# 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.

Unfortunately, using only familiar tools limits our ability to come up with optimal or even superior solutions. Hopefully, what follows will help you avoid some of the traps conventional wisdom doesn’t always give guidance on.

But first, having written extensively over the years about flexible-circuit technology, I still try to find fresh ways to think about flexible circuits and their construction and use. In the process of thinking about what I might say here, a fun book I read in high school more than half a century ago came to mind. The title of that book is Flatland: A Romance of Many Dimensions by Edwin A. Abbott [1]. In full disclosure, and as one might guess from the extended title, the book is not about geometry but is a rather entertaining read. I found it to be a useful book for stimulating thought.

In the book, almost every male character in Flatland has two major dimensions—X and Y—and many possible sides (thus, they have area), but they can only be perceived as lines when looked at from the reference of the planar world in which they exist. Women, on the other hand, are depicted as being  basic lines, and are required to make noise as they move about through Flatland should they be encountered head on and appear as a simple point. The protagonist (a square) encounters both Lineland and Pointland, but the encounter with a sphere from Spaceland is where the entertainment really begins. Trying to convince others of another dimension is no mean task, one learns. Many humans are resistant to accepting the teachings of science. The book proved useful over the years to a number of prominent scientists (including Carl Sagan) seeking to help the layperson understand the multidimensional space they envisioned and were attempting to explain.

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

02-11-2019

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: Achieving Continuous Flexible Circuit Innovation

12-07-2018

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.

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# Flexible Thinking Redux

07-02-2018

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.

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

03-31-2017

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.

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

05-11-2016

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.

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# 3D Printing in Electronics - A Perspective

01-14-2015

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.

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

07-31-2013

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.

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

04-17-2013

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.

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# Stretching the Limits of Flex

11-29-2012

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.

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

10-04-2012

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.

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# Technology Roadmaps: Thoughts and Observations

09-26-2012

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.

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# Something Old, Something New: Stretchable Circuits and Elastronics

10-13-2011

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.

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# Stretchable Circuits: The Emergence of "Elastronics"

07-14-2011

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.

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# Flexible Thinking: An Alternative Approach to Rigid-Flex Assembly

11-18-2010

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?

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# Reasons Why The Flex Market Continues to Shine

10-07-2010

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.

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# Flexible Thinking: Flexible Structures for Data Transmission

08-12-2010

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.

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# Flexible Thinking: Supporting Components on Flex Circuit Assemblies

07-21-2010

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.

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# A Simple Approach to Flex Manufacture, Assembly

04-29-2010

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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