CN201541424U

CN201541424U - Radio frequency shielding structure

Info

Publication number: CN201541424U
Application number: CN2009201670772U
Authority: CN
Inventors: 王雪峰
Original assignee: Hangzhou H3C Technologies Co Ltd
Current assignee: New H3C Technologies Co Ltd
Priority date: 2009-07-27
Filing date: 2009-07-27
Publication date: 2010-08-04
Anticipated expiration: 2019-07-27

Abstract

The utility model discloses a radio frequency shielding structure comprising a shielding case and a printed circuit board (PCB). The PCB comprises a radio frequency protection zone and a shielding case contact zone. The shielding case contact zone is provided with split solder pads arranged in adjacency, the solder pads are connected with a power supply and the earth, and solder bumps are arranged on the solder pads. Fitting margins between the shielding case and the shielding case contact zone are adjusted by utilizing the low height and hardness and easy deformation characteristics of the solder bumps. The shielding case is well linked and matched with the PCB after normally assembled, gaps between the adjacent solder bumps assembled can not become electromagnetic interference leakage channels, and radio frequency shielding is realized.

Description

A kind of radio shielding structure

Technical field

The utility model relates to the board design technical field, relates in particular to a kind of radio shielding structure.

Background technology

By use dividing, the electromagnetic wave that will have certain wavelength and can be used for radio communication is called radio frequency, and the product that develops based on the radio frequency theory is called radio frequency products.The signal frequency range of radio frequency products is at 30M～6GHz, and wherein high-frequency signal can pass through air dielectric radiation towards periphery, and peripheral circuits is caused electromagnetic interference.Therefore, when the design radio frequency veneer, to carry out shielding protection to circuit and the sensitive circuit around it with intense radiation source.

Radome is to use the most general a kind of shielding measure in the radio frequency products; operation principle is as follows: (for example insert high-conductivity metal between electromagnetic emission source and need protective circuit; the high-conductivity metal radome is set) on the need protective circuit; this metallic shield can reflect and the absorption portion radiation field, and the ability of reflection and absorption depends on the conductance of electromagnetic frequency/wavelength, metal, needs the multiple factors such as distance of protective circuit to emission source.

Press the difference of radome and PCB (Printed Circuit Board, printed circuit board) dress connection technology, radome can be divided into solder type and mechanical assembly type two classes.Wherein, the solder type radome is that radome is welded direct on the PCB; Machinery assembling radome is interconnected with the PCB realization by frame modes such as screws.Wherein, concerning the large scale radome, reason such as yielding and thermal capacitance is bigger owing to radome self, welding operation is difficult to be realized, so use mechanical assembling scheme more; In addition, part adopts the machinery assembling radome of particular design (top design is the fin profile) can also realize the shielding and the two kinds of functions of dispelling the heat simultaneously.

Wherein, machinery assembling radome can be divided into following two kinds again by appearance difference: a kind of the radome size is less shown in Fig. 1 a and Fig. 1 b, adopts aluminium alloy compression casting or high accuracy punch forming more, and inside is cavity 110; The outside is a radiator 120, can realize radiofrequency signal shielding and heat sinking function simultaneously; The radome bottom has fixing hole 130, is used for by screw to PCB.Another kind as shown in Figure 2, the radome size is bigger, adopts traditional metal plate punching, bending and molding more, cost is low, the cover body light weight.

The scheme that mechanical at present assembling radome adopts usually is to design bright copper (the bareness copper consistent with the radome profile earlier on PCB; the copper sheet that the PCB surface is directly exposed; outward appearance is identical with pad) district; this zone connects power supply ground; as shown in Figure 3; what have the zone 340 that needs protection on the pcb board 310 is provided with bright copper zone 330 on every side, near bright copper zone 330 fixing hole 320 is set.During assembling the radome body is directly contacted with the bright copper zone 330 of PCB, cooperate, on PCB, with radiation source with need protective circuit to isolate, realize being connected shielding with screw by the fixing hole on fixing hole on the pcb board 310 320 and the radome 130.

The radome anti-electromagnetic interference capability can reach desirable level in theory, determine the key of its actual performance to be the situation that is connected between radome and PCB, therefore, very high to the radome requirement on machining accuracy, the body surface of radome and PCB contact zone must be smooth, in addition, because radio frequency circuit/microstrip line coupler is to PCB surface treatment thickness sensitivity, and the requirement of radome good earth, the PCB surface treatment is required harsh.If cooperate between radome and PCB and tightly do not have the seam opening, when opening length during near the partial radiation signal wavelength, just can become the electromagnetic interference leakage path, shield effectiveness will be had a greatly reduced quality.The wireless device that with the operating frequency is 900MHz is an example.Its fundamental wavelength is about 33cm, and ten subharmonic are 9GHz, wavelength 3.3cm.If can produce the electromagnetic interference leakage path, equipment performance is descended with the Faraday cage shielding that contains this 3.3cm grooved opening.

