Basic properties of Dielectric Materials of PCB
1. Thermal properties
Glass transition Temperature
Decomposition Temperature
Thermal conductivity
Coefficient of thermal expansion
2. Electrical properties:
Dielectric constant
Loss tangent or dissipation factor
Dielectric constant(Er): It is important for signal integrity and impedance considerations at
high frequency applications. Er value in the range of 2.5 to 4.5.Dielectric constant decreases
with increase in frequency.
Loss Tangent or Dissipation factor (Df):
Df is the tangent of phase angle between the resistive and reactive currents in the dielectric.
The dielectric loss increases with increasing values of Df. Low value of Df results in a fast
substrate and large value of Df results in a slow substrate. Df increases slightly with
frequency. For high frequency materials with very low values of Df, which low variation with
frequency.
Df Value ranges from 0.001 to 0.030
PCB material selection:
Basic material categories:
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