PCB materials, short for Printed Circuit Board materials, are the essential building blocks of modern electronics. Whether you’re designing a sci-fi masterpiece or a simple household gadget, you have to choose the right PCB to avoid unwanted hassles. Yes—the material of PCB significantly impacts the performance and suitability of electronic devices.
We thoroughly analyzed and tested a diverse range of printed circuit boards materials—making it easier for you to make an informed decision. Each PCB materials type is tailored to meet specific requirements and challenges. So let’s see which one suits your needs the best!
The selection of substrate materials shapes the effective performance and traits of printed circuit boards. Therefore, it is vital to select suitable materials when designing your circuit board.Most PCB materials consist of the epoxy resin substrate, glass fiber, and epoxy resin substrate attached to the copper foil. Copper is commonly used in PCBs because it is a good conductor of electricity.
Types of PCB Materials
Here are the various types and their unique benefits. Make educated decisions about your electronics projects.
1. Hard/Rigid Materials
You require rigid and ceramic-based materials when you want to maintain your circuit board shape throughout its lifespan. The solid feature of these materials prevents boards from forming other shapes. Rigid PCB materials are primarily applied in making computer motherboards.
The most common rigid materials are aluminum, aluminum nitride, and beryllium oxide.
Benefits of Rigid Materials
- They display an excellent functioning temperature of above 3500C.
- They are packaged in small sizes and integrate well with PCB components.
- They have a high dielectric constant.
- They do not experience outgassing problems.
- They have the least water absorption rates, facilitating hermetic packaging.
When to Use
- When you want quick repairs and maintenance – hard materials are integrated with clearly labeled components.
- When you want to minimize costs in high-volume production runs
- When your application requires a stable board.
- When you need a clear signal path.
Let’s explore the most common types of rigid substrate materials while covering their unique properties, benefits, and challenges.
Let’s explore the most common types of rigid substrate materials while covering their unique properties, benefits, and challenges.
FR1 PCB Material
FR1 is one of the widely used material of PCB. This is a paper substrate, having a thin copper layer on a non-conductive phenolic resin. Basically, this is an environment-friendly material that complies with ROHS regulations. It stands out for its ease of bending, processing, and molding. This makes it a suitable choice for single-sided PCBs. However, it is not the best choice for applications with through-hole components due to its limited heat resistance.
FR2 PCB Material
FR2 bears a striking resemblance to FR1 in terms of use and cost. However, it differs in terms of its heat resistance, with a lower glass transition temperature (Tg) of 150°C. This means FR2 may not perform as well as FR1 in high-temperature environments.
FR3 PCB Material
FR3 material of PCB is also a paper substrate, but it uses an epoxy resin. Its compatibility with epoxy resin gives it a slight edge over other paper-based materials, especially in coating applications. It is an ideal choice when a circuit board coating is needed.
FR4 PCB Material
FR4 is basically a glass-reinforced epoxy resin laminate, which is a widely-used versatile material. It meets the demanding UL94V-0 flame retardant standard, having good adhesion to copper foil, low cost, and excellent moisture resistance. It’s a go-to choice for double-sided and multi-layer PCBs for applications, including computer motherboards, power supplies, set-top boxes, and Bluetooth audio devices. However, it might not be the best option for high-frequency applications.
CEM1
Composite Epoxy Material 1 is a low-cost, flame-retardant composite material of PCB. It combines a glass fabric surface and paper core with epoxy resin. Its electrical and mechanical properties surpass those of paper materials like FR1 and FR2. This makes it a preferable choice for single-sided PCBs. Moreover, this PCB material is often used when cost-effectiveness is a prime concern.
CEM2
Among different types of PCB materias, composite Epoxy Material 2 is quite similar to CEM1 but comes up with some distinct qualities. It offers higher heat resistance due to its higher Tg value. For sure, it is a solid choice for applications where greater heat tolerance is needed. However, it does not possess flame-retardant properties.
CEM3
Composite Epoxy Material 3 is a copper-clad composite laminate made up of glass fiber cloth and copper foil impregnated with epoxy resin. It is a more cost-effective alternative to FR4. This material finds its place in double-sided PCBs with plated holes, offering reasonable performance at a lower cost.
Rogers Material
Rogers material stands out in high-frequency applications. It is basically well-known for low electrical signal loss, low dielectric loss, and excellent thermal performance. All this makes it a preferred choice in high-speed designs, RF, microwave, and mobile applications. While it provides remarkable performance, it can be relatively more expensive than some other options.
Metal Substrates
Metal substrates include aluminum and copper. The aluminum substrates are often employed in single and double-sided PCBs, as they excel in terms of electrical performance, heat dissipation capabilities, dielectric strength, and resistance to bending. Due to their cost-effectiveness, they are widely used in LED lighting products. On the other hand, copper substrates offer high thermal conductivity and are mainly used in specialized applications.
2. Soft/Flexible PCB Materials
Soft materials present multiple application options because of their ability to bend, wrap, and fold into many shapes. This is why they have gained more attention in modern consumer electronics than their rigid counterparts.
Soft materials are applied particularly for electronics that require a PCB that bends during operation without hindering the current flow. Various industries, such as healthcare, smartphone, and wearables, have embraced flexible PCBs widely.
Manufacturers integrate a polyimide film known as Kapton in flexible materials. The film displays good traits like heat resistance, dimensional consistency, and dielectric property of 3.6. Polyimide and polytetrafluoroethylene are the common flexible PCB materials.
The Benefits of Flexible PCB Materials
- They are space-intensive and minimize the PCB weight.
- With plastic dielectric materials offering little stability to the boards, flexible PCB materials such as epoxy guarantee good stability to the board by creating a coat near the filler.
- They minimize the PCB sizes, making them suitable for high-signal trace density applications.
- They are ideal for making boards for use in harsh environmental conditions as they are waterproof and corrosion-resistant.
When to Use Flexible PCB Materials
- When designing for harsh environments.
- When you need a miniaturized and lightweight board.
- If the application requires a bending PCB.
Let’s explore the primary types of flexible substrate materials while covering their unique characteristics, benefits, and challenges.
PET (Polyester Films)
Polyester films are the circuit boards materials that offers flexibility and high chemical and moisture resistance. Typically ranging from 25 to 125 microns in thickness, these films have a melting point of 250°C and a glass transition temperature of 80°C. It is particularly suited for applications that require compact and flexible circuit boards that can adapt to tight spaces.
PI (Polyimide)
Polyimide is a polymer renowned for its exceptional thermal stability, heat resistance, electrical properties, and chemical resistance. All these properties make it the material of choice for applications subjected to high temperatures and harsh chemicals.
PTFE (Teflon)
Polytetrafluoroethylene (commonly known by its brand name Teflon) is a preferred material for flexible circuit boards when temperature stability and low power consumption are essential. Its excellent temperature stability and low dielectric loss make it suitable for applications like cruise control, power amplifiers, and antennas. However, its use may incur a higher cost than some other flexible PCB materials.
3. Flex-rigid PCB Materials
Flex-rigid materials are a combination of soft and hard materials. They have multiple layers, mostly made of polyimide, and are widely applied in making circuit boards for the aerospace, medical, and military industries.
Benefits of Flex-Rigid Materials
- You can machine them easily.
- They are precision built; thus, suitable for applications that require high precision levels, like military and medical equipment.
- They provide a 60% reduction in weight and space.
- They display minimal dielectric losses at microwave frequencies.
When to Use Flex-Rigid Materials
- When you require lightweight boards.
- When designing boards for medical and military use.
- When handling relative frequency identification tags.
- When building automotive radar and sensors.
- When designing cellular receivers and power amplifiers.
4. RF-4 PCB Materials
This is a fiberglass-epoxy material that is cost-effective, an excellent electrical insulator, and more fire-retardant than fiberglass-only material. Besides, FR-4 is not just a PCB material but a graded material recommended by various international trade bodies, like NEMA.
FR is an abbreviation for ‘fire retardant’ and implies that it complies with the UL94VO standard. FR-4 materials exhibit high flame resistance properties because they contain bromine halogens. There are multiple sub-grades of FR-4 materials, such as TG130, high TG, and FR4-Rogers.
The Benefits of FR-4
- They are cost-effective and versatile.
- They are made of prepreg sheets, which consist of fiberglass matting and epoxy resins.
- They represent the electronic industry standard regarding easy boring and metallization.
When to Use FR-4
- When prototyping
- When your application requires low-speed circuits.
- When you want to minimize the production costs.
- When making a complex design that requires multiple layers.
Other Specialized PCB Materials Types
While standard PCB materials boards, like FR4 or flexible substrates, are suitable for a wide range of applications, there are instances where specialized materials are necessary.
Now, we’ll explore a range of specialized PCB types, each designed for unique applications. These PCB materials are engineered to offer tailored solutions, whether for heat dissipation, high-frequency signals, or other specific requirements.
Metal Core PCBs (MCPCBs)
Metal Core PCBs are constructed by bonding a metal core, often aluminum, with a dielectric layer and a copper circuit layer. These PCBs are commonly employed in high-power LED applications, where efficient heat dissipation is paramount. Their benefits lie in superior heat dissipation, which extends the lifespan of LEDs. However, MCPCBs might be excessive and costly for applications with lower power and heat generation.
Ceramic PCBs
Ceramic PCBs are crafted using ceramic materials as the substrate, frequently aluminum oxide (Al2O3) or aluminum nitride (AlN). They are well suited to high-temperature environments, including power electronics and high-power circuits. This is due to their remarkable heat resistance, excellent thermal conductivity, and electrical insulation properties. Nonetheless, their fragility and relatively higher cost can be limiting factors.
Teflon PCBs
Teflon PCBs utilize Polytetrafluoroethylene (PTFE) as the substrate material. They shine in applications demanding low dielectric loss and consistent performance at high frequencies. Their exceptional dielectric properties and low-loss tangents make them valuable for specific high-frequency applications. However, their cost tends to be higher than other materials, and they may not be necessary for all applications.
Hybrid PCBs
Engineers make hybrid PCBs by putting together different base materials on one board to get the best performance for each use case. These are known for being flexible and able to change how they work to meet different needs. Yet, they come with complexities in design and manufacturing, potentially leading to higher costs for custom solutions.
Thick Copper PCBs
Thick Copper PCBs feature copper layers that typically exceed 3 ounces (105µm). These PCBs are ideal for high-current applications where power distribution and heat dissipation are critical. Their notable benefits include enhanced current-carrying capability and improved heat dissipation. However, they may be excessive and costlier than needed for many low-power projects.
Copper-Invar-Copper (CIC) PCBs
Combining copper with invar, a material with a low coefficient of thermal expansion, results in CIC PCBs. These excel in high-precision applications where dimensional stability is essential. Their primary advantage is dimensional stability over a wide temperature range. However, these offer limited flexibility and come with a higher cost compared to other PCB materials.
Factors to Consider When Selecting PCB Materials
You need to consider the thermal, mechanical, electrical, and chemical properties of materials to choose the right fit for your application.
Thermally, you need to factor in the temperature durability of the components and the distribution of optimum functioning temperatures. Additionally, you should think of mechanical properties, like enclosure and form factor control, and the density, in the case of rigid-flex PCBs.
Electrical properties matter most when you need to balance the dielectric requirements such as impedance, signal quality, and resistances. Chemical factors like moisture absorption (prevalent in electronics functioning in agricultural IoT) and flammability are also essential for the proper performance of your PCB products.
Ideal for Multilayer PCBs
Boards are often stacked to save on space –multilayering. You need to consider the dimensional and electrical features while designing multilayer PCBs. Below are the materials that are ideal for building multilayer boards:
RO4000: It features the low-thermal coefficient of the dielectric constant to reduce phase variations and the CTE z-axis, closely related to copper. RO4000 materials are therefore suitable materials for making multilayer boards.
Flex-rigid materials: The RO3000 materials are particularly ideal for low-loss microwave boards, though they do not perform well in multilayer boards because of their dimensional and dielectric changes with temperature. However, they can perform well in multilayer PCBs if you work on their structural properties by integrating their electrical properties with the mechanical elements of polyimide materials.
