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Copper Clad Laminate (CCL)

Article Catalog

1. What is Copper Clad Laminate?

2. Types of Copper Clad Laminates

3. Benefits of Copper Clad Laminate.

4. Composition of Copper Clad Laminate

5. What is the function of copper clad board?

6. Where can copper clad laminate be used?

7. Difference Between the Laminate and Prepreg

8. Manufacturing Process of Copper Clad Laminate

9. Conclusion

1. What is Copper Clad Laminate?

Copper Clad Laminate (CCL) is a plate-shaped material made by impregnating electronic fiberglass cloth or other reinforcing materials with resin, covering one or both sides with copper foil and hot pressing, referred to as Copper clad laminate.

Three golden copper-clad boards

Three golden copper-clad boards

Various printed circuit boards of different forms and functions are selectively processed, etched, drilled, and copper plated on copper-clad boards to produce different printed circuits. The printed circuit board mainly plays the role of interconnection, insulation and support, and has a great impact on the transmission speed, energy loss and characteristic impedance of the signal in the circuit. Therefore, the performance, quality and manufacturing of the printed circuit board The processability, manufacturing level, manufacturing cost, and long-term reliability and stability depend largely on the copper clad laminate.

2. Types of Copper Clad Laminates

Copper Clad Laminates (CCLs) are a type of material used in the manufacturing of printed circuit boards (PCBs). They consist of an insulating layer, such as fiberglass or epoxy resin, that is covered with a thin layer of copper on one or both sides. There are several types of CCLs based on different characteristics:

  1. By Mechanical Rigidity:

    • Rigid Copper Clad Laminates: These are typically used in devices like desktop computers and servers.

    • Flexible Copper Clad Laminates: Due to their flexibility, they're primarily used in foldable or bendable devices such as smartphones and wearable devices.

  2. By Insulating Material/Structure:

    • Organic Resin-based CCLs: Examples include FR-4 (glass fiber epoxy resin), CEM series (composite epoxy materials), etc.

    • Metal-Based CCLs: They are mainly used in LED lighting fixtures and automotive electronic products because they can dissipate heat well.

    • Ceramic-Based CCLs: With extremely low dielectric loss and high frequency stability, they are often applied in microwave radio frequency fields.

  3. By Thickness:

    • Thick plate (0.8~3.2mm including Cu)

    • Thin plate (<0.78mm excluding Cu)

  4. By Reinforcing Material

    • Glass cloth based

    • Paper-based – Composite base(CME-1、CME-2)

  5. Flame Retardancy Level
    According to UL standards(UL94、UL746E etc.), the flame retardant levels of rigid copper clad laminate can be divided into four categories : UL-94V0 level; UL-94V1 level; UL-94V2 level as well as UL-94HB level.

  6. Other classification methods also include by reinforcing material(e.g., paper or glass fiber), insulating resins used(e.g., phenolic or epoxy), special functionality (e.g., high temperature resistance or low dielectric constant ), and Coefficient of Thermal Expansion(CTE).

1) FR-4

FR-4 is a grade designation for flame-retardant material that complies with the highest standard, UL94 V-0, according to the Underwriters Laboratories (UL) flammability ratings. This term was coined by NEMA in 1968 and refers specifically to an insulating epoxy glass fiber fabric used in manufacturing rigid printed circuit boards (PCBs). When you look at a rigid PCB board, the visible insulation part is this FR-4 epoxy glass fiber fabric.

When copper is laminated onto FR-4 material, it forms Copper Clad Laminate (CCL), also known as FR4 CCL. This combination constitutes the most common base material utilized in crafting bare PCBs due to its robust mechanical properties and high-quality electrical insulation. In a PCB structure, however, FR-4 only serves as the primary insulating backbone.

For creating double-sided or multilayered PCBs, additional materials like an FR-4 core, pre-preg (PP), and copper foil are required. These components are layered together under heat and pressure within lamination machines after trace etching processes have been completed.

