Flexible Thinking

Column from: Joe Fjelstad

Joe Fjelstad, a founder of Silicon Pipe Inc., is an international authority and innovator in the field of electronic interconnection and packaging technologies with more than 185 U.S. patents issued or pending. He is the author of Flexible Circuit Technology and author, co-author or editor of several other books including Chip Scale Packaging for Modern Electronics. He has also authored numerous technical papers and articles. He frequently presents seminars on PCB, flex circuit and chip scale packaging technologies at industry conferences. You may contact him at 408-973-1744, x203.

March 13, 2024

Flexible Thinking: PCB Designers Still Wanted

From their relatively simple beginnings, PCBs were largely structured using through-components, including axial leaded resistors, capacitors and diodes, and the iconic dual inline bug-like IC packages. They were often assembled using breadboard and wire-wrapped connections that enabled the electronics hobbyists to prototype their imaginative circuit designs. Current generation PCBs rival their integrated circuit siblings in complexity as they have become even more closely associated with creating today’s mind-numbing products.
February 28, 2024

Flexible Thinking: Embedded Design—A Term With Multiple Meanings

With the seemingly endless ways that electronic products are worming their way into our lives, what was once “nice to own” is increasingly considered indispensable. The capabilities of these products have been driven by relentless improvements at every level of the manufacturing chain, from individual transistors (which are approaching Angstrom levels) to systems the size of buildings supporting Bitcoin mining and increasingly distributed AI products.
January 24, 2024

Flexible Thinking: What Matters When Designing Next-generation Products?

Since at least the 1970s, there has been a somewhat fungible mantra in electronics product development that has included two or more of the following descriptive adjectives: smaller, faster, lighter, better, and cheaper (often coupled with more rugged and reliable). Getting all of them simultaneously was not always possible, but if you paid enough, you could probably achieve it. However, it generally required the purchaser to give in to some commonly held “rules of the road” set down by the manufacturing community. When navigating the design process, what happens when the manufacturers want you to follow a road that does not take you where you want to go, or when standard practices are too constraining?
November 08, 2023

Flexible Thinking: The Simplest Way Is the Best Way

Interconnection substrate technologies (PCBs, flex and rigid-flex circuits, and IC packaging substrates) have made possible the steady advance of electronic products for more than seven decades. As foundational structures for electronics, they are arguably the backbone of modern electronics. However, their design and manufacture has gotten increasingly challenging over the years.
September 26, 2023

Flexible Thinking: Unlocking the Key to Rigid-flex Design Success

Despite what some seem to believe, rigid-flex circuits are not a new technology. In fact, they are more than a half-century old. At the time of the invention, my friend Thomas Sterns was working at Sanders Associates, the pioneering flex circuit manufacturer. Like many products in the first decades of printed circuit technology, they were working on a military application. The objective was to provide a reliable method for reducing the size, bulk, weight, and questionable reliability of wire harness assemblies while simultaneously reducing cost and assuring that human error might be minimized. These were all vitally important concerns for military and aerospace products.
August 15, 2023

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.
July 26, 2023

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.
July 03, 2023

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.”
April 25, 2023

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.
March 08, 2023

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.)
February 23, 2023

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.
January 19, 2023

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).
December 15, 2022

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.
November 03, 2022

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.
September 12, 2022

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.
July 04, 2022

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.
May 13, 2022

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%).
April 14, 2022

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.
March 11, 2022

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.
December 16, 2021

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.
December 02, 2021

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.
November 04, 2021

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.
September 23, 2021

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.
August 18, 2021

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.
July 19, 2021

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.
June 15, 2021

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.
May 19, 2021

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.
February 12, 2021

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.
January 21, 2021

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.
September 17, 2020

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.
July 15, 2020

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.
June 26, 2020

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.
April 15, 2020

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
February 15, 2020

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.
January 27, 2020

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.
May 15, 2020

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.
December 15, 2019

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.
March 27, 2020

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.
January 23, 2020

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.
October 21, 2019

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.
September 05, 2019

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.
April 26, 2019

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.
April 11, 2019

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.
February 25, 2019

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.
February 11, 2019

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.
December 07, 2018

Flexible Thinking: Achieving Continuous Flexible Circuit Innovation

Since their introduction, flexible circuits have continued a steady climb from relative obscurity to center stage in the world of electronic interconnections. Today, they are among the most popular choice for solving challenging electronic interconnection problems. Those who use this technology on a regular basis are familiar with the many reasons for the popularity of flex.
July 02, 2018

Flexible Thinking Redux

Flexible circuits are known by a few different names depending on one’s global location and language: flexible printed circuits, FPCs, flex circuits, flexi circuits, flexibles, bendables and a few others that are application-specific such as flexible heater circuits and controlled impedance cable constructions. While flex circuits are an original and foundational interconnection technology for electrical and electronic products (one of the first patents for electrical interconnections, issued at the turn of the last century, was arguably a flexible circuit), over the years there have been several forays into technological extensions of the basic idea.
March 31, 2017

