New Low-Loss Materials for High-Speed PCBs

Faster data transmission, higher operating frequencies, and increasingly compact electronic devices are creating new demands for printed circuit boards. For conventional applications, standard FR-4 may still be perfectly adequate. As signal speeds increase, however, signal transmission losses are becoming an increasingly important issue.

This is where low-loss and ultra-low-loss materials come into play. These materials are designed for high-speed digital, high-frequency, and RF applications where minimizing signal loss is critical.

Choosing a “better laminate” is not the only consideration. The resulting signal attenuation depends on a combination of material properties, trace geometry, operating frequency, and the properties of the copper foil. IPC points out that at higher frequencies, dielectric losses become increasingly significant, while copper foil roughness can further increase overall attenuation.

Why May Standard FR-4 No Longer Be Enough at High Speeds?

FR-4 remains one of the most widely used materials for PCB manufacturing. It is cost-effective, relatively easy to process, and offers a good balance of properties and cost for a wide range of electronic applications.

As frequency increases, however, the electrical properties of the dielectric become increasingly important. Key parameters include:

• Dk – dielectric constant, or the relative permittivity of the material,
• Df – dissipation factor, which characterizes dielectric losses,
• the stability of these parameters depending on frequency and temperature,
• the properties and roughness of the copper foil,
• the layer structure and trace geometry.

Put simply, the higher the required signal speed and operating frequency, the more important it becomes to control how much energy is lost during signal transmission.

According to IPC, overall attenuation is a combination of losses caused by the material itself and losses associated with the conductor, its geometry, and copper foil roughness. At higher frequencies, dielectric losses become increasingly significant.

Dk and Df: Two Key Parameters for Low-Loss Materials

When selecting a material for a high-speed PCB, two abbreviations appear frequently: Dk and Df.

Dk describes the dielectric constant of a material. It affects, among other things, signal propagation speed and the impedance of a transmission line. In high-speed designs, it is not only the Dk value itself that matters, but also how stable it remains across different frequencies and temperatures and within a particular PCB construction.

Df, or dissipation factor, is related to dielectric losses. In general, a lower Df means lower losses in the dielectric material. This is why materials designed for high-speed applications typically have very low Df values. For example, Rogers specifies a Df of 0.0027 at 10 GHz for low-loss materials RO4003C, while RO3003 has a Df of 0.0013 at 10 GHz.

New Generations of Materials Are Pushing the Boundaries

The development of materials for high-speed PCBs is focused on combining low electrical losses with good thermal stability, mechanical reliability, and reasonable manufacturing requirements.

One example is the range of low-loss materials developed by Rogers Corporation. The RO4000 series is designed for high-frequency applications and includes materials such as RO4003C and RO4350B. According to the manufacturer, RO4003C has a Dk of 3.38 ± 0.05 and a Df of 0.0027 at 10 GHz. It can also be processed using methods similar to those used for standard epoxy/glass materials, which can simplify multilayer PCB manufacturing.

Rogers also offers the RO3000 series, whose materials are designed for applications requiring very low losses. For example, RO3003 has a Dk of 3.00 ± 0.04 and a Df of 0.0013 at 10 GHz.

The development of the copper foil itself is also important. With its RO4000 LoPro materials, Rogers uses technology designed to reduce conductor losses and improve insertion loss and signal integrity. The manufacturer states that these solutions are suitable for designs operating above 40 GHz.

Low-Loss Materials from Other Manufacturers

The development of low-loss materials is not limited to a single manufacturer. Isola, for example, offers low-loss materials such as I-Tera MT40 and Tachyon 100G.

I-Tera MT40 is designed for high-speed digital as well as RF and microwave applications. The manufacturer specifies a Dk of 3.45 and a Df of 0.0031. The material is also designed to be compatible with conventional FR-4 manufacturing processes.

