PCB board classification and parameter explanation

PCB board classification and parameter explanation

PCB circuit board sheet introduction: according to the brand quality level from the bottom to the high is divided 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, cannot be a power board)

94V0: Flame retardant cardboard (die punching)

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

CEM-1: Single-sided glass fiber board (must be drilled by computer, not punched)

CEM-3: Double-sided semi-glass fiber board (except for double-sided cardboard, which belongs to the lowest end of the 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 glass fiber board

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

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

3. FR4 CEM-3 means sheet, fr4 is glass fiber board, cem3 is composite substrate

4. Halogen-free refers to substrates that do not contain halogen (e.g., fluorine, bromine, iodine, etc.), because bromine generates toxic gases when burned, which requires environmental protection.

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

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

What is high Tg? PCB circuit board and the advantages of 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 maximum temperature (°C) at which the substrate remains rigid. In other words, ordinary PCB substrate materials continue to soften, deform, melt and other phenomena at high temperatures, but also show a sharp decline in mechanical and electrical characteristics, which affects the service life of the product. The general Tg sheet is 130 Above ℃, high Tg is generally greater than 170 ℃, medium Tg is approximately greater than 150 ℃; usually PCB printed board with Tg ≥ 170 ℃ is called high Tg printed board; the Tg of the substrate is improved, the heat resistance of the printed board, Moisture resistance, chemical resistance, stability and other characteristics will be improved and improved. The higher the TG value, the better the temperature resistance of the sheet. Especially in the lead-free process, high Tg is more used; 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 multilayer requires the higher heat resistance of PCB substrate materials as a premise. 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 apertures, fine wiring and thinning.

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