CPW high Q inductors on organic substrates

The development of integrated passive components suitable for integration with printed wiring boards is relatively recent. This integration is required since in most mixed signal designs, off-passive components take up more real estate on the boards than the analog and digital signal processing units. Besides utilizing real estate on board, embedded passives on organic laminates significantly reduce cost and if optimized have less parasitics compared to discrete passive components. This paper discusses the design of high Q coplanar waveguide (CPW) planar inductors on laminates. The reason for choosing a CPW type layout is the ease in adding shunt elements and series elements compared to stripline and microstrip configurations. A max Q factor of 85 at 5.2 GHz was obtained for a 1.85 nH CPW type inductor. Several other inductors with similar performances were studied which are also presented. The paper also presents a method to model the CPW type inductors. This approach allows designers to include metal-to-dielectric interface roughness, nonuniform signal line profiles and frequency dependent parameters such as the dielectric constant of materials.