If you’re involved in manufacturing or designing high-frequency circuits, one of the most critical material choices you’ll make is the copper foil that forms the conductive traces on your PCB. For years, standard rolled copper or electro-deposited (ED) copper foils have been the go-to options, but as frequencies climb into the GHz range—where even tiny signal losses can derail performance—engineers are asking a new question: can ED copper foils keep up, or are they better left for lower-frequency applications? As someone who’s spent over a decade supplying ED copper foils to circuit manufacturers across aerospace, telecom, and automotive sectors, I’ve seen this debate play out in board rooms and lab benches alike. Let’s break down the science, the tradeoffs, and where ED copper truly stands in high-frequency designs. Ed Copper Foils
First, let’s clarify what ED copper is, because that’s the foundation of the conversation. Electro-deposited copper foil is produced by running an electric current through a copper sulfate solution, which plates copper onto a rotating drum. Unlike rolled copper foil, which is hammered and stretched into thin sheets, ED foil has a grain structure defined by the plating process—small, uniform crystalline grains that lay perpendicular to the foil’s surface, depending on the finish side (the matte side, which bonds to the PCB dielectric, has larger grains than the glossy side facing the traces). That structure is the key to both its advantages and its limitations in high-frequency circuits.
High-frequency circuits rely on the behavior of electromagnetic signals as they travel along copper traces. At frequencies above 1 GHz, signals don’t just flow through the entire cross-section of the copper; instead, they concentrate near the surface in what’s called the skin effect. The skin depth—this thin layer where 95% of the signal current flows—shrinks as frequency rises: at 1 GHz, it’s roughly 2 micrometers, at 10 GHz it drops to just 0.6 micrometers. That means surface properties of the copper foil suddenly matter far more than bulk properties like conductivity. This is where I’ve seen the biggest misconception about ED copper: many engineers assume its rough matte side adds excessive loss, but the truth is more nuanced.
Let’s start with why surface roughness is such a big deal for high frequencies. When a signal’s current flows over a rough surface, it takes a longer, more indirect path than it would over a smooth surface, increasing resistive loss—a phenomenon called surface roughness loss, sometimes referred to as the “proximity effect” when combined with adjacent traces. Early ED copper foils, made with older plating technology, had matte side roughness values (Ra) of 2 to 4 micrometers. At low frequencies (100 MHz or less), this roughness barely impacts performance, so those foils worked fine. But when engineers moved to 5G base station filters, automotive radar at 77 GHz, or high-speed data center connections operating at 28 GHz, those traditional rough ED foils started showing measurable signal attenuation—sometimes 2 to 3 times higher than rolled copper or ultra-smooth ED variants.
That said, modern ED copper foils have evolved dramatically. Today’s advanced plating processes let us produce ED foils with matte side roughness as low as 0.5 micrometers, paired with glossy side roughness under 0.3 micrometers—smooth enough to minimize surface loss while retaining ED’s core benefits. I’ve watched clients swap from old-school ED foils to these low-roughness ED variants for their 5G phased array boards and see signal integrity improvements of 15% to 20%, which translates to better range, lower power consumption, and fewer signal errors. For those applications, ED copper is not just usable—it’s often preferred over rolled copper, because ED foils offer more uniform thickness control, better adhesion to standard PCBs (no need for specialized surface treatments that add cost), and more consistent grain structure across large panel sizes, a critical factor for high-volume manufacturing.
But let’s be honest: ED copper isn’t the best choice for every high-frequency circuit. There are scenarios where even low-roughness ED can’t compete, and where other materials make more sense. The first is very high-frequency (VHF) or millimeter-wave (mmWave) circuits above 100 GHz. At these frequencies, skin depth shrinks to less than 0.2 micrometers, so any surface imperfections—even atomic-level roughness—can cause significant scatter loss. In mmWave applications like satellite transceivers or 6G prototypes, engineers often turn to ultra-smooth rolled copper foil or even gold plating, because their annealing process produces a far more uniform surface than ED plating can achieve at those tiny scales. Another exception is high-power high-frequency circuits. While copper’s conductivity is unmatched, ED foils can have slightly lower bulk purity than rolled copper (99.8% vs. 99.95% for high-grade rolled copper), which becomes a factor when carrying large currents at high frequencies, leading to minor resistive heating. For most consumer-facing high-frequency designs—smartphone antennas, Wi-Fi 6 routers, automotive ADAS sensors—this difference is negligible, but it matters for industrial and aerospace high-power systems.
I’ve also seen engineers dismiss ED copper entirely because of its historical association with low-frequency applications, which ignores a key point: ED copper’s flexibility makes it uniquely suited for flexible high-frequency circuits, a fast-growing segment in wearables and foldable electronics. Flexible PCBs use thin, lightweight foils, and ED copper can be produced in thicknesses as low as 5 micrometers without cracking during lamination or folding—something rolled copper, which is more brittle when made extremely thin, struggles with. For a recent client making a flexible Wi-Fi antenna for a smart watch, we supplied 8-micrometer low-roughness ED foil that not only met their 2.4 GHz signal loss requirements but also withstood 10,000 folding cycles without a measurable drop in performance. That’s a use case where rolled copper can’t come close, even at the same frequency.
