CN111589675B - High-thermal-conductivity electromagnetic wave absorption composite sheet and preparation method thereof - Google Patents

High-thermal-conductivity electromagnetic wave absorption composite sheet and preparation method thereof Download PDF

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CN111589675B
CN111589675B CN202010418156.7A CN202010418156A CN111589675B CN 111589675 B CN111589675 B CN 111589675B CN 202010418156 A CN202010418156 A CN 202010418156A CN 111589675 B CN111589675 B CN 111589675B
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wave
layer
absorbing layer
heat
heat conduction
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CN111589675A (en
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刘立东
朱航飞
单震
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Hengdian Group DMEGC Magnetics Co Ltd
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Hengdian Group DMEGC Magnetics Co Ltd
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    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
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    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
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    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
    • B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by features of form at particular places, e.g. in edge regions
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    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
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    • B32B37/10—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
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    • B32B7/04—Interconnection of layers
    • B32B7/08—Interconnection of layers by mechanical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/005—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile
    • B32B9/007—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile comprising carbon, e.g. graphite, composite carbon
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    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00—Constructional details common to different types of electric apparatus
    • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2039—Modifications to facilitate cooling, ventilating, or heating characterised by the heat transfer by conduction from the heat generating element to a dissipating body
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    • H05K9/00—Screening of apparatus or components against electric or magnetic fields
    • H05K9/0073—Shielding materials
    • H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
    • H05K9/0088—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a plurality of shielding layers; combining different shielding material structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/212—Electromagnetic interference shielding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
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    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/302—Conductive

Abstract

The invention belongs to the field of electromagnetic wave absorption materials, and discloses a high-thermal-conductivity electromagnetic wave absorption composite sheet and a preparation method thereof. The electromagnetic wave absorbing sheet material is formed by alternately laminating a plurality of wave absorbing layers and heat conducting layers, wherein the wave absorbing layers and the heat conducting layers are both of special-shaped structures with periodic uneven cross sections, and the wave absorbing layers comprise the following components in percentage by weight: high-molecular binder: 10% -20%, scaly soft magnetic alloy magnetic powder: 80% -90%, auxiliary materials: less than or equal to 1 percent; the thickness T1 of the wave-absorbing layer is 0.06-0.12 mm, the height H of the groove is 0.3-0.7 times of the thickness T1 of the wave-absorbing layer, the size of L2 is 5-10 mm, and the width of the groove L1 is 1-3 mm; the heat conducting layer comprises the following components in percentage by weight: high-molecular binder: 20% -50%, heat-conducting medium: 50% -80%, auxiliary agent: less than or equal to 2 percent. The thickness T2 of the heat conduction layer is 0.015-0.035 mm, the structure greatly shortens the distance between the heat conduction layer and the heat conduction layer, so that the heat conduction channel is more smooth, and the heat conduction coefficient of the material is greatly improved.

Description

High-thermal-conductivity electromagnetic wave absorption composite sheet and preparation method thereof
Technical Field
The invention relates to the technical field of electromagnetic wave absorption materials, in particular to a high-thermal-conductivity electromagnetic wave absorption composite sheet and a preparation method thereof.
Background
The electromagnetic wave absorption sheet material is an anti-electromagnetic interference material widely applied to consumer electronics products, and is mainly used for solving the problems of electromagnetic compatibility and electromagnetic radiation of electromagnetic products (such as smart phones, notebook computers and GPS navigators). The material mainly comprises a high-molecular binder and soft magnetic alloy magnetic powder, and has good electromagnetic wave absorption and shielding functions. The preparation process comprises a calendaring process and a casting process, wherein the calendaring process is used for preparing the magnetic sheet with lower magnetic permeability and thicker thickness (more than 0.2 mm), and the casting process can be used for preparing products with higher magnetic permeability and thinner thickness and is applied more and more.
Although the electromagnetic wave absorbing sheet material can solve the problems of electromagnetic compatibility and electromagnetic radiation to some extent, the electromagnetic wave absorbing sheet material has poor heat conductivity, and high integration and miniaturization of electronic products have made higher demands on the heat dissipation characteristics of the material. The reason that the electromagnetic wave absorbing sheet material has poor heat conductivity is mainly that the material contains a large amount of high molecular substances (generally, the mass percentage is higher than 10 percent), so that the heat conductivity coefficient is low and is generally 0.7-1.0W/(m.K); meanwhile, the electromagnetic wave absorption sheet is a homogeneous material, an effective heat dissipation channel cannot be provided, and the heat resistance is high, so that the heat dissipation characteristic is poor. For this reason, some researchers blend a thermal conductive agent (such as boron nitride, graphite, etc.) with the soft magnetic powder and then fill the mixture into a polymer material to improve the thermal conductivity of the material. However, the addition of the heat conductive agent reduces the volume ratio of the magnetic powder in the magnetic sheet, deteriorating the electromagnetic wave absorption and shielding properties of the magnetic sheet. Another solution is to stick a layer of heat conducting material on the surface of the material to improve the heat dissipation capacity, but the method has limited effect, mainly because the heat generated by the device can reach the heat conducting layer only through the wave absorbing sheet, the heat dissipation channel is not smooth, especially when the wave absorbing sheet is thick. Therefore, it is an urgent need to solve the above-mentioned problems by finding an electromagnetic wave absorbing material that has both heat conduction/dissipation characteristics and electromagnetic wave absorption/shielding characteristics.
