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What do PCB designers moving into the RF space need to understand about material selection? ere are some very specific electrical proper- ties that are important when selecting materi- als for RF or HSD applications. e first is the dielectric constant (Dk) of the material. e Dk is the ability of the substrate to store electric energy in an electrical field. It is a dimension- less property and is quoted as a value relative to a vacuum, which has a Dk of 1. Why does it matter? It matters because it determines transmission speed and must be accounted for when calculating the timing and synchroniza- tion of high-speed signals; it is also crucial for impedance matching and control. e Dk is very much a design consideration, and specific designs may require higher or lower values. e other important property is the dissipa- tion factor (Df ), also known as loss tangent, tan delta, or dielectric loss. is is a measure of the energy lost as heat in a dielectric mate- rial when an electric field is applied. It is also dimensionless, and a lower value always means better performance. In addition to these sub- strate properties, the copper foil also has an important influence on loss and signal integ- rity. As frequency increases, the current tends to flow primarily near the surface of a con- ductor, rather than uniformly throughout its cross-section. is is known as the skin effect. Traditional copper foil has a pronounced tooth on one side, which means that due to the skin effect, the signal has a longer and higher resis- tance path on either side of the conductor, which leads to signal integrity loss. Ventec recently launched some new RF mate- rials. What design challenges do these mate- rials address? Ventec has a full range of RF and HSD materi- als, offering the designer a choice of Dk and Df matching their designs. We curate these into our tec-speed signal integrity and tec-speed RF ranges. Our tec-speed signal integrity materi- als cover the growing demand for high-reli- ability and high-speed computing and storage applications with one of the most comprehen- sive ranges of products available from mid-loss (Df 0.015) (Df at 10 GHz:0.0095) to ultra-low- loss (Df 0.002) (Df at 10 GHz:0.0009) with Dk levels at 10 GHz ranging between 3.8 and 3.1 Our tec-speed RF range offers Df values as low as 0.0009 and extends the available Dk range from 2.2 to 10.2 primarily serving the military, defense radar, airborne and automotive radar, cellular network systems, and satellite com- munication sectors along with general RF and microwave circuitry. Some designers have had success designing RF PCBs with traditional materials. What sort of tradeoffs do designers face using FR-4, etc., for their RF boards? Success or failure depends primarily on the design parameters and the loss budget. Rela- tively low-frequency designs with short trans- 12 DESIGN007 MAGAZINE I APRIL 2025 Alun Morgan