Monthly Archives: December 2017

The Power of Flexible Circuits

I have a story to share.  Picture a beautiful, fall day filled with sunshine and warm winds.  Just after dinner a family is out in their yard.  The father and older son are finishing chores before dark and a little boy is playing in the yard with the family puppy.  In a split second that puppy ran into one a thick, dense cornfield and this four year old boy followed, chasing after his favorite pet.  It was one of those split second moments that every parent fears.   If you have ever been in a corn field in the Midwest, you know, your visibility is limited to maybe a row or two in front of you and maybe a row or two to the sides.

It quickly became apparent that this family was going to need help and law enforcement was called.  Within an hour there were 160 trained volunteers from the surrounding communities and a command center was set up.  Ten years ago, this would have been what you would typically think of as a man-hunt with chains of people walking through the fields.  The scene looked significantly different on this fall day.  The command center was able to utilize drones enabled with infrared and heat sensing technology, a helicopter with similar technology to cover a larger area, the GPS from the tractor that planted that field was able to accurately display where each and every stalk of corn was and all 160 of those searchers were able to communicate real-time.

So, why do I tell you this story in a flexible circuit column?  I tell this story, because each of those items just listed contain a flexible circuit.  Our industry accomplishes some pretty amazing things.  We regularly hear that flex and rigid flex is a significantly growing portion of the world wide PCB market but, speaking only for myself, I don’t always take time to really think about the end applications that flex enables.  Let’s look at a few of the known benefits of flexible circuits and what type of products we may interact with that have been, or are being, developed to take advantage of this.

Advantages of flexible Circuits:

Solve Product Packaging Problems:  Flex allows for a 3-axis connection.  It is able to bent and folded around corners eliminating the need for discrete pieces.  It is easy to think of products that take advantage of the space saving benefits of flexible circuits:  portable medical devices such as insulin pumps or heart rate monitors, hearing aids, smart phones and tablets, cameras.  As consumers, we are requiring our electronics to be smaller, lighter and at the same time have increased functionality.  Flexible materials allow designers to meet those demands.

Reduce Assembly Cost:  Flex eliminates hand-wiring and provides additional cost savings when purchasing costs for multiple wiring and component pieces are factored in.  Home monitoring bracelets and wearable electronics are a good example.  The product needs to be light weight and durable, wire and flexible circuits are both options.  A simple flex circuit eliminates time for assembly, purchasing costs and inspection costs by solving the problem with just one unit.

Reduces both weight and volume:  This is a big one.  Bulky wire harnesses and solder connections can be replaced with thin, light weight rigid flex.  It is not uncommon to see studies showing that this savings in weight and space can be near 60%.  Aerospace is a perfect example of an industry that benefits from reduction in weight and volume.  With aircraft, rockets, missiles, etc., weight is an expense.  Any opportunity to reduce weight and space translates to a product that is less expensive to operate.  The fun little TV screens that are being built into aircraft so we are always entertained, lighting systems in the airplane, engine controls, braking systems, are all products that have been able to take advantage of flexible materials.

Dynamic Flexing:  This is easy.  Anything with a hinge!  The one I use every day is my laptop.  Let’s not forget printers, disk drives, cameras, and robotic arms.

Thermal Management:  Flexible dielectrics offer a greater surface to volume ratio than round wire and this extra surface facilitate the heat away from the circuit.  Rigid PCB dielectrics often act as a thermal insulator inhibiting the flow of heat.  One area of significant growth in flexible circuit designs is the LED lighting market.  Automotive and aircraft applications, especially with the combined benefit of lighter weight and improved thermal management, are increasing the usage of flex.  Examples include headlamps, interior lighting, and interior electronics, just to name a few.  One of my favorite applications is LED lights in a pair of high top tennis shoes.  This application is not just your typical shoe that lights up when you walk; this high top was designed with an artistic LED lit pattern throughout the shoe.  It might not be the most high-tech application, but it is eye catching and fun.

Improved Aesthetics and Bio-Compatibility:  Appearance can impact decisions when the end user is exposed to functional elements of the product.   For example, a simple hand-held medical device being used in a doctor’s office had a wire that was visible to the patient.  Although the medical device was working perfectly, patients perception of and confidence in the procedure was not high.  This was traced back to patients not being comfortable with the perception of the wire.  That simple wire was replaced with a very simple flexible circuit, so simple, there were only two traces.  But, by making this simple change, the patient’s perception and confidence in the medical device skyrocketed.

Polyimide is also bio-compatible.  Most often, the polymide material is fully encapsulated before being inserted into the body.  New developments are exciting.  Polyimide laminate with gold, rather than copper traces are fully bio-compatible and being tested as sensors to be implanted into the human body.  This development is also aided by additive technology that allows trace size in the 5 to 10 micron range, significantly shrinking the package size as well.  There are exciting things on the horizon.

Intrinsically more reliable and reduce the opportunity for operator error:  Flexible circuits can significantly simplify the system design by reducing the number and levels of interconnection required.  Because the design is controlled by the artwork, the opportunity for human error is eliminated.   Aerospace is great example.  Spacecraft are subjected to many kinds of dynamic forces, especially during take-off.  In traditional PCB’s these vibrations contribute to failure.  Rigid flex are made to twist and flex and are a benefit in these harsh environments.  Solder joints, crimps, etc., are also at risk for failure in these conditions.  Flexible circuits can remove this concern by eliminating connections.

Yes, our industry has developed so many interesting, life enhancing and lifesaving products and for that we should all be proud to be a part of the growth in this market.  To finish the story I started earlier, this little boy emerged from the field, a little tired, very muddy and mostly angry that he still had not found his puppy.  Guess what.  The person stationed at the edge of the field that spotted him was able to notify his parents and the command center immediately with his cell phone.  Which, yes you guessed it, also contains a flexible circuit.

Contact us if you need any advice or assistance with your flexible circuit needs!

Tara Dunn, Omni PCB