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WO1998015162A1 - Joint d'etancheite statique procurant blindage emi et etancheite vis a vis de l'environnement - Google Patents

Joint d'etancheite statique procurant blindage emi et etancheite vis a vis de l'environnement Download PDF

Info

Publication number
WO1998015162A1
WO1998015162A1 PCT/US1997/017524 US9717524W WO9815162A1 WO 1998015162 A1 WO1998015162 A1 WO 1998015162A1 US 9717524 W US9717524 W US 9717524W WO 9815162 A1 WO9815162 A1 WO 9815162A1
Authority
WO
WIPO (PCT)
Prior art keywords
gasket
board
perimeter edges
integrally formed
notch
Prior art date
Application number
PCT/US1997/017524
Other languages
English (en)
Inventor
Jon Paul Mittler
Patrick E. Nixon
Original Assignee
Ericsson Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ericsson Inc. filed Critical Ericsson Inc.
Priority to AU47401/97A priority Critical patent/AU4740197A/en
Publication of WO1998015162A1 publication Critical patent/WO1998015162A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K9/00—Screening of apparatus or components against electric or magnetic fields
    • H05K9/0007—Casings
    • H05K9/0015—Gaskets or seals

Definitions

  • the present invention relates generally to gaskets used in printed circuit (PC) boards and more specifically, to a gasket which functions as an environmental seal and prevents the transfer of electromagnetic interference (EMI) through gaps between a PC board and an EMI shield such as a metal case.
  • PC printed circuit
  • EMI electromagnetic interference
  • Circuit designs often include both digital and analog circuits, also known as mixed circuit designs.
  • a mobile radio includes both an analog circuit which forms radio frequency (RF) circuits and a digital circuit which forms control circuits.
  • Mixed circuit designs are highly susceptible to cross-talk due to propagation of EMI between the analog and digital circuits and are generally shielded from each other to minimize the propagation of EMI .
  • metal cases or lids are mounted on a PC board in order to isolate circuits which are sensitive to EMI .
  • a simple compressible gasket made of conductive or partially conductive material is often positioned around the perimeter of the circuit to be isolated between the rim of the metal case and the surface of the circuit.
  • an annular, circumferential gasket includes at least one circumferential notch on the inner surface of the gasket and at least one circumferential ridge on the outer surface of the gasket .
  • Figure 1 is a perspective exploded view of a gasket in accordance with the present invention and a PC board.
  • Figure 2 is a cross-sectional view of the assembled PC board and gasket assembly of Figure 1 with the gasket attached to the PC board in accordance with the present invention.
  • Figure 3 is a cross-sectional view of the PC board and gasket assembly of the present invention retained within a partially shown outer housing.
  • Figure 1 shows a perspective exploded view of a gasket 10 and a PC board 12 which is also referred as a first member in the claims.
  • the gasket 10 is formed of a resilient, flexible material, such as silicone rubber.
  • the gasket 10 is shown of a rectangular shape, it can also be of any other shape, and is preferably substantially the same shape as the PC board 12.
  • a unique feature of the gasket 10 is that unlike a conventional gasket which lays on the surface of a PC board, the gasket 10 wraps around the perimeter edges 13 of the PC board 12. This is accomplished by a circumferential notch 15 integrally formed into the gasket 10 along the perimeter of its inner surface 14. The perimeter of the circumferential notch 15 is slightly less than the perimeter of the PC board 12. When the gasket 10 is stretched and positioned around the perimeter edges 13 of the PC board 12, it contracts and wraps around the perimeter edges 13 of the PC board 12. The gasket 10 snugly fits around the perimeter edges 13 of the PC board 12, and is securely retained by the PC board 12. This wrap-around feature of the gasket 12 will be further discussed in conjunction with Figures 2 and 3.
  • FIG. 1 shows a cross-sectional view of a PC board assembly 16 comprising the gasket 10 and the PC board 12.
  • the PC board 12 includes a circuit trace 18 and ground traces 20.
  • the ground traces 20 are that portion of the printed wiring which is adapted to be connected to a source of ground potential and the circuit trace 18 is usually held at potential other than ground potential.
  • the method of construction of a PC board, including the ground trace and the circuit trace, is well known and need not be discussed herein.
  • Circuitry blocks 22 may comprise a plurality of elements, such as microprocessors, multiplexers, shift - registers etc., that are mounted on the top surface 24 of the PC board 10.
  • a metal case 26 is provided on the top surface 24 of the PC board 12 for shielding the circuitry blocks 22 from EMI.
  • an inner housing member 36 is provided to cover the bottom surface 25 of the PC board 10.
  • Inner housing member 36 may form a portion of the enclosure of the product. Surfaces of inner housing member 36 may be made conductive by various well-known means.
  • the inner surface 14 of the gasket 10 is coated with a conductive material 33, such as silver, which prevents EMI from propagating through the gasket 10.
  • the conductive material 33 on the inner surface 14 of the gasket 10 also provides electrical contact between the metal case 26 and the ground trace 20, and between the inner housing 36 and the ground trace 20. The result is that the circuitry blocks 22 are covered by the metal case 26, inner housing member 36, and gasket 10 and are shielded against EMI .
  • the inner surface 14 of the gasket 10 includes the circumferential notch 15 integrally formed into the gasket 10 along its perimeter.
  • the perimeter of the circumferential notch 15 is slightly less than the perimeter of the PC board 12 to cause the gasket 10 to snugly fit around the perimeter edges of the PC board 12.
  • the outer surface 28 of the gasket 10 includes at least one semi-circular, circumferential ridge 30 integrally formed onto the gasket .
  • a second circumferential ridge 31 is provided. The function of the circumferential ridges 30 and 31 is to provide environmental sealing, and this function will be further described with reference to Figure 3.
  • Figure 3 shows an outer housing or member 38, assembled over PC board 16 and inner housing 36.
  • the outer housing 38 is of a size such that circumferential ridge 30 is compressed radially between outer housing member 38 and inner housing member 36.
  • circumferential ridge 31 is compressed radially between the outer housing member 38 and the PC board 12.
  • the compression ridge 30 forms a perimeter seal between housing 38 and 36 which prevents the intrusion of contaminants into the product.
  • the compression of ridge 31 forms an additional perimeter seal as a safeguard against failure of the first seal.
  • the compression of ridges 30 and 31 also automatically centers PC board 12, inner housing 36, and metal case 26 within outer housing member 38.
  • a novel feature of the gasket 10 is that it controls alignment of the entire PC board assembly 16 because it retains the PC board 12 and the metal case
  • the gasket 10 controls alignment of the entire PC board assembly 16, and the housings 36 and 38, it creates compliant interfaces along EMI shielding boundaries and along environmental boundaries. Finally, it must be noted that the gasket 10 is a radially compressed gasket because it is wrapped around the PC board 12. The gasket 10 radially isolates the PC board 12 from shock and vibration which may be present in the outer housing 38.

