CA2231150A1 - Rf shield for circuit card - Google Patents
Rf shield for circuit card Download PDFInfo
- Publication number
- CA2231150A1 CA2231150A1 CA 2231150 CA2231150A CA2231150A1 CA 2231150 A1 CA2231150 A1 CA 2231150A1 CA 2231150 CA2231150 CA 2231150 CA 2231150 A CA2231150 A CA 2231150A CA 2231150 A1 CA2231150 A1 CA 2231150A1
- Authority
- CA
- Canada
- Prior art keywords
- casing
- fingers
- side walls
- periphery
- circuit card
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
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
- H05K9/002—Casings with localised screening
- H05K9/0022—Casings with localised screening of components mounted on printed circuit boards [PCB]
- H05K9/0024—Shield cases mounted on a PCB, e.g. cans or caps or conformal shields
- H05K9/003—Shield cases mounted on a PCB, e.g. cans or caps or conformal shields made from non-conductive materials comprising an electro-conductive coating
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
- Casings For Electric Apparatus (AREA)
Abstract
A metallized plastic RFI/EMI shield is provided against electromagnetic energy for a circuit card (32) wherein the shield is formed of a box enclosure with two casing halves to enclose the card (32), the first casing half having a solid flange side walls surrounding the card (32) and the second casing half (24) having a flange (26) formed by flat, plate-like closely-spaced fingers (28), the fingers confronting, being in electrical contact with and mating in full length with substantially the entire periphery of the side walls of the first casing half. The fingers (28) are preferably spaced with a separation of less than 1/4 wavelength of any measurable harmonic of the intended operating frequency, typically up to the tenth harmonic. A slot (18) may be provided to receive the fingers (28) on the outside of the side walls, and closely-spaced grounding pins arranged around the periphery of the card (32) may extend between the first and second casing halves through ground plated perforations (34) along the edge of the side walls.
Description
CA 022311~0 1998-03-04 W O 97/11592 PCTrUS96/14711 RF SHIELD FOR CIRCUIT CARD
BACKGROUND OF THE INv~NllON
This invention relates to electromagnetic shielding problems confronting radio frequency circuits. More particularly, the invention relates to a manufacturable shielding enclosure for circuit cards which emit unwanted electromagnetic radiation.
Shielding against unwanted high frequency r.f.
emissions is a challenge, since any seemingly small aperture in a shielding enclosure may inadvertently form a radiating aperture in the nature of a slot antenna structure. In the prior art, it has been necessary to provide several levels or layers of shielding to prevent unwanted emissions and to meet regulatory st~n~Ards for emission suppression. It has been observed that a major source of leakage is perimeter apertures in the shield. However, manufacturability is an important consideration in mass production applications. It is costly and impractical to test and customize each and every enclosure during assembly to assure emissions st~n~rds compliance.
What is needed is an enclosure which is readily manufactured, easily assembled with a circuit card and essentially fully immune to unwanted r.f. emissions.
SUMWARY OF THE lNV~NllON
According to the invention, a metallized plastic RFI/EMI shield is provided against ele~lu ~gnetic energy for a circuit card wherein the shield is formed of a box enclosure with two casing halves to enclose the card, the first casing half having a solid flange side walls ~ullounding the card and the second casing half having a flange formed by flat, plate-like closely-spaced fingers, the fingers confronting, being in electrical contact with and mating in full length with substantially the entire periphery of the side walls of the first casing half. The fingers are preferably spaced with a CA 022311~0 1998-03-04 W O 97/11592 PCT~US96/14711 separation of less than 1/4 wavelength of any measurable harmonic of the intended operating frequency, typically up to the tenth harmonic. A slot may be provided to receive the fingers on the outside of the side walls, and closely-spaced grounding pins arranged around the periphery of the card may extend between the first and second casing halves through ground plated perforations along the edge of the side walls.
The invention will be better understood upon reference to the following detailed description in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a first casing half of an enclosure.
Fig. 2 is a perspective view of a second casing half of an enclosure which mates with the first half casing to form an effective r.f. shield according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 is a perspective view of a first casing half 10 an enclosure according to the invention. Designated arbitrarily the upper half casing, this half 10 comprises a solid base 12 and a side wall 14 of a solid flange ext~n~;ng along the entire enclosure periphery. Optionally there may be a lip 16 outside the side wall 14 to define a slot 18 between the lip 16 and the side wall 14 all along the periphery of the base 12. AS understood, each circuitous path for an r.f.
signal increases path loss and thus adds to the effectiveness of ~u~lession. Within the interior, there are internal isolation walls 20, some of which are disposed along the side walls, and some of which traverse the base. As shown in this embodiment, the internal isolation walls have along their (inwardly-directed) edges regular, closely-spaced indentations 2 2 or holes. Alternatively, the indentations may be protrusions or pins which mate to such indentations 22. As hereinafter explained, these indentations and ~r oLL.lsions form another level of shielding and grounding for spurious emissions.
