Oct. 31, 2019
According to PCB board reinforcement materials are generally divided into the following categories:
1, Phenolic PCB paper substrate
Because this kind of PCB board is composed of pulp wood pulp, etc., it is sometimes used as cardboard, V0 board, fire-retardant board and 94HB, etc. Its main material is wood pulp fiber paper, which is pressed and synthesized by phenolic resin. board. The paper substrate is characterized in that it is not fireproof, can be punched, has low cost, is inexpensive, and has a relatively low density. Phenolic paper substrates We often see XPC, FR-1, FR-2, FE-3 and the like. And 94V0 is a flame retardant cardboard, it is fireproof.
2, composite PCB substrate
This also becomes a powder board, which is made of wood pulp fiber paper or cotton pulp fiber paper, and is supplemented with glass fiber cloth as a surface reinforcing material. The two materials are made of flame retardant epoxy resin. There are single-sided semi-glass 22F, CEM-1 and double-sided semi-glass fiberboard CEM-3, among which CEM-1 and CEM-3 are the most common composite copper-clad laminates.
3, glass fiber PCB substrate
Sometimes it also becomes epoxy board, fiberglass board, FR4, fiberboard, etc. It uses epoxy resin as a binder and glass fiber cloth as a reinforcing material. This kind of circuit board has a higher operating temperature and is less affected by the environment. This type of board is often used in double-sided PCBs, but the price is relatively high compared to the composite PCB substrate, and the thickness is usually 1.6MM. The substrate is suitable for various power boards and high-level circuit boards, and is widely used in computers, peripheral devices, and communication equipment.
4, other substrates
In addition to the three types often seen above, there are also metal substrates and laminated multi-layer boards (BUM).
The electric circuit board must be flame resistant, not combustible at a certain temperature, and only soften. The temperature point at this time is called the glass transition temperature (Tg point), and this value is related to the dimensional stability of the PCB.
What are the advantages of high Tg PCB boards and the use of high Tg PCBs:
When the temperature rises to a certain area, the substrate will change from "glassy state" to "rubbery state", and the temperature at this time is called the glass transition temperature (Tg) of the plate. That is, Tg is the highest temperature (°C) at which the substrate remains rigid. That is to say, the ordinary PCB substrate material not only softens, deforms, melts, etc. at high temperatures, but also exhibits a sharp drop in mechanical and electrical properties.
Generally, the Tg plate is 130 degrees or more, the high Tg is generally greater than 170 degrees, and the medium Tg is greater than about 150 degrees. A PCB printed board with a typical Tg ≥ 170℃ is called a high Tg printed board. The Tg of the substrate is improved, and the characteristics such as heat resistance, moisture resistance, chemical resistance, and stability of the printed board are improved and improved. The higher the TG value, the better the temperature resistance of the sheet, especially in the lead-free process, the high Tg application is 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 multi-layer requires the higher heat resistance of PCB substrate materials as an important guarantee. The emergence and development of high-density mounting technology represented by SMT PCBA processing and CMT makes PCBs more and more inseparable from the high heat resistance of substrates in terms of small aperture, fine wiring and thinning.