Terahertz Characterization of Glass-Based Materials and Stackups for 6 G Microelectronics Packaging

Glass-based materials, including polymer/glass stack ups, are attractive structural blocks for packaging substrates supporting 5 G and 6 G microelectronic modules and components. We present the first broadband characterization of AGC Inc. EN-A1 alkali-free boroaluminosilicate glass and of Ajinomoto Build-up Film (ABF) laminated on soda-lime float glass substrate from 200 GHz to 2.5 THz with a commercial terahertz time-domain spectroscopy (THz-TDS) system. The refractive index \(n(\nu )\), attenuation coefficient \(\alpha (\nu )\), permittivity \(\varepsilon '(\nu )\), and loss tangent \(\tan \delta (\nu )\) of EN-A1 glass as well as laminated ABF are \(n_\mathrm{EN-A1}=2.376\), \(\alpha _\mathrm{EN-A1}=31.1\) cm\(^{-1}\), \(\varepsilon '_\mathrm{EN-A1}=5.64\), \(\tan \delta _\mathrm{EN-A1}=0.062\), and \(n_\textrm{ABF}= 1.9\), \(\alpha _\textrm{ABF}= 30\) cm\(^{-1}\), \(\varepsilon _\textrm{ABF} = 3.8\), \(\tan \delta _\textrm{ABF}= 0.072\), all at 1 THz. Our results validate the promising perspective of both EN-A1 glass and ABF polymer materials as microwave and THz packaging solutions.