CA 022311~0 1998-03-04 Referring now to Fig. 2, there is a perspective view of a second casing half 24 of an r.f shield according to the invention. Together the casing halves 10 and 24 form an effective box enclosure r.f. shield according to the invention. The second casing half 24 mates intimately with the first casing half 10 to form the desired level of shielding. The structure of the second casing half 24 is instructive. According to the invention, there is provided a second flange 26 all along the periphery which is formed of closely-spaced fingers 28. The fingers 28 are generally flat, flexible plates wherein the inwardly-disposed surface conforms closely with the contour of the outer surface of the flange 16 of the mating first casing half 10. The fingers 28 and the flange 16 slidably contact one another when the two casing halves are mated. The fingers 28 extend into the optional slot 18 to establish the circuitous path for r.f.
The fingers 28 are closely spaced to one another, typically having narrow slots with side-to-side spacing of far less than a quarter wavelength. Preferably the spacing is less than 1/4 wavelength of the highest measurable harmonic of the operating frequency of the fundamental of the r.f.
emission. A typical spacing is 1/4 wavelength at the tenth harmonic (1/8 wavelength of the fifth harmonic). The narrow spacing has been found to be adequate to provide an effective r.f. seal to the edges which providing a good mech~n;cal slide fit. The plate-like ~ingers 28 produce a flexible, self-sustaining lateral pressure fit against the solid flange 14.
The material forming the shield may be metal or metallized plastic, that is, plastic coated or plated with copper and nickel. The copper provides electromagnetic shielding and the nickel provides abrasion resistance.
Various processes are known in the art to achieve a substantially uniform effective coating.
The enclosure is for enclosing a circuit card 32 (in phantom in Fig. 2) wherein the circuit card 32 conforms with the enclosure. In accordance with the invention, the second casing half 24 is provided with isolation walls 120 which align with the isolation walls 20 of the opposing half. In CA 022311~0 1998-03-04 W O 97/11592 PCT~US96/14711 this embodiment, closely-spaced protrusions 30 or pins are disposed along the inward faces of the walls 120 and which mate with indentations in the first casing half 10. The alternative is also equivalent. The protrusions 30, from whichever casing half, either extend directly through perforations 3 4 in the circuit card 32 or press along the periphery of the circuit card 32. The perforations 34 must be plated-through or the periphery must be edge plated to form a grounded boundary at and along the edge of the circuit card 32. The protrusions 30 provide a conductive path between the casing halves and the circuit card at the isolation walls 120 and 20 and along the inside of the flange 14. This structure further ~nh~nc~ internal as well as external r.f. shielding.
The invention has now been explained with reference to specific embodiments. Other embodiments will be apparent to those of ordinary skill in the art. It is therefore not in~n~e~ that this invention be limited except by the appended claims.
BACKGROUND OF THE INv~NllON
This invention relates to electromagnetic shielding problems confronting radio frequency circuits. More particularly, the invention relates to a manufacturable shielding enclosure for circuit cards which emit unwanted electromagnetic radiation.
Shielding against unwanted high frequency r.f.
emissions is a challenge, since any seemingly small aperture in a shielding enclosure may inadvertently form a radiating aperture in the nature of a slot antenna structure. In the prior art, it has been necessary to provide several levels or layers of shielding to prevent unwanted emissions and to meet regulatory st~n~Ards for emission suppression. It has been observed that a major source of leakage is perimeter apertures in the shield. However, manufacturability is an important consideration in mass production applications. It is costly and impractical to test and customize each and every enclosure during assembly to assure emissions st~n~rds compliance.
What is needed is an enclosure which is readily manufactured, easily assembled with a circuit card and essentially fully immune to unwanted r.f. emissions.
