FR4 guide for printed circuits

The characteristics of FR-4 or FR4 make it very versatile and affordable. This is why it is widely used in printed circuit production. FR4 tg130 is the most commonly used material for printed circuit boards. FR4 describes a class of flame retardant glass fiber epoxy laminates.

fr4 circuit board
fr4 circuit board

Properties and materials of FR4

  • FR4 is a standard defined by NEMA for glass reinforced epoxy laminates.
  • Fr stands for “flame retardant”, indicating that the material meets the UL94V-0 standard for flammability of plastic materials. The 94V-0 code can be found on all FR-4 PCBs. It ensures that the flame does not burn and can be extinguished quickly when burning.
  • For high Tg or Hitg, the glass transition temperature (TG) is about 115 ° C to 200 ° C, depending on the manufacturing method and the resin used. A standard FR-4 PCB will have a FR-4 layer sandwiched between two thin copper layers.
  • The FR-4 uses bromine, a fire-resistant so-called halogen chemical element. In most applications, it replaces the G-10, another low corrosion resistant composite.
  • FR4 has the advantage of good resistance weight ratio. It does not absorb water, maintains high mechanical strength, and has good insulation ability in dry or humid environment.

An example of FR4

  • Standard FR4: as the name suggests, this is the standard FR-4 with 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 copper laminate: ideal for insulation and plate support.
  • The characteristics of these different materials are described in detail later in this paper.

Why FR4?

The reasonable price of FR4 makes it a standard choice for small batch PCB production or electronic prototype production.

However, FR4 is not ideal for high frequency printed circuits. Similarly, if you want to make a PCB into a product that is not easy to use components and hardly suitable for flexible PCBs, you should choose another material: polyimide / polyamide.

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