INCITS Quantum Computing Technical Advisory Committee working on technical standards for quantum electronics, and he currently serves on the IEEE P3186 Working Group focused on Port Interface Representing Photonic Signals Using SPICE-class Circuit Simulators.