Characterization of a planar spiral inductor on a composite-resin low-impedance substrate and its application to microwave circuits

The Q-factors of planar spiral inductors built on a polyimide-SiO/sub 2/-Si substrate are characterized as a function of the polyimide thickness. We found that inductor quality as high as that on a GaAs-microwave and millimeter-wave integrated circuit (MMIC) requires a polyimide thickness of over 100 /spl mu/m, resulting in a Q-factor of over 17. The applicability of a low-impedance substrate was confirmed through the investigation of a novel RF-MCM in a face-up-type structure for cellular phone systems using a composite epoxy resin-metallic substrate. A fabricated power amplifier module exhibited 28.5-dBm output power and 16% power efficiency at 1.75 GHz.