Flexible Thinking: Growth of Flex and Flex-hybrid Electronics in Mil-Aero Applications

Over the past several years, flexible electronics (FE) and flex-hybrid electronics (FHE) have enjoyed heightened attention in the electronics industry and have seen special interest and attention given by mil-aero companies. This is evidenced by June’s NextFlex conference titled “Hybrid Electronics Commercialization Path for Aerospace Applications,” an event at Boeing’s Seattle facility. It was well attended by a diverse group of U.S. suppliers of materials, processes, equipment, and products for the aerospace industry as well as several participants from academia.

The reasons for interest are becoming ever clearer as the technology, like its traditional flexible circuit elder siblings, offers advantageous applications in the military and aerospace industries, where lightweight, conformable, and robust electronics are highly desirable.

It is thus worth considering some specific examples of FHE applications in the mil-aero environment.

Wearable Electronics
One application for flex-hybrid circuits is wearable electronics. While the first wearables in the most recent rise of interest in FHE have been for fashion application, such as LED-lighted dresses, the idea of wearable electronics for soldiers caught attention early on and the ground soldier of today is increasingly dependent on electronics to carry out assigned missions.

This particular application is near and dear to me as I was a member of the Land Warrior Development Team at my former company, Pacific Consultants, where, in 2000-01, our small company of engineers and scientists demonstrated the concept of a local area network of soldiers wearing Smart uniforms, each with computers, radios, and heads-up displays to enhance situational awareness of team members. One significant benefit was preventing fratricide (which has unfortunately been the cause of far too many friendly fire casualties in former conflicts) by identifying friendlies on the display. Additional capabilities included gun sight cameras and night vision capabilities. The ultimate objective has always been to improve both the soldier’s performance and safety on the battlefield. More advanced systems will include integrated sensors for monitoring vital signs, hydration levels, and environmental factors. Making the warrior safer and more effective is crucial.

Aboard the Aircraft
Another area of interest is flexible displays and control panels where FHE technologies can be used for aircraft and spacecraft. Advantageously, flexible displays can be integrated into not just flat, but also curved surfaces, providing critical information to pilots or crew members, while saving valuable cockpit space.

Antennas and Sensors
Likewise, conformal antennas and sensors are another area of interest, as FHE technologies facilitate the creation of conformal antennas and sensors that can be seamlessly integrated into the surface of military vehicles, aircraft, and naval vessels. Having conformal antennas can improve aerodynamics and reduce the overall weight of the vehicle while maintaining essential communication and sensing capabilities.

Drones and unmanned aerial vehicles (UAVs), as well as unmanned autonomous ground vehicles, are beneficiaries of FHE. They make the UAVs lighter in weight, more efficient, and more mission capable. Flexible electronics enable unique design possibilities, leading to more advanced and more stealthy UAVs for reconnaissance, surveillance, and other military applications. The ongoing conflict in Ukraine has, for better or worse, become a proving ground of these increasingly important war-fighting technologies.

Flex-hybrid electronics, again like their traditional flexible circuit kin, are well suited to ruggedizing electronic systems in military and aerospace environments. It is well known that electronic components in mil-aero applications must withstand harsh conditions, including shock, vibration, and extreme temperatures. Flexibility is a key feature in mitigating such conditions.

Health Monitoring
Health monitoring is not just for the human soldier, it is also a concern for aircraft of every sort. Thus, interest in “smart skins” and aircraft structural health monitoring is being targeted for and enabled by FHE where flexible sensors both monitor and detect damage, fatigue, or stress in real-time, enhancing maintenance and safety. In recent years, prognostics has become an increased area of interest in both mil-aero and consumer environments; FHE tools will undoubtedly see increased use.

Electronic Warfare
With the ever-increasing reliance of electronics by militaries around the world, electronic warfare (EW) systems are, unsurprisingly, also of ever-increasing interest. Flex and flex-hybrid electronic technologies can foreseeably be used in EW systems for intelligence monitoring and gathering as well as for other electronic countermeasure applications. Again, the conformal nature of the products enables their near seamless integration into various EW platforms.

