High Frequency PCB

High-Frequency PCBs are the backbone of most electronics.

From devices such as mobile phones to microwaves, PCBs play a vital role in the current circulations.

If you are a manufacturer or an importer, you need to understand all the aspects of these PCBs.

This guide addresses all relevant aspects of a High-Frequency PCB.

You will find this guide an important Tool when dealing with High-Frequency PCBs.

Let’s read along.

High frequency PCB

Chapter 1: What is High-Frequency PCB?

High frequency refers to a type of printed circuit board whose applications is common in devices that requires transmission of particular signals between objects.

Mostly, the frequency range of these PCB is between 500MHZ to 2GHz.

The most common applications that use this PCB include microwaves, mobile phones, and radio frequency.

Microwave PCB

High-Frequency PCBs usually have High-frequency laminates which are hard to fabricate. This is because they need to retain the thermal heat transfer of the application.

Chapter 2: Features of High-Frequency PCB

The simple way of understanding High-Frequency PCBs is by understanding its features.

The features give you an idea of what a High-Frequency PCBs are.

Here is a look at the features of High-Frequency PCBs.

High frequency PCB

• To avoid any delay in the transmission of the frequency signal, the DK needs to be smaller and stable. Actually, the lower it is, the better for efficient frequency transmission.
• The DF needs to be small since it affects the quality of the transmission of the signal. If possible, use a smaller DF for clear signal transmission.
• To avoid separation of the copper foil when there is temperature change, you need to check on the thermal expansivity of the PCB. For effectiveness, you need to ensure that the thermal expansivity of the PCB materials is the same as that of the copper foil.
• Ensure that the heat resisting property, impact endurance, chemical resistance and peel of resistance needs to be appropriate.

Chapter 3: Practical Applications of High Frequency Printed Circuit Boards

As a fact, High-Frequency PCBs are common in applications that require high heat and temperature resistance.

You will notice in the earlier chapter that one of the features of High-Frequency PCBs is its ability to withstand high temperature.

Therefore, have a wide range of applications that you can use High-Frequency PCBs. However, the most common ones include the following:

·Military Applications

You can use High-Frequency PCBs in a wide range of applications in the military. For instance.in the firearms and ammunition.

Rocket launcher

Manufactures of firearms such as guns, explosives, and ammunition use High-Frequency PCBs to ensure they are safe and functional.

They will use equipment such as penetration shock recorders or impact testing devices before releasing them for usage.

·Medical Applications

You cannot underestimate the contribution of electronics to the medical fraternity.

You will find electronics in diagnostic, monitoring and treatment devices.

Even with these applications, there is a constant improvement in electronic applications.

At the root of these applications, you will find these High-Frequency PCBs.

Their designs allow you to use them in various complex medical devices. Mostly, you will need a small size of a PCB to meet the requirement of a medical device.

As such, most of these PCBs are high specialty density interconnect which are also known as HDI PCBs. In some designs, these PCBs can have a flexible base material which allows them to flex during usage.

CT Scan

This is vital for either internal or external medical equipment.

Due to their areas of applications, such High-Frequency PCBs tend to have the highest standards than other types of PCBs.

While designing Medical PCBs, considerations need to be on their reliability and durability while adhering to the medical standards available.

Among the common medical devices that utilize High-frequency PCBs include the following:

• They can either be personal or healthcare monitors such as blood glucose monitors, blood pressure monitors, and heart rate monitors.
• Scanning technology. Under this, you will find devices for controlling fluid infusion, ultrasound scanners, CT scanner, and an MRI scanner. You will also find X-ray and MRI scanners.
• Scientific Instruments. Among the ordinary ones include microscopes, photometers, and control systems which apply to generators and compressors.

·Industrial Applications

Industrial application is yet another common area where you will find High-Frequency PCBs in use.

These PCBs have control of the various electronic components that you can find in factories and manufacturing industries.

Harsh temperature and different chemicals are a common factor in such an environment. While using these PCBs in such settings, you will have to choose thick copper PCBs.

Such kind of PCBs enables high current induction in the applications as well as battery chargers.

The advantage of High-Frequency PCBs in such applications is that they can withstand high temperature and chemicals.

Industrial control panel PCB

In industrial application, High-Frequency PCBs are common in the following areas.

• Industrial equipment. These include electric drill as well as electric presses which are common in the manufacturing industry.
• Measuring equipment where you can use them to measure and control temperature, pressure as well as other variables during manufacturing.
• Power Indicators which includes power inverters, generators, solar powers, and other power control devices.

