A Complete Introduction To Copper Clad Laminate (CCL) (2022)

Copper Clad Laminate (CCL) is the material on which all circuitry and printed circuit boards (PCBs) are based. It is the basic material used in the PCB industry with wide applications in consumer electronics (e.g. radio and television), mobile communication industry, computers, avionics, military hardware, and others. The copper-clad laminate manufacturing industry is a growing industry with huge development prospects as a result of development and innovation in mobile communication technology, consumer and industrial electronics, semiconductor manufacturing technology, PCB manufacturing technology, and surface mounting technology, especially in China and Southeast Asia.

A Complete Introduction To Copper Clad Laminate (CCL)

Table of Contents

1. What Is Copper-Clad Laminate?

Copper Clad Laminate is an insulating plate coated or cladded with copper foil and produced by stacking an impregnated (prepreg) sheet of resin over a substrate (the base material) suchlike glass or paper, under high temperature and pressure. It is the basis of every circuit and PCB. When used in the manufacturing of multi-layer PCBs, it is known also as a CORE. The printed circuit board manufactured from CCL is a combination of conducting and insulating layers, vials, pads of copper tracks, holes, and other components.

Copper clad laminate consists basically of a glass fiber substrate laminated using copper foils and epoxy resins. The glass fiber can also be termed “prepreg” because it is integrated with epoxy resin. The glass fiber alongside other substrate materials such as glass, paper, fiber cloth, and water pulp is generally known as reinforcing materials. Copper clad laminate is the most commonly and significantly used substrate in the fabrication of PCBs. It is now being used in most PCBs, whether for industrial circuit boards or consumer electronics.

Glass-fabric and paper-based copper clad laminate are two of the major products (by output) in this market segment, contributing about 61% and 17% respectively of entire China’s CCL in 2013. The CCL industry has grown significantly and innovatively in the past years with Southeast Asia and China having the fastest growth and development. Key manufacturers in the industry globally have consequently taken measures such as product transformation and capacity expansion to strengthen the business of copper clad laminate production. The output of the world’s copper clad laminate in 2013 saw an annual increase of about 17.9% to 720,000,000 square meters, mainly from Asia (about 95.6%); particularly China, which produces a copper clad laminate with an output of 480,000,000 square meters in the same year, which is an increase of 6.8% from the previous year, accounting for about 67% of world production.

Copper clad laminate has a wide range of applications including:

  • Consumer electronics circuit board
  • High-speed mobile communications such as smartphones, 5G, and 4G-LTE base stations antenna equipment.
  • Automotive industry such as in Advanced Driver Assistance Systems (ADAS)
  • Avionics (Radar communications)
  • Electric power generation
  • Welded tanks
  • Sheathing of Offshore platform
  • Shipbuilding
  • Steam condensers
  • Hydraulic bushings
  • Heat exchangers
  • Pressure vessels
  • Nuclear materials storage
  • Desalination plants
  • Missile components
  • Wearable parts of expansion joints
  • Metal casting molds and dies
  • Oil exploration and others

The quality and performance of a copper clad laminate are dependent on the below factors and should be done by PCB Fabrication Houses.

  • Size: Given that copper clad laminates are the base or substrate material for PCBs, they must be made according to specific size requirements that correspond with the PCB. Parameters to be considered include the length, breadth, warpage, and diagonal deviation; each of these parameters must meet specific standards.
  • Appearance: A copper clad laminate of syndrome quality must be plain, sleek, and polished in appearance. Scratch, dent, bubble, pinhole, wrinkle, or resin point on the copper foil during production can reduce the performance of the copper clad laminate and PCB.
  • Physical performance: A copper clad laminate physical performance can be affected by these parameters: dimensional stability, bending strength, peel strength, punching quality, heat resistance namely thermal stress, Time to delamination-T300, T288, and T388, and others.
  • Chemical performance: The chemical performance of copper clad laminates must meet these requirements: resistance to chemical reagents, flammability, Z-CTE (Z-axis Coefficient of Thermal Expansion), Glass transition temperature (Tg) for mechanical stability, dimensional stability, and others.
  • Electric performance: This quality and performance are important for PCBs and the copper clad laminate must be designed for the best electric performance to meet the required standards such as Dielectric Constant (Dk), Surface Resistance, Volume Resistance, Dielectric Loss Tangent (Df), Dielectric Breakdown Voltage, Comparative Tracking Index (CTI), Electric Strength, etc.
  • Environmental performance: A copper clad laminate must also meet certain environmental requirements like eco-emissions, water absorption, etc.

