CA2110639A1 - Emi internal shield apparatus and methods - Google Patents
Emi internal shield apparatus and methodsInfo
- Publication number
- CA2110639A1 CA2110639A1 CA 2110639 CA2110639A CA2110639A1 CA 2110639 A1 CA2110639 A1 CA 2110639A1 CA 2110639 CA2110639 CA 2110639 CA 2110639 A CA2110639 A CA 2110639A CA 2110639 A1 CA2110639 A1 CA 2110639A1
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- CA
- Canada
- Prior art keywords
- emi
- electrically conductive
- printed circuit
- circuit board
- electronic circuitry
- 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
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- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
Abstract
EMI SHIELD APPARATUS AND METHODS
ABSTRACT OF THE DISCLOSURE
A top cover and bottom cover made of an electrically conductive material that absorbs and reflects electromagnetic interference (EMI) signals are formed to fit without solder or welding as an EMI shield apparatus over EMI susceptible electronic circuitry on a printed circuit board. The EMI shield apparatus shields the circuitry from EMI while at the same time permitting the communication of desired electromagnetic radio frequency and electrical signals to the circuitry. The EMI shield apparatus includes the use of an electrically conductive layer that is integral to the top and bottom sides of the printed circuit board and which includes conductive channels that penetrate the printed circuit board. The channels prevent EMI from passing through the printed circuit board to the electronic circuitry. Also, the channels receive tangs found both on the top cover and bottom cover. The tangs are positioned to prevent EMI
from passing through the top and bottom cover junctures with the conductive layer. As EMI signals reach the shield apparatus, they are absorbed and conducted through the shield EMI apparatus to an electrical ground or reflected from the EMI shield. Openings on the top cover permit desired electromagnetic radio frequency signals to reach the electronic circuitry. Passageways through the conductive layer permit electrical leads from the electronic circuitry to connect to external circuitry.
ABSTRACT OF THE DISCLOSURE
A top cover and bottom cover made of an electrically conductive material that absorbs and reflects electromagnetic interference (EMI) signals are formed to fit without solder or welding as an EMI shield apparatus over EMI susceptible electronic circuitry on a printed circuit board. The EMI shield apparatus shields the circuitry from EMI while at the same time permitting the communication of desired electromagnetic radio frequency and electrical signals to the circuitry. The EMI shield apparatus includes the use of an electrically conductive layer that is integral to the top and bottom sides of the printed circuit board and which includes conductive channels that penetrate the printed circuit board. The channels prevent EMI from passing through the printed circuit board to the electronic circuitry. Also, the channels receive tangs found both on the top cover and bottom cover. The tangs are positioned to prevent EMI
from passing through the top and bottom cover junctures with the conductive layer. As EMI signals reach the shield apparatus, they are absorbed and conducted through the shield EMI apparatus to an electrical ground or reflected from the EMI shield. Openings on the top cover permit desired electromagnetic radio frequency signals to reach the electronic circuitry. Passageways through the conductive layer permit electrical leads from the electronic circuitry to connect to external circuitry.
Description
ENI SHIELD APPARATUS AND METHODS
TECHNICAL FIELD OF THE_INVENTION :
The present invention is related generally to ~ ~-electronics, and ~ore specifically to packaging of electronics to limit the co~munication o~ E~
(electromagnetic interference) signals. Even more specifically, the invention is related to packaging -electronic circuitry on a printed circuit board within an .
EMI shield while permitting desired electromagnetic radio ~requency and electrical signals to communicate with the -electronic circuitry. ~ ~
~ ': ' ' 92ADo05 PATENT APPLICATION
- 21 ~ ~3g3~
BACKGROUND OF THE INVENTION
The prior art packaging of printed circuit boards containing electronic circuitry to prevent EMI signals from leaving the package or from reaching and adversely affecting highly-susceptible electronic circuitry within the package is both la~or intensi~e to manufacture and service and suffers from several functional lLmitations.
Keeping EMI from leaving an electronics module that contains EMI-emitting components has required soldering certain shielding materials to the printed circuit board and fastening other shielding materials to the soldered shielding material using various screws or other fastening hardware. Reeping EMI from reaching and affecting susceptible electronic circuits in an electronics module, on the other hand, has required placing the printed circuit board fully in a sealed box made of a material that the effectively shields most of the EMI signals.
In typical packages that shield EMI emitting components, several pieces are soldered to the printed circuit board and as many as 20 or more pieces of fastening hardware affix to the soldered pieces to provide the necessary level of shielding. This labor-intensive practice of soldering and fastening prior art shielding enclosures to printed circuit boards increases ~ -the electronics module fabrication costs. Moreover, with prior art shielding enclosures it is not possible to easily replace or repair electronic circuitry components on the printed circuit board. This is due to circuitry components often being tightly positioned adjacent the soldered shield pieces that are not easily removable from the printed circuit board. This causes servicing EMI-shielded printed circuit boards also to be time-consuming and expensive.
Prior art packaging for preventing EMI signals from reaching and affect~ng EMI susceptible circuits in an ~ - 92AD005 PATENT APPLICATION
211~3~
Qlectronics module suffers from other limitations. Using soldered and fastened shield materials is generally impractical because an unacceptable level o~ EMI leakage often occ~rs in such designs. Therefore, prior art devices ~or shielding susceptible electronic cixcuits from EMI use sealed boxes made of aluminum or some other electrically conductive material that fully enclose the printed circuit board. The ENI shield boxes of the prior art have sealed edges that keep EMI away from the sensitive electronic circuitry while often providing a ~-way for radio frequency signals to reach the electronic circuits. These types of sealed EMI shield boxes, however, are cumbersome, expensive, labor intensive and require significant amounts of storage space in electronics cabinets designed to hold them.
An even more serious limitation that the prior art EMI shield boxes impose relates to the fact that numerous electronics cabinet designs call for easy installation and removal of the shielded electronics module. Some - ~ -newer electronics cabinet designs require that the printed cixcuit boards be directly plugged into the electronics cabinets. This requires exposing a large portion o~ the printed circuit board outside the EMI
shield. With the prior art EMI shield boxes, however, exposing the printed circuit board makes it possible for EMI to pass through the printed circuit board and to the susceptible electronic circuitry.
It is thus an object of the present invention to provide a shielding apparatus for electronic circuitry on a printed circuit board that allows solderless installation of an EMI shield to produce an electronics module that has a high degree of EMI shielding and that permits extensive communication of desired electromagnetic radio frequency and electrical signals by exposing from out o~ the ENI shield certain portions of the printed circuit board.
~ 92AD005 PATENT APPLICATION
~ila63~
BRIEF ~E$CRIPTION OF T~E_DRAWINGS
Other objects and advantages of the present invention will ~e apparent from a reading of the specification and appended claims in conjunction with the drawings, wherein:
FIGURE 1 shows a card cage of a communications electronics cabinet that may establish a typical physical and E~I environment for the present invention;
FIGURE 2 shows an exploded view of the preferred embodiment of the present invention;
FIG~RE 3 shows a more detailed, exploded partial view of the preferred embodiment for more particularly illustrating the cooperation among its various components;
FIGURE 4 shows a ~iew of the top cover to illustrate the design of shield grounding tangs and trace signal passageways of the preferred embodiment;
FIGURE S shows a side cut-away view of a portion of the bottom cover of ~he preferred embodiment; and :.
FIGURE 6 is an exploded view of the top cover of the preferred embodiment that illustrates the placement and design of an internal shield of the preferred embodiment.
211~3~
-~ETAILED DESCRIPTION OF THE INVENTION
In FIGURE 1 appears a typical environment for employing the preferred embodiment of the present invention. Electronics module 10 may, ~or example, be a communications receiver module that fits within card cage 12 of communications electronics cabinet 14. Electronics cabinet 14 may contain a plurality of such communicatio~s electronics module~ 10 plugged side-by-side in slots such as slot 16. Communications electronics cabinet 14 receives each of the electronics modules 10 and electrically connects circuitry inside each electronic module 10 to other components of communications electronics cabinet 14. Communications electronics modules 10 may taXe a low level signal from a remote ;~
transmitter and amplify the signal, separate an information portion of the signal from a carrier portion, and add information to the signal. It is very important that EMI not adversely affect these operations.
Therefore, the embodiment of the present invention provides this necessary EMI shielding.
