Introduction
Traditionally, manufacturers have been making PCBs or printed circuit boards of materials that offer resistance to heat and are, therefore, less expensive to produce. However, not all applications are the same, and some equipment, while not being subject to extreme temperatures, may have to work at RF or radio frequencies. Printed circuit boards, meant for RF operations, are a better option. According to eminent PCB manufacturer PCB Trace Technologies Inc., at the extreme performance conditions demanded by RF, specialized materials such as Rogers are necessary to deliver the best functionality from PCBs.
What is FR-4?
FR-4 is the traditional material that is the basis for most PCBs and is an acronym for Flame Retardant Level 4. Being a composite material made of epoxy and glass fiber, manufacturers shape it in the form of sheets and laminate it with copper foil on one or both sides. FR-4 provides an excellent value for its function and is more than sufficient for regular applications at low to medium frequencies.
However, some applications such as microwaves, mobiles, telecommunication, and others require PCBs to function at higher than normal frequencies. As the operating signal frequency increases, losses in FR-4 boards also increase, resulting in a drastic reduction in signal integrity.
This is the main reason for using better materials for PCBs that will operate at higher frequencies. The most popular is the Rogers PCB material that the Rogers company offers, and is eminently suitable for handling higher frequencies.

The Rogers PCB Material
Unlike FR-4, the Rogers substrate materials offer different compositions. Some of them use a ceramic base rather than glass. Various compositions are available, such as woven glass reinforced with hydrocarbons, and they offer electrical performance very close to that of PTFE. The Rogers PCB material offers significant advantages over FR-4, such as:
- Better signal integrity due to low electrical signal losses
- Lower dielectric loss
- Lower outgassing
- Better thermal conductivity
- Wider dielectric constant
- Better impedance control
- Cost-effective
Types of Rogers PCB Material
Rogers offers various types of materials for PCBs for different applications. Some of these are:
Rogers 3003
Rogers 3003 offers an exceptionally stable dielectric constant over a large range of frequencies and temperatures. This material is suitable for wireless operations at 5G, ADAS, and automotive radar applications, especially those operating at 77 GHz.
Rogers 4350B
Rogers 4350B offers tighter control on the dielectric constant, thereby maintaining a low-loss performance. Although requiring similar processing as regular FR-4, Rogers 4350B is available at a substantially lower cost compared to regular microwave laminates. Suitable for high-power RF designs, this material is rated for UL 94 V-O.
Rogers RT/Duroid 6002
Rogers RT/Duroid 6002 is a special PCB material exhibiting very low loss because of a very low dielectric constant. Presenting excellent mechanical and electrical properties, this material is optimally suitable for multi-layered board designs for microwave applications.
Rogers 4534
Those requiring an optimization between cost and performance can choose Rogers 4534. This material has a glass-reinforced composition filled with ceramic and is suitable for RF applications such as antennas. Offering low-loss performance, well-controlled dielectric constant, and a passive response to
inter-modulation signals, Rogers 4534 is suitable for applications such as mobile infrastructure and microstrip antennas. The material is suitable for high-temperature, lead-free solder reflow processing.
Rogers RT/Duroid 5880
Presenting low dielectric loss and a low dielectric constant, the Rogers RT/Duroid 5880 PCB material is the most suitable for broadband/high-frequency applications. With randomly oriented microfibers that reinforce the PTFE composites, this material maintains a uniform dielectric constant.
Rogers 4003C
Rogers 4003C offers low loss while maintaining tight control of the dielectric constant. This is possible because the laminate uses two styles of glass fabric, namely 1674 and 1080. While requiring similar processing as regular FR-4, Rogers 4003C is available at a substantially lower cost compared to regular
microwave laminates. Unlike PTFE-based microwave materials, the Rogers 4003C PCB material does not require any special treatments or handling procedures for through holes.
Comparison Between FR-4 and Rogers Material
Frequency of Operations
The major difference between regular boards made of FR-4 and those with Rogers material is in their application. PCBs made of FR-4 can operate properly only when the frequency of operations is within a certain range. On the other hand, PCBs made of the Rogers material can perform over a much larger range of frequencies. For instance, while FR-4 PCBs can hardly reach 10 MHz, Rogers PCBs can operate very well in applications extending well beyond 500 MHz.
Material Hardness
There is a substantial difference in material hardness between FR-4 and Rogers material. FR-4 is mainly epoxy resin and quite hard. On the other hand, Roger’s material, being hydrocarbon, is comparatively softer.
Processing Technology
Although Rogers materials are meant for high-frequency operation, they are different from PTFE microwave PCB materials. Roger’s series of materials does not require any special treatment, such as special treatment for through-hole processing, and no extra technological processes are necessary.
The FR-4 material is epoxy glass cloth laminate, which offers stable electrical insulation, a smooth surface, good flatness, and no pitting. It is suitable for products requiring good electrical insulation. This material is also suitable for use as backing boards for PCB drilling, FPC stiffeners, planetary gears, test plates, motor insulators, and many more.
