A high thermal conductivity metal soft magnetic composite material, its preparation method and application

Abstract

This invention relates to a high thermal conductivity metal soft magnetic composite material, its preparation method, and its application, belonging to the field of soft magnetic material preparation technology. A thermally conductive sheet-like powder is added to a coupling agent solution to obtain a modified thermally conductive sheet-like powder. Resin and the modified thermally conductive sheet-like powder are added to the metal soft magnetic powder, which is then coated with an insulating layer. A volatile organic solvent is added for mixing and granulation. The metal soft magnetic powder is bridged by the thermally conductive sheet-like powder, and the resin is dispersed in the pores of the system to obtain metal soft magnetic composite particles. After pressing and molding, a metal soft magnetic composite green body is obtained. After curing and annealing the green body, the metal soft magnetic composite material is obtained. This invention establishes a thermally conductive pathway from the metal soft magnetic powder to the outer surface of the soft magnetic composite core, achieving high thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic material preparation technology, and more specifically, to a high thermal conductivity metal soft magnetic composite material, its preparation method and application. Background Technology

[0002] The integral molded inductor is mainly composed of soft magnetic composite material (SMC) and internal coil. Under actual AC and DC superposition working conditions, the internal coil has DC power loss due to DC resistance; the AC current in the winding will cause AC power loss and AC magnetic flux loss in the soft magnetic composite material; the metal soft magnetic particles will generate eddy current loss in the high-frequency alternating magnetic field. All of the above losses will generate a certain amount of heat.

[0003] Given the aforementioned background, the heat dissipation mode used in the field of molded inductors primarily relies on external auxiliary heat dissipation. However, since the heat source is internal and the binder has low thermal conductivity, it cannot quickly dissipate the internally generated heat. As a result, heat accumulates in the molded inductor, leading to a rapid temperature rise. As the device temperature increases, the DC resistance of the device also increases, further increasing the power consumption generated by DC, creating a vicious cycle. Therefore, especially for molded inductors used in high-power, high-frequency, and high-ambient-temperature scenarios, the thermal conductivity of soft magnetic composite materials becomes particularly important.

[0004] Metal soft magnetic composite materials are mainly made by mixing metal soft magnetic particles, insulating coating layers and adhesives, and preparing them in the form of molding. The insulating coating layer can be mainly composed of organic thermosetting resins, inorganic oxides and metal oxides. Although the insulating coating layer can achieve insulation between particles and reduce eddy current losses, it will also introduce some materials with low thermal conductivity, which will increase the thermal resistance of the soft magnetic composite core.

[0005] Adhesives are generally composed of thermosetting organic adhesives such as epoxy resin, silicone resin, and phenolic resin. Organic resins are poor conductors of heat; for example, the thermal conductivity of epoxy resin is 0.17–0.21 W·m. -1 ·K -1 Therefore, using resin as a binder is a key factor in increasing the thermal resistance of soft magnetic composite cores.

[0006] Soft magnetic composite materials also suffer from weak interfacial bonding between the adhesive and the coating layer, which can easily lead to phonon scattering and increased interfacial thermal resistance. Currently, there is little information available on improving the thermal conductivity of soft magnetic composite materials. Summary of the Invention

[0007] This application provides a high thermal conductivity metal soft magnetic composite material and its preparation method. By modifying the surface of high thermal conductivity sheet powder, the interconnection between resin, high thermal conductivity Al2O3 insulating coating layer and high thermal conductivity powder is enhanced, the thermal resistance of the adhesive is reduced, and the interface scattering is reduced. The high thermal conductivity of the metal soft magnetic composite material is achieved, thereby solving the technical problem of low thermal conductivity of soft magnetic composite materials in the prior art from the inside of the material.

