Background technology
Usually, the Electromagnetic Interference in numeral and high-frequency circuit element is when electronic unit and microstrip transmission line are installed on the substrate, is produced by the electromagnetic coupled between this electronic unit and the microstrip transmission line.
According to routine, in order to suppress this Electromagnetic Interference, by using the thick relatively individual layer electro-magnetic abortion film that surpasses 0.2mm, and by in the output separately of circuit substrate, connecting low pass filter or noise filter, perhaps by keeping spacing between electronic unit and the microstrip transmission line being suppressed at the Electromagnetic Interference in the problematic circuit, thereby address this problem.
Yet the method for above-mentioned inhibition Electromagnetic Interference requires space and spacing that absorber is set, and described absorber has described filter or thickness is not less than 0.2mm, thereby produces the size of increase electronic device and the problem of weight.
In order to make full use of space limited between these parts and the circuit substrate, in order to be suppressed at the electromagenetic wave radiation that produces in circuit substrate and the parts, and in order to be suppressed at the electromagnetic interference that produces between other contiguous circuit blocks, so the low pass filter or the noise filter of relative large space of not instructions for use and spacing, and using thin electro-magnetic wave absorption film, it is made up of the individual layer that thickness is no more than 0.1mm.
The mechanism of absorption of this electro-magnetic abortion film is mainly given the credit to the high frequency loss characteristic (high-frequency loss property) of material.Generally speaking, the material that is used as electro-magnetic abortion film classifies as has conduction loss, dielectric absorption, at least two material in magnetic loss or these losses.In these materials, the material that uses magnetic loss is by being dispersed in magnetic metallic powder the form that is fabricated to film in the organic binder bond, and described film has the thickness that is no more than 0.1mm.Yet in being no more than the frequency band of 1GHz, because thin thickness, therefore electromagnetic power loss is no more than 35%, and shows the restriction of characteristic.Measure above-mentioned result as shown in Figure 1.
Fig. 1 is the chart of power loss that the conduction electro-magnetic wave of electro-magnetic wave absorption film is shown, this film is made by the magnetic metal composite of coating use ferro-silicon-aluminium (Fe-Si-Al alloy) powder as individual layer, and the thickness of this film is (1) 0.025mm, (2) 0.05mm, (3) 0.075mm and (4) 0.1mm.The thickness that is appreciated that this film is thick more, and power loss is high more.
At the curve (1) of Fig. 1, (2), in (3) and (4), along with frequency raises, ripple shortens, and therefore this electromagnetic power loss uprises.Yet in being no more than the frequency band of 1GHz, the electro-magnetic wave absorption film that has a problem to be to use thickness to be no more than 0.1mm is difficult to obtain to be not less than or to be higher than 35% electromagnetic wave absorptivity.
Summary of the invention
Technical problem
The present invention creates in order to solve above-mentioned traditional problem.For the conducted noise that makes thickness be no more than the thin electro-magnetic wave absorption film of 0.1mm suppresses maximum effect, its objective is by lamination conductive polymer membrane on magnetic metal composite a kind of improved electro-magnetic wave absorption film is provided, the electromagnetic wave absorptivity of this film in the frequency of 10MHz~6GHz is not less than 35%, thereby shows constant resistance.
Another object of the present invention is to provide a kind of thin multilayer electro-magnetic wave absorption film by lamination conductive polymer coating and magnetic metal composite, this film has flexible (flexibility) that is no more than 0.1mm thickness, and makes the attenuating maximization by electromagnetic sealing in the electronic device or electromagnetic noise attentuation.
Another object of the present invention is by direct polymerization PEDOT on magnetic metal composite, conductive polymer and thin multilayer electro-magnetic wave absorption film through applying is provided.
Another object of the present invention provides the thin multilayer electro-magnetic wave absorption film that thickness is no more than 0.1mm, and it can (acquisition be not less than 50% higher attenuating in 0.3~3GHz) at the quasi-microwave band.
Technical scheme
In order to reach purpose of the present invention as discussed above, the invention provides a kind of thin multilayer electro-magnetic wave absorption film, this film comprises magnetic metal composite, the conductive polymer coating and the soft magnetic metal that wherein have the constant resistance between 20 Ω~1000 Ω disperse and combination by organic binder bond, and described magnetic metal composite comprises that two-layer at least layer structure and thickness are no more than 0.1mm.
