High TG PCB

Are you having a problem selecting a High TG PCB?

Or are you looking for more information about high TG PCB?

If yes, then you are in the right place

In this guide, you will learn all there is about a High TG PCB. This includes the features of a TG PCB and which material makes the best TG PCB.

In short, you will find the relevant answers for your query.

So, let’s read along.

What is High TG PCB?

Defining what a high TG PCB can be the ideal starting point of this guide.

In practical terms, when talking about TG in Printed Circuit Board, we are refereeing the Glass Transition Temperature.

Glass transition temperature

The flammability of a standard PCB is usually V-0 (UL 94-V0).

What’s the implication for this?

If the temperature of the PCB exceeds a specific TG value, the board will likely change its state.

Meaning, your PCB will change to a rubbery state from the solid state which in turn affects how a PCB function.

I hope I am not confusing you here. Let me take you slowly.

You see, the working temperature for your application can be higher than the standard temperature (130-140C).

If this is the case, then you will have to use a TG PCB material that is of a higher value which can be > 170C.

High TG PCB

What this means is that the temperature of your application needs to be lower than the temperature of PCB by at least 10-20C.

What is TG Value?

In the previous chapter, we have mentioned TG value on several occasions. But what does a TG value mean?

To start, TG is an abbreviation of Glass Transition Temperature.

It, therefore, refers to the temperature point beyond which the state of your material changes from solid to a flexible, rubbery state.

PCB Melts

There are two pieces of information that a TG value offer that is vital for your application.

First, it will help you understand the nature of the PCB material and at which temperature you can service it.

Second, the state of your PCB material. That is, whether the material in a solid, rubbery or rigid state.

Features of High TG PCB

If you are looking to purchase a high TG PCB for your application, you need to understand its features. This is critical when selecting one that can fit your application and function accurately.

There are four broad features of High PCBs that you can consider when selecting a particular High TG PCB. They include mechanical, electrical, thermal and chemical features.

Since these features are in general, allow me to work you through each of them.

Keep reading:

a)Thermal features of high TG PCB

Here, you need to consider the following key aspects:

• Glass transition temperature
• Decomposition temperature
• Coefficient of thermal temperature
• Thermal conductivity

Glass transition temperature (Tg) of your TG PCB is that temperature range at which your PCB material changes it’s state.

This is generally from a rigid state to a soft, flexible state.

This process is ordinarily reversible that is when the temperature of the PCB cools down, it returns to the initial state that it was.

For your high TG PCB to be useful, choose one with a high glass transition temperature.

Decomposition temperature (Td) refers to the temperature at which the TG PCB substrate decomposes chemically. Implying, the substrate will lose 5% of the mass or less.

You can express this in degrees Celsius.

One thing you need to note with a TG PCB is that the changes that occur are irreversible.

It is an important features when assembling high TG PCB.

So, what should you do?

Select material whose temperature is higher that Tg, but lower than the Td.

Coefficient of Thermal Expansion (CTE) indicates the stability of the vias. You can clearly use CTE to classify high TG PCB as high performance.

Normally, an increase in the PCB substrate temperature, results in the rise of CTE temperature.

In practical terms, having a high TG value will favor a low CTE-Z value.

This value represents the total expansion in the z-axis. By having a low z-axis expansion, you can prevent several errors that occur to your PCB.

This includes pad lifting or cracks within the via and corner cracks.

Thermal Conductivity (k) – refers to the ability of the high TG PCB to conduct heat.

What are the implications?

If there is low thermal conductivity, there will be a corresponding low heat transfer.

For instance, the thermal conductivity for most dielectric PCB materials ranges between 0.3 to 0.6 W/M-ºC.

For copper, the thermal conductivity is 386 W/M-ºC. This means that copper plane transmits more heat than what dielectric material carries.

b)Electrical features of high TG PCB

When it comes to electrical features of high TG PCB, you should consider the following:

• Electrical Strength
• Surface Resistivity
• Volume Relativity
• Dielectric Loss Tangent
• Dielectric Constant

High TG PCB

Dielectric Constant – it is also called Relative Permittivity (Er or Dk). Most materials have a Dk of between 2.5 and 4.5.

