A material’s flammability, also known as flame retardancy, self-extinguishing flame resistance, flame retardancy, fire resistance, and flammability, is an assessment of a material’s ability to resist combustion.

A sample of a flammable material is ignited with a flame that meets the required standards. After a specified time, the flame is removed and the degree of combustion is determined based on the sample’s degree of flammability. There are three levels of flammability: horizontal testing with the sample placed horizontally, resulting in levels FH1, FH2, and FH3. Vertical testing with the sample placed vertically, resulting in levels FV0, FV1, and VF2.

What is the difference between HB and V0 PCB materials?

HB has low flame retardancy and is mostly used for single-sided boards. V0 has high flame retardancy and is mostly used for double-sided and multi-layer boards. This type of PCB material that meets V-1 fire rating requirements is called FR-4. V-0, V-1, and V-2 are fire ratings.

Circuit boards must be flame-resistant and must soften at a certain temperature, preventing them from burning. This temperature is called the glass transition temperature (Tg), and this value is crucial to the dimensional stability of the PCB.

What are high-Tg PCBs and the advantages of using them?

When the temperature of a high-Tg printed circuit board rises to a certain level, the substrate transitions from a "glassy" state to a "rubbery" state. This temperature is called the board’s glass transition temperature (Tg). In other words, Tg is the highest temperature at which the substrate maintains its rigidity.

What are the specific types of PCB materials?

The grades are classified from lowest to highest as follows:

94HB – 94VO – 22F – CEM-1 – CEM-3 – FR-4. Details are as follows: 94HB: Ordinary cardboard, not fireproof (lowest-grade material, requires die-punching, not suitable for power boards) 94V0: Flame-retardant cardboard (requires die-punching) 22F: Single-sided semi-fiberglass board (requires die-punching) CEM-1: Single-sided fiberglass board (requires computer-drilled holes, not die-punched) CEM-3: Double-sided semi-fiberglass board (besides double-sided cardboard, this is the lowest-end material for double-sided boards. Simple double-sided boards can use this material and are 5-10 yuan/square meter cheaper than FR-4) FR-4: Double-sided fiberglass board

Circuit boards must be flame-resistant and must soften at a certain temperature, preventing them from burning. This temperature is called the glass transition temperature (Tg), which affects the dimensional stability of the PCB.

What are High-Tg PCBs and the Advantages of Using High-Tg PCBs

When the temperature rises above a certain level, the substrate material transitions from a "glassy" state to a "rubbery" state. This temperature is called the board’s glass transition temperature (Tg). In other words, Tg is the highest temperature (°C) at which the substrate maintains its rigidity. This means that at high temperatures, ordinary PCB substrate materials not only soften, deform, and melt, but also experience a sharp decline in mechanical and electrical properties (I don’t think you’d want to see this happen to your own products after looking at the PCB classification).

The typical Tg of a board is above 130°C, with high Tg generally exceeding 170°C, and medium Tg above approximately 150°C. PCBs with a Tg ≥ 170°C are generally considered high-Tg. Raising the substrate’s Tg improves and enhances the board’s heat resistance, moisture resistance, chemical resistance, and stability. The higher the TG value, the better the board’s temperature resistance. High Tg materials are particularly common in lead-free manufacturing processes.

High Tg refers to high heat resistance. With the rapid development of the electronics industry, especially electronic products like computers, which are moving towards higher functionality and higher layers, PCB substrate materials require higher heat resistance as a key requirement. The emergence and development of high-density mounting technologies like SMT and CMT have made it increasingly necessary for PCBs to achieve smaller apertures, finer circuitry, and thinner profiles.

The difference between standard FR-4 and high-Tg FR-4 is that under heat, especially after absorbing moisture, the materials exhibit differences in mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, and thermal expansion. High-Tg products significantly outperform standard PCB substrate materials. In recent years, the number of customers requesting high-Tg printed circuit boards has increased year by year.

What are the key criteria for substrate materials?

With the development and continuous advancement of electronic technology, new requirements are constantly being placed on printed circuit board (PCB) substrate materials, driving the continuous development of copper-clad laminate (CCL) standards. Currently, the main standards for substrate materials are as follows.

① National Standards: Currently, China’s national standards for the classification of PCB substrate materials are GB/T 4721-4722-1992 and GB 4723-4725-1992. Taiwan’s CCL standard is the CNS standard, which was developed based on the Japanese JIS standard and was issued in 1983.

② Other major standards include: Japan’s JIS, the United States’ ASTM, NEMA, MIL, IPc, ANSI, and UL, the United Kingdom’s BS, Germany’s DIN and VDE, France’s NFC and UTE, Canada’s CSA, Australia’s AS, the former Soviet Union’s FOCT, and international IEC. Common and frequently used suppliers of raw PCB design materials include Shengyi, Jiantao, International, and South-Electronic.