Yet in the radome of the machinery assembling at present process, the radio frequency pcb board is thick thinner usually, and Reflow Soldering or screw assembling process cause plate to stick up easily, have the slit thereby cause between assembling back radome and PCB, influence shield effectiveness.In addition, the radome self-deformation also is that a problem, particularly radome are big more, the cover wall is thin more, just easy deforming more.

Another kind of scheme is at the large scale radome in the prior art, and assembling scheme can be regarded a kind of scheme optimization as.End view increases soft conductive rubber 430 as shown in Figure 4 on the bright copper zone of radome 410 and PCB420.Because large scale radome more than 410 adopts the pressing and bending moulding, comprises and cuts, dashes, rolls over three process, it is generally not high to be subjected to each operation cumulative errors to influence surface smoothness.Therefore, also can between cover body and the bright copper of PCB, increase a soft conductive rubber 430 on the fastening basis of screw during assembling, play the effect that filling chink strengthens shielding.

Yet owing to increased conductive adhesive tape, production, design cost increase; In addition, though conductive adhesive tape has conductivity, compare its conductive earthing degradation with directly contacting bright copper scheme.

The utility model content

The utility model provides a kind of radio shielding structure, on the basis that does not increase extra frock and cost, promotes the allowance that cooperates between radome and PCB.

The utility model provides a kind of radio shielding structure; comprise radome and PCB circuit board; described PCB circuit board comprises radio frequency protection zone and radome contact zone; described radome contact zone is distributed with the discrete pad of adjacent arrangement; described pad is connected with power supply ground; it is protruding that described pad is provided with tin.

Described pad center is apart from the 1/n harmonic number that is no more than signal wavelength.

The protruding edge distance of adjacent tin after the described assembling is no more than the 1/n harmonic number of signal wavelength.

The protruding height of tin on the described discrete pad is identical.

Described pad be shaped as circle, rectangle or ellipse.

If radome contact zone broad, described pad is staggered at least two rows.

Distance between described adjacent two row's pads satisfies processing technology, and the described adjacent pad center distance that is arranged in same row is no more than the 1/n harmonic number of signal wavelength.

Compared with prior art, the utlity model has following advantage:

In the utility model, increased the cooperate window of radome, effectively remedied contact surface evenness defect of insufficient with the PCB contact-making surface; Evaded the problem that part PCB surface treatment condition can not good earth; And saved the use of auxiliary materials such as conductive rubber, reduced design cost.

Description of drawings

Fig. 1 a and Fig. 1 b are aluminium alloy compression casting or high accuracy punch forming structure charts in the prior art;

Fig. 2 is the shielding case structure figure of a kind of metal plate punching, bending and molding in the prior art;

Fig. 3 designs the Liang Tong district schematic diagram consistent with the radome profile on PCB in the prior art;

Fig. 4 is the end view that increases soft conductive rubber on the bright copper zone of radome and PCB in the prior art;

Fig. 5 is a PCB circuit board schematic diagram in a kind of radio shielding structure in the utility model;

Fig. 6 is the assembling schematic diagram that finishes between radome and PCB in the utility model.

Embodiment

In the utility model, it is protruding to increase tin between the contact area of radome and PCB, utilize the low yielding characteristics of protruding height of tin and hardness to strengthen the allowance that cooperates between radome and PCB, when the contact-making surface out-of-flatness between radome and the PCB contact area, in assembling process, to the original highly identical different active forces of the protruding generation of tin, make the protruding generation different deformation of tin, guarantee better to be connected cooperation with PCB after the normal assembling of radome, avoid conventional face contact to occur the problem of large tracts of land loose contact easily, and then guarantee that the slit of the adjacent tin in assembling back between protruding can not become the electromagnetic interference leakage, the shield effectiveness of realizing ideal.

The utility model provides a kind of radio shielding structure, comprises radome and PCB circuit board.PCB circuit board 510 comprises radio frequency protection zone 520 and radome contact zone 530, and as shown in Figure 5, radome contact zone 530 is the zones that contact with radome that are positioned on the PCB circuit board 510; Radio frequency protection zone 520 is the electronic circuit zone, generally is the electromagnet source region, but some situation also may be circuit or the device region that is subject to electromagnetic interference.The discrete pad of adjacent arrangement is set on the radome contact zone 530, these pads are connected with power supply ground, it is protruding to set up tin on these pads, utilize the low yielding characteristics of protruding height of these tin and hardness to regulate the allowance that cooperates between radome and radome contact zone during assembling, when radome and PCB contact-making surface are smooth, to the protruding generation same function of highly identical tin power, make the identical deformation of the protruding generation of tin, the edge of radome 620 contacts with PCB610 by tin protruding 630; Even radome and PCB contact-making surface are not at ordinary times, in assembling process, to the original highly identical different active forces of the protruding generation of tin, make the protruding generation different deformation of tin, guarantee that radome normally assembles the back and is connected cooperation with PCB, and then guarantee that the slit of the adjacent tin in assembling back between protruding can not become the electromagnetic interference leakage, the shield effectiveness of realizing ideal.

