PCB Materials

A Comprehensive Guide to Copper Clad Laminate (CCL) Used in PCB Fabrication

Get an in-depth understanding of Copper Clad Laminate (CCL) materials used in printed circuit board (PCB) fabrication. Learn about the different types, manufacturing processes, properties, and applications of CCL, as well as tips for selection and handling.

What is CCL?

What is Copper Clad Laminate?

Copper Clad Laminate (CCL) is a core material used in the fabrication of printed circuit boards. It is a composite material made up of a layer of copper foil, a substrate, and an adhesive. The copper foil is typically applied to the substrate with an adhesive layer in between, creating a laminate material. CCL is also known as copper-covered laminate or copper clad laminate due to the presence of the copper layer.

The use of CCL in PCB manufacturing is essential for creating a reliable and high-performance circuit board. The quality of the CCL can directly impact the overall performance and reliability of the finished PCB. Superior quality CCL can ensure good bonding between copper and the substrate, reducing the chance of delamination failures, and improving the electrical conductivity of the board.

Benefits of Copper Clad Laminate in PCB manufacturing

Excellent dimensional stability

Ensuring precise circuit alignment and shape maintenance of the board.

Excellent thermal conductivity

Protecting the board from overheating and extending its lifespan.

High dielectric strength

Allowing it to withstand high electric fields without breakdown.

Composition and Materials of CCL

Copper Clad Laminate is a critical component in PCB manufacturing, and it is made up of several different materials. The basic structure of CCL includes a substrate, copper foil, adhesive, and auxiliary materials such as release film. Each of these materials plays a crucial role in the fabrication process and determines the performance characteristics of the final product.

Materials used in Copper Clad Laminate

Substrate

The substrate is the foundation of the CCL and can be made of various materials such as synthetic resin, fiberglass, or paper. The substrate provides the required mechanical strength and dimensional stability to the PCB, as well as insulation between the copper layers and other circuit elements.

Copper Foil

Copper foil is the conductive layer of the CCL, and it is bonded to the substrate through an adhesive layer. There are different types of copper foils available, including electrolytic copper, rolled copper, and thin copper foil. Their selection depends on the requirements of the application, such as electrical conductivity and flexibility.

Adhesive

The adhesive is a critical component that binds the copper foil to the substrate layer. It provides good mechanical strength and stability to the CCL, and the selection of adhesive material depends on factors such as curing process, thermal resistance, and adhesion strength.

In addition to the above components, CCL also contains auxiliary materials such as release film, which is used to separate layers during lamination.

The selection of materials for each component determines the overall performance characteristics of the CCL. For example, the substrate material’s choice influences the mechanical strength, moisture resistance, and dielectric constant of the CCL. The choice of copper foil material affects electrical conductivity, flexibility, and thermal conductivity. The adhesive material choice impacts CCL strength, bonding properties, and temperature resistance. Thus, selecting the right type of materials for each component is essential for achieving optimal PCB performance.

Types of CCL

Copper clad laminate Types

Base on reinforcing material

Paper base CCL ( such as XPC)
Glass fiber cloth base CCL (such as FR-4, FR-5)
Compound CCL ( such as CEM-1, CEM-3)
Special material base CCL (such as metal-base CCL, ceramic-base CCL)

Base on applied insulation resin

Phenolic resin CCL (such as XPC, XXXPC, FR-1, FR-2, and so on)
Epoxy resin CCL (FR-3)
Polyester resin CCL

Base on performance

General performance CCL
CCL with high heat resistance
CCL with low dielectric constant
CCL with low CTE (Coefficient of Thermal Expansion)

Base on mechanical rigidity

Rigid Copper Clad Laminate
Flexible Copper Clad Laminate

Common CCL types and Properties

The mainstream CCL types on the market include rigid PCB CCL(FR-4, Aluminum Core CCL, Copper Core CCL, high-frequency materials with low dielectric constant, and mixed dielectric constant plates) and Flexible Copper Clad Laminate (FCCL).

Rigid PCB Copper Clad Laminate

Copper Clad Laminate, also known as PCB laminate, is an indispensable substrate material in the manufacturing of printed circuit boards. Its core feature is a thin layer of copper that is laminated on one or both sides of the board, giving rise to the common terms “single-sided CCL” and “double-sided CCL.”

