New RF Materials Offer Options for RF Designers

Estimated reading time: 2 minutes

The RF materials arena has changed quite a bit in the past decade. The newest thermoset laminates boast performance numbers that are almost competitive with PTFE, but without the manufacturability challenges.

At IPC APEX EXPO this year, I spoke with Brent Mayfield, business development manager at AGC Multi Material America. Brent walked through some recent innovations in RF materials, advances in resin systems, and the many design trade-offs for RF engineers to consider for each material set.

Andy Shaughnessy: Brent, this issue focuses on RF design techniques. What are your thoughts on the RF materials landscape and the challenges your customers are facing?

Brent Mayfield: Traditionally, much of the RF business has been focused on aerospace and defense. The RF material sets have historically been considered unfriendly to the fabrication process, which limited commercial adoption. As things have expanded, RF applications have spread across all electronics. The commercial side is now leaning into phased arrays and trying to do what the military has been doing for decades, when they were typically using PTFE materials. Often, with these high-performance phased arrays, you weren’t getting what you wanted with yields, but it was the only way to get the performance. The thermoset materials that were available at the time really couldn't achieve that type of performance.

Around 2015, we started seeing a turn toward high-speed digital materials, and then it became a lot easier to build RF products. But there are still performance challenges. We always ask, “What do you need to achieve from the material?” Often the response is, “We need it to be ultra low-loss.” If you're looking for what you could have gotten with PTFE, you won’t quite get that. While the Df specification for the latest thermosets is getting close, there are mechanical performance characteristics that just don’t match up. For instance, with PTFE, you have very good adhesion to copper foils with minimal roughness. With thermosets, you just can't achieve the same level adhesion of copper. It's about trying to strike a balance. How do you know what will work? If I go to consumer goods, it's considered a high-end product where they will deal with drop tests. With a radio for first responders, the drop test is much higher. How do we deal with this type of issue? Often, we start by focusing on electrical performance, but when we get to mechanical performance for different types of applications, we see that there are limits to what we can do.

We have to do a lot more engineering work. Even in the defense industry, there's a lot more volume using high-performance thermosets. Added to that are the commercial OEMs looking closer at the cost. What's the manufacturability? That's our focus. PTFE isn’t going away. There are some very special things about PTFE; it is still best for high-power—high-power antennas, RF power amplifiers, high-power couplers, etc. But the thermoset will lead the way from a volume perspective if that isn’t already happening. How do we start bettering some of the performance characteristics from a mechanical standpoint so that these thermosets can do some of the things that maybe you're still reserving for PTFE now?

To continue reading this interview, which originally appeared in the April 2025 Design007 Magazine, click here.