Characterization of ABF/Glass/ABF Substrates for mmWave Applications

Glass-based packaging presents unique opportunities for supporting 5G and beyond frequencies. In this work, we present the first broadband characterization results for the electrical properties of Ajinomoto build-up film (ABF) laminated on glass substrates. ABF/glass/ABF-based stack up has been characterized from 20 to 170 GHz. We also report the low-loss performance of ABF/glass/ABF transmission lines. The material stack up consists of a 100- μm-thick EN-A1 glass core from Asahi Glass Company (AGC) with 15- μm ABF GL102 laminated on both sides. Semiadditive process (SAP) has been used to metalize the stack up. A microstrip ring resonator (MRR) method has been used to extract the dielectric constant and loss tangent of the stack up. The dispersive model estimates the dielectric constant of the stack up to be ~4.72 for the entire frequency range with a variance of +0.1. The measured loss tangent values were 0.004, 0.009, and 0.012 at 23, 103, and 140 GHz, respectively. The electrical characterization results with a confidence interval of 95% have been reported. The average insertion loss for coplanar waveguide (CPW) lines in the frequency range was measured to be between 0.055 and 0.50 dB/mm. The average insertion loss for microstrip in the same frequency range was measured to be 0.12-0.62 dB/mm. Along with the good model to hardware correlation, the performance of the transmission lines has been compared with the insertion loss published for other substrate technologies.