SUMWARY OF THE lNV~NllON
According to the invention, a metallized plastic RFI/EMI shield is provided against ele~lu ~gnetic energy for a circuit card wherein the shield is formed of a box enclosure with two casing halves to enclose the card, the first casing half having a solid flange side walls ~ullounding the card and the second casing half having a flange formed by flat, plate-like closely-spaced fingers, the fingers confronting, being in electrical contact with and mating in full length with substantially the entire periphery of the side walls of the first casing half. The fingers are preferably spaced with a CA 022311~0 1998-03-04 W O 97/11592 PCT~US96/14711 separation of less than 1/4 wavelength of any measurable harmonic of the intended operating frequency, typically up to the tenth harmonic. A slot may be provided to receive the fingers on the outside of the side walls, and closely-spaced grounding pins arranged around the periphery of the card may extend between the first and second casing halves through ground plated perforations along the edge of the side walls.
The invention will be better understood upon reference to the following detailed description in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a first casing half of an enclosure.
Fig. 2 is a perspective view of a second casing half of an enclosure which mates with the first half casing to form an effective r.f. shield according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 is a perspective view of a first casing half 10 an enclosure according to the invention. Designated arbitrarily the upper half casing, this half 10 comprises a solid base 12 and a side wall 14 of a solid flange ext~n~;ng along the entire enclosure periphery. Optionally there may be a lip 16 outside the side wall 14 to define a slot 18 between the lip 16 and the side wall 14 all along the periphery of the base 12. AS understood, each circuitous path for an r.f.
signal increases path loss and thus adds to the effectiveness of ~u~lession. Within the interior, there are internal isolation walls 20, some of which are disposed along the side walls, and some of which traverse the base. As shown in this embodiment, the internal isolation walls have along their (inwardly-directed) edges regular, closely-spaced indentations 2 2 or holes. Alternatively, the indentations may be protrusions or pins which mate to such indentations 22. As hereinafter explained, these indentations and ~r oLL.lsions form another level of shielding and grounding for spurious emissions.
CA 022311~0 1998-03-04 Referring now to Fig. 2, there is a perspective view of a second casing half 24 of an r.f shield according to the invention. Together the casing halves 10 and 24 form an effective box enclosure r.f. shield according to the invention. The second casing half 24 mates intimately with the first casing half 10 to form the desired level of shielding. The structure of the second casing half 24 is instructive. According to the invention, there is provided a second flange 26 all along the periphery which is formed of closely-spaced fingers 28. The fingers 28 are generally flat, flexible plates wherein the inwardly-disposed surface conforms closely with the contour of the outer surface of the flange 16 of the mating first casing half 10. The fingers 28 and the flange 16 slidably contact one another when the two casing halves are mated. The fingers 28 extend into the optional slot 18 to establish the circuitous path for r.f.
The fingers 28 are closely spaced to one another, typically having narrow slots with side-to-side spacing of far less than a quarter wavelength. Preferably the spacing is less than 1/4 wavelength of the highest measurable harmonic of the operating frequency of the fundamental of the r.f.
emission. A typical spacing is 1/4 wavelength at the tenth harmonic (1/8 wavelength of the fifth harmonic). The narrow spacing has been found to be adequate to provide an effective r.f. seal to the edges which providing a good mech~n;cal slide fit. The plate-like ~ingers 28 produce a flexible, self-sustaining lateral pressure fit against the solid flange 14.
The material forming the shield may be metal or metallized plastic, that is, plastic coated or plated with copper and nickel. The copper provides electromagnetic shielding and the nickel provides abrasion resistance.
Various processes are known in the art to achieve a substantially uniform effective coating.
The enclosure is for enclosing a circuit card 32 (in phantom in Fig. 2) wherein the circuit card 32 conforms with the enclosure. In accordance with the invention, the second casing half 24 is provided with isolation walls 120 which align with the isolation walls 20 of the opposing half. In CA 022311~0 1998-03-04 W O 97/11592 PCT~US96/14711 this embodiment, closely-spaced protrusions 30 or pins are disposed along the inward faces of the walls 120 and which mate with indentations in the first casing half 10. The alternative is also equivalent. The protrusions 30, from whichever casing half, either extend directly through perforations 3 4 in the circuit card 32 or press along the periphery of the circuit card 32. The perforations 34 must be plated-through or the periphery must be edge plated to form a grounded boundary at and along the edge of the circuit card 32. The protrusions 30 provide a conductive path between the casing halves and the circuit card at the isolation walls 120 and 20 and along the inside of the flange 14. This structure further ~nh~nc~ internal as well as external r.f. shielding.
The invention has now been explained with reference to specific embodiments. Other embodiments will be apparent to those of ordinary skill in the art. It is therefore not in~n~e~ that this invention be limited except by the appended claims.
