–From pcb world,

The combustibility of materials, also known as flame retardancy, self-extinguishing, flame resistance, flame resistance, fire resistance, flammability and other combustibility, is to evaluate the ability of the material to resist combustion.

The flammable material sample is ignited with a flame that meets the requirements, and the flame is removed after the specified time. The flammability level is evaluated according to the degree of combustion of the sample. There are three levels. The horizontal test method of the sample is divided into FH1, FH2 , FH3 level three, the vertical test method is divided into FV0, FV1, VF2.

The solid PCB board is divided into HB board and V0 board.

HB sheet has low flame retardancy and is mostly used for single-sided boards.

VO board has high flame retardancy and is mostly used in double-sided and multi-layer boards

This type of PCB board that meets the V-1 fire rating requirements becomes FR-4 board.

V-0, V-1, and V-2 are fireproof grades.

The circuit board must be flame-resistant, cannot burn at a certain temperature, but can only be softened. 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?

When the temperature of a high Tg printed board rises to a certain area, 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. In other words, Tg is the highest temperature at which the substrate maintains rigidity.

What are the specific types of PCB boards?

Divided by grade level from bottom to high as follows:

94HB － 94VO － 22F － CEM-1 － CEM-3 － FR-4

The details 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 half glass fiber board (except for double-sided cardboard, it is the lowest end material of double-sided board, simple

This material can be used for double panels, which is 5~10 yuan/square meter cheaper than FR-4)

FR-4: Double-sided fiberglass board

The circuit board must be flame-resistant, cannot burn at a certain temperature, but can only be softened. 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. When the temperature rises to a certain area, the substrate will change from the “glass state” to the “rubber state”.

The temperature at that time is called the glass transition temperature (Tg) of the plate. In other words, Tg is the highest temperature (°C) at which the substrate maintains rigidity. That is to say, ordinary PCB substrate materials not only produce softening, deformation, melting and other phenomena at high temperatures, but also show a sharp decline in mechanical and electrical characteristics (I think you don’t want to see the classification of PCB boards and see this situation in your own products. ).

The general Tg plate is more than 130 degrees, the high Tg is generally more than 170 degrees, and the medium Tg is about more than 150 degrees.

Usually PCB 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, where high Tg applications are more common.

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 PCB substrate materials as an important guarantee. The emergence and development of high-density mounting technologies represented by SMT and CMT have made PCBs more and more inseparable from the support of high heat resistance of substrates in terms of small aperture, fine wiring, and thinning.

Therefore, the difference between the general FR-4 and the high Tg FR-4: it is in the hot state, especially after moisture absorption.

Under heat, there are differences in the mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, and thermal expansion of the materials. High Tg products are obviously better than ordinary PCB substrate materials.

In recent years, the number of customers requiring the production of high Tg printed boards has increased year by year.

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 for substrate materials are as follows.

① National standards At present, my country’s national standards for the classification of PCB materials for substrates include GB/

T4721-47221992 and GB4723-4725-1992, the copper clad laminate standards in Taiwan, China are CNS standards, which are based on the Japanese JIs standard and were issued in 1983.

②Other national standards include: Japanese JIS standards, American ASTM, NEMA, MIL, IPc, ANSI, UL standards, British Bs standards, German DIN and VDE standards, French NFC and UTE standards, and Canadian CSA Standards, Australia’s AS standard, the former Soviet Union’s FOCT standard, the international IEC standard, etc.

The suppliers of the original PCB design materials are common and commonly used: Shengyi \ Jiantao \ International, etc.

● Accept documents: protel autocad powerpcb orcad gerber or real board copy board, etc.

● Sheet types: CEM-1, CEM-3 FR4, high TG materials;

● Maximum board size: 600mm*700mm (24000mil*27500mil)

● Processing board thickness: 0.4mm-4.0mm (15.75mil-157.5mil)

● The highest number of processing layers: 16Layers

● Copper foil layer thickness: 0.5-4.0(oz)

● Finished board thickness tolerance: +/-0.1mm(4mil)

● Forming size tolerance: computer milling: 0.15mm (6mil) die punching plate: 0.10mm (4mil)

● Minimum line width/spacing: 0.1mm (4mil) Line width control ability: <+-20%

● The minimum hole diameter of the finished product: 0.25mm (10mil)

The minimum punching hole diameter of the finished product: 0.9mm (35mil)

Finished hole tolerance: PTH: +-0.075mm(3mil)

NPTH: +-0.05mm(2mil)

● Finished hole wall copper thickness: 18-25um (0.71-0.99mil)

● Minimum SMT patch spacing: 0.15mm (6mil)

● Surface coating: chemical immersion gold, tin spray, nickel-plated gold (water/soft gold), silk screen blue glue, etc.

● The thickness of the solder mask on the board: 10-30μm (0.4-1.2mil)

● Peeling strength: 1.5N/mm (59N/mil)

● Hardness of solder mask: >5H

● Solder mask plug hole capacity: 0.3-0.8mm (12mil-30mil)

● Dielectric constant: ε= 2.1-10.0

● Insulation resistance: 10KΩ-20MΩ

● Characteristic impedance: 60 ohm±10%

● Thermal shock: 288℃, 10 sec

● Warpage of finished board: <0.7%

● Product application: communication equipment, automotive electronics, instrumentation, globaal positioning system, computer, MP4, power supply, home appliances, etc.