JPH1174669A - Radio frequency shield electronic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable shielding from emission and interference of radio frequencies(RF), by electrically connecting a track with a grounding plane, fixing a peripheral loop of a conductive elastomer to a board in a state of being connected with a peripheral track, and fixing a metal cover onto the loop. SOLUTION: An area 11 need not cover the entire main surface of a board 10, and the surface is partitioned into the area 11 where RF radiation raises a problem and an area 12 where radiation shield is not necessary. The area 11 is surrounded by a peripheral conductive track 13, a conductive elastomer loop 14 arranged thereon, and a conductive metal cover 15. The track 13 electrically contacts the grounding plane of the board through an appropriate path, and the track 13, the loop 14 and the cover 15 are assembled in electric contact with one another. Thus, all the surfaces of circuit components in the area 11 are surrounded by the conductive materials and therefore can be shielded from RF radiation and trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to electronic circuit boards, and more particularly, to an electronic circuit board that is shielded against unwanted emissions of radio frequency or unwanted interference from such radiation.

[0002]

BACKGROUND OF THE INVENTION As consumer electronics change to digital communications at higher bit rates and communications equipment transitions to the form of portable radio, there is greater shielding from radio frequency (RF) emissions and interference. It is becoming more and more important. The unshielded radiation of one user interferes with another user. In fact, at higher bit rates, RF emissions and interference are potential problems even within a single complex unit such as a computer.

[0003]

The most common approach to RF suppression is to shield radiating fragile components in a metal enclosure. However, this technique becomes more difficult as the bit transmission rate increases. See, for example, P. Nyholm et al., EMI Protection for Portable Consumer Products.
on in Consumer Portable Products) "(Electronic Pa
ckaging and Production, pp.40-44, March 1994)
Please refer to. Another approach is to shield with soft ferrite. To provide such shielding, cores, beads and connector plates are used. A disadvantage of such devices is that they are difficult to use with IC packages and electronic circuit boards that require high density connections. C.
Parker's "How to choose ferrite and how it works (How to
Select Ferrites and How They Work) "(EMC Test and
Design, pp. 26-29, January 1994).
Accordingly, there is a need for new arrangements that provide RF shielding for electronic circuit boards.

[0004]

SUMMARY OF THE INVENTION The present invention is an improved RF shielding configuration of an electronic circuit board that includes a conductive ground plane and one or more RF emitting (or RF vulnerable) electronic components. is there. A peripheral metal track is formed around the component on the substrate, and the track is electrically connected to a ground plane. Next, the peripheral loop of the conductive elastomer is fixed to the substrate by contacting the peripheral track,
Secure the metal cover on the loop. The conductive elastomer is desirably thicker than any component within the perimeter, and it is advantageous to pressurize the metal cover into the loop and seal it against radiation leakage.

[0005] The advantages, nature and various other features of the present invention will become more fully apparent upon consideration of the illustrative embodiments set forth in detail in conjunction with the accompanying drawings. It is to be understood that the drawings are illustrative of the concepts of the present invention and are not to scale.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, FIG.
1 is an exploded perspective view of an electronic circuit board 10 having a surface area 11 that includes one or more electronic components (not shown) that emit or are vulnerable to radiation. Substrate 10
Among the various structures used as electronic circuit boards such as conventional printed circuit boards and lead frame boards,
Either one may be used. As before, circuit board 10 has at least one metal layer (not shown) acting as a ground plane.
including. The ground plane is usually the inner metal layer. As shown, the region 11 need not surround the entire major surface of the substrate 10, and the surface can be divided into a region 11 where RF radiation is a concern and a region 12 where radiation shielding is unnecessary or undesirable. For example, region 12 may be an antenna region for a transceiver.

The region 11 is radiated by a peripheral conductive track 13 extending around the periphery of the region 11, a conductive elastomeric loop 14 disposed on the peripheral track, and a conductive metal cover 15 disposed on the loop. (Or electromagnetic interference). The track 13 is in electrical contact with the ground plane of the substrate via a suitable passageway, thus assembling and assembling the track 13, loop 14 and cover 15 in electrical contact. Therefore area 1
The circuit components in 1 are surrounded on all sides by a conductive material, namely a ground plane on the bottom, conductive elastomer loops 14 on the sides, and a metal cover 15 on the top. This arrangement shields against RF radiation or obstruction.

The conductive tracks 13 are preferably tin or gold, and the conductive elastomer loops 14 are advantageously silicon filled (mixed) with conductive particles such as carbon particles or metal powder. It is convenient to form the loop 14 into a predetermined shape in advance.

