RF PCB – Professional PCB fabrication and PCB Assembly Service Manufacturer

RF PCB Definition

The fastest expanding industry in PCB manufacturing has to be RF Printed Circuit Boards, or RF PCBs as it is more commonly called. The use of RF PCBs is only expected to increase given the general trend of the rise of wireless devices, IoT, smart phones, and more. But what do RF printed circuit boards actually do? Any board that runs at or above 100 MHz is typically referred to as an RF PCB, whereas anything that operates at or above 2 GHz is a microwave PCB.

Finding the best PCB manufacturer who can build RF PCBs to the necessary high-quality standards is crucial when dealing with them. More so considering that RF circuit boards are thought to be challenging to design due to problems with noise sensitivity and tighter impedance tolerance.

Our RF PCBs Capabilities:

To put it mildly, RF PCBs are complicated. This is due to a number of factors, including the necessity to control the heat within the board in order for it to withstand thermal loads. The distance between the characteristics also matters a lot. Additionally, you require specialist equipment like laser direct imaging and plasma etch machines. Below there are our RF PCBs capabilities:

Layer: 2-44 layers
Surface finish: immersion silver, immersion tin, OSP, ENIg, HASL (Lead-free).
Metal Core thickness: 58mm * 1010mm
Minimum track and gaps: 0.75mm / 0.075 mm
Characteristic impedance of a transmission line: Controlled impedance
Vias: Buried /Blind Vias. & Micro Vias Via In Pad with Fill Options (Copper Plug, Conductive, Non-Conductive)
Maximum Panel Size: 24″ x 30″
Drill aspect ratio: 15:1

Feature of RF (Radio Frequency) PCB

Fine pitch components can be easily placed, which is increasingly becoming necessary.
They are well suited for use in hot environments. It is impossible to overestimate their significance for applications that must operate in hot environments.
Due to the possibility of multilayer board stack-up, both performance and cost are maximized.
High Frequency signals can move more quickly and with less impedance because to it.

Why we can make high quality RF PCB for you?

The fact that intopcb has 20 years of experience producing and assembling premium RF PCBs is what sets us apart from the competition. By being current with technology, we are able to provide items that are at the top of their respective industries. While some of the processing for RF PCB can be done using conventional equipment, complicated designs call for specialist equipment. We are prepared to take on even the most complicated designs thanks to our Plasma Etch equipment. Our team of professionals can also direct you because they have the necessary industry knowledge. Therefore, you do not need to create the wheel from scratch.

The RF PCB stackup is created by our experts to maintain signal integrity. When it comes to RF PCB stackup design, some of the factors that they take into account are as follows:

Layer Arrangement : Ground planes and power can be spaced on adjacent layers of a multi-layered PCB stack up.
Decoupling: Thus, power integrity is guaranteed.
Isolation: By doing this, interference between different frequencies is prevented.

Additionally, proper consideration is given to the PCB’s material selection as well as the positioning of traces, planes, and component interconnections. Additionally, our professionals are aware that selecting the proper substrate material improves the performance of the RF PCBs. Thickness, Loss Tangent, Relative Permitivity, and other factors are some of those considered when making the decision.

It is essential that you choose an RF PCB manufacturer who is aware of these minute details that contribute to the smooth operation of the RF circuit board. Although quality is given a lot of care, quick turnaround times are also given a lot of attention. This ensures that your deadlines are never missed and that you have the advantage of a speedy time to market.

Additionally, our ability to accommodate both large production runs and prototype amounts makes us popular with our customers. All you have to do is contact our staff with your specific needs, and we’ll take care of the rest. We can provide you with unique quotations, RF printed circuit boards that are delivered in accordance with your demands, and support.

RF PCB material types:

Ceramic-filled PTFE material:

which have outstanding mechanical and electrical stability. Regardless of the dielectric constant (Dk) chosen, Rogers RO3000 series circuit materials offer consistent mechanical properties, enabling multi-layer board designs that use a variety of dielectric constant materials without experiencing warpage or reliability issues. As opposed to its hydrocarbon-based competitors, the Taconic RF family of products has a low dissipation factor and high thermal conductivity potential, which prevents oxidation, yellowing, and upward dielectric constant and dissipation factor drift.

Halogen Free Megtron 6 , Ultra-low Loss material

High-Density Interconnect (HDI) and high speed (over 3 GHz) architectures are perfect for MEGTRON 6, which has a low expansion ratio and a high glass transition temperature (Tg).

Woven Glass Reinforced PTFE material

It is made of incredibly thin, woven fiberglass, and is more dimensionally stable than PTFE composites reinforced with chopped fiber. Low dissipation factors in materials like those found in the Taconic TL family of products make them ideal for millimeter-wave antennas and 77 GHz radar applications.

Hydrocarbon ceramic material

As this low loss material provides easier use in circuit manufacturing and streamlined qualities over typical PTFE materials, it is used in microwave and millimeter-wave frequency designs. The Rogers RO4000 family of products have above-average thermal conductivity and a wide range of DK values (2.55–6.15). (.6-.8).

Filled PTFE (ceramic or random glass) material

High frequency circuit materials are favoured in space applications due to their low electrical loss, low moisture absorption, and minimal outgassing characteristics.

Thermoset microwave material

It combines a low copper-matched coefficient of thermal expansion, a low thermal coefficient of dielectric constant (Dk), and outstanding mechanical dependability. Great-frequency laminates made by Rogers TMM are perfect for strip-line and micro-strip applications requiring high reliability.

10 Factors to consider in RF PCB design

1. Material option

However, FR-4 (flame retardant level 4) and other materials frequently used in PCB fabrication are not the best options for high frequency RF applications due to the non-uniformity of the dielectric constant and a worse tangent angle. FR-4 is also relatively inexpensive. Specific materials, such as FEP, PTFE, ceramic, hydrocarbons, and several kinds of glass fiber, are employed for RF PCBs. The fluoropolymer family’s PFE and PTFE materials enhance the base material’s chemical resistance and feature anti-adhesion, smoothness, and exceptional heat resistance (they may survive temperatures as high as 200°C). The ideal option is PTFE with fiberglass, eventually woven glass fiber, if money is not an issue and quality is more essential than price.

The PTFE with ceramic coating is used because it is less expensive and the manufacturing process is simpler. A major manufacturer of dielectrics, laminates, and pre-pregs for high frequency RF applications is Rogers Advanced Connectivity Solutions (ACS), which supplies materials to several printed circuit board makers. Although more expensive, Rogers materials enable power losses to be reduced by up to 50%, ensuring great performance even over 20GHz and a low dielectric constant value that is stable and reproducible as the frequency varies. The most normal strategy is to use various materials that satisfy the requirements for electrical performance, thermal characteristics, and cost because RF PCBs are frequently multi-layered.

2. Transmission

Transmission lines (such as microstrip, stripline, coplanar waveguide, or others) are needed for RF PCBs in order to prevent power losses and guarantee signal integrity. The characteristic impedance, which typically has values between 50 and 75, is determined by the width of the trace, the layer thickness, and the kind of dielectric in microstrip transmission lines (Figure 1). Striplines are utilized on the inner layers, and microstrips are used on the outer layers. On the other hand, coplanar waveguides (grounded) offer the best level of isolation, particularly when RF signals intersect relatively close traces.

3. Impedance

A frequent strategy employed by designers is to select a standard impedance value (usually 50 ohms), so limiting their selection to RF components (filters, antennas, and amplifiers) with this particular impedance. The 50 ohm value has the benefit of being very common and makes impedance matching easier, enabling each PCB trace to be given the proper width.

4. Inductance

On the other hand, inductance should be maintained as low as possible because it can significantly affect the design of an RF PCB. This is accomplished by using several through holes, ground planes that are appropriately large and clear of gaps or discontinuities, and suitable ground connections to each RF component. High frequency components and traces need to be placed close to ground planes.

5. Routing

The curvature and angles that are present on a trace are subject to the first rule. It is ideal to generate an arc with a radius of curvature that is at least three times the trace width when a transmission line needs to change direction due to routing requirements. As a result, the characteristic impedance is guaranteed to remain constant throughout the curved segment. If this isn’t possible, draw an angle while keeping in mind that right angles must be replaced by two 45° angles.

In order to reduce the resulting variance in inductance, it is advised to install at least two via holes for each crossing when a transmission line must pass through two or more layers. In fact, utilizing the greatest diameter value feasible with the trace width for the holes, a via pair can cut the inductance fluctuation by 50%. Particularly if they are intersected by sensitive signals, the traces connecting the RF components must be kept as short, appropriately spaced apart, and organized orthogonally on the neighboring layers.

The multilayer structure with four layers is the greatest option for the stackup. The results are far better and are simple to duplicate, even though the cost is more than a double layer method. High frequencies cannot sustain discontinuities in the ground planes, hence continuous ground planes must be introduced beneath the RF signal traces.

6. Insulation

It’s important to pay close attention to prevent harmful couplings between the signals. The RF transmission lines shouldn’t run parallel for extended periods of time and should be kept as far apart from other traces as feasible (especially if they are crossed by high-speed signals like HDMI, Ethernet, USB, clock, differential signals, etc.). In reality, as the gap between them shrinks and the distance traveled in the parallel direction grows, the coupling between parallel microstrips grows. Traces carrying high-power signals ought to be segregated from other circuit components in a similar manner. The grounded coplanar waveguides can be used to get a superb insulation value.

In order to prevent coupling phenomena, high-speed signal traces should be routed on a distinct layer than RF signal traces. Additionally, the power supply lines should be routed on specific layers with the proper decoupling and bypass capacitors.

7. Ground planes

The power pins should be in close proximity to the appropriate value bypass capacitors, which can be arranged either singly or in a star pattern. A decoupling capacitor with a higher capacity (a few tens of micro Farads) is positioned in the center of the star arrangement, which is particularly helpful for components with many power pins. Other capacitors with a smaller capacity are positioned close to each branch. Long return pathways to the ground are avoided by the star configuration, which lowers parasitic inductances and prevents the emergence of unintended feedback loops. Given that the capacitor’s self-resonance frequency (SRF) rises above a certain point and takes on inductive properties, the decoupling effect is negated, it is important to pay close attention to this value.

8. capacitor

9. Via design

As much as feasible, RF traces should be free of vias. Specific through sizes and lengths must be followed if these can’t be avoided. A through causes a circuit board’s parasitic capacitance. This capacitance affects the high-frequency operation of radio-frequency boards. Therefore, it’s crucial to build vias with the following principles in mind to minimize interference at these frequencies:

Increase the number of parallel vias to lower parasitic capacitance.
A dedicated via is required for each of a component’s pins or pads. wherever possible, use stitching to implement ground plane. As a result, the current’s ground return path is shortened.
Reduce the use of vias for RF trace routing between layers.
Use as many vias as the design permits to connect the inner layer planes with the top layer ground plane. These vias need to be positioned no farther than 1/20th of the signal wavelength away.

10. Power supply

When it comes to radio-frequency boards, noise reduction is absolutely essential. These boards become particularly sensitive to the effects of noise at the high operating frequencies. As a result, all techniques are used to reduce noise. Power supply decoupling is one such technique.