Chinese patent application document CN201711223210.7 proposes a heat-conducting wave-absorbing magnetic sheet with a composite structure, the structure of the wave-absorbing layer and the heat-conducting layer of the magnetic sheet alternate lamination greatly improves the heat conductivity coefficient, the heat-conducting channel is also improved to a certain extent, while ensuring the electromagnetic wave absorption and shielding characteristics, the heat conductivity of the magnetic sheet is greatly improved, the density of the magnetic sheet is reduced, so that the magnetic sheet has the dual characteristics of electromagnetic noise absorption/shielding and heat conduction, and a better effect is obtained. However, the heat generated by the device in the technology still needs to pass through a plurality of wave-absorbing layers to be finally dissipated, so that the structure of the heat dissipation channel is not ideal.
Disclosure of Invention
The invention aims to overcome the defects of the background art and provides an electromagnetic wave absorbing sheet material with a novel structure and a preparation method thereof aiming at the problems of poor heat conduction and heat dissipation properties of the conventional electromagnetic wave absorbing sheet material.
In order to achieve the purpose of the invention, the electromagnetic wave absorbing sheet material is formed by alternately laminating a plurality of wave absorbing layers and heat conducting layers, wherein the wave absorbing layers and the heat conducting layers are of special-shaped structures with periodic uneven cross sections;
the wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 10 to 20 percent
Scaly soft magnetic alloy magnetic powder: 80 to 90 percent
Auxiliary materials: less than or equal to 1 percent
The thickness T1 of the wave-absorbing layer is 0.06-0.12 mm, the height H of the groove is 0.3-0.7 times of the thickness T1 of the wave-absorbing layer, the size of L2 is 5-10 mm, and the width of the groove L1 is 1-3 mm;
the heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 20 to 50 percent
A heat-conducting medium: 50 to 80 percent
Auxiliary agent: less than or equal to 2 percent
The thickness T2 of the heat conduction layer is 0.015-0.035 mm.
Furthermore, the high molecular binder in the wave absorbing layer is required to be suitable for tape casting, and the system is not limited and includes, but is not limited to, polyurethane, acrylic resin, epoxy resin, liquid nitrile rubber, ethyl cellulose, PVB and the like.
Further, the scaly iron-based alloy magnetic powder in the wave absorbing layer comprises one or more of Fe-Si, Fe-Si-Al, Fe-Si-Cr, Fe-Si-Al-Cr, Fe-Ni-Mo and Fe-Al, preferably Fe-Si-Al, Fe-Ni or Fe-Ni-Mo, the thickness of the magnetic powder is 0.8-1.8 mu m, and the diameter-thickness ratio (the diameter direction size and the thickness direction size) is more than 40: 1.
further, the auxiliary materials include, but are not limited to, anti-settling agents, coupling agents, dispersing agents, toughening agents and the like. The auxiliary material may be free of or include one or more of an anti-settling agent, a coupling agent, a dispersing agent, or a toughening agent.
Preferably, the groove height H of the wave-absorbing layer is 0.45-0.55 times of the thickness T1 of the wave-absorbing layer.
Further, the heat conducting layer polymer binder includes, but is not limited to, polyurethane, acrylic resin, epoxy resin, liquid nitrile rubber, ethyl cellulose, PVB, or the like; the binder is required to be suitable for casting, coating, spraying and the like.
Further, the heat conducting layer heat conducting medium is a carbon-based material, including but not limited to one or more of graphite, graphene or graphene micro-sheets.
Further, the heat conduction layer assistant includes, but is not limited to, a coupling agent, a dispersing agent, a leveling agent, an antifoaming agent, and the like, and one or more of the coupling agent, the dispersing agent, the leveling agent, or the antifoaming agent may be not added or may be contained.
On the other hand, the invention also provides a preparation method of the high-thermal-conductivity electromagnetic wave absorption composite sheet, which comprises the following steps:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent, scaly soft magnetic alloy magnetic powder and auxiliary materials, and then carrying out vacuum defoaming treatment on the slurry to obtain the uniformly-mixed wave-absorbing layer slurry with the viscosity suitable for tape casting;
(2) preparing a wave-absorbing layer: coating the uniformly mixed slurry obtained in the step (1) on a PET film to obtain a casting film, drying, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave absorbing layer unit, wherein the thickness of the casting film is T1; the surface of the PET film is of a rugged structure, and the height of the bulges is H;
(3) preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent, auxiliary materials and a high-molecular binder, and then performing defoaming treatment to obtain heat-conducting layer slurry with the viscosity of 2000-;
in the invention, the viscosity of the slurry of the heat conduction layer needs to be controlled to 2000-3500 mPas. The viscosity is too high, so that the slurry cannot be completely filled to the groove of the wave-absorbing layer, and the final product has air holes at the corner of the bottom of the groove; the solvent amount is too much, the viscosity is too low, a large number of cavities can be formed in the heat conduction layer in the subsequent drying process, the density of the heat conduction layer can be influenced, and the heat conduction effect is finally influenced;
(4) coupling and activating the wave-absorbing layer: preparing an activating liquid, uniformly dispersing a coupling agent in a solvent, wherein the concentration of the coupling agent is not more than 0.5%, spreading and fixing a completely dried wave-absorbing layer on a base film, wherein a base surface with a concave-convex structure faces upwards, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, wherein the thickness of the coupling agent layer is less than 1 mu m, and naturally drying for later use;
the coupling agent system is not limited, and the bonding strength of the wave absorbing layer and the heat conducting layer can be improved;
(5) preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface of the wave-absorbing layer with the concave-convex structure after coupling and activating treatment, and then drying to obtain a composite unit of the wave-absorbing layer and the heat conduction layer;
the coating process includes, but is not limited to, casting, coating, spraying;
(6) repeating the steps (1) to (5) to obtain a plurality of composite units of the wave absorbing layer and the heat conducting layer;
(7) and carrying out hot pressing on the plurality of composite units to finally obtain the high-heat-conductivity electromagnetic wave absorption composite sheet.