In a preferred application, electronic circuit board 10 is a wireless transceiver card, such as a PCMCIA form factor card. The shielded area 11 contains an RF amplifier and is an unshielded area 1 limited by a loop 14
2 includes an RF antenna. The RF signal is transmitted to the shielding area 11 and the antenna area 1 via a conductive signal layer inside the substrate.
2 is supplied. The circuitry of such a card is
PCMCIA / JEIOA PCC incorporated herein by reference
ard Standard, Vol. 3 (Feb. 1995) is a well-known PC card standard 0295-03-1500.

As better shown in FIGS. 2A and 2B, which are schematic cross-sectional views showing the closed configuration of the loop, the conductive elastomeric loop 14 has a flat track 13 and a flat cover 15 so as to fit properly. It is advantageous to have flat upper and lower surfaces 20,21. In the loop,
Preferably, an integral projection notch 22 is provided to fit the hole 23 in the track and frictionally secure the loop. The holes 23 can be plated with metal that is continuous with the tracks 13 to enhance the electrical contact between the loop and the ground plane. As shown in FIG. 2B, the cover 15 is preferably held under pressure against the top surface of the loop 14 for proper sealing and proper electrical contact.

FIG. 3 is a schematic exploded sectional view showing an alternative arrangement for packaging a circuit board. Here, circuit board 10 having major surfaces 10A and 10B includes circuit elements such as integrated circuit 30 and separate components 31 on both major surfaces. The substrate is disposed between a pair of conductive elastomer loops. The top metal cover 15 and the bottom metal cover 34 can lockably engage to squeeze the loop 14. In particular, the top cover 15 is provided with a recessed notch 33 and the bottom cover 34 is provided with a retaining tab 35 which engages with the notch 33 during assembly.

FIG. 4 is a cross-sectional view of the assembled structure of FIG. When the top cover 15 and the bottom cover 34 are pressed together, the loop 14 is squeezed and the tab 35 engages with the notch 33 in a lockable state.

It is to be understood that the above-described embodiments illustrate only a few of the many possible specific embodiments that may represent applications of the principles of the present invention. For example, while the invention has been illustrated for a single printed circuit board package assembly, it will be apparent that, with only minor modifications, the package can accommodate multiple boards, either stacked or coplanar. Accordingly, one of ordinary skill in the art may make myriad other alternatives without departing from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a first embodiment of an electronic circuit board shielded by a conductive elastomer loop.

FIG. 2A illustrates a method of securing the conductive elastomer loop of FIG. 1 to a substrate and sealing against radiation leakage.

FIG. 2B illustrates a method of securing the conductive elastomer loop of FIG. 1 to a substrate and sealing against radiation leakage.

FIG. 3 is an exploded cross-sectional view of a second embodiment of the electronic circuit board shielded by a conductive elastomer loop.

FIG. 4 is a schematic sectional view of the assembled substrate of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Electronic circuit board 11 area | region 12 area | region 13 conductive track 14 loop 15 metal cover 20 upper surface 21 lower surface 22 notch 23 hole 30 integrated circuit 31 component 33 notch 34 metal cover

Claims (9)

[Claims] 1. An RF shielding arrangement for an ionization circuit board, comprising: an electronic circuit board comprising a pair of major surfaces and a conductive ground plane; and one or more shieldedly mounted on at least one said major surface. An electronic component, and a conductive track on the major surface extending around the electronic component, the conductive track in electrical contact with the ground plane, and further extending around the electronic component. At least one existing
A loop of electrically conductive elastomeric material, the loop electrically contacting the conductive track, and further including a metal cover pressed against and contacting the loop, such that the cover, loop and ground plane are A shield configuration that surrounds electronic components and shields them from radio frequencies. 2. The method of claim 1, wherein the major surface including the component includes a first area to be shielded and a second area that does not need to be shielded, and a loop of the elastomeric material extends around the first area. The shield configuration according to claim 1, wherein: 3. The shield arrangement according to claim 2, wherein said first region to be shielded comprises an RF amplifier and said second region comprises an RF antenna. 4. The shield configuration according to claim 2, wherein said internal area of said circuit board includes a conductive path between said first area and said second area. 5. The wireless transceiver according to claim 1, wherein the electronic circuit board is a wireless transceiver.
The shield configuration according to claim 1, including a card. 6. A method according to claim 1, wherein each of said major surfaces is shielded.
The shield arrangement of claim 1, including one or more electronic components and individual loops of conductive elastomeric material extending around the periphery of the component. 7. The method of claim 6, further comprising a lockable top and bottom metal cover for locking each of said loops of conductive elastomer material together in a compressed position. Shield configuration as described. 8. The conductive track includes a plurality of holes,
The shield configuration according to claim 1, wherein the loop includes a plurality of protrusions that fit into the holes. 9. The shield arrangement according to claim 8, wherein said holes are plated with metal continuous with said conductive tracks to provide electrical contact between said loop and said ground plane. .