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.
The dielectric constant (Dk, ε, Er) of the FR4 copper clad plate determines the speed at which electrical signals propagate in the medium. The rate at electrical signals propagate is inversely proportional to the square root of the dielectric constant. The lower the dielectric constant, the faster the signal transmission speed. We make an image metaphor, just think that you are running on the beach, the water is drowning your ankle. The viscosity of water is the dielectric constant. The more sticky the water, the higher the dielectric constant and the slower you run.
The dielectric constant is not very easy to measure or define. It is not only related to the characteristics of the medium itself, but also to the test method, test frequency, pre-test and material state during the test. The dielectric constant also varies with temperature. Some special materials are developed with temperature in mind. Humidity is also an important factor affecting the dielectric constant because water has a dielectric constant of 70 and very little moisture. Will cause significant changes.
FR4-CCL dielectric loss: The energy loss caused by the insulation material under the electric field due to the hysteresis effect of dielectric conductance and dielectric polarization. Also called media loss, referred to as dielectric loss. Under the action of an alternating electric field, the angle δ of the angle between the current phasor flowing through the dielectric and the voltage phasor (power factor angle Φ) is called the dielectric loss angle. The dielectric loss of FR4 sheet is generally 0.02, and the dielectric loss will increase with the increase of frequency.
TG4 sheet TG value: also known as glass transition temperature, generally 130 ° C, 140 ° C, 150 ° C, 170 ° C.
FR4 sheet thickness
Commonly used thicknesses: 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2.0mm, the sheet thickness error depends on the production capacity of the sheet factory.
FR4 CCL is commonly used in copper thickness: 0.5 ounces, 1 ounce, 2 ounces, and other copper thicknesses. If necessary, please consult ZTELEC to provide FR-4 double-sided copper-clad PCB.