Rigid Flex PCBs and Your Future: Smart, Effective Designing

Created: February 27, 2018
Updated: September 25, 2020

Flexible PCB circuit

Oftentimes, in terms of PCB design, we are tasked with fitting a square peg into a round hole. Fitting thousands of various components onto a board no larger than a dollar bill, and maybe even a quarter, we always seem to be limited to the 2D plane of predetermined space within our equipment or device.

We’ve all been there: after putting the finishing touches on a PCB design, you take a look at the space requirements of the device only to find that you’ve exceeded what is allowed in. Now it’s back to the drawing board.

Without any alteration to this 2D plane, we can certainly make efforts to condense into a higher and higher density of interconnects making it an ultra HDI PCB. We could increase the number of layers of the board incorporating the use of multilayered vias. We might even be able to push the borders of our edge clearance tolerances allowing for more components to be crammed on to our plane. Or, we can explore the benefits of rigid flex PCB design.

What is Rigid Flex for PCBs?

As the name implies, rigid flex PCBs are comprised of both rigid and flexible PCB material. The rigid portion of the PCB as our familiar-looking board housing many of the components. The flex portion of the PCB is (again, as it sounds) a flexible material that is designed to bend, twist, roll over, sit, and play fetch… wait… am I mixing things up?

Flex PCBs alone are pieces of marvelous engineering. Allowing you to even house the components onto this flexible material, they can fit into nearly any shape and application (however mounting these to your device can be a bit tricky as there is no solid “backbone” to fall back on). Rigid flex takes things to another level, allowing you to firmly mount the rigid portion on to your device and use the flexible portion to expand space requirements to 3D.

Aerial view of a flexible circuit layer

Flex circuits can be printed and shaped just like rigid boards

Five of the Ample Benefits of Rigid Flex Technology

The rigid flex technology has captivated my heart and I have nothing but great news to share with you through the rest of the article. Let’s explore what other benefits you’ll find within the rigid flex space:

Form to the Device: Although briefly stated above, this deserves its own section. Instead of our PCB design being bound by the space within the device, if we are clever, we can now form our PCB around the device in 3D space. This means that no mounting surface is off limits to where we can put our boards. As long as we can run a flex material from one rigid board to the next, we can integrate the design into any device shape, no matter how funky it may look.

Lightweight and Compact: Beings that the material is vastly different from your typical rigid board, and due to the nature of its design inspiration, the flexible material that it’s built with just so happens to be a much lighter weight and a much more compact design. This will allow you to save not just space, but also weight.

Designed Without Solder Joints: The way a rigid flex board is constructed is by sandwiching a flex board in between two (or more) rigid boards. This method of assembly is fantastic due to the lack of extra solder joints, connectors, or contact crimps. This will only serve to increase its overall structural integrity as it’s put through its flexible paces.

Fewer Materials = Fewer Cost: Although not the case 100% of the time (maybe more like 98% of the time), you’ll be using less material overall when incorporating flex material into your rigid design. This will often time lead to a decrease in cost for you and less work for your procurement team.

Protection Against Exposure: Another added benefit of flex material within the rigid flex designs is the protection it offers itself throughout the longevity of its life against UV rays, radiation exposure, and harmful chemicals that may be a variable that needs consideration.

Flexible PCB interconnect

Flex layers can also act as interconnections solutions between PCBs

Design with Rigid Flex Today

Now that you’ve been introduced to the fantastic benefits of a rigid flex PCB system, I would almost be offended if you didn’t start incorporating it into your designs from here on out. Keeping in mind the fact that adding a flex into your rigid flex PCB will allow you to design in 3D space, save weight and cash, increase joint strength, save materials, and protect against exposure, I highly encourage you to consider the implementation of this great piece of technology.

The only thing left to do is make sure that your PCB design software can handle all of the amazing designs you’ll be able to make with rigid flex technologies. It’s not just about whether your software has the features you need like real-time error checking, and auto-interactive routing, but also that it has the features you need in a layout interface that keeps things easy to use like in Altium Designer®.

If you are wondering what a rigid flex design might look like on your PCB design software, talk to an Altium expert today.

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