Circuit board component shielding enclosure and assembly

An EMI shielding assembly includes an elongated enclosure made of an electrically conductive material and having a plurality of interconnected walls arranged in a polygonal configuration to surround an electronic component on a circuit board, a plurality of mounting pins attached to lower portions of the walls and extending downwardly from a lower edge thereon for attachment to the circuit board, and plurality of inner and outer tabs formed in upper portions of the walls which extend upwardly from the lower portions thereof. The inner and outer tabs are disposed in spaced apart, alternating and offset relationship with respect to one another along the upper portions of the walls so as to create an annular channel therebetween which extends around the enclosure along the upper portions of the interconnected walls thereof. The shielding assembly also includes a cover made of an electrically conductive material and having side portions removably inserted into the annular channel defined by the inner and outer tabs and into a frictional fitting relation therebetween to thereby removably mount the cover over the enclosure so as to provide an EMI shield for the electronic component therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to shielding devices for minimizing 
electromagnetic interference and, more particularly, is concerned with an 
enclosure and an assembly employing the enclosure for providing effective 
shielding of circuit board compoents against electromagnetic interference. 
2. Description of the Prior Art 
Electronic components found in various types of transmitters, receivers, 
computers and other electronic devices emit or are susceptible to 
electromagnetic radiation. It is therefore desirable to shield circuit 
components to reduce undesirable electromagnetic interference (EMI) and/or 
susceptibility effects with the use of conductive shields that reflect or 
dissipate electromagnetic charges and fields. Such shields are generally 
grounded to allow electrical charges and fields to be dissipated without 
disrupting the operation of the electronic components enclosed within the 
shield. 
Various types of shielding devices for electronic components mounted on 
printed circuit boards have been proposed in the prior patent art. 
Representative examples of such shielding devices are the ones disclosed 
in U.S. patents to Stickney et al (U.S. Pat. No. 4,754,101), Hibino et al 
(U.S. Pat. No. 4,841,414), McCoy, Jr. (U.S. Pat. No. 5,014,160), Rogers et 
al (U.S. Pat. No. 5,043,848), Johnson (U.S. Pat. No. 5,095,177), Fry et al 
(U.S. Pat. No. 5,160,807) and Moore (U.S. Pat. No. 5,175,395); a Japanese 
patent to Tsunoda (U.S. Pat. No. 62,595), and a German patent to Bardon 
(U.S. Pat. No. 3,736,833). These shielding devices frequently include a 
base frame which is mounted to the printed circuit board surrounding the 
circuit board components, and a cover which fits over and connects with 
the base frame enclosing the printed circuit board components. 
Various difficulties may be encountered with respect to providing a 
satisfactory connection of the cover to the base frame. The connection 
must secure the cover to the base frame in a reliable manner which 
prevents dislodgement due to shock and vibration. At the same time, the 
connection must permit easy removal of the cover for periodic visual 
inspection of the printed circuit board and the components enclosed by the 
shield. 
As an example, such difficulties may be experienced with respect to the 
electromagnetic shielding assembly of U.S. Pat. No. 4,754,101 to Stickney 
et al. The shielding assembly of this patent has a cover plate and a base 
frame with a plurality of walls made from a length or strip of metallic 
material. The base frame is formed in a rectangular configuration so as to 
surround the electronic component on the circuit board. The base frame has 
a plurality of spaced mounting pins projecting downwardly from a lower 
edge of the strip for alignment within holes in the circuit board. The 
base frame also has a plurality of spaced deflectable engagement prongs 
defined by spaced slots and extending upwardly from an upper edge of the 
strip. The prongs have flanged upper end to allow insertion of the cover 
plate within the base frame and outwardly formed recesses between the 
flanged upper ends to receive and hold the cover plate. The 
above-described design of the shielding assembly of the Stickney et al 
patent fails to provide any positive means for preventing inadvertent 
overinsertion of the cover plate downwardly past the recesses of the 
prongs which can result in overdeflection thereof and damage thereto and 
to the electronic component enclosed by the shielding assembly. 
Consequently, a need still exists for improvement in the design of 
shielding devices for printed circuit board components. 
SUMMARY OF THE INVENTION 
The present invention provides a circuit board component shielding 
enclosure and assembly designed to satisfy the aforementioned need. The 
shielding assembly of the present invention employs an enclosure of the 
present invention and a cover frictionally interfitted therewith which 
together provide effective EMI shielding of components while allowing the 
cover to be easily fitted to and removed from the enclosure. The shield 
assembly has features providing a secure attachment with and a positive 
downward stop of the cover relative to the enclosure while allowing easy 
removal of the cover for component accessibility. 
Accordingly, the present invention is directed to a circuit board component 
shielding enclosure which comprises: (a) a plurality of interconnected 
walls arranged in a polygonal configuration to surround an electronic 
component on a circuit board, each of the walls having a lower portion and 
an upper portion extending upwardly from the lower portion; (b) a 
plurality of mounting pins attached to the lower portions of the 
respective walls and extending downwardly from lower edges thereon for 
attachment to the circuit board; and (c) a plurality of inner and outer 
tabs formed in the upper portions of the respective walls, the inner and 
outer tabs being disposed in spaced, alternating and offset relationship 
with respect to one another along the upper portions of the walls so as to 
create an annular channel between the inner and outer tabs extending along 
the upper portions of the respective interconnected walls. 
Also, the present invention is directed to a circuit board component 
shielding assembly which comprises: (a) the above-defined enclosure; and 
(b) a cover having a top portion and a plurality of side portions attached 
to and extending downwardly from the top portion and arranged in a 
polygonal configuration matching that of the interconnected walls of the 
enclosure. The side portions of the cover are removably inserted into the 
annular channel defined by the inner and outer tabs and into a frictional 
fitting relation therewith to thereby removably mount the cover over the 
enclosure and provide an electromagnetic interference shield for the 
electronic component. 
These and other features and advantages of the present invention will 
become apparent to those skilled in the art upon a reading of the 
following detailed description when taken in conjunction with the drawings 
wherein there is shown and described an illustrative embodiment of the 
invention.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings and particularly to FIGS. 1 to 3, there is 
illustrated a circuit board component electromagnetic shielding assembly, 
generally designated 10, of the present invention. Basically, the 
shielding assembly 10 includes an elongated fence or enclosure 12 of the 
present invention and a cover 14 fitted over the enclosure 12. The 
enclosure 12 and cover 14 are preferably made of a suitable electrically 
conductive material, such as a conductive metal. 
Referring to FIGS. 1 and 2, the enclosure 12 of the shielding assembly 10 
is defined by an elongated generally planar strip of material bent at 
spaced apart locations to define corners 16 of the enclosure 12 and a 
plurality of generally planar walls 18 extending between and 
interconnected by the corners 16. The walls 18 are thus arranged in a 
polygonal, preferably rectangular, configuration adapting the enclosure 12 
to surround an electronic component (not shown) mounted on a circuit board 
B (see FIG. 6). 
Referring to FIGS. 1, 2, 5 and 6, the enclosure 12 of the shielding 
assembly 10 also includes a plurality of mounting pins 20 attached to 
lower portions 18A of the walls 18 and extending downwardly from lower 
edges 22 thereon. The mounting pins 20 are preferably integrally formed 
with and in the plane of the respective walls 18. The mounting pins 20 are 
provided to facilitate attaching of the enclosure 12 to the circuit board 
B by inserting the mounting pins 20 into selected ones of a plurality of 
holes H (only one being shown in FIG. 6) through the circuit board B and 
then by soldering the mounting pins 20 to electrically conductive 
receptacles (not shown) provided on the circuit board B. 
