Shielded multilayer printed wiring board, high frequency, high isolation

• US 5,677,515 A
• Filed: 10/18/1991
• Issued: 10/14/1997
• Est. Priority Date: 10/18/1991
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Canyon, James Carl, Gower, Frederick M., Selk, Kenneth Charles, Hirsch, Harold J.
• Primary Examiner(s): TSO, LAURA K
• Application Number:
  US07/778,552
• Time in Patent Office: 2,188 Days
• Field of Search: 174/250, 174/255, 174/261, 174/262, 174/265, 174/35 R, 361/388, 361/386, 361/412, 361/414, 361/417, 361/424
• US Class Current: 174/255
• CPC Class Codes: H05K 1/0221 Coaxially shielded signal lines comprising a continuous shielding layer partially or wholly surrounding the signal lines
• CPC Class Codes: H05K 2201/09036 Recesses or grooves in insulating substrate recess in metallic substrate H05K2201/09745
• CPC Class Codes: H05K 2201/09981 Metallised walls
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 9/0039 Galvanic coupling of ground layer on printed circuit board [PCB] to conductive casing printed shielding conductors, ground planes or power planes for reduction of cross-talk or noise in printed circuits H05K1/0218

Abstract

A shielded printed wiring board is disclosed which provides electrical and magnetic isolation for the signal layers located thereon. The printed wiring board includes a signal layer laminated between two non-conductive dielectric layers. The bottom side of the printed wiring board has a conductive layer coated thereon. Grooves are routed through the printed circuit board on both sides of each signal layer extending from the top layer partially through to the conductive layer. Conductive metallic coatings are then provided to coat the board and thereby encapsulate the signal layer in a ground envelope, separated by a controlled thickness dielectric. In an alternate embodiment, a plurality of layers are laminated one on top of the other to provide a multilayer printed wiring board.

Claims

1. A shielded printed wiring board which isolates signal layers thereon, said printed wiring board comprising:

a first conductive signal layer having bottom and top surfaces;

a first non-conductive layer on the bottom surface of said first signal layer, said first non-conductive layer extending beyond opposite sides of said first signal layer;

a second non-conductive layer extending over the top surface of said first signal layer and said first non-conductive layer;

a conductive base layer having a top surface supporting the first non-conductive layer;

first and second grooves on opposite sides of said first signal layer and displaced therefrom, said grooves having walls extending through said first and second non-conductive layers and at least to said conductive base layer; and

a conductive coating substantially covering the top of the second non-conductive layer and the walls of the grooves thereby cooperating with the base layer to provide a conductive shielding substantially surrounding the signal layer.

2. The printed wiring board as defined in claim 1 further comprising:

access means for accessing said first signal layer, said access means including a plurality of openings extending from said first signal layer; and

a plurality of wires, said wires being inserted through said plurality of openings and connected to said first signal layer.

3. The printed wiring board as defined in claim 1, further comprising:

a second conductive signal layer having bottom and top surfaces;

a third non-conductive layer disposed on a bottom surface of said conductive base layer and having a top and bottom surface, the top surface of said second signal layer being defined on the bottom surface of said third non-conductive layer, with the top surface of said third non-conductive layer being connected to said conductive base layer;

a fourth non-conductive layer extending below said second signal layer and the bottom surface of the third non-conductive layer;

third and fourth grooves routed on opposite sides of said second signal layer and displaced therefrom, said third and fourth grooves having walls extending through said third and fourth non-conductive layers and at least to said conductive base layer; and

a second conductive coating substantially encapsulating the bottom of the fourth non-conductive layer, as well as the walls of said third and fourth grooves so as to provide a conductive shielding substantially surrounding the second signal layer.

4. The printed wiring board as defined in claim 3 further comprising:

interconnection means including a plated through hole for connecting said first signal layer to said second signal layer, said plated through hole being isolated from said conductive base layer.

7. The printed wiring board as defined in claim 1 further comprising:

access means including at least one hole extending into said board and exposing the signal layer; and

conductor means including at least one conductor extending into each of said holes and providing electrical connection to said signal layer.

8. The printed wiring board as defined in claim 1 further comprising a plurality of conductive signal layers disposed between said first and second non-conductive layers and each of said signal layers having said first and second grooves formed displaced from the sides thereof.

5. A shielded printed wiring board which isolates signal layers thereon said wiring board comprising:

a signal layer including a fiat conductor;

a first non-conductive layer having a sheet of controlled dielectric material with top and bottom surfaces, said signal layer being defined on the top surface of said first non-conductive layer;

a second non-conductive layer having a sheet of controlled dielectric material with top and bottom surfaces, said signal layer and top surface of said first non-conductive layer being laminated to the bottom surface of said second non-conductive layer;

a conductive base layer extending across the bottom surface of said first non-conductive layer;

first and second grooves routed along the sides of said signal layer and displaced therefrom, said grooves having walls extending through said first and second non-conductive layers and at least to said conductive base layer;

a conductive coating encapsulating the plurality of layers and grooves of said wiring board thereby providing a conductive shielding surrounding the signal layer; and

access means for accessing said signal layer to form electrical connection therewith.

6. The printed wiring board as defined in claim 5 wherein said access means comprises:

a plurality of openings extending outward from said signal layer; and

a plurality of wires, said wires being inserted through said plurality of openings and connected to the signal layer.

9. A circuit board comprising:

an electrically conductive base layer;

a first layer of non-conductive material disposed on top of said conductive base layer;

an electrically conductive signal transmission line disposed on top of a portion of said first layer of non-conductive material;

a second layer of non-conductive material disposed on top of said signal transmission line and said first layer of non-conductive material, said first and second layers of non-conductive material extending beyond opposite sides of said signal transmission line;

conductive grooves formed along opposite sides of said signal transmission line and separated therefrom, said grooves having walls extending through said first and second layers of non-conductive material at least to said conductive base layer and providing electrical contact therewith; and

an electrically conductive material substantially covering the top of said second layer of non-conductive material and said walls so as to form a conductive shield substantially surrounding said signal transmission line.

10. The circuit board as defined in claim 9 further comprising a plurality of signal transmission lines formed between said first and second layers of non-conductive material and having conductive grooves formed along sides of each of said signal transmission lines for providing conductive shields substantially surrounding each of said signal transmission lines.

11. The circuit board as defined in claim 9 wherein said circuit board is a multiple layer circuit board which further comprises:

a third layer of non-conductive material disposed on bottom of said conductive base layer;

a second electrically conductive signal transmission line disposed on bottom of a portion of said third layer of non-conductive material;

a fourth layer of non-conductive material disposed on bottom of said second signal transmission line and said third layer of non-conductive material;

third and fourth grooves routed along opposite sides of said second signal transmission line and displaced therefrom, said third and fourth grooves having walls extending through said third and fourth layers of non-conductive material at least to said conductive base layer; and

a second electrically conductive coating substantially covering the bottom of said fourth layer of non-conductive material and said walls so as to form a conductive shield substantially surrounding said second signal transmission line.

12. The circuit board as defined in claim 11 further comprising:

interconnection means including a plated through hole internally connecting said first signal transmission line to said second signal transmission line.