2) FR-2

FR2 Copper Clad Laminate (CCL) is another type of base material used in the production of printed circuit boards (PCBs). The term "FR2" denotes that this material is flame retardant level 2. It's primarily composed of a phenolic resin binder and cellulose paper as reinforcement, which gives it different properties compared to FR4 CCL.

While not as popular or widely used as FR4 due to its lower thermal resistance and mechanical strength, FR2 CCL still finds applications in less demanding environments where cost-effectiveness is a priority. The copper layer laminated onto the FR2 substrate can be etched into specific patterns to create conductive pathways for electrical signals, similar to other types of PCBs.

3) CEM Series (CEM-1, CEM-3)

The CEM series of Copper Clad Laminates (CCL) are composite materials used for printed circuit boards (PCBs). The term "CEM" stands for Composite Epoxy Material. The two most common types in this series are CEM-1 and CEM-3.

  • CEM-1: CEM-1 is a type of laminate composed of a cellulose paper base impregnated with flame-retardant epoxy resin and clad with copper on one or both sides. It's often used in applications where cost-effectiveness is important, as it offers good mechanical strength and electrical properties at a lower price point than some other types of laminates, such as FR4.

  • CEM-3: On the other hand, CEM-3 has similar properties to FR4 but comes at a more affordable price. Its composition includes glass fibers combined with an epoxy resin binder that makes it flame retardant. Unlike FR4 which is typically opaque due to its woven cloth reinforcement, CEM-3 is white and slightly translucent because it uses non-woven glass fabric reinforcement.

Both these types are widely used in PCB manufacturing due to their favorable electrical characteristics, thermal resistance capabilities, and relative affordability compared to higher-end materials like FR4.

4) Metal Core Printed Circuit Boards (MCPCB)

Metal Core Printed Circuit Boards (MCPCBs), also known as thermal PCBs or metal-backed PCBs, are a type of PCB that contains a base metal material. The purpose of the metal core is to divert heat away from critical board components and to less crucial areas such as the metallic core or heatsink backing.

Flexible copper clad laminate can be bent

Metal Core Printed Circuit Boards

The most common type of MCPCB involves the use of aluminum alloys, but other metals like copper can be used for better performance. These boards are especially useful in high power applications where heat dissipation can be critical for component function and lifespan.

An MCPCB typically consists of four layers:

  • Component Layer: This is the top layer where all components are soldered on.

  • Dielectric Layer: A non-conductive layer designed to provide electrical isolation while still allowing heat transfer.

  • Base Metal Layer: Usually made from aluminum or copper, this layer helps dissipate heat.

  • Backside Layer: Often just an additional protective coating, but it may also include more circuitry depending on design needs.

MCPCBs find extensive application in LED technology (for lighting and backlighting) due to their ability to efficiently manage generated heat at high brightness levels. They're also used in power converters/supplies, automotive systems, RF applications and more - essentially any application that requires effective thermal management within electronic circuits.

5) High Frequency Copper Clad Laminate

High Frequency Copper Clad Laminate (HF CCL) is a type of material used in the manufacturing of printed circuit boards (PCBs) specifically designed for high-frequency circuits. These are often found in applications such as radio frequency (RF) and microwave systems, telecommunications, antennas, radar systems, etc.

High Frequency Copper Clad Laminate Structure Diagram

High Frequency Copper Clad Laminate Structure Diagram

The key characteristic of HF CCLs is their low dielectric constant (εr), also known as relative permittivity, and low dissipation factor. The dielectric constant relates to how much electrical energy can be stored in the material while the dissipation factor indicates how much energy will be lost during storage and release. Both these factors directly affect signal transmission speed and loss at high frequencies.

Materials commonly used for HF CCL include Polyphenylene Oxide (PPO), Polytetrafluoroethylene (PTFE or Teflon), Rogers materials like RO4350B or RO4003C among others.

In comparison with standard FR4 laminates:

  1. Performance: At higher frequencies (>2GHz typically), HF CCLs perform better due to lower signal loss.

  2. Cost: HF materials tend to be significantly more expensive than conventional FR4.

  3. Manufacturing Process: Some high-frequency materials require special handling or processing steps compared to standard PCB fabrication processes.