Closely coupled with electronic warfare is, unsurprisingly, cybersecurity. Once again, flexible circuit technologies can offer enhanced security in military communications and data transmission. Sealed flexible circuit designs include built-in EMI and ESD shielding to make it difficult to physically tamper with the circuitry while at the same time providing an additional layer of protection against wireless electrical and electronic threats.

Satellites and Space
Last but certainly not least are satellite and space applications for flex and flex-hybrid electronics. The technologies have long been employed in such products to create flexible solar panels, lightweight antennas, and various electronic sensors of many varieties. Flex and FHE designs enable more efficient use of space while reducing weight, both long considered critical factors in the aerospace industry.

This is not an exhaustive recitation of where and how flex-hybrid electronics are helping to advance military and aerospace industries, but it is reasonably representative. As familiarity with flexible circuit and flex-hybrid electronics technologies continue to advance, there will unquestionably be more innovative applications coming into existence, providing ever greater efficiency, reliability, and versatility to the products.

Joe Fjelstad is founder and CEO of Verdant Electronics and an international authority and innovator in the field of electronic interconnection and packaging technologies with more than 185 patents issued or pending. To read past columns or contact Fjelstad, click here. Download your free copy of Fjelstad’s book Flexible Circuit Technology, 4th Edition, and watch his in-depth workshop series “Flexible Circuit Technology.”



Flexible Thinking: Growth of Flex and Flex-hybrid Electronics in Mil-Aero Applications


Over the past several years, flexible electronics (FE) and flex-hybrid electronics (FHE) have enjoyed heightened attention in the electronics industry and have seen special interest and attention given by mil-aero companies. This is evidenced by June’s NextFlex conference titled “Hybrid Electronics Commercialization Path for Aerospace Applications,” an event at Boeing’s Seattle facility. It is thus worth considering some specific examples of FHE applications in the mil-aero environment.

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Flexible Thinking: Stretching Conductors—and Design Possibilities


Stretchable circuits, also referred to as elastic circuits or even “elastronics,” are a subset of the venerable flexible circuits that have enabled countless numbers of today’s electronics products, from toys to smartphones to the International Space Station. This most recent “member” of the interconnection family—stretchable circuits—have been designed and engineered to be resiliently bent, twisted, and/or stretched in support of the end product’s need without negatively affecting its electrical function.

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Flexible Thinking: The Adjacent Possible


In the inspirational and informative book titled "Where Good Ideas Come From," author Steven Johnson uses the term "the adjacent possible." This term, which immediately captivated my mind, originated with a theoretical biologist named Stuart Kaufman, who used the term in his book, Investigations, to describe the circuitous path of biological evolution. For Johnson, however, the “adjacent possible,” which is one of the places “good ideas come from,” conceptually includes everything that’s one step away from what currently exists, with more is yet to come. This is important. There is a necessary precondition that there must be an immediate nexus to make something “adjacently possible.”

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Flexible Thinking: Catalyzing Change and Design Evolution


Electronics have wormed their way into our daily lives in ways few of us could have ever imagined. In their early days especially post-World War II through the 1950s, electronics were largely used to entertain us, first with radio and then with television. Those two drivers have clearly not gone away; if anything, they have become even more woven into our lives by internet and smartphone technologies where sound and images demand our attention nearly every waking moment.

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Flexible Thinking: Tribal Knowledge—A Personal Perspective


With the benefit of more than half a century of experience in the printed circuit and electronics interconnection industry, I now enjoy a perspective that is not available to those just entering into the industry. I harken often to a comment I chanced upon a few decades back made by legendary Swedish film director, Ingmar Bergman, who expressed in an interview, “Old age (growing old) is like climbing a mountain. You climb from ledge to ledge. The higher you get, the more tired and breathless you become, but your views become more extensive.” That perspective is truly a gift, regardless of what one does in life. It certainly has resonated with me (even before I arrived here.)

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Flexible Thinking: A Once and Future Idea


Electronic assemblies are typically comprised of a mix of discrete resistors, capacitors, inductors, and the like, along with numerous integrated circuit chips, each chip having a certain function or range of different functions. In such assemblies, there are also several different connectors and/or sockets that allow for the assembly to be connected to other assemblies. Making interconnections between and among these many and various active and passive devices is the job of the circuit designer. To date, a broad range of IC packaging and electrical interconnection techniques have been used in such assemblies, especially at the higher end.

