RF/Microwave/High Frequency PCB Design Guidelines & RF / low loss PCB Material Comparison

Most products today require special attention to signal intergrity. Hemeixin offers customers a large variety of base materials to cover their needs in the high speed/low loss arena. In addition, we can assist our customers with various advanced high frequency measurement techniques to verify compliance to specifications.

We feature a dedicated signal integrity lab and a corporate signal integrity engineers.

RF PCB

In order to meet increasing demands for Microwave & RF Printed Circuit Boards for our customers all around the world, we have increased our investment over the last few years so that we have become a world-class manufacturer of PCBs using high frequency laminates.

The definition of RF and microwave PCBs is that they contain components that carry RF or microwave signals. These signals vary in frequency from, 50MHz to above 2 GHz, and these frequencies define the differences in components between RF and microwave PCBs and other PCB types.

These applications typically require laminates with specialized electrical, thermal, mechanical, or other performance characteristics that exceed those of traditional standard FR-4 materials. With our many years of experience with PTFE-based microwave laminate, we understand the high reliability and tight tolerance requirements of most applications.

High frequencies require high precision. And extensive expertise. In cooperation with our customers from the automotive and telecommunications industries, we at Hemeixin have developed to become one of the leading manufacturers of printed circuit boards for high-frequency applications in the range from 24 to 77 GHz.

What materials are used for high-frequency PCBs?

When it comes to the cost of FR4, PPO, and Teflon laminates, FR4 is the least expensive, while Teflon is the most costly. Teflon is the best in terms of DK, DF, water absorption, and frequency characteristics. Only Teflon PCB substrate can be used to produce products that require frequencies more than 10GHz. Teflon’s performance is significantly superior to that of other substrates, yet, Teflon has the disadvantage of great heat resistance.

PTFE or polytetrafluoroethylene is a synthetic thermoplastic fluoropolymer and is the second most commonly used PCB laminate material. It offers consistent dielectric properties at a higher coefficient expansion than standard FR4. These two laminates, FR4 and PTFE, quickly became the 2 options for all PCBs coming to market.

The PTFE is commonly used in a higher-speed, higher-frequency technology. One example is microwave technology: the PTFE has a higher coefficient of thermal expansion (CTE). This makes it a good choice where the PCB could see changes in temperature.

The base PTFE had its challenges to overcome with the addition of woven glass assisted in the stability or size changes of the laminate due to fluctuating temperature. Later, ceramic fillers and microfiber glass were introduced to increase the dielectric constant (Dk) values. PTFE with additives such as glass or ceramic improved and stabilize the DK, allowing for a better signal between parts to be had.

The additional cost for this type of material is significant from FR4. It is more costly to produce and typically the quantity of PCBs is smaller for the purchase. This, compiled with the part’s physical size, is also typically smaller in the X,Y, driving up the cost to manufacture.

The supplier imposes a MOQ on laminate purchase to multiple sheets, leaving stock on the shelf for an undetermined amount of time. This cost is passed on to the consumer in the piece price or laminate cost so as to encourage consumption and ease the pain of purchasing and having stock for long periods of time. Introducing multiple parts on one panel has become more common to aid the customer in keeping costs down; we have seen 8 or 12 different PCBs on a single array for a one-time buy versus buying 5 pieces of 8 or 12 different parts in a single purchase each. This saves the customer on NRE passing as 1 instead of 8 or 12, but it also assists production on the consumption of panels where the physical size is small, so it is allowed.

When Do You Need an RF PCB Material?

This is a fair question and it relates to some important tasks in systems analysis. There are a few different considerations a designer should examine when qualifying an alternative PCB substrate material should be used. Here’s a short list of some dimensions you might look at when selecting an RF PCB substrate material.

• Loss tangent: This is the first major area that PCB designers will use to start comparing material options.
• Dielectric constant: Although this is sometimes misunderstood, and everyone tends to just go for low-Dk laminates, but high-Dk laminates can also have low loss tangent and other benefits.
• Thermal properties: There are multiple thermal properties, but the most important are probably glass transition temperature and CTE.
• Workability in fabrication: Designers leave this up to their fabricator at their own peril. It’s best to contact your fabricator regarding availability of materials, their ability to work the board, and availability of materials.
• Thickness: You can’t just choose any thickness you want, you’ll need to check with your fabricator on their preferred stackup. If you know which layer thicknesses they can support, you can usually get your design close enough to the fabricator’s specifications.
• Dispersion: I’ve put this at the bottom of the list as it tends to matter least for mmWave applications. The bandwidths in mmWave devices may be small enough that dispersion is negligible, but you should still check on this where possible.

