High-frequency PCB – Digital Download Store

High Frequency PCB and High Speed PCB Manufacturing Service

High-frequency PCB is a special PCB with a frequency range of 500MHz to 2GHz, widely used in applications involving specialr signal transmission between objects.

A special PCB

High Frequency PCB

Printed Circuit Boards are very high in demand because they make the circuit compact durable and ensure optimum performance with low errors and malfunctions. Nowadays, there are different types of PCBs available that can be used anywhere, even in a small flashlight or a large spacecraft. One of the special kinds of PCB is High-frequency PCB, which is used for special purposes. It has made a lot of things easier that were not possible to do using a normal PCB.

What is High-Frequency PCB?

A high-frequency PCB refers to a special PCB that has a frequency range of 500MHz to 2GHz. This is a very high-frequency range that is not achievable in standard PCBs, which is why these PCBs are used for particular purposes where high-frequency signals are transmitted. High-frequency PCB is a circuit board produced on microwave substrate copper clad board using part of ordinary rigid circuit board manufacturing methods or using unique processing methods. Due to high frequency, communication and signal transmission are carried out at a faster rate. High-frequency PCBs’ primary use is in wireless communications, including satellites, telecommunication, and radar systems.

Why High-Frequency PCB?

When it comes to transmitting a signal at a higher frequency, there are many chances of losses, delays, and distortion in the signal. Thus, if we use a standard PCB for high-speed or high-frequency purposes, the results will not be optimum. The signals might get lost, or there could be huge losses after receiving the signal.

Furthermore, we cannot eliminate the use of high-frequency signals in the circuit because it’s the future. Nowadays, wireless transmission is widespread, and the best example is a Wi-Fi router working at your home. Some complex components and switches need signals faster, so the signal has a higher frequency. In simple words, high-frequency applications are increasing day by day because of the advantages that it offers. Thus, there is no choice to go for low-frequency signals to avoid the problem.

The only solution to these problems is the high-frequency PCB. A high-frequency is made of unique materials and has some specific features that allow it to transfer high-frequency signals with minimal loss. The High-frequency PCB is ideal for high-speed applications.

Materials for High-Frequency PCB

The materials that are used for high-frequency PCBs have unique qualities. If the material you have chosen is correct, it will offer the optimum results. Before you select any material, you need to go through some specifications to know whether the material is suitable for the application or not.

The important factors that you need to look at are,

1. Dielectric Constant(DK)
2. Dissipation Factor(DF)
3. Coefficient of Thermal Expansion
4. Moisture Absorption

Dielectric Constant(DK)

Dielectric constant (Dk) is also known as Relative Permittivity (Er). It is a crucial factor that should be considered while selecting the material for PCB, especially in high-frequency PCBs. When you read the value of dielectric contact of the material, it seems constant, and many people consider it a continuous value. In reality, it is a variable quantity that varies with the frequency. Typically, the value of the dielectric contact decreases with the increase in frequency. The dielectric constant of a high-frequency PCB should be small to prevent delays in signal transmission. Moreover, the constant value should remain stable for a wide range of frequencies to deliver the desired results.

Dissipation Factor(DF)

Dissipation factor (Df) is also termed as dielectric loss tangent. It is a significant factor in high-speed designs. It is the measure of signal loss during transmission. A low or no loss is desired in every case, including high-frequency applications. Df's value should be lower so that it cannot attenuate the signal or create a significant loss. The lower the dissipation factor, the better it is. At higher frequencies, the loss is higher because the dielectric material absorbs more energy. Thus, if the high-frequency PCB materials are not picked wisely, there will be a loss of signals.

Coefficient of Thermal Expansion

While selecting the material for a high-frequency PCB, thermal expansion's coefficient is an essential factor to look at. Above the base layer of the PCB, there is a copper layer, which is responsible for the conduction. If anything happens to that layer, the PCB will not work or provide the desired results. The coefficient is analyzed wisely, and the material with the coefficient of a thermal expansion near to copper is selected. This ensures the expansion and contraction of the base material with the top copper layer. Otherwise, due to a massive difference in both the materials' coefficients, there can be a discontinuity in the electric connection. The top copper layer stays intact in a high-frequency PCB irrespective of the hot or cold temperature. Thus, the PCB can last for a long time and provide the desired results.