2. Copper Clad Laminate Classifications And Materials

Copper clad laminates are grouped into different categories as follows:

  • Based on the mechanical rigidity of copper-clad laminate: Copper clad laminates exist in two types based on this classification: Rigid CCL and Flex CCL. Examples of Rigid CCL are FR-4 and CEM-1. CEM-1 is a composite material consisting of paper core and woven glass fiber surfaces mixed with epoxy resin and used mainly in the PCB industry; with great electrical properties and higher flexing strength than paper-based materials. FR-4 (Flame Retardant-4) is a material consisting of a woven glass fiber cloth and an epoxy resin laminate material that is self-extinguishing (flame resistant). Rigid PCBs make use of rigid CCLs whereas flexible PCBs use flex CCLs. The rigid-flexible PCB contains both flex CCL and rigid CCLs.
  • According to insulating materials and structures: Under this classification, we have metal-base CCL, organic resins CCL (e.g. CEM-3), ceramics-base CCL, and others.
  • According to the thickness of the CCL: With this classification, we have thin and standard thickness CCLs. Thin CCL requires at most 0.5mm thinness is while the other required at least a thickness of 0.5mm. The thickness of the copper foil is not included in the CCL’s thickness.
  • According to the types of reinforcing materials: In this case, we have paper-based CCL (suchlike XPC); fiberglass cloth-focused CCL (suchlike FR-5 and FR-4); Compound CCL (suchlike CEM-1 and CEM-3); and Specialized material-base CCL (suchlike metal–base CCL, ceramic – base CCL, and others).
  • According to applied insulation resin: The types of CCL under this classification are Phenolic resin CCL (such as XPC, FR-1, FR-2, and XXXPC); Epoxy resins CCL (such as FR-3); and Polyester resin CCL.
  • According to the performance of the CCL: Under this category, we have these types of CCL: General performance CCL; low dielectric constants CCL; CCL with high-temperature resistance; and CCL with low Coefficient of Thermal Expansion (CTE).

2.1 Rigid PCB CCL

Rigid PCB Copper Clad Laminate is also known as PCB laminate is a kind of substrate material used in PCBs containing a tiny layer of copper lamination on any side (single CCL) or both sides (double CCL) of the PCB. Substrate materials like FR-4 (epoxy resin), PTFE (Polytetrafluoroethylene), Ceramic, and metal core (copper or aluminum) are used by manufacturers to fabricate multi, double, and single-layer rigid PCBs.

FR-4 copper clad laminate

2.1.1 Copper Core CCL

Copper Core CCL contains copper foils, a copper plate, and a dielectric bonding layer. Its thermal conductivity depends on the dielectric bonding layer and if the PCB design is thermally effective in dissipating heat. Copper-based PCBs are of three main types namely:

  • Chip on Board (COB) copper PCB
  • Common copper core PCB (having circuitry on a copper layer with no Plated-Through holes (PTH).
  • Direct thermal path copper-based PCB (without insulator beneath the thermal path pad)

Characteristics of Copper Core CCL:

  • Copper thickness from 0.5oz to 2oz is available.
  • Copper Core CCL thickness from 0.8mm to 2.0mm is available.
  • Thermal Conductivity: 7.0W/m·K, 5.0W/m·K, 3.0W/m·K
  • Dielectric Constant (Er or Dk) of 4.8 at 1MHz 4.8
  • Copper (Cu) Style: C1100 (386 W/m·K)
  • Glass Transition Temperature (Tg): Tg130°C, Tg120°C, and Tg100°C
  • Compatible with zero lead and standard assembly
  • Halogen-free
  • High UL-Rated Flammability: 94V-0

2.1.2 FR-4 CCL

FR-4 Copper Clad Laminates are rigid PCB substrate materials with copper cladding on either side or both sides of the FR-4 substrate. FR-4 (Flame Retardant-4) is a material consisting of a woven glass fiber cloth and an epoxy resin laminate material that is self-extinguishing (flame resistant).

