Magnetic-dielectric assembly

Abstract

A magnetic-dielectric disc assembly includes a magnetic ceramic disc coaxially secured within a dielectric ceramic ring by an adhesive that includes a powdered ceramic in an epoxy matrix. The powdered ceramic is selected from the group consisting of alumina, titania, silica, and zirconia. The magnetic-dielectric disc assembly can be used as a component of, for example, a circulator, isolator, or similar electrical assembly.

1 . A magnetic-dielectric assembly comprising a magnetic ceramic disc coaxially secured within a dielectric ceramic ring by an adhesive that includes a powdered ceramic in an epoxy matrix, the powdered ceramic selected from the group consisting of alumina, titania, silica, and zirconia. 
     
     
         2 . The magnetic-dielectric assembly of  claim 1  wherein the magnetic ceramic disc includes yttrium-iron-garnet and the dielectric ceramic ring includes MgO—CaO—ZnO—Al 2 O 3 —TiO 2 . 
     
     
         3 . The magnetic-dielectric assembly of  claim 1  mounted in an electrical device coupled to a radio frequency electric circuit. 
     
     
         4 . The magnetic-dielectric assembly of  claim 3  wherein the electrical device is at least one of a circulator and an isolator. 
     
     
         5 . The magnetic-dielectric assembly of  claim 1  wherein the epoxy matrix has a dielectric constant lower than a dielectric constant of the powdered ceramic. 
     
     
         6 . The magnetic-dielectric assembly of  claim 1  wherein the epoxy matrix has a thermal conductivity lower than a thermal conductivity of the powdered ceramic. 
     
     
         7 . The magnetic-dielectric assembly of  claim 1  wherein the powdered ceramic includes substantially spherical particles with a median diameter in a range of from about 0.1 micrometers to about 10 micrometers. 
     
     
         8 . The magnetic-dielectric assembly of  claim 1  wherein the adhesive includes from about 0.4 to about 1.2 grams of powdered ceramic per gram of epoxy. 
     
     
         9 . The magnetic-dielectric assembly of  claim 1  wherein the powdered ceramic has a purity of greater than about 99%. 
     
     
         10 . The magnetic-dielectric assembly of  claim 1  having a thickness of between about 1 millimeter and about 10 millimeters. 
     
     
         11 . The magnetic-dielectric assembly of  claim 10  having a variation in thickness of less than 0.025 mm. 
     
     
         12 . The magnetic-dielectric assembly of  claim 1  wherein the epoxy matrix and the powdered ceramic provide the adhesive with a dielectric constant such that an insertion loss at a frequency of 900 MHz of a microwave isolator including the magnetic-dielectric assembly is decreased by about 0.2 decibels relative to an assembly of substantially the same materials except having an adhesive free of the powdered ceramic. 
     
     
         13 . The magnetic-dielectric assembly of  claim 1  wherein the epoxy matrix and the powdered ceramic provide the adhesive with sufficient thermal conductivity such that during cutting of the magnetic-dielectric assembly the adhesive does not melt. 
     
     
         14 . The magnetic-dielectric assembly of  claim 1  wherein the powdered ceramic has a thermal conductivity of at least 0.08 cal/(sec·cm·K). 
     
     
         15 . The magnetic-dielectric assembly of  claim 1  wherein the dielectric ceramic ring includes MgO—CaO—ZnO—Al 2 O 3 —TiO 2 . 
     
     
         16 . The magnetic-dielectric assembly of  claim 1  wherein the magnetic ceramic disc includes yttrium-iron-garnet. 
     
     
         17 . The magnetic-dielectric assembly of  claim 1  wherein the powdered ceramic reduces an amount of adhesive on a surface of a blade of a saw when the magnetic-dielectric assembly is cut with the saw. 
     
     
         18 . The magnetic-dielectric assembly of  claim 1  wherein an outer annular surface of the magnetic ceramic disc is separated from an inner annular surface of the dielectric ceramic ring by a gap having a width of greater than about 10 micrometers. 
     
     
         19 . The magnetic-dielectric assembly of  claim 18  wherein the gap is filled with the adhesive. 
     
     
         20 . The magnetic-dielectric assembly of  claim 1  having a diameter of from 10 millimeters to 40 millimeters.