Claims (11)
1. A shield against electromagnetic energy for an electromagnetic circuit card, said shield comprising:
a box enclosure for said electromagnetic circuit card, said box enclosure having a first casing and a second casing, said first casing having a solid first flange of a first contour defining side walls surrounding said electromagnetic circuit card and said second casing having a second flange of a second contour defining side walls, wherein said second contour is formed by closely-spaced fingers, said fingers confronting, being in electrical contact with and mating in full length with said first contour along substantially the entire periphery of said side walls.
a box enclosure for said electromagnetic circuit card, said box enclosure having a first casing and a second casing, said first casing having a solid first flange of a first contour defining side walls surrounding said electromagnetic circuit card and said second casing having a second flange of a second contour defining side walls, wherein said second contour is formed by closely-spaced fingers, said fingers confronting, being in electrical contact with and mating in full length with said first contour along substantially the entire periphery of said side walls.
2. The shield according to claim 1 wherein said fingers are spaced from one another at a distance substantially less than 1/4 wavelength of a measurable harmonic of a fundamental operating frequency of said electromagnetic circuit.
3. The shield according to claim 1 wherein said fingers are flat plates having a face for flexibly confronting said first contour.
4. The shield according to claim 3 wherein said second casing is formed of metallized plastic, and wherein said fingers flexibly conform to said first contour.
5. The shield according to claim 1 wherein said side walls are disposed within boundaries defined by said fingers.
6. The shield according to claim 5 wherein said first casing further includes a lip disposed in parallel to said side walls to define a receiving slot for said fingers.
7. The shield according to claim 6 wherein said electromagnetic circuit card has a plated periphery and further including a plurality of closely-spaced pins mating to said periphery and protruding from said first casing into said second casing through said periphery.
8. The shield according to claim 6 wherein said electromagnetic circuit card has a periphery of grounded perforations and said first casing further includes a plurality of closely-spaced pins mating to said perforations and protruding from said first casing into said second casing through said periphery.
9. A shield against electromagnetic energy for an electromagnetic circuit card, said shield comprising:
a box enclosure for said electromagnetic circuit card, said box enclosure having a first casing and a second casing, said second casing being formed of metallized plastic, said first casing having a solid first flange of a first contour defining side walls surrounding said electromagnetic circuit card and said second casing having a second flange of a second contour defining side walls, wherein said second contour is formed by closely-spaced fingers, said fingers confronting, being in electrical contact with and mating in full length with said first contour along substantially the entire periphery of said side walls, wherein said fingers are flat plates having a face for flexibly confronting said first contour and are spaced from one another at a distance substantially less than 1/4 wavelength of a measurable harmonic of a fundamental operating frequency of said electromagnetic circuit
a box enclosure for said electromagnetic circuit card, said box enclosure having a first casing and a second casing, said second casing being formed of metallized plastic, said first casing having a solid first flange of a first contour defining side walls surrounding said electromagnetic circuit card and said second casing having a second flange of a second contour defining side walls, wherein said second contour is formed by closely-spaced fingers, said fingers confronting, being in electrical contact with and mating in full length with said first contour along substantially the entire periphery of said side walls, wherein said fingers are flat plates having a face for flexibly confronting said first contour and are spaced from one another at a distance substantially less than 1/4 wavelength of a measurable harmonic of a fundamental operating frequency of said electromagnetic circuit
10. The shield according to claim 9 wherein said first casing further includes a lip disposed in parallel to said side walls to define a receiving slot for said fingers.