Further, in order to uniformly disperse the binder and the auxiliary material in the solvent, the solvent is preferably a low-boiling solvent.
Furthermore, in order to facilitate the film forming of the wave absorbing layer, silicone oil is coated on the surface of the PET film.
Compared with the prior art, the invention has the following advantages:
(1) compared with the traditional wave-absorbing magnetic sheet, the electromagnetic wave-absorbing composite sheet material provided by the invention is formed by alternately laminating a plurality of wave-absorbing layers and heat-conducting layers, wherein the cross sections of the heat-conducting layers and the wave-absorbing layers are of uneven special structures, the structure greatly shortens the distance between the heat-conducting layers, enables the heat-conducting channels to be more smooth and greatly improves the heat conductivity coefficient of the material. Meanwhile, the invention limits the sizes and thicknesses of the heat conduction layer and the wave absorption layer, so that the composite sheet material has good wave absorption/shielding and heat conduction performances.
(2) The heat conducting layer of the electromagnetic wave absorption composite sheet material provided by the invention adopts the carbon material as the heat conducting medium, so that on one hand, the heat conducting property of the material is greatly improved, and meanwhile, the light weight of the material is facilitated, and the density of the whole material is reduced. In addition, the filling proportion of the carbon-based heat-conducting medium in the heat-conducting layer is limited, and the heat-conducting layer has certain electromagnetic wave absorption and shielding properties in the range, so that the composite sheet material has good heat-conducting property and the electromagnetic wave absorption/shielding properties are not influenced.
(3) The invention takes the PET film with a rugged structure and a special structure as a base film and is assisted by a hot pressing process to prepare the electromagnetic wave absorption composite sheet material, and the invention has the following characteristics:
a. the invention limits the viscosity of the heat-conducting slurry, and the excessive viscosity can cause that the slurry can not be completely filled to the groove of the wave-absorbing layer, and the final product has air holes at the corner of the bottom of the groove; the solvent amount is too much, the viscosity is too low, a large number of cavities can be formed in the heat conduction layer in the subsequent drying process, the density of the heat conduction layer can be influenced, and the heat conduction effect is finally influenced;
b. in order to improve the bonding strength between the heat conduction layer and the wave-absorbing layer, particularly at the groove, and avoid the problems that the heat conduction layer and the wave-absorbing layer cannot be well bonded, air holes are generated, the wave-absorbing layer cannot be formed after hot pressing and the like, the wave-absorbing layer is subjected to coupling activation treatment before the heat conduction layer is prepared, and meanwhile, the concentration of a coupling agent solution and the thickness of a coupling layer are limited, so that the interface bonding between the heat conduction layer and the wave-absorbing layer is improved, and the performance of the composite sheet material is further improved.
Drawings
Fig. 1 is a cross-sectional structure of the electromagnetic wave absorbing composite sheet of the present invention, wherein 1 is a heat conducting layer, and 2 is a wave absorbing layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. It is to be understood that the following description is only illustrative of the present invention and is not to be construed as limiting the present invention.
The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
The indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the number clearly indicates the singular.
Further, the technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.
Example 1
The electromagnetic wave absorption composite sheet is of a structure that a plurality of wave absorption layers and heat conduction layers are alternately laminated, the number of the wave absorption layers and the number of the heat conduction layers are determined according to the requirement of actually required thickness, and the wave absorption layers and the heat conduction layers are of special-shaped structures with periodic uneven cross sections. In order to obtain higher electromagnetic wave absorption/shielding performance and heat conduction performance, strict requirements are made on the material composition and the key size of the wave absorbing layer and the heat conduction layer.
(1) The wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 11.8 percent
Scaly soft magnetic alloy magnetic powder: 88 percent
Auxiliary materials: less than or equal to 0.2 percent
The high-molecular binder is polyurethane;
the scale-shaped soft magnetic alloy magnetic powder is Fe-Si-Al magnetic powder, the average thickness of the scale-shaped soft magnetic alloy magnetic powder is 1.1 mu m, and the diameter-thickness ratio (the size in the diameter direction and the size in the thickness direction) is more than 82: 1.
the auxiliary material comprises a silane coupling agent KH 550.
The thickness T1 of the wave-absorbing layer is 0.1mm, and the height H of the groove is 0.5 times of the thickness T1 of the wave-absorbing layer, namely 0.05 mm; the L2 dimension was 7mm and the groove width dimension L1 was 1.5 mm.
