What is Volume Resistivity in High Frequency PCB?

January 15, 2025

1. Introduction

"In the high-frequency field, volume resistivity is the guardian of signal quality." In high-frequency PCB design, Volume resistivity not only concerns the efficiency of signal transmission but also directly affects circuit stability and reliability. As electronic devices continue to evolve towards higher frequencies and smaller sizes, understanding and optimizing volume resistivity has emerged as a key challenge for design engineers.

2. Understanding Volume Resistivity

Volume resistivity refers to the resistance a material offers to the flow of current under specific conditions, measured in ohm-meters (Ω·m). In high-frequency applications, the volume resistivity of materials affects signal attenuation and the suppression of electromagnetic interference. If the volume resistivity is too high, it can lead to increased signal loss and noise, adversely affecting the overall performance of the device. Therefore, selecting suitable materials to achieve low volume resistivity is critical in high-frequency PCB design.

3. Comparison of Volume Resistivity in Different Materials

The two tables below illustrates the changes in the DK thermal coefficient at varying temperatures for Taconic, Rogers, and Wangling materials, offering a clear comparison of their performance stability in high-frequency PCB applications.

The table below shows a comparison of the volume resistivity of various materials:

Note: The above data are approximate values for PCB materials. The specific values may vary due to environmental or material differences.

From the table, it is evident that Taconic and Wangling materials have relatively low volume resistivity, making them suitable for high-frequency signal transmission. In contrast, while FR-4 has cost advantages, its performance in high-frequency applications is limited.

However, the CPB material with unique advantages that I would like to introduce is Rogers DiClad 527 laminates，which is the ideal PCB substrate for your different needs

Rogers DiClad 527 laminates are woven fiberglass reinforced, PTFE-based composite materials designed for use as printed circuit board substrates. These laminates offer a unique combination of features that make them an excellent choice for a wide range of applications.

4.Key Features and Benefits of Rogers DiClad 527

4.1 Higher Fiberglass Reinforcement to PTFE Ratio: The carefully controlled ratio of fiberglass reinforcement to PTFE content provides a higher dielectric constant range , ensuring better performance and stability.

4.2 Enhanced Dimensional Stability and Registration: This ratio also results in better dimensional stability and registration, making it easier to manufacture high-quality PCBs.

4.3 Stable Dk across Wide Frequency Range: DiClad 527 laminates offer a very stable dielectric constant(2.40-2.60) over a wide frequency range , ensuring consistent performance in various applications.

4-1. The stable dielectric constant of DiClad 527

4.4 Minimal Circuit Losses at High Frequency : These laminates have low circuit losses at high frequency and a dissipation factor of 0.0018 at 10GHz. Ideal for high-frequency applications where signal integrity is crucial.

4.5 Negligible Performance Variation in High Humidity: Even in high humidity environments, DiClad 527 laminates exhibit negligible performance drift, ensuring reliable operation.

4.6 Copper Foil Options: Available with copper foil thicknesses of 1/2 oz. (18µm) and 1 oz. (35µm), DiClad 527 laminates can be customized to meet your specific requirements.

5.The typical applications of DiClad 527 laminates :

• Military Radar Feed Networks
• Commercial Phased Array Networks
• Low Loss Base Station Antennas
• Missile Guidance Systems
• Digital Radio Antennas
• Filters, Couplers, LNAs

6. Conclusion

"In the sphere of high frequency PCBs, volume resistivity is the unsung hero, quietly shaping the future of electronics."It is clear that volume resistivity directly relates to signal quality and circuit reliability. By optimizing designs and selecting appropriate materials, engineers can effectively enhance circuit performance and ensure reliability in high-frequency applications, which lay the foundation for the success of electronic products.