11. The shield according to claim 10 wherein said electromagnetic circuit card has a plated periphery and further including a plurality of closely-spaced pins mating to said periphery and protruding from said first casing into said second casing through said periphery.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US419795P | 1995-09-22 | 1995-09-22 | |
| US08/569,403 US5774344A (en) | 1995-12-06 | 1995-12-06 | RF shield for circuit card having a solid first flange |
| US60/004,197 | 1995-12-06 | ||
| US08/569,403 | 1995-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2231150A1 true CA2231150A1 (en) | 1997-03-27 |
Family
ID=26672740
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2231150 Abandoned CA2231150A1 (en) | 1995-09-22 | 1996-09-11 | Rf shield for circuit card |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0852108A4 (en) |
| JP (1) | JPH11511595A (en) |
| CN (1) | CN1196870A (en) |
| CA (1) | CA2231150A1 (en) |
| MX (1) | MX9802266A (en) |
| WO (1) | WO1997011592A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3780096A4 (en) * | 2019-03-29 | 2022-01-19 | LG Electronics Inc. | Substrate structure and control method therefor |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE29914661U1 (en) * | 1999-08-13 | 1999-11-11 | Detewe-Deutsche Telephonwerke Ag & Co, 10997 Berlin | Shielding to prevent the passage of electromagnetic radiation |
| US6443768B1 (en) * | 2001-09-14 | 2002-09-03 | Molex Incorporated | Small form factor connector cage |
| CN101166412B (en) * | 2006-10-16 | 2011-11-30 | 英华达(上海)电子有限公司 | A manufacturing method for shielding cover and shielding cover manufactured based on this method |
| JP2009130181A (en) | 2007-11-26 | 2009-06-11 | Ｎｅｃディスプレイソリューションズ株式会社 | Electronic circuit board, and method and structure for shielding electronic circuit board |
| CN102122766A (en) * | 2010-12-24 | 2011-07-13 | 向荣集团有限公司 | Connector of tubular bus bar |
| KR20170019023A (en) * | 2015-08-10 | 2017-02-21 | 에스케이하이닉스 주식회사 | Semiconductor package including EMI shielding and manufacturing method for the same |
| CN206251571U (en) * | 2016-11-30 | 2017-06-13 | 广州视源电子科技股份有限公司 | Electrostatic shielding device |
| CN109392295A (en) * | 2017-08-03 | 2019-02-26 | 深圳市道通智能航空技术有限公司 | Electromagnetic armouring structure and electronic equipment with this electromagnetic armouring structure |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5354951A (en) * | 1993-03-15 | 1994-10-11 | Leader Tech, Inc. | Circuit board component shielding enclosure and assembly |
-
1996
- 1996-09-11 EP EP96931560A patent/EP0852108A4/en not_active Withdrawn
- 1996-09-11 CA CA 2231150 patent/CA2231150A1/en not_active Abandoned
- 1996-09-11 JP JP9512792A patent/JPH11511595A/en active Pending
- 1996-09-11 WO PCT/US1996/014711 patent/WO1997011592A1/en not_active Application Discontinuation
- 1996-09-11 CN CN 96197100 patent/CN1196870A/en active Pending
-
1998
- 1998-03-23 MX MX9802266A patent/MX9802266A/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3780096A4 (en) * | 2019-03-29 | 2022-01-19 | LG Electronics Inc. | Substrate structure and control method therefor |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0852108A1 (en) | 1998-07-08 |
| MX9802266A (en) | 1998-11-29 |
| CN1196870A (en) | 1998-10-21 |
| WO1997011592A1 (en) | 1997-03-27 |
| EP0852108A4 (en) | 1999-05-26 |
| JPH11511595A (en) | 1999-10-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5774344A (en) | RF shield for circuit card having a solid first flange | |
| US4567317A (en) | EMI/RFI Protected enclosure | |
| US5165055A (en) | Method and apparatus for a PCB and I/O integrated electromagnetic containment | |
| US6624432B1 (en) | EMI containment apparatus | |
| US5724234A (en) | Slotted shield can | |
| EP1895826B1 (en) | Electronic Appliance with a metallic heat dissipating member | |
| EP0663142B1 (en) | Electromagnetic radiation reduction technique using grounded conductive traces circumscribing internal planes of printed circuit boards | |
| US6683245B1 (en) | Electromagnetic shield | |
| EP0608418A4 (en) | Cartridge for electronic apparatus. | |
| US20040043659A1 (en) | Electrical connector having improved shielding member and method of making the same | |
| EP0843512A3 (en) | High frequency emi shield with air flow for electronic device enclosure | |
| US6320122B1 (en) | Electromagnetic interference gasket | |
| CA2231150A1 (en) | Rf shield for circuit card | |
| US5610368A (en) | Clip plate bulkhead mounting for EMI filters | |
| US5170321A (en) | Enclosure system for environmental isolation of RF circuitry | |
| EP0342971B1 (en) | Electric device | |
| US5682299A (en) | PCMCIA module having multiple point grounding | |
| GB2420911A (en) | RF shielding liner having protrusions | |
| US6437993B1 (en) | Shielded housing for electronic circuit or components | |
| JPH08204377A (en) | Shielding body | |
| WO2002052916A1 (en) | Emi and rfi containment enclosure for electronic devices | |
| US7182644B2 (en) | Filtering electromagnetic interference from low frequency transmission lines at a device enclosure | |
| US4414425A (en) | Broadband non-contacting RF shielding gasket | |
| Dixon | EMI mitigation at millimeter wave | |
| US6700799B2 (en) | Electromagnetic interference containment apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |