PCB  material is an important part of PCB. It determines the PCB board performance and scope of application. Different products have different requirements on the PCB  material. With the development of electronic technology, PCB  material meet more and more challenges, which also push the development of copper clad laminate(CCL).

What is CCL?

The structure of CCL

Copper Clad Laminates (CCL), also known as cores, are sheets of rigid material made by impregnating glass fiber cloth or other reinforcing materials with resin, covering one or both sides with copper foil and laminating together in a hot press. They form the main structure of rigid printed circuit boards, giving PCBs their thickness and strength.The structure of the copper clad laminate can be divided into three layers:  layer, copper foil, copper clad laminate adhesive:

1.plat

The substrate of the core is composed of polymer synthetic resin and reinforcing material. There are many types of synthetic resins. Commonly used are phenolic resin, epoxy resin, polytetrafluoroethylene and so on. There are generally two types of reinforcement materials: paper and fiberglass cloth.

2.copper foil

Copper foil is an important material for the manufacture of copper clad laminates, which must have high conductivity and good weldability. This helps reduce the impedance of the circuit and facilitate welding of components. It is required that the surface of the copper foil shall not have scratches, blisters and wrinkles, the l purity shall not be less than 99.8%, and the thickness error shall not exceed ±5um.

3.adhesive for the copper clad laminate

The adhesive is the key to whether the copper foil can be firmly covered on the substrate. The peel strength of the copper clad laminate mainly depends on the performance of the adhesive.

The role of CCL

CCL mainly plays the role of interconnection, insulation and support in the PCB, and has a great influence on the transmission speed, energy loss and characteristic impedance of the signal in the circuit. Therefore, CCL largely determines the performance, quality, processability, manufacturing level, manufacturing cost, and long-term reliability and stability of the PCB.

Types of CCL: Rigid CCL and Flexible CCL

Generally speaking, CCL can be divided into two categories: Rigid Copper Clad Laminate and Flexible Copper Clad Laminate.Rigid Copper Clad Laminate can be divided into different types according to different factors such as insulating material, thickness, and reinforcing material. There are also many different types of Flexible Copper Clad Laminate.

Rigid Copper Clad Laminate

Divided by insulating material and its structure

• Organic resin copper clad laminate

• l  (core) copper clad laminate

l-d copper clad laminates are generally composed of three parts: a l substrate, an insulating medium, and a conductive layer (usually copper foil). That is, one or both sides of a l substrate whose surface has been chemically or electrochemically treated are covered with an insulating dielectric layer and copper foil, and then composited by hot pressing.

• Ceramic  copper clad laminate

The ceramic  copper clad laminate is composed of a ceramic substrate, a bonding layer and a conductive layer (copper foil). There are many types of ceramics.

Divided by the thickness of the CCL

• Conventional board

The thickness of the conventional board is not less than 0.8mm.

• Thin board

The thickness of the thin plate is less than 0.8mm. However, the IPC standard defines the thickness of the thin plate to be less than 0.5mm. Epoxy resin glass fiber thin board can be used for punching processing, and glass fiber cloth thin board can be used for inner core board of mult PCB.

Divided by reinforced materials used by CCL

• Electronic glass fiber cloth  copper clad laminate

Electronic grade glass fiber cloth has the characteristics of good electrical insulation, fire retardant, waterproof, aging resistance, weather resistance, high strength and high modulus.

• Paper-d copper clad laminate

The paper-d copper clad laminate is made of impregnated fiber paper as a reinforcing material, impregnated with a resin solution and dried, then covered with glued copper foil, and then formed by high temperature and high pressure lamination. The most common paper-d copper clad laminates are: FR-1, FR-2, FR-3, (flame retardant) and XPC, XXXPC (non-flame retardant).

• Composite  copper clad laminate

Mainly refers to the insulating  material composed of two different reinforcing materials for the surface layer and the core layer. In addition, different copper clad laminates can also be divided according to the insulating resin used in the copper clad laminate or according to the flame retardant grade and other some special properties.

Flexible Copper Clad Laminate

• Polyester film type (flame retardant and non-flame retardant)

• Polyimide film type (flame retardant, non-flame retardant, two-layer method and three-layer method)

• Ultra-thin electronic glass fiber cloth type