Cost
Cost is an important factor for electronic equipment. Customers look for manufacturers offering PCBs with the best and most economical performance. Although making boards with FR-4 can save costs, this material is suitable for products operating at low frequencies and moderate temperature settings. On the other hand, for applications requiring high-speed operation or high temperatures, using Rogers material would be more suitable, even if it is more expensive.
Impedance Stability
The maximum dielectric constant of FR-4 material is 4.5. In comparison, Roger’s material has a dielectric constant of about 2.2-12.85. The higher dielectric constant of Rogers material contributes to high impedance stability.
Thermal Capability
For applications operating at high speeds, the PCB must also have better thermal capacity to prevent it from overheating and causing operational problems. Rogers PCBs, with their higher thermal capabilities, perform better than FR-4 at high temperatures and for high-speed applications.
Signal Integrity
Rogers PCB material has a dissipation factor of 0.004%. In comparison, the dissipation factor for FR-4 material is 0.02%. The significantly lower dissipation factor of the Rogers PCB material contributes to a substantially lower signal loss, thereby improving the signal integrity.
Moisture Absorption
Most regular PCB materials absorb moisture typically between 0.1 % and 0.2 % from the ambient. Absorption of moisture reduces the thermal and electrical properties of the material and its efficiency.
Compared to FR-4, Rogers PCB materials exhibit a lower value of moisture absorption, typically ranging from 0.02 % to 0.08 %. This makes the Rogers PCB materials much more suitable for defense and aerospace applications that operate in extreme environments.
Choosing the Right PCB Material
The designer may have to consider the following points when choosing the right PCB material between FR-4 and Rogers:
Impedance Control
As stated earlier, FR-4 material is good enough only for applications with low signal frequencies. This is because, as the signal frequency increases, so do the losses in the FR-4 material, leading to poor impedance control and deteriorating signal integrity.
Using the Rogers material, on the other hand, allows tolerance on dielectric constant to remain at ±2% or lower. This offers very low insertion and transmission loss for Rogers material, about 50-80% lower than traditional FR-4 material.
Cost-to-Performance Ratio
PCB cost is an important factor for customers to remain within budgetary constraints. Although Rogers PCB materials are more expensive as compared to regular FR-4 materials, their overall cost-to-performance ratio is much lower, as Rogers PCB materials offer significantly better performance at high-frequencies with their relatively lower losses.
Sometimes, designers offset the higher cost of Rogers material by using them in layers immediately below the top and bottom layers (these carry the high-frequency signals), while using FR-4 for lamination in the other layers. This option is mixed stack-up in PCB manufacturing.
Frequency of Signals
For signal frequencies over 500 MHz, Rogers material can provide substantially higher performance with its stricter impedance control. Moreover, in comparison to FR-4 material, the Rogers material offers a much lower dielectric loss along with a very stable dielectric constant over a wide frequency range. For antenna and radar applications that use high-frequency signals, Rogers material offers very low insertion loss.
CTE or Coefficient of Thermal Expansion
In comparison with FR-4 material, the Rogers PCB material offers very low and stable CTE. This is helpful when the PCB must undergo multiple thermal cycles such as during soldering for maintaining high dimensional stability.
Tg or Glass Transition Temperature
Regular FR-4 material has a Tg of 135-150. This is the temperature beyond which the substrate starts to become plastic. Rogers PCB material, on the other hand, offers a Tg above 200, allowing it to be more stable at higher
temperatures.
Conclusion
In this article, we, at PCB Trace Technologies Inc., have presented a comprehensive comparison between regular FR-4 and Rogers PCB materials, and how to select the most optimum material for an application. The Rogers PCB materials have the advantage of not requiring any special process for fabricating PCBs. In suitable cases, designers can offset the higher cost of Rogers material by using it only for layers that handle high frequencies and using FR-4 for others.
FAQs
What is Rogers PCB material?
Rogers PCB materials are superior materials in comparison to regular FR-4 and manufactured by Rogers Corporation. Rogers PCB materials are more suitable for high-frequency applications.
What is the major difference between FR-4 and Rogers material?
They differ majorly in their composition. FR-4 uses woven glass fiber reinforced with epoxy resin. While Rogers material is hydrocarbon based and uses specialized materials.
At what frequencies should I start using Rogers materials?
In general, Rogers material is best suited for operations above microwave frequencies. However, Rogers Corporation offers a large variety of Rogers materials suitable for different operational frequencies.
Is the dielectric constant of Rogers material lower or greater than FR-4?
The dielectric constant of some Rogers PCB materials is much higher in comparison to that for regular FR-4 materials. The maximum dielectric constant of FR-4 material is 4.5. In comparison, Rogers materials exhibit a dielectric constant ranging from 2.2 to 12.85.
Can I route traces between Rogers and FR-4 layers?
When routing groups of signals of similar frequencies, it is preferable to assign a whole layer to a specific material type. For instance, route high-frequency signals within a few layers using Rogers material. Use FR-4 material for the other layers.