FIGURE 2 shows the preferred embodiment of the printed circuit board shielding method and apparatus 20 of the present invention that together with associated electronic circuitry forms electronics module 10 of FIGURE 1. Referring to FIGURE 2, printed circuit board 22 includes top side 24 and bottom side 26 ~or connecting and holding electronic circuitry (not shown). Electrical leads or traces 28 and 30 may connect printed circuit board 22 to associated receptacles o~ the communications electronics cabinet 14 of FIGURE 1. Additionally, printed circuit board 22 includes electrically conductive layer or perimeter 32 designed to surround electronic circuitry installed on top side 24. The shield apparatue 20 o~ the preferred embodiment includes top portion 34 having integral to it top shield 36 and side shields 38, 40, 42 and 44. Side shield 40 permits connecting various 92AD005 PATEN'r APPLIC~TION
coaxial cable connectors as well as displaying lnternal display lights, test points or other indications on the electronic circuitry through openings such as opening 41.
Additionally, openings such as opening 43 permit coaxial cable connectors or other connectors to pass through top cover 34 for electrical connection to the internal electronic circuitry. Internal shield 46 may attach to the internal side of top cover 34.
On bottom side 26 of printed circuit board 22 attaches bottom cov~r 48. Bottom cover 48 includes insulating material 50 to electrically separate the ~
electronic circuitry that may protrude from bottom side :
26 to the shield material of bottom cover 48. Insulating material 50, however, may not be necessary if bottom cover 48 is sufficiently tall to prohibit contact with circuitry that may pass ~hrough the bottom of printed circuit board 22. Several screws such as screw 52 pass through associated holes 54 of bottom cover 48 and holes 56 of printed circuit board 22 to screw bloc~s 58. -Blocks 58 mount to top cover 34 through mounting holes 60. The preferred e~bodiment may also include handle 61 to permit the removal of electronics module 10 from card cage 12 of communications electronics cabinet 14 of FIGURE 1, for example.
As FIGURE 2 illustrates, the preferred embodiment provides top cover 34 and bottom cover 48 that grip between them printed circuit board 22. Top cover 34 is made of aluminum in the preferred embodiment, however, other electrically conductive materials capable of effectively shielding EMI such as copper or steel may also be used. Although the pre~erred embodiment uses a single integral top cover 34, top cover 34 may be made with a single piece top shield 36 and side shields 38, 40, 42, and 44 made of one, two, three or four separate sides. These pieces may then connect togethor with top shield 36 to fit as a unit over printed circuit board 22.
92~D005 2 1 10 ~ 3 9 PATENT APPLIC~TION
-For example, side shields 38, 42, and 44 may ~e ~ormed o~
a single C-shaped strip of conductive material with side 40 and top shield 36 as separate pieces of shielding. If the top shield 36 of top cover 34 is a separate piece, a ~oil gasket bac~ed with a silicone material may be necessary to assure a good electrical co~nection between top shield 36 and the side shields 3~, 40, 42 and 44.
80ttom cover 48 typically is made of the same material as top cover 34, but other materials capable o~
shielding EMI may also be used. Insulating material 50 typically is a sheet of plastic or other material that adheres to bottom cover 98. Fastening means other than screws 52 to blocks 58 may also be used. For example, rivets or a press fitting may be used to gxip printed circuit board 22 between top cover 34 and bottom cover 48.
FIGURE 3 provides a more detailed view of shield apparatus 20 of FIGURE 2 to illustrate more precisely the mechanical cooperation of the EMI shield components of the preferred embodiment. Referring to FIG~RE 3, bottom cover 48 has vertical side~ 62 and 63 that include tangs such as tangs 64. ~angs 64 fit into certain of conductive paths or channels 66 of perimeter 32. The height o~ sides 62 and 63 is su~ficient to permit recessing screws 52 within holes 54 of bottom cover 48 so that when screwed down, the heads of screws 52 are flush with the outer sur~ace of bac~ cover 48. The height of hole S4 also minimizes distortion of sides 62 and 63 that may occur when screw 52 is screwed down.
Vertical sides 38 and 44 o~ top cover 34 also appear in FIGURE 3. On vertical sides 38 and 44 are tangs such as tang 68 that fit in the remaining channels 66 of printed circuit board 22. It should be noted that perimeter 34 o~ printed circuit board 22 appears as a -conductive metal layer on both top side 24 and bottom side 26 of printed circuit board 22. Channels 66 ,~'' :~
-,: :
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penetrate fully through printed circuit board 22 for receiving either tangs 64 from bottom cover 48 or tangs 68 from top cover 34. Channels 66 have an internal conductive layer that electrically connec~s to perimeter S 32. Perimeter 32 connects to ground lead 70. Ground lead 70 provides a way to electrically connect perimeter :
32 and channels 66 to an electrical ground.
As FIGUREs 2 and 3 illustrate, the preferred embodiment provides an EMI-shielded enclosure that is simple to place over and remove from the electronic circuitry of printed circuit board 22. In particular, no welding or soldering of side shields 38, 40 42, and 44, is necessary with the preferred em~odiment. Moreover, channels 66 and screw holes 56 form an EMI barriar that prevents EMI from passing through the edge of printed circuit board 22 and into the interior of the EMI shield enclosure that top cover 34 and ~ottom cover 48 establish.
Screw holes 56 and channels 66 are spaced not more than approximately one-half inch from each other in the preferred embodiment. The one-half inch distance is a function of the frequency of the ENI for which the components inside the EMI shield are most susceptible.
Additionally, the distance between tangs 62 of bottom cover 48 and tangs 68 of top cover 32 do not exceed one-inch in the preferred embodime~t ~or the same reason. To ..
accomplish this, tangs 62 generally alternate their engaging channels 66 with the tangs 68 engaging the remaining channels 66. It also warrants pointing out that openings 41 and 43 on side shield 40 (see FIGURE 2) do not make an opening greater than one-inch in any direction.
If the frequency of EMI for which electronics circuitry of electronics module 10 is susceptible is higher than the 70 MHz EMI signal for which EMI shield ;
apparatus 20 is designed, then it may be necessary to :':' ,, ",' :. i. , ,' ' ' ', ...
TECHNICAL FIELD OF THE_INVENTION :
The present invention is related generally to ~ ~-electronics, and ~ore specifically to packaging of electronics to limit the co~munication o~ E~
(electromagnetic interference) signals. Even more specifically, the invention is related to packaging -electronic circuitry on a printed circuit board within an .
EMI shield while permitting desired electromagnetic radio ~requency and electrical signals to communicate with the -electronic circuitry. ~ ~
~ ': ' ' 92ADo05 PATENT APPLICATION
- 21 ~ ~3g3~
BACKGROUND OF THE INVENTION
The prior art packaging of printed circuit boards containing electronic circuitry to prevent EMI signals from leaving the package or from reaching and adversely affecting highly-susceptible electronic circuitry within the package is both la~or intensi~e to manufacture and service and suffers from several functional lLmitations.
Keeping EMI from leaving an electronics module that contains EMI-emitting components has required soldering certain shielding materials to the printed circuit board and fastening other shielding materials to the soldered shielding material using various screws or other fastening hardware. Reeping EMI from reaching and affecting susceptible electronic circuits in an electronics module, on the other hand, has required placing the printed circuit board fully in a sealed box made of a material that the effectively shields most of the EMI signals.
In typical packages that shield EMI emitting components, several pieces are soldered to the printed circuit board and as many as 20 or more pieces of fastening hardware affix to the soldered pieces to provide the necessary level of shielding. This labor-intensive practice of soldering and fastening prior art shielding enclosures to printed circuit boards increases ~ -the electronics module fabrication costs. Moreover, with prior art shielding enclosures it is not possible to easily replace or repair electronic circuitry components on the printed circuit board. This is due to circuitry components often being tightly positioned adjacent the soldered shield pieces that are not easily removable from the printed circuit board. This causes servicing EMI-shielded printed circuit boards also to be time-consuming and expensive.
Prior art packaging for preventing EMI signals from reaching and affect~ng EMI susceptible circuits in an ~ - 92AD005 PATENT APPLICATION
211~3~
Qlectronics module suffers from other limitations. Using soldered and fastened shield materials is generally impractical because an unacceptable level o~ EMI leakage often occ~rs in such designs. Therefore, prior art devices ~or shielding susceptible electronic cixcuits from EMI use sealed boxes made of aluminum or some other electrically conductive material that fully enclose the printed circuit board. The ENI shield boxes of the prior art have sealed edges that keep EMI away from the sensitive electronic circuitry while often providing a ~-way for radio frequency signals to reach the electronic circuits. These types of sealed EMI shield boxes, however, are cumbersome, expensive, labor intensive and require significant amounts of storage space in electronics cabinets designed to hold them.
An even more serious limitation that the prior art EMI shield boxes impose relates to the fact that numerous electronics cabinet designs call for easy installation and removal of the shielded electronics module. Some - ~ -newer electronics cabinet designs require that the printed cixcuit boards be directly plugged into the electronics cabinets. This requires exposing a large portion o~ the printed circuit board outside the EMI
shield. With the prior art EMI shield boxes, however, exposing the printed circuit board makes it possible for EMI to pass through the printed circuit board and to the susceptible electronic circuitry.