(2) The heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 40 percent of
A heat-conducting medium: 59.4 percent
Auxiliary agent: 0.6 percent
The binder is polyurethane;
the heat-conducting medium is graphite;
the auxiliary agent is a silane coupling agent KH 550;
the thickness T2 of the heat conduction layer is 0.02 mm.
The preparation method of the electromagnetic wave absorption composite sheet comprises the following steps:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent, scaly soft magnetic alloy magnetic powder and auxiliary materials, and performing vacuum defoaming treatment on the slurry to obtain uniform wave-absorbing layer slurry suitable for tape casting; wherein the solvent is absolute ethyl alcohol.
(2) Preparing a wave-absorbing layer: coating the uniformly mixed slurry on a PET film, drying the casting film, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave-absorbing layer unit; wherein the casting film thickness was 0.2 mm.
The surface of the PET film is of a rugged structure, the height of the bulges is 0.1mm, and silicone oil needs to be coated on the surface of the PET film in order to facilitate the film forming of the wave-absorbing layer.
(3) Preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent, auxiliary materials and a high-molecular binder, and then defoaming the slurry to obtain uniformly-mixed heat-conducting layer slurry with certain viscosity; wherein the solvent is absolute ethyl alcohol, and the viscosity of the heat conduction layer slurry is 2935 mPas.
(4) Coupling and activating the wave-absorbing layer: preparing an activating liquid, wherein the coupling agent is a silane coupling agent KH-550, uniformly dispersing the coupling agent in absolute ethyl alcohol solvent, the concentration of the coupling agent is 0.2%, spreading and fixing a completely dried wave-absorbing layer (with a concave-convex structure, the base surface facing upwards) on a base film, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, and naturally drying the layer to be used.
(5) Preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface (a base surface with a concave-convex structure) of the wave-absorbing layer subjected to coupling activation treatment to obtain a composite unit of the wave-absorbing layer and the heat conduction layer; wherein, the coating process is casting, and the thickness of the casting film of the heat conduction layer is 0.04 mm.
(6) And (5) repeating the steps (1) to (5) to obtain 3 composite units of the wave absorbing layer and the heat conducting layer.
(7) And (3) carrying out hot pressing on the composite units according to the requirement, wherein the hot pressing compression ratio is 50%, and finally obtaining the electromagnetic wave absorption composite sheet material with the total thickness of 0.36 mm.
Comparative example 1
The difference of the comparative example of the embodiment 1 is that the sheet material has no heat conduction layer, only has a single wave-absorbing layer, the thickness of the casting film of the single wave-absorbing layer is 0.24mm, the composition and the proportion of the components of the wave-absorbing layer are the same as those of the embodiment 1, and the thickness of the final electromagnetic wave absorbing sheet is 0.36 mm.
Comparative example 2
As a comparative example of example 1, there is a difference in that both the wave-absorbing layer and the heat-conducting layer in the sheet-type material are flat and smooth surfaces, i.e., there is no particular uneven structure, and the thickness of the final electromagnetic wave-absorbing sheet is 0.36 mm.
The materials prepared in example 1, comparative example 1 and comparative example 2 were respectively tested for shielding performance, wave-absorbing performance (reflection loss), thermal conductivity and density, and the test results are shown in table 1.
TABLE 1 test results of the materials prepared in example 1 and comparative examples 1-2
Figure BDA0002495861150000091
As is clear from the results in table 1, the shielding performance and reflection loss of example 1 are comparable to those of comparative example 1 and comparative example 2, and it was confirmed that the shielding performance and reflection loss are not significantly deteriorated by introducing the heat conductive layer and the special concavo-convex structure. However, the thermal conductivity of example 1 is significantly higher, the thermal conductivity is better, and the density is greatly reduced, which is beneficial to the light weight of the material.
Example 2
The electromagnetic wave absorption composite sheet is of a structure formed by alternately laminating a plurality of wave absorption layers and heat conduction layers, the number of the wave absorption layers and the number of the heat conduction layers are determined according to the requirement of actually required thickness, and the wave absorption layers and the heat conduction layers are of irregular structures with periodic uneven cross sections. In order to obtain higher electromagnetic wave absorption/shielding performance and heat conduction performance, strict requirements are made on the material composition and the key size of the wave absorbing layer and the heat conduction layer.
(1) The wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 11 percent of
Scaly soft magnetic alloy magnetic powder: 89 percent
The high-molecular binder is polyurethane;
the scale-shaped soft magnetic alloy magnetic powder is Fe-Si-Al magnetic powder, the average thickness of the scale-shaped soft magnetic alloy magnetic powder is 1.1 mu m, and the diameter-thickness ratio (the size in the diameter direction and the size in the thickness direction) is more than 82: 1.
the thickness T1 of the wave-absorbing layer is 0.08mm, and the height H of the groove is 0.5 times of the thickness T1 of the wave-absorbing layer, namely 0.04 mm.
The L2 dimension was 6mm and the groove width dimension L1 was 1.2 mm.
(2) The heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 35 percent of
A heat-conducting medium: 65 percent of
The binder is polyurethane;
the heat-conducting medium is a graphite microchip;
the thickness T2 of the heat conduction layer is 0.02 mm.
