Here are some detailed introductions:
94HB: Ordinary cardboard, not fireproof (the lowest grade material, die punching, can not be used as a power board);
94V0: fireproof cardboard (die punching)
22F：Single-sided semi-fiberglass board (die punching)
CEM-1: Single-sided fiberglass board (Computer drilling is required, no die punching)
CEM-3: Double-sided semi fiberglass board (double sided cardboard is the lowest grade double sided board, CEM-3 can be used for simple double sided board, and CEM-3 is 5~10 yuan/square meter cheaper than FR-4);
FR-4: Double-sided fiberglass board
The classification of flame retardant characteristics can be divided into four types: 94V-0 , V-1, V-2 and 94-HB;
Tg is the glass transition temperature, and that is the melting point.
The circuit board must be flame resistant, and cannot burn at a certain temperature, but only soften. At this time, the temperature point is called the glass transition temperature (Tg point), and this value is related to the dimensional stability of the PCB.
High Tg PCB and the merits of high Tg PCB
When the temperature of a high Tg printed board rises to a certain area, the substrate will change from "glassy" to "rubbery", and the temperature at this time is called the glass transition temperature (Tg) of the board. That is, Tg is the maximum temperature (°C) at which the substrate remains rigid. In other words, ordinary PCB substrate materials not only produce softening, deformation, melting and other phenomena, but also manifest a sharp decline in mechanical and electrical properties at high temperatures.
Ordinary Tg PCB can bear 130°C, and high Tg PCB can bear 170 °C.
For PCB with Tg≥170℃, it can be called as high Tg PCB.
As the Tg of the substrate increases, the characteristics of the printed board, such as heat resistance, moisture resistance, chemical resistance, and stability, will be improved. The higher the Tg value, the better the temperature resistance of the board, especially in the lead-free process. There are more applications for high Tg.
High Tg refers to strong heat resistance. With rapid development of electronics industry, particularly electronic products represented by computers are developing towards high functionality and high multi-layering, so the PCB with stronger heat resistance is required. With the emergence and development of high-density mounting technologies represented by SMT and CMT, PCB is increasingly inseparable from the support of high heat resistance of substrates in terms of small aperture, fine wiring, and thinness.
Therefore, the difference between ordinary FR-4 and high Tg FR-4 is that under hot condition, especially when PCB is heated after it absorbs moisture, there are differences in the mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, thermal expansion and other conditions of the material, and the high Tg product is obviously better than ordinary PCB substrate material.
Recently, more and more customers demand to produce high Tg PCB.
PCB and its standards
There are many ways to classify copper clad laminate. Generally, according to the different reinforcing materials of the board, it can be divided into: paper-based, glass-fiber PCB board classification cloth base, composite base (CEM series), multi-layer board base and special material base (ceramic, metal core base, etc.).
Common fiberglass cloth CCL is epoxy resin (FR-4, FR-5), which is the most widely used type of fiberglass cloth at present. In addition, there are other special resins (glass fiber cloth, polyamide fiber, non-woven fabrics, etc.): bismaleimide modified triazine resin (BT), polyimide resin (PI), diphenyl ether resin (PPO), maleic anhydride imine-styrene resin (MS), polycyanate resin, polyolefin resin, etc. According to the classification of flame retardant performance of CCL, there are two types: flame retardant type (UL94-VO, UL94-V1 grade) and non-flame retardant type (UL94-HB grade). In the past one or two years, with more attention to environmental protection, a new bromine-free CCL variety 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, CCLs are classified into general performance CCLs, low dielectric constant CCLs, high heat resistance CCLs (L of general boards is 150℃or more), and low thermal expansion coefficient CCL (generally used on package substrates). With the development and continuous progress of electronic technology, new requirements are constantly put forward for printed board substrate materials, so as to promote the continuous development of copper clad laminate standards. Currently, the main standards for substrate materials are as follows:
National standard about PCB substrate materials is GB／T4721—47221992 and GB4723—4725—1992 in China.
The standard for copper clad laminate is CNS in Taiwan, China.
The main standards of other national standards are: JIS standard in Japan, ASTM, NEMA, MIL, IPc, ANSI, UL standard in United States, Bs standard in United Kingdom, DIN and VDE standard in Germany, NFC and UTE standard in France, CSA standard in Canada, AS standard in Australia, FOCT standard in the former Soviet Union, IEC standard in international standards, etc.
PCB material types: CEM-1, CEM-3, FR4, high Tg;
Maximum size of the board: 600mm*700mm(24000mil*27500mil);
Board thickness: 0.4mm-4.0mm(15.75mil-157.5mil);
Maximum layers: 16 layers;
Copper foil layer thickness: 0.5-4.0(oz);
Finished board thickness tolerance: +/-0.1mm(4mil)
Dimensional tolerance: computer Milling: 0.15mm(6mil) Mold Punching 0.10mm(4mil)
Minimum wire width or spacing: 0.1mm(4mil) control ability＜+-20％
The minimum bore diameter of the finished product: 0.25mm(10mil)
The minimum punching hole diameter of the finished product: 0.9mm(35mil)
Finished hole diameter tolerance: +/-0.075mm(3mil)
NPTH: +/-0.05mm(2mil)
The finished hole wall copper thickness: 18-25um（0.71-0.99mil）
Minimum SMT spacing: 0.15mm(6mil)
Surface coating: chemical immersion gold, tin soldering, nickel gold plating (water/soft gold), silk screen glue, etc Solder mask thickness on board: 10-30μm (0.4-1.2mil)
Peel strength: 1.5N/mm（59N/mil）
Solder mask hardness: ＞5H
Solder mask plug capability: 0.3-0.8mm(12mil-30mil)
Permittivity:ε= 2.1-10.0
Insulation resistance: 10KΩ-20MΩ
Characteristic impedance: 60 ohm±10％
Thermal shock: 288℃, 10 sec
The warpage of the finished PCB: < 0.7％
Product application: communication equipment, automotive electronics, instrumentation, GPS, computer, MP4, power supply, home appliances, etc