[0008] According to a first aspect of the present invention, a method for preparing a soft magnetic metal composite material is provided, comprising the following steps:

[0009] (1) The thermally conductive sheet powder is added to the coupling agent solution to obtain the modified thermally conductive sheet powder; the thermally conductive sheet powder is a nitride, carbide or oxide;

[0010] (2) Add resin and modified thermally conductive sheet powder obtained in step (1) to the metal soft magnetic powder. The metal soft magnetic powder is coated with an insulating layer and then mixed and granulated with volatile organic solvent. The metal soft magnetic powder is bridged by the thermally conductive sheet powder, and the resin is dispersed in the pores of the system to obtain metal soft magnetic composite particles.

[0011] (3) Press the metal soft magnetic composite particles obtained in step (2) into a mold to obtain a metal soft magnetic composite material green blank; heat and solidify the green blank to obtain the metal soft magnetic composite material.

[0012] Preferably, in step (1), the nitride is BN, AlN or Si3N4; the carbide is SiC or diamond; and the oxide is Al2O3, ZnO or BeO.

[0013] Preferably, in step (1), the soft magnetic metal powder is at least one of carbonyl iron powder, Fe-based amorphous alloy powder, Fe-based nanocrystalline powder, FeNiMo alloy powder, FeSi alloy powder, FeSiAl alloy powder, and FeSiCr alloy powder.

[0014] Preferably, the resin is at least one selected from epoxy resin, silicone resin, and phenolic resin.

[0015] Preferably, the insulating layer is Al2O3 or MgO.

[0016] Preferably, the coupling agent is at least one selected from amino coupling agents, mercapto coupling agents, vinyl coupling agents, epoxy coupling agents, cyano coupling agents, and methacryloxysilane coupling agents.

[0017] Preferably, in step (3), the heating temperature is 150℃~700℃.

[0018] Preferably, in step (3), the metal soft magnetic composite particles are pressed into a ring structure.

[0019] According to another aspect of the present invention, a soft magnetic metal composite material prepared by any of the methods described herein is provided.

[0020] According to another aspect of the present invention, the metal soft magnetic composite material is provided for use in inductors or soft magnetic composite cores.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0022] (1) The present invention provides a metal soft magnetic composite material with high thermal conductivity. The present invention modifies the surface of the high thermal conductivity sheet powder so that it can be better compatible with the resin binder, reduces phonon scattering between the thermally conductive particles and the resin components, and increases the thermal conductivity of the soft magnetic composite material.

[0023] (2) The insulating coating layer of this invention preferably uses Al2O3 (38-42 W·m) with high thermal conductivity. -1 ·K -1 A thermally conductive pathway was established from the metal soft magnetic powder to the outer surface of the soft magnetic composite core using thermally conductive sheet-like powder as a thermally conductive network, thus realizing its thermal conductivity characteristics. Composite materials generally cannot achieve the inherent thermal conductivity of thermally conductive fillers (sheet-like powders) because heat is generally transferred along the sheet-like thermally conductive powders, which have higher thermal conductivity. However, the organic resin used as a binder slows down this process. Therefore, it is necessary to fill the resin with fillers of specific shapes, sizes, and aspect ratios to achieve interconnection between sheet-like powders while ensuring the lowest possible filler content, thereby realizing a thermally conductive pathway. In other words, a network-like pathway for rapid heat flow is constructed with a low filler content. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the high thermal conductivity metal soft magnetic composite material structure of the present invention.

[0025] Figure 2 This is an EDS image of the alumina coating layer on the surface of the metal magnetic powder of the present invention.

[0026] Figure 3 This is a SEM image of the BN flake powder used in this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] This invention discloses a method for preparing a soft magnetic metal composite material, comprising the following steps:

[0029] (1) The high thermal conductivity sheet powder is placed in a diluted coupling agent solution and stirred and sonicated to obtain the modified high thermal conductivity sheet powder;

[0030] (2) A certain amount of resin is added to the metal soft magnetic powder, the modified high thermal conductivity sheet powder is mixed with volatile organic solvent and granulated, dried and sieved to obtain metal soft magnetic composite particles.

[0031] (3) The above-mentioned soft magnetic composite particles are pressed into shape by molding process to obtain a soft magnetic composite material green blank;

[0032] (4) The above green blank is placed in an atmosphere and cured under high temperature conditions to obtain a high thermal conductivity soft magnetic composite material.