The preparation method of the electromagnetic wave absorption composite sheet comprises the following steps:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent and scaly magnetic powder, and performing vacuum defoaming treatment on the slurry to obtain uniform wave-absorbing layer slurry suitable for casting; wherein the solvent is absolute ethyl alcohol;
(2) preparing a wave-absorbing layer: coating the uniformly mixed slurry on a PET film, drying the casting film, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave-absorbing layer unit; wherein the thickness of the casting film of the wave-absorbing layer is 0.16 mm.
The surface of the PET film is of a rugged structure, the height of the bulges is 0.08mm, and in order to facilitate the wave-absorbing layer to form the film, the surface of the PET film needs to be coated with silicone oil.
(3) Preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent and a high-molecular binder, and then defoaming the slurry to obtain uniformly-mixed heat-conducting layer slurry with certain viscosity; wherein the solvent is absolute ethyl alcohol, and the viscosity of the heat conduction layer slurry is 2537 mPas.
(4) Coupling and activating the wave-absorbing layer: preparing an activating liquid, wherein the coupling agent is a silane coupling agent KH-550, uniformly dispersing the coupling agent in absolute ethyl alcohol solvent, the concentration of the coupling agent is 0.3%, spreading and fixing a completely dried wave-absorbing layer (with a concave-convex structure, the base surface facing upwards) on a base film, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, and naturally drying the layer to be used.
(5) Preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface (a base surface with a concave-convex structure) of the wave-absorbing layer subjected to coupling activation treatment, and drying to obtain a composite unit of the wave-absorbing layer and the heat conduction layer; wherein, the coating process is casting, and the thickness of the casting film of the heat conduction layer is 0.04 mm.
(6) And (5) repeating the steps (1) to (5) to obtain 3 composite units of the wave absorbing layer and the heat conducting layer.
(7) And (3) carrying out hot pressing on the composite units according to the requirement, wherein the hot pressing compression ratio is 50%, and finally obtaining the electromagnetic wave absorption composite sheet material, wherein the total thickness of the material is 0.3 mm.
Comparative example 3 as a comparative example to example 2, except that the wave-absorbing layer thickness T1 was 0.13mm and H was 0.065 mm. The thickness of the single-layer wave absorbing layer casting film is 0.26mm, the height of the PET film bulge is 0.13mm, the thickness of the single-layer heat conduction layer casting film is 0.04mm, finally the two composite units are subjected to hot-press compounding, and finally the thickness of the electromagnetic wave absorbing sheet is 0.3 mm.
Comparative example 4
A comparative example of example 2 is distinguished by a wave-absorbing layer thickness T1 of 0.05mm, a H of 0.025mm and a heat-conducting layer thickness T2 of 0.025 mm. In the preparation process, the thickness of the single-layer wave absorbing layer casting film is 0.1mm, the height of the PET film bulge is 0.05mm, and the thickness of the single-layer heat conducting layer casting film is 0.05 mm. And finally, carrying out hot-press compounding on the 4 compounding units, wherein the thickness of the electromagnetic wave absorption sheet is 0.3 mm.
Comparative example 5
As a comparative example of example 2, except that the heat conductive layer thickness T2 was 0.07mm, the single heat conductive layer casting film thickness was 0.14mm, and finally the two composite units were subjected to thermocompression bonding, and the thickness of the final electromagnetic wave-absorbing sheet was 0.3 mm.
Comparative example 6
As a comparative example of example 2, the differences are that the thickness T2 of the heat conducting layer is 0.01mm, the thickness of the casting film of the single heat conducting layer is 0.02mm, the thickness T1 of the wave absorbing layer is 0.09mm, H is 0.045mm, the thickness of the casting film of the single wave absorbing layer is 0.18mm, the height of the projection of the PET film is 0.09mm, and finally, the three composite units are subjected to hot press composite, and the thickness of the final electromagnetic wave absorbing sheet is 0.3 mm.
Comparative example 7
A comparative example, example 2, except that H was 0.25 times T1, i.e. H was 0.02 mm; the height of the PET film protrusion is 0.04 mm.
Comparative example 8
A comparative example, example 2, except that H was 0.75 times T1, i.e. H was 0.06 mm; the height of the PET film protrusion is 0.12 mm.
Comparative example 9
A comparative example to example 2, except that L2 was 4 mm.
Comparative example 10
A comparative example to example 2, except that L2 was 11 mm.
Comparative example 11
A comparative example to example 2, except that L1 was 0.5 mm.
Comparative example 12
A comparative example to example 2, except that L1 was 3.5 mm.
The materials of example 2 and comparative examples 3 to 12 were tested for shielding performance, wave-absorbing performance (reflection loss), thermal conductivity and density, respectively, and the test results are shown in table 2.
Table 2 test results of materials prepared in example 2 and comparative examples 3 to 12
Figure BDA0002495861150000121
Figure BDA0002495861150000131
Wherein, the wave absorbing layer of the material obtained in comparative example 8 is easy to break, and the grooves of the material obtained in comparative example 11 are provided with air holes.
The experimental results in table 2 show that the structural dimensions T1, T2, H, L2 and L1 in the electromagnetic wave absorbing composite sheet material are all limited in a certain range, otherwise, the electromagnetic wave absorbing composite sheet material cannot achieve good electromagnetic wave absorbing/shielding and heat conducting properties at the same time, and H is too large, which causes the wave-absorbing layer to be easily broken in the film-forming process after being dried, and is difficult to form, while L1 is too small, which causes the heat-conducting slurry in the groove to be organically combined with the wave-absorbing layer due to the capillary phenomenon, and a large amount of air holes are found through the observation of a scanning electron microscope.
