# US 11,452,202 B2 · Radio frequency filtering of printed wiring board direct current distribution layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,452,202 B2 - Document ID: US11452202B2 - Status: Granted - Kind: B2 - Application number: 17/123,408 - Filed: 2020-12-16 - Published: 2022-06-16 - Granted: 2022-09-20 - Earliest claimed: 2020-12-16 - Assignees: Raytheon Company - Applicants: Raytheon Company - Inventors: John W. Hauff; Orlando F. Perez; John F. Magnani - Web page: https://patentgrep.com/patent/US11452202B2 ## CPC - H05K 1/0233: {Filters, inductors or a magnetic substance} - H05K 1/024: {Dielectric details, e.g. changing the dielectric material around a transmission line} - H05K 1/0225: {Single or multiple openings in a shielding, ground or power plane (H05K1/0227 takes precedence)} - H05K 1/0373: {containing additives, e.g. fillers (H05K1/036 takes precedence)} - H05K 3/4673: {Application methods or materials of intermediate insulating layers not specially adapted to any one of the previous methods of adding a circuit layer (similar methods for protective coatings H05K3/28)} - H05K 3/4676: {Single layer compositions} - H05K 1/0218: {by printed shielding conductors, ground planes or power plane (H05K1/0236 takes precedence)} - H05K 2201/0215: Metallic fillers - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS ## Abstract A method of fabricating a printed wiring board (PWB) includes etching traces to carry direct current (DC) on a first surface of a first epoxy-based layer. The first epoxy-based layer includes radio frequency (RF) absorber material. The method also includes arranging a second epoxy-based layer. The second epoxy-based layer includes the RF absorber material and includes a first surface in contact with the first surface of the first epoxy-based layer such that the traces are sandwiched between the first epoxy-based layer and the second epoxy-based layer. ## Claims ### Claim 1 A printed wiring board (PWB) comprising: a layer of traces configured to carry direct current (DC), wherein at least one of the traces is a DC supply line for a circuit in another layer of the PWB; a first epoxy-based layer, wherein the layer of traces is on a first surface of the first epoxy-based layer, the first epoxy-based layer including radio frequency (RF) absorber material; and a second epoxy-based layer, the second epoxy-based layer including the RF absorber material and including a first surface in contact with the first surface of the first epoxy-based layer such that the traces are sandwiched between the first epoxy-based layer and the second epoxy-based layer. ### Claim 2 (depends on 1) The PWB according to claim 1, wherein the first epoxy-based layer and the second epoxy-based layer include ferrite embedded in an epoxy layer. ### Claim 3 (depends on 1) The PWB according to claim 1, wherein the first epoxy-based layer and the second epoxy-based layer include iron embedded in an epoxy layer. ### Claim 4 (depends on 1) The PWB according to claim 1, further comprising a first ground plane, a first side of the first ground plane layer being in contact with a second side, opposite the first side, of the first epoxy-based layer. ### Claim 5 (depends on 4) The PWB according to claim 4, further comprising a second ground plane, a first side of the second ground plane layer being in contact with a second side, opposite the first side, of the second epoxy-based layer. ### Claim 6 (depends on 5) The PWB according to claim 5, wherein the first ground plane and the second ground plane are copper ground planes. ### Claim 7 (depends on 5) The PWB according to claim 5, further comprising additional layers arranged on a second side, opposite the first side, of the first ground plane layer and also on a second side, opposite the first side, of the second ground plane layer. ### Claim 8 (depends on 7) The PWB according to claim 7, further comprising pass-throughs in the first epoxy-based layer, the first ground plane layer, and one or more of the additional layers on the second side of the first ground plane layer. ### Claim 9 (depends on 7) The PWB according to claim 7, further comprising pass-throughs in the second epoxy-based layer, the second ground plane layer, and one or more of the additional layers on the second side of the second ground plane layer. ### Claim 10 (depends on 1) The PWB according to claim 1, wherein a length of the traces corresponds with a lowest frequency used by circuits of the PWB. ### Claim 11 A method of fabricating a printed wiring board, the method comprising: etching traces to carry direct current (DC) on a first surface of a first epoxy-based layer, the first epoxy-based layer including radio frequency (RF) absorber material and at least one of the traces being a DC supply line for a circuit in another layer of the PWB; and arranging a second epoxy-based layer, the second epoxy-based layer including the RF absorber material and including a first surface in contact with the first surface of the first epoxy-based layer such that the traces are sandwiched between the first epoxy-based layer and the second epoxy-based layer. ### Claim 12 (depends on 11) The method according to claim 11, wherein the first epoxy-based layer and the second epoxy-based layer include epoxy with ferrite embedded therein. ### Claim 13 (depends on 11) The method according to claim 11, wherein the first epoxy-based layer and the second epoxy-based layer include epoxy with iron embedded therein. ### Claim 14 (depends on 11) The method according to claim 11, further comprising arranging a first side of a first ground plane layer in contact with a second side, opposite the first side, of the first epoxy-based layer. ### Claim 15 (depends on 14) The method according to claim 14, further comprising arranging a first side of a second ground plane layer in contact with a second side, opposite the first side, of the second epoxy-based layer. ### Claim 16 (depends on 15) The method according to claim 15, wherein the first ground plane and the second ground plane are copper ground planes. ### Claim 17 (depends on 15) The method according to claim 15, further comprising arranging additional layers on a second side, opposite the first side, of the first ground plane layer and also on a second side, opposite the first side, of the second ground plane layer. ### Claim 18 (depends on 17) The method according to claim 17, further comprising forming pass-throughs in the first epoxy-based layer, the first ground plane layer, and one or more of the additional layers on the second side of the first ground plane layer. ### Claim 19 (depends on 17) The method according to claim 17, further comprising forming pass-throughs in the second epoxy-based layer, the second ground plane layer, and one or more of the additional layers on the second side of the second ground plane layer. ### Claim 20 (depends on 11) The method according to claim 11, further comprising controlling a length of the traces etched in the first surface of the first epoxy-based layer, wherein an increased length results in increased RF attenuation.