What is FR4 material in PCB?

1.What is FR4 and its advantage?


FR-4 material, short for glass fiber cloth.

The epoxy glass fiber cloth copper clad plate has following advantage:

  • high strength
  • good heat resistance
  • good dielectric property

FR4 concept:

Of caurse, the through hole of the substrate can be metallized to realize the circuit continuity between double-sided multi-layer printing layers and layers.

The epoxy glass fiber cloth copper clad plate is the most widely used and used type of copper clad plate of all qualities. It is a kind of raw material and base material of circuit board, and the code of fire resistant material grade, which means that the resin material must be able to extinguish itself after burning.

The FR-4 is most commonly used in PCB (printed circuit board). These FR-4 is build the common single, double and multilayer PCB circuit boards!  Because of its high strength and flame retardancy, most circuit boards will choose FR-4 as the base material.

FR4 Advantage:

The general technical indicators of FR-4 sheet materials include: bending strength, peel strength, thermal shock performance, flame retardancy, volume resistance coefficient, surface resistance, dielectric constant, dielectric loss tangent, glass transition temperature Tg, dimensional stability, maximum service temperature, warpage, etc.

2.What is PCB and its composition?

PCB is the abbreviation of Printed Circuit Board in English. PCB is an important electronic component. It is the supplier of electrical connection of electronic components.

Do you know the PCB starts from the most basic unit: substrate. There are several layers on substrate. And of course, these layer plays an important role in the function of the final PCB.

These alternate layers include:

  • Base material: This is the basic material of PCB. It makes the PCB rigid.
  • Copper: Add a thin conductive copper foil on each functional surface of the PCB – on one side if it is a single-sided PCB, and on both sides if it is a double-sided PCB. This is the copper wiring layer.
  • Solder resistance layer: the top of the copper layer is a solder resistance layer, which gives each PCB a unique green color. It makes the copper trace unintentionally contact with other conductive materials that may cause short circuit. In other words, solder keeps everything in place. The holes in the solder mask are where solder is applied to connect the components to the circuit board. Moreover, the solder mask is a key step in the smooth manufacturing of PCBA, because it can prevent welding on unnecessary parts and avoid short circuit.
  • Silk screen: The white silk screen is the last layer on PCB. This layer adds labels on the PCB in the form of characters and symbols. This helps with the functionality of each component on the dashboard.


PCB varies according to its substrate materials, including high-frequency microwave plate, metal substrate, aluminum substrate, iron substrate, copper substrate, double-sided plate and multilayer plate. Normally, we use circuit in PCB to conducting between components.

When we design, the engineer add large copper surface as the grounding and power supply layer.  Of course, the engineer build the lines and drawings at the same time. The wiring density is high, the volume is small, and the weight is light, which is conducive to the miniaturization of electronic equipment.

The base plate of the board itself is made of insulating and heat-insulating materials that are not easy to bend. The small circuit material visible on the surface is copper foil. Originally, the copper foil was covered on the whole board. But during the manufactureing process the part of copper will  be etched. Therefor,  the left part became a small network circuit.

3.Advantages and characteristics of FR-4

Generally, FR-4 made the single, double and multilayer PCB boards. FR in FR-4 represents flame retardant, while the number 4 distinguishes this material from other materials in this category. FR-4 is a glass fiber reinforced epoxy laminate. The FR4 looks like a thin woven cloth board. The term FR-4 also represents the grade used to manufacture these laminates.

Glass fiber structure provides structural stability for materials. The flame retardant epoxy resin cover the glass fiber layer. This brings durability and strong mechanical properties to the material. All these features make FR-4 PCB very popular among electronic contract manufacturers.

Its technical features mainly lie in: electrical insulation, stability, good flatness, smooth surface, no pits, and thickness tolerance standard.

Which are suitable for products with high-performance electronic insulation requirements. Such as:

  • FPC reinforcement plate
  • PCB drilling pad, glass fiber meson
  • potentiometer carbon film printed glass fiber plate
  • precision planetary gear (wafer grinding)
  • precision test plate
  • electrical (electrical) equipment insulation brace partition
  • insulation pad Transformer insulation plate
  • motor insulation parts, grinding gear
  • electronic switch insulation plate

FR-4 sheet is now widely used in:

  • military
  • communications
  • computers
  • digital circuits
  • industrial instruments
  • automotive circuits
  • other electronic products

All performance indicators can meet the needs of general industrial electronic products. Very good price performance ratio.

see more