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Flexible Thinking: A Patently Innovative Resolution


The month of January is named for the Roman god Janus, a two-faced deity whose role is to watch over doorways, the comings and goings of individuals, and the passage of time. In January, individuals often make resolutions to themselves; though following through on these resolutions may be short-lived, a new year often prompts people to be mindful of the need to make some improvements in their lives—whether personal or professional. One of the best ways to look forward is, like Janus, to simultaneously look backward. For technologists of every stripe, one of the best places to look back on is the U.S. Patent and Trademark Office (USPTO).

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Flexible Thinking: Flexible Circuits—A Road Less Traveled


Referencing a famous poem may seem an odd way to start a technology column, but I find it fitting; my long engagement with flexible circuit technology has taken me places, both mentally and physically, that I would never have seen or experienced had I not developed an interest in what was once a marginal interconnection technology. Flexible circuits were a road less traveled when I first encountered them but taking that path has made all the difference in my career.

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Flexible Thinking: The Chameleon of Interconnection Technologies


Flexible circuits are arguably the first instantiation of electronic interconnections. A flexible interconnection structure was first disclosed in patent literature by Albert Hansen—unearthed by gifted researcher, innovator, and self-described technology generalist Dr. Ken Gilleo. The roots of flexible circuits, as determined by the patent Gilleo uncovered, date back to a 1903 British patent issued to Albert Hansen of Germany, entitled “Improvements in, or Connected with, Electric Cables and the Joining of Same.” The invention was designed to serve the new world of telephony and improve interconnection design.

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Flexible Thinking: The Rapidly Expanding Realm of Stretchable Circuits


Flexible circuit technology has been rising ever higher on the radar of those charged with designing next generation electronic products for every imaginable application, from the mundane to the highly exotic. The technology is being embraced by a growing fanbase as they become increasingly aware of flex circuit technology’s numerous benefits. They are being driven to new heights by industry and government collaborations such as NextFlex and FlexTech, and their laser-like focus on what was formerly called printed polymer thick film circuits, now rebranded as flex hybrid electronics (FHE) and printed electronics.

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Flexible Thinking: The Many Benefits of Eliminating (Most) Solder


Many scientists are familiar with the concept of Occam’s Razor (also sometimes called the Law of Parsimony). The basic idea postulates that when attempting to explain any given observed phenomena, the simplest explanation is preferable to those which are more complex. The reasoning behind the concept is that simple theories are easier to examine and verify, and not coincidently, are more often found to be true. Simplicity is a theme that has been recommended time and again by some of the greatest minds in history.

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Flexible Thinking: Blue Skying It With Aluminum Rigid-Flex


Aluminum is an amazingly versatile metal and has found its way into countless products since its discovery during the reign of Napoleon III of France. At the time, it was more valuable than gold, and at hosted dinners, the emperor and his honored guests dined using aluminum cutlery while the others had to make do with gold utensils. It took some time for scientists to calculate that it was by far the most abundant metal found in the earth’s crust at 8.3%, ranking third among all elements found in the crust, ranking behind oxygen (46%) and silicon (26%).

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Flexible Thinking: The Fascinating History of Wearable Electronics


Wearable electronics have been capturing much attention in the press, both technical and business, over the past few years. Articles for consumption by the public, as well as technical research papers on the topic, have been increasing steadily in recent times. However, wearable electronics are far from new. Moreover, the term “wearable” is quite fungible and encompasses a broad spectrum of prospective embodiments.

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Flexible Thinking: Flexible Circuits or Flexible Electronics?


The term “flexible circuit” has been ensconced and accepted in electronic interconnection technology lexicon for several decades. In broad brush strokes the term has embraced every type of printed circuit produced on flexible base materials, regardless of the nature of the conductors used; metals, such as copper; or conductive inks, such as silver or other conductive particle filled polymers. The latter type of truly printed circuits, have, for many years, been referred to as “polymer thick film” circuits.