In addition, the present invention further provides thin multilayer electromagnetic wave absorption film, wherein said magnetic metal composite is positioned in the middle of the layered structure and described conductive polymer coating is laminated to the surface, upper and lower of described magnetic metal composite, in the middle of perhaps conductive polymer coating is positioned at and magnetic metal composite be laminated to the surface, upper and lower of this conductive polymer coating.
In addition, the present invention further provides thin multilayer electro-magnetic wave absorption film, wherein the intermediate layer binding agent in layered structure passes through directly to apply, bonding component, or the mode of compression is set up.
In addition, the present invention further provides thin multilayer electro-magnetic wave absorption film, wherein said conductive polymer coating is by PEDOT, polyaniline, and one of polypyrrole and polythiophene are made.
In addition, the present invention further provides thin multilayer electro-magnetic wave absorption film, wherein the sheet resistance of the described PEDOT layer by controlling described conductive polymer coating is that 100 Ω~500 Ω make the electromagnetic wave absorptivity maximization in being no more than the 500MHz frequency bandwidth.
In addition, the present invention further provides thin multilayer electro-magnetic wave absorption film, wherein dry then with polymerization and form described conductive polymer coating by the monomer solution that on described magnetic metal composite, directly applies described PEDOT.
In addition, the present invention further provides thin multilayer electro-magnetic wave absorption film, wherein, form described conductive polymer coating by on PET film or PP film, applying described PEDOT.
Hereinafter, will explain formation of the present invention in detail.
Beneficial effect
According to the present invention as above, comprise that magnetic metal composite and conductive polymer coating and thickness are no more than the thin multilayer electro-magnetic wave absorption film of 0.1mm, the effect of material production that is used for conducting polymer and magnetic metallic powder is than good as the material of known electro-magnetic wave absorption film.
Depend on laminating method, thin multilayer electro-magnetic wave absorption film of the present invention produces and stops electromagnetic effect very effectively, thereby do not influence electric semiconductor (electricsemiconductor), the equipment in telecommunication field, cellular parts and shell (case) and be used for the equipment of mobile communication, electric digital image device etc.
Embodiment
Conductive polymer coating of the present invention is included in the constant resistance between 20 Ω to 1000 Ω, and the sheet resistance of magnetic metal composite is 10
6~10
8Between the Ω, near insulation.
Usually, use the electro-magnetic abortion film of ohmic loss to use resistance.It is fabricated to the form of the polyurethane that contains carbon usually.If resistance is 20 Ω or following, conductance is high relatively, and when electromagnetic wave is absorbed, because its loss of Low ESR reduces.The loss of absorbed electromagnetic wave by internal resistance is converted to heat and disappears.Its principle is similar to lead or electric mattress (electric mattress) produces heat.Be absorbed in the process that this electro-magnetic abortion film disappears then at electromagnetic wave, the impedance of electro-magnetic abortion film has significant effects.The impedance of air is 377 Ω, and if the impedance of this electro-magnetic abortion film be 377 Ω (with the air impedance phase like), its electromagnetic wave penetrates this electro-magnetic abortion film with 100%.Yet if the impedance of this electro-magnetic abortion film is lower than 20 Ω, and thus far below the impedance of air 377 Ω, this electromagnetic wave can not penetrate this electro-magnetic abortion film, but major part is reflected.Therefore, it can not be used for this electromagnetic wave, because this electromagnetic wave is reflected before being absorbed.
Therebetween, this electro-magnetic abortion film with the sheet resistance that is higher than 1000 Ω is very good aspect electromagnetic penetrability, yet, the problem that exists low resistance to lose.This is because use the electromagnetic wave absorb of ohmic loss to cause absorption of electromagnetic wave by the internal charge polarization, but polarized amount of charge is considerably less.
Therefore, produce big loss, the material that preferably has sheet resistance between 20 Ω~1000 Ω for higher electromagnetic wave penetrability and by charge polarization.
Even the sheet resistance of magnetic metal composite is 10
6~10
8Between the Ω, the reason that material still has the effect that absorbs electric wave is because magnetic loss is used in the electric wave absorption loss water of magnetic metal composite, rather than ohmic loss.
Utilization is from PEDOT (polyethylene dioxythiophene), polyaniline, a kind of one or both sides that this conducting polymer are laminated to magnetic metal composite that polypyrrole and polythiophene are chosen.Top laminating method is by directly applying bonding component, or compress mode enforcement.