Example 3
The electromagnetic wave absorption composite sheet is of a structure formed by alternately laminating a plurality of wave absorption layers and heat conduction layers, the number of the wave absorption layers and the number of the heat conduction layers are determined according to the requirement of actually required thickness, and the wave absorption layers and the heat conduction layers are of irregular structures with periodic uneven cross sections. In order to obtain higher electromagnetic wave absorption/shielding performance and heat conduction performance, strict requirements are made on the material composition and the key size of the wave absorbing layer and the heat conduction layer.
(1) The wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 15 percent of
Scaly soft magnetic alloy magnetic powder: 85 percent of
The high-molecular binder is polyurethane;
the scaly iron-based alloy magnetic powder is Fe-Si-Al magnetic powder, the average thickness of the scaly iron-based alloy magnetic powder is 0.95 mu m, and the diameter-thickness ratio (the size in the diameter direction and the size in the thickness direction) is more than 87: 1.
the thickness T1 of the wave-absorbing layer is 0.08mm, and the height H of the groove is 0.5 times of the thickness T1 of the wave-absorbing layer, namely 0.04 mm.
The L2 dimension was 6.5mm and the groove width dimension L1 was 1.5 mm.
(2) The heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 34 percent of
A heat-conducting medium: 66 percent
The binder is polyurethane;
the heat-conducting medium is a graphite microchip;
the thickness T2 of the heat conduction layer is 0.02 mm.
The preparation method of the electromagnetic wave absorption composite sheet comprises the following steps:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent and scaly magnetic powder, and performing vacuum defoaming treatment on the slurry to obtain uniform wave-absorbing layer slurry suitable for casting; wherein the solvent is absolute ethyl alcohol.
(2) Preparing a wave-absorbing layer: coating the uniformly mixed slurry on a PET film, drying the casting film, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave-absorbing layer unit; wherein the thickness of the casting film of the wave-absorbing layer is 0.16 mm.
The surface of the PET film is of a rugged structure, the height of the bulges is 0.08mm, and in order to facilitate the wave-absorbing layer to form the film, the surface of the PET film needs to be coated with silicone oil.
(3) Preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent and a high-molecular binder, and then defoaming the slurry to obtain uniformly-mixed heat-conducting layer slurry with certain viscosity; wherein the solvent is absolute ethyl alcohol, and the viscosity of the heat conduction layer slurry is 2806 mPas.
(4) Coupling and activating the wave-absorbing layer: preparing an activating liquid, wherein the coupling agent is a silane coupling agent KH-550, uniformly dispersing the coupling agent in a solvent (absolute ethyl alcohol), the concentration of the coupling agent is 0.25%, spreading and fixing a completely dried wave-absorbing layer (with a concave-convex structure and a base surface upward) on a base film, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, and naturally drying the layer for later use, wherein the thickness of the coupling agent layer is less than 1 mu m.
(5) Preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface (a base surface with a concave-convex structure) of the wave-absorbing layer subjected to coupling activation treatment, and drying to obtain a composite unit of the wave-absorbing layer and the heat conduction layer; wherein, the coating process is casting, and the thickness of the casting film of the heat conduction layer is 0.04 mm.
(6) And (5) repeating the steps (1) to (5) to obtain 3 composite units of the wave absorbing layer and the heat conducting layer.
(7) And (3) carrying out hot pressing on the composite units, wherein the hot pressing compression ratio is 50%, and finally obtaining the electromagnetic wave absorption composite sheet material with the total thickness of 0.3 mm.
Comparative example 13
As a comparative example of example 3, there is a difference in that the proportion of the binder (polyurethane) is 53% and the proportion of the heat transfer medium (graphite micro-sheets) is 47%.
Comparative example 14
A comparative example of example 3 is different in that the binder (polyurethane) is 18% and the heat transfer medium (graphite micro-sheets) is 82%.
Comparative example 15
As a comparative example of example 3, except that the viscosity of the thermally conductive paste was controlled by controlling the vacuum defoamation time, the final viscosity was 1931 mPas.
Comparative example 16
As a comparative example of example 3, except that the viscosity of the thermally conductive paste was controlled by controlling the vacuum defoamation time, the final viscosity was 3645 mPas.
The materials of example 3 and comparative examples 13 to 16 were tested for shielding performance, wave-absorbing performance (reflection loss), thermal conductivity and density, and the interface junction between the heat-conducting layer and the wave-absorbing layer was characterized by a scanning electron microscope, with the test results shown in table 3.
Table 3 test results of materials prepared in example 3 and comparative examples 13 to 16
Figure BDA0002495861150000161
As can be seen from the experimental results in table 3, the filling ratio of the heat conducting medium in the heat conducting layer and the viscosity of the slurry in the preparation process of the heat conducting layer are limited to some extent, otherwise, the heat conducting property and the electromagnetic wave absorption/shielding property cannot be obtained at the same time.
