High-frequency low-loss magnetic powder core and preparation method thereof

Abstract

The invention belongs to the technical field of soft magnetic materials, and discloses a high-frequency low-loss magnetic powder core and a preparation method thereof. The method comprises the following preparation steps that (1) iron alloy soft magnetic powder with the particle size being 5-50 microns is subjected to insulation coating treatment, and insulation-coated iron alloy soft magnetic powder is obtained; and (2) uniformly mixing the insulated and coated iron alloy soft magnetic powder obtained in the step (1) with ferrite powder with the particle size of less than 5 microns and a binder, then injecting the mixture into a mold for compression molding, and then heating to 600-900 DEG C for annealing treatment to obtain the high-frequency low-loss magnetic powder core. The magnetic powder core is prepared by mixing and compounding the large-particle-size iron alloy soft magnetic powder and the small-particle-size ferrite powder, the insulating property of the magnetic powder core can be remarkably improved so that the high-frequency loss of the magnetic powder core can be reduced, and the forming density of the magnetic powder core can be improved so that the adverse effect on the inductance value can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of soft magnetic materials, and in particular relates to a high-frequency low-loss magnetic powder core and a preparation method thereof. Background Art

[0002] Ferroalloy soft magnetic materials have high magnetic permeability and low coercivity, and are widely used in radio electronics industry, precision instruments, remote control and automatic control systems. According to their composition, ferroalloy soft magnetic materials mainly include iron-nickel (FeNi) soft magnetic alloy, iron-silicon (FeSi) soft magnetic alloy and iron-silicon-aluminum (FeSiAl) soft magnetic alloy. With the improvement of electronic technology, the requirements for magnetic devices are getting higher and higher, mainly developing in the direction of miniaturization and high frequency, and higher requirements are put forward for magnetic loss and temperature rise performance. Due to its high conductivity, ferroalloy soft magnetic materials have high eddy current losses at high frequencies, and their applications are limited. Therefore, it is generally necessary to insulate and coat ferroalloy soft magnetic materials.

[0003] Ferrite soft magnetic materials are ferromagnetic oxides with Fe2O3 as the main component, mainly including manganese zinc (MnZn) ferrite, copper zinc (CuZn) ferrite, nickel zinc (NiZn) ferrite, etc. Compared with iron alloys, ferrite soft magnetic materials have the characteristics of high resistance and high insulation, but relatively low magnetic permeability. Therefore, it is expected that the insulation performance of iron alloy magnetic powder cores can be further improved by compounding with appropriate ferrite content to reduce its high-frequency loss, while minimizing the impact on magnetic permeability and inductance.

[0004] The patent document with publication number CN 111316385 A discloses a powder magnetic core that can significantly reduce iron loss. y Fe 3-y The spinel ferrite grain boundary layer represented by O4 is coated on the soft magnetic particles containing pure iron or iron alloy. The pressed powder magnetic core after annealing exhibits high specific resistance due to the grain boundary layer with compound layer, and can reduce eddy current loss and hysteresis loss. However, it is necessary to spray ferrite generation liquid (reaction liquid) on the surface of the powder coated with silicone resin layer to prepare a composite phase coating layer. The corresponding coating process is relatively complicated, and the coating treatment with ferrite layer has a great influence on the magnetic permeability and inductance value. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing a high-frequency and low-loss magnetic powder core.

[0006] Another object of the present invention is to provide a high-frequency low-loss magnetic powder core prepared by the above method.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a high-frequency low-loss magnetic powder core comprises the following preparation steps:

[0009] (1) subjecting an iron alloy soft magnetic powder having a particle size of 5 to 50 μm to an insulation coating treatment to obtain an insulation coated iron alloy soft magnetic powder;

[0010] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is evenly mixed with ferrite powder with a particle size of less than 5 μm and a binder, and then injected into a mold for compression molding, and then heated to 600-900° C. for annealing to obtain a high-frequency low-loss magnetic powder core.

[0011] Furthermore, the iron alloy soft magnetic powder in step (1) is iron nickel (FeNi) soft magnetic alloy powder, iron silicon (FeSi) soft magnetic alloy powder or iron silicon aluminum (FeSiAl) soft magnetic alloy powder, which are commonly used iron alloy soft magnetic powder materials in the art.

[0012] Furthermore, the insulation coating treatment in step (1) refers to the insulation coating treatment using silicon dioxide or the insulation coating treatment using silicon dioxide-aluminum phosphate composite. Preferably, the insulation coating treatment is performed using silicon dioxide-aluminum phosphate composite.

