At present, China's production of PCB circuit board in the heavy use of copper clad plate; Generally, according to the different reinforcing materials of the board, it can be divided into five categories: paper base, glass fiber cloth base, composite base (CEM Series), laminated multilayer board base and special material base (ceramic, metal core base, etc.).

If the board is classified according to the resin adhesive used, the common paper-based CCI. There are: phenolic resin (XPC, xxpc, FR-1, FR 12, etc.), epoxy resin (Fe-3), polyester resin and other types.

Common glass fiber based CCL has epoxy resin (FR-4, FR-5), which is the most widely used type of glass fiber cloth. In addition, there are other special resins (glass fiber cloth, poly (amide fiber), non-woven fabric and other materials: bismaleimide modified triazine resin (BT), polyimide resin (PI), diphenyl ether resin (PPO), maleimide styrene resin (MS), polycyanate resin, polyolefin resin, etc.

According to the classification of CCL, it can be divided into two types of boards: flame retardant (UL94 VO, ul94-v1) and non flame retardant (ul94-hb).

In recent years, with more attention to environmental protection, a new type of CCL without bromine is divided into flame retardant CCL, which can be called "green flame retardant CaCl".

With the rapid development of electronic products technology, there is higher performance requirements for the CaCl.

Therefore, according to the performance classification of CCL, it can be divided into general performance CCL, low dielectric constant CCL, CCL with high heat resistance (L of general board is more than 150), CCL with low thermal expansion coefficient (generally used on the packaging substrate) and other types.

With the development and progress of electronic technology, new requirements are put forward for the printed board substrate materials, thus promoting the continuous development of copper clad foil standards. At present, the main standards of substrate materials are as follows

National standard: the national standards for substrate materials in China include GB / t4721-47221992 and gb4723-4725-1992. The copper clad foil standard in Taiwan is CNS standard, which is formulated based on JIS standard in Japan and issued in 1983.

International standards: JIS standards in Japan, ASTM, NEMA, mil, IPC, ANSI and UL standards in the United States, BS standards in the UK, DIN and VDE standards in Germany, NFC and ute standards in France, CSA standards in Canada, as standards in Australia, FOCT standards of the former Soviet Union, international IEC standards, etc; PCB design materials suppliers, common and commonly used: Shengyi Jiantao international, etc.

PCB board introduction:

The classification from bottom to high by brand quality level is as follows: 94hb-94vo-cem-1-cem-3-fr-4

Detailed parameters and uses are as follows:

94hb: ordinary board, non fire resistant (lowest grade material, die punching, power board not allowed)

94v0: flame retardant board (die punch)

22F: single side half glass fiber board (die punch)

CEM-1: single side fiberglass plate

CEM-3: double sided semi glass fiber board (except double-sided board, it belongs to the lowest end material of double-sided board, and simple double-sided board can use this material, which will be 5-10 yuan / m2 cheaper than FR-4)

Fr-4: double sided fiberglass board

1. the classification of flame retardant properties can be divided into four types: 94vo-v-1-v-2-94hb

2. semi curing piece: 1080=0.0712mm, 2116=0.1143mm, 7628=0.1778mm

3. FR4 CEM-3 is used to represent the plate, FR4 is fiberglass board, and cem3 is composite substrate

4. halogen free refers to the base material without halogen (such as fluorine bromine iodine) because bromine will produce toxic gas during combustion, which requires environmental protection.

5. TG is the glass conversion temperature, i.e. melting point.

6. the circuit board must be flame resistant, and it cannot be burned at a certain temperature and can only be softened. The temperature point is called glass transition temperature (TG point), which is related to the dimension durability of PCB.

What is high Tg?

Advantages of PCB PCB and high Tg PCB: when the temperature of high Tg PCB rises to a certain threshold, the substrate will change from "glass state" to "rubber state", and the temperature is called glass temperature (TG) of the board. That is, TG is the highest temperature at which the substrate remains rigid. That is to say, the common PCB substrate materials under high temperature, constantly produce softening, deformation, melting and other phenomena, and also show a sharp decline in mechanical and electrical characteristics, which affects the service life of the product. Generally, TG plate is over 130, high Tg is generally greater than 170, and medium TG is about 150; Generally, PCB printed boards with TG ≥ 170 are called high Tg printed boards; Tg of the substrate is improved, and the heat resistance, humidity resistance, chemical resistance and stability of printed board will be improved.

The higher Tg value, the better the temperature resistance of the plate, especially in lead-free process, high Tg is used more; High Tg refers to high heat resistance. With the rapid development of electronic industry, especially the electronic products represented by computer, it is necessary to have higher heat resistance of PCB substrate materials.

The emergence and development of high density installation technology represented by SMT and CMT make PCB more and more independent of the support of high heat resistance of PCB in small aperture, fine circuit and thin profile. So the difference between general FR-4 and high Tg is that the mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition and thermal expansion of the materials are different at the same temperature, especially after moisture absorption. The high Tg products are obviously better than the ordinary base plate materials.