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FR4 sheet parameters and conventional thickness

Time : 2023-11-24 Hits : 3

A. FR-4 Sheet Parameters are Categorized:dielectric constant parameters, dielectric loss parameters, TG value parameters.

FR-4 sheet is made of epoxy resin + glass cloth pressed together into a double-sided copper-clad PCB sheet, generally used FR4 copper-clad sheet, relative to the air dielectric constant is 4.2-4.7. This dielectric constant will change with the temperature, in the temperature range of 0-70 degrees Celsius, the maximum range of change can be up to 20%. A change in dielectric constant will result in a 10% change in line delay, the higher the temperature, the greater the delay. Dielectric constant will also change with the signal frequency, the higher the frequency the smaller the dielectric constant, the general design of the dielectric constant of the classic value of 4.4.

The dielectric constant (Dk, ε, Er) determines the speed of propagation of electrical signals in the medium. The speed of electrical signal propagation is inversely proportional to the square root of the dielectric constant. The lower the dielectric constant, the faster the signal travels. Let's make an analogy, as if you are running on the beach, the depth of the water submerged your ankles, the viscosity of the water is the dielectric constant, the more viscous the water, represents the dielectric constant is higher, you run more slowly.

The dielectric constant is not very easy to measure or define. It is related not only to the properties of the medium itself, but also to the test method, the frequency of the test, and the state of the material before and during the test. The dielectric constant also varies with temperature, and some special materials are developed with temperature in mind. Humidity is also an important factor affecting the dielectric constant, because the dielectric constant of water is 70, very little moisture, can cause significant changes.

PCB (4)

FR4 sheet dielectric loss: insulating materials in the electric field, due to dielectric conductivity and dielectric polarization of the hysteresis effect, the energy loss caused by its internal. Also called dielectric loss, referred to as dielectric loss. Under the action of an alternating electric field, the residual angle δ of the angle between the current phase and voltage phase flowing in the dielectric (power factor angle Φ) is called the dielectric loss angle.FR4 sheet dielectric loss is generally 0.02, and the dielectric loss will increase with the increase of frequency.

FR4 sheet TG value: also known as glass transition temperature, generally 130 ℃, 140 ℃, 150 ℃, 170 ℃.

B. FR4 Sheet Conventional Thickness

Commonly used thickness: 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2.0mm, plate thickness error according to the plate factory's fabrication capacity.

FR4 copper laminates commonly used copper thickness: 0.5 ounces, 1 ounce, 2 ounces, other copper thicknesses are also available, you need to consult the PCB manufacturer to determine.


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