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Knowledge of FR4 PCB Circuit Board

Fr stands for flame retardant. FR4 is a glass fiber epoxy laminate, and FR-4 is an international design for flame retardant (self extinguishing) glass fiber reinforced epoxy laminate. It is the most commonly used PCB material. Copper clad laminate (CCL) is formed by adding copper layer on one side or each side of FR4, which is the non-conductive core material of ordinary printed circuit board (PCB). The printed circuit board with FR4 as the core material will be called “FR4 PCB”.


The 1.60mm FR4 uses 8 layers (7628) of fiberglass. The red UL / manufacturer logo is located in the middle (Tier 4). There are two types of logos: red and blue. Ul94-v0 in red and ul94-hb in blue. If you are using a blue logo material, it can be XPC (phenolic) or G10 (glass epoxy); these are older materials. Today, the main use of the G10 is for thin watch circuits – because it’s easy to punch. In the 1.50 / 1.60mm FR4, the logo is located in the middle layer (layer 4) of the common 8-layer structure.

FR4 PCB Circuit Board

PCBs are used to mechanically support and electrically connect electronic components through conductive paths, routing or signal routing etched from copper clad laminate substrates. Sometimes a PCB is also called a printed circuit board (PWB) or an etched circuit board if no additional electronic components are added.

FR4 is designed for high density multilayer boards, suitable for surface mount multilayer, mcm-l, direct chip connection, automotive and wireless communications. The characteristics of FR4 also make it particularly suitable for mass production of thin wire multilayer and PCMCIA applications.

The predictability and consistency of this material provide great convenience for the processing of circuit board manufacturing site. Its electrical and mechanical properties make it user-friendly for designers and manufacturers of key circuits.

PCB materials for flex and rigid flexible applications

Flexible and rigid – flexible circuit boards are becoming more and more popular due to their unique applications. Flexible and rigid – flexible circuit boards can do things that normal standard rigid circuit boards can’t do. They can be folded, twisted and wrapped in narrow / small packaging areas.

Most flexible circuit boards are made of DuPont’s “Kapton” material. The material based on polyimide film has heat resistance, dimensional stability and low dielectric constant of 3.6. There are three variants of Kapton material

Pyralux LF (acrylic based adhesive, non flame retardant) pyralux fr (acrylic based flame retardant) pyralux AP (no adhesive – suitable for high performance applications with higher requirements)

Example of FR-4

  • Standard FR4: as the name suggests, this is the standard FR-4, which has a heat resistance of about 140 ° C to 150 ° C.
  • High Tg FR4: This FR-4 has a high glass transition (TG) of about 180 ° C.
  • High CTI FR4: the comparison tracking index is higher than 600 v.
  • FR4 without laminated copper: very suitable for insulation board and board support.



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