·Advanced Communication System

You can also find High-Frequency PCBs in advanced communication systems.

These devices ensure clear transmission of sound even when they are far away which enables clear communication.

There are various functions in the communication systems that you can use these PCBs. They include High-frequency amplifiers as well as filtering devices.

 High frequency amplifier

Also, booster stations, frequency boards, mixing decks, receivers and microphones also use these PCBs.

In this industry, you will find lightweight, high-frequency PCBs which are durable and can match the density of the machinery in use.

The design and usage of these High-Frequency PCBs vary depending on the application that you are using.

·Radar Systems

In radar systems, you can find an extensive usage of High-Frequency PCBs.

They play a significant role especially in aviation as well as the marine industries.

In the marine industry, you will find the use of radar systems in various applications such as underwater and sailing applications.

In marine applications, radar systems prove to be a pivotal point in ensuring that ships avoid obstacles such as icebergs.

Radar system

Ships, as well as submarines, can use them in detecting enemy ships as well as destroying their targets.

In sailing vessels, you will find these PCBs in devices that power up the vessel.

There are considerable amounts of designs that you will have to make when using these PCBs.

This is due to the variation in pressure as well as the vibrations of the application.

In the aviation industry, the radar system is essential in guiding aircraft which helps in avoiding accidents.

Chapter 4: Step by Step High-Frequency PCB Design Consideration

Designing a High-Frequency PCB can consume a lot of your time and money. You, therefore, need to consider several factors before you decide to design a High-Frequency PCB.

Section of high frequency PCB

Such factors include your budget, schedule, the quantity you are to design and the international standards that you need to adhere.

Once you have considered these factors, you can now go ahead and design your High-Frequency PCB.

But how do you know that you are designing a High-Frequency PCB?

Three indicators will help you establish this.

First is the frequency of your PCB.

Most High-Frequency PCBs use anything above 50MHz to affect the circuit performance. You can also check on the traces.

You can check the physical measurements of the PCB traces to know if you are dealing with High-frequency PCB.

On a fundamental note, once you have a trace that is above a third the rise time of your application’s switching speed, then you are dealing with a high-frequency PCB.

Lastly, is by checking if your PCB is working as a unit or there are divisions.

If there are divisions in the working of your PCB, then you have a High-Frequency PCB.

Let me take you through the guidelines that you can use to design these PCBs.

At the end of these guidelines, you can now design a High-Frequency PCB.

High frequency board design

High-Frequency PCB Design Guidelines

Whenever you’re designing high frequency PCB, you should pay attention to the following key aspects:

1)Plan your High-Frequency Design

You need to have a proper design for your High-frequency PCB before you start the actual PCB design. This is important to avoid setbacks or to have unexpected issues with your PCB.

Examples of frequencies

What you need to do is to have a checklist if you are going to need during your PCB design. Among the key considerations that you need to look into include:

System organization which involves you having a visual representation of subcircuits interconnections.

2)Know the Signal Frequency of your PCB

Ensure that you have documented the power and voltage requirements for the ICs and if you will have to divide any power planes.

Check if you can accommodate the different signals, trace length as well as any controlled impedance.

At this stage, your manufacturer plays a vital role in ensuring that you understand what their minimum tolerance requirements are.

Also, you need to have a strategy that which will reduce the level of noise on your High-frequency signals

3)Document all Your Board Stack Up Plan for Manufacturing

Once you have a plan of how you are going to design your PCB, you will have to document the requirements for your stack up layer.

You can consult with your manufacturer to determine the specifics for your PCBs.

This includes understanding the materials and the specific constraints for your PCB. You can either use FR-4, Nelco or Rodgers materials for your PCB.

PCB design

You can have other strategies for your stack up such as having a signal layer which you can place next on an adjacent layer. This will offer signals that have an efficient return path.

You can also consider routing the high-frequency signals which are on the inner layers of your PCB between planes.

This will offer to shield over any radiation that it emits externally.

Also, on your layer stack up, you may use many ground planes.

The purpose for this is to reduce your reference hinderance which in turn minimizes the effect of radiation on your circuit.

4)Floor planning

This involves portioning your PCB into logical sections.

What you need to consider is whether you will have to place all your subcircuits into a larger design or separately.

