Process for shielding an electric or electronic circuit and shielding cap

• US 6,420,649 B1
• Filed: 05/18/1999
• Issued: 07/16/2002
• Est. Priority Date: 08/18/1996
• Status: Expired due to Term

• Current Assignee: Bernd Tiburtius, Helmut Kahl
• Original Assignee: Bernd Tiburtius, Helmut Kahl
• Inventors: Kahl, Helmut, Tiburtius, Bernd
• Primary Examiner(s): Browne, Lynne H.
• Assistant Examiner(s): BOCHNA, DAVID
• Application Number:
  US09/242,460
• Time in Patent Office: 1,155 Days
• Field of Search: 174/35.R, 174/35.GC, 174/35.MS, 277/316, 277/590, 428/35.8, 428/331, 428/423.1, 524/93, 521/76
• US Class Current: 174/377
• CPC Class Codes: H05K 9/0015 Gaskets or seals

Abstract

A process is disclosed for screening a part of an electrical or electronic circuit, which part is surrounded by an electrically-conductive frame, from absorbing and/or emitting electromagnetic interference fields. The process comprises taking an electrically-conductive screening cap, with an open side bordered by a rim that contains a seating surface, and forming an elastic and electrically-conductive screening seal by directly applying the sealing compound to the seating surface in such a way that the screening seal projects beyond the seating surface. The screening cap is then placed with the screening seal on the electrically-conductive frame to fix the screening cap on the electrically-conductive frame.

Claims

1. A process for screening a part of an electrical or electronic circuit which part is surrounded by an electrically-conductive frame, from absorbing and/or emitting electromagnetic interference fields, said process comprising the steps of:

taking an electrically-conductive screening cap the open side of which is bordered by a rim, said rim being provided with a seating surface;

forming an elastic and electrically-conductive screening seal by using a flowable and elastically hardening sealing compound, dipping said screening cap with said rim in a bath of said sealing compound such that said sealing compound adheres to said seating surface; and

removing said screening cap with said adhering sealing compound from said bath, to apply said sealing compound on said seating surface such that said screening seal projects beyond the seating surface;

placing said screening cap with said screening seal on said electrically-conductive frame; and

fixing said screening cap on said electrically-conductive frame.

2. A screening cap for screening a part of an electrical or electronic circuit from absorbing and/or emitting electromagnetic interference fields, said electrical or electronic circuit being arranged on a circuit board, and said part of said electrical or electronic circuit being surrounded by an electrically-conductive frame on said circuit board, whereby said screening cap comprises side walls which run essentially vertical with respect to said circuit board and which are bordered by seating surfaces adapted to make contact with said electrically-conductive frame on said circuit board when said screening cap is placed on said circuit board,

and whereby said seating surfaces are provided with an elastic and electrically-conductive screening seal that adheres to and projects beyond said seating surfaces.

3. A screening cap according to claim 2, characterized in that the seating surfaces are edges, and the screening seal is placed on the face of the edges.

4. A screening cap according to claim 2, characterized in that the seating surfaces are edges, and the screening seal surrounds the edges.

5. A screening cap according to one of claims 3, 4, or 2, characterized in that the screening seal has the shape of one or more sealing beads.

6. A screening cap according to one of claims 3, 4, or 2, characterized in that the screening seal consists of an electrically-conductive elastomer, especially based on silicone or polyurethane with electrically-conductive fillers.

7. A screening cover according to claim 6, characterized in that the electrically-conductive elastomer has an adhesive or wet consistency and can be hardened by heat or radiation.

8. A screening cap according to one of claims 3, 4, or 2, characterized in that the screening seal consists of an electrically-conductive thermoplastic or an electrically-conductive hot-melt adhesive.

9. A screening cap according to one of claims 3, 4, or 2, characterized in that the screening seal comprises a sealing core consisting of an electrically-insulating elastomer that is provided with a metal coating.

10. A screening cap according to one of claims 3, 4, or 2, characterized in that the screening cap consists of a metallized insulation.

11. A process for screening a part of an electrical or electronic circuit from absorbing and/or emitting electromagnetic interference fields, whereby said electrical or electronic circuit is arranged on a circuit board, and whereby said part of said electrical or electronic circuit is surrounded by an electrically-conductive frame on said circuit board, said process comprising the steps of:

taking an electrically-conductive screening cap with side walls which run essentially vertical with respect to said circuit board and which are bordered by seating surfaces adapted to make contact with said electrically-conductive frame on said circuit board when said screening cap is placed on said circuit board;

forming an elastic and electrically-conductive screening seal by directly applying an electrically-conductive sealing compound on said seating surfaces of said side walls such that said electrically-conductive screening seal adheres to and projects beyond said seating surfaces;

placing said screening cap with said electrically conductive screening seal on said electrically-conductive frame; and

fixing said screening cap to said circuit board.

12. A process according to claim 11, wherein said adhesive sealing compound is applied to said seating surfaces by:

using a flowable and elastically hardening sealing compound;

dipping said screening cap with said seating surfaces in a bath of said sealing compound such that said sealing compound adheres to said seating surfaces; and

removing said screening cap with said adhering sealing compound from said bath.

13. A process according to claim 11, characterized in that the sealing compound is applied in the form of at least one bead to the seating surfaces by a dispenser through a nozzle.

14. A process according to claim 13, characterized in that several sealing beads are applied on top of each other to from the screening seal.

15. A process according to one of the claims 2, 3, 11, or 12, characterized in that an electrically-conductive elastomer is used as the sealing compound.

16. A process according to claim 15, characterized in that an electrically-conductive elastomer based on silicone or polyurethane is used that contains electrically-conductive fillers.

17. A process according to one of claims 2, 3, 11, or 12, characterized in that an electrically-insulating elastomer is used as the sealing compound, and the sealing compound is provided with an electrically-conductive coating, especially in the form of metal coating after it is applied to the seating surfaces.

18. A process according to claim 17, characterized in that a screening cap is used that consists of an electrically-insulating material, and the screening cap and sealing compound are both provided with an electrically-conductive coating, especially in the form of metal cover, after the sealing compound has been applied to the seating surfaces.

19. A process according to one of the claims 2, 3, 11, or 12, characterized in that electrically-conductive or isotropic plastics are used as the sealing compound.

20. A process according to one of the claims 11 or 12, characterized in that the screening cap is mechanically fixed after it is placed on the frame.

21. A process according to claim 20, characterized in that auxiliary means are used to mechanically affix the cover, and the auxiliary means press the screening cap with the screening seal against the frame.

22. A process according to claim 21, characterized in that the auxiliary means comprise a spring clip.

23. A process according to claim 21, characterized in that the auxiliary means comprise a screw.

24. A process according to claim 21, characterized in that the auxiliary means comprise an opposing housing part.

25. A process according to claim 21, characterized in that the auxiliary means comprise spring sheet metal parts that are on the screening cover.

26. A process according to one of the claims 11 or 12, characterized in that the screening cap is adhered to the frame with the screening seal after it is placed on the frame.

27. A process according to claim 26, characterized in that an adhesive or wet electrically-conductive elastomer is used as the sealing compound.

28. A process according to claim 27, characterized in that the sealing compound is hardenable by heat or radiation, and it is hardened after the screening cap is placed on the frame.

29. A process according to claim 26, characterized in that an electrically-conductive thermoplastic or hot-melt adhesive is used as the sealing compound, and the screening cap is adhered after it is placed on the frame by increasing the temperature at the frame.