Many years of experience in processing special high-frequency materials have made us the perfect partner for you and your RF PCB project.

We use special materials for achieving the high frequency operations of our HF PCBs. Depending on the range of signal speeds of the application, we use a variety of substrate materials that are the best suitable.

Ceramic-filled PTFE composites, which have exceptional electrical and mechanical stability. Rogers RO3000 series circuit materials have consistent mechanical properties, regardless of the dielectric constant (Dk) selected, which allows multi-layer board designs that use different dielectric constant materials without encountering war-page or reliability problems. The Taconic RF series of products has a low dissipation factor with high thermal conductivity possible so it will not oxidize, yellow, or show upward drift in dielectric constant and dissipation factor like its hydrocarbon-based competitors.

Ultra-low Loss, Highly Heat-Resistant, Halogen Free Megtron 6 circuit board material. With high glass transition temperature (Tg) and the low expansion ratio of hydrocarbon resin-based MEGTRON 6 - makes it ideal for High-Density Interconnect (HDI) and high speed (above 3 GHz) constructions.

Woven Glass Reinforced PTFE laminates are manufactured with very lightweight woven fiberglass and are more dimensionally stable than chopped fiber reinforced PTFE composites. Materials such as the Taconic TL family of products have a low dissipation factor, and this is perfect for radar applications designed at 77 GHz as well as other antennas in millimeter-wave frequencies.

Hydrocarbon ceramic laminates are used in microwave and millimeter-wave frequency designs as this low loss material offers easier use in circuit fabrication and streamlined properties over traditional PTFE materials. Rogers RO4000 series of products come in a wide range of DK values (2.55-6.15) and have above average thermal conductivity (.6-.8).

Filled PTFE (random glass or ceramic) composite laminates such as the Rogers RT/duroid® high frequency circuit materials have low electrical loss, low moisture absorption, and low outgassing properties that are preferred in space applications.

Thermoset microwave laminates combine low thermal coefficient of dielectric constant (Dk), a copper matched coefficient of thermal expansion and excellent mechanical reliability. Rogers TMM materials are high-frequency laminates ideal for high-reliability strip-line and micro-strip applications.

Benefits Of RF PCB

RF PCB boards come with a wide variety of benefits for MHz and GHz applications:

• It allows High Frequency signals to travel fast with less impedance.
• Since it is possible to have multilayer board stack-up, is makes for both, optimal performance and reduced costs.
• They lend themselves to seamless usage in high temperatures. For applications that have to work in high environmental temperatures, therefore, their importance cannot be overstated.
• It is easy to place fine pitch components, which is increasingly becoming the need of the hour.

RF PCB Board Applications

RF boards have a multitude of different applications, including wireless technologies, smart phones, sensors, robotics and security. With the advent of new technologies that are pushing the limits of electronics, the demand for RF boards is on the rise.

Finding a capable RF PCB manufacturer is critical to make sure the boards are fabricated to high quality standards and on-time. Our reputation speaks for itself. We pride ourselves on bringing the most demanding layout concepts to reality.

RF PCB Manufacturer

As high frequency PCB manufacturer, Hemeixin makes both rigid and flexible types of boards. Our high frequency PCBs offer faster signal flow for frequencies up to 100 GHz. Although numerous materials are available for high frequency operation, Hemeixin uses materials for HF PCBs that exhibit a few common features like low dielectric constant or Dk, low dissipation factor or Df, and low coefficient of thermal expansion or CTE. We use the materials for high frequency PCBs also for our boards using HDI technology. Industries using our high frequency PCBs include RF microwave, telecommunications, high speed communications, and more.

Benefits of Rogers PCB

• They are well suited for harsh environmental conditions.
• Rogers PCB show significantly less moisture absorption as well as improved thermal management.
• RO4000 material’s thermal co-efficient of expansion is akin to that of copper that offers dimensional stability.
• They are also known to display better impedance control.
• They are extremely cost-effective when it comes to circuit fabrication.
• They are known for lower di-electric loss, lower signal loss, as well as low cross-over.

What is Rogers PCB

RO4000 hydrocarbon ceramic laminates are designed to offer superior high frequency performance and low cost circuit fabrication. The result is a low loss material which can be fabricated using standard epoxy/glass (FR-4) processes offered at competitive prices.

