Nobody should tell you that the PCB materials don’t matter because a circuit board is good as its makeup medium.
For this reason, we have numerous grades of PCB materials ranging from conventionally popular FR-4 to sophisticated mixes of FR4 and Teflon.
The arduous task is knowing which material to use in a particular scenario to ensure you strike a balance between quality and cost.
Don’t worry anymore; we’ll discuss PCB materials and their rightful applications with you in this guide. Check out for more.
Basic PCB Construction
PCB Board manufacturing and testing process.
When picking circuit board material, you must consider the environment where you’ll primarily use the device.
Another critical consideration is the electrical properties of the circuit board you want to achieve.
Here are the main PCB construction components and their applications:
PCB Materials and Construction Terms
The first four layers below comprise the core of a PCB board. But, we’ll further look at the other terms you’ll likely encounter in PCB assembly.
|Substrate Layer||This base material houses all the components and traces of a circuit board.|
|Conductive Layer (Copper)||The material is important in making connections within the PCB|
|Solder mask||It protects the copper traces on circuit boards from oxidation and shields the electrical transmitting parts from dust.|
|Silkscreen||A silkscreen is typically an ink trace for labeling the circuit board components. All the inscriptions and writings on a PCB are possible because of a silkscreen.|
|Annual Rings||An annual ring is a copper layer on the circumference of a PCB hole/via. It facilitates electrical conduction, especially during the through-hole mounting of components.|
|Copper Trace||It is the copper path through which electrical signals flow through on a circuit board.|
Other critical definitions of this topic include the following:
Design rule check: Before embarking on mass production of PCBs, the manufacturer must countercheck if it’s viable. It is the basis of the design rule check.
Blind and buried vias: The two are crucial in boosting a PCB’s functionality without taking up too much board space.
A buried via is a concealed connector between the PCB layers, while a blind via links an outer layer to one or several internal layers.
Surface Mount and Through Hole Mount: These are component placement methods.
Surface mount technology (SMT) typically involves laying components on the surface of the PCB via automated systems in an industrial setting.
Through-hole technology, conversely, involves component placement onto pre-drilled PCB holes. The latter is more intricate.
Factors to Consider When Choosing PCB Materials
What are some core considerations when picking up PCB materials to realize optimal functionality? Find out below.
Design/purpose of the circuit board
The design elements of a circuit board should always match its intended application. Its material must be up to the task if used in extreme temperatures.
Consider the loss tangent and dielectric constant for top electrical performance.
The latter represents the capacity of the material to store electrical energy, while the loss tangent is the overall energy signal loss factor.
A high-frequency material should have a relatively low-loss tangent and a low dielectric constant.
It is imperative to enhance performance by significantly curtailing signal loss and distortion.
Thermal and Chemical Performance
On thermal conductivity, the best-performing boards have a high heat dissipation rate.
It ensures they can lose heat fast to prevent it from affecting performance.
Therefore the material should be good enough to get away as much heat as possible from the PCB critical components.
Finally, an ideal PCB material should withstand chemical exposure in production and use environments.
Stack-up matters greatly, especially in determining whether the manufacturer uses a single or multilayer PCB.
Also, it is a critical consideration as it also affects impedance, so the manufacturer has to be careful to keep this factor under check.
One of the most critical factors in PCB materials is their coefficient of expansion (CTE).
For instance, if a material expands too easily in microelectronics, it would be inappropriate because it won’t fit in the casing.
Mounting parts on a PCB.
When setting up a PCB, the type of materials matter in determining if they can generate interference during signal transmission.
So the role of the manufacturer is to decide where to place the respective components for minimal interference.
The guiding factor in this process is the primary material quality.
Cost and Availability
It is especially critical for a DIY project whereby although the aforementioned performance factors matter, you must also consider the material availability.
For instance, including gold in your PCB will balloon production costs. The material is also not readily available.
Moreover, the design technology will depend on the overall cost. For example, using buried vias is key in reducing the PCB size.
But the cost and technology involved are so complex that it’s impossible in small-scale production even where the materials are available.
So the general rule is to balance the materials’ performance, cost, and availability.
The Most Common Types of PCB Materials
Below are the commonest PCB materials.
A plain FR-4 PCB.
Most of the printed circuit boards you have encountered are made of FR-4 because of the material’s excellent features.
It is available and quite cheap compared to other materials.
So what exactly is FR-4?
The material comprises a base material of fiberglass cloth with a flame-retardant epoxy resin to enhance its electrical performance capacity. Among its standout features include the following:
- FR-4 has excellent electrical insulation thanks to the epoxy resin component.
- Also, its composition ensures that it features excellent mechanical strength, thus suitable for multipurpose PCBs.
- Again, if you’re looking for a thermal-resistant PCB material, FR-4 will not disappoint you. It has a perfect glass transition temperature of about 140 degrees Celsius, which can withstand most electrical circuit environments.
- Also remarkable is its excellent dielectric strength, which accounts for its wide versatility.
