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Microwave Circuit Board Material: Stable, Low Tangent PCB Laminates for High-Power Applications

Microwaves transmit data at high frequencies. Therefore, PCBs for microwave devices should handle high-power signals optimally. However, microwave applications vary nowadays, from military use to consumer electronics. Thus, you need to pick the best material for the specific application. We have covered the best microwave circuit board material and properties for the most typical ones to help you pick the right one for your project. Take a look!

What are Microwave Circuit Boards?

Microwave circuit boards are special radio frequency PCBs designed to work at signal frequencies in the megahertz to gigahertz range. These medium to extremely high frequencies are ideal for various applications, such as military radars and smartphones. The board requires special materials and technology to achieve this performance.

A microwave PCB

Microwave PCB Advantages

Microwave circuit boards have the following advantages.

  • High Speed: The low consistency and tangent of the signal loss enable faster and less impudent transmission.
  • High Stability: Microwave PCBs are stable at extreme temperatures and can run analog applications at 40 GHz.
  • Efficient Fine Pitching: You can mount fine-pitch components on the board efficiently without any issues.

A fine-pitch PCB assembly

A fine-pitch PCB assembly

  • Multifaceted: You can also create multilayer boards by aligning the layers into intricate patterns using low CTE components.
  • Reduced Costs: It is possible to mix the materials in a panel storage system. This action lowers assembly costs while optimizing PCB performance.

Key Parameters To Consider When Choosing Microwave Circuit Board Materials

These electrical and mechanical properties make microwave PCB materials suitable for different applications.

Dielectric Permittivity

Also known as relative permittivity, dielectric permittivity shows the measure of a material's dielectric properties relative to the dielectric properties of air at room temperature. This property is a function of frequency and affects the behavior of electric fields passing through the material. A low dielectric is better for high-frequency signals because it reduces parasitic capacitance between the conductive structures and copper traces. Additionally, permittivity determines planar structure geometries.

A fine-pitch PCB assembly

A high-frequency amplifier PCB

Loss Tangent

Dissipation factor or loss tangent gives a measure of the electromagnetic energy absorbed in the material and dispersed as heat. The property is also a function of frequency. Low-loss tangent materials are ideal for high-power and high-performance applications because they reduce losses in the transmission lines.

Surface Roughness

Surface smoothness or roughness can affect performance depending on the application. Usually, this interference has to do with the layer depositing resolution and adhesion characteristics.

Thermal Conductivity

Thermal conductivity measures how well materials conduct heat. Poor thermal conductivity can limit a device's performance by minimizing the stack's overall thermal conductivity.

Dielectric Strength

This property measures the required electric field strength to begin stripping electronics from the dielectric material. It is a vital property for high voltage and power applications because it can limit performance.

Best Microwave Circuit Board Materials

There are several microwave PCB materials, but the following are the top 10.

Isola PCB Laminates (High-Performance)

Isola has been a pioneer in manufacturing and developing copper laminating solutions for multifaceted PCBs since 1912. The best material options should have a perfect balance between efficiency and price. Isola laminates for microwave frequency circuits provide steady and accurate dielectric, dielectric, and layer thickness management.

Rogers Advanced Materials for RF/Microwave Designs

Rogers is one of the oldest PCB laminate manufacturers because they created the first material for RT/droid in 1949. This material is currently the market leader in high-speed microwave PCB applications in the high-frequency PTFE family. PCB PTFE laminates need unique materials and systems to produce. Teflon is the most famous brand name for PTFE-based formulations.

A RF PCB

Rogers 5880 microwave laminate PCB

 

Source: Flickr

Arlon Electronic PCB Materials

Arlon specializes in the acrylate resin technique, a material that incorporates extraordinary TG, polyimide, and low-cost thermoset structures. The company based these resin alternatives on multiple substrates, such as non-plaited aramid and fabric crystal. These substrates are perfect for reliable, high-speed PCB microwave signals.

Taconic Advanced Dielectric Materials

Taconic is a global leader in PTFE products. The company primarily focuses on manufacturing thermally stable materials with a low dielectric constant for microwave and RF applications. Also, some of these laminates provide exceptional loss insertion capabilities with an ultra-low fiberglass percentage and standard refractive index on the cover.

A power amplifier PCB

A RF PCB

Panasonic MEGTRON 6

This laminate is a sophisticated PCB technology for induction motors used in high-frequency measurement equipment, data centers, IC testing systems, etc. Also, the material has low dielectric factors and dissipation, high thermal expansion, and low transmission losses.

Higher Dk Materials

If looking for laminates for power amplifiers and low noise amplifiers, you need materials with high Dk values. These can miniaturize circuit dimensions for a specific frequency range and impedance.

A power amplifier PCB

A power amplifier PCB

Source: Wikimedia Commons

The circuit wavelength also depends on the laminate material and frequency. Higher Dk values enable routing algorithms to operate at lower frequencies.

PA Materials

Susceptibility control and tight Dk are significant factors for laminates used in PA (Power Amplifier) circuits. The additional heat generated by these circuits also means thermal conductivity is a weighty factor. Other vital properties to look for are CTE (coefficient of thermal expansion), TCDk, and heat capacity.

An RF amplifier PCB

An RF amplifier PCB

Metal Material for Microwave PCB

Iron, copper, aluminum, and other metallic PCB materials are ideal for surface mounting and are more durable (mechanically). Pick the specific metal material based on the expected results.

A copper clad, tin-coated PCB

A copper-clad, tin-coated PCB

Source: Wikimedia Commons

FR-4 Material

FR-4 is a glass-reinforced laminate epoxy material. It is the most often used PCB material because it is waterproof, has high tensile strength, and provides outstanding weight.

PTFE (Teflon) for Microwave PCB

Teflon is a zero-resistance polymeric substance suitable for high-frequency, high-speed applications. The material is also flexible, lightweight, flame resistant, and stable in high temperatures.

Common RF & Microwave PCB Materials’ Dielectric and Material Properties

Common RF & Microwave PCB Materials’ Dielectric and Material Properties

Common RF & Microwave PCB Materials’ Dielectric and Material Properties

Common RF & Microwave PCB Materials’ Dielectric and Material Properties

 

How do RF and Microwave PCB Differ?

The most significant difference between the two is the radio frequency. Microwave PCBs fall under the category of over 2 GHz RF circuit boards. However, both are suitable for applications requiring transmission and receiving radio signals, specifically for dealing with networking signals.

Various RF circuit boards

Various RF circuit boards

Summary

In conclusion, there are several microwave circuit board materials, and each has different properties that suit specific applications. Considering the critical parameters described above, you should be able to pick the best material to use for your project. If you think we left something out or have any questions/comments, leave a message, and we'll get back to you asap.