6) Flexible Copper Clad Laminates

Flexible Copper Clad Laminates (FCCLs) are a type of material used in the manufacturing of flexible printed circuit boards (FPCBs). They consist of an adhesive layer, a copper layer, and a polyimide film. The polyimide film provides excellent heat resistance, chemical resistance, and flexibility.

Flexible copper clad laminate can be bent

Flexible copper clad laminate

The main advantage of FCCLs is their ability to be bent or folded without breaking. This makes them ideal for use in small devices where space is limited or where components need to move or flex during operation.

There are two main types of FCCLs:

  • Adhesive-based FCCL: This consists of three layers - copper foil, adhesive layer and base film (usually Polyimide). The adhesive that's commonly used can be epoxy resin, acrylic resin etc.

  • Adhesiveless FCCL: In this type there's no separate adhesive layer; instead the copper foil is directly bonded onto the base film through a special process. Adhesiveless laminates have better dimensional stability and thermal endurance than those with adhesives.

7) PTFE Based Copper Clad Laminates

Polytetrafluoroethylene (PTFE) based Copper Clad Laminates are specialized materials used in the fabrication of high-frequency printed circuit boards (PCBs). These laminates are particularly valued in applications that demand fast and efficient signal transmission. The PTFE fluoropolymer offers a low dielectric constant, minimizing signal loss and facilitating rapid signaling. Its low dissipation factor means less energy is lost as heat during operation, while its chemical resistance ensures durability across various environments.

However, there are challenges linked to using PTFE-based laminates. They tend to be more expensive than other types like FR4 due to their superior performance characteristics at higher frequencies (> 2GHz typically). Additionally, achieving good adhesion between copper and the non-stick PTFE substrate during manufacturing can be difficult without special treatment methods such as plasma etching or chemical roughening. Despite these hurdles, their use remains widespread in sectors like telecommunications equipment production, antenna design and microwave devices where maintaining high-frequency signal integrity is critical.

3. Benefits of copper clad laminate

Copper Clad Laminate (CCL) is a type of base material for printed circuit boards (PCB). It's made by reinforcing copper foil on one or both sides of an insulating substrate. The benefits of using Copper Clad Laminates in PCBs include:

  1. Electrical Conductivity: Copper has excellent electrical conductivity, which reduces the resistance to signal transmission and improves the overall performance of electronic devices.

  2. Thermal Conductivity: Copper also has good thermal conductivity that helps dissipate heat generated by components on the board, reducing overheating risks and improving device reliability.

  3. Mechanical Strength: The combination of copper and laminate provides mechanical strength to protect against bending and breaking while maintaining flexibility for design purposes.

  4. Etching Capability: Copper can be easily etched away during PCB production process to create complex circuit patterns necessary for modern electronics.

  5. Cost-Effective Production: CCLs are relatively cost-effective materials used in mass-production environments due to their ease-of-use in manufacturing processes like drilling, etching, etc., leading to lower costs per unit produced.

  6. Compatibility with Soldering Processes: Components are typically soldered onto the copper traces on a PCB, so having a copper layer makes this process easier and more reliable.

  7. Durability & Longevity: CCL-based PCBs tend to have long lifespans because they resist corrosion well; this makes them ideal for use in harsh environmental conditions where other types of boards might fail prematurely.

  8. Dimensional Stability: CCL offers stable dimensions even under changing temperatures or humidity levels - an important factor considering that many electronic devices operate under varying environmental conditions.

4. Composition of copper clad laminate

Copper Clad Laminate (CCL) is the primary material used in the manufacturing of Printed Circuit Boards (PCBs). It's composed of two main parts:

Copper clad laminate composition materials

Copper clad laminate composition materials

  1. Insulating Substrate: This forms the bulk of the laminate and provides mechanical strength, electrical insulation, and heat resistance to the PCB. The substrate can be made from various materials depending on its intended use. Common substrates include:

    • FR-4: This is a grade designation for glass-reinforced epoxy laminate sheets, tubes, rods and printed circuit boards (PCB). FR-4 is widely used because it's well balanced in terms of cost, availability, performance characteristics such as low water absorption and good chemical resistance.

