FR-4 double-sided copper-clad PCB sheet parameter classification
FR-4 sheet is a double-sided copper-clad PCB sheet made of epoxy resin + glass cloth + copper foil. If you highlight the performance of CCL products, there are three important indicators: dielectric constant, dielectric loss, TG value.
The commonly used FR4 copper clad laminate has a dielectric constant of 4.2-4.7 relative to air. This dielectric constant varies with temperature and can vary up to 20% over a temperature range of 0-70 degrees. A change in the dielectric constant results in a 10% change in line delay. The higher the temperature, the greater the delay. The dielectric constant also varies with the signal frequency. The higher the frequency, the smaller the dielectric constant. The typical dielectric constant of the design is 4.4.