The selection of laminates typically available to designers is signifi cantly reduced once operational frequencies increase to 500 MHz and above. RO4000 material possesses the properties needed by designers of RF microwave circuits and matching networks and controlled impedance transmission lines. Low dielectric loss allows RO4000 series material to be used in many applications where higher operating frequencies limit the use of conventional circuit board laminates. The temperature coeffi cient of dielectric constant is among the lowest of any circuit board material , and the dielectric constant is stable over a broad frequency range . For reduced insertion loss, LoPro® foil is available. This makes it an ideal substrate for broadband applications.

RO4000 material’s thermal coeffi cient of expansion (CTE) provides several key benefi ts to the circuit designer. The expansion coeffi cient of RO4000 material is similar to that of copper which allows the material to exhibit excellent dimensional stability, a property needed for mixed dielectric multi-layer boards constructions. The low Z-axis CTE of RO4000 laminates provides reliable plated through-hole quality, even in severe thermal shock applications. RO4000 series material has a Tg of >280°C (536°F) so its expansion characteristics remain stable over the entire range of circuit processing temperatures.

RO4000 series laminates can easily be fabricated into printed circuit boards using standard FR-4 circuit board processing techniques. Unlike PTFE based high performance materials, RO4000 series laminates do not require specialized via preparation processes such as sodium etch. This material is a rigid, thermoset laminate that is capable of being processed by automated handling systems and scrubbing equipment used for copper surface preparation.

RO4003C™ laminates are currently offered in various confi gurations utilizing both 1080 and 1674 glass fabric styles, with all confi gurations meeting the same laminate electrical performance specifi cation. Specifi cally designed as a drop-in replacement for the RO4003C™ material, RO4350B™ laminates utilize RoHS compliant fl ame-retardant technology for applications requiring UL 94V-0 certifi cation. These materials conform to the requirements of IPC- 4103.

What is RO4350B rogers PCB

RO4350B laminates provide tight control on dielectric constant (Dk) and maintain low loss while utilizing the same processing method as standard epoxy/glass. Available at a fraction of the cost of conventional microwave laminates, RO4350B laminates do not require the special through-hole treatments or handling procedures as PTFE based materials. These materials are UL 94 V-0 rated for active devices and high power RF designs.

Rogers RO4350B PCB including:

• Dk of 3.48 +/- 0.05
• Dissipation factor of 0.0037 at 10 GHz
• Low Z-axis coefficient of thermal expansion at 32 ppm/°C
• Processes like FR-4 at lower fabrication cost
• Competitively priced
• Excellent dimensional stability

What is RO4003C rogers PCB

Offered in various configurations, RO4003C laminates utilize both 1080 and 1674 glass fabric styles with all configurations meeting the same laminate electrical performance specification. RO4003C laminates provide tight control on dielectric constant (Dk) and low loss while utilizing the same processing method as standard epoxy/glass but at a fraction of the cost of conventional microwave laminates. Unlike PTFE based microwave materials, no special through-hole treatments or handling procedures are required.

RO4003C materials are non-brominated and are not UL 94 V-0 rated. For applications or designs requiring a UL 94 V-0 flame rating, RO4835™ and RO4350B™ laminates do meet this requirement.

Rogers RO4003C PCB including:

• Dk of 3.38 +/- 0.05
• Dissipation factor of 0.0027 at 10 GHz
• Low Z-axis coefficient of thermal expansion at 46 ppm/°C
• Ideal for multi-layer board (MLB) constructions
• Processes like FR-4 at lower fabrication cost
• Designed for performance sensitive, high volume applications
• Competitively priced

Rogers PCB Manufacturer

The use of high frequency rogers printed circuit board material is imperative when it comes to creating PCBs for critical applications that particularly need low signal loss as well as low dielectric loss. Such material is also the need of the hour when signal integrity and impedance matching are of utmost importance.

At Hemeixinpcb, we provide Rogers printed circuit boards, one of the well-known names, when it comes to Rogers PCB manufacturing:

• Dielectrics
• Laminates
• Prepregs

Their high-quality materials, are especially known for their ability to withstand harsh environmental conditions.

As a Rogers PCB Manufacturer, we are fully equipped to manufacture eponymous printed circuit boards created from material sourced from Rogers that is known for their durability and reliability. We provide high mix printed circuit boards, high frequency rogers PCB, RF rogers printed circuit boards, SMT rogers circuit boards, Rogers PCB prototype and more. The range of manufacturing printed circuit boards are reliable, efficient and high performance for any type of specialty applications.