**What is Copper Clad Laminate?**
The primary material of a printed circuit board (PCB) is copper clad laminate. Copper clad laminate consists of a substrate, copper foil, and adhesive. The substrate is an insulating layer made from polymer synthetic resin and reinforcing materials. The surface of the substrate is covered with a layer of high-conductivity, high-solderability pure copper foil, typically with a thickness of 35-50 µm. Copper clad laminate with copper foil on only one side of the substrate is called single-sided copper clad laminate, while laminate with copper foil on both sides is referred to as double-sided copper clad laminate. The adhesive ensures that the copper foil adheres firmly to the substrate. Common thicknesses for copper clad laminates are 1.0 mm, 1.5 mm, and 2.0 mm.
**What are the Commonly Used Copper Clad Laminates?**
The following types of copper clad laminates are commonly used:
– **FR-1:** Phenolic cotton paper, commonly known as bakelite, is more economical than FR-2.
– **FR-2:** Phenolic cotton paper.
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FR-3 ── Cotton paper, epoxy resin.
FR-4 ── Woven glass, epoxy resin.
FR-5 ── Glass cloth, epoxy resin.
FR-6 ── Masked glass, polyester.
G-10 ── Glass cloth, epoxy resin.
CEM-1 ── Cotton paper, epoxy resin (flame retardant).
CEM-2 ── Cotton paper, epoxy resin (non-flame retardant).
CEM-3 ── Glass cloth, epoxy resin.
CEM-4 ── Glass cloth, epoxy resin.
CEM-5 ── Glass cloth, polyester.
AIN ── Aluminum Nitride.
SIC ── Silicon Carbide.
There are also many types of copper-clad laminates. Based on different insulating materials, they can be categorized into paper substrates, glass cloth substrates, and synthetic fiberboards. According to different binder resins, they can be classified into phenolic, epoxy, polyester, and polytetrafluoroethylene types. Additionally, laminates can be divided into general-purpose and special types based on their intended use.
The structure and characteristics of commonly used PCB copper-clad laminates in China are as follows:
1) **Copper-Clad Phenolic Paper Laminate**: This laminate is made from insulating paper impregnated with phenolic resin and hot-pressed. It may include a single layer of alkali-free glass cloth on both surfaces, with copper foil covering one side. It is primarily used as a printed circuit board in radio equipment.
2) **Copper-Clad Phenolic Glass Cloth Laminate**: This laminate consists of alkali-free glass cloth impregnated with epoxy phenolic resin and hot-pressed. Copper foil may be applied to one or both sides. It features light weight, good electrical and mechanical properties, and ease of processing. The board surface is typically light yellow; if melamine is used as the curing agent, the surface is light green with good transparency. It is mainly used for printed circuit boards in radio equipment that operate at higher temperatures and frequencies.
3) **Copper-Clad PTFE Laminate**: Made from PTFE board as the base material, this laminate is coated with copper foil and hot-pressed. It is predominantly used for printed boards in high-frequency and ultra-high-frequency circuits.
4) **Copper-Clad Epoxy Glass Cloth Laminate**: This is a commonly used material for hole-metallized printed circuit boards.
5) **Soft Polyester Copper-Clad Film**: This material is a ribbon-shaped composite of polyester film and copper, created through hot pressing. In application, it is often rolled into a spiral and placed inside equipment. To reinforce or prevent moisture ingress, it is commonly encased in epoxy resin. It is mainly used as flexible printed circuits and printed cables, and can also serve as a transition line for connectors.
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