Routes to embedded inductors in MCM-L technology - design, CAD and manufacturing issues

This paper focuses on the design, fabrication and testing of magnetic components in MCM-L technology. The work is being carried out as part of a European Union funded Brite-EuRAM project, COMPRISE (BE 96-3371), the objective of which is to develop new materials and manufacturing processes to embed passive components (R, L, C) within printed wiring structures fabricated from laminate materials. As a first step towards the integration of magnetic structures in MCM-L, this paper describes the design of single and double layered air-core spiral inductors. The adaptation of an existing PCB and MCM-L CAD tool to design and layout the devices is discussed. This will be used to create a cell library of integrated spiral inductors. Models of frequency dependant impedance are presented which include the parasitic effects of resistance and capacitance. Using these models, inductance values up to 15 μH are designed to fit within a footprint area of 5×5 mm². Typical predicted Q-values are in the 60-140 range for single layered devices, and 20-60 for two winding layers. The possibility of increasing the inductor Q-value is also investigated. The self resonant frequency predicted is of the order of 1 GHz for single layered devices, and 100's of MHz for 2-layered devices.