Arrangement of Thin Film Cores for Planar Coil Inductor

Miniaturized thin film inductors with various shaped magnetic cores are described. The dimensions of these inductors are about 2 mm × 2 mm. Since they are used at frequencies above 100 MHz, the effective utilization of the magnetic core must be considered. We measured the inductance of inductors with magnetic cores of various shapes, and investigated the flux density distribution. The inductors were based on from 100 to 240 core pieces, each piece with from one to three coil turns. The conductor of these inductors was confined to a single plane to prevent connection defects. According to measured results, the inductor with the highest inductance per unit area employed two-turn magnetic core pieces. There was no significant difference in the inductance of closed-loop and open-loop core constructions.