# US 7,609,141 B2 · Flexible circuit having overvoltage protection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,141 B2 - Document ID: US7609141B2 - Status: Granted - Kind: B2 - Application number: 11/679,061 - Filed: 2007-02-26 - Published: 2007-06-28 - Granted: 2009-10-27 - Earliest claimed: 2002-04-08 - Assignees: Littelfuse, Inc. - Inventors: Edwin James Harris; Timothy Pachla; Tushar Vyas - Web page: https://patentgrep.com/patent/US7609141B2 ## CPC - H01C 7/12: Overvoltage protection resistors; Arresters - H01G 2/14: Protection against electric or thermal overload (by cooling H01G2/08) - H05K 1/0257: {Overvoltage protection} - H05K 1/167: {incorporating printed resistors} - H02H 9/044: {Physical layout, materials not provided for elsewhere (varistors H01C7/12; spark-gaps H01T; Ovshinsky devices H10N70/00)} - H05K 1/0259: {Electrostatic discharge [ESD] protection} - H05K 1/0298: {Multilayer circuits} - H05K 1/0393: {Flexible materials (H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups)} - H05K 3/28: Applying non-metallic protective coatings {(H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673)} - H05K 2201/0738: Use of voltage responsive materials, e.g. voltage switchable dielectric or varistor materials - H05K 2201/09763: Printed component having superposed conductors, but integrated in one circuit layer - H01C: RESISTORS - H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10) - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) ## Abstract A first voltage variable material (“VVM”) includes an insulative binder, first conductive particles with a core and a shell held in the insulating binder and second conductive particles without a shell held in the insulating binder; a second VVM includes an insulating binder, first conductive particles with a core and a shell held in the insulating binder, second conductive particles without a shell held in the insulating binder, and semiconductive particles with a core and a shell held in the insulating binder; a third VVM includes only first conductive particles with a core and a shell held in the insulating binder. ## Claims ### Claim 1 A flexible circuit having overvoltage protection comprising: a first flexible layer; a plurality of signal conductors applied to the first flexible layer; at least one ground conductor positioned adjacent to at least one of the signal conductors; a layer of voltage variable material (“VVM”) applied to the plurality of signal conductors and the at least one ground conductor such that a first path through the VVM from any of the signal conductors to the at least one ground conductor is smaller than a second path through the VVM from any of the signal conductors to a closest adjacent signal conductor; and a second flexible layer covering the signal conductors, the at least one ground conductor and the VVM, wherein the at least one ground conductor lies across the plurality of signal conductors, separated from the signal conductor by the VVM. ### Claim 2 (depends on 1) The flexible circuit of claim 1, wherein at least one of the first and second flexible layers is made of a material selected from the group consisting of: a ribbon, mylar, polyimide and an electrically insulated film. ### Claim 3 (depends on 1) The flexible circuit of claim 1, wherein the VVM includes a binder that is pliable enough such that it can be flexed with the flexible circuit without cracking. ### Claim 4 (depends on 1) The flexible circuit of claim 1, which includes an intermediate insulation layer between at least one of: (i) the signal conductors, (ii) the at least one ground conductor and (iii) VVM and the second flexible layer. ### Claim 5 (depends on 4) The flexible circuit of claim 4, wherein the intermediate insulative layer is made of a material selected from the group consisting of: (i) a dry film photo-imageable coverlay, (ii) a spray liquid photo-imageable coverlay and (iii) a glob-coating. ### Claim 6 (depends on 1) The flexible circuit of claim 1, which includes a silver ink coating applied to at least one of the signal conductors, the at least one ground conductor and the VVM. ### Claim 7 (depends on 1) The flexible circuit of claim 1, wherein the VVM covers at least substantially all of an entire surface of the signal conductors and the at least one ground conductor. ### Claim 8 (depends on 1) The flexible circuit of claim 1, wherein the VVM is applied to a portion of the signal conductors and the at least one ground conductor. ### Claim 9 (depends on 1) The flexible circuit of claim 1, wherein the at least one ground conductor and the VVM are in a z-direction relationship with the plurality of signal conductors. ### Claim 10 (depends on 1) The flexible circuit of claim 1, further comprising at least one of: (i) an internal insulating layer; and (ii) a intermediate silver ink coating. ### Claim 11 (depends on 1) The flexible circuit of claim 1, wherein the VVM