Especially, in order to maximize electro-magnetic wave absorption in being no more than the frequency bandwidth of 500MHz, the sheet resistance of the PEDOT layer of this described conductive polymer coating is controlled at 100 Ω~500 Ω.With reference to figure 4, be under the situation of 300 Ω (being similar to airborne impedance) in sheet resistance, it shows that absorptivity is maximized in being no more than the frequency bandwidth of 500MHz.At 300MHz, electromagnetic wave absorptivity approximately is 43%.Yet under the situation with 200 Ω sheet resistances, in the frequency bandwidth of 300MHz, electromagnetic wave absorptivity approximately is 18%, yet is no more than in sheet resistance under the situation of 100 Ω, electro-magnetic wave absorption can not take place.
Simultaneously, have under the situation of 500 Ω sheet resistances of surpassing, be difficult to 30% or the above electromagnetic wave absorptivity of acquisition in the frequency bandwidth of 300MHz at this electromagnetic wave absorb.
Polymeric layer according to the present invention is as follows.By dissolving 3 in organic solvent (as 1-butanols or 1-propyl alcohol), 4-polyethylene dioxythiophene (as the conducting polymer monomer), polyvinylpyrrolidone (as matrix polymer), and n-methyl pyrrolidone and dimethyl formamide (as basic additive) are prepared monomer solution.By dissolving in the solvent of same type benzene methanesulfonic acid iron (being used as oxidant) is prepared oxidiferous solution.By the oxidiferous solution of ready monomer solution and this is mixed prepare homogeneity solution after, thus obtained soln using spin coating on magnetic metal composite (spin coating), bar are coated with (barcoating) or are with the method that is coated with (tape coating) to be coated on PET film or the PP film.If the substrate through applying heats special time in baking box, that means predetermined temperature, and this monomer is aggregated and forms the conductive PEDOT film subsequently, and it utilizes methyl alcohol, and purifications such as acetone are to obtain final PEDOT film.If change the content of polyvinylpyrrolidone, basic content of additive, the solubility of oxidant and polymerization temperature and time, the surperficial non-resistance of the PEDOT film that this prepares can easily change the sheet resistance of this PEDOT film through applying.Another execution mode of coated with conductive polymeric layer of the present invention is as follows.After being ready to solvable polypyrrole, preparing polypyrrole solution in the chloroform by it is dissolved in, and this solution is coated on this substrate according to institute reported method (Korean Patent No.0162864-0000).Substrate is dried special time, use purifications such as methyl alcohol, acetone then, oven dry can obtain final electric polypyrrole film then then.
Another execution mode of coated with conductive polymeric layer of the present invention is as follows.
After being ready to solvable polypyrrole, preparing polypyrrole solution in the chloroform by it is dissolved in, and this solution is coated on this substrate according to institute reported method (Korean Patent No.0205912-0000).Substrate is dried special time and used methyl alcohol, and purifications such as acetone can obtain final electric polypyrrole film then.
Simultaneously, this magnetic metallic powder that is used for conductive polymer coating of the present invention is by sendust (Fe-Si-Al), permalloy (Fe-Ni), pure iron powder (fe), carbonyl iron, molybdenum permalloy (Fe-No-Mo), ferrite, stainless steel (Fe-Cr, any composition Fe-Cr-Ni) or in silicon steel (Fe-Si) powder.
In addition, the organic binder bond that is used for this magnetic metal composite is by PVC (polyvinyl butyral resin), polyurethane rubber, silicon rubber, polyethylene, polyvinyl chloride, EPDM, butadiene rubber, polypropylene or polystyrene, or any composition in the natural rubber.Above-mentioned this organic binder bond of mentioning is characterised in that they are good at the maintenance powders, and can therefore be allowed can thoroughly be disperseed by the powder that this binding agent keeps assembling by organic solvent dissolution.
Can be by the thin multilayer electro-magnetic wave absorption film that magnetic metal composite and conductive polymer coating are formed by utilizing bonding component such as electric insulation binding agent, the mode of bonding paste (adhesion paste) or DR tape (double tape) is in conjunction with formation.This bonding component can be easy to be attached on the electronic device.
Top this thin multilayer electro-magnetic wave absorption film of the present invention will be as follows by execution mode specific explanations with reference to the accompanying drawings.
Fig. 2 is the accompanying drawing that embodiment of the present invention is shown.