This aspect is vital when considering the strength integrity as well as the impedance of your TG PCB.

Dk increases with an increase in frequency and decreases with a decrease in frequency.

When considering material for your TG PCB, you need to pick materials that have a constant Dk on a frequency range of above 100MHz.

Dielectric Loss Tangent – this is also called dissipation factor. The Loss Tangent of material offers the measure of power loss as a result of that substrate.

A substrate that has a lower Loss tangent usually loses less power. Most substrates have a Loss Tangent of between 0.02 and 0.001.

You need to note that as the frequency increases so does the Loss Tangent.

Volume Relativity – you can also refer to this as the Electrical Resistivity (p).

It refers to the measure of the electrical resistance of a high TG PCB material.

If p of a TG PCB is high, the less readily it will allow for the movement of electric charge.

The measure of p is ohm- meters or ohm-centimeters. You need to note that temperature and moisture affect the Electrical Resistivity of your TG PCB.

You can also look at the Surface Resistivity (pS) of your high TG PCB when looking at the Electrical feature.

This refers to the measure of the insulation resistance or electrical resistance of the surface of a TG PCB substrate.

For efficiency, you need to ensure that your TG PCB has a higher Surface Resistivity. Also, moisture and temperature affect Surface Resistivity.

Electrical Strength – it is a measure of the ability of the PCB to resist electrical breakdown. This is about the Z direction (which is perpendicular to the TG PCB plane).

You will find that the best materials have an Electrical Strength value of between 800 V/mil and 1500 V/mil.

You can determine the electrical strength of a material by subjecting it to a short high voltage which is at a normal AC power frequency.

a)Chemical features of high TG PCB

Chemical features of a TG PCB involve several aspects that you can examine to select the best material.

Corrosion on PCB

First, you can have a look at the Moisture Absorption of the PCB material.

Moisture absorption is the ability of a TG PCB substrate to resist absorption of water or moisture when in such a surrounding.

Moisture Absorption affects the electrical and thermal features of the PCB material.

It also affects the material’s ability to resist the formation of a Conductive Anode Filament during powering of the PCB circuit.

Another aspect is the Methylene Chloride Resistance of your PCB material. This is the measure of how a material resists to chemical properties.

This is more so its resistance ability to methylene chloride absorption.

b)Mechanical features high TG PCB

Another feature that you can examine when dealing with a high TG printed circuit board is the mechanical feature.

Here, you need to evaluate the following:

Peel Strength which measures the bond strength present between the dielectric material and the copper conductor. The unit of measurement of the Peel Strength is pounds of force per linear inch.

Flexural Strength measures the capability of the material to withstand mechanical force without fracturing.

Young’s modulus is yet another aspect of mechanical features that you can have for your PCB. Here, it refers to the measure of the strain ratio of the material in a particular direction.

Best Materials for High TG PCB

As we will see later on, there are a variety of physical characteristics that you can use to identify the best material for your high TG printed circuit board.

You will realize that there are a range of high TG PCB material.

The choice of material to use will have a great impact on your application.

Here is a look at the different elements that you can use when manufacturing your High TG PCB.

The primary material that you are going to use for your TG PCB includes the substrates and the laminates.

Substrates are mainly dielectric composite structures comprising of glass or paper weave and epoxy resin.

PCB Material – Photo courtesy: EPEC

In certain types, ceramics complements the substrate to increase the dielectric constant.

Quality substrates should meet specific set requirements such as Tg.

There are a variety of substrates that you can use to manufacture your high TG PCB. They include:

• FR-1 thru FR-6, G-10, and G-11
• CEM-1 thru CEM-5.

