High frequency circuit materials are used in a variety of printed circuit board (PCB) applications. Some of these applications are for digital circuitry and others are based on RF technology. Understanding the areas of concern for the application and how certain material properties interact with those concerns, can be critical for the success of an RF application or digital circuitry.
It is well known that RF applications operating at lower microwave frequencies typically use dielectric materials with thicker substrates. It is also well known that as frequencies increase, a thicker substrate can cause problems related to wave propagation properties. Due to this issue and other related issues, using a thinner substrate for the PCB is typically necessary for applications operating at millimeter-wave frequencies. When the substrate is relatively thin, the circuit is much more sensitive to copper surface roughness and other conductor related issues. Additionally, the radars which operate at these frequencies are extremely sensitive to phase response
This presentation will explain several material and circuit properties which can affect millimeter-wave radar performance. The topics covered will start with a discussion on copper surface roughness variation and its impact on insertion loss and phase response. Also discussed will be thermal coefficient of dielectric constant, also known as TCDk. Some information will be given on glass weave effect as well as final plated finish. Measured data will be given in support of these topics, which will range from about 1 GHz to 80 GHz.