Low profile power inductors based on ferromagnetic LTCC technology

Abstract

Based on a compliant LTCC (low temperature co-fired ceramic) material system which allows the integration of soft magnetic NiCuZn ferrite layers in combination with Au and Ag thick film conductors, ultra low profile inductances of thickness between 200 and 400 mum have been developed and characterized. The designs of toroidal and spiral inductors of size between 2 and 6 mm were optimized. Inductance values in a range of between 1 and 10 muH at currents of up to 1 A and q-factors up to 30 at frequencies up to 1 MHz have been obtained. The DC resistance was between 40 and 200 mOhm depending on the number of windings. Inductance values and q-factors were measured as function of frequency, DC-bias and AC current. These inductors can be used for DC-DC converters for portable electronics or micro systems where the device height is of major concern