Charge Displacement
Material behavior under an external electric field involves the temporary shift of bound charges within a non conductive substrate. Dielectric polarization occurs when the molecular structure of the resin and reinforcement reacts to the voltage potential by forming internal dipoles. This mechanism dictates the ability of the PCB laminate to store electrical energy.
The resulting alignment affects the signal propagation speed and the overall capacitance of the circuit traces.
Permittivity Factor
Signal integrity in high speed designs relies on the stability of the substrate response across different operating frequencies. As the frequency increases, dielectric polarization may lag behind the oscillating field, leading to energy loss. This phenomenon contributes to the dissipation factor of the material.
Laminates are selected based on their ability to minimize these parasitic effects.
Molecular Friction
Heat generation within the board stackup often stems from the rapid reorientation of dipoles during high frequency switching. When dielectric polarization is inefficient, the converted energy appears as thermal rise in the dielectric layer. High frequency materials use specific resin systems to reduce the friction associated with this movement.
Low loss laminates maintain signal strength over longer distances by controlling this internal reaction. This physical constraint defines the upper frequency limit for standard epoxy glass composites.
