erial drones are rapidly becoming integral to modern society, dominating headlines in combat tactics and finding widespread use across various industries. From 2020 to 2030, the global drone market is anticipated to grow at a compound annual growth rate (CAGR) of 20%, with much of this expansion taking place in the segments of logistic drones, enterprise drones, and defense drones.
Advancements in drone technology accelerate the need to meet strict demands of lightweighting, electronics thermal management, and electromagnetic interference (EMI) shielding to ensure uncompromised signal integrity.
Drones come in nearly every shape, size, and price range. They can be as small as a bumblebee or as large as a small passenger jet, and they can cost anywhere from $10 to hundreds of millions of dollars. Their propulsion systems can be electric motors, gas-powered heat engines, and even jet engines, while propeller types include fixed wing and rotary wing. And, while vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) are not exclusive features of drones, they are common in many types of commercial and defense drones.
Commercial drones are used for non-defense or non-military applications, such as for recreational or industrial purposes. You’ve likely seen drone footage used for the latest Hollywood blockbuster or in a nature documentary or even experienced drone light displays at sporting events or holiday celebrations. Commercial applications have driven a 25% CAGR in drone usage over the last decade.
From an industrial standpoint, drones are used in a variety of applications. Drones offer improved vision and sensors for agriculture and forestry surveying as well as wildlife tracking. Contractors and civil engineering firms are using drones to inspect difficult-to-reach or dangerous locations such as infrastructure and construction sites. Some drone manufacturing companies are marketing their technology for public safety, touting their benefits for fire inspection, police operation, search and rescue, and even crowd control.
And we can’t forget about logistics drones that are used for delivery and fulfillment. Around the world, we’re seeing more and more small-scale trials with delivery drones for packages. Drones also play a vital role in getting critical equipment and supplies like medicine to remote locations that may otherwise be difficult to reach. Drones are playing a major part in our lives, even if they aren’t always visible or obvious. From Washington to Botswana, from Detroit to Japan, from Hollywood to India, drones are being used for all kinds of purposes and making headlines every day.
Many defense drones have a high degree of autonomy as well as interoperability, meaning they need to be able to communicate with other military systems. Commercial drones have varying levels of autonomy and interoperability, and it’s important to note that those requirements tend to be much more application-specific. For example, a light show is one situation where perfectly synchronized drones that operate autonomously and in communication with the base terminal and the surrounding drones would be required.
Longevity and reliability often vary as well. Defense drones are expected to operate with minimal maintenance for years or decades. They must work continuously for hours or days at a time while potentially carrying hundreds or thousands of pounds of payload equipment and flying at lightning-fast speeds.
On the other hand, commercial drones often have relatively light payloads, if any at all, and use lower-power propulsion systems to operate for shorter periods. Most commercial drones don’t have a mission-critical reliability need, except for those utilized for public safety and rescue operations. Recreational drones may need more frequent battery changes and repairs to motors or propellers.
The security and regulatory requirements around each drone type are different as well. Commercial drones are usually only required to meet some U.S. Federal Aviation Administration (FAA) restrictions around flight locations and heights, as well as U.S. Federal Communications Commission (FCC) regulations around wireless communication. The requirements for defense drones are much more strict. Defense drones must meet many military standards, such as MIL‑STD-461 for EMI shielding of electronics, in order to provide resistance against interception, jamming, and cyber threats.
When we refer to the advanced technology within drones, we are not only referring to their propulsion and communication modules but also their advanced sensors. Lidar, radar, laser, and ultrasonic sensors are used for collision avoidance and precision positioning when paired with location control GPS sensors and stabilization or orientation modules. Advanced flight analytics, such as time of flight sensors, can give operators details about how the drone is performing relative to environmental conditions and can be used to enhance future flights.
Additional sensors are needed if the drone is meant to do a specific job, such as videography or imaging. Cameras, chemical detection, thermal sensors, and hyperspectral sensors are just a few examples. It’s important to note that some of this technology can also collect data internally, process the inputs, and respond automatically or communicate in real-time to the operator. Drones do a tremendous amount of data processing, which is the primary reason they need high levels of EMI shielding and thermal management.