PCB placement

You will find this vital when you have analog and digital sections that you have to isolate carefully to minimize interference. At the end of it all, you need to know the direction of your circuits.

5)Understand your ground and power planes

After defining the layout of your PCB, you are now free to check into the details of your design. This includes understanding the ground plane which you need to ensure it is complete.

Floating plane in PCB

That may include not dividing your ground plane with a routed signal.

Creating division on the ground plane means that you will have to rotate the void which may have an effect on the EMI and signal timings.

If it is mandatory that you have to split the ground plane, ensure that you include a resistor along the signal trace.

The purpose for this is to enable your signal to have a bridge which will facilitate the return path.

6)Minimize the size of your land patterns

One thing that you will notice with High-frequency PCB is that they have a smaller pad than the rest of the PCBs.

Actually, minimizing the space of your PCB is key to ensuring that you have a useful PCB.

High frequency PCB

On a general note, you can maintain the size of your Pad to be between 0 to 5% the size of the component pins. Other PCBs have a capacity of 30% of the component pins.

There are several advantages of minimizing space. It will maximize the mechanical strength as well as reduce the parasitic capacitance

Also, by reducing the space, you will have more space for differential pairs and high pin count space for your PCB.

7)Routing your High-frequency signals

The advantage of routing your frequency signals is to maximize the shielding benefits of your PCB.

What happens is that the high-frequency signals will emit high amounts of radiations as they move from the source.

This can result in interference between two different signals. To avoid this, you can route your frequency signals by observing a couple of options.

Rooting PCB

First, you need to minimize long and parallel signals to reduce any signal coupling. You can also maximize the distance of your signal traces.

The other option is to ensure that you route the signals to a different layer in case they are noisy.

Routing of signals on different layers needs to be orthogonal to each other.

This implies that on a signal layer, you can have traces that are either horizontal or vertical.

8)Have an efficient current return path

Each signal on your High-Frequency PCB will need a route that starts from the source terminating at the sink through the path.

This path requires minimal obstruction. It is an important aspect in PCB design and fabrication.

To ensure that the path is smooth, you might require the use of via in certain circumstances. Without this, the current might spread over the splits on your ground plan.

PCB Fabrication

The effect of this is that it can lead to a loss of the integrity of the signal.

If you are using via to reverse the current to their source, then you need to ensure that the coupling is tight.

Doing this will ensure that your signals arrive on time.

To reduce the distance that your signal has to travel, you need to place your reverse via too close to the signal via.

9)Minimize trace coupling by using the 3W rule

Line coupling can pose a severe challenge on the integrity of your signal during transmission.  To minimize this, you can use the 3W rule.

Signal transmission

3W rules state that the distance of separation between the traces needs to be thrice the width of a single trace measured from one center to the other.

This rule will increase the distance between the traces which in turn reduces the coupling effect.

To increase the gains of minimizing line coupling, you can increase the separation distance from three to ten.

10) Minimize plane coupling by using the 20H rule

Coupling that occurs between the power and ground planes can also pose a risk to your PCB design.

Here coupling in PCB will allow absorption of fringing to the ground plane instead of it externally radiating out.

PCB Signal coupling

The 20H rule states that you need to ensure that your dielectric thickness between the ground and adjacent power plane is 20 times thicker than the power plan.

11)Check on the routing guidelines

After all this, you need to check on the general routing guidelines for your PCB.

First, avoid the 90-degree bends on your traces since they can cause single reflections of your frequencies.

Multi layer PCB design

You also need to ensure that all the signals in the different pairs are of the same length and gap. This will maximize the advantages of electromagnetic field cancellation.

You need to design your transmission lines using microstrip traces. These strips will only offer a single reference plane that is separated by a dielectric.

Chapter 5: Characteristics of High-Frequency PCB Laminate Material

Understanding the characteristics of your High-Frequency PCB laminate material is critical when manufacturing your PCB.

You will be able to identify and understand the behavior of your PCB.

Here is a look at the characteristics of High-frequency PCB laminate materials.

·Dielectric constant (Er)

Dielectric constant is a measure of the ability of a material to store electrical energy while in an electric field.

This ability depends on the direction of the current implying that the dielectric current changes as the axis of the material changes.

What you need to understand is the frequency range that you will subject the material to while testing.

Relative permittivity

Also, you need to know the testing method and any variable present for the frequency range.

Lastly, you have to consider the constant dielectric conditions of your PCB that can match that of your application.