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Flexible Thinking: Shaping Flexible Circuits


It is axiomatic that bending and folding are fundamental to flexible circuits. Reality is that most flex circuit applications are ones where the circuit is made to conform to the confines of the package that contains it to meet product design objectives. This is a matter that is often glossed over but it is often very important to get the flex circuit to take on a reasonably permanent shape to facilitate its installation into a housing.

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Flexible Thinking: A Brief Retrospective of 50 Years in the PCB Industry


I recently reflected upon the notion that this year marks my 50th year in the printed circuit industry. It was a bit of a shock when I looked at the calendar and realized that I have been kicking around this industry for a half-century. I was fortunate enough to find my way into the PCB industry through the analytical lab of a PCB company in Mountain View, California in the early days of Silicon Valley. The name of the company was Printex and it was one of the premier PCB fabricators in the United States.

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Flexible Thinking: Flexible Circuits—A Catalyst for Technological Evolution


With only a wee bit of prejudice, I would argue that flexible circuits are among the most adaptive and adaptable of all electronic interconnection technologies and perhaps the most catalytic as well. The driver of change has been that the industry is continuously being pressed to develop newer and better products with more functions and at lower cost. There is likely a tendency to think that change is the result of consumer demand, but as Steve Jobs observed many years ago, the consumer doesn't necessarily always know what they want until they see it and can sense or experience the value.

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Flexible Thinking: Intellectual Property—How it Works for the Benefit of All


Innovation is the lifeblood of technological progress. It has been the driving force in electronics for over a century. In general, intellectual property (IP) refers to innovations, those creations of the human mind. Patents protect those creations. Joe Fjelstad explains.

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Flexible Thinking: The Importance of Asking 'Why Not?' When Inventing


With such an impressive list of benefits, it seems it might seem as though flexible circuit technology has reached its improvement limits. However, the principle of continuous improvement does not rest and it demands that we persist in our efforts do and make things better over time.

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Flexible Thinking: The Calf Path—Redux


When I first read the poem many decades ago, it immediately struck me with its simple yet profound wisdom. Since that fortunate discovery, the poem has informed often my conscious thinking. I'm sure it will for you as well.

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Flexible Thinking: Star Trek Memories


Columnist Joe Fjelstad not only watched Star Trek with fascination, he grew to become his own inventor, thanks to his father—an aerospace engineer. "The passion for flight, especially rocketry, entered my veins early," he writes.

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Flexible Thinking: Process Flow for Occam QFN Test Vehicle


Joe Fjelstad teaches the Occam process through a series of steps and images. These solutions can significantly reduce the number of process steps required to manufacture an electronic module or assembly (perhaps by as much as one-third) and in the process making electronic assemblies more reliable and less costly by fundamentally focusing on the elimination of solder and the soldering process.

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Flexible Thinking: IC Package Footprints—Why So Many and How Many Is Enough?


Joe Fjelstad takes a historical look at the formation of integrated circuits and what that means for today's PCB designs.

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Flexible Thinking: Flexible Circuits Vs. Flexible Hybrid Electronics—Where’s the Line?


The line separating polymer thick film flexible circuit assemblies from flexible hybrid electronics, exists but it is not hard and bright. The introduction of new flexible circuit manufacturing technologies and materials including stretchable substrates has created a surge of interest in their use.

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Flexible Thinking: Thermal Management—Electronic Technology’s Rodney Dangerfield


Thermal engineering has, unfortunately, often been treated with less respect than it deserved. Dealing with the heat generated by electronics was often not given full consideration until after the design was completed and prototyped, and the problem manifests as a failure. Joe Fjelstad emphasizes why keeping devices cool is a vital objective.

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Flexible Thinking: Designers at the Edge


Designers often play it safe in the center, but step out on the edge and you’ll likely see things much differently. Joe Fjelstad shares his thoughts.

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Flexible Thinking: Lead-Free Solder—Panacea or Pandemic?


Solder has been used as the primary means of interconnecting electronic components for more than seven decades. For the benefit of all those who are new to the electronics interconnection industry, Joe Fjelstad shares how we got to this point.

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Flexible Thinking: When Expectations and Results Don’t Line Up


Around 20 years ago, I had the good fortune of receiving a recommendation to read the book The Four Agreements by Don Miguel Ruiz and subsequently picking it up. It is a short and simple book that the author says is based on ancient Toltec wisdom.

