Varistor and light-emitting apparatus

Abstract

A varistor comprises an element body, two external electrodes, and a metal conductor. The element body includes a portion having first and second faces opposing each other. Two external electrodes are arranged on the first face of the element body. The metal conductor is arranged on the second face of the element body. The metal conductor has a thermal conductivity higher than that of the element body. At least a region between the two external electrodes and metal conductor in the element body exhibits a nonlinear current-voltage characteristic. The heat transmitted to the varistor is efficiently diffused from the metal conductor in the varistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing the varistor in accordance with an embodiment.

FIG. 2 is a schematic plan view showing the varistor in accordance with the embodiment.

FIG. 3 is a schematic view showing a cross-sectional structure taken along the line III-III of FIG. 2.

FIG. 4 is a schematic view showing a cross-sectional structure taken along the line IV-IV of FIG. 1.

FIG. 5 is a schematic view showing a cross-sectional structure of the light-emitting apparatus in accordance with an embodiment.

FIG. 6 is a schematic view showing a cross-sectional structure of the varistor in accordance with the first modified example of the embodiment.

FIG. 7 is a schematic view showing a cross-sectional structure of the varistor in accordance with the second modified example of the embodiment.

FIG. 8 is a schematic perspective view showing the varistor in accordance with the third modified example of the embodiment.

Claims

1. A varistor comprising: an element body including a portion having first and second faces opposing each other;two external electrodes arranged on the first face of the element body; anda metal conductor, arranged on the second face of the element body, having a thermal conductivity higher than that of the element body;wherein at least a region between the two external electrodes and metal conductor in the element body exhibits a nonlinear current-voltage characteristic.

2. A varistor according to claim 1, wherein the metal conductor has a first surface in contact with the second face of the element body, a second surface opposing the first surface, and a third surface extending so as to connect the first and second surfaces to each other; andwherein the element body further comprises a portion formed so as to be continuous with the portion having the first and second faces of the element body and be in contact with the third surface of the metal conductor.

3. A varistor according to claim 2, wherein the element body further comprises a portion formed such as to be continuous with the portion formed in contact with the third surface of the metal conductor and be in contact with the second surface of the metal conductor.

4. A varistor according to claim 2, wherein, in a cross section, perpendicular to an opposing direction of the metal conductor and two external electrodes, passing the metal conductor, the metal conductor has an area ratio of at least 20% but not more than 99.7%, where the total area of the metal conductor and element body is 100%.

5. A varistor according to claim 1, wherein a thickness between the two external electrodes and metal conductor in the element body is at least 10 μm but not more than 200 μm.

6. A varistor according to claim 1, wherein a thickness of the metal conductor in the opposing direction of the metal conductor and two external electrodes is at least a thickness between the two external electrodes and metal conductor in the element body.

7. A varistor according to claim 1, wherein the metal conductor has a volume ratio of at least 10% but not more than 99.7%, where the total volume of the element body and metal conductor is 100%.

8. A varistor comprising: an element body;a metal conductor, arranged within the element body, having a thermal conductivity higher than that of the element body; andtwo external electrodes arranged on an outer surface of the element body so as to oppose the metal conductor;wherein at least a region between the two external electrodes and metal conductor in the element body exhibits a nonlinear current-voltage characteristic.

9. A varistor according to claim 8, wherein, in a cross section, perpendicular to an opposing direction of the metal conductor and two external electrodes, passing the metal conductor, the metal conductor has an area ratio of at least 20% but not more than 99.7%, where the total area of the metal conductor and element body is 100%.

10. A varistor according to claim 8, wherein a thickness between the two external electrodes and metal conductor in the element body is at least 10 μm but not more than 200 μm.

11. A varistor according to claim 8, wherein a thickness of the metal conductor in the opposing direction of the metal conductor and two external electrodes is at least a thickness between the two external electrodes and metal conductor in the element body.

12. A varistor according to claim 8, wherein the metal conductor has a volume ratio of at least 10% but not more than 99.7%, where the total volume of the element body and metal conductor is 100%.

13. A light-emitting apparatus comprising: the varistor according to claim 1; anda semiconductor light-emitting device connected physically and electrically to the two external electrodes so as to be connected in parallel to the varistor.

14. A light-emitting apparatus comprising: the varistor according to claim 8; anda semiconductor light-emitting device connected physically and electrically to the two external electrodes so as to be connected in parallel to the varistor.