Electrical Properties of Ceramic Substrates

Electrical parameters of interest for the ceramic substrates include volume resistivity, dielectric constant, dissipation factor, and dielectric strength 

The dielectric constant K is the measme of the ability of the material to store the electric charge relative to vacuinn, a dimensionless quantity. The dielectric constant value of ceramics varies at room temperature in the range from 5.5 to well above 10, depending on the type of ceramic (i.e., composition), the temperature and the frequency of operation, the particle size, and the purity of the material. The K values increase upon temperature increase for most ceramics. Often, dielectric constant values are provided with measurements conducted at 1 MHz. Measurements also indicate a strong dependence of the dielectric constant value on the frequency of operation a decline in K is often observed upon a frequency increase. Often, a low dielectric constant is desired to avoid capacitance effect. Typical values of K are 9.7, 6.8, 9.9, and 40, for conventional alumina, beryllia, AIN, and silicon carbide, respectively. 

The dissipation factor (DF), or dielectric loss, or loss tangent (tan 8) is a measure of the real or resistive component of a capacitor, and it does determine the energy loss from the material per cycle in the form of heat. With alternating voltages, the charge stored on the dielectric surface has both an in-phase or real component and an out-of-phase or imaginary component, caused by dielectric absorption or resistive leakage. DF is of the form 

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The electrical properties of ceramic substrates perform an important task in the operation of electronic circuits. Depending on the applications, the electrical parameters may be advantageous or detrimental to circuit function. Of most interest are the resistivity, the breakdown voltage or dielectric strength, and the dielectric properties, including the dielectric constant and the loss tangent. 

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