[0013] Furthermore, the method for insulating and coating the silicon dioxide-aluminum phosphate composite is as follows:

[0014] 1) adding phytic acid to an alcohol aqueous solution to dissolve it, then adding an aluminum alkoxide solution to mix and react to obtain a phytic acid aluminum sol, and then mixing the phytic acid aluminum sol with a silica sol to obtain an insulating coating solution;

[0015] 2) The ferroalloy soft magnetic powder is evenly mixed with the insulating coating liquid of step 1), first dried at 60-100° C. to remove the solvent, and then heated to 300-800° C. for heat treatment to obtain ferroalloy soft magnetic powder with a silicon dioxide-aluminum phosphate composite insulation coating.

[0016] Preferably, the alcohol aqueous solution in step 1) is an ethanol aqueous solution with an ethanol volume percentage of 80-95%; the aluminum alkoxide solution is triethanol aluminum solution, propoxide aluminum solution, isopropoxide aluminum solution or n-butoxide aluminum solution; the amount of the aluminum alkoxide solution added is such that the pH value of the reaction system is 5-7.

[0017] Preferably, the amount of silica sol added in step 1) is 20-60% of the mass of phytic acid in terms of silicon dioxide content.

[0018] Preferably, the amount of the insulating coating liquid added in step 2) is 0.2-2% of the mass of the ferroalloy soft magnetic powder in terms of solid content.

[0019] Preferably, the drying and removing of the solvent in step 2) is carried out under vacuum conditions; the heat treatment is carried out under nitrogen protection conditions, and the heat treatment time is 3 to 10 hours.

[0020] Furthermore, the ferrite powder in step (2) is manganese zinc (MnZn) ferrite, copper zinc (CuZn) ferrite or nickel zinc (NiZn) ferrite powder; the amount of ferrite powder added is 5% to 20% of the mass of the insulating coated iron alloy soft magnetic powder. Within the above ferrite powder content range, the high-frequency loss performance of the magnetic powder core is significantly improved, and the effect on the inductance value is small. The above ferrite powder is a ferrite soft magnetic powder material commonly used in the art.

[0021] Furthermore, the binder in step (2) is an epoxy resin binder or a silicone resin binder; the amount of the binder added is 0.2 to 1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder, calculated by its solid content.

[0022] Furthermore, in step (2), the temperature of the press molding is 60-100° C., and the pressure is 500-800 MPa; and the time of the annealing treatment is 15-120 min.

[0023] A high-frequency and low-loss magnetic powder core is prepared by the method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The magnetic powder core of the present invention is prepared by mixing and compounding large-particle iron alloy soft magnetic powder and small-particle ferrite powder, which can significantly improve the insulation performance of the magnetic powder core to reduce its high-frequency loss and increase its molding density to reduce the adverse effect on the inductance value.

[0026] (2) The present invention further uses a silicon dioxide-aluminum phosphate composite to perform insulation coating treatment on the ferroalloy soft magnetic powder, which can significantly improve the insulation coating effect and the bonding molding effect, thereby further reducing high-frequency losses and increasing the inductance value. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] A method for preparing a high-frequency low-loss magnetic powder core comprises the following preparation steps:

[0030] (1) Sendust soft magnetic powder with an average particle size of 10 μm and silica sol with a solid content of 20% are stirred and mixed uniformly, and the amount of silica sol added is 0.5% of the mass of the sendust soft magnetic powder in terms of its solid content. The mixture is first dried in vacuum at 80°C to remove the solvent, and then heated to 500°C under nitrogen protection for heat treatment for 5 hours to obtain an iron alloy soft magnetic powder treated with silica insulation coating.

[0031] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is evenly mixed with manganese zinc ferrite powder with an average particle size of 2 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the epoxy resin content is 0.5% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder, and then injected into a mold, pressed at a pressure of 600 MPa and a temperature of 80° C., and then heated to 800° C. under nitrogen protection for annealing for 60 minutes to obtain a high-frequency low-loss magnetic powder core.

[0032] In this embodiment, the addition amount of manganese-zinc ferrite powder is adjusted to 0%, 5%, 10%, 15%, 20%, and 25% of the mass of the insulating coated iron alloy soft magnetic powder, and the test results of density, inductance value and high-frequency loss (1MHz / 50mT) of the obtained magnetic powder core are shown in Table 1 below.

