# US 11,908,599 B2 · Varistor and method for manufacturing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,908,599 B2 - Document ID: US11908599B2 - Status: Granted - Kind: B2 - Application number: 17/892,711 - Filed: 2022-08-22 - Published: 2023-03-16 - Granted: 2024-02-20 - Earliest claimed: 2021-08-31 - Assignees: Panasonic Intellectual Property Management Co., Ltd. - Applicants: Panasonic Intellectual Property Management Co., Ltd. - Inventors: Keiji Kawajiri; Naoki Mutou; Hironori Motomitsu; Michiya Watanabe; Yuji Yamagishi - Web page: https://patentgrep.com/patent/US11908599B2 ## CPC - H01C 7/102: Varistor boundary, e.g. surface layers (H01C7/12 takes precedence) - H01C 1/142: the terminals or tapping points being coated on the resistive element - H01C 7/1006: {Thick film varistors} - H01C 7/112: ZnO type - H01C 17/06546: {Oxides of zinc or cadmium} - H01C: RESISTORS ## Abstract A varistor includes a sintered body, an internal electrode, an insulating layer, and an external electrode. The internal electrode is disposed in an interior of the sintered body. The insulating layer covers at least part of the sintered body and includes Zn2SiO4. The external electrode is electrically connected to the internal electrode, covers part of the sintered body and part of the insulating layer, and is in contact with the part of the insulating layer. The insulating layer has a region being in contact with the external electrode, the region having a greater average thickness than a region of the insulating layer which is out of contact with the external electrode. ## Claims ### Claim 1 A varistor comprising: a sintered body; an internal electrode disposed in an interior of the sintered body; an insulating layer covering at least part of the sintered body and including Zn2SiO4; and an external electrode electrically connected to the internal electrode, covering part of the sintered body and part of the insulating layer, and being in contact with the part of the insulating layer, wherein: the insulating layer includes a region in contact with the external electrode, and the region has a greater average thickness than a region of the insulating layer which is out of contact with the external electrode. ### Claim 2 (depends on 1) The varistor of claim 1, wherein the sintered body includes ZnO. ### Claim 3 (depends on 1) The varistor of claim 1, wherein the external electrode includes Bi2O3. ### Claim 4 (depends on 3) The varistor of claim 3, wherein the sintered body includes no Bi2O3, or a mass concentration of Bi2O3 in the sintered body is lower than a mass concentration of Bi2O3 in the external electrode. ### Claim 5 (depends on 1) The varistor of claim 1, wherein the external electrode includes a primary external electrode disposed at a side of the sintered body and being in contact with a first region of the insulating layer, and a secondary external electrode covering the primary external electrode and being in contact with a second region of the insulating layer, the second region being different from the first region, and an average thickness of the second region of the insulating layer is greater than an average thickness of the first region of the insulating layer. ### Claim 6 (depends on 5) The varistor of claim 5, wherein the primary external electrode includes no Bi2O3, or a mass concentration of Bi2O3 in the primary external electrode is lower than a mass concentration of Bi2O3 in the secondary external electrode. ### Claim 7 A method for manufacturing a varistor, the method comprising: preparing a sintered body including ZnO as a main component and including an internal electrode disposed in an interior of the sintered body; forming a precursor layer including SiO2 or silicate such that the precursor layer covers at least part of the sintered body; applying an external electrode paste including Bi2O3 such that the external electrode paste covers part of the sintered body and is in contact with part of the precursor layer; performing heat treatment to form an insulating layer including Zn2SiO4 from the precursor layer and to form an external electrode from the external electrode paste. ### Claim 8 (depends on 7) The method of claim 7, wherein the insulating layer having a region being in contact with the external electrode, the region having a greater average thickness than a region of the insulating layer which is out of contact with the external electrode. ### Claim 9 (depends on 7) The method of claim 7, wherein the sintered body includes substantially no Bi2O3, or a mass concentration of Bi2O3 in the sintered body is lower than a mass concentration of Bi2O3 in the external electrode paste. ### Claim 10 (depends on 7) The method of claim 7, wherein a concentration of Bi2O3 in the external electrode paste is greater than or equal to 3% by mass and less than or equal to 30% by mass. ### Claim 11 (depends on 1) The varistor of claim 1, wherein the sintered body on which the insulating layer is formed has a flat surface, the insulating layer has a thickness from the flat surface of the sintered body in a depth direction of the sintered body. ### Claim 12 A varistor comprising: a sintered body; an internal electrode disposed in an interior of the sintered body; an insulating layer covering at least part of the sintered body and including Zn2SiO4; and an external electrode electrically connected to the internal electrode, covering part of the sintered body and part of the insulating layer, and being in contact with the part of the insulating layer, wherein: the sintered body on which the insulating layer is formed has a flat surface, and the insulating layer includes a region in contact with the external electrode, and the region has a greater average thickness from a surface of the insulating layer than a region of the insulating layer which is out of contact with the external electrode. ### Claim 13 (depends on 12) The varistor of claim 12, wherein the sintered body includes ZnO. ### Claim 14 (depends on 12) The varistor of claim 12, wherein the external electrode includes Bi2O3. ### Claim 15 (depends on 14) The varistor of claim 14, wherein the sintered body includes no Bi2O3, or a mass concentration of Bi2O3in the sintered body is lower than a mass concentration of Bi2O3 in the external electrode. ### Claim 16 (depends on 12) The varistor of claim 12, wherein the external electrode includes a primary external electrode disposed at a side of the sintered body and being in contact with a first region of the insulating layer, and a secondary external electrode covering the primary external electrode and being in contact with a second region of the insulating layer, the second region being different from the first region, and an average thickness of the second region of the insulating layer is greater than an average thickness of the first region of the insulating layer. ### Claim 17 (depends on 16) The varistor of claim 16, wherein the primary external electrode includes no Bi2O3, or a mass concentration of Bi2O3 in the primary external electrode is lower than a mass concentration of Bi2O3 in the secondary external electrode.