It is thus an object of the present invention to provide a shielding apparatus for electronic circuitry on a printed circuit board that allows solderless installation of an EMI shield to produce an electronics module that has a high degree of EMI shielding and that permits extensive communication of desired electromagnetic radio frequency and electrical signals by exposing from out o~ the ENI shield certain portions of the printed circuit board.
~ 92AD005 PATENT APPLICATION
~ila63~
BRIEF ~E$CRIPTION OF T~E_DRAWINGS
Other objects and advantages of the present invention will ~e apparent from a reading of the specification and appended claims in conjunction with the drawings, wherein:
FIGURE 1 shows a card cage of a communications electronics cabinet that may establish a typical physical and E~I environment for the present invention;
FIGURE 2 shows an exploded view of the preferred embodiment of the present invention;
FIG~RE 3 shows a more detailed, exploded partial view of the preferred embodiment for more particularly illustrating the cooperation among its various components;
FIGURE 4 shows a ~iew of the top cover to illustrate the design of shield grounding tangs and trace signal passageways of the preferred embodiment;
FIGURE S shows a side cut-away view of a portion of the bottom cover of ~he preferred embodiment; and :.
FIGURE 6 is an exploded view of the top cover of the preferred embodiment that illustrates the placement and design of an internal shield of the preferred embodiment.
211~3~
-~ETAILED DESCRIPTION OF THE INVENTION
In FIGURE 1 appears a typical environment for employing the preferred embodiment of the present invention. Electronics module 10 may, ~or example, be a communications receiver module that fits within card cage 12 of communications electronics cabinet 14. Electronics cabinet 14 may contain a plurality of such communicatio~s electronics module~ 10 plugged side-by-side in slots such as slot 16. Communications electronics cabinet 14 receives each of the electronics modules 10 and electrically connects circuitry inside each electronic module 10 to other components of communications electronics cabinet 14. Communications electronics modules 10 may taXe a low level signal from a remote ;~
transmitter and amplify the signal, separate an information portion of the signal from a carrier portion, and add information to the signal. It is very important that EMI not adversely affect these operations.
Therefore, the embodiment of the present invention provides this necessary EMI shielding.
FIGURE 2 shows the preferred embodiment of the printed circuit board shielding method and apparatus 20 of the present invention that together with associated electronic circuitry forms electronics module 10 of FIGURE 1. Referring to FIGURE 2, printed circuit board 22 includes top side 24 and bottom side 26 ~or connecting and holding electronic circuitry (not shown). Electrical leads or traces 28 and 30 may connect printed circuit board 22 to associated receptacles o~ the communications electronics cabinet 14 of FIGURE 1. Additionally, printed circuit board 22 includes electrically conductive layer or perimeter 32 designed to surround electronic circuitry installed on top side 24. The shield apparatue 20 o~ the preferred embodiment includes top portion 34 having integral to it top shield 36 and side shields 38, 40, 42 and 44. Side shield 40 permits connecting various 92AD005 PATEN'r APPLIC~TION
coaxial cable connectors as well as displaying lnternal display lights, test points or other indications on the electronic circuitry through openings such as opening 41.
Additionally, openings such as opening 43 permit coaxial cable connectors or other connectors to pass through top cover 34 for electrical connection to the internal electronic circuitry. Internal shield 46 may attach to the internal side of top cover 34.
On bottom side 26 of printed circuit board 22 attaches bottom cov~r 48. Bottom cover 48 includes insulating material 50 to electrically separate the ~
electronic circuitry that may protrude from bottom side :
26 to the shield material of bottom cover 48. Insulating material 50, however, may not be necessary if bottom cover 48 is sufficiently tall to prohibit contact with circuitry that may pass ~hrough the bottom of printed circuit board 22. Several screws such as screw 52 pass through associated holes 54 of bottom cover 48 and holes 56 of printed circuit board 22 to screw bloc~s 58. -Blocks 58 mount to top cover 34 through mounting holes 60. The preferred e~bodiment may also include handle 61 to permit the removal of electronics module 10 from card cage 12 of communications electronics cabinet 14 of FIGURE 1, for example.
As FIGURE 2 illustrates, the preferred embodiment provides top cover 34 and bottom cover 48 that grip between them printed circuit board 22. Top cover 34 is made of aluminum in the preferred embodiment, however, other electrically conductive materials capable of effectively shielding EMI such as copper or steel may also be used. Although the pre~erred embodiment uses a single integral top cover 34, top cover 34 may be made with a single piece top shield 36 and side shields 38, 40, 42, and 44 made of one, two, three or four separate sides. These pieces may then connect togethor with top shield 36 to fit as a unit over printed circuit board 22.
92~D005 2 1 10 ~ 3 9 PATENT APPLIC~TION
-For example, side shields 38, 42, and 44 may ~e ~ormed o~
a single C-shaped strip of conductive material with side 40 and top shield 36 as separate pieces of shielding. If the top shield 36 of top cover 34 is a separate piece, a ~oil gasket bac~ed with a silicone material may be necessary to assure a good electrical co~nection between top shield 36 and the side shields 3~, 40, 42 and 44.
80ttom cover 48 typically is made of the same material as top cover 34, but other materials capable o~
shielding EMI may also be used. Insulating material 50 typically is a sheet of plastic or other material that adheres to bottom cover 98. Fastening means other than screws 52 to blocks 58 may also be used. For example, rivets or a press fitting may be used to gxip printed circuit board 22 between top cover 34 and bottom cover 48.
FIGURE 3 provides a more detailed view of shield apparatus 20 of FIGURE 2 to illustrate more precisely the mechanical cooperation of the EMI shield components of the preferred embodiment. Referring to FIG~RE 3, bottom cover 48 has vertical side~ 62 and 63 that include tangs such as tangs 64. ~angs 64 fit into certain of conductive paths or channels 66 of perimeter 32. The height o~ sides 62 and 63 is su~ficient to permit recessing screws 52 within holes 54 of bottom cover 48 so that when screwed down, the heads of screws 52 are flush with the outer sur~ace of bac~ cover 48. The height of hole S4 also minimizes distortion of sides 62 and 63 that may occur when screw 52 is screwed down.
Vertical sides 38 and 44 o~ top cover 34 also appear in FIGURE 3. On vertical sides 38 and 44 are tangs such as tang 68 that fit in the remaining channels 66 of printed circuit board 22. It should be noted that perimeter 34 o~ printed circuit board 22 appears as a -conductive metal layer on both top side 24 and bottom side 26 of printed circuit board 22. Channels 66 ,~'' :~
-,: :
211~3~
penetrate fully through printed circuit board 22 for receiving either tangs 64 from bottom cover 48 or tangs 68 from top cover 34. Channels 66 have an internal conductive layer that electrically connec~s to perimeter S 32. Perimeter 32 connects to ground lead 70. Ground lead 70 provides a way to electrically connect perimeter :
32 and channels 66 to an electrical ground.
As FIGUREs 2 and 3 illustrate, the preferred embodiment provides an EMI-shielded enclosure that is simple to place over and remove from the electronic circuitry of printed circuit board 22. In particular, no welding or soldering of side shields 38, 40 42, and 44, is necessary with the preferred em~odiment. Moreover, channels 66 and screw holes 56 form an EMI barriar that prevents EMI from passing through the edge of printed circuit board 22 and into the interior of the EMI shield enclosure that top cover 34 and ~ottom cover 48 establish.
Screw holes 56 and channels 66 are spaced not more than approximately one-half inch from each other in the preferred embodiment. The one-half inch distance is a function of the frequency of the ENI for which the components inside the EMI shield are most susceptible.
Additionally, the distance between tangs 62 of bottom cover 48 and tangs 68 of top cover 32 do not exceed one-inch in the preferred embodime~t ~or the same reason. To ..
accomplish this, tangs 62 generally alternate their engaging channels 66 with the tangs 68 engaging the remaining channels 66. It also warrants pointing out that openings 41 and 43 on side shield 40 (see FIGURE 2) do not make an opening greater than one-inch in any direction.
If the frequency of EMI for which electronics circuitry of electronics module 10 is susceptible is higher than the 70 MHz EMI signal for which EMI shield ;
apparatus 20 is designed, then it may be necessary to :':' ,, ",' :. i. , ,' ' ' ', ...
2 ~ 3 ~
reduce the distance between tangs 64 on bottom cover 48 and tangs 68 on top cover 34.
Another significant benefit of the preferred embodiment is that it makes possible straddling a component of the printed circuit board. For example, circllitry that is not susceptible to EMI may be placed outside the EMI enclosure. By connecting circuitry through the printed circuit board and not in contact with either channels 66 or screw holes 56 it is possible to electrically connect circuitry inside to circuitry outside the EMI shield.