During the production of rigid circuit boards, manufacturers rely heavily on specially designed rigid CCLs that are typically composed of substrate materials, such as resin epoxy (FR4), metal core (aluminum or copper), PTFE, and ceramic. These materials are used to fabricate various types of circuit boards, including single-, double-, and multi-layer circuits.

Thanks to its unique composition, CCLs play a crucial role in ensuring the rigidity, stability, and durability of PCBs, even in harsh operating environments. Manufacturers must therefore understand the characteristics and properties of each type of CCL material and select the most suitable one for their specific application.

Resin Epoxy FR-4 Copper Clad Laminate

FR-4 Copper Clad Laminate refers to a specific type of rigid PCB substrate material that has copper cladding on one or both sides of the base, which is made of a composite material comprised of woven fiberglass cloth bonded with an epoxy resin binder. The material is known for its flame-resistant properties, denoted by the “FR” abbreviation, yet it is important to note that compliance with the standard UL 94V-0 is not automatic and must be tested at a compliant lab according to Section 8 of UL 94 Vertical Flame testing. The term “FR-4” was coined by the National Electrical Manufacturers Association (NEMA) in 1968.

Due to its excellent electrical insulation properties and rigid structure, FR-4 CCL is widely used in the PCB industry for manufacturing printed circuit boards. The woven fiberglass cloth provides the necessary strength and stability, while the epoxy resin binder creates a strong bonding agent that secures the copper cladding to the base material. In addition to being an excellent electrical insulator, FR-4 CCL also offers good thermal conductivity properties, making it a popular choice for high-power applications.

FR-4 CCL is available in various thicknesses, copper weights, and sizes, and it can be classified into two main types: single-sided and double-sided. Single-sided FR-4 CCL has copper cladding on one side, while the other side remains unclad. Double-sided FR-4 CCL has copper cladding on both sides, with holes drilled through the substrate to allow the conductive paths to be routed between the two layers.

In summary, FR-4 CCL is a composite material that provides excellent electrical insulation and thermal conductivity properties, making it a popular choice for manufacturing printed circuit boards. Its flame-resistant properties, denoted by the “FR” abbreviation, make it a safer option for electronic devices that require high durability and reliability.

FR-4 Copper Clad Laminate Properties

Low glass transition temperature (Tg): Tg130°C – Tg140°C
Mid glass transition temperature (Tg): Tg150°C
High glass transition temperature (Tg): Tg170°C
High decomposition temperature (Td): Td>345°C
Dielectric constant (Dk or Er) at 1 GHz: 3.66-4.5
Dissipation factor (Df) at 1 GHz: 0.016
High UL rated flammability: 94V-0
Low coefficient of thermal expansion (CTE): 2.5%-3.8%
High comparative tracking index (CTI): CTI >=600V
Halogen-free
Compatible with standard and lead-free assembly
Available FR4 CCL thicknesses: 0.2mm to 3.2mm
Available copper foil weights: 1/3oz to 3oz

Aluminum Core Copper Clad Laminate

Aluminum core Copper Clad Laminate, also known as Aluminum base CCL, is a high-performance electronic substrate material made of an aluminum plate, a dielectric bonding layer, and a copper foil through a high-temperature hot pressing process. The metal layer in Aluminum core CCL provides excellent thermal conductivity, while the overall conductivity of the material is determined by the dielectric bonding layer. To further enhance its thermal conductivity, Aluminum core CCL can be filled with ceramic materials as the dielectric layer.

Most Aluminum PCB boards are built with a single-sided Copper Clad Laminate, while double-sided CCL are used for the manufacturing of double-sided Aluminum PCBs and multilayer hybrid Aluminum PCBs, which are a specialty at JHYPCB. With its excellent thermal conductivity and other advantageous properties, Aluminum core CCL has become an indispensable raw material in the production of high-performance electronic devices and is widely used in various industries.