    • Polyimide Films: Used for high temperature applications due to their excellent thermal stability.

    • Phenolic Cotton Paper Laminates: Generally cheaper but have lower performance specifications compared to FR-4 or Polyimide.

  2. Copper Foil: Copper foil is adhered onto one or both sides of this insulating substrate through a process known as lamination. The copper serves as conductive pathways for electronic signals when etched into specific patterns during PCB production.

The thicknesses of both components can vary based on requirements like flexibility/rigidity needs or signal transmission speed considerations.

In addition to these basic components, some CCLs may also contain filler materials that enhance properties like flame retardancy or thermal conductivity.

5. What is the function of copper clad board?

A Copper Clad Laminate (CCL), or copper clad board, is a fundamental material in the production of Printed Circuit Boards (PCBs). It serves several pivotal roles. Firstly, its copper layers form conductive pathways or "traces" when etched into specific patterns. These traces enable communication between different PCB components. Secondly, the CCL's substrate layer offers mechanical support and structural integrity for all mounted components.

Additionally, due to copper's excellent thermal conductivity properties, it aids in heat dissipation from various electronic components during operation—this helps prevent overheating and potential damage. The insulating substrate also provides electrical insulation by separating different layers of copper traces to avoid short-circuiting between them. Lastly, the surface of these boards is compatible with soldering processes typically used to attach electronic components onto it.

6. Where can copper clad laminate be used?

Copper Clad Laminates (CCLs) are primarily used as the base material for Printed Circuit Boards (PCBs), which are found in nearly every electronic device. Here are a few specific examples of where CCLs can be used:

  1. Consumer Electronics: Mobile phones, computers, televisions, gaming consoles and other home appliances all contain PCBs made from CCL.

  2. Industrial Equipment: Machinery controls, power equipment, automation systems often employ PCBs to manage electrical functions.

  3. Automotive Industry: Modern vehicles use numerous PCBs for engine control units, entertainment systems, navigation systems, safety features like airbags and anti-lock braking system etc.

  4. Aerospace & Defense Industries: Avionics systems in aircraft or spacecraft heavily rely on high-specification PCBs; defense applications may include communication devices or radar equipment.

  5. Medical Devices: Advanced medical devices such as imaging equipment (MRI machines), heart monitors and electric wheelchairs also utilize PCBs extensively.

6 .Telecommunications: Network hardware like routers ,switches ,servers have multiple complex multilayered printed circuit boards .

7 .LED Lighting Systems: Metal core printed circuit board(MCPCB) is commonly used in LED lighting system due to its superior heat dissipation capability .

8 .Wearable Technology: Flexible Copper Clad Laminates(FCCL) find their application here due to need of flexibility -like smartwatches ,fitness bands etc

The type of copper clad laminate used will depend on the requirements of the specific application &ndash; some might require a higher level of heat resistance or mechanical strength than others.

7. Difference between the laminate and prepreg

Copper clad laminate (CCL) and prepreg are both essential materials in the creation of multilayer printed circuit boards (PCBs), but they serve different purposes. Here are their main differences

 Copper Clad Laminate (CCL)Prepreg
DefinitionA base material used in PCBs that provides mechanical support and electrical insulation. It consists of an insulating layer, such as FR-4 or polyimide, clad with copper on one or both sides.Short for "pre-impregnated," it refers to fiberglass cloth that has been pre-impregnated with a resin system (usually epoxy-based). It's partially cured ("B-staged"), making it tacky at room temperature but able to fully cure under high heat during the lamination process.
Role in PCB ManufacturingForms the external layers where most components are mounted and conductive pathways or circuits are etched into its surface.Serves as an adhesive layer between two sheets of CCL in multilayer boards; when heated during lamination, it flows and hardens when cooled forming mechanically strong electrically insulating bond. Also provides electrical insulation between different layers within the PCB.
State before UseFully cured state which means they're rigid and not sticky at room temperature.B-stage state which means they're semi-cured making them flexible and tacky at room temperature.
Thermal PropertiesDepends on specific type but generally need to withstand soldering temperatures without significant degradation.Needs to be able to flow smoothly under heat & pressure then solidify upon cooling creating strong bonds.
Electrical PropertiesProvides good electrical insulation properties while also providing a conductive surface for circuit formation.Mainly serves as insulator preventing short circuits across multiple layers.
Mechanical Strength/StiffnessHigh mechanical strength needed since this forms structure of the board . Stiffer compared to prepreg due its fully cured nature.Lower stiffness than CCL due its semi-cured nature , however after final curing step becomes part of rigid assembly .

