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What is Copper Clad Laminate Used for PCB

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Thur, Dec 24, 2020

What is Copper Clad Laminate

copper clad laminate

Copper clad laminate, abbreviated to CCL is a type of PCB material with glass fiber or wood pulp paper as reinforcing.

With the innovation and development of high-density electronic assemblies, the integration and assembly density of components on the boards are more and more power dissipated. If the substrates have poor dissipation, it will lead to the unreliability of the whole assembly.

The Printed circuit board (PCB) substrates are one of the most widely used to fabricate boards. They are kinds of material that soaks in resin, with the electronic glass fiber or other reinforcing material to contribute to the copper-clad on either of the sides of the board or even both. Copper clad laminate finds applications in radio, computers, television, mobile devices, and many electronic assemblies.

Types of Copper Clad Laminates

Each of the PCBs has its own requirements and specifications - designers or engineers responsible for the development of the assembly take under consideration all of these requirements. This is why we are going to review the different kinds of copper clad laminate used in the development of PCB.

There are two general types of copper clad laminate (CCL):

    Rigid Copper Clad Laminate

    As per the different insulation materials and division structure, the CCLs can be an organic raisin copper clad laminate, ceramic base copper-clad laminate, or metal-core copper laminate. If we also take the thickness under consideration, the CCL could be conventional copper-clad laminate or thin copper-clad laminate.

    The reinforcement materials used are paper base copper-clad laminates, electronic fiberglass cloth-based copper-clad laminates, and composite base copper clad laminates. According to the insulation resin used for the CCLs, they could be polyester resin copper-clad laminates, epoxy resin copper-clad laminates, and cyanate resin copper-clad laminates.

    Flexible Copper Clad Laminates

    Polyamide types can be flame retardant and non-flame retardant. They can also be very thin electronic fiberglass cloth copper-clad laminates and polyester, again, flame retardant and non-flame retardant.

Kinds of Copper Clad Laminate

Keep in mind that the two major types we’ve revealed above are the most commonly met in PCB electronics. The copper-clad laminates are not limited just to these two types. Now we are going to review more widely applied types of CCLs over the world.

We will also review some of their general properties such as flammability, flexural strength, coefficient of thermal expansion, Tg, and more.

1. CEM-3 (Composite Epoxy Materials Grade-3) is a fiberglass composite material developed on the FR0-4 basis, with a combination of woven glass fiber and non-woven glass plus core raisin filling. The color is usually milky white. The properties of CEM-3 are that it has lower mechanical endurance but is a cost-effective replacement for the other copper-clad laminate such as FR-4.

  • Flexural Strength - 300~400Mpa Lengthwise / 200~300Mpa Crosswise
  • Flammability - UL-94V0
  • Tg - ~130℃
  • Dielectric Constant @ 1MHz - 4.5~4.8
  • Coefficient of Thermal Expansion - ~55ppm/℃ before Tg / ~285ppm/℃ after Tg
  • Thermal Conductivity - Up to 0.8w/mk
  • Loss Tangent @ 1MHz - 0.020

2. FR-4 is the most popular copper-clad laminate used around the world. FR-4 has an impressive performance and is actually cheaper than some special materials. In the meantime, this material has been fully identified and studied, so it can now be modified to produce a variety of different helpful boards such as halogen-free type.

  • Flexural strength - 500~600Mpa lengthwise / 400~500Mpa crosswise
  • Flammability - UL-94V0
  • Dielectric constant @ 1MHz - ~4.7
  • Coefficient of thermal expansion - ~55ppm/℃ before Tg / ~285ppm/℃ after Tg
  • Thermal conductivity - up to 0.8w/mk

3. Aluminum is another common material used for the manufacturing of printed circuit boards. It is popular and widely used in high-power and LED products due to its impressive dissipation capabilities.

  • Flexural strength - ~450Mpa lengthwise / ~390Mpa crosswise
  • Flammability - UL-94V0
  • Dielectric breakdown - 6.0KV
  • Coefficient of thermal xxpansion - ~27ppm/℃ before Tg / ~30ppm/℃ after Tg
  • Thermal conductivity - 1.0~3.0w/mk

4. Polyimide (PI) is one of the top heat-resistant high molecular organic polymers. It is efficient for its softness, and it is the main material used for the manufacturing of flexible printed boards.