·Loss tangent

Unlike other PCBs, loss tangent is one of the challenges that affect the ability of your High-Frequency PCB to work effectively.

Loss tangent is as a result of a change in the molecular structure of the PCB material.

Dielectric loss

The change occurs when there is an increase in frequency which affects the signal transmission as some signals get lost due to burning out.

Also, in complex multilayer PCBs, you can have various components that are close to each other thereby generating heat.

The heat may also hurt the PCB frequency signals.

·CTE (coefficient of thermal expansion)

The coefficient of thermal expansion primarily refers to the change in the size of the PCB material as temperature changes. It is a way to calculate or determine the thermal robustness of a material.

You will find this aspect particularly crucial during the drilling and assembly stages of manufacturing your High-Frequency PCB.

Coefficeint of thermal expansion

When you have a multilayer stack, the different materials are going to have a different coefficient of thermal expansion depending on the temperature change.

In such a scenario, having the upper layer expanding at a faster rate than the lower layers can cause problems especially during the drilling stage.

Among the most commonly used material in the manufacturing of PCB is the PTFE due to its quality.

During the assembly stage, the coefficient of thermal expansion affects how to handle the thermal soldering force.

Having a Coefficient of thermal expansion that is of poor quality can break your PCB.

As a result, you can use a material that has poor Coefficient of thermal expansion during the drilling and assembly stages of your manufacturing.

Chapter 6: High-Frequency PCB Fabrication Process

The process of fabricating a High-Frequency PCB is simple. Once you have understood the considerations above, you can easily make your PCB.

The advantage of manufacturing your PCB is that you can customize it according to your specification.

Here are the steps that you can follow when manufacturing your High-Frequency PCB.

·Design your PCB

The starting point in the manufacturing of your PCB is to have a design for the PCB. This involves having a plan where you will lay the blueprint for your PCB.

PCB design

The most common designer software that uses for your PCB is the Extended Gerber.

Extended Gerber will assist you in encoding the relevant information that you may need.

This information includes the number of layers of your copper and the number of solder masks that you will need.

When you have encoded your PCB blueprint using the Gerber Extended Software, you need to confirm other aspects of your design.

After finishing all these, you will have to take your design to the fabrication center where manufacturing will take place.

It is here where your design will undergo a DFM check to ensure that your design attains the tolerance that meets the requirements is for production.

·PCB design printing

Once you complete checking your PCB design, you can go ahead and print it.

What you need to understand is that printing happens using a printer known as plotter printer.

What happens is that the plotter printer produces a film of the PCB which basically is the negative of the PCB.

The film contains two types of ink. You have the black ink which the circuit of your High PCB and the copper will use.

There is also the clear ink which that indicates the non-conducive parts of the PCB such as the fiberglass base.

However, the roles of the inks change when you are on the outer part of the layer of your PCB.

The clear ink will indicate the path of the copper while the black ink indicates areas of copper that you need to remove.

You will also have to use different films for each layer of your PCB and the subsequent solder mask.

For instance, if your PCB has two layers, you will need four films to serve each layer and the solder mask.

Once you have printed the PCB, you need to line up and punch a hole through them. This hole is called a registration hole.

·Copper printing for the inner layers

The actual manufacturing of the PCB by your manufacturer takes place at this stage.

Once you have printed the PCB onto the laminate, you will pre-bond the copper on the same laminate that acts as the structure of your PCB.

Inner layers of PCB

After that, you engrave the copper to reveal the earlier blueprint of your PCB. You then cover your laminate panel using a photosensitive film known as a resist.

The composition of this resist is a photoreactive chemical layer which hardens when you expose it to ultraviolet light.

Resist allows your manufacturer to obtain the best match between the printed results on the photoresist and the blueprint photos.

After lining up of your laminate and the resist using the hole, you will expose them to ultraviolet light.

Here, the light will travel through the translucent areas of the film which hardens the photoresist.

By hardening, you can see the copper areas which you have to use as pathways.

On the other hand, the black ink will intercept any light that tries to reach the areas which are not to be hardened which you can remove later.

After preparing the PCB, you will have to wash it using an alkaline solution which removes remnants of the resist.

Next, you have to pressure wash your PCB to detach anything that remains on the surface.

The next step is to allow your PCB to dry. After that, remove the resist from the PCB apart from the ones on the top of the copper. Be careful to avoid any errors at this stage.

