Flexible PCBs for High-Frequency

High-frequency applications often require a device to be small, lightweight, rugged and resistant to environmental factors. A flexible PCB is the perfect solution for these types of applications. Whether you need to track inventory in a warehouse, ship products from a fulfillment center or operate your business’s online storefront, you likely use modern electronics that communicate via radio frequency (RF). These devices must be able to withstand a lot of movement and pressure over an extended period of time. Rigid circuit boards simply aren’t a good fit for these conditions. Flexible or flex-rigid PCBs, on the other hand, can provide you with the performance you need.

Unlike rigid PCBs, which have a base of fiberglass or metal, flexible circuits typically are made from a thin polymer film. This type of material allows the circuit board to remain flexible and resilient after thermosetting. It also resists humidity, making it a great choice for a wide variety of industrial and commercial applications.

Another advantage of a flexible pcb board is that it’s less expensive than a rigid one. This is because the manufacturing process for a flex PCB requires fewer steps and uses fewer materials. A resulting lower price tag can save you money on the overall cost of production, as well as on testing, wire routing errors, rejects and reworking.

Flexible PCBs for High-Frequency Applications

To make a flex PCB that performs well in high-frequency applications, you need to start with the correct raw materials and stack up. Copper is the most common conductor material used for flex circuits, and you can find it in both fully annealed and low-temperature annealed forms. These options help your circuits to be more conductive and have better flexing properties than un-annealed copper. Having the right copper thickness helps reduce I-beaming and stress points in your circuits when they bend, which minimizes damage and ensures a smoother signal. It’s also important to stagger traces on multi-layered flex circuits so that they are perpendicular to the neutral bending axis of the device.

The surface finish on a flex PCB is just as important as the core materials. A quality finish protects the copper from oxidation and makes it solderable. The best option for this purpose is Electroless Nickel Immersion Gold (ENIG). It’s an inexpensive way to get a durable, high-quality finish that will not degrade with continuous flexing.

Other key materials for a flex circuit include a suitable coverlay and stiffeners. Photo imageable coverlay materials can create intricate openings for surface mount components, and a mechanical stiffener can rigidize SMT, connector and other areas of your flex circuit. Reference plane layers and shielding can also be added to increase impedance control and signal integrity. It’s also critical to design your flex circuit with a consistent copper thickness to avoid skin effect and crosstalk. The thickness should be closely monitored to ensure it doesn’t change during flexing. This is something that you’ll want to discuss with your manufacturer before production starts. They’ll be able to recommend the optimal thickness for your application.