[0033] Preferably, the high thermal conductivity sheet powder in step (1) is at least one of BN, AlN, Si3N4, SiC, Al2O3, ZnO, and BeO.

[0034] Preferably, the ratio of the diameter (average of the major and minor axes) to the thickness of the high thermal conductivity sheet powder described in step (1) should be between 10 and 2000.

[0035] Preferably, the coupling agent in step (1) is at least one of amino, mercapto, vinyl, epoxy, cyano, and methacryloyloxysilane coupling agents.

[0036] Preferably, the coupling agent solution in step (1) is a mixed solution of ethanol and H2O, wherein the weight ratio of H2O to coupling agent is between 5% and 40%, the volume ratio of coupling agent to ethanol is between 50% and 400%, and the ultrasonic stirring time is between 2 and 24 hours.

[0037] Preferably, the soft magnetic metal powder mentioned in step (2) is coated with Al2O3, and its preparation process adopts the commonly used sol-gel method or gas phase method, with a thickness of 1-100 nm. The soft magnetic metal powder is composed of at least one of carbonyl iron powder, Fe-based amorphous alloy powder, Fe-based nanocrystalline powder, FeNiMo alloy powder, FeSi alloy powder, FeSiAl alloy powder, and FeSiCr alloy powder.

[0038] Preferably, the volume ratio of the modified high thermal conductivity sheet powder to the resin in step (2) is between 30% and 70%.

[0039] Preferably, the resin mentioned in step (2) is at least one of epoxy resin, silicone resin, and phenolic resin, wherein the weight ratio of the resin to the soft magnetic metal powder should be between 0.5% and 12%.

[0040] Preferably, the volatile organic solvent mentioned in step (2) is at least one of acetone, ethyl acetate, and toluene.

[0041] Preferably, the drying temperature in step (2) should be between 40°C and 200°C.

[0042] Preferably, the sieving process in step (2) refers to sieving the metal soft magnetic composite powder using a sieve between 40 mesh and 400 mesh.

[0043] Preferably, the molding pressure in step (3) is between 300 MPa and 2000 MPa, and the holding time is between 30 and 300 seconds.

[0044] Preferably, the atmosphere described in step (4) is at least one of air, nitrogen, argon, and helium, wherein the purity of nitrogen, argon, and helium is 99.99%.

[0045] Preferably, the high temperature condition described in step (4) is 150 to 700°C.

[0046] A schematic diagram of the high thermal conductivity metal soft magnetic composite material structure of this invention is attached. Figure 1 As shown, this embodiment provides a metal magnetic powder core 1, which includes metal soft magnetic particles 2, an insulating coating layer 3, sheet-like thermally conductive powder 4, and an organic resin binder 5. This structure disperses a certain amount of sheet-like thermally conductive powder 4 in the organic resin binder 5 and forms bridging interconnects to create a thermally conductive network. The metal soft magnetic particles 2, coated with the insulating coating layer 3, are dispersed within the thermally conductive network, forming a soft magnetic composite material with a network thermally conductive structure.

[0047] Example 1

[0048] This embodiment provides a method for manufacturing the above-mentioned metal magnetic powder core, which includes the following steps:

[0049] (1) Weigh 100g of soft magnetic metal powder with D50 = 40μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 10nm by gas phase method or liquid phase method.

[0050] (2) Place 200mg of silane coupling agent in 190ml of ethanol and 10ml of water, add 20g of BN flake powder, stir ultrasonically for 6 hours, filter and dry to obtain modified BN powder.

[0051] (3) Add 1g of epoxy resin, 2.16g of BN flake powder with a diameter-to-thickness ratio of 1000 (the volume ratio of boron nitride to epoxy resin is 50%), and 20ml of ethyl acetate to the above-mentioned soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40-mesh and 200-mesh sieves to obtain soft magnetic composite powder with a particle size range of 40-mesh to 200-mesh.

