This invention describes materials
system and
processing conditions for manufacturing
magnetic circuit components such as induction coils and transformers that are non wire-wound, miniature in size and, have a low manufacturing cost. The materials
system of this invention is comprised of: (1) Low Temperature Cofire
Ceramic (LTCC) tapes or thick film pastes of ferromagnetic ceramics with a 20 to 750 range of magnetic permeability to form the
magnetic core of the components, (2) Thick film buried silver conductor paste to form the planar induction coils on individual magnetic
layers, (3) Thick film via-fill silver conductor paste to interconnect two or more of the planar induction coils through the thickness of the magnetic
layers, (4) Thick film silver solderable top layer conductor paste compatible with the ferrite and, (5) Thick film
dielectric paste with low magnetic permeability to redirect the
magnetic flux for enhancing the magnetic
coupling coefficient and to insulate the silver conductors for enhancing the
dielectric breakdown voltage. The key characteristics of the materials
system of this invention that facilitate manufacture of low cost non wire-wound, miniature
magnetic circuit components are: (1) Mutual compatibility essential for either of the techniques, the cofire technique or the sequential technique, used for manufacturing multilayer
hybrid microelectronic components, (2) Complementary thermo-physical properties such as shrinkage and
thermal expansion coefficient essential for manufacturing flat multilayer
magnetic components, (3)
Magnetic components with magnetic
coupling coefficients greater than 0.95 under optimal
processing conditions and, (4)
Magnetic components with
dielectric breakdown voltage greater than 500V / mil under optimal
processing conditions.