  • Flammability - UL-94V0
  • Tensile strength - ~72Mpa
  • Coefficient of thermal expansion - ~55ppm/℃ before Tg / ~149ppm/℃ after Tg
  • Tg - >250℃
  • Dielectric constant @ 1MHz - 4.2
  • Loss tangent @ 1MHz - 0.018
  • Thermal conductivity - ~0.2w/mk

5. Poly Tetrafluoroethylene (PTFE) or "Teflon" is a synthetic polymer material that has better dielectric properties when compared to conventional high-frequency materials. It is an excellent solution for special or demanding microwave/RF products. The only concern here is the expensive price that the manufacturers have to consider carefully.

  • Flammability - UL-94V0
  • Flexural strength - >276Mpa lengthwise / >241Mpa crosswise
  • Coefficient of thermal expansion - 70ppm/℃
  • Tg - >280℃
  • Loss tangent @ 1MHz - 0.003
  • Thermal conductivity - 0.24w/mk

In general, electronics have a lot to do in each copper-clad laminate, and they also include FR-½, 22F, CEM-1, and other substrates.

Copper Clad Laminate Materials

Prepreg- A prepreg (comes from pre-impregnated) is basically fiberglass impregnated with resin. The raisin has to be dried beforehand but not too hardened so that it will be able to flow and completely immerse as heating. In general, prepregs are fiberglass reinforced and strengthened by an adhesive later similar to the FR4 material that we have reviewed earlier in the article.

Different manufacturers have different requirements when it comes to thickness and specific types of prepreg. Furthermore, there are the versions "SR" Standard Resin, "HR" High Resin, and "MR" Medium Resin that are based on the resin content. The best possible material used depends on the desired final layer of structure, thickness, and impedance.

Copper Foil - Copper foil is an electrolytic cathodic material. It is deposited on a thin and continuous layer of metal foil on the base of a PCB. It is easy to bond to an insulating layer, which will lead to the creation of a printed protective layer to protect the board from corrosion.

PCB material

What makes the Best Copper Clad Laminate?

Size - Since the copper clad laminate is the base material of a PCB, they have to meet some size requirements accurately as per the desired end design. All parameters are taken under careful consideration including width, length, diagonal deviation, and warpage. All these requirements have to be met to be exact in order for a successful application.

Appearance - There is a wide range of possible issues that can occur on the copper foil due to unexpected elements during the manufacturing process. Some of these issues could be scratches, dents, resin points, pinholes, wrinkles, bubbles, and more. If any of these issues occur, this will definitely lead to the poor performance of the copper-clad laminate and it will then reflect on the printed board.

Electric Performance - The electric performance has to be carefully designed as this is one of the essential aspects. Again, here we have some strict requirements including dielectric loss tangent (Df), dielectric constant (Dk), surface resistance, insulation resistance, volume resistance, arc resistance, electric strength, and Comparative Tracking Index (CTI).

Environmental Performance - It has to be ensured that simple requirements such as water absorption and corrosion resistance are met. Otherwise, the production process may encounter serious failures in performance.

Chemical Performance - The chemical performance of copper-clad laminate is extremely important and it has to meet the strict requirements for flammability, Tg, chemical regents resistance, Z-axis coefficient of thermal expansion (Z-CTE), and dimensional stability.

Physical Performance - Requirements related to the physical performance include Peel Strength (PS), dimensional stability, bending strength, heat resistance (with thermal stress, Td, T260, T300, T288), and punching quality.

The Future of Copper Clad Laminate

There are two major potential leeds we have that are directly related to the higher and newer requirements that had been brought concerning reliability and heat resistance.

Halogen-Free Copper Clad Laminate - It refers to copper-clad laminates with a content of bromine (Br) and chlorine (Cl) that is controlled within 900ppm when their overall content is below 1500ppm.

To illustrate it better here is a comparison table of halogen-free copper-clad laminate vs FR-4 CCL.

