MAGNETIC-DIELECTRIC ASSEMBLY
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.