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Flexible Thinking: DFM or Design With Manufacturing?


The great Irish author, playwright, and humorist Oscar Wilde once defined a cynic as an individual who knows the price of everything and the value of almost nothing. Unfortunately, over the decades, that same analysis could often be applied to procurement agents in electronic product companies around the globe. The reward for a purchasing agent is too often derived not from getting the best solution for their company but the best price

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Flexible Thinking: Profitability—A Vital Design Requirement


The decisions designers make will impact virtually every manufacturing step in the fabrication and assembly of electronics products. Joe Fjelstad explains how applying “design for” guidelines can help create products that can be made both reliably and profitably when applied.

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Flexible Thinking: Power and Thermal Management—Dealing With the Heat


Without power, electronics are useless. With power, miracles happen. Managing that power is critical in both design and operation in terms of heat generation and energy conservation, especially for battery-powered devices. Moreover, often in electronic products, designers find themselves providing power to an electronic module or system at multiple different voltages and currents.

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Flexible Thinking: Looking Back and Looking Forward


The month of January is upon us once again. The month is named after the Roman god Janus. According to Wikipedia, Janus is the god of beginnings, gates, transitions, time, duality, doorways, passages, and endings. He is usually depicted as having two faces: one on the front of his head, and one on the back since he looks to the past and future.

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Flexible Thinking: The Value of Experience


For many people, December is a month in which to reflect on the experiences and lessons encountered and learned over the past year. As the years pass, I am increasingly thankful for the many experiences that have brought me to this point. In sitting down to collect and share my thoughts, what first came to mind was a timeless story about the value of experience. It goes something like this.

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Flexible Thinking: Additive Manufacturing of PCBs


We are seeing increasing interest in technologies that will allow one to make electronic substrates in near real-time using additive processing techniques and 3D printers. It is a true game-changer in product development. The surge in interest in additive manufacturing technologies shown in recent times—as indicated by the significant increase in published articles and press releases—suggests that the electronic interconnection manufacturing industry could be on the verge of a manufacturing renaissance.

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Flexible Thinking: Standards—An Industrial-strength Glue


Standards are frequently viewed as cumbersome nuisances and impediments to progress by those pressing for rapid change. The process of writing, getting approval, and promulgating standards can be arduous and frustrating. It has a lot of similarities to the creation and passage of laws in various government bodies in that there are many opinions and interested parties who engage in the process to make sure that it results in a product that does not damage or favor one solution or party over another.

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Flexible Thinking: Making Flexible Circuits Stretchable


It is my opinion that the initial driving impetus for the development of stretchable circuits was a bit different than normal, meaning that military and aerospace have traditionally driven the development of arcane electronic interconnection technologies as they did with the development of both flexible and rigid-flex circuits. In contrast, it was a consumer-driven market that appears to have been the gate opener in the form of wearable electronics.

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Flexible Thinking: How to Get From Here to There


To begin any process, you must first know where you are going. This is true for any project or life pursuit, I believe, and I often try to bring it to mind as I start any new project. With respect to developing products that might benefit from flexible circuit technology, this is no less true. Find out why.

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Flexible Thinking: Ways to Conserve Flex Circuit Material in the Design Process


In summary, the decisions made by the flex circuit designer when laying out a flex circuit will have an impact that lasts the entire process. By considering how the circuit might fit onto a panel before submitting the design to a manufacturer, it may be possible to save a considerable amount of material and money.

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Flexible Thinking: A Few Simple Lessons in Designing Reliable 3D Flex


There is an old and familiar adage that goes something like this: “If the only tool in your tool chest is a hammer, you tend to see every problem as a nail.” We all have a tendency to stick close to the familiar and use the tools we know to create solutions to problems confronting us; we’re only human.

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Flexible Thinking: A Few Simple Lessons in Designing Reliable 3D Flex


We all have a tendency to stick close to the familiar and use the tools we know to create solutions to problems confronting us; we're only human. Unfortunately, using only familiar tools limits our ability to come up with optimal or even superior solutions. This article will help you avoid some of the traps conventional wisdom doesn't always give guidance on.

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