It may be possible to establish an EMI enclosure without the use of channels 66 by having tangs 64 and 68 simply contact continuous perimeter 32. This, however, will not prohibit ENI from passing through printed circuit board 22, unless some form of conductive shield material other than the internal surfaces of channels 66 also penetrates printed circuit board 22 at the same spacing as channels 66.
Yet another advantage of the preferred embodIment exhibits is that it provides a significantly simpler assembly relative to prior art EMI enclosures. Not only does the preferred embodiment significantly redu~e the necessary hardware (e.g., the prior art soldered and fastened EMI enclosure requires between 12 and 18 pieces -o~ hardware such as screws for assembly, whereas the preferred embodiment requires between only 10 and 12 pieces of hardware), but also the preferred embodiment -substantially reduces the piece part count (~.g., the prior art soldered and fastened EMI enclosure requires six pieces for shielding whereas the preferred embodiment needs only three pieces (i.e., top cover 34, insulator 50, and bottom cover 48)).
Yet another significant benefit of the preferred embodiment is that it may be completely assembled from a downward orientation. In other words, assembly of the ,~. ~
` :
9 2AD0 0 S PATENT APPLIC~TION
2 ~ 10~39 preferred embodiment may occur by first placing top cover 34 with its internal side upward on a flat surface. The next step is to install printed circuit board 22 over top cover 32 to engage channels 66 with tangs 68. Next, if handle 61 is necessary, it may be placed on printed circuit ~oard 22. Bottom cover 48 is then placed over printed circuit board 22 and handle 61 to engage channels 66 with tangs 64. Finally, screws 52 are installed in holes 54 to pass through printed circuit board 22 and to lo blocks 58 to fasten top cover 34 and bottom cover 48 to printed circuit board 2Z.
FIGURE 4 provides a side view of a cut-away portion of vertical shield side 44 to show more particularly shield grounding tangs 68 and trace signal openings such as opening 72. Vertical sides 38, 40, and 42 also have positioning tangs 68, but not signal trace openings 72.
As FIGURE 4 shows, tangs 68 protrude from side 44 of top cover 34 to ensure electrical contact between top cover 34 and channels 66 of perimeter 32. Although the preferred embodiment uses rectangular tang tips such as tip 74, the tang tips 74 may be rectangular, square, oval or circular in cross-section depending on the particular ease of design of other parameters affecting their manu~acture. Similarly, tang angles such as angle 76 permit tang tips 74 to be sufficiently small relative to the diameter of channels 66. This permits a significant amount of free play in the positioning of tangs 68 as they engage channels 66. With this level of free play, tang angles 76 assure that upon fastening top cover 34 to printed circuit board 22 a good electrical contact occurs. This assures that top cover 34 is electrically grounded. For this purpose, tang angle 76 may provide a straight edge, as in the preferred embcdiment, or may form a ~uarter circle or c~rved edge, depending upon the applicable manufacturing limitations, if any.
- , . . . , . . ., ..... ..- ~ , . .; . . -: . . ~ ,. , ,: ..... ...: ,;-: . . - - - . :: ........... -:: : :- -. . : : - ... -: . ., -:- : . : .:. :- ,., :: -: , :- .. .- ... ,. ~ .... -` 92AD005 PATENT APPLICATION
An important consideration of the preferred embodiment, which has application as an EMI shield for a communications receiver module, is to admit traces into the receiving components of the electronic circuitry on printed circuit board 22. For example, electronics module 10 may contain circuitry that receives signals from traces that run to the outer edge of printed circuit board 22. For this purpose, side shield 44 o~ top co~er 34 provides different side shield heights among certain of the alternating spaces between tangs 68. As FIGURE 4 demonstrates, a di~ference ~ in height between trace signal opening 72 and opening 78 exists. The height difference ~ causes trace signal opening 72 to form a gap or opening equal to the difference ~ in height between shield side 44 and printed circuit board 22 when top cover 32 fastens to printed circuit board 22. For the preferred embodiment, this opening having height ~ has a width 80 of approximately one-inch due the spacing of tangs 68. This ~ap or opening area provides a :
sufficiently long slot line to permit power to reach the electronic circuitry of electronics module 10. The one~
inch separation, however, prevents undesirable EMI from passing through and affecting the ENI-susceptible electronic circuitry.
Maintaining the integrity of the EMI barrier at :~
junctures between top cover 34 and printed circuit board 22 top side 24 and bottom cover 48 and bottom side 26 is an essential characteristic of the preferred embodiment.
This may require modi~ication of either printed circuit board 22, top cover 34, or bottom cover 48 when component placement restricts the ability to use tangs 68 or 64.
For example, at the point where handle 61 (see FIGURE 2) ~: .
contacts bottom cover 48 it is not possible to easily use :
a positioning tang 64. FIG~RE 5 shows a cross-section of ; :~
.
92AD0 05 PATENT APPLIC~TION
211~g3~
a portion of hottom cover 48 to illustrate how the preferred embodiment overcomes this situation.
FIGURE 5 illustrates a hal~-shear 82 that may be used on bottom cover 48 to provide an EMI shield at the point where bottom cover 48 covers handle 61. ~y hal~
shearing bottom cover 48 to produce an indentation having a depth approximately one-half that of the thickness of the bottom cover 48 sheet metal, it is possible to maintain the integrity of the approximately one-inch EMI
barrier at all points around bottom cover 48.
FIGURE 6 illustrates an exploded isometric diagram of the internal shield 46 of the preferred embodiment.
In particular, internal shield 46 contacts top cover 34 on inside surface ~4. Internal shield 46 has side shield surfaces that form vertical shield 86 that may follow the contour of a conductive layer placed within and electrically connected to conductive perimeter 32 of the preferred embodiment. Such a conductive layer would surround a predetermined portion of the electronics circuitry on printed circuit board 22. The function of internal shield 46 is to isolate a circuit from within top cover 34. The embodiment that FIGURE 6 shows has ~ive straight surfaces that form vertical shield 86.
Integral and perpendicular to vertical shield 86 is horizontal mounting edge 88. Mounting edge 88 folds parallel to inside surface 84 ~or placement thereon. In '~
order to mount internal shield 46 to inside surface 84, the preferred embodiment coordinates the use of sel~-positioning tangs such as self-positioning tang 90 and pop rivets such as pop rivet 92.
Internal shield 46, like top cover 34 and bottom cover 48, includes tangs such as tang 94 to engage corresponding channels that may be placed within a conductive layer on printed circuit board 22. Also similar to top cover 34, internal shield 46 uses blocks such as block 96 that mount to mounting hole 98 to : ~ - .- : .:: , . . .
: . : , . ,, , ,.,. ::: :.~ .. ,: . .. .: .... -.
92A~005 PATENT APPLICATIOM
receive a fastening screw such as screw 52 of FIGURE 2.
As FIGURE 6 further illustrates, internal shield 46 also has spaces to establish trace signal opening such as edge 100 that, for example, differs in height from edge 102 by a distance sufficient to permit the communication of desired signal traces. The size of internal shield 46 depends on the desired electronic circuitry on printed circuit ~oard 22 for which internal shield 46 is necessary.
Positioning tangs 90 aid in self-positioning internal shield 46 on inside surface 84. Positioning tangs 90 extend beyond edge 104 of internal shield 46.
When internal shield 46 is placed in contact with inside surface 84, positioning tangs 90 drop into holes such as hole 91 to align internal shield 46 to its proper location. When intçrnal shield 46 is in position, pop rivets 92 pass through associated holes such as hole 103 of top cover 34 and hole 106 of mounting edge 88. Holes 103 may be slightly larger than the shaft of pop rivet to permit a slight degree o~ free play when fastening ~-internal shield 46 to top cover 34. Once in place, pop -rivets 92 may be forced or pressed to secure internal --shield 46 to top cover 34.
Positioning tangs 90 may be rectangular or square in shape depending on the particular manufacturing or design objectives or limitations. Other methods of fastening internal shield 46 to inside surface 84 may include screws, soldering, brazing, or press fitting or other methods of fastening. By fastening internal shield 46 to top cover 34, upon the removing top c~ver 34 all circuitry on printed circuit board 22 is immediately accessible for factory repair or replacement.
Internal shield 46 represents a significant improvement over prior art methods and apparatuses to isolate selected circuits on a printed board from other circuits within the EMI enclosure of the preferred ~119~3~
embodiment. In particular, internal ~hield 46 is a olderless way o~ separating specific circuits rrom other circuits in the enclosure. This has the advantage o~
making those circuits accessible and not restricted in accessibility by the soldered vertical shield to the prior art. Another technical advantage that internal shield 46 provides relates to the way that positioning tangs 90 cooperate with engaging tangs 94. By having self-positioning tangs 90 and engaging tangs 94 cn the same vextical shield 88, this enhances alignment o~
engaging tangs 94 with the associated grounding channels o~ printed circuit board 22.