[0052] (4) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0053] (5) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0054] Example 2

[0055] This embodiment provides a method for manufacturing the above-mentioned metal magnetic powder core, which includes the following steps:

[0056] (1) Weigh 100g of soft magnetic metal powder with D50 = 40μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 20nm by gas phase method or liquid phase method.

[0057] (2) Place 200mg of silane coupling agent in 190ml of ethanol and 10ml of water, add 20g of BN flake powder, stir ultrasonically for 6 hours, filter and dry to obtain modified BN powder.

[0058] (3) Add 1g of epoxy resin, 2.16g of BN flake powder with a diameter-to-thickness ratio of 1000 (the volume ratio of boron nitride to epoxy resin is 50%), and 20ml of ethyl acetate to the above-mentioned soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40-mesh and 200-mesh sieves to obtain soft magnetic composite powder with a particle size range of 40-mesh to 200-mesh.

[0059] (4) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0060] (5) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0061] Example 3

[0062] This embodiment provides a method for manufacturing the above-mentioned metal magnetic powder core, which includes the following steps:

[0063] (1) Weigh 100g of soft magnetic metal powder with D50 = 40μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 20nm by gas phase method or liquid phase method.

[0064] (2) Place 200mg of silane coupling agent in 190ml of ethanol and 10ml of water, add 20g of BN flake powder, stir ultrasonically for 6 hours, filter and dry to obtain modified BN powder.

[0065] (3) Add 1.2g of epoxy resin, 2.57g of BN flake powder with a diameter-to-thickness ratio of 1000 (the volume ratio of boron nitride to epoxy resin is 40%), and 20ml of ethyl acetate to the above-mentioned soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40-mesh and 200-mesh sieves to obtain soft magnetic composite powder with a particle size range of 40-mesh to 200-mesh.

[0066] (4) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0067] (5) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0068] Example 4

[0069] This embodiment provides a method for manufacturing the above-mentioned metal magnetic powder core, which includes the following steps:

[0070] (1) Weigh 100g of soft magnetic metal powder with D50 = 40μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 20nm by gas phase method or liquid phase method.

[0071] (2) Place 200mg of silane coupling agent in 190ml of ethanol and 10ml of water, add 20g of BN flake powder, stir ultrasonically for 6 hours, filter and dry to obtain modified BN powder.

[0072] (3) Add 0.8g of epoxy resin, 2.57g of BN flake powder with a diameter-to-thickness ratio of 1000 (the volume ratio of boron nitride to epoxy resin is 60%), and 20ml of ethyl acetate to the above-mentioned soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40-mesh and 200-mesh sieves to obtain soft magnetic composite powder with a particle size range of 40-mesh to 200-mesh.

[0073] (4) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0074] (5) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0075] Example 5

[0076] This embodiment provides a method for manufacturing the above-mentioned metal magnetic powder core, which includes the following steps:

[0077] (1) Weigh 100g of soft magnetic metal powder with D50 = 20μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 20nm by gas phase method or liquid phase method.

[0078] (2) Place 200mg of silane coupling agent in 190ml of ethanol and 10ml of water, add 20g of BN flake powder, stir ultrasonically for 6 hours, filter and dry to obtain modified BN powder.

[0079] (3) Add 0.8g of epoxy resin, 2.57g of BN flake powder with a diameter-to-thickness ratio of 1000 (the volume ratio of boron nitride to epoxy resin is 60%), and 20ml of ethyl acetate to the above-mentioned soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40-mesh and 200-mesh sieves to obtain soft magnetic composite powder with a particle size range of 40-mesh to 200-mesh.

[0080] (4) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0081] (5) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0082] Comparative Example 1

[0083] (1) Weigh 100g of soft magnetic metal powder with D50 = 20μm and prepare an Al2O3 insulating coating layer with an insulation thickness of 20nm by gas phase method or liquid phase method.

[0084] (2) Add 2g of epoxy resin and 20ml of ethyl acetate to the above soft magnetic metal powder and mix and granulate. After the organic solvent has completely evaporated, pass through 40 mesh and 200 mesh sieves to obtain soft magnetic composite powder with a particle size range of 40 mesh to 200 mesh.

