Broadband Characterization of Newly Developed ABF Type A Material for Advanced Packaging and mmWave Applications

To meet the performance demands of 6G and sub-terahertz (sub-THz) systems, advanced packaging technologies require new materials with low dielectric loss and high stability. This paper presents the first broadband characterization of a newly developed Ajinomoto Build-up Film® (ABF) Type A laminated on glass substrates. The dielectric properties were evaluated from 10 GHz to 220 GHz using the microstrip ring resonator (MRR) method, while microstrip lines on 30$\mu \mathrm{m}$thick ABF A were fabricated via a Semi-Additive Patterning (SAP) process to assess insertion loss. The measured dielectric constant remained nearly constant at 3.45 ± 0.05, and the loss tangent increased gradually from 0.002 at 10 GHz to 0.009 at 220 GHz. The microstrip lines exhibited average insertion loss from 0.08 dB/mm to 0.39 dB/mm across the same frequency range. Compared to the widely used ABF Type B, Type A variant demonstrates significantly lower loss at higher frequencies. These findings highlight the potential of ABF Type A as a promising candidate for low-loss interconnects and high-frequency packaging in future 6G and sub-THz wireless applications.