~ 92AD005 P~TENT APP~ICATION
- 2i1fJ639 OPERATION
The basic operation of the preferred embodiment is very straight forward once conceived and comprises placing top cover 34 and bottom cover 48 so as to grip S and hold firm printed circuit board 22. As E~I reaches the electronics module 10 that results when placing the appropriate circuitry on printed circuit board 22, ~rom the top of the module top cover ~4 prevents EMI from reaching and affecting the electronic circuitry side shields 38, 40, 42, and 44 prevent EMI from reaching the electronic circuitry from the sides. Back cover 48 prevents EMI signals ~rom reaching the bottom portion of the circuitry positioned on printed circuit board 22.
Although EMI might otherwise pass through the ~uncture between top cover 34 and printed circuit board 22 and, similarly, bottom cover 48 and printed circuit board 22, positioning tangs 68 and 64, respectively, together with channels 66 prevent this from happening.
The EMI signals of concern ~or the preferred embodiment have a frequency o~ approximately 70 MHz.
This frequency yields a signal with an approximately 168-inch wavelength. A factor of 30 divides this wa~elength -to specify the maximum hole size for the EMI shield. ~he 30 ~actor limit the EMI shield apparatus 20 to a maximum -hole size o~ 5.6 inches. The preferred embodiment protects the electronic circuitry from the ~ifth harmonic o~ the EMI. This even further limits the EMI shield to only a 1.12 inch maximum hole size. Since the preferred embodiment has no opening greater than one-inch in size, strong levels of EMI do not reach the electronic circuitry that EMI shield apparatus 20 protects. In ~act, testing o~ the EMI shield of the preferred embodiment shows a 6 dB improvement over the prior art EMI shielding mechanisms designed to protect susceptible electronic circuit~.
:
92AD005 PATENT APPLIC~TION
, 2lla63s The operation o~ internal shield 46 of FIGUnE 6 provides similar EMI shield operation. Additionally, internal shield 46 isolates circuitry within internal shield 46 from other circuitry in electronics module 10.
The operation of the preferred embodiment may also extend to using the present invention to prevent EMI
transmission ~rom an electronics module. If EMI shield apparatus 20 were to enclose a communications transmitter module, it would prevent EMI from leavi~g EMI-generating circuitry. When used in this way, EMI shield apparatus 20 not only ser~es to shield susceptible electronic circuitry from EMI, but also may be used to prevent transmission of ENI to enhance electromagnetic compatibility within a communications electronics cabinet.
EMI shield apparatus 20 provides a high degree o~
electromagnetic compatibility (EMC~ among adjacent electron modules 10. As use herein, electromagnetic compatibility is the ability of electronic system to ~unction properly in its intended electromagnetic environment and not be a source o~ electromagnetic signal p~llution to that environment. This enhances the operation of other units within card cage 12 of FIGURE 1, ~or example. The preferred embodiment of the present invention achieves a high degree of EMC by significantly reducing the amount o~ EMI reaching susceptible components within the electronic circuitry of electronics module 20, while at the same time preventing the leakage of the EMI from components that operate within the shielded environment of the pre~erred embodiment.
In summary, we have illustrated one embodiment o~
the inventive concept o~ an EMI shield apparatus that encloses a printed circuit board and that permits easy, solderless installation while producing a highly ENI-shielded electronics module by placing around the susceptible circuitry an EMI shield layer that prohibits . - . ~ ~: : : :
92AD005 PATENT APPLIC~TION
211~3~ ~
EMI from passing through the edges of the circuitry and gripping the printed circuit board between an EMI shield ~ ; .
top coYer and an ENI shield bottom cover with specially designed tangs integral to the top and bottom covers to :
make connectioni to the EMI layer on the printed circuit board while permitting extensive communication of desired radio frequency and electrical signals with the enclosed :~
electronic circuitry. -:~
.~ . ., ~ : ' :: ~ `: .
.
~' ,' ' ' ;
`,:
reduce the distance between tangs 64 on bottom cover 48 and tangs 68 on top cover 34.
Another significant benefit of the preferred embodiment is that it makes possible straddling a component of the printed circuit board. For example, circllitry that is not susceptible to EMI may be placed outside the EMI enclosure. By connecting circuitry through the printed circuit board and not in contact with either channels 66 or screw holes 56 it is possible to electrically connect circuitry inside to circuitry outside the EMI shield.
It may be possible to establish an EMI enclosure without the use of channels 66 by having tangs 64 and 68 simply contact continuous perimeter 32. This, however, will not prohibit ENI from passing through printed circuit board 22, unless some form of conductive shield material other than the internal surfaces of channels 66 also penetrates printed circuit board 22 at the same spacing as channels 66.
Yet another advantage of the preferred embodIment exhibits is that it provides a significantly simpler assembly relative to prior art EMI enclosures. Not only does the preferred embodiment significantly redu~e the necessary hardware (e.g., the prior art soldered and fastened EMI enclosure requires between 12 and 18 pieces -o~ hardware such as screws for assembly, whereas the preferred embodiment requires between only 10 and 12 pieces of hardware), but also the preferred embodiment -substantially reduces the piece part count (~.g., the prior art soldered and fastened EMI enclosure requires six pieces for shielding whereas the preferred embodiment needs only three pieces (i.e., top cover 34, insulator 50, and bottom cover 48)).
Yet another significant benefit of the preferred embodiment is that it may be completely assembled from a downward orientation. In other words, assembly of the ,~. ~
` :
9 2AD0 0 S PATENT APPLIC~TION
2 ~ 10~39 preferred embodiment may occur by first placing top cover 34 with its internal side upward on a flat surface. The next step is to install printed circuit board 22 over top cover 32 to engage channels 66 with tangs 68. Next, if handle 61 is necessary, it may be placed on printed circuit ~oard 22. Bottom cover 48 is then placed over printed circuit board 22 and handle 61 to engage channels 66 with tangs 64. Finally, screws 52 are installed in holes 54 to pass through printed circuit board 22 and to lo blocks 58 to fasten top cover 34 and bottom cover 48 to printed circuit board 2Z.
FIGURE 4 provides a side view of a cut-away portion of vertical shield side 44 to show more particularly shield grounding tangs 68 and trace signal openings such as opening 72. Vertical sides 38, 40, and 42 also have positioning tangs 68, but not signal trace openings 72.
As FIGURE 4 shows, tangs 68 protrude from side 44 of top cover 34 to ensure electrical contact between top cover 34 and channels 66 of perimeter 32. Although the preferred embodiment uses rectangular tang tips such as tip 74, the tang tips 74 may be rectangular, square, oval or circular in cross-section depending on the particular ease of design of other parameters affecting their manu~acture. Similarly, tang angles such as angle 76 permit tang tips 74 to be sufficiently small relative to the diameter of channels 66. This permits a significant amount of free play in the positioning of tangs 68 as they engage channels 66. With this level of free play, tang angles 76 assure that upon fastening top cover 34 to printed circuit board 22 a good electrical contact occurs. This assures that top cover 34 is electrically grounded. For this purpose, tang angle 76 may provide a straight edge, as in the preferred embcdiment, or may form a ~uarter circle or c~rved edge, depending upon the applicable manufacturing limitations, if any.
- , . . . , . . ., ..... ..- ~ , . .; . . -: . . ~ ,. , ,: ..... ...: ,;-: . . - - - . :: ........... -:: : :- -. . : : - ... -: . ., -:- : . : .:. :- ,., :: -: , :- .. .- ... ,. ~ .... -` 92AD005 PATENT APPLICATION
An important consideration of the preferred embodiment, which has application as an EMI shield for a communications receiver module, is to admit traces into the receiving components of the electronic circuitry on printed circuit board 22. For example, electronics module 10 may contain circuitry that receives signals from traces that run to the outer edge of printed circuit board 22. For this purpose, side shield 44 o~ top co~er 34 provides different side shield heights among certain of the alternating spaces between tangs 68. As FIGURE 4 demonstrates, a di~ference ~ in height between trace signal opening 72 and opening 78 exists. The height difference ~ causes trace signal opening 72 to form a gap or opening equal to the difference ~ in height between shield side 44 and printed circuit board 22 when top cover 32 fastens to printed circuit board 22. For the preferred embodiment, this opening having height ~ has a width 80 of approximately one-inch due the spacing of tangs 68. This ~ap or opening area provides a :
sufficiently long slot line to permit power to reach the electronic circuitry of electronics module 10. The one~
inch separation, however, prevents undesirable EMI from passing through and affecting the ENI-susceptible electronic circuitry.
