Blog  /  PCB Materials – The Ultimate Guide to PCB Manufacturing

PCB Materials – The Ultimate Guide to PCB Manufacturing

PCB materials are arguably the most important element in creating a printed circuit board that can handle any challenge that comes its way. Choose the right circuit board materials, and you’ll see success. Notably, using the wrong materials for your PCB application may land you in a lot of trouble. Read through our ultimate guide […]
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PCB materials are arguably the most important element in creating a printed circuit board that can handle any challenge that comes its way. Choose the right circuit board materials, and you’ll
see success. Notably, using the wrong materials for your PCB application may land you in a lot of trouble.

Read through our ultimate guide to help you make more informed choices when it comes to which printed circuit board (PCB) materials are used in your design.

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What are PCB Materials?

What are PCB Materials?

PCB materials are the physical building blocks out of which a PCB is constructed. These materials make up the many layers of the PCB and provide support for the board and insulation for the copper layers, which transfer electricity between components.

Each layer of the PCB layout is a different material. For instance, the substrate – the structural foundation of the PCB – can be made from a number of different materials, each with its own advantages and disadvantages.

PCB Arrangement

A printed circuit board is composed of several distinct layers, each serving a specific purpose in the board's functionality and construction.

Silkscreen

The silkscreen layer is the topmost layer on a PCB. It’s used for labeling components, test points, and other useful indicators. The silkscreen helps engineers and technicians identify various parts on the board, for correct assembly and easy troubleshooting.

This layer is typically made of non-conductive epoxy ink, with white being the most commonly used color. But you can use other contrasting colors like yellow, red, or blue to stand out against the solder mask.

Solder Mask

This PCB layer lies beneath the silkscreen and protects the copper traces from oxidation. It also prevents solder bridges from forming between closely spaced solder pads. It gives the PCB its characteristic green appearance.

The solder mask is usually made of a polymer-based material. This provides an insulating barrier to prevent short circuits and ensures solder only sticks to the designated pads.

Conductive Layer

The conductive layer contains the copper traces that form the electrical connections between components on the PCB. Depending on the complexity of the PCB, there can be multiple conductive layers (in multilayer PCBs), each separated by insulating layers.

The primary material used in this layer is copper due to its excellent conductivity. These layers can vary in thickness based on the requirements and design specifications of the PCBs.

Substrate

PCB substrate materials are the foundation of the board, providing it with its rigidity and structural integrity. The substrate layer is typically made of a composite epoxy material, commonly known as FR-4.

For a flexible PCB, the substrate can be made of materials like polyimide, which allows the board to bend and flex. The choice of substrate material significantly influences the PCB's performance, durability, and application suitability.

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Why is Choosing the Right Type of PCB Material Important?

Choosing the right material for a printed circuit board is important as PCB material selection influences the performance, functionality, and durability of the boards.

Why is Choosing the Right Type of PCB Material Important Factors for Choosing the Right Type of PCB Material

Influence on Electrical Performance

The material used in PCB circuit boards directly affects their electrical performance. This is because different types of PCB materials have varying levels of dielectric constant and loss tangent, which influence how signals transmit through the board.

High-frequency applications, for example, require materials with low dielectric constants and loss tangents to minimize signal loss and allow for efficient transmission. A careful choice of PCB material ensures that the printed circuit board meets all the electrical requirements of the specific application.

Signal Integrity and Speed

Signal integrity and speed are important factors in the performance of high-speed electronic circuits. You should select materials with high thermal stability and low signal loss to maintain signal integrity over longer distances and at higher speeds.

Choosing materials like high-frequency laminate material can help prevent signal distortion and crosstalk. This provides reliable and fast communication between components.

Impact on Durability

The durability of a circuit board depends largely on the types of materials used in its construction. PCBs made from high-quality materials can withstand a variety of environmental conditions like fluctuations in temperature, humidity, and mechanical stress.

For instance, composite materials like FR-4 are known for their excellent mechanical properties and thermal resistance. This makes them suitable for a wide range of applications.

Resistance to Physical Stress

PCBs are often subjected to physical stresses during PCB manufacturing, assembly, and operation. The material you select must be able to endure flexing, vibrations, and other mechanical forces without cracking or delamination.

Flexible PCBs use materials like polyimide, which can bend and flex without any damage. Using flexible materials makes them ideal for applications that require dynamic movements, like mobile phones.

Protection Against Corrosion

Corrosion can cause significant damage to a circuit board, which will lead to malfunctions. To prevent this, using materials with high corrosion resistance is important, especially in harsh environments or where corrosive substances are present.

Protective coatings composed of epoxy material or conformal coatings can help protect the PCB assemblies. Epoxy coatings create a strong barrier against moisture, dust, chemicals, and mechanical wear.

Conformal coatings are made from materials such as acrylic, silicone, and urethane. These provide a thin, flexible layer that adheres closely to the PCB's surface and increases the circuit board's durability.

Cost-Effectiveness

Cost is always a factor in PCB design and PCB fabrication. While higher-quality materials may have a higher upfront cost, they can lead to savings in the long run by reducing the need for repairs, replacements, and maintenance.

By choosing the right PCB material types, designers can make sure their PCBs meet the necessary electrical, mechanical, and environmental requirements. This will yield more efficient and durable electronic devices.

Most Common PCB Materials

Most Common PCB Materials

Common Materials for PCB Manufacturing

Substrate Materials

The substrate is the base material of the printed circuit board, providing the foundation for the circuit. There are several types of substrate materials used in a circuit board, each with unique properties.

FR-4

FR-4 is a widely used PCB material, made from a composite of fiberglass and epoxy resin. It’s known for its excellent balance of cost, performance, and durability.

For standard applications, the thermal properties of FR-4 material are good enough. This material is flame retardant, provides exceptional electrical insulation, and has robust strength and heat resistance.

Polyamide Materials

Polyamide is an ideal choice for flexible PCBs and various applications due to its outstanding properties. It is a chemical-resistant material that can withstand extreme temperatures, is highly flexible, lightweight, and offers good mechanical strength.

Plus, polyamide has low moisture absorption and favorable dielectric properties, making it suitable for insulating applications in electronics.

PTFE (Teflon)

PTFE, also known as Teflon, is used in high-frequency and microwave applications. It offers exceptional electrical properties, is highly flexible, and chemical-resistant.

It's often combined with fiberglass for added strength. But despite its advantages, PTFE is expensive and can be hard to manufacture.

Metal

Metal became popular in PCBs in the 1960s because it didn’t have the same limitations as the other materials widely used in PCBs. With excellent heat dissipation, strength, impact resistance, and thermal conductivity, it’s a strong choice.

Rogers Material

Rogers material is known for minimal signal loss and distortion at high frequencies, as well as its reliability at a high temperature. These materials are often based on PTFE, hydrocarbon ceramic, or woven glass, and they incorporate resin, filler, and copper foil.

Each material is formulated for specific applications, with common uses in RF and microwave circuits, high-speed digital circuits, and aerospace electronics.

CEM-3

CEM-3 consists of woven fabric and epoxy resin with cellulose paper as a filler material. It’s a less costly option than FR-4, with similar electrical and mechanical features. PCB manufacturers use CEM-3 for electronic circuits with moderate thermal needs, but it has limited suitability for high-temperature, high-frequency, or high-speed applications.

Kapton

Kapton is used in flex and rigid-flex boards and comes in three Pyralux versions: flame retardant (FR), non-flame retardant (NFR), and adhesiveless / high performance (AP). It's known for its superior thermal stability, chemical resistance, and electrical insulation properties.

Conductive Materials

Conductive Materials

Copper

The thickness of the copper material directly influences inductance, capacitance, and resistance. It can vary based on the number of layers in the board. A thick layer of copper is often used in boards that need to handle higher currents or require lower resistance paths.

In a multilayer PCB, the thickness of the copper layers is carefully controlled to balance performance and manufacturability, providing the necessary electrical characteristics for various applications.

Prepreg

Prepreg serves as an insulator sandwiched between copper layers or between copper and core layers. It bonds two layers together while maintaining separation between them, and consists of partially cured or uncured core material.

The prepreg material not only provides electrical insulation but also adds mechanical strength to the PCB. Its role is significant in multilayer PCB manufacturing, where it helps to align and bond layers, which is vital for the board’s overall structural integrity.

Solder Mask Materials

Epoxy Liquid

This is the lowest-cost solder mask available. It’s applied with silk-screening through the pattern onto the PCB. Despite its lower cost, it provides effective protection for the PCB surface, preventing oxidation and solder bridges between closely spaced solder pads.

This type of solder mask is commonly used in less complex and lower-density PCB designs, where cost savings are a significant consideration.

Liquid Photoimageable Solder Mask (LPSM or LPI) Inks

LPSM or LPI inks are cost-effective and sensitive to UV light. They can be silk-screened or sprayed onto the circuit board material, then exposed to the pattern and developed to create openings for soldering parts to the copper pads.

This method allows for precise control over the solder mask pattern, which is important for high-density PCB designs where accuracy is key.

Dry-Film Photoimageable Solder Mask (DFSM)

DFSM is vacuum-laminated onto the PCB, then exposed and developed. It’s ideal for high-density wiring boards, as it doesn’t flood the through-holes. The vacuum lamination process ensures a uniform and high-quality application, which is necessary for advanced PCB designs.

DFSM is highly reliable, making it suitable for complex circuit boards where precise solder mask application is required to prevent shorts and provide robust electrical performance.

What to Consider When Choosing PCB Materials

Choosing a PCB material requires careful consideration. It's tempting to just go for the main types, but your PCB may benefit from materials typically not used at first thought. Thoroughly consider the full range of materials available to you when choosing materials for PCB designs.

Material Strength

Materials with good damping properties are significant for applications exposed to mechanical shocks or vibrations. These properties absorb and dissipate energy from impacts, protecting the PCB and its components from damage.

Flexibility

Flexible materials are generally used for bendable and wearable technology, where the PCB must conform to various shapes without breaking. Materials like polyamide are ideal due to their flexibility and durability. Thick boards offer rigidity and durability, while thin boards are perfect for projects with space constraints.

Thermal Conductivity

High thermal conductivity reduces the likelihood of thermal-related failures. This is important for applications operating in extreme temperatures or generating significant heat. The glass transition temperature (Tg) represents the point at which the board material transitions from rigid to flexible, affecting thermal stability.

Electrical Performance

Important material properties to consider are the dielectric constant (Dk) and loss tangent (Df). The dielectric constant influences how fast electrical signals travel through the material, while the loss tangent measures how much energy the material dissipates.

Both factors affect signal clarity and performance in high-speed and high-frequency circuits. For applications that require high-frequency or high-speed data transmission, opt for materials with low Dk and Df.

Chemical Resistance

Chemical resistance is essential for industries such as chemical processing, oil and gas, automotive, aerospace, and marine. These industries often operate under harsh conditions, where exposure to corrosive substances is common.

A material with good chemical resistance protects the PCB from corrosion, enhancing its longevity and reliability. Consider the specific chemicals the PCB may encounter during its lifecycle.

Environmental Considerations

Choose PCB materials that comply with the Restriction of Hazardous Substances (RoHS) directive, limiting hazardous materials. Opt for lead-free and halogen-free materials to reduce environmental impact and health risks.

PCB Materials FAQs

Do the Properties of the Material Affect the Color of a PCB?

No, the main color seen on a PCB board is the solder mask layer, chosen to reduce glare and offer a sharp contrast with white text. Green is the most popular solder mask color, but it can be blue, black, yellow, or red.

What is the Cheapest PCB Material?

The cheapest PCB material is FR-4 laminated fiberglass, which is widely used for its low cost and reliability. If cost is something you need to consider when choosing a PCB, there's good news: despite being so affordable, FR-4 is also one of the top choices in any PCB material selection guide.

 

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