CN1196870A

CN1196870A - RF shield for circuit card

Info

Publication number: CN1196870A
Application number: CN 96197100
Authority: CN
Inventors: 马修P·卡塞博尔特
Original assignee: Metricom Inc
Current assignee: Metricom Inc
Priority date: 1995-09-22
Filing date: 1996-09-11
Publication date: 1998-10-21
Also published as: EP0852108A1; JPH11511595A; WO1997011592A1; CA2231150A1; MX9802266A; EP0852108A4

Abstract

A metallized plastic RFI/EMI shield is provided against electromagnetic energy for a circuit card (32) wherein the shield is formed of a box enclosure with two casing halves to enclose the card (32), the first casing half having a solid flange side walls surrounding the card (32) and the second casing half (24) having a flange (26) formed by flat, plate-like closely-spaced fingers (28), the fingers confronting, being in electrical contact with and mating in full length with substantially the entire periphery of the side walls of the first casing half. The fingers (28) are preferably spaced with a separation of less than 1/4 wavelength of any measurable harmonic of the intended operating frequency, typically up to the tenth harmonic. A slot (18) may be provided to receive the fingers (28) on the outside of the side walls, and closely-spaced grounding pins arranged around the periphery of the card (32) may extend between the first and second casing halves through ground plated perforations (34) along the edge of the side walls.

Description

The radio shielding box of circuit board

The present invention relates to electromagnetic shielding problem that radio circuit is faced.Exactly, the present invention relates to provide the shielding box of being convenient to make for the circuit board of launching useless electromagnetic radiation.

For useless high frequency (r, f) to inject row shielding be a challenge problem to the width of cloth because the character that has according to slot (flute profile) antenna structure, as if any very little hole can form radiating aperture by accident on the shielding box.In the prior art, must provide some levels of masking or screen to stop useless emission and to satisfy the administrative standard that suppresses emission.Have now found that the hole of main source of leakage at the screen periphery.Yet main consideration is manufacturability in mass production applications.Testing and customize each box between erecting stage is infeasible to guarantee that it satisfies emission standard, and cost is very high.What need is that box can be made easily, and easy and circuit board assembling also can avoid the influence of useless r.f radiation fully.

According to the present invention, metalized plastics RFI/EMI is provided shielding, be used for providing shielding its electromagnetic energy to circuit board, this shielding is to be made of the chamber that two half boxes that separate are arranged, encase circuit board, first half box has the solid flange sidewall around circuit board, and second half box has the flange that is made of the little spacing fingertip of flat plate shape, and fingertip electrically contacts facing to the whole periphery of first half box sidewall and with it and closely cooperates fully.The fingertip spacing is preferably less than any 1/4 wavelength of measuring harmonic wave under the predetermined work frequency.The slit can be provided, receiving the fingertip of sidewall outside, the intensive ground connection pin of settling along the circuit board periphery can be passed the first and second half boxes by the ground hole of electroplating along the edge of sidewall.

In conjunction with the accompanying drawings, will understand the present invention better with reference to following detailed description.

Fig. 1 is the perspective view of the first half boxes of shielding box.

Fig. 2 is the perspective view of second half box of shielding box, and itself and first half box closely cooperates to constitute the effective r.f shielding of the present invention.

Fig. 1 is the perspective view according to first half box 10 of shielding box of the present invention.Any first box of appointment, this half box 10 comprises the substrate 12 of entity, the sidewall 14 of the entity flange that stretches out along whole box periphery.As selection, in the outside of sidewall 14 lip 16 can be arranged, be used for constituting slit 18 at lip 16 with between the sidewall 14 of whole peripheries of substrates 12.As known to, each circuitous path of r.f signal will increase path loss, thereby will increase the validity that suppresses.Insulation wall 20 in inside has, and insulation wall is placed along sidewall in some, and some then cross substrate.Shown as present embodiment, interior insulation wall has the intensive groove 22 or the hole of rule along its (inwardly) edge.On the other hand, groove can be and above-mentioned groove 22 close-fitting jut or pins that the back will illustrate that these grooves and jut constitute the another kind of level of masking and be pseudo-emission ground connection.

Referring now to Fig. 2, is the perspective view according to second half box 24 of r.f shielding box of the present invention.According to the present invention, half box 10 and 24 lumped together just constitute effective r.f shielding chamber.Second half box 24 closely cooperates with first half box 10 and forms the predetermined level of masking.The structure of second half box 24 is guiding.According to the present invention, along whole peripheries second flange 26 is arranged, it is to be made of intensive fingertip 28.The flex plate that fingertip 28 is normally flat, its surface inwardly should be with consistent with the external surface shape of the flange 16 of its close-fitting first half box 10.Fingertip 28 and flange 16 mutual sliding contact when two and half boxes combine.Fingertip 28 stretches into selects slit 18, for r.f sets up circuitous path.

