Definition

Dielectric refers to the electrically insulating material separating conductive layers in a PCB, including laminate cores and prepreg. Key dielectric properties are dielectric constant (Dk, affecting impedance and signal speed), dissipation factor (Df, affecting signal loss), and dielectric strength (breakdown voltage). Dielectric thickness determines impedance for given trace widths. Materials are selected based on frequency, thermal, and mechanical requirements. Air (Dk=1) is the reference; common PCB dielectrics range from Dk=2.1 (PTFE) to Dk=4.5 (FR-4).