ABOUT FR4

What is FR4? FR4 is a common material used in printed circuit manufacturing industry - PCB.

FR stands for Fire Retardant, meaning fire resistance. Thus FR material is a fire resistant material. After combining thin copper layers on the outside of FR fireproofing materials, materials were created to produce printed circuits.

Structure of FR4 material:

A common circuit board, the core can meet the rigidity and serve as a basis for making a circuit with copper on it. The FR4 core, outside of the task of rigidity and the foundation for the circuit, is also responsible for preventing the middle of the copper layers, creating an insulating dielectric layer between them.

For 2-layer printed circuit board, FR4 separates the top and bottom copper layers, for multi-layer printed circuitry, the FR4 PrePreg layers are added between the inner layer and the outer copper layer.

Creating the required thickness of PCB is done by adding or removing laminates to create different thicknesses.

For example, a FR4 circuit with a thickness of 1.6 mm is usually made of 8 layers of fiberglass. If you want FR4 printed circuit with a thickness of 0.8 mm, you can reduce it from 8 layers to 4 layers.

The name FR4 comes from the NEMU classification system in which ‘FR’ stands for cháy flame retardant ’, complying with UL94V-0 standard. You can see that FR4 is followed by TG130. The TG refers to the transition glass temperature - the temperature at which the glass reinforced material begins to deform and soften. For standard boards, this value is 130 ° C, which is more than enough for most applications. Special high TG materials can withstand temperatures of 170 - 180 ° C and can be ordered online by advanced PCB service.

Other types of PCBs are similar:

FR2: is a slower and cheaper fire material. they are used for mass production projects with low-end devices.

G10: is the predecessor of FR4, they are full-featured but replaced by FR4 with more safety.

 FR4 classification:

By class number: one class, two classes, or multiple classes
According to copper layer thickness: 0.5 oz, 1 oz, 2 oz, 3 oz
According to the link layer destruction temperature of materials TG130, TG 135, TG140, TG170, TG180