Example 4
The electromagnetic wave absorption composite sheet is of a structure formed by alternately laminating a plurality of wave absorption layers and heat conduction layers, the number of the wave absorption layers and the number of the heat conduction layers are determined according to the requirement of actually required thickness, and the wave absorption layers and the heat conduction layers are of irregular structures with periodic uneven cross sections. In order to obtain higher electromagnetic wave absorption/shielding performance and heat conduction performance, strict requirements are made on the material composition and the key size of the wave absorbing layer and the heat conduction layer.
(1) The wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 13 percent of
Scaly soft magnetic alloy magnetic powder: 87 percent of
The high-molecular binder is polyurethane;
the scaly iron-based alloy magnetic powder is Fe-Si-Al magnetic powder, the average thickness of the scaly iron-based alloy magnetic powder is 0.95 mu m, and the diameter-thickness ratio (the size in the diameter direction and the size in the thickness direction) is more than 87: 1.
the thickness T1 of the wave-absorbing layer is 0.08mm, the height H of the groove is 0.5 times of the thickness T1 of the wave-absorbing layer, namely 0.04mm,
the L2 dimension was 6.5mm and the groove width dimension L1 was 1.5 mm.
(2) The heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 40 percent of
A heat-conducting medium: 60 percent of
The binder is polyurethane;
the heat-conducting medium is a graphite microchip;
the thickness T2 of the heat conduction layer is 0.02 mm.
The preparation method of the electromagnetic wave absorption composite sheet comprises the following steps:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent and scaly magnetic powder, and performing vacuum defoaming treatment on the slurry to obtain uniform wave-absorbing layer slurry suitable for casting; wherein the solvent is absolute ethyl alcohol.
(2) Preparing a wave-absorbing layer: coating the uniformly mixed slurry on a specially designed PET film, drying the casting film, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave absorbing layer unit; wherein the thickness of the casting film of the wave-absorbing layer is 0.16 mm.
The surface of the PET film is of a rugged structure, the height of the convex part is 0.08mm, and silicone oil needs to be coated on the surface of the PET film in order to facilitate the wave-absorbing layer to form the film.
(3) Preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent and a high-molecular binder, and then defoaming the slurry to obtain the uniformly-mixed heat-conducting layer slurry with certain viscosity. The solvent is absolute ethyl alcohol; wherein the heat conducting layer slurry viscosity is 3145 mPas.
(4) Coupling and activating the wave-absorbing layer: preparing an activating liquid, wherein the coupling agent is a silane coupling agent KH-550, uniformly dispersing the coupling agent in a solvent (absolute ethyl alcohol), the concentration of the coupling agent is 0.2%, spreading and fixing a completely dried wave-absorbing layer (with a concave-convex structure and a base surface upward) on a base film, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, and naturally drying the layer for later use, wherein the thickness of the coupling agent layer is less than 1 mu m.
(5) Preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface (a base surface with a concave-convex structure) of the wave-absorbing layer subjected to coupling activation treatment, and drying to obtain a composite unit of the wave-absorbing layer and the heat conduction layer; wherein, the coating process is casting, and the thickness of the casting film of the heat conduction layer is 0.04 mm.
(6) And (5) repeating the steps (1) to (5) to obtain 3 composite units of the wave absorbing layer and the heat conducting layer.
(7) And (3) carrying out hot pressing on the composite units to finally obtain the electromagnetic wave absorption composite sheet material, wherein the total thickness of the material is 0.3 mm.
Comparative example 17
As a comparative example to example 4, except that the wave-absorbing layer was not subjected to a coupling activation treatment.
Comparative example 18
The difference between the comparative example of example 4 and the coupling agent concentration in the coupling activation treatment of the wave-absorbing layer is 0.6%.
Comparative example 19
The difference as a comparative example of example 4 is that when the wave-absorbing layer was subjected to coupling activation treatment, the thickness of the coupling agent layer was 2 μm, and the thickness of the coupling agent layer was measured by a scanning electron microscope.
The materials of example 4 and comparative examples 17 to 19 were tested for shielding performance, wave-absorbing performance (reflection loss), thermal conductivity and density, and the interface junction between the heat-conducting layer and the wave-absorbing layer was characterized by a scanning electron microscope, with the test results shown in table 4.
Table 4 test results of the materials prepared in example 4 and comparative examples 17 to 19
Figure BDA0002495861150000181
Figure BDA0002495861150000191
From the experimental results in table 4, it can be known that the coupling activation treatment of the wave-absorbing layer has an important effect on improving the interface bonding between the heat conducting layer and the wave-absorbing layer, and meanwhile, the coupling agent component in the material is increased due to the excessively high concentration of the coupling agent in the activation liquid and the excessively thick thickness of the coupling agent layer, and the electromagnetic wave absorption/shielding and heat conducting effects of the material are deteriorated. Therefore, the concentration of the coupling agent and the thickness of the coupling agent layer need to be controlled within a certain range.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. The high-heat-conductivity electromagnetic wave absorption composite sheet is characterized in that the electromagnetic wave absorption sheet material is formed by alternately laminating a plurality of wave absorption layers and heat conduction layers, and the wave absorption layers and the heat conduction layers are of special-shaped structures with periodically uneven cross sections;
the wave-absorbing layer comprises the following components in percentage by weight:
high-molecular binder: 10 to 20 percent
Scaly soft magnetic alloy magnetic powder: 80 to 90 percent
Auxiliary materials: less than or equal to 1 percent
The thickness T1 of the wave absorbing layer is 0.06-0.12 mm, the size L2 is 5-10 mm, the L2 is the interval between the protrusions, and the width L1 of the groove is 1-3 mm;
the heat conducting layer comprises the following components in percentage by weight:
high-molecular binder: 20 to 50 percent
A heat-conducting medium: 50 to 80 percent
Auxiliary agent: less than or equal to 2 percent
The thickness T2 of the heat conduction layer is 0.015-0.035 mm;
coupling and activating the wave-absorbing layer: preparing an activating liquid, uniformly dispersing a coupling agent in a solvent, wherein the concentration of the coupling agent is not more than 0.5%, spreading and fixing a completely dried wave-absorbing layer on a base film, wherein a base surface with a concave-convex structure faces upwards, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, wherein the thickness of the coupling agent layer is less than 1 mu m, and naturally drying for later use;
the groove height H of the wave-absorbing layer is 0.45-0.55 times of the thickness T1 of the wave-absorbing layer.
