The circuit board must be flame-resistant, it cannot burn at a certain temperature, it can 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 board.
What is a high TgPCB circuit board and the advantages of using a high TgPCB?
When the temperature of high Tg printed boards rises to a certain area, the substrate will change from "glass state" to "rubber state", and the temperature at this time is called the glass transition temperature (Tg) of the board. That is, T is the highest temperature at which the substrate remains rigid.
What types of PCB board materials are there? According to the grade level from bottom to high, it is divided as follows:
94HB - 94vo - 22F -CEM-1 - CEM-3 - FR-4 are introduced in detail as follows:
94HB: Ordinary cardboard, not fireproof (the lowest grade material. Die punching. Can not be used as a power 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 required, not punching)
CEM-3: Double-sided semi-fiberglass board (except for double-sided cardboard, it is the lowest-end material for double-sided panels. Simple double-sided panels can use this material, which is 5~10 yuan/square meter cheaper than FR-4)
FR-4: double-sided glass fiber board
The circuit board must be flame-resistant, it cannot burn at a certain temperature, it can 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 board.
What is a high Tg PCB circuit board and the advantages of using a high Tg PCB High Tg printed board When the temperature rises to a certain area, the substrate will change from "glass state" to "rubber state", and the temperature at this time is called the temperature of the board Glass transition temperature (Tg). That is, Tg is the highest temperature (° C.) at which the substrate remains rigid. That is to say, ordinary PCB substrate materials not only soften, deform, melt, etc. at high temperatures, but also show a sharp decline in mechanical and electrical properties (I think you don’t want to see this situation in your own products by looking at the classification of PCB boards. ).
The general Tg of the plate is above 130 degrees, the high Tg is generally greater than 170 degrees, and the medium Tg is greater than 150. Generally, PCB printed boards with Tg2170°C are called high Tg printed boards. The Tg of the substrate is increased, and the heat resistance, moisture resistance, chemical resistance, and stability 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, there are more high Tg applications.
High Tg means high heat resistance. With the rapid development of the electronics industry, especially electronic products represented by computers, are developing towards high functionality and high multi-layers, which requires higher heat resistance of PCB substrate materials as an important guarantee. The emergence and development of high-density mounting technologies represented by SMT and CMT have made PCBs smaller in aperture, finer lines, and thinner. It is increasingly inseparable from the support of high heat resistance of the substrate.
Therefore, the difference between general FR-4 and high Tg FR-4 is that the mechanical strength, dimensional stability, adhesion, water absorption, and thermal decomposition of the material are in the hot state, especially when heated after moisture absorption. There are differences in various conditions such as thermal expansion, and high T products are obviously better than ordinary PCB substrate materials. In recent years, the number of customers who require high Tg printed boards has increased year by year.
With the development and continuous progress of electronic technology, new requirements are constantly put forward for printed board substrate materials, thereby promoting the continuous development of copper clad laminate standards. Currently, the main standards for substrate materials are as follows.
①National standards At present, my country's national standards for the classification of substrate materials pcb boards include GB/T4721-47221992 and G84723-4725-1992. The standard for copper foil boards in Taiwan, China is the CNS standard, which is based on Japanese standards. . Released in 1983.
②The main standards of other national standards are: Japanese JS standard, American ASTM, NEMA, MIL, IPc, ANSI, UL standard, British Bs standard, German DIN.VDE standard, French NFC, UTE standard, Canadian CSA Standards, Australia's AS standard, the former Soviet Union's FOCT standard, the international IEC standard, etc.
Accepted files: protel autocad powerpcb orcad gerber or solid copy board, etc.
●Board type: CEM-1, CEM-3 FR4, high TG material;
●Maximum board size: 600mm*700mm (24000mil*27500mil) Processing board thickness: 0.4mm-4.0mm(15.75mil-157.5mil) Maximum processing layers: 16Layers
●Thickness of copper foil layer: 0.5-4.0(oz)
●Or product thickness tolerance: +/-0.1mm (4mil)
Molding size tolerance: computer milling: 0.15mm (6mil) mold stamping: 0.10mm (4mil) minimu line width/spacing: 0.1mm (4mil) line width control ability: <+-20%
The minimu drilling diameter of the finished product: 0.25mm (10mil)
Finished minimu punching hole diameter: 0.9mm (35mil)
Finished hole tolerance: PTH: +-0.075mm (3mil) NPTH: +-0.05mm (2mil)
Copper thickness of finished hole wall: 18-25um (0.71-0.99mil)
·minimu SMT patch pitch: 0.15mm (6mil)
Surface coating requirements: chemical immersion gold, spray ring, whole board nickel-plated gold (water/soft gold), silk screen blue glue, etc.
●Solder mask thickness on the board: 10-30um (0.4-1.2mil)
●Peel strength: 1.5N/mm (5sN/mil)
●Solder mask hardness:>5H
●Solder resistance plugging capacity: 0.3-0.8mm (12mil-30mil) ●Dielectric constant: E= 2.1-10.0
●Insulation resistance: 10KQ-20MQ characteristic impedance: 60 ohm±109% ●Thermal shock: 288℃, 10 sec ●Warpage of finished board: <0.7%
Product application: communication equipment, automotive electronics, instrumentation, global positioning system, computer, MP4, power supply, home appliances, etc.
According to the PCB board reinforcement materials, it is generally divided into the following types: 1. Phenolic PCB paper substrate
Because this kind of PCB board is composed of pulp and wood pulp, it sometimes becomes cardboard, VO board, flame retardant board and 94HB, etc. Its main material is wood pulp fiber paper, which is pressurized and synthesized by phenolic resin. plate.
The characteristics of this kind of paper substrate are that it is not fireproof, can be punched, has low cost, low price, and low relative density. The phenolic paper substrates we often see are XPC, FR-1, FR-2.FE-3, etc. And 94v0 belongs to flame retardant cardboard. It is fireproof.
2. Composite PCB substrate
This kind is also called powder board, with wood pulp fiber paper or cotton pulp fiber paper as reinforcement material. At the same time, it is supplemented by glass fiber cloth as the surface reinforcement material, and the two materials are made of flame-retardant epoxy resin. There are single-sided half-glass fiber 22F, CEM-1, and double-sided half-glass fiber board CEM-3, among which CEM-1 and CEM-3 are currently the most common composite-based copper clad laminates.
3. Glass fiber PCB substrate
Sometimes it is also called epoxy board, glass fiber board, FR4, fiber board, etc. It uses epoxy resin as adhesive and glass fiber cloth as reinforcing material. This kind of circuit board has a higher working temperature and is less affected by the environment. This kind of board is often used in double-sided PCBs, but the price is more expensive than composite PCB substrates, and the common thickness is 1.6MM. This substrate is suitable for various power supply boards and high-level circuit boards, and is widely used in computers, peripheral equipment, and communication equipment.
4. Other substrates
In addition to the three commonly seen above, there are also metal substrates and build-up multilayer boards (BUM).
