Magnetic ceramic substrate, substrate manufacturing method, and circulator
A magnetic ceramic substrate includes a base material made of magnetic ceramic and a conductor pattern formed to be in contact with a surface of the base material. The surface of the base material is smooth, and the conductor pattern contains a metal conductor and amorphous glass. A circulator includes the magnetic ceramic substrate.
1 . A magnetic ceramic substrate comprising:
a base material made of magnetic ceramic that is garnet-type ferrite; and
a conductor pattern formed to be in contact with a surface of the base material,
wherein a value of Ra is 0.01 or more and 0.5 or less where Ra is a smoothness of the surface of the base material, and
wherein the conductor pattern is made of a metal conductor formed of Ag and amorphous glass that does not crystallize.
2 . The magnetic ceramic substrate according to claim 1 , wherein T sin −T sof is 100° C. or more and 300° C. or less where T sof is a softening temperature of the amorphous glass contained in the conductor pattern and T sin is a sintering temperature of the metal conductor contained in the conductor pattern.
3 . The magnetic ceramic substrate according to claim 1 , wherein part of a surface of the amorphous glass constituting the conductor pattern is bonded to the surface of the base material.
4 . The magnetic ceramic substrate according to claim 3 , wherein the surface of the amorphous glass partly bonded to the surface of the base material is, except for the part bonded to the surface of the base material, in contact with the metal conductor.
5 . The magnetic ceramic substrate according to claim 1 , wherein the conductor pattern has a thickness of 10 μm or more and 20 μm or less.
6 . The magnetic ceramic substrate according to claim 1 , wherein an amount of amorphous glass contained in the conductor pattern is 2 vol % or more and 12 vol % or less with respect to a volume of the conductor pattern.
7 . The magnetic ceramic substrate according to claim 1 ,
wherein the conductor pattern is constituted of a first-layer conductor pattern formed to be in contact with the surface of the base material, and a second-layer conductor pattern formed to be in contact with a surface of the first-layer conductor pattern,
wherein the first-layer conductor pattern is made of a metal conductor and amorphous glass that does not crystallize, and
wherein the second-layer conductor pattern is made of a metal conductor.
8 . A circulator comprising the magnetic ceramic substrate according to claim 1 .
9 . A magnetic ceramic substrate manufacturing method of manufacturing a magnetic ceramic substrate, the magnetic ceramic substrate manufacturing method comprising:
mirror-polishing a surface of a base material made of magnetic ceramic that is garnet-type ferrite such that a value of Ra is 0.01 or more and 0.5 or less where Ra is a smoothness of the surface of the base material;
applying a conductor paste made of a metal conductor formed of Ag and amorphous glass that does not crystallize by thick-film printing to the mirror-polished surface;
drying the conductor paste applied by thick-film printing; and
baking the dried conductor paste to the surface of the base material.
10 . The magnetic ceramic substrate manufacturing method according to claim 9 , wherein T sin −T sof is 100° C. or more and 300° C. or less where T sof is a softening temperature of the amorphous glass contained in the conductor paste and T sin is a sintering temperature of the metal conductor contained in the conductor paste.