But FR-4 may not be the best choice for high-frequency applications fundamentally because of its relatively high loss of tangent and dielectric constant values.
The material also easily draws moisture from the surrounding, potentially affecting its ability to conduct electric signals.
Automated PCB Manufacturing.
Polytetrafluoroethylene (PTFE) ranks as among the best replacements for FR-4, especially in high-frequency applications.
It has a relatively low dielectric constant. Its signal loss is also significantly low, making it popular in microwave operations.
Also, we encourage you to go for Teflon if you’re looking for a PCB material that will perform at the top level, even under high temperatures.
Its chemical resistance is also excellent, meaning it can withstand all the apparent production and working environments.
Nonetheless, manufacturers, especially in common PCB assembly applications, barely use Teflon because of its relatively high cost.
Processing it is also not as straightforward as with FR-4 meaning customers would have to wait longer to manufacture their Teflon PCB.
If you have encountered flexible PCBs, you have probably seen polyimide in use, as it is the primary ingredient of such circuit boards.
It has excellent flexibility in addition to extremely good thermal stability.
Moreover, Polyimide can withstand a wide range of chemical exposure without significantly affecting its structure.
But, like Teflon, it is costly and takes much time to process.
CEMs are initial for Composite Epoxy Material, and one quick fact about CEM-3 is that it is similar to the FR-4 above in many respects.
For instance, both have an epoxy resin impregnation, although the base material in CEM-3 is woven glass fibers.
So when do we use CEM-3 over Teflon? In scenarios where the aim is to cut the cost.
Their features are quite similar, and so are the performances.
Nonetheless, this also means that CEM-3 shares the inefficiencies of FR-4.
For instance, both are unsuitable for high-frequency applications because of their high dielectric constant and loss tangent.
Also, like FR-4, it’s prone to drawing moisture from the surroundings.
They are unique circuit board make-up materials by US-headquartered Rogers Corporation, a company dealing in quality PCB parts manufacturing.
Examples of common Rogers materials include the RO3000 and RO4000.
What makes them unique from the others we’ve already covered?
- First, they are best suited to high-frequency circuits because of the reasons we mentioned earlier for Teflon- They feature a relatively low loss tangent and low dielectric constants.
- Their thermal resistance is also pretty impressive, thanks to their low coefficients of thermal expansion (CTE). It means they can effectively function in a high-temperature environment without breakdown.
- Moreover, Rogers materials are the ideal go-to makeup elements for tailored performance electronics primarily because they fit in all extreme PCB applications.
But Rogers materials come at a high price, and they are less available than FR-4 hence their low popularity in common circuits.
Finally, we can also regard copper metal as a primary PCB material, as it is ever-present in all circuit boards.
Its cardinal role is to facilitate the conduction of electricity in the current.
Specialized PCB Materials
In specialized applications, we need high-quality materials of a different grade from the conventional circuit board makeup materials. Some of them include the following.
They are typically laminates similar to those in low-grade PCBs.
However, their unique feature is that they are designed to operate excellently in conditions of extremely high frequencies.
Hence their fundamental feature is low signal tangents and dielectric losses.
These properties are imperative in upholding signal integrity without significant distortions, even under high-frequency applications.
Common such laminates include:
- I-Tera MT series by Isola
- RT/duroid by Rogers Corporation
- TLY series by Taconic
Metal Core PCB Materials
You’ve probably heard of insulated metal substrates (IMS) or metal-backed PCBs.
They all represent circuit boards with a metal base, which is useful in enhancing their heat loss capacities.
Moreover, the metal core is key in ensuring the great mechanical strength of the PCB, meaning they can perfectly fit in harsh environments.
High-Temperature PCB Materials
As their name suggests, these are perfect for high-heat yield applications. Isola’s FR406HT is an example of a PCB built for such environments.
Another like-for-like alternative to the FR406HT is Rogers’ RO4835.
They guarantee reliability as they cannot break down even under extreme conditions, primarily because of their excellent thermal stability.
Environmental Considerations when Choosing PCB Materials
When picking up PCBs, consider several environmental factors, such as the following?
Material Composition and Toxicity
- Refrain from using highly toxic PCB materials that can harm the device users. Ideally, they should be lead-free and have no halogen materials.
- Secondly, always ensure your PCB material complies with the Restriction of Hazardous Substances (RoHS) directive, especially if you’re selling them worldwide. Another important regulation to follow is the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH).
- Lastly, only engage the services of PCB manufacturers that are keen on proper waste disposal.
Moreover, buy PCBs that are manufactured in a resource-efficient cognizant environment.
And finally, you and your manufacturer should uphold proper PCB disposal.
Whenever you buy PCBs, even for a simple DIY assembly process, the critical factor to check is their material.
Why? Because the material is among the main things that affect the PCB performance.
This guide has listed the top common PCB materials and their respective features. Therefore, choose the best fit for your application as an assembler.
Also, remember to go for the specialized PCBs for delicate applications such as making medical equipment PCB.