Development of a Novel Printed Circuit Board Technology for Inductive Device Applications

This paper describes the fabrication and characterisation of 2-dimensional inductive devices integrated inside printed circuit boards . PCB and flex-foils. These devices basically are composed of three layers of which the outer layers bear the printed coil patterns and the inner layer is a high permeability ferromagnetic sheet core. Both magnetic metal and copper layers are patterned using standard lithographic techniques. Electroplated interconnections between the outer layers complete the windings. We have fabricated both transformers and fluxgate magnetic field sensing devices with a thickness of 200 mm for the flex-foil devices and 600 mm for the PCB-based devices. Lateral dimensions are approximately 1 cm. We realise relatively high inductances of 1–10 mH at a frequency of 1 kHz for the transformers and a magnetic field detection limit of 43 mT at 20 kHz for the fluxgate devices.