Wherein, tin is protruding to be the alloy projection that is formed in bond pad surface by scolder after the Reflow Soldering, wherein, the paste mixture that scolder is made up of solder powder, solder flux, solvent and additive, select for use production common soldering paste commonly used to get final product, recommending (Sn-Pb) is solder cream, and this is the hardness lower (as Sn63Pb37) that soldering paste forms solder joint, radiator and the tin good contact matching between protruding when helping guaranteeing to assemble.In addition, because film of flux residue can have influence on the contact effect, preferably low welding assisted agent residuals model soldering paste.

Wherein, the discrete pad of adjacent arrangement one by one is set on the radome contact zone 530 on the PCB circuit board 510, it is protruding on these pads tin to be set.Wherein, bond pad shapes can adopt circle or regular polygon (being not less than regular hexagon), so that guarantee the consistency of solder joint shape.In fact pad can also adopt other shapes, for example oval, square or pentagon etc., but because the influence of factors such as processing technology is best with the circle.Tin convex bottom face shape and corresponding bonding pad form fit, for example for circular pad, the tin convex bottom face is circular.Generally, the protruding height of the tin on the discrete pad is identical, if but there is minute differences in tin between protruding, and can in the assembling allowed band.

When radome contact zone 530 broads, also can be designed as the pad of double staggered (even three rows are interlocked or the like), promptly double tin is protruding, to strengthen shield effectiveness.Pad distance between adjacent two row's tin are protruding satisfies processing technology and gets final product.The pad gap requires pad limit spacing (air gap) minimum value to be not less than 0.4mm, with the realizability that guarantees steel mesh opening (general steel mesh producer promise to undertake attainable steel mesh opening the wide 0.4mm of being of foot bridge).Pad diameter is optional apart from deducting in the scope of pad gap (c-d) in pad center, preferably approaches the contact width of radome.

Distance is relevant with the frequency and the harmonic number of corresponding radio frequency source between the adjacent pad in same row, pad center can not surpass the 1/n (n is a harmonic number) of signal wavelength apart from maximum, or the protruding edge of adjacent tin after the assembling is apart from the 1/n harmonic number that is no more than signal wavelength, can not become the electromagnetic interference leakage to guarantee the slit of the adjacent tin in assembling back between protruding.

Radome and PCB circuit board assembling process are as follows:

At first, because tin is protruding in the PCB surface, radome contacts with the protruding top of tin earlier during assembling;

Then, along with the increase of radome in the assembling process and protruding active force of tin, the protruding top of tin is flattened gradually, and is indivedual owing to difference in height has gone up with protruding also the contact gradually of the tin of radome contact;

Finally, the radome assembling finishes, and all tin convex into the top and are a faceted contact point, have realized the effect that touch screen covers between radome and PCB.

Between radome and PCB the assembling finish after as shown in Figure 6, the edge of radome 620 contacts with PCB610 by tin protruding 630, because tin protruding 630 has plasticity, under ambient pressure, can be out of shape, when radome and PCB contact-making surface are smooth, to the protruding generation same function of highly identical tin power, make the identical deformation of the protruding generation of tin, the edge of radome 620 contacts with PCB610 by tin protruding 630; Even radome and PCB contact-making surface are not at ordinary times, to the original highly identical different active forces of the protruding generation of tin, make the protruding generation different deformation of tin, therefore can remedy the physical deformation of radome 620 and PCB610 by protruding 630 deformation of tin, avoid excesssive gap, slit between the adjacent tin in assurance assembling back is protruding can not become the electromagnetic interference leakage, the shield effectiveness of realizing ideal.

More than disclosed only be several specific embodiment of the present utility model, still, the utility model is not limited thereto, any those skilled in the art can think variation all should fall into protection range of the present utility model.

Claims

1. a radio shielding structure comprises radome and PCB circuit board, it is characterized in that; described PCB circuit board comprises radio frequency protection zone and radome contact zone; described radome contact zone is distributed with the discrete pad of adjacent arrangement, and described pad is connected with power supply ground, and it is protruding that described pad is provided with tin.

2. radio shielding structure as claimed in claim 1 is characterized in that, described pad center is apart from the 1/n harmonic number that is no more than signal wavelength.

3. radio shielding structure as claimed in claim 1 is characterized in that, the protruding edge distance of the adjacent tin after the described assembling is no more than the 1/n harmonic number of signal wavelength.

4. radio shielding structure as claimed in claim 1 is characterized in that, the protruding height of the tin on the described discrete pad is identical.

5. radio shielding structure as claimed in claim 1 is characterized in that, described pad be shaped as circle, regular polygon or ellipse.

6. radio shielding structure as claimed in claim 1 is characterized in that, described pad is staggered at least two rows.

7. radio shielding structure as claimed in claim 6 is characterized in that, distance satisfies processing technology between described adjacent two row's pads, and the described adjacent pad center distance that is arranged in same row is no more than the 1/n harmonic number of signal wavelength.