·Inspection and alignment of the layers

This stage revolves ensuring that the layers are aligned as well as carrying out an optical inspection. You can use the holes to align the inner and outer layers of your PCB.

What happens is that you can place the layers on top of a machine referred to as an optical punch.

The optical punch will force a pin down via the holes to align the layers of your PCB.

After the optical punch, you can use another machine to do an optical inspection which ensures that the PCB lacks defects.

Inspection is necessary to prevent errors that can occur once the layers are together.

You can use an AOI machine to compare the PCB and the Extended Gerber design that acts as a model for your PCB.

·Lamination of the PCB layers

Once your PCB is free of errors, you can now move to the next step of the manufacturing process. During lamination, fusing of the layers of your PCB takes place.

The main steps that take place here are laminating PCB and lay- up steps. The outer part of your PCB consists of fiberglass precoated using epoxy resin.

PCB Lamination

A thin layer of copper foil covers the original material for your PCB with copper engravings.

After preparing the inner and outer layer of your PCB, you can go ahead and join them together.

You can use a metal clamp and a particular press table to sandwich the layers.

Fitting of the layers onto the table is by using a unique pin.

You can start this process by placing a pre-coated epoxy resin layer on the alignment bottom of the table.

You then place a layer of substrate on top of the resin layer and then a copper foil layer.

On top of the copper foil, you will add layers of pre-impregnated resins and then another copper foil layer.

Lastly, you will place a piece of press plate.

After that, you can now press the layers. You can use pins to punch down through the layers which ensure that you have fixed the layers correctly.

The next step is to laminate the PCB. Here, a pair of heated plate transfers heat and pressure to the PCB layers.

The heat will melt the epoxy while the pressure fuses the layers.

You will have to unpack the top press and the pins which will allow the actual PCB to be free.

·Drilling

Before drilling, you will have to use an X-ray machine to identify the drilling spots. After that, you can drill guiding holes which secure your PCB.

Drilling PCB

When drilling the holes, you can use a computer-guided drill with the help of the Extended Gerber design. After drilling, you can file off the extra coper left.

·PCB Plating

After drilling, you can now go ahead and plate your PCB. In this process, you will use chemicals to join the different layers together.

You will have to clean the PCB thoroughly before you bath it in various chemicals.

 Gold plated PCB

Coating of the panel in a micro – copper layer takes place during the bathing process. Bathing also helps in covering the walls of the drilled copper walls.

·Imaging and plating of the outer layer

This process involves applying to resist the outer layer through imaging.

After coating and imaging of the outer layer, you have to plate the interior layer in the same way as previously.

Imaging PCB

At this stage, the plating of the outer layer aids in protecting the copper on the outer side.

·Solder mask application

You will have to clean the panel in preparation for application of the solder mask. After washing, you will apply an epoxy ink together with the solder film.

You then expose the PCB to ultraviolet light which aids in marking portions of the solder masks that you have to remove. The next step involves you baking the PCB in an oven to cure the solder mask.

·Silk-screening and finishing

During the finishing process, you can plate your PCB with either gold, silver or HASL this will offer extra protection to the pad and the copper.

Silk screen PCB

After plating, you need to silk- screen your PCB. During this process, printing of all the vital information on the PCB takes place.

This includes the company ID number, the warning labels as well as the manufacturer’s marks. After that, you have to cure your PCB.

·Testing

Testing of your PCB is essential to ensure that your PCB functions appropriately. Testing includes circuit continuity and isolation tests.

Testing PCB

Circuit continuity test identifies if there are any disconnections in your PCB. On the other hand, the isolation test looks into the isolation value of your PCB to identify any shorts.

·Cutting and profiling

If your PCB passes the testing stage, you can move to the next step of cutting and profiling. Here, you can have several cuttings from your original PCB panel.

You can make cutting on your PCB in two different ways.  You can use a CNC machine that will cut little tabs on the edges of your PCB.

The other option is by using a V- a groove that will cut diagonal passages along the sides of your PCB.

Chapter 7: How to Choose Best Material for High-Frequency PCB

Having the right material for your High-Frequency PCB will minimize the chances of your circuit by sending mixed signals.

By having materials, such that have suboptimal copper foil can have severe effects on your circuit.

That is why you need to select the correct High-Frequency PCB material for your circuit. Here is how you can go about doing this.

·Consider Top High-Frequency PCB Material Manufacturers

Several companies manufacture High-Frequency PCBs. However, not all of them meet the standards international standards.