Flexible Thinking: The Benefits of Employing a Standard Grid Pitch in Design

The industry at large needed to jump on the learning curve and overcome its fear of the unknown. One of the most vexing concerns at the time (an arguably still today) is that terminations beneath the area array package were unseeable. Given the fact that then, as today, solder joints were a major cause of failure, there was much consternation over the quality of the joints.
May 11, 2016

Flexible Thinking: Process Engineering—PCB Manufacturing’s ‘Delta Force’

Process engineers serve a vital function on the front line of printed circuit manufacturing. They are often, if you will, the “Delta Force” that subdues and controls that which is one of the mortal enemies of manufacturing…process variation.
January 14, 2015

3D Printing in Electronics - A Perspective

Knowing the value of a product or technology is key to making the right decision. Appreciating the value of an element of business is evermore important as the rate of change surrounding an industry accelerates. This brings us to one of the current buzz subjects in our industry: 3D printing. Understanding what it is and what its value is to a company and that company's ability to improve its place in the industry is vital.
July 31, 2013

The E.I. Files: The Electronics Industry's Black Swans

First proposed in 2007, there is a potential electronics industry "black swan" technology quietly being developed and refined. It is one that could greatly and positively impact, at once, the cost, reliability, and environmental friendliness of electronic manufacturing by simply eliminating the soldering process.
April 17, 2013

Flex Circuits and Photonics: A Pairing for the Future, and the Here and Now

Photons are making continuous headway into the world of electronics. One thing that the basic data carriers (electrons, microwaves and photons) have in common is that flexible circuits are being increasingly looked to for help in managing their data transmission function.
November 29, 2012

Stretching the Limits of Flex

Those steeped in flexible circuit design and manufacture for any length of time fully appreciate the long list of benefits that only flexible circuits can offer. Some of the most fundamental benefits of flex circuit technology have been exploited since the earliest days of the technology. Joe Fjelstad explains.
October 04, 2012

Flexible Thinking: Circuit Flexibility (and How to Achieve it)

The most common interpretation of the word flexible, as applied to the flex circuits that the industry currently makes, is something capable of being bent repeatedly without breaking. Joe Fjelstad discusses a few other definitions of flexible that are worthy of consideration when using the term, for their ability to unlock new thinking patterns relative to what is flexible.
September 26, 2012

Technology Roadmaps: Thoughts and Observations

If one is without a sense of the direction their technology is headed, odds are that they will sooner find themselves on the road to ruin than the road to success. A technology roadmap is a critical tool in helping a company make informed decisions. By Joe Fjelstad.
October 13, 2011

Something Old, Something New: Stretchable Circuits and Elastronics

The stretching of circuits to alternately increase and decrease the length of a circuit has proven useful for electronic products and assemblies for years. Stretchable circuit technology and elastronics are poised to take on challenges that cannot be easily met by flexible circuit technology alone. Keep them in mind next time you find yourself in need of a little more "spring" in your design. By Joe Fjelstad.
July 14, 2011

Stretchable Circuits: The Emergence of "Elastronics"

The stretchable circuit is an interesting and promising new branch on the flexible circuit tree. The stretching of circuits to alternately increase and decrease the length of a circuit has proven useful for many years. The European Union has funded research in this area through such initiatives as the STELLA project.
November 18, 2010

Flexible Thinking: An Alternative Approach to Rigid-Flex Assembly

The fundamental approach to manufacturing rigid-flex has remained constant for the 40-plus years of rigid-flex history. But is there a better way? What if one could produce a circuit that was rigid throughout the manufacturing process and only become flexible in the final step? In other words, what if one could make a rigid circuit assembly, flex?
October 07, 2010

Reasons Why The Flex Market Continues to Shine

According to IPC market statistics, flexible circuits continue to be the brightest sector of the overall printed circuit market. The reasons for this are many but, at the end of the day, it generally boils down to the fact that flexible circuits are an excellent way to solve interconnection challenges in a cost-effective way.
August 12, 2010

Flexible Thinking: Flexible Structures for Data Transmission

Flexible circuit cables offer some significant advantages for facilitating the movement of data between elements of a system that must also be moved or flexed. However, there is a balancing act involved and there is more than one master to be served to create a system that is robust, reliable and easily manufacturable.
July 21, 2010

Flexible Thinking: Supporting Components on Flex Circuit Assemblies

With proper planning, stiffeners can be designed to aid assembly through the designed manufacture of a flex circuit that can be handled as if it were a rigid circuit board. Such constructions can be accomplished by using any one of several methods.
April 29, 2010

A Simple Approach to Flex Manufacture, Assembly

Flexibility, the single attribute that makes flex so attractive, also makes flex circuits more difficult to build. What if we could produce a circuit that was rigid throughout the entire manufacturing process and only become flexible in the final step?
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