[0085] (3) Place the above granulated powder in a mold, adjust the equipment pressure to 1800 MPa, and press to obtain soft magnetic composite magnetic powder core.

[0086] (4) The molded inductor is annealed in argon at 550°C for 1 hour to obtain the high thermal conductivity soft magnetic composite material required above.

[0087] like Figure 1The diagram shows a schematic representation of the structure of the present invention. The sheet-like thermally conductive powder 4 is uniformly distributed within the organic resin binder 5 and bridged to form a thermally conductive network. This network surrounds the soft magnetic metal particles 2 coated with an insulating layer 3, forming a network-like thermally conductive soft magnetic composite material. Figure 2 As shown, the soft magnetic particles are uniformly coated with a layer of Al2O3 insulating coating. The sheet-like thermally conductive powder used in this invention is as follows... Figure 3 As shown.

[0088] According to the equivalent medium formula The thermal conductivity of soft magnetic composite materials can be calculated, where λ c λ1 is the thermal conductivity of the composite material, λ2 is the thermal conductivity of the resin matrix, V is the volume fraction of the magnetic powder filler, and k is the thermal conductivity of the magnetic powder. R The value represents the thermal resistance factor. Calculations show that the soft magnetic composite material prepared using this method has the beneficial effect of improving thermal conductivity.

[0089] Table 1. Calculation results of thermal conductivity for the examples and comparative examples.

[0090] sample <![CDATA[Calculate the thermal conductivity k e (W·m -1 ·K -1 )]]> Example 1 9.2 Example 2 9.3 Example 3 8.1 Example 4 10.7 Example 5 9.6 Comparative Example 1 7.6

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of producing a metal soft magnetic composite material, characterized by, Includes the following steps: (1) The thermally conductive sheet powder is added to the coupling agent solution to obtain the modified thermally conductive sheet powder; the thermally conductive sheet powder is a nitride, carbide or oxide; the diameter to thickness ratio of the thermally conductive sheet powder is between 10 and 2000, and the diameter is the average of the major axis and the minor axis; The nitride is BN, AlN, or Si3N4; the carbide is SiC or diamond; the oxide is Al2O3, ZnO, or BeO; and the coupling agent is at least one of amino coupling agents, mercapto coupling agents, vinyl coupling agents, epoxy coupling agents, cyano coupling agents, and methacryloxysilane coupling agents. (2) Add resin and the modified thermally conductive sheet powder obtained in step (1) to the metal soft magnetic powder. The metal soft magnetic powder is coated with an insulating layer by a gas phase method. The insulating layer is Al2O3 and the thickness of the insulating layer is 10~20 nm. Then add volatile organic solvent to mix and granulate. The metal soft magnetic powder is bridged by the thermally conductive sheet powder. The resin is dispersed in the pores of the system to obtain metal soft magnetic composite particles. The resin is at least one of epoxy resin, silicone resin and phenolic resin; (3) Press the metal soft magnetic composite particles obtained in step (2) into a molding material with a molding pressure between 1800 MPa and 2000 MPa to obtain a metal soft magnetic composite material green body; heat and cure the green body at a temperature of 550℃ to 700℃ to obtain the metal soft magnetic composite material; enhance the interconnection between the resin, the high thermal conductivity Al2O3 insulating coating layer and the thermally conductive sheet powder by modifying the surface of the thermally conductive sheet powder, reduce the thermal resistance of the adhesive, and reduce interface scattering. Achieve high thermal conductivity in soft magnetic metal composite materials.

2. The method of producing a metal soft magnetic composite material according to claim 1, wherein In step (1), the soft magnetic metal powder is at least one of carbonyl iron powder, FeNiMo alloy powder, FeSi alloy powder, FeSiAl alloy powder and FeSiCr alloy powder.

3. The method of producing a metal soft magnetic composite material according to claim 1, wherein In step (3), the metal soft magnetic composite particles are pressed into a ring structure.

4. The soft magnetic metal composite material prepared by the method according to any one of claims 1-3.

5. The application of the metal soft magnetic composite material as described in claim 4 in inductors.

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