Abstract:PCB board is the base material, which is finally composed of copper foil and P sheet (bonding sheet), because these two substances have many classifications due to different applications. The following are some basic classifications of pcb boards.
Table of content
1.The resin adhesive used in the board is different
2.According to the flame retardant performance of CCL classification
3.According to the performance classification of CCL
1.The resin adhesive used in the board is different
Common paper-based CCIs are: phenolic resin (XPc, XxxPC, FR-1, FR-2, etc.), epoxy resin (FE-3), polyester resin and other types.
Common glass fiber cloth base CCL has epoxy resin (FR-4, FR-5), which is currently the most widely used type of glass fiber cloth base.
In addition, there are other special resins (with glass fiber cloth, polyamide fiber, non-woven fabric, etc. as additional materials): bismaleimide modified triazine resin (BT), polyimide resin (PI) , Diphenylene ether resin (PPO), maleic anhydride imine-styrene resin (MS), polycyanate resin, polyolefin resin, etc.
2. According to the flame retardant performance of CCL classification
It can be divided into flame-retardant type (UL94-VO, UL94-V1 grade) and non-flame-retardant type (UL94-HB grade). In the past year or two, with more attention to environmental issues, a new type of CCL that does not contain bromine has been classified in flame-retardant CCL, which can be called “green flame-retardant C CL”.
3. According to the performance classification of CCL
With the rapid development of electronic product technology, there are higher performance requirements for cCL. Therefore, from the performance classification of CCL, it is divided into general performance CCL, low dielectric constant CCL, high heat resistance CCL (normal board L is above 150 ℃), low thermal expansion coefficient CCL (usually used on package substrates) ) And other types.
With the development and continuous progress of electronic technology, new requirements are constantly being put forward for printed circuit board substrate materials, thereby promoting the continuous development of copper clad laminate standards. At present, the main standards of substrate materials are as follows :
PCB circuit board material introduction: According to the brand quality level from bottom to high, it is divided as follows: 94HB-94VO-CEM-1-CEM-3-FR-4
The classifications of PCB boards detailed parameters and uses are as follows:
94HB: ordinary cardboard, not fireproof (the lowest grade material, die punching, can not be used as a 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 four types: 94VO-V-1 -V-2 -94HB
2 > . Prepreg: 1080=0.0712mm, 2116=0.1143mm, 7628=0.1778mm
3 > . FR4 CEM-3 is for sheet material, fr4 is fiberglass 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, that is, the melting point.
6 > . The circuit board must be flame-resistant, cannot burn at a certain temperature, but 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 circuit board.
What is high Tg? Circuit board and the advantages of using high Tg circuit board:
When the temperature of the high Tg printed circuit board rises to a certain threshold, the substrate will change from the “glass state” to the “rubber state”. The temperature at this time is called the glass transition temperature (Tg) of the board. That is, Tg is the highest temperature (°C) at which the base PCB circuit board material maintains rigidity.
That is to say, ordinary circuit board 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 characteristics. This will affect the service life of the product. Generally, Tg plates are Above 130°C, high Tg is generally greater than 170°C, and medium Tg is approximately greater than 150°C; usually circuit board printed boards with Tg≥170°C are called high Tg printed boards;
As the Tg of the substrate increases, the heat resistance, moisture resistance, chemical resistance, stability and other characteristics of the printed board 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 circuit board substrate materials as a prerequisite.
The emergence and development of high-density mounting technologies represented by SMT and CMT have made circuit boards more and more inseparable from the support of high heat resistance of substrates in terms of small aperture, fine circuit and thinner.
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 circuit board material.