PCB Material

Always ensure that you obtain your PCB materials from the best manufacturers.

Among the top manufacturers that you can source for your PCB materials include the following.

1)Rogers

Rodgers is an international company with branches in America, Europe, Asia.

All of their PCB materials have proven to be reliable regarding performance.

Rodgers ltd sells laminated PCB materials that you can use to make circuit boards.

Mostly, the circuit boards materials that you can buy include Flame Retardant level 4 (FR4).

These materials can have a copper or glass fiber foil laminating both sides.

The FR4 that you can buy through Rodgers ltd are suitable for applications that have high-frequency properties.

What you will notice with purchase from this company is that they are expensive. However, the cost is worth it since the materials have a lossy characteristic in high-frequency applications.

2) Arlon

Arlon is among the leading manufacturer of high-performance laminate materials that you can use for various PCB applications.

Mostly, this company specializes in thermoset resin technology.

You can find the resin in the different substrate which includes non- woven aramid and woven glass.

Applications of Arlon PCB materials include military electronics, Density interconnect and Microwave PCBs.

With a manufacturing plant that is ISO 9001: 2008 certified, you can trust the products that they manufacture.

That is to imply that you get high quality as well as cost-effective materials for your applications.

The advantage with this company is that there are different options that you can use to purchase your PCB materials.

3)GIL Taconic

GIL Taconic is yet another company that deals mainly with different types of High-Frequency PCB materials.

This company has manufacturing plants in different countries such as the US, France, Poland, Brazil, and Korea.

The company itself is ISO 9001 and prides itself in the manufacture of high quality and cost-effective PCB materials.

The quality of these materials is that they have a high chemical as well as temperature resistance.

They also have high dielectric strength as minimal electric losses.

This implies that you can use these materials in manufacturing different application circuit boards.

Among the areas of application include Microwave laminates and customs belts for different circuit boards.

4) Metclad

Metclad manufactures high-quality PCB materials which you can use to assemble your PCBs.

They have different copper sizes which you can use choose from as well as different solder mask colors for your PCB.

There is always a guarantee that the materials you purchase from Metclad will give you service.

5)Isola

Isola considers itself as one of the leading companies that design and manufactures copper- clad laminates.

You can use these laminates in the production of advanced high-frequency PCBs.

The company has a global footprint which includes manufacturing facilities and research centers in Asia, Europe, and the US.

You can use Isola High-Frequency PCBs in different applications such as computers, networking, and communication equipment.

You can also use these materials in products that you can use in aerospace, military, and medical markets.

These materials adhere to the different international standards for the applications.

They include the International Material Data System, REACH, ROHS, and Perfluorochemicals.

6)Polyclad

If you are looking for a company that offers high-quality PCB materials, then you can pick Polyclad.

There are a variety of materials that they provide such as copper foil, solder masks, and boards.

Polyclad also offers assistance in designing and manufacturing your PCB.

There is a guarantee that you will get service on the materials that you purchase at Polyclad.

7)Asaki

Asaki offers high-end materials for your PCBs.

Though their materials are of expensive when you compare with other manufacturers, you have an assurance of quality service.

Among the materials that you can purchase include copper foils, solder masks, and even boards.

Asaki will also do an electric test for your PCB ensuring that you have a functioning PCB.

8)Hitachi

With its headquarters in Tokyo, Japan, Hitachi offers a wide range of quality PCB materials.

You can capitalize on its various offices around the world to purchase their products.

Also, they offer quality surface finishing for your PCB.

This include surface finishes such as HASL lead-free and ENG among others.

This company will help you design guidance as well as a guarantee for the PCB materials that you purchase from them.

9)Ehemical

Ehemical can customize your PCB according to your specification.

All you need to do is to produce a design for your PCB in an Extended Gerber format.

They will help you manufacture your PCB including electrically testing it.

If you choose to buy any material from them, you have a guarantee of quality materials from this company.

·Evaluate Dielectric Constant

You will have to take into consideration the dielectric constant of the PCB substrate.

Dielectric constant refers to the ability of a PCB material to retain energy in the electric field.

This will depend on which direction the material takes. As such, an effective dielectric constant need to be very small to deliver a stable input.

Dielectric constant

It is this input that will help minimize delay in the transmission of signals.

What you need to note is that the constant dielectric substrate needs to match for your PCB to function correctly.