Fingertip 28 mutual spacings are very little, and the narrow slit between general mutual close two fingertips is much smaller than 1/4 wavelength.Optimal cases is 1/4 wavelength of this spacing less than maximum detection amount harmonic wave under the r.f emission first-harmonic operating frequency.Typical pitch is 1/4 wavelength (1/8 wavelength of 5 subharmonic) of ten subharmonic.It is suitable that thin space pair carries out effective r.f sealing with the edge that can provide good mechanical to be slidingly matched.Plate shape fingertip 28 produces flexible self-holding other a pressure that cooperates with integral-type flange 14.

The material that constitutes shielding box can be the plastics of metal or plating, promptly with the plastics that apply or electroplate copper and mickel.Copper provides electromagnetic shielding, and nickel provides scuff resistance.The various technologies of prior art can obtain coating uniformly and effectively.

Shielding box is used for potted circuit plate 32 (pressing Fig. 2 imagination), and wherein circuit board 32 is consistent with box.According to the present invention, second half box 24 has insulation wall 120, insulation wall 20 couplings of itself and second half box.In the present embodiment, intensive jut 30 or pin are positioned at the inner face of wall 120, and with the groove fit of first half box 10.It also is equivalent replacing.The jut 30 of two halves box is not that the hole 34 of directly slotting oversampling circuit plate 32 is exactly the periphery that presses circuit board 32.Hole 34 must be electroplating ventilating hole, and perhaps periphery one is decided to be the plating limit, to form the ground connection border at the edge along circuit board 32.Protuberance 30 reaches along the inboard of flange 14 between the circuit board of half box and insulation wall 120 and 20 conductive path is provided.This structure has also strengthened inner and outside r.f shielding.

Explained the present invention with reference to specific embodiment now.Those skilled in the art are conspicuous to the embodiment of other form.Thereby except that claims, the present invention is unrestricted.

Claims

1. one kind is used for the shielding box that the electromagnetic circuit plate shields electromagnetic energy, it is characterized in that described shielding box comprises:

The chamber that is used for described electromagnetic circuit plate, described chamber has first box and second box, described first box has entity first flange of qualification round first profile of the sidewall of described electromagnetic circuit plate, described second box has second flange of second profile that limits sidewall, wherein, described second profile is made of intensive fingertip, described fingertip facing to electrically contacting and in whole length the whole periphery along described sidewall cooperate with described first profile.

2. according to the shielding box of claim 1, it is characterized in that described fingertip is separated from each other, spacing is less than 1/4 wavelength of the harmonic wave measured of the first-harmonic operating frequency of described electromagnetic circuit.

3. according to the shielding box of claim 1, it is characterized in that described fingertip is dull and stereotyped, has the face of facing described first profile flexibly.

4. according to the shielding box of claim 3, it is characterized in that described second box is made of the plastics of plating, wherein said fingertip flexibly with described first outline.

5. according to the shielding box of claim 1, it is characterized in that described sidewall is placed in the border that is limited by described fingertip.

6. according to the shielding box of claim 5, it is characterized in that described first box also comprises the lip of placing with described parallel sidewalls, limit the receiving slit of described fingertip.

7. according to the shielding box of claim 6, it is characterized in that described electromagnetic circuit plate has the periphery of plating, comprise that also many intensive pins and described periphery closely mate, and outstanding from described first box, enter second box by described periphery.

8. according to the shielding box of claim 6, it is characterized in that described electromagnetic circuit plate has the ground hole in a week, described first box comprises that also many intensive pins and described hole closely mate, and outstanding from described first box, enters described second box by described periphery.

9. one kind is used for the shielding box that the electromagnetic circuit plate shields electromagnetic energy, it is characterized in that described shielding box comprises:

The chamber that is used for described electromagnetic circuit plate, described chamber has first box and second box, described second box is made by metalized plastics, described first box has entity first flange of first profile that limits the sidewall that centers on described electromagnetic circuit plate, described second box has second flange of second profile that limits sidewall, wherein said second profile is made of intensive fingertip, described fingertip facing to electrically contacting and in whole length whole periphery and described first profile along described sidewall closely cooperate, wherein said fingertip is dull and stereotyped, have flexible face facing to described first profile, fingertip is each other with less than 1/4 wavelength of the harmonic wave measured of described electromagnetic circuit first-harmonic operating frequency separately.

10. according to the shielding box of claim 9, it is characterized in that described first box also comprises the lip that is seated in described parallel sidewalls, limits the receiving slit of described fingertip.

11. the shielding box according to claim 10 is characterized in that, described electromagnetic circuit plate has the periphery of plating, also comprises many intensive pins, closely cooperate with described periphery, and outstanding from described first box, enter described second box by described periphery.