How Are PCB Boards Classified

PCB board knowledge and standards

At present, there are several types of copper clad plates widely used in China, and their characteristics are as follows: there are many kinds of copper clad plates, knowledge of copper clad plates, and classification methods of copper clad foil plates. Generally, according to the different reinforcement 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 different resin adhesives, the common paper-based CCI. There are: phenolic resin (XPC, xxpc, FR-1, FR-2, etc.), epoxy resin (Fe-3), polyester resin and other types. Common glass fiber cloth CCL has epoxy resin (FR-4, FR-5), which is the most widely used type of glass fiber cloth at present. In addition, there are other special resins (glass fiber cloth, polyimide fiber, non-woven fabric, etc.) such as bismaleimide modified triazine resin (BT), polyimide resin (PI), diphenylene ether resin (PPO), maleimide styrene resin (MS), polycyanate resin, polyolefin resin, etc.

According to the classification of CCL's flame retardant performance, it can be divided into 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 has been separated from the flame retardant CCL, which can be called "green flame retardant CCL". With the rapid development of electronic product technology, there are higher performance requirements for CCL. Therefore, according to the performance classification of CCL, it can be divided into general performance CCL, low dielectric constant CCL, high heat resistance CCl (the L of general plate is above 150 ℃), low thermal expansion coefficient CCl (generally used on packaging substrate), etc. With the development and progress of electronic technology, new requirements are put forward for printed board substrate materials, so as to promote the continuous development of copper clad laminate standard. At present, the main standards of substrate materials are as follows

â‘  National standards: China's national standards for substrate materials include GB / t4721-47221992 and gb4723-4725-1992. The copper clad laminate standard in Taiwan is CNS standard, which is based on Japanese JIS standard and issued in 1983.

â‘¡ International standards: Japanese JIS standards, American ASTM, NEMA, mil, IPC, ANSI and UL standards, British BS standards, German DIN and VDE standards, French NFC and ute standards, Canadian CSA standards, Australian as standards, former Soviet FOCT standards, international IEC standards, etc; Suppliers of PCB design materials are common and commonly used: Shengyi, Jiantao, international, etc.

Introduction to PCB board: according to the brand quality level from bottom to top, it is divided as follows: 94hb-94vo-cem-1-cem-3-fr-4

Detailed parameters and uses are as follows:

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

94v0: flame retardant paperboard (die punching)

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

CEM-1: single side fiberglass board (computer drilling is required, die punching is not allowed)

CEM-3: double sided semi fiberglass board (except for double-sided paperboard, it is the lowest end material of double-sided board. This material can be used for simple double-sided board, which is 5 10 yuan / m2 cheaper than FR-4)

FR-4: double sided fiberglass board

1. The classification of flame retardant characteristics can be divided into 94vo-v-1-v-2-94hb

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

3. FR4 and CEM-3 are plates, FR4 is fiberglass board and 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 during combustion, which is required by environmental protection.

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

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

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

When the temperature of high Tg printed circuit board 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. That is, TG is the maximum temperature (℃) at which the substrate remains rigid. In other words, ordinary PCB substrate materials constantly produce softening, deformation, melting and other phenomena at high temperature. At the same time, they also show a sharp decline in mechanical and electrical characteristics, which will affect the service life of the product. Generally, the TG plate is more than 130 ℃, the high Tg is generally more than 170 ℃, and the medium TG is about more than 150 ℃; Generally, PCB printed boards with TG ≥ 170 ℃ are called high Tg printed boards; The Tg of the substrate is improved, and the heat resistance, moisture resistance, chemical resistance, stability and other characteristics of the printed board will be improved. The higher the TG value, the better the temperature resistance of the plate, especially in the lead-free process, the application of high Tg is more; High Tg refers to high heat resistance. With the rapid development of electronic industry, especially the electronic products represented by computers are developing towards high functionality and high multilayer, which requires the higher heat resistance of PCB substrate materials as the premise. The emergence and development of high-density installation technology represented by SMT and CMT make PCB more and more inseparable from the support of high heat resistance of substrate in terms of small aperture, fine wiring and thin.

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

How Are PCB Boards Classified 1

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