Maintaining the integrity of the EMI barrier at :~
junctures between top cover 34 and printed circuit board 22 top side 24 and bottom cover 48 and bottom side 26 is an essential characteristic of the preferred embodiment.
This may require modi~ication of either printed circuit board 22, top cover 34, or bottom cover 48 when component placement restricts the ability to use tangs 68 or 64.
For example, at the point where handle 61 (see FIGURE 2) ~: .
contacts bottom cover 48 it is not possible to easily use :
a positioning tang 64. FIG~RE 5 shows a cross-section of ; :~
.
92AD0 05 PATENT APPLIC~TION
211~g3~
a portion of hottom cover 48 to illustrate how the preferred embodiment overcomes this situation.
FIGURE 5 illustrates a hal~-shear 82 that may be used on bottom cover 48 to provide an EMI shield at the point where bottom cover 48 covers handle 61. ~y hal~
shearing bottom cover 48 to produce an indentation having a depth approximately one-half that of the thickness of the bottom cover 48 sheet metal, it is possible to maintain the integrity of the approximately one-inch EMI
barrier at all points around bottom cover 48.
FIGURE 6 illustrates an exploded isometric diagram of the internal shield 46 of the preferred embodiment.
In particular, internal shield 46 contacts top cover 34 on inside surface ~4. Internal shield 46 has side shield surfaces that form vertical shield 86 that may follow the contour of a conductive layer placed within and electrically connected to conductive perimeter 32 of the preferred embodiment. Such a conductive layer would surround a predetermined portion of the electronics circuitry on printed circuit board 22. The function of internal shield 46 is to isolate a circuit from within top cover 34. The embodiment that FIGURE 6 shows has ~ive straight surfaces that form vertical shield 86.
Integral and perpendicular to vertical shield 86 is horizontal mounting edge 88. Mounting edge 88 folds parallel to inside surface 84 ~or placement thereon. In '~
order to mount internal shield 46 to inside surface 84, the preferred embodiment coordinates the use of sel~-positioning tangs such as self-positioning tang 90 and pop rivets such as pop rivet 92.
Internal shield 46, like top cover 34 and bottom cover 48, includes tangs such as tang 94 to engage corresponding channels that may be placed within a conductive layer on printed circuit board 22. Also similar to top cover 34, internal shield 46 uses blocks such as block 96 that mount to mounting hole 98 to : ~ - .- : .:: , . . .
: . : , . ,, , ,.,. ::: :.~ .. ,: . .. .: .... -.
92A~005 PATENT APPLICATIOM
receive a fastening screw such as screw 52 of FIGURE 2.
As FIGURE 6 further illustrates, internal shield 46 also has spaces to establish trace signal opening such as edge 100 that, for example, differs in height from edge 102 by a distance sufficient to permit the communication of desired signal traces. The size of internal shield 46 depends on the desired electronic circuitry on printed circuit ~oard 22 for which internal shield 46 is necessary.
Positioning tangs 90 aid in self-positioning internal shield 46 on inside surface 84. Positioning tangs 90 extend beyond edge 104 of internal shield 46.
When internal shield 46 is placed in contact with inside surface 84, positioning tangs 90 drop into holes such as hole 91 to align internal shield 46 to its proper location. When intçrnal shield 46 is in position, pop rivets 92 pass through associated holes such as hole 103 of top cover 34 and hole 106 of mounting edge 88. Holes 103 may be slightly larger than the shaft of pop rivet to permit a slight degree o~ free play when fastening ~-internal shield 46 to top cover 34. Once in place, pop -rivets 92 may be forced or pressed to secure internal --shield 46 to top cover 34.
Positioning tangs 90 may be rectangular or square in shape depending on the particular manufacturing or design objectives or limitations. Other methods of fastening internal shield 46 to inside surface 84 may include screws, soldering, brazing, or press fitting or other methods of fastening. By fastening internal shield 46 to top cover 34, upon the removing top c~ver 34 all circuitry on printed circuit board 22 is immediately accessible for factory repair or replacement.
Internal shield 46 represents a significant improvement over prior art methods and apparatuses to isolate selected circuits on a printed board from other circuits within the EMI enclosure of the preferred ~119~3~
embodiment. In particular, internal ~hield 46 is a olderless way o~ separating specific circuits rrom other circuits in the enclosure. This has the advantage o~
making those circuits accessible and not restricted in accessibility by the soldered vertical shield to the prior art. Another technical advantage that internal shield 46 provides relates to the way that positioning tangs 90 cooperate with engaging tangs 94. By having self-positioning tangs 90 and engaging tangs 94 cn the same vextical shield 88, this enhances alignment o~
engaging tangs 94 with the associated grounding channels o~ printed circuit board 22.
~ 92AD005 P~TENT APP~ICATION
- 2i1fJ639 OPERATION
The basic operation of the preferred embodiment is very straight forward once conceived and comprises placing top cover 34 and bottom cover 48 so as to grip S and hold firm printed circuit board 22. As E~I reaches the electronics module 10 that results when placing the appropriate circuitry on printed circuit board 22, ~rom the top of the module top cover ~4 prevents EMI from reaching and affecting the electronic circuitry side shields 38, 40, 42, and 44 prevent EMI from reaching the electronic circuitry from the sides. Back cover 48 prevents EMI signals ~rom reaching the bottom portion of the circuitry positioned on printed circuit board 22.
Although EMI might otherwise pass through the ~uncture between top cover 34 and printed circuit board 22 and, similarly, bottom cover 48 and printed circuit board 22, positioning tangs 68 and 64, respectively, together with channels 66 prevent this from happening.
The EMI signals of concern ~or the preferred embodiment have a frequency o~ approximately 70 MHz.
This frequency yields a signal with an approximately 168-inch wavelength. A factor of 30 divides this wa~elength -to specify the maximum hole size for the EMI shield. ~he 30 ~actor limit the EMI shield apparatus 20 to a maximum -hole size o~ 5.6 inches. The preferred embodiment protects the electronic circuitry from the ~ifth harmonic o~ the EMI. This even further limits the EMI shield to only a 1.12 inch maximum hole size. Since the preferred embodiment has no opening greater than one-inch in size, strong levels of EMI do not reach the electronic circuitry that EMI shield apparatus 20 protects. In ~act, testing o~ the EMI shield of the preferred embodiment shows a 6 dB improvement over the prior art EMI shielding mechanisms designed to protect susceptible electronic circuit~.
:
92AD005 PATENT APPLIC~TION
, 2lla63s The operation o~ internal shield 46 of FIGUnE 6 provides similar EMI shield operation. Additionally, internal shield 46 isolates circuitry within internal shield 46 from other circuitry in electronics module 10.
The operation of the preferred embodiment may also extend to using the present invention to prevent EMI
transmission ~rom an electronics module. If EMI shield apparatus 20 were to enclose a communications transmitter module, it would prevent EMI from leavi~g EMI-generating circuitry. When used in this way, EMI shield apparatus 20 not only ser~es to shield susceptible electronic circuitry from EMI, but also may be used to prevent transmission of ENI to enhance electromagnetic compatibility within a communications electronics cabinet.
EMI shield apparatus 20 provides a high degree o~
electromagnetic compatibility (EMC~ among adjacent electron modules 10. As use herein, electromagnetic compatibility is the ability of electronic system to ~unction properly in its intended electromagnetic environment and not be a source o~ electromagnetic signal p~llution to that environment. This enhances the operation of other units within card cage 12 of FIGURE 1, ~or example. The preferred embodiment of the present invention achieves a high degree of EMC by significantly reducing the amount o~ EMI reaching susceptible components within the electronic circuitry of electronics module 20, while at the same time preventing the leakage of the EMI from components that operate within the shielded environment of the pre~erred embodiment.
In summary, we have illustrated one embodiment o~
the inventive concept o~ an EMI shield apparatus that encloses a printed circuit board and that permits easy, solderless installation while producing a highly ENI-shielded electronics module by placing around the susceptible circuitry an EMI shield layer that prohibits . - . ~ ~: : : :
92AD005 PATENT APPLIC~TION
211~3~ ~
EMI from passing through the edges of the circuitry and gripping the printed circuit board between an EMI shield ~ ; .
top coYer and an ENI shield bottom cover with specially designed tangs integral to the top and bottom covers to :
make connectioni to the EMI layer on the printed circuit board while permitting extensive communication of desired radio frequency and electrical signals with the enclosed :~
electronic circuitry. -:~
.~ . ., ~ : ' :: ~ `: .
.
~' ,' ' ' ;
`,:
Claims (6)
1. A method for isolating EMI from electronic circuitry on a printed circuit board while permitting exposure of electrical connections to the electronic circuitry, comprising the steps of:
placing an electrically conductive perimeter on the printed circuit board, said electrically conductive perimeter surrounding the electronic circuitry while permitting electrical connections to the electronic circuitry to pass under said perimeter to an edge of said printed circuit board, said electrically conductive perimeter further electrically connected to a ground potential;
isolating the printed circuit board and electronic circuitry from EMI with a top housing, said top housing covering a top portion of the electronic circuitry and comprising a plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said top housing to said electrically conductive perimeter, said top housing further comprising a predetermined set of apertures for permitting passage of electrical connectors to said electronic circuitry, said apertures having a diameter no greater than said predetermined distance;
isolating the electronic circuitry from EMI
with a bottom housing, said bottom housing covering a bottom portion of the printed circuit board and electronic circuitry and comprising a plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said bottom housing to said electrically conductive perimeter; and fastening said top housing and said bottom housing to the printed circuit board and in electrical contact with said electrically conductive perimeter to establish a grounded EMI shield enclosure for the electronic circuitry on the printed circuitry board.
placing an electrically conductive perimeter on the printed circuit board, said electrically conductive perimeter surrounding the electronic circuitry while permitting electrical connections to the electronic circuitry to pass under said perimeter to an edge of said printed circuit board, said electrically conductive perimeter further electrically connected to a ground potential;
isolating the printed circuit board and electronic circuitry from EMI with a top housing, said top housing covering a top portion of the electronic circuitry and comprising a plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said top housing to said electrically conductive perimeter, said top housing further comprising a predetermined set of apertures for permitting passage of electrical connectors to said electronic circuitry, said apertures having a diameter no greater than said predetermined distance;
isolating the electronic circuitry from EMI
with a bottom housing, said bottom housing covering a bottom portion of the printed circuit board and electronic circuitry and comprising a plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said bottom housing to said electrically conductive perimeter; and fastening said top housing and said bottom housing to the printed circuit board and in electrical contact with said electrically conductive perimeter to establish a grounded EMI shield enclosure for the electronic circuitry on the printed circuitry board.
2. A printed circuit board assembly for containing electronic circuitry and isolating EMI from the electronic circuitry, comprising:
a printed circuit board for holding the electronic circuitry and comprising a plurality of leads for permitting electrical connection to the electronic circuitry, said printed circuit board having a top side and a bottom side;
an electrically conductive perimeter comprising an electrically conductive layer integral to said printed circuit board and surrounding the electronic circuitry, said electrically conductive perimeter permitting electrical leads to the electronic circuitry to pass under and separate from said perimeter to an edge of said printed circuit board;
a top housing comprising a first electrically conductive shield material for covering and isolating said top side and the electronic circuitry from EMI, said top housing further comprising a predetermined set of apertures for permitting passage of electrical connectors to said electronic circuitry, said apertures having a diameter no greater than said predetermined distance;
a first plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said first shield material to said perimeter, a bottom housing comprising a second electrically conductive shield material for covering and isolating said bottom side and said electronic circuitry from EMI;
a second plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said second shield material to said perimeter;
fastening means for fastening said top housing and said bottom housing to said electrically conductive perimeter for establishing an EMI shield enclosure for the electronic circuitry while permitting exposure of said leads.
a printed circuit board for holding the electronic circuitry and comprising a plurality of leads for permitting electrical connection to the electronic circuitry, said printed circuit board having a top side and a bottom side;
an electrically conductive perimeter comprising an electrically conductive layer integral to said printed circuit board and surrounding the electronic circuitry, said electrically conductive perimeter permitting electrical leads to the electronic circuitry to pass under and separate from said perimeter to an edge of said printed circuit board;
a top housing comprising a first electrically conductive shield material for covering and isolating said top side and the electronic circuitry from EMI, said top housing further comprising a predetermined set of apertures for permitting passage of electrical connectors to said electronic circuitry, said apertures having a diameter no greater than said predetermined distance;
a first plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said first shield material to said perimeter, a bottom housing comprising a second electrically conductive shield material for covering and isolating said bottom side and said electronic circuitry from EMI;
a second plurality of tangs for engaging said electrically conductive perimeter to form a solderless electrical connection with said second shield material to said perimeter;
fastening means for fastening said top housing and said bottom housing to said electrically conductive perimeter for establishing an EMI shield enclosure for the electronic circuitry while permitting exposure of said leads.
3. An EMI shield enclosure for containing EMI
susceptible electronic circuitry that isolates the circuitry from EMI, comprising:
a printed circuit board for holding electronic circuitry and comprising electrical means for permitting electrical connection to the electronic circuitry, said printed circuit board having a top side and a bottom side;
first electrically conductive means integral to said top side and said bottom side of said printed circuit board, said first electrically conductive means surrounding the electronic circuitry and connected to an electrical ground;
second electrically conductive means for communicating electrical signals with the electronic circuitry, said second electrically conductive means separate from and passing through said first electrically conductive means channel means passing through said printed circuit board from said top side to said bottom side and having a third electrically conductive means electrically connected to said first electrically conductive means, said channel means associated with said first electrically conductive means to prevent EMI having a predetermined wavelength from passing through said printed circuit board to the electronic circuitry;
first shield means for covering and isolating said top side and the electronic circuitry from EMI, said first shield means comprising connecting means for establishing a solderless electrical connection with said first shield means to said first electrically conductive means, said first shield means comprising a predetermined set of apertures for permitting passage of trace signals and electrical connectors to the electronic circuitry, said apertures having a diameter no greater than said predetermined wavelength;
second shield means for covering and isolating said bottom side and the electronic circuitry from EMI, said second shield means comprising connecting means for establishing a solderless electrical connection to said second shield means to said first electrically conductive means, said second shield means further comprising insulating means for insulating the electronic circuitry from said second shield means;
fastening means for fastening said first shield means and said second shield means to said first electrically conductive means for establishing an EMI
shield enclosure for the electronic circuitry while permitting exposure of said second electrically conductive means to the electronic circuitry.
susceptible electronic circuitry that isolates the circuitry from EMI, comprising:
a printed circuit board for holding electronic circuitry and comprising electrical means for permitting electrical connection to the electronic circuitry, said printed circuit board having a top side and a bottom side;
first electrically conductive means integral to said top side and said bottom side of said printed circuit board, said first electrically conductive means surrounding the electronic circuitry and connected to an electrical ground;
second electrically conductive means for communicating electrical signals with the electronic circuitry, said second electrically conductive means separate from and passing through said first electrically conductive means channel means passing through said printed circuit board from said top side to said bottom side and having a third electrically conductive means electrically connected to said first electrically conductive means, said channel means associated with said first electrically conductive means to prevent EMI having a predetermined wavelength from passing through said printed circuit board to the electronic circuitry;
first shield means for covering and isolating said top side and the electronic circuitry from EMI, said first shield means comprising connecting means for establishing a solderless electrical connection with said first shield means to said first electrically conductive means, said first shield means comprising a predetermined set of apertures for permitting passage of trace signals and electrical connectors to the electronic circuitry, said apertures having a diameter no greater than said predetermined wavelength;
second shield means for covering and isolating said bottom side and the electronic circuitry from EMI, said second shield means comprising connecting means for establishing a solderless electrical connection to said second shield means to said first electrically conductive means, said second shield means further comprising insulating means for insulating the electronic circuitry from said second shield means;
fastening means for fastening said first shield means and said second shield means to said first electrically conductive means for establishing an EMI
shield enclosure for the electronic circuitry while permitting exposure of said second electrically conductive means to the electronic circuitry.
4. A method for enclosing a printed circuit board containing EMI susceptible electronic circuitry that isolates the circuitry from EMI while permitting electrical access to the electronic circuitry, comprising the steps of:
surrounding said electronic circuitry with a first electrically conductive means internal to the printed circuit board and connecting said first electrically conductive means to an electrical ground;
communicating electrical signals with the electronic circuitry using a second electrically conductive means, said second electrically conductive means electrically separate from and passing through said first electrically conductive means to the electronic circuitry;
associating a channel means with said first electrically conductive means to prevent EMI having a predetermined wavelength from passing through the printed circuit board to the electronic circuitry, said channel means passing through the printed circuit board and having an electrically conductive means;
electrically connecting said channel means to said first electrically conductive means;
covering and isolating a top aspect of the electronic circuitry from EMI using a first shield means;
electrically connecting said first shield means to said first electrically conductive means using a solderless connecting means;
covering and isolating a bottom aspect of the electronic circuitry from EMI using a second shield means;
electrically connecting said second shield means to said first electrically conductive means using a solderless connecting means;
fastening said first shield means and said second shield means to said first electrically conductive means to establish an EMI shield enclosure for the printed circuit board and the electronic circuitry while permitting exposure of second electrically conductive means to the electronic circuitry.
surrounding said electronic circuitry with a first electrically conductive means internal to the printed circuit board and connecting said first electrically conductive means to an electrical ground;
communicating electrical signals with the electronic circuitry using a second electrically conductive means, said second electrically conductive means electrically separate from and passing through said first electrically conductive means to the electronic circuitry;
associating a channel means with said first electrically conductive means to prevent EMI having a predetermined wavelength from passing through the printed circuit board to the electronic circuitry, said channel means passing through the printed circuit board and having an electrically conductive means;
electrically connecting said channel means to said first electrically conductive means;
covering and isolating a top aspect of the electronic circuitry from EMI using a first shield means;
electrically connecting said first shield means to said first electrically conductive means using a solderless connecting means;
covering and isolating a bottom aspect of the electronic circuitry from EMI using a second shield means;
electrically connecting said second shield means to said first electrically conductive means using a solderless connecting means;
fastening said first shield means and said second shield means to said first electrically conductive means to establish an EMI shield enclosure for the printed circuit board and the electronic circuitry while permitting exposure of second electrically conductive means to the electronic circuitry.