Properties of FR-4 CCL:

Characteristics of FR-4 CCL

  • High, Mid, and Low Glass Transition Temperature of Tg150°C, Tg170°C, and Tg130°C to Tg140°C respectively.
  • High Comparative Tracking Index (CTI) of at least 600V.
  • High Temperature of Decomposition (Td) greater than 345°C
  • Dielectric Constant of (Dk or Er) 3.66-4.5 (@1GHz)
  • Dissipation factor (Df) of 0.016 (@1GHz)
  • High UL-Rated Flammability of 94V-0
  • Low CTE of 2.5%-3.8%
  • Halogen-free
  • Compatible with zero-lead and standard assembly.
  • FR4 CCL thickness from 0.2mm to 3.2mm is available.
  • Copper thickness from 0.33oz to 3oz

2.1.3 Aluminum Core CCL

Aluminum (Alu) core or base copper clad laminates are consists of copper foil, aluminum plate, and dielectric bonding layer under high pressure and temperature. The metallic layers have high thermal conductivity and the conductivity of the Aluminum core laminate depends on the dielectric bonding layer. With its high thermal conductivity, ceramic can be used as a dielectric. Most aluminum PCBs are designed with one-sided CCL; double-sided Alu PCBs are made with double-sided CCL and multi-layer hybrid Alu PCBs can be also produced.

Properties of Aluminum Core CCL:

  • Thermal conductivity: 7.0W/m·K, 5.0W/m·K, 4.2W/m·K, 3.0W/m·K, 2.0W/m·K, 1.5W/m·K, and 1.0W/m·K.
  • Copper thickness available from 0.5oz to 2oz
  • Aluminum (Al) Alloy Style: 5052 (220 W/m·K) and 1060 (138 W/m·K)
  • Copper (Cu) Style: C1100 (386 W/m·K)
  • Glass Transition Temperature (Tg): Tg130°C, Tg120°C, and Tg100°C
  • Dielectric Constant (Dk or Er) of 4.8 @1MHz
  • Compatible with zero-lead and standard assembly
  • Halogen-free
  • High UL-Rated Flammability: 94V-0
  • Aluminum Core CCL thickness from 0.8mm to 2.0mm is available

2.2 Flexible CCL (FCCL)

Flexible Copper Clad Laminate

Flexible CCLs are used in flexible PCBs FCCL is composed of layers of polyimide and copper foil which serve as an insulator and an electrical conductor respectively. FCCL can be single-sided or double-sided with copper fools on either side and both sides respectively. In terms of the adhesive that exist between copper foil and polyimide, FCCLs are divided into:

  • Adhesive FCCL
  • Non-Adhesive FCCL

Both double-sided and single-sided FCCLs without or with adhesive are used in fabricating flexible PCBs.

Characteristics of FCCL

  • Good peel strength and dimensional stability at high temperature 
  • Excellent flexing strength
  • UL-certified product
  • Good resin flow stability
  • Halogen-free
  • Eco-friendly
  • Combination of various copper clad and thickness (Non-adhesive FCCL)
  • Good heat-resistance capacity
  • Excellent adhesive property (adhesive FCCL)

2.3 Special Copper Clad Laminates

Special copper clad laminates include ceramic CCLs and other metal-base CCLs. They are used in fabricating ceramic PCBs. Ceramic PCBs are thermally conductive organic ceramic circuit boards that have a thermal conductivity of 9-20W/m.K manufactured under a temperature of less than 250°C with thermally conductive using organic adhesive and ceramic powder. Ceramic CCLs (by substrate material) used in various ceramic PCBs include:

  • Aluminum Nitride (150-180 W/m.K thermal conductivity)
  • Aluminum Oxide (18-36 W/m.K thermal conductivity)
  • Beryllium Oxide (184-300 W/m.K thermal conductivity)
  • Boron Nitride (15-600 W/m.K thermal conductivity)
  • Silicon Carbide (70-210 W/m.K thermal conductivity)

2.3.1 RF/Microwave PCB CCL

PCBs are designed at microwave frequencies. The basic features of RF/Microwave PCB CCLs and prepreg performance are defined by dielectric constant, dissipation factor, coefficient of thermal expansion, thermal coefficient of dielectric constant, and thermal conductivity. The most common high-frequency CCL material for manufacturers and designers are PTFE with great dielectric characteristics at microwave frequencies

These four CCL companies below produce high-frequency CCL materials:

  • Isola High-Performance PCB laminates
  • Rogers Advance Laminates for RF/Microwave Designs
  • Taconic Advanced PCB Dielectric Laminates
  • Panasonic MEGTRON 6

2.3.2 Halogen-free CCLs

Halogen-free CCL is a new trend in CCL design to meet Restriction of Hazard-based Substances (RoHS) regulations with higher requirements such as reliability and heat resistance. In Halogen-free CCLs, Chlorine and Bromine contents are controlled around 900ppm with their total content not greater than 1500ppm.

Characteristics of Halogen-free CCL

  • High UL-Rated Flammability of 94V-0
  • Great heat performance
  • Excellent size stability
  • Thermal decomposition is greater than 320°C
  • Time to delamination (T260) >30 mins -the time taken for the PCB substrate material to delaminate when under a temperature of 260°C.
  • RoHS compliant
  • Good mechanical properties
  • Excellent flexing capacity

2.3.3 Zero Lead CCL

Zero-lead CCLs are copper cladded PCBs where surface mountings are done without applying zero-lead solders. Brominated epoxy resin is the major resin of zero lead CCLs. According to RoHS regulations, six items including PBDE and PBB are not used any longer in CCLs. Phenol-formaldehyde resin is used as a curing agent in zero lead CCLs.

Characteristics of Zero Lead CCLs with PN curing systems

  • Great thermal performance
  • Good CAF (Conductive Anodic Filament) resistance
  • Good water absorption resistance
  • Heat decomposition temp >320°C
  • Time to delamination (T260) > 30 mins

3. Characteristics of Copper Clad Laminates

Below are the characteristics of Copper Clad Laminates are:

  • High peel and tear strength
  • Extensive processing latitude
  • Great thermal resistance
  • Great dielectric thickness tolerance
  • High coefficient for reliable Chip-on-Flex (COF) wire bonding
  • High flexing strength
  • Low water absorption
  • Excellent dimensional stability

4. The Copper clad Laminate Manufacturing Process

Copper Clad Laminate manufacturing process involves the use of a prepreg-a reinforcing material-impregnated already with a resin that contains the right curing agent. The resin exists in pre-dried and unhardened form. The prepreg is heated and placed in a mold and inserted or sandwiched between two layers of copper foils. Additional resin can be added also. Subjecting this combination of copper foils and prepreg to heat enables the resin to flow and the prepreg to stick to the copper foil. Increasing the temperature and pressure further is necessary for bonding the prepreg to the copper foil.

5. CCL Brand And Manufacturers

CCL brand and manufacturers include:

  • Golden Max International Technology Ltd (GDM) owner of two copper-clad laminate brands: ILM and GEM. ILM is one of the highest quality copper-clad laminate brands in the industry.
  • Isola High-Performance PCB laminates
  • Rogers Advance Laminates for RF/Microwave Designs
  • Taconic Advanced PCB Dielectric Laminates
  • Panasonic MEGTRON 6
  • AGC Hub
  • DK Enterprises
  • PS Electronics
  • DD Enterprises
  • SMTnet
  • Huizhou Green Mark Photoelectric Technology Company
  • Signour Laminates ( India ) PVT Ltd
  • FRX Polymers and others

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