Aluminum Core Copper Clad Laminate Properties

Thermal conductivity available in a range of values: 1.0W/m·K, 1.5W/m·K, 2.0W/m·K, 3.0W/m·K, 4.2W/m·K, 5.0W/m·K, and 7.0W/m·K
Aluminum alloy style available in 1060 (138 W/m·K) and 5052 (220 W/m·K)
Copper style available in C1100 (386 W/m·K) with copper thickness in the range of 0.5oz to 2oz
Glass Transition Temperature (Tg) available in Tg100oC, Tg120oC, and Tg130oC
Dielectric Constant (Dk or Er) measures at 4.8 (@1MHz) and is halogen-free
Compatible with standard and lead-free assembly
High UL Rated Flammability: 94V-0
Aluminum Core CCL thickness available from 0.8mm to 2.0mm

Copper Core Copper Clad Laminate

Copper Core CCL, likewise Aluminum Core CCL, is a composite material consisting of a copper plate, dielectric bonding layer, and copper foil. The thermal conductivity of Copper Core CCL is primarily determined by the dielectric bonding layer as well as the thermal dissipation design of the board.

Copper Core PCB, also known as copper substrate PCB, copper-based PCB, or copper-clad PCB, comes in three main design types:

Standard Copper Core PCB: circuitry is placed on the copper layer without plated-through holes (PTHs)
Chip on Board (COB) Copper PCB: where the IC chip is directly mounted onto the copper layer of the board, providing a small form factor
Direct Thermal Path Copper-based PCB: this type of PCB does not have an insulator layer under the thermal path pad, allowing for optimal thermal dissipation.

It is important to note that Copper Core PCBs have a higher thermal conductivity than FR-4 PCBs, which makes them a popular choice for high-power applications where heat dissipation is critical. Copper Core PCBs are also used in electronic devices that require reliable operation in harsh environments, such as aerospace, automotive, and military applications.

Copper Core Copper Clad Laminate Properties

Thermal Conductivity: available options include 3.0W/m·K, 5.0W/m·K, and 7.0W/m·K.
Copper (Cu) Style: typically made with C1100 copper, which has a thermal conductivity of 386 W/m·K.
Copper thickness: available from 0.5oz to 2oz.
Glass Transition Temperature (Tg): available options include Tg100oC, Tg120oC, and Tg130oC.
Dielectric Constant (Dk or Er) (@1MHz): typically around 4.8.
Halogen-free: Yes.
Assembly Compatibility: compatible with both standard and lead-free assembly.
Flammability: High UL Rated Flammability: 94V-0.
Copper Core CCL thickness: available from 0.8mm to 2.0mm.

High-frequency Materials with Low Dielectric Constant

High-frequency materials with low dielectric constant are a type of copper-clad laminate used in the manufacturing of PCBs for high-frequency circuits.

These materials have a low dielectric constant, meaning that they have a relatively low capacitance and can therefore transmit high-frequency signals with minimal signal loss. High-frequency materials with low dielectric constant are specifically designed to maintain stable electrical performance even at higher frequencies, resulting in significantly reduced signal loss and crosstalk in comparison to PCBs made with traditional FR-4 CCLs.

Other key characteristics that define CCL and prepreg (PP) performance for microwave/RF printed circuit boards, in addition to dielectric constant (Dk), include dissipation factor (Df), coefficient of thermal expansion (CTE), thermal coefficient of dielectric constant (TCDR) and thermal conductivity. Different materials may have varying levels of these characteristics, which need to be considered when selecting the appropriate material for a given application.

PTFE (Polytetrafluoroethylene), which is a synthetic thermoplastic fluoropolymer, is a high-frequency material commonly used in PCB designs at microwave frequencies. PTFE has excellent dielectric properties at microwave frequencies, making it ideal for use in high-frequency PCBs. Despite this, it isn’t always the best choice as it can be quite expensive and have some processing limitations.

When selecting a material, it’s important to consider the specific requirements of the application, including frequency, signal power, dielectric constant, dissipation factor, thermal conductivity, and cost. Working with experienced material suppliers who are able to provide detailed information about the specific characteristics of their materials, as well as their processing requirements, is vital to achieving optimal performance.