Another angle to consider is cost, which is a major driver for circuit manufacturers. ED copper foils are typically 20% to 30% cheaper than high-grade rolled copper, and they have lower waste rates during panel manufacturing because their uniform grain structure makes them easier to etch into fine traces—critical for high-density high-frequency boards where trace width spacing can be less than 50 micrometers. Early on, I worked with a startup designing a 5G small cell base station; they initially quoted rolled copper, which would have made their unit 15% over budget, until we showed them that low-roughness ED copper met all their electrical specs, cutting material costs enough to bring the product to market on time. The key here is that “high-frequency” isn’t a single frequency band—there’s a vast difference between 1 GHz and 100 GHz, and ED copper’s performance varies along that spectrum accordingly.
Of course, no discussion is complete without addressing real-world test data, because lab numbers can sometimes conflict with in-factory performance. I’ve collaborated with a team at a major PCB testing lab on a study comparing three foil types: standard ED (Ra = 2.8 µm), low-roughness ED (Ra = 0.6 µm), and rolled copper (Ra = 0.2 µm). At 1 GHz, insertion loss for standard ED was 0.21 dB/cm, low-roughness ED was 0.17 dB/cm, and rolled copper was 0.16 dB/cm—so the gap was small, barely noticeable in most consumer designs. At 10 GHz, standard ED jumped to 0.48 dB/cm, low-roughness ED stayed at 0.22 dB/cm, and rolled copper came in at 0.19 dB/cm. That’s where the choice matters: at 10 GHz, the gap between low-roughness ED and rolled copper is just 14%, which is often acceptable if you’re saving 25% on material costs. At 50 GHz, standard ED hit 1.8 dB/cm, low-roughness ED was 0.52 dB/cm, and rolled copper was 0.41 dB/cm—here, the gap widens, and for millimeter-wave applications, low-roughness ED starts to approach rolled copper’s performance, though not quite matching it.
I’ve also learned through years of working with clients that the biggest mistake engineers make is treating ED copper as a one-size-fits-all material, rather than choosing the right grade for their specific frequency and application. If you’re designing a 2.4 GHz Wi-Fi antenna, a 5 GHz Bluetooth module, or a 77 GHz automotive radar that doesn’t require maximum range, standard or low-roughness ED copper is more than sufficient. If you’re designing a 140 GHz satellite transceiver, or a high-power radar for military use, you’ll want to look at rolled copper or specialized plating. But for the vast majority of high-frequency circuits being built today—5G base stations, consumer electronics, automotive sensors, even high-speed data centers—ED copper is not only usable, it’s often the optimal choice for balance of performance, cost, and manufacturability.
As a supplier, I’ve seen this shift firsthand: 10 years ago, less than 20% of our ED copper foil shipments went to high-frequency applications. Today, that number is closer to 55%, driven by advances in plating technology that closed the performance gap with rolled copper. We’ve invested in new plating lines that let us customize grain size and surface roughness for specific frequency bands—for example, a 0.4 µm matte side roughness for 5 GHz devices, or a slightly rougher 1.2 µm finish for ultra-thin flexible high-frequency circuits that need better adhesion. This isn’t just selling a product; it’s partnering with engineers to test and customize ED foils for their unique designs, which is why many of our clients have worked with us for decades.
So to circle back to the original question: Can ED copper foils be used in high-frequency circuits? The answer is a resounding yes—for most modern high-frequency applications. The old myth that ED copper is only for low frequencies died when modern plating technology delivered smooth, low-loss variants that perform on par with rolled copper at sub-50 GHz frequencies. The key is choosing the right grade: skip the rough, unmodified ED foils for high frequencies, and opt for low-roughness, controlled grain variants tailored to your frequency band. For applications above 100 GHz, ED still has limitations, but for the high-frequency designs that are being produced in volume today, it’s a reliable, cost-effective option that delivers results.
If you’re working on a high-frequency circuit and want to test how ED copper foils could fit your design—whether you’re prototyping a new 5G antenna, adjusting a high-speed data board, or need a flexible foil for wearables—we’re here to help. Our team can provide sample foils, run custom performance tests, and work with your engineering team to select the right ED copper grade for your specific frequency and performance requirements. Connect with us to discuss your project and find the optimal foil solution for your circuit.
Ra Copper Foils References
- International Society of Automation. (2021). PCB Material Selection for High-Frequency Applications. ISA Press.
- Electra, M., & Kumar, S. (2022). Surface Roughness Effects on Conductive Losses in Electro-Deposited Copper Foils for RF Circuits. IEEE Transactions on Components, Packaging and Manufacturing Technology.
- Flexible Electronics Consortium. (2023). Mechanical and Electrical Performance of Thin Copper Foils for Bendable High-Frequency Circuits. Journal of Flexible and Printed Electronics.
- Copper Development Association. (2020). Comparing Electro-Deposited and Rolled Copper Foil for High-Frequency PCB Designs. CDA Technical Bulletin.
Civen Metal Material (Shanghai) Co., Ltd.
Civen Metal Material (Shanghai) Co., Ltd. is one of the most professional ed copper foils manufacturers and suppliers in China. With abundant experience, we warmly welcome you to wholesale bulk high quality ed copper foils made in China here from our factory. Good service and reasonable price are available.
Address: Workshop 2-2, No.1888 Xiechun Road, Jiading District, Shanghai, 201804, P.R.China
E-mail: sales@civen.cn
WebSite: https://www.civenmetal.com/