If you have constant dielectric substrates that are not uniform may create problems in the functioning of your PCB.

Among the constant dielectric substrate that you can have include resins and woven materials.

·Know the Dissipation Factor

An effective dissipation factor needs to be very small. This is because having a high dissipation factor can affect the quality of transmission of the signal.

Losses in PCB transmission

By having a small dissipation factor, you will have less signal wastage while at the same time high signal transmission.

·Ability to Achieve Proper Spacing

The ability of your PCB material achieving proper spacing has an integral role in your PCB. This is especially when you are talking about cross-talking and the skin effect of your PCB.

Crosstalk refers to when the PCB starts self-interaction and is concerns with the coupling effect of the components. Since this coupling effect is undesired, you need to avoid it.

PCB Spacing

You can do this through ensuring there is the minimum distance between the plane and trace.

On the other hand, skin effect has a direct connection with the trace resistance.

As the trace resistance increases, the skin effect also increases which causes the PCB to start warming up.

As a result, you need to ensure that while selecting the PCB trace, the length and width need not affect the board when the frequencies increases.

·Consider Loss Tangent

You need to consider the molecular structure of the PCB material when looking at the loss tangent of your material.

The essential of this is to help in determining the effect the molecular structure has that can PCB material at higher frequencies.

·Peel Off Resistance

Peel off resistance refers to the ability of the solder mask to hold onto the PCB.

You can use this factor in determining the best solder mask as well as the copper foil that you can select for your PCB.

A useful material needs to have strong peel-off resistance. By choosing such a material, you have a guarantee of your copper foil holding off to the PCB for a long time.

This is essential when you are designing a High-Frequency PCB for applications that require high temperature.

·The coefficient of Thermal Expansion

The coefficient of thermal expansion refers to the effect temperature has on the size of your PCB material. Different materials have a different temperature characteristic including CTE.

While picking your substrate, you need to ensure that they have uniform CTEs.  Having different CTEs may cause the components of your PCB substrate to expand at different rates while operating.

This can result in defects or even altering the physical appearance of the substrate. Always pay attention to the CTE of your PCB material to ensure that you have uniform material for your PCB.

It is essential especially when you are subjecting the PCB to a different temperature.

Chapter 8: Surface Finish Selection for High-Frequency PCB

Surface finishing is one of the steps that you will take your PCB through. This is an essential stage since it gives the PCB an appeal as well as extra strength.

PCB Surface Finish – Photo courtesy: AMITRON

There are various options that you can use for your surface finish. The common ones include the following.

·HASL

HASL is an abbreviation for Hot Air Solder leveling and is the commonly used method of surface finishing.

Using this method involves dipping of your PCB in a melting solder bath.

From the bath, there is blowing of hot wind off the redundant soldiering to give a smooth, bright and uniform coat.

The availability and low cost of this method make it widely used in PCB surface finishing.

Generally, the shelf life of HASL is high thereby you are assured of the quality service. However, this method is not favorable for use in fine pitch PCB.

The availability of lead makes it a health risk when using it. However, other HASL variants lack the lead component.

Apart from that, there is also the disadvantage of solder bridging as well as thermal shock.

·ENG

Electroless Nickel and Immersion Gold is a type of surface finishing that utilizes the deposition of nickel and gold layers on the copper PCB.

This is happens using chemical electroplating which is basically a replacement reaction.

The use of this method has gained attraction due to the application of the RoHS regulations.

Among the advantages that you will gain through the use of this method include having a flat surface of your PCB.

It is also the best method if you are having Plated Through Holes not forgetting the long shelf life that it offers to your PCB.

However, this method is quite expensive.

It, therefore, makes sense if you are using it for large scale manufacturing of PCBs.

It can also lead to a signal loss if you don’t correctly apply to your PCB.

You need to take care when using this method to avoid damages from the ET.

·ENEPIG

Electroless Nickel Electroless Palladium and Immersion Gold is another type of surface finish of your PCB.

The main aim of this method is to eliminate the generation of a metallic compound that is common between the nickel and gold layer.

This happens through the introduction of Palladium which is a stable layer between the gold and nickel layers.

By minimizing the production of a new compound by nickel, Palladium inhibits black pads which is a problem when using ENIG.

The advantages of using this method include solderability, smoothness of the PCB surface and oxidation resistance. It is also heat resistance meaning that you can use it in the application that utilizes high heat.

·Immersion Tin

Immersion Tin is a traditional way of giving your PCB a surface finish.