Item
Halogen-Free CCL
FR-4 CCL
Flammability
V-0
V-0
Peel Strength
Bad
Good
Heat Performance
Good
Bad
Thermal Decomposition
>320°C
320°C
Size Stability
Excellent
Bad
T260
>30min
10min
Bending Strength
Bad
Good

Lead-Free Copper Clad Laminate - The lead-free copper-clad laminate refers to CCLs whose surface mounting is carried out without the application of lead-free solder. According to the regulations of RoHS, six substances such as PBDE and PBB are no longer in use for copper-clad laminate. If we compare it with the DICY curing system (with a curing agent, dicyandiamide) applied in ordinary FR-4 copper-clad laminates, lead-free CCLs take advantage of the PN curing system). To visualize refer to the below table:

Item
DICY
PN
Peel Strength
Good
Bad
Thermal Performance
Bad
Good
CAF Resistance
Bad
Good
Thermal Decomposition Temperature
>320°C
>320°C
T260
10min
>30min
Bending Strength
Good
Bad

Here are also the terms of peel strength on halogen-free copper-clad laminates and lead-free CCLs that have been accepted by the printed circuit board and copper-clad laminate industries.

Specifications
IPC Standard
Attributes
Attributes
Attributes
12μm
/
>5
>0.9

/

12μm
/

>6

>1.05
1.5Kg/cm
12μm
>1.05N/mm
>8
>1.4
1.5Kg/cm
12μm
/
>11
>2.0
/

How Copper Clad Laminates are Classified?

Copper clad laminates are usually classified by a few essential aspects and standards that allow us to sort them into 5 categories:

  • Based on insulation material and structures we have metal-based copper clad laminate, ceramic-base copper-clad laminate, and CCL (FR-4 and CEM-3).
  • Based on thickness we have the standard thickness copper-clad laminate and thin CLL. As we already mentioned each individual assembly end design could require a different thickness, weight and etc. The most common requirement is at least 0.5mm thickness whale the letter can be even thinner than 0.5mm. Note that the copper foil thickness is excluded from the copper-clad laminate thickness.
  • Based on copper-clad laminate mechanical rigidity, we have rigid CCL (FR-4 & CEM-1) and flexible CCL.
  • Based on the reinforcing material types it could be fiber cloth base copper clad laminate (FR-5 and FR-4), compound CCL (CEM-1 and CEM-3), and paper-based copper clad laminate (XPC).
  • Based on the insulation resin applied, we have epoxy resin copper clad laminate (CEM-3, FR-4) and Phenolic CCL (XPC and FR-1).

Learn More about PCB fabrication and CLL

PCBONLINE is a great source to order and customize your own PCB as per your requirements. They use a high-quality management system for every raw material and electronic component. They are using only reliable and proven sources for ensuring the reliability of your terminal products. They always aim to exceed your expectations by taking the advantages one step further in your service.

When working us them you can expect:

  • High-quality flexible PCB raw materials, ensuring the source quality.
  • Cover Film: TaiFlex, APLUS, RCCT

    Material: Dupont, TaiFlex

    PI reinforce: UBE, TaiFlex, SKC

    Electromagnetic membrane: Fang Bang, Toyo, Sankei

  • Professional research and development department, with a production and quality management team with years of experience in flexible circuits fabrication.
  • Wide-range of production types as a PCB supplier: CTP, flexible PCB led strip, Biological recognition, automotive, and more.
  • Best cost solution deliverable from a variety of different design materials and expert evaluation of manufacturability in the end-design product.
  • Team of professionals available at your services 24/7.
  • Strictly following the IPC standards in order to ensure the quality of the shipments.
  • Fast delivery time provides the customers with marketing advantages.

PCBONLINE’s capability:

  • Layer: 1 ~ 42
  • Laminate: normal Tg/high-Tg/lead-free/halogen-free
  • Surface finishing: OSP/HASL/LF HASL/immersion ENIG/immersion tin/immersion silver
  • Board thickness: 0.15 ~ 3.2 mm
  • Max board size: 500 × 580 mm
  • Copper thickness: (inner finish copper) 1-4oz, (outer finish copper) 1-7oz
  • Min. line width/spacing: 0.0635 mm/0.0635 mm
  • Min. CNC drilling size: 0.15 mm
  • Min. laser drilling size: 0.075 mm
  • HDI stack up: 1+N+1, 2+N+2, 3+N+3

They provide real-time feedback with professional opinions, quotes, PCB fabrication, assembly, and components sourcing.

Conclusion

This article gives comprehensive research on copper clad laminate, including its types, how to classify and choose them, and recommends a good PCB manufacturer, PCBONLINE, who can customize boards made of any materials. If you want to learn more about printed circuit boards, do not forget to visit our  BLOG for more interesting content in the PCB industry.