Referring to FIGS. 2, 4, 5 and 6, the enclosure 12 of the shielding 
assembly 10 also includes a plurality of inner and outer tabs 24, 26. The 
inner and outer tabs 24, 26 are formed in respective upper portions 18B of 
the walls 18 which extend upwardly from the respective lower portions 18A 
thereof to upper edges 28 of the walls 18. The inner and outer tabs 24, 26 
are disposed in spaced apart, alternating and offset relationship with 
respect to one another along the upper portions 18B of the walls 18 so as 
to create a continuous annular channel 30 therebetween which extends 
around the enclosure 12 along the upper portions 18B of the interconnected 
walls 18 thereof and is open from above to receive the cover 14. 
More particularly, the outer tabs 26 in the upper portion 18B of each wall 
18 are integrally connected to the lower portion 18B of the wall 18 and, 
in effect, constitute continuations or extensions of the lower portion 18A 
of wall 18 which extend substantially in the plane of the lower portion 
18A of the wall 18. Only portions of the upper edge 18B of each wall 18 
which constitute the upper ends 26A of the outer tabs 26 are flared 
outwardly beyond the plane of the wall 18 so as to make it relatively easy 
to insert the cover 14 downwardly into the annular channel 30 defined 
between the inner and outer tabs 24, 26. 
The inner tabs 24 in the upper portion 18B of each wall 18 are integrally 
connected to the lower portion 18A of the wall 18 and extend in an offset 
fashion inwardly and upwardly therefrom. As mentioned above, these offset 
inner tabs 24 are arranged in an alternating fashion with the outer tabs 
26 of the upper portion 18B of the wall 18. The upper upper ends 24A of 
the inner tabs 24 are flared inwardly so as to make it relatively easy to 
insert the cover 14 downwardly into the annular channel 30 defined between 
the inner and outer tabs 24, 26. As stated above, outer tabs 26, which are 
remaining sections of the upper portion 18B of the wall 18 being merely 
continuations of the lower portion 18A of the wall 18, do not outwardly 
deflect to any significant degree when the cover 14 is inserted into and 
removed from the annular channel 30. Most of the deflection occurs in 
offset inner tabs 24. Thus, the offset inner tabs 24 are made by a 
conventional forming operation wherein portions of the upper portion 18B 
of the wall 18 are cutout between the inner and outer tabs 24, 26 and then 
the inner tabs 24 are bent about two spaced parallel locations thereon to 
place them in the offset relationship to the wall 18. The lower inwardly 
extending portions of the inner tabs 24 where they are integrally 
connected to the wall 18 provide positive downward stops 24B which prevent 
overinsertion of the cover 14 onto the enclosure 12. 
Referring to FIGS. 1, 3 and 6, the cover 14 of the shielding assembly 10 
has a top portion 32 and a plurality of side portions 34 integrally 
attached to and depending downwardly from the top portion 32. The side 
portions 34 of the cover 14 are arranged in a polygonal, preferably 
rectangular, configuration matching that of the interconnected walls 18 of 
the enclosure 14. However, the perimeter size of the cover 14 is matched 
with that of the annular channel 30 so as to permit the side portions 34 
of the cover 14 to be removably inserted into the annular channel 30 
defined between the inner and outer tabs 24, 26 and into a frictional 
fitting relation therebetween to thereby removably mount the cover 14 over 
the enclosure 12, as seen in FIG. 1, and provide an EMI shield for the 
electronic component (not shown) enclosed by the shielding assembly 10. 
FIGS. 2, 3, 5 and 7 show an optional feature which can be employed in the 
shielding assembly 10 of the present invention. A plurality of dimples 36 
can be formed on the side portions 34 of the cover 14 which will 
interengaged with selected ones of respective holes 36 defined through the 
inner tabs 24 of the enclosure 12. This feature provides a releasable 
snap-in lock connection in addition to the frictionally fitted connection 
which may be desirable in applications where the shielding assembly 10 
will be subject to severe vibrations. 
It is thought that the present invention and its advantages will be 
understood from the foregoing description and it will be apparent that 
various changes may be made thereto without departing from its spirit and 
scope of the invention or sacrificing all of its material advantages, the 
form hereinbefore described being merely preferred or exemplary embodiment 
thereof.