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Abstract

Cette invention se rapporte à un joint d'étanchéité statique à double usage conçu pour assurer un blindage anti-induction électromagnétique (EMI) et l'étanchéité vis à vis de l'environnement d'une plaquette de circuits imprimés. Dans la réalisation préférée de la présente invention, un joint d'étanchéité statique circonférentiel et annulaire comporte au moins une encoche circonférentielle ménagée sur sa surface interne, qui fait partie intégrante du joint statique. La circonférence de l'encoche circonférentielle est inférieure à la circonférence de la plaquette de circuits imprimés. L'encoche circonférentielle s'accouple aux bords périphériques de la plaquette de circuits imprimés et maintient solidement la plaquette de circuits imprimés lorsque le joint statique est étiré autour des bords périphériques de la plaquette de circuits imprimés puis relâché.
PCT/US1997/017524 1996-10-04 1997-10-03 Joint d'etancheite statique procurant blindage emi et etancheite vis a vis de l'environnement WO1998015162A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU47401/97A AU4740197A (en) 1996-10-04 1997-10-03 Gasket for emi shielding and environmental sealing

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US72628996A 1996-10-04 1996-10-04
US08/726,289 1996-10-04

Publications (1)

Publication Number Publication Date
WO1998015162A1 true WO1998015162A1 (fr) 1998-04-09

Family

ID=24917984

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/017524 WO1998015162A1 (fr) 1996-10-04 1997-10-03 Joint d'etancheite statique procurant blindage emi et etancheite vis a vis de l'environnement

Country Status (2)

Country Link
AU (1) AU4740197A (fr)
WO (1) WO1998015162A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3930377A1 (de) * 1988-09-20 1990-03-29 Kitagawa Ind Co Ltd Dichtung mit elektromagnetischer abschirmung
EP0427550A2 (fr) * 1989-11-13 1991-05-15 Gichner Systems Group, Inc. Joint pour blindage contre des interférences électromagnétiques
US5205751A (en) * 1992-02-21 1993-04-27 Motorola, Inc. Electrically-conductive elastomeric connector

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3930377A1 (de) * 1988-09-20 1990-03-29 Kitagawa Ind Co Ltd Dichtung mit elektromagnetischer abschirmung
EP0427550A2 (fr) * 1989-11-13 1991-05-15 Gichner Systems Group, Inc. Joint pour blindage contre des interférences électromagnétiques
US5205751A (en) * 1992-02-21 1993-04-27 Motorola, Inc. Electrically-conductive elastomeric connector

Also Published As

Publication number Publication date
AU4740197A (en) 1998-04-24

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