includes one of: (i) an insulating binder, first conductive particles with a core and a shall held in the insulating binder, and second conductive particles without a shell held in the insulating binder; (ii) an insulating binder, first conductive particles with a core and a shell held in the insulating binder, second conductive particles without a shell held in the insulating binder, and semi-conductive particles with a core and a shell held in the insulating binder; and (iii) a insulating binder and only first conductive particles with a core and shell held in the insulating binder. ### Claim 12 A flexible circuit having overvoltage protective comprising: a first flexible layer; a plurality of signal conductors applied to the first substrate layer; a voltage variable material (“VVM”) applied to the plurality of signal conductors; a ground conductor applied to the VVM and across the signal conductors, wherein the ground conductor extends across the signal conductors to a ground trace applied to the first flexible layer; a first gap filled with the VVM between each adjacent signal conductor, the first gap larger than a second gap filled with the VVM between each signal conductor and the ground conductor; and a second flexible layer covering the signal conductors, the ground conductor and the VVM. ### Claim 13 (depends on 12) The flexible circuit of claim 12, which includes at least one of: (i) an internal insulating layer; and (ii) a intermediate silver ink coating. ### Claim 14 (depends on 12) The flexible circuit of claim 12, further comprising a plurality of signal conductors, each signal conductor lying adjacent to one of the ground conductors, separated by the VVM. ### Claim 15 A flexible circuit having overvoltage protection comprising: a first flexible layer; a signal conductor applied to the first flexible layer; a second flexible layer; a ground conductor applied to the second flexible layer; and a voltage variable material (“VVM”) located between the signal and ground conductors, wherein the VVM includes one of: (i) an insulating binder, first conductive particles with a core and a shell held in the insulating binder, and second conductive particles without a shell held in the insulating binder; (ii) an insulating binder, first conductive particles with a core and a shell held in the insulating binder, second conductive particles without a shell held in the insulating binder, and semi-conductive particles with a core and a shell held in the insulating binder; and (iii) a insulating binder and only first conductive particles with a core and shell held in the insulating binder. ### Claim 16 (depends on 15) The flexible circuit of claim 15, wherein at least one of the first and second flexible layers is made of a material selected from the group consisting of: a ribbon, mylar, polyimide and an electrically insulated film. ### Claim 17 (depends on 16) The flexible circuit of claim 16, the VVM separating the signal conductors and the ground conductor by a gap, each signal conductor spaced away from an adjacent signal conductor by a distance larger than the gap. ### Claim 18 (depends on 15) The flexible circuit of claim 15, which includes a plurality of signal conductors applied to the first flexible layer. ### Claim 19 A flexible circuit having overvoltage protection comprising: a first flexible layer; a plurality of signal conductors applied to the first flexible layer; at least one ground conductor positioned adjacent to at least one of the signal conductors; a layer of voltage variable material (“VVM”) applied to the plurality of signal conductors and the at least one ground conductor such that a first path through the VVM from any of the signal conductors to the at least one ground conductor is smaller than a second path through the VVM from any of the signal conductors to a closest adjacent signal conductor; and a second flexible layer covering the signal conductors, wherein the at least one ground conductor comprises a plurality of ground conductors, the VVM and each of the signal conductors in an x-y direction relationship with one of the plurality of ground conductors. ### Claim 20 A flexible circuit having overvoltage protection comprising: a first flexible layer; a plurality of signal conductors applied to the first flexible layer; at least one ground conductor positioned adjacent to at least one of the signal conductors; a layer of voltage variable material (“VVM”) applied to the plurality of signal conductors and the at least one ground conductor such that a first path through the VVM from any of the signal conductors to the at least one ground conductor is smaller than a second path through the VVM from any of the signal conductors to a closest adjacent signal conductor; and a second flexible layer covering the signal conductors, wherein each of the signal conductors lies adjacent to the at least one ground conductor, separated by the VVM.