Dielectric Constant(DK)

The PCB material should not absorb too much moisture because it can increase the losses and delays in the transmission. If the humidity is absorbed too much, the dielectric constant and loss tangent is also affected.

Some Common High-frequency PCB Materials

By considering the above factors, some common materials that are used for high-frequency PCBs. Some of them are:

. High Performing FR-4
. PTFE
. Ceramic-filled PTFE
. Ceramic-fille Hydrocarbon
. E-fibre glas

Teflon is one of the best and most widely used materials for high-frequency PCBs. It can offer stable and optimum results. But it is more expensive as compared to FR-4. There are some popular and trusted manufacturers of high-frequency PCB materials; some of them are:

. Rogers (RO03001, RO03003, RO3010, RO4350B, RO4450B, RO4350 HF, RO4003)

Isola IS620 E-fibre glass
Isola FR408, FR 408 HR
Isola IS 415
Arlon 85N
Taconic RF-35 Ceramic
Taconic TLX
GIL Taconic
Nelco N4000-12/N4000-12SI
Nelco N4000-13EP/N4000-13EPSI
Nelco N8000
Hitachi LX-67Y, FX II
Getek
Panasonic Megtron +
Panasonic R2125
Panasonic Megtron VI

Double Sided PCB Board Prototype

Double Sided PCB Prototype Fabrication

As we all know, the double-sided circuit board is a very important PCB in the printed circuit board. The market has double-sided metal-based PCB, Hi-Tg heavy copper circuit board, double-sided flexible circuit board, and double-sided high-frequency circuit board.

The most common surface treatment used in manufacturing double-sided PCB board prototypes is OSP, immersion gold, lead-free tin spraying, etc.

The double-sided PCB with a lead-free tin spraying process has the advantages of beautiful appearance, white pads, easy-to-tin pads, ease-to-solder, and low price.

The Cheapest and The Most Expensive High-Frequency PCB Material

The laminate cost of FR4, PPO, and Teflon, FR4 is the cheapest one, while Teflon is the most expensive one. In terms of DK, DF, water absorption, and frequency feature, Teflon is the best. When product applications require frequency above 10GHz, only can we choose Teflon PCB substrate to manufacture. Obviously, Teflon’s performance is far better than other substrates; however, the Teflon substrate has the disadvantage of high cost and large heat-resisting property. To improve PTFE stiffness and heat-resisting property function, many SiO2 or fiberglass as the filling material. On the other hand, due to molecule inertia of PTFE material, it is not easy to combine with copper foil; thus, it needs to do the special surface treatment on the combination side. Combined surface treatment normally uses chemical etching on PTFE surface or plasma etching to plus surface roughness or add one adhesive film between PTFE and copper foil. Still, these may influence dielectric performance.

We manufacture high-frequency PCBs with frequencies typically in the range from 500MHz to 2GHz. The following table shows some of our common-use materials for High-Frequency PCBs manufacturing.

Material	Dielectric Constant
RO4350B	3.48±0.05@10 GHz
RO4003C	3.38±@10 GHz
Ro3003	3.00±0.04@10 GHz
Ro3010	10.2±0.03@10 GHz
RT5880	2.20±0.02@10 GHz