The method entails a chemical displacement reaction that deposits metallic finish on the base of the circuit board.

By doing so, the Tin shields the underneath copper from oxidation thereby extending its shelf life.

This method gives your PCB a smooth flat surface as well as eliminating any pb.

It is the best choice if you are working on press fit insertion PCBs.

However, this method is not common in surface finishing of PCBs. This is due to its numerous limitations.

They include the availability of Tin Whiskers, being difficult to measure the thickness of the Tin.

Also, the method is not suitable if you are using multiple assembly processes.

·OSP

Organic Soldering Preservative is method that utilizes water-based organic compound to preserve oxidation of the copper surface.

This is through the application of a thin layer on the exposed copper that protects it.

The advantage you have with this method is that it offers a flat surface to your PCB.

The fact that it is a simple process as well as it being cost effective makes it favorable for use.

However, this method does not offer an opportunity to measure the thickness of the material protecting your PCB.

Also, you cannot use this method if your PCB has Plated Through Holes.

Apart from that, this method has a short shelf life while at the same time it can hurt the ICT of your PCB.

You need to go through the advantages and disadvantages of each method before selecting an appropriate surface finish for your PCB.

An effective surface finish needs to take into consideration the effect it has on the copper element.

Also, you need to consider the cost as well as the finish that you want your PCB to have.

Chapter 9: FAQs on High-Frequency PCB Design and Fabrication

This guide cannot be complete without going through what most of our clients ask for clarification.

Through this, you can expound on the available knowledge in as far as this guide is concerned.

Take a look.

High frequency PCB

1.What is the best price for High Frequency PCB?

The cost of your PCB is affected by several factors.

They include the raw materials, the thickness of the board as well as that of the copper and the surface finishing option.

Other factors include the trade width as well as the spacing. To minimize these costs, try as much as possible to design your PCB as simple as you can.

2.Why should you test electrically test PCB?

It is vital to electrically test your PCB since it is the only way that you can ensure that your PCB is well ready for use.

There are several tests that you can pass your PCB to ensure that it is useful.

It is the only way that you can identify any fault on your PCB especially any that can be present under the solder mask.

3.Is it possible to fabricate my PCB from a picture file?

No. it is not possible to manufacture a PCB using a picture file since these files are incompatible with the production process due to quality and the resolution.

To facilitate the manufacturing of your PCB, you need to ensure your design is in a Gerber Format.

4.What options do I have for my surface finishing?

There are various options available for your surface finishing. The choice of which surface finish to use depends on several factors.

They include cost, the desired effect that you want for your PCB and the impact the method has on the copper.

The available surface finishing option s include HASL, Immersion Tin, ENG, ENEPIG, and OSP.

You can also have HASL lead free option, immersion gold and Immersion Silver.

What colors are available for solder masks?

There are various colors of solder masks available for your PCB. The choice depends on your preferences.

Among the common colors include green, black, blue, white and yellow.

5.What is the difference between a buried via, a regular and a blind via?

The purpose of a buried via is to connect two inner layers of your PCB. In essence, it neither goes to the top nor the bottom layer.

On the other hand, a blind via serves the purpose of connecting either the top or bottom layer of the PCB to the inner layer. This type of via has to go through either the top or the bottom.

Contrary to the others, a regular via connects both the bottom and top layers of the PCB and it does pass through the inner layer.

6.What is the function of the decoupling capacitor?

The decoupling capacitor serves to level the noise from the power supply. While designing your PCB, you need to place it as close to the ICs as possible.

7.What is DRC?

DRC is an abbreviation for Design Rule Checking.  This is important to ensure that your PCB is free from any electrical failure.

While doing a DRC, you can encounter several errors on your PCB. They include a pad to pad violation. Trace to pad violation and component keep out the violation.

We would like to hear from you. Feel free to drop any question that you have, and we will be glad to offer clarification.

Conclusion

High-Frequency PCB plays an integral role in applications that require high heat resistance.

By having a circuit design that meets the internationally recognized standards, you can function appropriately.

As you have learned from this guide, there are several critical aspects of a High-Frequency PCB that you need to consider.

This includes factors to consider when purchasing a High-Frequency PCB as well as the design process.

At this point, I hope you can design a High-frequency PCB using the correct materials and guidelines. You can always get in touch with us for any assistance when it comes to High Frequency PCB.

We are always ready to assist you.