What is FR4 board

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asked Feb 26, 2021 in H&E by MayNa (420 points)

As the basic material of PCB, fr4 board is very popular among electrical engineers and designers. This material's low cost, versatility and rich beneficial physical properties make it very popular. FR4 sheet is an electrical insulator with high dielectric strength. They also have a high strength-to-weight ratio, and are lightweight and moisture resistant. When added to their relative temperature resistance, FR4 performs well under most environmental conditions.

FR4 board connection
These qualities make FR4 an ideal default substrate for high-quality PCB manufacturing processes. If these attributes are used correctly, they can also form the basis of high-quality and low-cost PCBs.

In the PCB, FR4 constitutes the main insulation backbone. This is the basis for manufacturing companies to build circuits. When ready, the FR4 board will be laminated with one or more layers of copper foil through heating and bonding. This copper forms the circuit in the final product and may cover one or both sides of the board, depending on the board design.

Complex PCBs may use more than one side of the circuit board, and may even use multilayer circuit boards to produce more complex circuits. From here on, before covering with solder resist, the circuit is drawn out and etched to prepare for the final screen printing layer and subsequent soldering process.

FR4 board and high frequency laminate
So, using all the information listed above, how can an electrical engineer or PCB designer choose between FR4 and high frequency laminate? First, the designer must use the most specific parameters to list and compare the electrical and mechanical requirements of the final PCB. Then, designers must check how FR4 meets these parameters compared to laminates designed to handle high-frequency signals. Using industry data tables can easily obtain more accurate data for each of these points.

In short, FR4 is a widely related material that is popular mainly due to its low cost and relative mechanical and electrical stability. Although this material has a wide range of advantages and is available in various thicknesses and sizes, it is not the best choice for every application, especially high-frequency applications such as radio frequency and microwave designs. In the latter case, high-frequency laminates are a better choice. However, it is easy to see why FR4 is still so widely used today.

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