Several common high frequency circuit board material parameters

Material for high frequency boards
	°C	ppm/°C	@10GHz	KV/mm	MΩ	W/m*K	@10GHz	°C	N/mm
Rogers 4350B HF material	280°	32	3,5	31	5,7 x 10^9	0,69	0,0037	390°	0,9
ISOLA IS620 E-fibre glas	220°	55	4,5*	–	2,8 x 10^6	–	0,0080*	–	1,2
Taconic RF-35 Ceramic	315°	64	3,5**	–	1,5 x 10^8	0,24	0,0018**	–	1,8
Taconic TLX PTFE	–	135	2,5	–	1 x 10^7	0,19	0,0019	–	2,1
Taconic TLC PTFE	–	70	3,2	–	1 x 10^7	0,24	–	–	2,1
Rogers RO3001 Bonding Film for PTFE	160°	–	2,3	98	1 x 10^9	0,22	0,0030	–	2,1
Rogers RO3003 PTFE ceramic-filled	–	25	3,0	–	1 x 10^7	0,50	0,0013	500°	2,2
Rogers RO3006 PTFE ceramic-filled	–	24	6,2	–	1 x 10^5	0,79	0,0020	500°	1,2
Rogers RO3010 PTFE ceramic-filled	–	16	10	–	1 x 10^5	0,95	0,0022	500°	1,6
ARLON 85N Polyimide HTg	250°	55	4,2*	57	1,6 x 10^9	0,20	0,0100*	387°	1,2

PCB Materials Suppliers

Properties of High-Frequency PCB

Reduced Signal Delay

The first and the most important property of high-frequency PCB is that it reduces the delay of signals. The material used to make the PCB has a very low dielectric constant (DK), which is why it works better for high frequencies. There are minimal delays and losses in the signals. The impedance remains in control.

No Discontinuity in Copper Layer

No matter the temperature, the copper layer at the top of the PCB remains functional as it is supposed to be. It is because the coefficient of thermal expansion of copper is nearly equal to the base material, so they expand and contract together. Thus, there won’t be any discontinuity in the copper layer.

High Glass Transition Temperature

The glass transition temperature (Tg) of a high-frequency PCB is high, which means it can withstand high temperatures. It remains stable for a wide range of temperatures.

Minimal Attenuation

High-frequency PCB offers minimal attenuation of the signal. The reason behind this is the low dissipation factor (Df) of the base material. Due to minimal attenuation, the signal received at the receiver side is similar to the transmitter side. There is almost no decrease in the amplitude of the signal.

Low Moisture

The materials used for high-frequency boards absorb very little moisture. Thus, the high-frequency signals are not affected by humidity. In contrast, standard PCBs can absorb moisture 25 times more than the high-frequency boards.

Applications of High-Frequency PCB

Telecommunication Systems

Telecommunications systems require a high-frequency signal transfer, which is the reason the devices contain a high-frequency PCB. The transmission of the signal in telecommunication is possible because of high-frequency, and any loss or attenuation in the signal can be problematic. Thus, a special high-frequency board is necessary.

Radars

Radars also have an antenna that is responsible for receiving a high-frequency signal without wires. It is only achieved using the high-frequency PCB.

Satellites

Satellites also require high-frequency communication. High-frequency PCBs are widely used in satellites.

Wireless Controlled Devices

We use several wireless devices at our homes and other places. This includes Wi-Fi routers, remote controllers, cell phones, GPS receivers, and RF IDs. Thus, high-frequency PCB is also common in our daily life.

Speed Switching

For high-speed switching, a higher frequency is required. For instance, if you are using a high-speed switching transistor, you need a high-speed frequency signal. Such a signal can only be transmitted using high-frequency PCBs. High-speed switching is common in power devices and solar converters/inverters.

Medical Machinery

Many modern medical types of machinery use high frequencies, including the ultrasound machine, X-ray, and MRI scanners.

Military Applications

Military applications also require high-frequency PCB for communications in missile operation and other warfare machines that require wireless communication.

Factors influencing a high frequency PCB Design

Some of the factors needed to design high frequency PCB are mentioned below:

The selection of PCB material for high-speed digital circuits is influenced by several factors. The high frequency PCB must offer following features apart from a good structural build-up. Impedance controlled multilayers
Sandwich buildup for material combinations
Controlled production line
Signal loss tolerance
Heat sinking ability
Operating temperature(temperature expansion, stability over a temperature range)
Production cost

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High Frequency PCB and High Speed PCB Manufacturing Service

A special PCB