Embedding a Passive Material Layer in Low Temperature Co‐Fired Packing

Abstract

This work investigates co-sintering and magnetic property issues encountered during the fabrication of integral substrates composed of low temperature cofired ceramic (LTCC) insulators and nickel copper zinc ferrite inductor material. Co-sintering incompatibilities including glass redistribution, shrinkage rate, and sintering onset temperature were quantified. LTCC and ferrite densification temperatures differed by over 100°C. The depth of glass redistribution from the LTCC into the sintering ferrite layer followed the Rideal-Washbum equation, with a parabolic time dependence. Adjustment of ferrite densification by the addition of lead silicate glass sintering aids was explored, as was the effect of the glass additions on ferrite magnetic properties. Glass additions of 3, 5 and 8 vol. % were used to modify ferrite densification. Additions of 8 vol. % of low T g glasses were found adequate for the production of LTCC I Ferrite integral substrates. Ferrites with sintering aid glass additions had magnetic permeabilities of 60 to 80 H/mm and quality factors of over 100. This paper considers the specific integration of a ferrite material, but there are general aspects that are important for all integrated ceramic materials. In particular, the migration and redistribution of glass from the substrate and the use of glass additives to limit constrain sintering problems in LTCCs.