Others are flexible substrates Pyralux and Kapton, Aluminum or insulated metal substrate and Polytetrafluoroethylene (PTFE), RF-35.

When it comes to the manufacturing of laminates, do this under pressure, and it constitutes thermostat resin and paper or cloth layers.

You can customize laminates as per the requirements of your TG PCB. However, you need to ensure that they meet the available standards.

Such standards include shear and tear strength, Tg and the CTE.

The ordinary laminates that you can use include CEM-1 and CEM-3 polytetrafluoroethylene (Teflon) and FR-1, FR-4.

Selecting the correct substrate as well as the laminate forms the basis of having a quality TG PCB.

Classification of High TG Printed Circuit Boards

You can use different criteria to classify your High TG Printed Circuit Boards.

These criteria include the following.

1.Component Location on High TG Printed Circuit Board

You can have embedded, single-sided or double sided PCB.

2.Stack Up PCB

Another criteria is the stack up of your TG PCB. Here, your TG PCB can either be single layer or multilayer.

3.Design of High TG Printed Circuit Board

Design is yet another important classification criteria.

The design can either be custom, unique or module-based TG PCB.

In custom high TG PCBs, you’ll come up with the design, and the manufacturer fabricates a TG PCB for you.

Classification of high TG PCB

For unique PCB, you can buy directly from the manufacturer and request for some changes on specifications.

It will all depend on your application requirement.

While the module based is one which your manufacturer has designed. The manufacturer provides it on specific applications.

4.Bendability of PCB

The other criteria that you can use to classify your TG PCB are the bendability of your PCB.

In this case, your PCB can either be flex, rigid or rigid- flex.

5.Classify PCB depending on strength

Furthermore, you can use strength criteria. Here, you can have electrically sturdy TG PCB or mechanically robust TG PCB.

6.Electrical functionality of PCB

Lastly, you can use the electrical functionality to classify your TG PCB.

In this case; you can have high density, high frequency, or microwave TG PCBs.

Each of these criteria, however, there is limitation.

For instance, component location, stack up and design is poor criteria of classifying your TG PCB.

This is because you cannot base them on the material properties of the TG PCB.

However, the use of bendability and strength criteria are the best when classifying the physical properties of your TG PCB.

High TG PCB

It is because they define the outward effect of your TG PCB when they interact with various surroundings.

You can use the electrical criteria to classify your TG PCB if you want to design PCBs.

In this regard, when you are talking of High-frequency TG PCB, it implies that your PCB can hold frequencies of between 500MHz – 2GHz.

When you classify your PCB as High Power, it means they can transmit high currents.

This requires you use thick copper and broader traces.

And, why is this important?

To assist the High-power PCBs in dissipating high temperature effectively.

In regards to High Density, it implies that the PCB has thin trances.

As such, they usually take advantage of the micro-vias and light materials that have high performance.

Lastly, microwave classification means that there is a presence of signal speeds in the range of 1GHz to a couple of GHz.

However, the spectrum of microwave extends typically in the range of 300MHz to 300GHz.

Why is this classification important?

You can use it when selecting the best material to use for your design.

Step-by-step High TG PCB Designs and Layout Process

The main question that arises when dealing with High TG PCB is about the printed circuit board layout and design.

This is a vital question especially if you are a manufacturer or you want to customize your own High TG PCB.

High TG PCB design and layout

In this section, I will take you through the steps that you can easily follow when designing the layout for your High TG PCB.

Keep reading.

I.Designing High TG PCB

The first step towards fabricating your TG PCB is to have a design that you are going to use. Here, you can use different software to assist you in coming up with a design for your PCB.

Such software includes Altium Designer, OrCAD, Pads, KiCad, and Eagle.

It is vital that your manufacturer gets to know which software you are using to design your PCB.

II.Identifying which frequency signal, you will use on your TG PCB

After designing your TG PCB, you can go ahead and select the suitable voltage and power requirements for various electrical components of your PCB.

You need to check on the trace length and any impedance available on the board.