[0033] Table 1

[0034] Ferrite addition amount, % <![CDATA[Density, g / cm 3 > Inductance, μH <![CDATA[Loss, kW / m 3 > 0％ 5.675 12.87 2154 5％ 5.712 13.22 1952 10％ 5.830 13.25 1545 15％ 5.857 12.86 1327 20％ 5.863 11.73 1205 25％ 5.862 10.14 1136

[0035] It can be seen from the results in Table 1 that the density of the magnetic powder core shows an increasing trend with the increase of the content of small-particle ferrite powder. The reason is that the small-particle ferrite powder can fill the gaps between the large-particle sendust soft magnetic powder and improve the molding density. The loss of the magnetic powder core shows a decreasing trend with the increase of the ferrite powder content, indicating that the high-frequency loss of the iron alloy soft magnetic powder core can be effectively reduced by the compounding of ferrite powder. The inductance value of the magnetic powder core shows a trend of first increasing and then decreasing with the increase of the ferrite powder content. The reason is that the magnetic permeability of ferrite is low, so its addition will have an adverse effect on the inductance value of the magnetic powder core, but the appropriate content of small-particle ferrite powder can increase the molding density of the magnetic core, so it can reduce the adverse effect on the inductance value. When the amount of ferrite powder added is in the range of 5% to 20% of the mass of the insulating coated iron alloy soft magnetic powder, the obtained magnetic powder core has good comprehensive magnetic properties.

[0036] Example 2

[0037] A method for preparing a high-frequency low-loss magnetic powder core comprises the following preparation steps:

[0038] (1) Stir and mix the iron-silicon soft magnetic powder with an average particle size of 20 μm and the silica sol with a solid content of 20% to uniformly, wherein the amount of the silica sol added is 1% of the mass of the iron-silicon soft magnetic powder in terms of its solid content, and first vacuum dry the mixture at 80°C to remove the solvent, and then heat treat the mixture at 600°C under nitrogen protection for 6 hours to obtain an iron alloy soft magnetic powder with a silicon dioxide insulation coating.

[0039] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is uniformly mixed with copper-zinc ferrite powder with an average particle size of 4 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the amount of copper-zinc ferrite powder added is 10% of the mass of the insulating coated iron alloy soft magnetic powder, and the content of epoxy resin is 0.8% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder. The mixture is then injected into a mold, pressed at a pressure of 700 MPa and a temperature of 80° C., and then heated to 750° C. under nitrogen protection for annealing for 60 min to obtain a high-frequency low-loss magnetic powder core.

[0040] Example 3

[0041] A method for preparing a high-frequency low-loss magnetic powder core comprises the following preparation steps:

[0042] (1) An iron-nickel soft magnetic powder having an average particle size of 5 μm and a silica sol having a solid content of 20% are stirred and mixed uniformly, wherein the amount of silica sol added is 2% of the mass of the iron-nickel soft magnetic powder in terms of its solid content. The powder is first dried in vacuum at 80° C. to remove the solvent, and then heated to 700° C. under nitrogen protection for heat treatment for 8 h to obtain an iron alloy soft magnetic powder treated with silica insulation coating.

[0043] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is uniformly mixed with nickel zinc ferrite powder with an average particle size of 1 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the amount of nickel zinc ferrite powder added is 10% of the mass of the insulating coated iron alloy soft magnetic powder, and the content of epoxy resin is 1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder. The mixture is then injected into a mold, pressed at a pressure of 800 MPa and a temperature of 80° C., and then heated to 800° C. under nitrogen protection for annealing for 60 min to obtain a high-frequency low-loss magnetic powder core.

[0044] Example 4

[0045] A method for preparing a high-frequency low-loss magnetic powder core, compared with Example 1, using the insulating coating liquid prepared by the following method to replace silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0046] Phytic acid is added to an ethanol aqueous solution with an ethanol volume percentage of 85% to dissolve, and then an ethanol solution of aluminum isopropoxide is added for mixed reaction, and the pH value of the reaction system is controlled to be 6 by controlling the amount of aluminum isopropoxide added to obtain phytic acid aluminum sol. Then, it is evenly mixed with silica sol, and the amount of silica sol added is 40% of the mass of phytic acid in terms of silicon dioxide content, to obtain an insulating coating solution with a solid content of 20%.

[0047] In this embodiment, the density of the obtained magnetic powder core is 5.915 g / cm2 under the condition that the addition amount of manganese zinc ferrite powder is 10% of the mass of the insulating coated iron alloy soft magnetic powder. 3 , the inductance is 17.25μH and the loss is 854kW / m 3 .

[0048] Example 5

[0049] A method for preparing a high-frequency low-loss magnetic powder core, compared with Example 1, using the insulating coating liquid prepared by the following method to replace silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0050] Phytic acid is added to an ethanol aqueous solution with an ethanol volume percentage of 90% to dissolve, and then an ethanol solution of aluminum triethoxide is added for mixed reaction, and the pH value of the reaction system is controlled to be 5 by controlling the amount of aluminum triethoxide added to obtain phytic acid aluminum sol. