Keywords: RF PCB

RF printed circuit boards are becoming an interesting, fast-developing niche market segment of the PCB manufacturing industry. They are also remarkably diverse and it is easy to get lost for a few hours trying to decide on which augmented reality option to pursue. Engineers are happy to discuss decisions for each phase of fabrication/assembly or the constraints, pitfalls, and possibilities in the process of building your RF PCB.

What is an RF Circuit Board?

By the PCB industry standards, an RF circuit board is defined as any high-frequency PCB that works above 100 MHz.

For the radio frequency class where the rate is more than 2 GHz, we are talking of Microwave PCB.

What is a Microwave PCB?

The primary distinction between RF circuit boards and Microwave PCBs is in the radio frequency within which they function. These are Microwave PCBs are any RF circuit board that operates beyond 2GHz. RF circuit boards and Microwave PCBs are widely used with communication signals in any system needing reception and transmission of radio signals.

Microwave Printed Circuit Board and Radio Frequency Circuits:

Typical Difficulties and Their Remedies

For instant RF circuit boards and Microwave PCBs are much more challenging to design than the normal layout of PCBs. This is in view of synonymous issues that could occur in reception or transmission of the radio signals. Several of the most significant issues are matters of noise sensitivity and tighter impedance tolerances.

Radio and microwave signals are much more sensitive to noise than ordinary circuit boards, and at the same time have much more stringent tolerances for impedance. Moreover, these problems can be solved with the help of ground plans and presenting a generous bend radius at the impedance-controlled traces. These solutions will in the end help the RF/Microwave PCB to realize its best performance.

RF Board Applications

RF boards have very versatile application prospects in such fields as wireless technologies, communication, smartphones, sensors, robotics, and security. RF boards are in demand now, especially given that new innovations are emerging in electronics today to address and meet the client’s needs.

Selecting a qualified RF PCB manufacturer is important in order to ensure that the boards are manufactured to accurate specifications and within the right time. Speaking about the reputation of our company – it is virtually unblemished. The company boasts of the fact that we are able to provide for the layout of some of the most challenging concepts today.

RF MATERIALS BY APPLICATION

We are also able to assist with every aspect of board costs down to manufacturing recommendations for a sleek, fifty ply board.

It is by no means easy to manufacture RF PCB but there is no magic involved in the process.

To this end, the following are several factors which engineers need to have into consideration if they have to undertake an RF manufacturing project:

Even though parameters like dielectric constant are possible to be considered as constant numbers for most uses outside RF, they are a lot more variable in those strong ranges of frequency.

Heat management within the board is important due to the extreme thermal loads that a PCB assembly puts on the board. During drilling operation, the thermal conductance or resistance character of the material is crucial for the layer-to-layer orientation of multilayer stacks.

The distances between the features will also be crucial ones as RF boards can be very sensitive and interfere with the nearby features.

Determining the right material to use depending on the intended application and cost is therefore important since most of the rest of the challenges will arise from this decision.

In selecting material for RF PCBs, certain essential properties must always be considered.

Selecting the right material may compensate the whole process of manufacturing the RF board as it is arguably the most important decision made.

The Dielectric Constant, a Dynamic Characterization

Dielectric constant of a material is defined as the ratio of energy stored in the material placed in an electric field to the energy stored in vacuum in just for that field strength.

It depends on the direction, therefore this dielectric constant differs from the other based on the axes of the material.

The first one is measured with the use of Coefficient of Thermal Expansion.

The coefficient of thermal expansion (CTE) is the measure of a piece how its size changes for a given change in temperature. It is also a method for quantifying thermal resilience. It plays a major role in the drill and the assembly process of manufacturing of PCBs.

Just as in a multilayer stack, the electronic materials which can have different CTE’s are going to change their shape in a different manner. The issue of alignment becomes a very big concern during the drilling process when the layer above grows faster than the layer below.

PTFE, easily some of the highest quality RF materials which are used widely, can smear at drill if it gets hot and that cannot be erased. In the functional integration phase where components are being soldered on, the CTE determines how it will cope with the thermal expansion stress from soldering. A poor CTE can result to a broken of board in the final stage which is very costly to the company.

To address these issues, a material that has a lower CTE is going to be stronger when it comes to drill and assembly.

Loss Tangent

Loss Tangent, like the dynamic dielectric constant, is one of those difficult effects which appears in RF but is not really detrimental in lower frequency designs. That is the result of the molecular structure of the material, the fabric of the actual piece of clothing.

As a result, the signal is dispersed, absorbed and burned up as heat when the frequency increases. A rather important point is that in an analog circuit, amplitude loss takes place.

While in complex multilayer boards forming components can get rather compact and extra heat produced during operation is a factor to take into consideration.

Spacing

Where Cleaning is concerned, spacing can be a bit of an issue in RF applications because of crosstalk and what is called the skin effect.

Crosstalk is a situation where board height is started interacting with each other for instance, signals are coupled or interfere with nearby parts and undesired coupling. The skin effect is a situation in which the resistance of a trace starts to rise, resulting in losses of resistive kind, which make heat in a circuit. It is proportional to factors like trace width and length, and the problem escalates as frequencies rises.

The minimum distances that are safe vary in different ways. If you need answers to any minimum spacing question or any other RF PCB design guidelines, contact SFC today.

Moisture Absorption

Another factor to look at is the context in which your device will be working in. If the board will end up in a lab with an air-controlled environment, the moisture absorption may not concern you with this material. However, if the board is to be installed outside, or in a rainy climate or may likely to be in and out of water for short durations without prior planning, then moisture ingress poses higher importance.

Cost vs. Performance

Certain material types possess remarkable characteristics. They proposed dielectric constants and CTEs have been specifically designed to fit your application. Unfortunately, such materials are typically costly. It is, however, challenging to find a good balance between the cost, electrical performance and thermal characteristics; but certainly not unachievable.