Millimeter-Wave Complex Permittivity of Silica/Alumina-Filled Epoxy-Molding Compounds
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Millimeter-Wave Complex Permittivity of Silica/ Alumina-Filled Epoxy-Molding Compounds Michael P. McGarry 1 & Enis Tuncer 2 & Mark Lee 1,3 Received: 11 June 2020 / Accepted: 7 July 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Composite materials made of micron-sized oxide particle fillers in an epoxy resin matrix that can be molded into desired shapes are widely used for packaging radiofrequency and microwave-integrated circuits (ICs). To potentially employ these materials with millimeter-wave ICs (MMICs), quantitative knowledge of the composites’ dielectric properties across a broad millimeter-wave band is necessary. Here, we present nondestructive measurements of the complex relative permittivity, εr = ε′ + jε″, on some possible MMIC packaging composites consisting of silica and/or alumina microsphere fillers dispersed in an epoxy matrix. Measurements using phase-sensitive transmission over the WR3 and WR5 frequency bands (140 to 325 GHz) show that ε′ ranged from 3.6 for pure silica filler to 7.2 for pure alumina filler, with very little frequency dispersion. In all materials, the loss tangent tanδ = ε″/ε′ was between 0.01 and 0.02 in this frequency range. An analysis using the theory of two-component composites is used to extract the real permittivity of the epoxy resin. The results could be used to model performance of packaged MMICs and to design composites having a tailored value of ε′. Keywords Dielectrics . Millimeter-wave integrated circuit . MMIC . Materials spectroscopy . Packaging materials, epoxy-molding compounds
1 Introduction Bringing broadband millimeter-wave integrated circuit (MMIC) electronics technology to commercial viability involves solving many design, engineering, and materials problems * Mark Lee [email protected]
1
Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA
2
Semiconducting Packaging, Technology & Manufacturing Group, Texas Instruments, Inc., Dallas, TX 75243, USA
3
Texas Analog Center of Excellence, The University of Texas at Dallas,, Richardson, TX 75080, USA
Journal of Infrared, Millimeter, and Terahertz Waves
beyond the obvious semiconductor chip level device and circuit challenges. One such problem is integrating a MMIC chip into a useful package [1–3], where the dielectric packaging material needs to provide mechanical and thermal support and protection while causing minimal degradation in electromagnetic performance. To properly understand and model the electromagnetic effects of packaging, it is necessary to know with good accuracy the behavior of the complex relative permittivity, εr = ε′ + jε″, of the packaging dielectric materials across the frequency range of interest (here, j is the unit imaginary number). It is also of interest to understand how the composition of a packaging material affects its permittivity, so that materials with desired dielectric properties such as a targeted value of ε′ or lower loss tangent, tanδ = ε″/ε′, may be designed. For most MMICs, the goal is a packa
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