Another example is Tachyon 100G, which is designed for very high-speed digital applications. Isola specifies a Dk of 3.02 and a Df of 0.0021. The material is intended for applications with data rates of 100 Gb/s and above. Its construction also incorporates very smooth copper foil to help reduce conductor losses.

Another important example is Panasonic Industry’s MEGTRON series. These low-loss materials are designed for multilayer PCBs requiring very low transmission losses and high thermal resistance. MEGTRON 6 and MEGTRON 7 are intended, among other applications, for ICT infrastructure and high-speed data transmission.

Smoother Copper Can Mean Lower Losses

When designing a high-speed PCB, it is easy to focus primarily on the properties of the laminate. However, that can be misleading.

As frequency increases, the skin effect becomes increasingly significant. High-frequency current tends to concentrate closer to the surface of the conductor, meaning that the actual current path is also affected by the surface structure of the copper.

In its technical material, IPC compares PCB constructions using standard and smoother copper foil. In a test at 5 GHz, the construction with rougher copper foil showed higher losses than the construction using smoother foil.

This is why modern high-speed materials increasingly feature copper foils described as VLP, HVLP, or ultra-smooth copper.

Material selection is therefore no longer simply a matter of asking: “Which laminate should we use?”

A more important question is: “How will the entire system perform – the dielectric material, copper, trace geometry, and operating frequency?”

What Do Low-Loss Materials Bring to PCB Manufacturing?

Low-loss materials can be important in applications such as:

• high-speed data links,
• servers and data centers,
• telecommunications equipment,
• 5G and future 6G systems,
• high-frequency and microwave applications,
• radar systems,
• automotive electronics,
• high-speed backplanes and daughtercards.

In these applications, the main challenge is no longer simply whether a PCB can carry a signal. The challenge is maintaining signal quality, timing, and signal integrity at increasingly high frequencies and data rates.

This is why material manufacturers combine low Df values with controlled Dk, low copper foil roughness, thermal stability, and suitable mechanical properties.

Low-Loss Materials Do Not Automatically Mean the Best Choice

It is important to emphasize that a low-loss material is not automatically the right choice for every PCB.

More advanced materials can be more expensive, and their processing may require tighter control of the manufacturing process. The availability of a particular material, its thickness options, prepregs, copper foils, and compatibility with the overall PCB construction are also important considerations. Material selection therefore needs to be based on the requirements of the specific application.

For example, if a design operates at relatively low frequencies and uses short signal paths, a standard material may be entirely adequate from both a technical and economic perspective. On the other hand, for high-speed connections where signal attenuation, impedance, jitter, or precise signal timing are critical, material properties can become a decisive factor.

The Future Lies in Combining Low-Loss Materials with Precise Design

The development of high-speed PCBs is therefore not simply about finding a material with the lowest possible Df.

Increasingly, the focus will be on optimizing the entire system. The material needs to work together with the appropriate layer stack-up, controlled impedance, trace geometry, copper foil type, and the manufacturing capabilities of the PCB manufacturer.

New low-loss materials are one of the ways the PCB industry is responding to the growing requirements of data centers, telecommunications, automotive electronics, and other applications where transmission speeds continue to increase.

For PCB manufacturers, this also creates a new challenge: not only being able to manufacture PCBs using these materials, but also processing them correctly and maintaining their electrical properties throughout the entire manufacturing process.

This will play an increasingly important role in determining how fast and reliable the next generations of electronic devices can be.

Low-Loss materials:

IPC. Base Material Consideration for High Speed Printed Circuit Boards. IPC.

Rogers Corporation. RO4000 Series Laminates. Rogers Corporation.

Rogers Corporation. RO3000 Series Laminates. Rogers Corporation.

Isola Group. Tachyon 100G Laminate and Prepreg. Isola Group.

Isola Group. I-Tera MT40 Laminate and Prepreg. Isola Group.

Panasonic Industry. Circuit Board Materials – MEGTRON Series. Panasonic Industry.