Low DK LAMINATES 2.17-3.9

The selection of substrate materials with tailored Dk and Df values is decisive for high‑frequency PCB designs. Total transmission loss, the core performance metric for RF circuits, consists of two dominant parts: conductor loss and dielectric loss, with radiation loss taken into account for open‑structure layouts. Conductor loss rises with copper surface roughness and operating frequency, while dielectric loss is governed by the material’s dissipation factor (Df). High‑performance laminates feature ultra‑low Df to suppress dielectric attenuation at millimeter‑wave bands. Radiation loss describes signal energy escaping from the transmission line; excessive radiation not only degrades power efficiency but also introduces crosstalk to adjacent traces.

Radiation loss is affected by trace geometry, substrate thickness, manufacturing tolerance, material Dk and working frequency. Circuits built on low‑Dk substrates normally generate higher radiation loss, whereas high‑Dk materials help confine the electromagnetic field and cut stray radiation. Meanwhile, the dielectric constant directly impacts circuit miniaturization: a lower Dk yields a longer guided wavelength, requiring larger layout dimensions for the same electrical length. For RF coupled‑line structures driven by fringing electric fields, field coupling intensity is strongly dependent on the Dk of the base material.

Given these trade‑offs between loss, radiation, component size and electromagnetic coupling, selecting the proper Dk‑Df material combination is indispensable to fine‑tune circuit behavior and satisfy target specifications across diverse high‑frequency scenarios.