PCB design software

You can engage the services of your manufacturer who will ensure that you have the minimum tolerance requirements for the board.

You also need to check if you have a workable plan on reducing the noise emanating from the TG PCB.

III. Documentation of the stack up plan for the board

Proper documentation of the requirements for the stacking up plan is critical for the successful fabrication of your high TG PCB.

You can engage your manufacturer to give you the specifications that you will need.

Check on the type of material and the correct constraint specifications for your high TG PCB. Here, you have the option of either FR-4, Nelco or Rodgers materials.

PCB made from Rodgers material

If there is a presence of high frequency on the inner layers between the planes, you can route them.

This is critical to insulate the layers against radiation that the signals emit externally.

You can include ground planes on the stack-up. The importance of this is that it assists in reducing the effect of radiation on your circuit.

IV.Floor planning

Floor planning is all about partitioning your PCB to relevant parts.

Here you need to consider if you will put all the components into a large design or placing them separately.

Sample floor planning for PCB – Photo courtesy: Electronic Design

You will find this step crucial when designing analog and digital parts that you will have to isolate thus reducing interference.

Again, at this point, you have to identify which direction your circuit will take.

V.Identify the power and the ground plane

Here, you need to identify all the details of your TG PCB including the ground and power plane and confirming if they are complete.

Ensure that the routed signal does not divide the ground plane.

Planes on PCB – Photo courtesy: Analog Devices Inc.

Dividing the ground plane will make you rotate the void present since it can affect the signal timings and the EMI.

If you have to split the ground plane, you need to have a resistor along the signal trace.

This will serve to facilitate the signal by acting as a bridge so that you can have a return path.

VI.Checking the land pattern sizes

You need to have the correct pattern sizes for the board.

For you to have the right proportions, you need to have accommodation for all the parts to function correctly.

VII.Routing high- frequency signals

Routing high-frequency signals will assist in shield effect maximization on your high TG PCB. Remember, high-frequency signals emit high amounts of radiation as they transverse from the source.

High TG PCB

Radiation can affect the signals. However, you can route such signals in two ways.

You can minimize the parallel and long signals which reduce the coupling of the signals.

The other option is to increase the trace distance of the signals.

The other option if they are still noisy is to route the signals onto a different layer.

You need to ensure that they are orthogonal to each other.

That is to say, they can either be vertical or horizontal.

VIII.Check on the return path

Make sure that there is a route that originates from the source and terminating at the sign through the path for each signal. Your path should be clear.

Vias are essential in certain situations since they aid in having a smooth path.

Types of vias

This is through reducing chances of spreading current across the splits present on your PCB.

In case this happens, it may affect the quality of the signal.

You can have a tight coupling by using the via to reverse the current to the source.

Tight coupling facilitates the arrival of the signals on time.

To reduce the distance the signal travels, you can place the reverse via close to the signal via.

IX. 3W rule

It helps in reducing trace coupling which affects signal transmission quality.

This rule states that distance of separation between traces should be three times the width of a trace measured from one end to another.

The 3W rule increases the distance of the traces leading to a reduction in the coupling effect.

If you want to reduce the coupling effect completely, you can increase the distance of separation to 10 from 3.

X.20H rule

If you’re going to minimize the coupling effect on the plane, you need to apply the 20H rule.

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

Coupling of the plane occurs between the power plane and the ground plane posing a risk to your TG PCB.

This coupling permits fringe absorption to the ground plane instead of emitting it out externally.

XI. Checking the routing guidelines

Finally, you have to check on the routing guidelines to ensure you have followed all of them.

First, avoid using the 90- degree bends on the traces sing they can result in frequencies that have a single reflection.

You can also check on the signals of different pairs to ensure they have the same gap and signal. This will facilitate electromagnetic field cancellation.

You can also use microstrip traces for your transmission lines. This ensures that the traces provide a signal reference plane that a dielectric separates it.

