High Frequency Characterization of Ajinomoto Build-Up (ABF) Laminates for Millimeter Wave Applications

In this paper, the high-frequency properties of two dielectric materials (A and B) used in the fabrication process of flip-chip enhanced quad flat no-leads package (FCeQFN) is reported in the WR5 band $(140 \mathrm{GHz}-220 \mathrm{GHz})$ for the first time using free-space quasi-optical spectrometer (FSQS) technique. The materials are Ajinomoto Build-up Film-based laminates that drive the FCEQFN technology. Material A and B show an average dielectric constant of 3.33 and 3.45, respectively, with an average loss tangent of 0.01 across the WR5 band. The results are compared alongside the measurements using the Fabry-Perot resonator in the WR3 band($\mathbf{2 2 0 G H z} -\mathbf{3 3 0} \mathbf{G H z}$). The paper reports the characterization technique, measurement requirements, material processing challenges, and possible solutions to extract the frequency response over a wide range of frequencies.