Monolithic ceramic capacitor with internal conductor layers having different densities
A monolithic ceramic capacitor includes an element body having therein a multilayer portion formed of a plurality of conductor layers and a plurality of ceramic dielectric layers alternately stacked in a thickness direction; and a first outer electrode and a second outer electrode provided on an outer portion of the element body. The element body is divided in the thickness direction into a thickness-direction first outer layer portion, a thickness-direction second outer layer portion, and a thickness-direction inner layer portion located between the thickness-direction first outer layer portion and the thickness-direction second outer layer portion and including the multilayer portion. A first conductor layer and a second conductor layer, which are outermost layers among the plurality of conductor layers, have lower conductor densities than any of conductor densities of the other conductor layers.
1. A monolithic ceramic capacitor comprising:
an element body including a multilayer portion including a plurality of conductor layers and a plurality of ceramic dielectric layers alternately stacked in a thickness direction of the element body; and
an outer electrode provided on an outer portion of the element body; wherein
outer surfaces of the element body include a first principal surface and a second principal surface that are opposed to each other in the thickness direction, a first end surface and a second end surface that are opposed to each other in a length direction perpendicular or substantially perpendicular to the thickness direction, and a first side surface and a second side surface that are opposed to each other in a width direction perpendicular or substantially perpendicular to both the thickness direction and the length direction;
the element body is divided in the thickness direction into a thickness-direction first outer layer portion that includes a first ceramic dielectric layer and defines the first principal surface, a thickness-direction second outer layer portion that includes a second ceramic dielectric layer and defines the second principal surface, and a thickness-direction inner layer portion including the multilayer portion and located between the thickness-direction first outer layer portion and the thickness-direction second outer layer portion;
among the plurality of conductor layers included in the thickness-direction inner layer portion, a first conductor layer arranged at a position closest to the first principal surface is provided at a position adjacent to the first ceramic dielectric layer of the thickness-direction first outer layer portion;
among the plurality of conductor layers included in the thickness-direction inner layer portion, a second conductor layer arranged at a position closest to the second principal surface is provided at a position adjacent to the second ceramic dielectric layer of the thickness-direction second outer layer portion;
the outer electrode includes a first outer electrode provided to cover the first end surface, and a second outer electrode provided to cover the second end surface;
one portion of the plurality of conductor layers is connected to the first outer electrode through a first wiring portion extending from the multilayer portion toward the first end surface side;
another portion of the plurality of conductor layers is connected to the second outer electrode through a second wiring portion extending from the multilayer portion toward the second end surface side;
the element body is divided in the length direction into a length-direction first outer layer portion that includes portions of the conductor layer and the ceramic dielectric layer corresponding to the first wiring portion and defines the first end surface, a length-direction second outer layer portion that includes portions of the conductor layer and the ceramic dielectric layer corresponding to the second wiring portion and defines the second end surface, and a length-direction inner layer portion that includes the multilayer portion and is located between the length-direction first outer layer portion and the length-direction second outer layer portion;
a conductor density in a length-direction first end portion region located at the first end surface side in the multilayer portion, and a conductor density in a length-direction second end portion region located at the second end surface side in the multilayer portion are lower than a conductor density in a length-direction center portion region located at a center in the length direction in the multilayer portion;
the element body is divided in the width direction into a width-direction first outer layer portion that includes the ceramic dielectric layer and defines the first side surface, a width-direction second outer layer portion that includes the ceramic dielectric layer and defines the second side surface, and a width-direction inner layer portion that includes the multilayer portion and is located between the width-direction first outer layer portion and the width-direction second outer layer portion;
a conductor density in a width-direction first end portion region located at the first side surface side in the multilayer portion, and a conductor density in a width-direction second end portion region located at the second side surface side in the multilayer portion are lower than a conductor density in a width-direction center portion region located at the center in the width direction in the multilayer portion; and
the conductor densities of the first conductor layer and the second conductor layer are lower than the conductor densities in the length-direction first end portion region, the length-direction second end portion region, the width-direction first end portion region, and the width-direction second end portion region, by about 10%.
2. The monolithic ceramic capacitor according to claim 1 , wherein
the first conductor layer and the second conductor layer each include a plurality of fine through holes penetrating through the first conductor layer and the second conductor layer in the thickness direction; and
the plurality of through holes are filled with a ceramic dielectric material.
3. The monolithic ceramic capacitor according to claim 1 , wherein
a portion of the conductor layer connected to the second outer electrode and included in the length-direction first end portion region among the plurality of conductor layers, and a portion of the conductor layer connected with the first outer electrode and included in the length-direction second end portion region among the plurality of conductor layers include a plurality of fine through holes penetrating through the portions of the conductor layers in the thickness direction; and
the plurality of through holes are filled with the ceramic dielectric material.
4. The monolithic ceramic capacitor according to claim 1 , wherein
portions included in the width-direction first end portion region and the width-direction second end portion region among the plurality of conductor layers include a plurality of through holes penetrating through the conductor layers in the thickness direction; and
the plurality of through holes are filled with the ceramic dielectric material.
5. The monolithic ceramic capacitor according to claim 1 , wherein the first conductor layer and the second conductor layer are floating conductor layers not connected with the outer electrode.
6. The monolithic ceramic capacitor according to claim 1 , wherein the element body has a rectangular or substantially rectangular parallelepiped shape.
7. The monolithic ceramic capacitor according to claim 1 , wherein the plurality of ceramic dielectric layers include barium titanate.
8. The monolithic ceramic capacitor according to claim 7 , wherein the plurality of ceramic dielectric layers further include at least one of a Mn compound, a Mg compound, a Si compound, a Co compound, a Ni compound, and a rare-earth compound.
9. The monolithic ceramic capacitor according to claim 1 , wherein the plurality of conductor layers are made of Ni or Cu.
10. The monolithic ceramic capacitor according to claim 1 , wherein the outer electrode is defined by a multilayer film.
11. The monolithic ceramic capacitor according to claim 10 , wherein the multilayer film includes a sintered metal layer disposed on the outer portion of the element body and a plated layer disposed on the sintered metal layer.
12. The monolithic ceramic capacitor according to claim 11 , wherein the sintered metal layer is made of a sintered conductor paste including at least one of Cu, Ni, Ag, Pd, an Ag—Pd alloy, and Au.
13. The monolithic ceramic capacitor according to claim 11 , wherein the plated layer is one of a Cu plated layer and an Au plated layer.
14. The monolithic ceramic capacitor according to claim 1 , wherein a thickness of the first conductor layer and the second conductor layer is smaller than a thickness of the other conductor layer located between the first and second conductor layers.
15. The monolithic ceramic capacitor according to claim 1 , wherein edge portions and corner portions of the element body are rounded.