8. Manufacturing Process of Copper Clad Laminate

Copper clad laminate manufacturing process flow chart

Copper clad laminate manufacturing process flow chart

The manufacturing process of copper clad laminate (CCL) generally involves the following steps:

  1. Preparation of Insulating Material: The insulating material, often a type of glass fiber cloth such as FR-4, is prepared according to required dimensions.

  2. Impregnation: The insulating material is impregnated with resin. This step involves soaking the glass fibre in a specific resin solution (like epoxy). Once soaked, excess resin is removed leaving behind uniformly impregnated sheet.

  3. Drying and Curing: After impregnation, the material needs to be dried and partially cured ("B-staged"). This makes it rigid but still able to bond under heat and pressure.

  4. Lamination with Copper Foil: A layer of copper foil is then laminated onto one or both sides of this base material under high temperature and pressure conditions.The heat causes further curing of the resin making it solidify , simultaneously bonding strongly with copper creating a single unified structure .

  5. Cooling & Finishing : Post lamination assembly cools down , any extra bits are trimmed off , quality checks like visual inspection for defects or measurement for thickness etc are performed .

  6. Cutting : Finally large sheets can be cut into smaller sizes depending upon market requirements .

9. Conclusion

Copper Clad Laminate (CCL) and Prepreg are two essential materials used in the manufacturing of Printed Circuit Boards (PCBs).

CCL, which consists of an insulating layer clad with copper on one or both sides, forms the backbone of PCBs. It provides mechanical support and electrical insulation while also providing a conductive surface for circuit formation. The manufacturing process involves preparing the insulating material, impregnating it with resin, partially curing it ("B-staging"), laminating with copper foil under high temperature and pressure, followed by cooling and finishing.

Prepreg is a type of fiberglass cloth that has been pre-impregnated with a resin system. In its semi-cured state at room temperature before use, it's flexible and tacky but able to fully cure under heat during lamination process in PCB assembly. Its role is to serve as an adhesive layer between CCL sheets in multilayer boards while also providing additional electrical insulation.

Both CCLs and Prepreg have unique characteristics that make them indispensable for different stages in PCB production - from providing structural integrity to ensuring electrical functionality. Understanding their properties is crucial when designing complex electronics systems.

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Frequently Asked Questions

1. Where can Copper Clad Laminate Be Used?

Copper Clad Laminates (CCLs) are used extensively in the creation of Printed Circuit Boards (PCBs) for a wide range of electronics, including everyday devices, flexible circuits in compact gadgets, high-frequency applications like antennas and microwaves, automotive systems, aerospace & defense equipment, and medical devices.

2. What are the Three Layers of Copper Clad Board?

A copper clad board typically consists of three layers: the substrate (often made of fiberglass or other insulating material), a layer of adhesive to bond the materials, and a thin layer of copper that is used for creating electronic circuits.

3. What is CCL Material?

Copper Clad Laminate (CCL) is a type of material used in the electronics industry, composed of an insulating layer (often made from fiberglass or other similar materials), bonded with a thin layer of conductive copper, which serves as the foundation for creating printed circuit boards.

4. Why Choose Copper Cladding?

Copper is chosen for cladding due to its excellent electrical conductivity, ability to be etched into fine patterns, good heat dissipation properties, and compatibility with various manufacturing processes used in the production of printed circuit boards.

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