An important note is that all devices have different needs for EMI shielding to make sure that nearby electronics are not impacting their performance. The right combination of EMI shielding and thermal interface materials will vary by device and application to provide device-level or component-level protection from unwanted electromagnetic radiation.
The specific particles and binders each lend themselves to different benefits based on the design requirements. For example, fluorosilicones will be used where the gasket may come into contact with harsh chemicals or washdown fluids. A silver-plated aluminum particle will provide very high conductivity, shielding, and galvanic corrosion resistance against aluminum substrates that are exposed to moisture and salt bog.
Conductive elastomers can be extruded into a gasket that sits in a groove or molded into a flat sheet and then die-cut into very intricate shapes, such as those that would be suitable for a connector for grounding. They can provide the advantage of being an EMI shield as well as an environmental seal, cutting down on the number of seals or gaskets required. They can also be developed as co-extruded parts where there is a durable non-conductive gasket permanently bonded to a conductive gasket for an even higher level of galvanic corrosion resistance.
Overall, the advantages of using conductive plastics are weight reduction, RF absorption, corrosion resistance, good shielding effectiveness, and suitability for harsh environments. These plastics are ideal for moderate to high volumes, and while they do provide many benefits, some considerations are the initial cost for the injection molding tooling, upfront design time, minimum wall thickness, fluid exposure, and the color options that are available.
There are many advantages to using these gaskets, and one important one is that they are soft with a very low compression force. Additionally, they are lightweight and low density, typically low cost, and work well as a dust seal. Hundreds of standard parts and profiles are available, and tooling for custom parts is a relatively inexpensive option compared to other solutions. One drawback is that foam-based gaskets are typically not recommended for water or moisture sealing.
The pros of board shields are that they’re low cost and highly customizable with a lot of design options, and they can be integrated into automated assemblies. Additionally, they can be made of several materials and packaged in tape and reel formats, as well as assembled by pick-and-place machines. Aluminum is an increasingly common material for precision board shielding as it has the added benefit of excellent thermal conductivity, serving as a shield and a heat sink. While the upfront tooling cost is a drawback, the low unit cost can certainly make up for that over the course of a high-volume program.
Nearly all gap pads are NASA E595 outgassing certified, meaning they’re approved for use in vacuum, space, and high-altitude applications. Gap pads are traditionally manufactured in sheets and can be cut into any shape or size. While common thicknesses range from 0.25 mm up to about 5.0 mm, gap pads can be made in much larger thicknesses as well. One of the advantages of gap pads is their ease of application, as they can simply be peeled off a protective liner and applied onto a heat sink or electronic component.
While gap pads have a typical minimum thickness of about 0.010” or 0.25 mm, gels can be dispensed in bond lines as thin as about 0.002” or 50 microns and up to well over half an inch on the thicker side. This means significantly increased thermal performance at thinner bond lines as the material can wet out and make effective contact between surfaces. Other benefits include very low compression forces, even lower than those of the already soft gap pads, thus reducing the force on underlying components. They also tend to have a lower density than pads, further reducing weight.
On the EMI shielding side, current research is directed toward new elastomer solutions, such as unique form-and-place materials and RF-absorbing solutions. The industry is not only developing new products but ensuring that these products are augmented with supporting information, such as high-frequency shielding data up to 115 GHz for EMI shielding products and environmental reliability data. Enhanced reliability testing capabilities aim to better align with customer requirements so that products perform reliably and consistently over the entire lifetime of the device.
Finally, remember that there are easy steps to reduce significant weight and ensure reliability in any environment. Lightweighting products such as conductive heat string tubing and plastics can provide up to 75 percent weight reduction while maintaining an important level of EMI shielding and RF absorption. Conductive foams and some thermal gels allow you to take advantage of light weight solutions while providing grounding or excellent heat transfer, respectively. These are all important considerations to keep drones flying safely and reliably.