PCB Materials to Use in High-Frequency Boards
Applications that require wireless connections, high speeds, and frequencies are living proof of the necessity of building boards with materials that offer excellent performance while maintaining signal strength and overcoming interference. Below are the ideal materials for building high-frequency PCBs.
Fluorine-series resin: PTFE materials display high dielectric performance and are suitable for making 5GHz frequency boards. They are the most expensive materials, and they have high-temperature expansion coefficients. Nevertheless, they function well in environments plagued with high dielectric loss and humid conditions.
PPO or PPE resin: They are excellent for building PCBs of 1-10GHz frequencies and guarantee reliable performance throughout the PCB lifespan.
Modified epoxy resin: They are suitable for creating boards with frequencies of 1-10GHz. Generally, they are the cheapest high-frequency PCB materials.
How to Choose the Right Materials for High-Frequency Applications?
- Matching the CTE properties: This is an essential substrate quality regarding temperature – ensure that the CTE between two materials matches to avoid expansion of substrates at distinct speeds and uniformities. Irregular CTE values can cause defects during the manufacturing process, altering the physical structure of the materials and their DK values.
- Tight material weave: You must weave your materials appropriately for them to interact well with the mesh.
- Matching the dielectric constants: If the Dk values of your materials do not match, you are likely to experience issues. For instance, pairing a resin with a woven layer will result in mismatched Dk values.
- FR-4 is not an alternative: As mentioned before, the FR-4 material is unsuitable for high-frequency boards. However, many designers use it because it is cheap, even when they are aware that it will affect the proper performance of their high-frequency circuits. Such circuits require low-loss materials.
The Future of PCB Materials
Although small developments in the silkscreen ink or the solder mask materials are not likely to hit the headlines, a lot of research and development focuses on improving the substrate materials for making different boards. The need for miniaturized and lightweight PCBs for consumer electronic products has amplified the demand for multilayer designs that offer more functionality and performance.
Advanced epoxy materials like Getek, Megatron, 4000-13, and FR-408, which boast better performance than FR-4 materials, will likely shape the future of PCBs. Additionally, we will experience wide use of high-performing materials like A-PPE, Nelco 600-21 Si, and Rogers 4350 because of their low dielectric properties, high impedance control, and minimal jitter.
Stringent RoHS standards will also boast the use of higher heat-resistant and reliable substrate materials. Halogen-free substrates reduce chlorine and bromine content in PCBs to around 900 ppm. Furthermore, lead-free substrates eliminate lead in PCBs by swapping the curing of traditional FR-4 materials with a PN curing method.
Conclusion
This article has offered a detailed analysis of PCB materials and the factors that you should consider when selecting materials for high-frequency circuits. We also touched on the future of PCB materials to keep you up-to-date with the current industry trends.
MKTPCB has rich experience in PCB manufacturing and assembling. Our highly experienced engineers can help you choose suitable PCB materials that meet your design requirements. You also need to understand the different PCB layers & types of PCBs to design a product that best fits your PCB needs. Kindly contact us today to learn more about our products and services.
Frequently Asked Questions
How to choose PCB material?
Choosing the right PCB material involves assessing project needs like temperature, electrical performance, and flexibility. Consider your budget, application (e.g., high-frequency or power electronics), environmental conditions, and heat dissipation requirements. Ensure compatibility with your manufacturing processes and consult experts for guidance.
What are the most common PCB materials made of?
Common materials include FR4 for general use, Polyimide for flexibility, Rogers for high-frequency applications, and specialized materials like ceramic for high-temperature environments.
Are There Eco-Friendly PCB Materials Options?
Yes. There are eco-friendly PCB materials options. Some manufacturers offer materials that comply with RoHS (Restriction of Hazardous Substances) regulations, which restrict the use of certain hazardous substances in electronics.
Is it Possible to Use Multiple PCB Materials in a Single Project for Optimal Performance?
Yes. It’s possible to use multiple PCB materials in a single project, known as a hybrid PCB. This approach allows you to optimize performance by tailoring materials to specific sections of the circuit. Just know that hybrid PCBs can enhance the overall functionality of your project.
