Engineering RF Dielectric Material to Enable 5G/6G Antenna Devices

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The electrical and thermomechanical properties of dielectric materials primarily determine the performance of high-speed circuitry fabricated on PCB laminate technology. Therefore, a recommended practice for PCB fabrication is to implement characterization methodologies that provide relevant information about the material's performance in realistic scenarios. Hence, rather than limit characterization to solely obtaining nominal data at particular frequencies by assuming signal propagation in a direction of best performance, the material characteristics should be analyzed in different directions and positions. This gives the designer a clearer idea of how much variation to expect in an actual implementation, in contrast to ideal conditions that are typically assumed to simplify the design cycle. 

In selecting a laminate material for a high-speed/frequency antenna design, the composite material properties are critical parameters that will determine if the antenna patches and network of interconnects to be fabricated can meet the loss, timing delay, and impedance match requirements of the application. PCB laminates are typically manufactured in two ways: 

1. By impregnating and strengthening a woven fiberglass fabric with resin.
2. Reinforcing the resin system with non-woven fibers or alternative fillers to control the coefficient of thermal expansion.  

In addition to optimal electrical properties, dielectric materials for high speed/frequency applications are engineered to exhibit improved thermal reliability, dimensional stability, and low moisture absorption. The resin matrix at the core of these systems has greatly evolved from standard epoxy to olefin chemistries which exhibit the desired electrical properties of PTFE-like substrates, but also offer ease of processing and low reliability risk. 

To read this entire article, which appeared in the March 2022 issue of PCB007 Magazine, click here.