Fig. 2 (a) is the viewgraph of cross-section that thickness is no more than the thin multilayer electromagnetic wave absorb of 0.1mm, wherein, magnetic metal composite 21 is by disperseing combination and soft magnetic metal powder in blocks to form by organic binder bond, conductive polymer coating 22 forms by coat conducting polymer in the one side, and at the opposite side of this conductive polymer layer 22 in conjunction with bonding component 23, as binding agent, bonding paste or DR tape are to attach release film 24.
At this conductive polymer coating 22, electromagnetic wave is at first by the ohmic loss decay, and in this magnetic metal composite 21, this electromagnetic wave is decayed by magnetic loss once more.Compare its excellent with the magnetic metal composite membrane of forming by a layer.
In the superincumbent multilayer film, at the liquid phase state that is disperseed by this organic binder bond, use Dr.Blade, band is coated with, and methods such as spin coating apply the combination between the complete layer equably.Perhaps, it can or use bonding paste by the electricity combination, and binding agent or DR tape compress them and form.
Simultaneously, shown in Fig. 2 (b), conductive polymer coating 22 is positioned at top, and magnetic metal composite 21 is laminated to the bottom, and forms bonding component 23 and release film 24.
In addition, as for an embodiment of the invention, as have three layers multilayer electro-magnetic wave absorption film, shown in Fig. 2 (c), the present invention can select conductive polymer coating 21 is combined in the structure on the surface, upper and lower of this magnetic metal composite 22.In addition, shown in Fig. 2 (d), can select magnetic metal composite 22 is connected the structure on the surface, upper and lower of this conductive polymer coating 21.
In order to check effect, measure electromagnetic wave absorptivity by following method according to thin multilayer electro-magnetic abortion film of the present invention.
In order to measure the electromagnetic wave absorptivity of electro-magnetic wave absorption film of the present invention, as shown in Figure 3, the copper 83 of the about 2mm of length 80mm width is set on the top of microstrip circuit substrate 81, and the end of this microstrip circuit substrate is connected with the SMA type terminals 85 of 3.5mm.
The bottom of this microstrip circuit substrate is made up of copper layer 84, and the absorbing film 82 with pre-set dimension is positioned at the top of this copper cash, measures the power loss of conduction electro-magnetic wave noise then.
The electro-magnetic wave absorption film that is used for inventing above is of a size of the square of length of side 50mm.Be understandable that the equipment that is used to measure described electromagnetic wave absorptivity is analyzed the attenuating of electro-magnetic wave absorption film,, and be attenuated from the signal that an end conducts to the other end so that this film is combined in the equipment that is used to analyze vector network.
The result of the absorptivity that measures by described method as shown in Figure 4.
Figure shown in Figure 4 expresses the electromagnetic wave absorptivity of the thin multilayer film that comprises double-layer structure, this structure is shown in Fig. 2 (a), by on this magnetic metal composite, coating conducting polymer (PEDOT), this magnetic metal composite is disperseed and combination by organic binder bond, and bonding component is combined in the bottom of this conductive polymer coating.
The fixed thickness of this magnetic metal composite is 0.03mm, on it, by control surface resistance is 20 Ω (71) equably, 50 Ω (72), 80 Ω (73), 100 Ω (74), 230 Ω (75) and 300 Ω (76), this conductive polymer coated thickness is 0.005~0.020mm, and the gross thickness of this thin multilayer film is set at 0.05mm.
The electromagnetic wave absorptivity that the data that contrast described data among described Fig. 4 and electromagnetic wave absorptivity illustrate according to the thickness of conducting metal composite single layer film is no more than 30% in being no more than the 1GHz frequency, opposite the present invention in the frequency of 1GHz, obtain 85% or on the electromagnetic wave absorptivity of (74).
Especially, under the situation that this electro-magnetic wave absorption film according to the present invention is made up of magnetic metal composite and conductive polymer coating, the present invention shows excellent electromagnetic wave absorptivity, even this absorptivity also can not be obtained by the magnetic metal composite single layer in being no more than the 500MHz frequency.
Therefore, wherein the film of the present invention of lamination magnetic metal composite of the present invention and conductive polymer coating can prevent short circuit and make the electromagnetic wave absorptivity maximization, keeps thickness at 0.1mm or following simultaneously.
The present invention mainly explains based on preferred implementation of the present invention as above.Yet the present invention can or be modified to the degree that is no more than scope of the present invention by those skilled in the art's appropriate change.As long as the type that changes or revise does not deviate from main idea of the present invention, obviously it is within the scope of right of the present invention.
Technical scope of the present invention is not limited to the specific descriptions of this specification.