Comparing Standard FR4 Attenuation with Alternatives Up to 16 GHz

Sunnysky wrote:

WHat is std FR4 attenuation up to 16 GHz
Compare some alternatives

To determine the signal attenuation of standard FR4 and its alternatives up to 16 GHz, we need to consider several factors. Signal attenuation in PCB materials is primarily due to dielectric losses and conductor losses, which include both resistive and skin effect losses.

Standard FR4:
- FR4 is a commonly used PCB material with a dielectric constant (Dk) typically around 4.5 at 1 MHz, but this value can vary with frequency. The dissipation factor (Df) for FR4 is relatively high compared to other high-frequency materials, usually in the range of 0.02 at 1 GHz, which can lead to significant signal attenuation at higher frequencies.
- As frequency increases, the dielectric losses in FR4 increase due to its Df, and the skin effect causes the conductor losses to rise, resulting in higher attenuation. At frequencies up to 16 GHz, the attenuation can become quite pronounced, though the exact value will depend on the specific type of FR4 and the dimensions of the conductors.

Alternative Materials:
Several high-frequency materials offer lower attenuation compared to FR4:
1. Rogers RO4000 Series: These materials, such as RO4350B, have a lower Dk and Df compared to FR4. For example, RO4350B has a Dk of around 3.48 and a Df of 0.0037 at 10 GHz.
2. Taconic RF Series: These materials are also designed for high-frequency applications, with lower loss characteristics compared to FR4. Taconic's RF-35 has a Dk of about 3.5 and a Df of 0.0018 at 10 GHz.
3. Isola I-Tera: I-Tera MT40 has a Dk of 3.45 and a Df of 0.0035 at 10 GHz, which is better than FR4 for high-frequency applications.
4. Arlon Microwave Materials: Arlon's 25N has a Dk of 3.38 and a Df of 0.0025 at 10 GHz.

Comparison:
- When comparing these materials to standard FR4, the key differences come down to the Df at high frequencies. Lower Df translates into lower signal attenuation.
- Rogers, Taconic, Isola, and Arlon materials are specifically designed to maintain signal integrity at microwave frequencies and will typically outperform FR4 in applications above a few GHz.
- The choice between these materials will depend on the specific requirements of your application, including the acceptable levels of signal loss, the environmental conditions, and cost considerations.

Do you have a specific application in mind or certain performance requirements for the PCB material? Knowing more about what you're looking to achieve will help in providing a more precise comparison.