Detailed explanation of PCB board classification and parameters

Detailed explanation of PCB board classification and parameters

PCB circuit board board introduction: according to the brand quality level from bottom to high as follows: 94HB-94VO-CEM-1-CEM-3-FR-4

The detailed parameters and uses are as follows:

94HB: ordinary cardboard, not fireproof (the lowest grade material, die punching, can not be used as power supply board)

94V0: Flame Retardant Cardboard (Die Punching)

22F: Single-sided half glass fiber board (die punching)

CEM-1: Single-sided fiberglass board (computer drilling is necessary, not die punching)

CEM-3: Double-sided semi-glass fiber board (except for double-sided cardboard, it is the lowest-end material of double-sided board. Simple double-sided board can use this material, which is 5~10 yuan/square meter cheaper than FR-4)

FR-4: Double-sided fiberglass board

1. The grades of flame retardant properties can be divided into 94VO-V-1 -V-2 -94HB

2. Semi-cured film: 1080=0.0712mm, 2116=0.1143mm, 7628=0.1778mm

3. FR4 and CEM-3 are all plates, fr4 is glass fiber board, cem3 is composite substrate

4. Halogen-free refers to the base material that does not contain halogen (fluorine, bromine, iodine and other elements), because bromine will produce toxic gas when burned, environmental protection requirements.

5. Tg is the glass transition temperature, or melting point.

6. The circuit board must be flame-resistant. It cannot burn at a certain temperature and can only be softened. The temperature at this time is called the glass transition temperature (Tg point), and this value is related to the dimensional durability of the PCB.

What is high Tg? Advantages of PCB circuit board and using high Tg PCB:

high Tg printed circuit board when the temperature rises to a certain threshold, the substrate will change from "glass state" to "rubber state". The temperature at this time is called the glass transition temperature (Tg) of the board. In other words, Tg is the highest temperature (°C) at which the substrate maintains rigidity. That is to say, ordinary PCB substrate materials will continue to soften, deform, and melt at high temperatures. At the same time, they will also show a sharp decline in mechanical and electrical properties. This will affect the service life of the product. Generally, the Tg plate is 130 ℃ above, high Tg is generally greater than 170 ℃, medium Tg is greater than 150 ℃; usually Tg ≥ 170 ℃ PCB printed boards are called high Tg printed boards; the Tg of the substrate increases, the heat resistance of the printed board, Features such as moisture resistance, chemical resistance, and stability will be improved and improved. The higher the TG value, the better the temperature resistance of the board, especially in the lead-free process, high Tg applications are more; high Tg refers to high heat resistance.

With the rapid development of the electronics industry, especially the electronic products represented by computers, the development of high functionality and high multilayers requires higher heat resistance of PCB substrate materials as a prerequisite. The emergence and development of high-density mounting technologies represented by SMT and CMT have made PCBs more and more inseparable from the support of high heat resistance of substrates in terms of small aperture, fine wiring, and thinning.

Therefore, the difference between general FR-4 and high Tg: at the same high temperature, especially when heated after moisture absorption, the material's mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, thermal expansion, etc. There are differences in this situation. High Tg products are obviously better than ordinary PCB substrate materials.