What is a High Frequency PCB
PCBs are an integral aspect of electronics. In this article, we will discuss about High frequency PCBs.
For their wide range of features and properties, high-frequency PCBs are one of the most widely used boards in the engineering world.
High frequency PCB boards are needed when there is a need for signal communication between two objects, such as satellites, and telecommunications.
What is a High Frequency PCB?
High Frequency PCB is a type of PCB which is widely used in applications that involves special signal transmission between objects, such as mobile, microwave, radio frequency and high speed design applications.
It is available in the frequency range of 500MHz to 2GHz and hence is an ideal choice for above mentioned applications.
Properties of High Frequency PCB
High frequency PCB offer a wide range of properties. Such as :
- Low and stable dielectric constant: Dielectric constant is the ability of material to store energy in the electric field. The dielectric constant of a high frequency PCB is lower and stable. The lower dielectric constant leads to higher rate of frequency transmission. This also helps to ensure less signal delay.
- Chemical resistance: High frequency PCBs can withstand chemical attacks if exposed to one. Due to this property, these circuit boards are less likely to corrode.
- Dissipation factor: High frequency PCBs have a low dissipation factor that falls between 0.0019 and 0.025. This value helps to ensure that the signal transmission rate is not affected. It also ensures improved signal transmission and minimum signal loss.
- Low dimensional stability: High frequency PCBs have low dimensional stability. These PCBs maintain their size irrespective of the temperature they are exposed to which means their size remains the same even though they are exposed to heat.
- Low moisture absorption: High Frequency PCBs have a low rate of water absorption. It doesn’t absorb moisture and therefore can withstand a humid environment.
High Frequency PCB Applications
High frequency PCBs are used in many products and across many industries. These boards are specially fabricated to meet the requirements of high temperature applications. They are used in applications such as :
- Advanced communication system: These boards are used in the communication systems. They are commonly used in filtering devices, amplifiers, booster stations, and receivers. (Cellphones, Telecommunications)
- Military industry: High frequency PCB materials are used in the production of ammunition and firearms.
- Radar systems: These PCBs play a vital role especially in the marine and aviation industries. Radar systems prevent ships from obstacles like icebergs in marine application. The radar system guides aircraft to prevents accidents.
- Medical systems: These boards are used in the manufacturing of medical electronics like monitoring and diagnostic devices.
- High-density interconnect and high-speed design applications
Materials Used for High Frequency PCBs
Special materials are required to achieve the high frequency provided by this type of PCB.
Most of the professionals prefer rogers dielectric material as it is less expensive, has low dielectric constant and dissipation factor value, reduced signal loss and appears to be suitable for fabrication and prototyping applications.
Another common material that is used in the manufacturing process of the high frequency PCB, is Teflon, which comes with a frequency of 5GHz.
FR4 can be used in many applications requiring 1GHz to 10GHz frequency. But these FR4 based products have some drawbacks and limitations. For example, they fail badly when high frequency is required for the signal transmission.
Teflon, and flex circuits are the best options when it comes to dielectric constant, dissipation factor, water absorption, and survivability in the environment, but these are more expensive than FR4.
If your project requires a frequency above 10GHz with higher quality and stable signal, newer generation substrates like Teflon, and Flex substrates are your best option since they are far superior to traditional FR-4 material.
Following are some materials that can be used for high frequency:
- Rogers 4350B HF
- Rogers RO3010
- Rogers RO3003
- Taconic RF-35 Ceramic
- Taconic TLX
- ISOLA IS620 E-fibre glass
- ARLON 85N
Prior Considerations
High frequency PCBs come with much tighter impedance tolerance as compared to conventional circuit boards because they are more vulnerable to noise. However, proper bend radius and accurate ground plans on impedance traces can help you design a product that can work in an effective way.
The manufacturer can design a final product that meets the client’s needs and expectations by considering certain parameters such as coefficient of thermal expansion, dielectric constant, dissipation factor, temperature coefficient, thermal coefficient, and quality of the material used.
Ground plane is also an important part in high speed design applications, as it not only retains the quality of the signal but also helps in reducing EMI emissions. It works nicely by providing controlled impedance traces that resonate with load and electrical source. It plays an important role in keep the signal connected with their return path.
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