High-Performance Dielectric Substrate Development with Low Dk and Df for RF and mm-wave Applications

Official URL: https://risc01.sabanciuniv.edu/record=b2579274 _(Table of contents)

For almost ve decades, the industries were attracted towards silica- lled epoxy laminates due to their enhanced mechanical and electrical properties. Predominantly vast majority of the integrated circuits were packed by silica blended epoxy structures due to the ease of processability and cost reduction. However, in 5G applications, the signal that operates in the RF and mm-wave regions gets attenuated as it propagates along the PCB substrate made of epoxy-silica-based laminates. Hence, the need for low-loss laminates evolved to reduce the attenuation of the signal. The e ective dielectric properties need to be enhanced to develop a low-loss laminate. The e ective dielectric properties of the PCB laminate are strongly dependent on their building blocks. Thus, due to the heterogeneous nature of the PCB laminates, the e ective dielectric properties can be manipulated by the selection of host matrix, reinforcement type, or interfacial functionalization between these building blocks. The main parameters that a ect dielectric materials are the dielectric constant (Dk) and the dissipation factor (Df ) which is described by the ratio between the imaginary part and the real part of the complex permittivity. EM wave transition from free space to a medium of a higher relative permittivity ("r ), resulting in a slower velocity, shorter wavelength, and the amplitude will be reduced. More speci cally, PCB laminate design e orts are primarily based on minimizing the real part of the permittivity ("0) to reduce the capacitive coupling and minimize the imaginary part of the permittivity ("00) to reduce electrical loss. The primary objective of this study is the modelling and the development of a high-performance, low-cost PCB substrate that operates in RF and mm-wave applications. In order to achieve these speci cations, we have examined the particular building blocks of the PCB laminates and determined the targeted chemical structures of the host matrix and the speci c ber weave structures. However, due to the lack of prediction techniques of the e ective electrical and mechanical properties of the laminates, we have utilized multiple approaches to determine the e ective electrical and mechanical properties of the laminate structures. In terms of e ective electrical parameters, this thesis proposes two approaches: internal- eld and energy-based approaches. Thus, both proposed methods consider the concept of the representative unit cell, which provides three-dimensional control over the unit volume of a laminate. Using single and two-level homogenization techniques, obtained local dielectric properties were converted into an e ective dielectric property. With respect to the single level, the two-level homogenization technique creates an opportunity to extract e ective dielectric properties of multilayered laminates with a less computational load. Subsequently, both internal- eld and energy-based approaches were veri ed with common e ective medium approximations and compared with the measurement results between 20 GHz to 40 GHz. As a result in terms of the complex permittivity, the internal eld approach predicted the e ective Dk with a 2.5% error rate and the e ective Df predicted with 18.5% error rate with respect to the measurement results at 40 GHz. On the other hand, to extract the e ective mechanical properties, a two scale homogenization technique was proposed to examine the yarn behaviour of the laminate. These are yarn and laminate homogenization techniques. Thus, the simulation results of yarn homogenization were obtained to be inserted into the laminate homogenization scale.