You manufacture will also assist you in ensuring your TG PCB passes the mandatory tests and quality standards.

The importance of this is to help you in having a TG PCB that offers quality service.

High TG Circuit Parameters & Specification

There are different parameters and specifications that you can use to manufacture a High TG PCB. These specifications depend on your application.

High TG PCB specification

However, the common parameters that you can use include the following:

·Number of layers

One of the settings that you need to consider when manufacturing a TG PCB is the number of layers to use.

PCB layers

As a recommendation, you can have even number of layers to make quality PCB. Of course odd numbers can work depending on your requirements.

·High TG PCB board dimensions

The choice for the board dimension will depend on the application that you are going to use.

If your application is broad, then you will have to use a larger board dimension.

PCB Dimensions

You will also have to check if the electrical components can fit on a particular board dimension before manufacturing your TG PCB.

·Surface finish for high TG PCB

There are different types of surface finishes that you can apply on your TG PCB.

Your choice will depend on what you want to achieve.

High TG PCB

The most common ones include:

i.Hot Air Levelling (HASL)

There are two types of HASL that you can use for your surface finishes. You can choose from spray tin with lead and spray tin with lead- free.

HASL has longer storage time and cost effective.

Besides, you can use it on lead- free soldering.

ii.Organic Protective Film (OSP)

OSP is simple and leaves a smooth surface.

Furthermore, OSP is cost affective, making it a perfect choice for high TG PCB.

Unfortunately, you cannot use OSP with line binding and crimping technology.

iii.Immersion silver

Most high TG PCB tend to use immersion silver for their surface finishes. They are suitable due to their low cost as well as their ability to leave a flat surface.

Immersion silver, however, has high storage requirements since it can easily be contaminated. You might also experience micro- hole issues when welding and electro migration phenomena.

iv.Immersion Tin

Immersion Tin is another type of surface finish that you can use for your high TG PCB.

It is suitable for SMT.

However, there are several limitations that you will experience when using this kind of surface finish. First, you cannot apply this finish on the contact switch.

Second, you must meet high solder mask processing requirements. Or, you’ll run the risk of solder mask peeling off.

v.Immersion Gold

It is a common surface finish for high TG printed circuit board.

But, why use immersion gold technique?

You can use it for electrical testing your PCB as well as for contact switch. The fact that you can store it for a long time with minimum requirements makes it ideal for use.

vi.Nickel palladium (ENEPIG)

ENEPIG is becoming common when doing surface finishes on TG PCB.

This is due to its ability that allows you to use both aluminum and gold trace binding.

Among the advantages of nickel palladium finishing is the long storage time. It is also suitable for different TG PCBs as well as surface treatment.

However, it is a complex process. Besides, you may not control the entire process easily.

·Solder mask

The solder mask refers to the layer that protects your PCB against external impurities.

Besides, it provides separation between the surface elements including drill holes, copper traces, and pads.

Solder mask

There are several options for applying solder mask on your TG PCB.

Among the common ones include:

• Screen printing
• Curtain coating
• High-Pressure Low Volume (HPLV) Air Spray
• Electrostatic Spray

You choice will depend on the specific requirements of the high TG PCB.

Take for example, if TG PCB requires tenting, then you must avoid applying liquid solder mask.

·Copper weight

We can look at copper weight as a specification that you need to consider from two angles.

The first angle is the beginning of copper weight.

Copper on PCB

This refers to the copper that you use to start the manufacturing process for your PCB. Typically, you can have different weights such as 5oz, 1oz, 1.5oz.

This is important when you want to select the base material for your TG PCB.

The second one is the finished copper weight which is more critical than the beginning copper weight.

Because your manufacturer will use this to determine the finished copper thickness for your high TG PCB.

If you are using different finished copper weight for the layer, then you need to label each layer separately.

·Finished board thickness

The thickness of the TG board varies depending on its nature.

To say, that you can have different board thickness depending on whether your board is rigid, flex-rigid or flexible.