5. A method for selectively isolating EMI from a plurality of electronic circuits on a printed circuit board while permitting exposure of electrical leads to the plurality of electronic circuits, the leads being integral to the printed circuit board, comprising the steps of:
placing an electrically conductive means on the printed circuit board, said electrically conductive means for outlining areas on the printed circuit board containing the plurality of electronic circuits, said electrically conductive means permitting the electrical leads to pass under said electrically conductive means to a predetermined portion of the electronic circuits, said electrically conductive means further electrically connected to a ground potential;
placing a plurality of EMI wave barrier means in association with said electrically conductive means and through the printed circuit board, each of one said EMI wave barrier means at a predetermined distance from adjacent ones of said wave barrier means, said distance not greater than a predetermined wavelength of the EMI, for which the electronic circuits are susceptible, said EMI barrier means establishing a barrier for preventing EMI from passing through the printed circuit board to the electronic circuits within said boundaries, isolating the electronic circuits from EMI with a top housing, said top housing covering a top portion of the printed circuit board and the electronic circuits and comprising engaging means for solderless engagement of said electrically conductive means and electrically connecting said top housing to said electrically conductive means;
further isolating a predetermined portion the plurality of electronic circuits from the remainder of the electronic circuits covered by said top housing using an internal housing, said internal housing fastened to said top housing and comprising engaging means for solderless engagement of said electrically conductive means to electrically connect said internal housing to said electrically conducting means;
isolating the electronic circuits from EMI with a bottom housing, said bottom housing covering a bottom portion of the printed circuit board and electronic circuits and comprising an engaging means for engaging said electrically conductive means and forming a solderless electrical connection between said bottom housing and said electrically conductive means; and fastening said top housing and said bottom housing to the printed circuit board and in electrical contact with said electrically conductive means to establish a grounded EMI shield enclosure for the plurality of electronic circuits and an internal EMI
shield enclosure for said predetermined portion of the plurality of electronic circuits on the printed circuit board.
placing an electrically conductive means on the printed circuit board, said electrically conductive means for outlining areas on the printed circuit board containing the plurality of electronic circuits, said electrically conductive means permitting the electrical leads to pass under said electrically conductive means to a predetermined portion of the electronic circuits, said electrically conductive means further electrically connected to a ground potential;
placing a plurality of EMI wave barrier means in association with said electrically conductive means and through the printed circuit board, each of one said EMI wave barrier means at a predetermined distance from adjacent ones of said wave barrier means, said distance not greater than a predetermined wavelength of the EMI, for which the electronic circuits are susceptible, said EMI barrier means establishing a barrier for preventing EMI from passing through the printed circuit board to the electronic circuits within said boundaries, isolating the electronic circuits from EMI with a top housing, said top housing covering a top portion of the printed circuit board and the electronic circuits and comprising engaging means for solderless engagement of said electrically conductive means and electrically connecting said top housing to said electrically conductive means;
further isolating a predetermined portion the plurality of electronic circuits from the remainder of the electronic circuits covered by said top housing using an internal housing, said internal housing fastened to said top housing and comprising engaging means for solderless engagement of said electrically conductive means to electrically connect said internal housing to said electrically conducting means;
isolating the electronic circuits from EMI with a bottom housing, said bottom housing covering a bottom portion of the printed circuit board and electronic circuits and comprising an engaging means for engaging said electrically conductive means and forming a solderless electrical connection between said bottom housing and said electrically conductive means; and fastening said top housing and said bottom housing to the printed circuit board and in electrical contact with said electrically conductive means to establish a grounded EMI shield enclosure for the plurality of electronic circuits and an internal EMI
shield enclosure for said predetermined portion of the plurality of electronic circuits on the printed circuit board.
6. An EMI-shield enclosure for restricting communication of EMI signals among a plurality of electronic circuits on a printed circuit board and with external electronic circuits, comprising:
electrically conductive means on the printed circuit board, said electrically conductive means for outlining areas on the printed circuit board for containing the plurality of electronic circuits, said boundaries permitting electrical leads to the electronic circuitry to pass under said electrically conductive means to predetermined portions of the electronic circuits, said electrically conductive means further electrically connected to a ground potential;
a plurality of EMI wave barrier means in association with said electrically conductive means and passing through the printed circuit board, each of one said EMI wave barrier means at a predetermined distance from an adjacent one of said means, said distance not greater than a predetermined wavelength of the EMI for which the electronic circuits is susceptible, said EMI
barrier means establishing a barrier for preventing EMI
from passing through the printed circuit board to the electronic circuits within said boundaries, top housing means for isolating the electronic circuits from EMI, said top housing means covering a top portion of the electronic circuits and comprising engaging means for solderless engagement of said electrically conductive means and electrical connection of said top housing to the electrically conductive means;
internal housing means for further isolating a predetermined portion the electronic circuits from the remainder of the electronic circuits covered by said top housing means, said internal housing means fastened to said top housing means comprising engaging means for solderless engagement of said electrically conductive means and electrical connection of said internal housing to said electrically conducting means;
bottom housing means for isolating the electronic circuits from EMI, said bottom housing means covering a bottom portion of the electronic circuits and comprising a plurality of engaging means for solderless engagement of said electrically conductive means and electrical connection of said bottom housing to said electrically conductive means and fastening means for fastening said top housing means and said bottom housing mean to the printed circuit board and in electrical contact with said electrically conductive means to establish a grounded EMI
shield enclosure for the plurality of electronic circuits and an EMI shield enclosure for such predetermined portion of the plurality of electronic circuits on the printed circuit board.
electrically conductive means on the printed circuit board, said electrically conductive means for outlining areas on the printed circuit board for containing the plurality of electronic circuits, said boundaries permitting electrical leads to the electronic circuitry to pass under said electrically conductive means to predetermined portions of the electronic circuits, said electrically conductive means further electrically connected to a ground potential;
a plurality of EMI wave barrier means in association with said electrically conductive means and passing through the printed circuit board, each of one said EMI wave barrier means at a predetermined distance from an adjacent one of said means, said distance not greater than a predetermined wavelength of the EMI for which the electronic circuits is susceptible, said EMI
barrier means establishing a barrier for preventing EMI
from passing through the printed circuit board to the electronic circuits within said boundaries, top housing means for isolating the electronic circuits from EMI, said top housing means covering a top portion of the electronic circuits and comprising engaging means for solderless engagement of said electrically conductive means and electrical connection of said top housing to the electrically conductive means;
internal housing means for further isolating a predetermined portion the electronic circuits from the remainder of the electronic circuits covered by said top housing means, said internal housing means fastened to said top housing means comprising engaging means for solderless engagement of said electrically conductive means and electrical connection of said internal housing to said electrically conducting means;
bottom housing means for isolating the electronic circuits from EMI, said bottom housing means covering a bottom portion of the electronic circuits and comprising a plurality of engaging means for solderless engagement of said electrically conductive means and electrical connection of said bottom housing to said electrically conductive means and fastening means for fastening said top housing means and said bottom housing mean to the printed circuit board and in electrical contact with said electrically conductive means to establish a grounded EMI
shield enclosure for the plurality of electronic circuits and an EMI shield enclosure for such predetermined portion of the plurality of electronic circuits on the printed circuit board.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08-041,522 | 1993-03-31 | ||
| US08/041,522 US5335147A (en) | 1992-02-12 | 1993-03-31 | EMI shield apparatus and methods |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2110639A1 true CA2110639A1 (en) | 1994-10-01 |
Family
ID=21916960
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2110639 Abandoned CA2110639A1 (en) | 1993-03-31 | 1993-12-03 | Emi internal shield apparatus and methods |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2110639A1 (en) |
-
1993
- 1993-12-03 CA CA 2110639 patent/CA2110639A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |