FR4 is a kind of code of fire resistant material grade, represented by the mean resin material after combustion state must be able to put out a material specification, it is not a material name, but a level of material, so the general FR4 grade materials used in the circuit board has a lot of kinds, but most are based on the so-called four functions (Tera - Function) of epoxy resin and Filler (Filler) and glass fiber made of composite materials.
It is mainly a kind of refractory material after epoxy resin and glass fiber pass high temperature and high pressure, and it is also a main material for PCB production at present. Heat resistance up to 300 degrees, operating frequency up to several GHz, dielectric constant about 4.3.
Some common characteristics of glass fibers are as follows:
A. High strength: Glass is extremely strong compared to other textile fibers. In some applications, the strength/weight ratio even exceeds that of iron wire.
B. Heat and fire resistance: Glass fiber is inorganic, so it will not burn
C. Chemical resistance: it is resistant to most chemicals, and is not subject to infiltration of mold, bacteria and insect attacks.
D. Moisture resistance: Glass does not absorb water and retains its mechanical strength even in very humid conditions.
E. Thermal properties: the glass fiber has a very low linear expansion coefficient, and high thermal conductivity coefficient, so in the high temperature environment has excellent performance.
F. Electrical properties: Fiberglass is a good choice for insulation due to its non-conductivity.
The E - grade glass used for PCB substrate is mainly due to its excellent water resistance. Therefore, in very humid, harsh environments, still maintain very good electrical and physical properties as dimensional stability.
The FR - 4 is defined by the NEMA specification: LI1-1983, refers to the test of glass fiber epoxy resin sample burning, its size is 5 inches long, 0.5 inches wide, the thickness of the informal without copper substrate, in particular the Bunsen burner, under the sample put 45 degrees of inclined try to burn the light, then remove the fire and let already with flame retardant agent (e.g., 20% of the bromide) sheet of self extinguishing, and take the clock down from the "spread" the number of seconds after the fire. After ten test burns, the total number of seconds of burning less than 50 seconds is called V-0, and less than 250 seconds is called V-1. Any glass fiber epoxy board conforming to V-1 is called FR-4.
Besides fr-4 materials commonly used in PCB, other high functional high Tg resins are included, such as BT, Polymide, Cyanate Ester and PTFE. However, fr-4's low price, good adhesion, low moisture absorption and other advantages are not matched by other resins, so most PCBS are made of FR-4 materials
Copper-clad Laminate (CCL) is an important component of P-C board. It is composed of copper foil (leather), resin (meat), reinforcing materials (bone), and other functional reinforcing additives (tissue).
PC board type layer number
Application field
Paper phenolic resin single and double panels
(FR1 & FR2)
TV, monitor, power supply, stereo, photocopier, VCR, calculator, telephone, playing instrument, keyboard
Epoxy resin composite substrate single, double panel
(CEM1&CEM3)
Television, monitor, power supply, advanced audio, telephone, playing Musical Instruments, automobile electronic products, mouse, electronic notepad
Glass fiber cloth epoxy single and double panels
(FR4 )
Adapter card, computer peripheral equipment, communication equipment, wireless telephone, watch, playing musical instrument
Glass fiber cloth epoxy resin multilayer board
(FR4 & FR5)
Desktop computer, notebook computer, palmtop computer, hard disk machine, word processor, pager, mobile phone, IC card, digital TV and audio, fax machine, automobile industry, military equipment.