·Spacing

For quality transmission of frequency signals, ensure you have an equal spacing of the layers and the electrical components.

The purpose is to minimize the coupling effect. Besides, it helps in swift emission of radiation.

·Hole sizes

It is crucial to consider hole tolerance and the PCB drill aspect ratio when determining the hole sizes for your TG PCBs.

There are two types of drill holes that you can have for your board:

• Plated through holes
• Non- plated through holes

Non- plated through holes don’t transmit current. As a result they don’t have conductive plating. Example of non- plated through holes are the mounting holes.

On the other hand, plated through holes are the signal carriers also known as ground returns. They transmit current thus they need a conductive plating.

They are often vias that are between the inner and outer layers, on the surface to surface or on the inner layers only.

Non- plated through holes should have a minimum hole size of 0.006″. The smallest edge to edge clearance needs to be 0.005″ from any surface element.

Printed circuit board holes

Plated Through Hole should have a minimum hole size of 0.006″ while the minimum annular ring size should be 0.004.”

If your board has to be IPC Class 2, the annular ring should be at the bare minimum 0.004” larger than your drilling hole. This should be from every angle.

The board thickness limits the drilling of holes whether mounting holes or vias. To express this limitation, you use the aspect ratio concept.

The aspect ratio expresses the relationship between the diameter of the hole and its depth.

·Quality grade

You need to ensure that the grade of your TG PCB is higher to offer quality service on your application. There are different grades in the market which have different functional capability.

·Quality tests

You will run various quality tests to ensure your high TG PCB meets necessary performance specifications.

Of course, the choice of test will depend on the nature of the application.

It’s this simple, you must tests everything –  lamination, copper plating, solderability, hole wall quality, electrical, environment, cleanliness of your PCB, etc.

Among the most common tests are In-Circuit Test, Fixtureless In-Circuit Test, Functional Circuit Test, and Boundary Scan Testing.

Testing PCB

Of course, quality testing goes hand in hand with quality compliance.

The high TG PCB must have quality compliance certificates and marks.

Main Applications of High TG PCB

High TG PCB are common in applications that use high temperature.

The best part:

Heat generated by the system will not affect performance of the printed circuit board.

Below are some of the most common applications:

1)Industrial application

High TG PCB is common in various industrial application due to their high-temperature requirements. Such equipment usually operates in harsh environments like harsh chemical and temperature environment.

In most of these applications, High TG PCB that use thick copper is often common. Here, they facilitate faster battery chargers and high current industrial use.

Good examples are electric drills and presses which make use of High TG PCBs.

Also, you will find these PCBs in measuring equipment.

Solar power PCB

Lastly, you can find these PCBs in power equipment.  Such equipment includes solar power cogeneration equipment and power inverter.

2)Automobile electronics

Automotive electronics also use the high TG PCBs. In fact, with the invention of self-driving cars, these PCBs are bound to be of significant use.

Automotive electronics

Radar technology has also gained momentum in the automobile industry. Radar technology heavily borrows from High TG PCBs in their manufacturing and functioning process.

Other applications that you can find TG PCBs in automotive electronics include control systems and surrounding monitors. You will also see them in navigation devices and audio and video devices.

3)High-temperature applications

High TG PCBs are temperature resistant, making them a perfect choice in many applications.

Among the common applications include the use of LED technology which is gaining popularity.

LED lighting technology

You will find this technology in industries like the telecommunication industry, computer technology industry and medical industry.

Other applications that use High TG PCBs include broadcasting applications such as booster stations frequency boards and microphones. You can also find them in security applications such as fire detectors and burglar alarms.

Conclusion

After going through this guide, you are now an expert on anything to do with a TG PCB. You need to pay particular attention to the fabrication process as well as the specifications for a quality TG PCB.

Having a manufacturer who can help you customize high TG PCB is advantageous.

If you are still finding any difficulties, get in touch with us today.

We will be glad to offer professional assistance.