Properties of High-frequency Materials with Low Dielectric Constant

Low dielectric constant: One of the most important properties of high-frequency materials with low dielectric constant is that they have a low dielectric constant. This means that they are able to minimize signal loss, which is crucial in high-frequency applications.
Low loss tangent: Another key property of high-frequency materials with low dielectric constant is that they have a low loss tangent. This means that they are able to minimize energy dissipation in electrical circuits, leading to improved signal integrity and reduced interference.
High thermal stability: High-frequency materials with low dielectric constant generally have high thermal stability, which means that they can withstand high temperatures without any significant degradation of their electrical properties.
Low water absorption: High-frequency materials with low dielectric constant tend to have low water absorption, which is important for maintaining their electrical properties in humid conditions.
Good dimensional stability: High-frequency materials with low dielectric constant also exhibit good dimensional stability, which means that their physical size and shape remain constant over a wide range of operating temperatures and environmental conditions.
Good mechanical strength: Many high-frequency materials with low dielectric constant are also characterized by good mechanical strength, which makes them more resistant to damage, warping, and other physical stress.

Flexible Copper Clad Laminate

Flexible Copper Clad Laminate (FCCL) is a specially designed type of Copper Clad Laminate that is commonly used in manufacturing flexible PCBs. It is created by laminating a layer of copper foil to a flexible core material, such as polyimide or polyester film.

FCCL is highly preferred in modern electronics for its ability to lend flexibility and conformability to the PCBs. The flexible nature of FCCL allows it to be easily bent or curved to suit various applications. The flexibility of FCCL is unparalleled, providing an opportunity to create new and innovative devices that traditional rigid PCBs cannot achieve.

Due to its remarkable properties, FCCL has found wide application in various sectors, such as the aerospace, automotive, and medical fields. In the automotive industry, for example, FCCL is used to manufacture sensors, antennas, and dashboards, where the flexible nature of FCCL allows it to conform easily to the shape of the dashboard. In the medical industry, FCCL is used to make medical devices that require bending or twisting to fit inside the body.

FCCL is a versatile and valuable material that has been instrumental in the development and evolution of modern electronic devices. With its flexibility and conformability, FCCL has enabled the creation of innovative and unique products that are beyond the scope of traditional rigid PCBs. Therefore, when developing devices that require bending and curving, FCCL is an ideal solution for high-performance and cost-effective flexible PCBs.

Properties of FCCL

Flexibility: FCCL has excellent flexibility and can be bent or molded to fit a variety of shapes and forms.
Pliability: FCCL is also highly pliable, which means that it can be easily formed or reshaped to fit specific applications.
Low Dielectric Constant: With a low dielectric constant, FCCL is ideal for high-speed digital circuits, signals and frequencies.
Thermal Stability: FCCL has excellent thermal stability, which ensures reliable performance in high temperature environments.
High Tensile Strength: FCCL can withstand significant amounts of tension and stress, which makes it ideal for use in harsh environments such as aerospace and automotive industries.
Easy to Manufacture: FCCL is relatively easy to manufacture compared to other high-performance materials. It can be produced through several methods, including etching, lamination and coating.

Manufacturing process of Copper Clad Laminate

The manufacturing process of Copper Clad Laminate involves a series of steps that ensure the production of a reliable and efficient product. The following is a detailed description of the process.

The first step is to prepare the base material. The material used for CCL is typically fiberglass cloth, which is impregnated with resin and dried. The resin used is usually an epoxy or phenolic resin, which provides the required mechanical and electrical properties to the product.
The next step is to clean the surface of the base material to remove any impurities or contaminants. This is done using a chemical cleaning process that involves the use of various solvents and acids.
The base material is then coated with a layer of copper foil, which is usually around 18-35 microns thick. The copper foil is bonded to the base material using an adhesive layer, which can be either a thermally set or a UV-curable adhesive.

The above picture is the production flow chart of copper clad laminate, and the following is the specific process represented by each code in the production process.

1. glass fiber cloth
2. gluing unit
3. resin mixing
4. mixing machine
5. additives / solvent / resin
6. dryer
7. prepreg
8. cutting machine
9. sheet prepreg
10. layer distributor
11. pre-layup prepreg
12. rolled copper foil

13. cutting machine
14. sheet copper foil
15. CCL lay-up system
16. steel plate
17. hot press
18. steel plate cleanser with high speed
19. CCL break-down system
20. steel plate
21. CCL
22. packaging machine
23. CCL layups

Critical Factors to Consider When Selecting Copper Clad Laminates for PCB Manufacturing

When selecting copper clad laminates, there are several factors that should be taken into account. Among these factors, the most critical ones are:

Electrical Performance: The electrical properties of the CCL like its conductivity, and dielectric properties, are vital for signal transmission to be effective.
Mechanical Stability: The mechanical strength of the CCL is critical for the reliability and longevity of the PCB. Factors to consider include its flexibility, dimensional strength, and resistance to damage.
Thermal Stability: The thermal stability of the CCL is crucial for the PCB’s reliability, particularly in high-temperature applications.
Chemical Resistance: The chemical resistance of the CCL must be considered in harsh environmental conditions to ensure that it can withstand exposure to chemicals and moisture.
Cost: The cost of the CCL can impact the overall cost of the PCB, so it’s necessary to factor in the budgetary constraints.
Manufacturing Processes: The manufacturing processes involved in producing the CCL should be considered, including customizability, surface finish, and thickness.
Environmental Requirements: The application’s environmental requirements should also be taken into account, including toxicity and flame resistance.

By taking these factors into account, one can select a Copper Clad Laminate that provides the ideal combination of electrical performance, mechanical stability, thermal stability, and resistance against harsh chemicals and environmental conditions.

Copper Clad Laminate FAQs

What is copper clad laminate?

Copper clad laminate (CCL) is a composite material made of a copper layer laminated onto a substrate material, such as fiberglass, to create a printed circuit board (PCB).

What are the common types of copper clad laminate?

The most common types of copper clad laminate are FR-4, CEM-1, and CEM-3.

What are the applications of copper clad laminate in PCBs?

Copper clad laminate is used as the base material for PCBs, which are used in a wide range of electronic devices, including computers, smartphones, and televisions.

What are the electrical properties of copper clad laminate?

Copper clad laminate has good electrical conductivity and low dielectric constant, making it ideal for use in high-frequency applications.

What are the mechanical properties of copper clad laminate?

Copper clad laminate has good strength, stiffness, and resistance to bending and twisting.

What are the thermal properties of copper clad laminate?

Copper clad laminate has good thermal conductivity and low thermal expansion, making it suitable for use in high-temperature applications.

What factors should be considered when selecting copper clad laminate?

Factors to consider when selecting copper clad laminate include the electrical properties, mechanical stability, thermal stability, chemical resistance, cost, manufacturing process, and environmental requirements.

What is the role of copper in copper clad laminate?

Copper provides the electrical conductivity for the PCB and allows electrical signals to flow through the circuit.

What is the role of laminate in a PCB?

The laminate material provides the mechanical support and stability for the copper layer and helps to maintain the circuit pattern.

What is the difference between FR-4 and CEM-1 copper clad laminate?

FR-4 has higher mechanical strength and better resistance to moisture and chemicals, while CEM-1 has lower cost and better thermal conductivity.

What is the difference between copper foil and copper clad laminate?

Copper foil is a thin sheet of copper that is used as the conductive layer in a PCB, while copper clad laminate consists of a copper layer laminated onto a substrate material.

What are the benefits of using copper clad laminate in PCBs?

The benefits of using copper clad laminate in PCBs include good electrical conductivity, mechanical stability, thermal stability, and chemical resistance.

How is the copper layer attached to the substrate material in copper clad laminate?

The copper layer is attached to the substrate material through a process called lamination, which involves applying heat and pressure to bond the two materials together.

What are the disadvantages of using copper clad laminate in PCBs?

The disadvantages of using copper clad laminate in PCBs include the potential for delamination, the risk of corrosion, and the cost of materials and manufacturing.

What is the thickness of the copper layer in copper clad laminate?

The thickness of the copper layer in copper clad laminate can vary depending on the application, but is typically between 0.5 and 2 ounces per square foot.

How is the copper layer patterned in copper clad laminate?

The copper layer is patterned through a process called etching, which involves using a chemical solution to remove the unwanted copper and leave the desired circuit pattern.

What is the difference between single-sided and double-sided copper clad laminate?

Single-sided copper clad laminate has a copper layer on one side of the substrate material, while double-sided copper clad laminate has copper layers on both sides.

What is the maximum operating temperature of copper clad laminate?

The maximum operating temperature of copper clad laminate depends on the specific material used, but is typically between 130°C and 180°C.

What is the shelf life of copper clad laminate?

The shelf life of copper clad laminate varies depending on the specific material used, but is typically between 6 months and 1 year.