2. The high thermal conductivity electromagnetic wave absorption composite sheet according to claim 1, wherein the polymeric binder in the wave-absorbing layer is selected from polyurethane, acrylic resin, epoxy resin, liquid nitrile rubber, ethyl cellulose or PVB.
3. The high-thermal-conductivity electromagnetic wave absorption composite sheet as claimed in claim 1, wherein the scaly iron-based alloy magnetic powder in the wave-absorbing layer is selected from one or more of Fe-Si, Fe-Si-Al, Fe-Si-Cr, Fe-Si-Al-Cr, Fe-Ni-Mo, and Fe-Al, the thickness of the magnetic powder is 0.8 μm to 1.8 μm, and the aspect ratio is greater than 40: 1.
4. the high thermal conductivity electromagnetic wave absorption composite sheet according to claim 1, wherein the auxiliary material is one or more of an anti-settling agent, a coupling agent, a dispersing agent or a toughening agent.
5. The high thermal conductivity electromagnetic wave absorption composite sheet according to claim 1, wherein the thermally conductive polymeric binder is selected from polyurethane, acrylic resin, epoxy resin, liquid nitrile rubber, ethyl cellulose, or PVB.
6. The high thermal conductivity electromagnetic wave absorbing composite sheet according to claim 1, wherein the thermally conductive layer and thermally conductive medium is selected from one or more of graphite and graphene.
7. The high thermal conductivity electromagnetic wave absorption composite sheet according to claim 1, wherein the heat conduction layer assistant is one or more selected from a coupling agent, a dispersing agent, a leveling agent, and an antifoaming agent.
8. The method for preparing a highly thermally conductive electromagnetic wave absorption composite sheet as claimed in any one of claims 1 to 7, wherein the method comprises the steps of:
(1) preparing casting slurry: uniformly mixing a high-molecular binder, a solvent, scaly soft magnetic alloy magnetic powder and auxiliary materials, and then carrying out vacuum defoaming treatment on the slurry to obtain the uniformly-mixed wave-absorbing layer slurry with the viscosity suitable for tape casting;
(2) preparing a wave-absorbing layer: coating the uniformly mixed slurry obtained in the step (1) on a PET film to obtain a casting film, drying, and taking down the casting film from the PET film after the solvent is completely volatilized to obtain a wave absorbing layer unit, wherein the thickness of the casting film is T1; the surface of the PET film is of a rugged structure, and the height of the bulges is H;
(3) preparing heat conduction layer slurry: firstly, uniformly mixing a heat-conducting medium, a solvent, auxiliary materials and a high-molecular binder, and then performing defoaming treatment to obtain heat-conducting layer slurry with the viscosity of 2000-;
(4) coupling and activating the wave-absorbing layer: preparing an activating liquid, uniformly dispersing a coupling agent in a solvent, wherein the concentration of the coupling agent is not more than 0.5%, spreading and fixing a completely dried wave-absorbing layer on a base film, wherein a base surface with a concave-convex structure faces upwards, uniformly spraying the activating liquid on the surface of the wave-absorbing layer, wherein the thickness of the coupling agent layer is less than 1 mu m, and naturally drying for later use;
(5) preparing a heat conduction layer: uniformly coating the heat conduction layer slurry prepared in the step (3) on the surface of the wave-absorbing layer with the concave-convex structure after coupling and activating treatment, and then drying to obtain a composite unit of the wave-absorbing layer and the heat conduction layer;
(6) repeating the steps (1) to (5) to obtain a plurality of composite units of the wave absorbing layer and the heat conducting layer;
(7) and carrying out hot pressing on the plurality of composite units to finally obtain the high-heat-conductivity electromagnetic wave absorption composite sheet.
9. The method for preparing a high thermal conductivity electromagnetic wave absorption composite sheet according to claim 8, wherein the surface of the PET film is coated with silicone oil.
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CN207354807U (en) * 2017-06-01 2018-05-11 宜宾金原复合材料有限公司 Composite electromagnetic wave absorbing film
CN107880798A (en) * 2017-11-29 2018-04-06 横店集团东磁股份有限公司 A kind of heat conduction wave absorbing patch and preparation method thereof
CN109550668A (en) * 2018-10-19 2019-04-02 苏州铂韬新材料科技有限公司 A kind of thermally conductive laminated film and preparation method thereof inhaled wave screen and cover three-in-one function
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