Circuit-board materials for high-frequency designers are akin to paper for writers. Although we can both learn to work in the virtual worlds of simulation and word processors within a computer, the real proof of an effort appears on a circuit board or on paper, for others to use. In both cases, we have learned to live with the limitations of these fundamental building blocks. For example, all circuit-board materials dissipate energy and suffer losses. Ideally, a substrate material could have the dielectric constant of air and losses from one point to another in a circuit would be almost nonexistent. In reality, the material does suffer losses, and exhibits variations in performance over time and temperature, just as a sheet of paper grows yellow with age.
But high-frequency designers are a clever bunch, and have learned to account for the imperfections of circuit-board materials in their computer simulations and real-world designs. And materials developers, for their parts, have done wonders in developing a wide range of circuit-board dielectric and laminate materials to fit the needs of many different applications. This short column is hardly the place to present the latest information on circuit-board materials. Those interested in more information won't want to miss a Special Report by Editor Nancy Friedrich, in the March issue of Microwaves & RF. It will cover not just circuit-board materials, such as PTFE and LTCC, but other materials instrumental to electronic design, such as sealants and shielding gaskets.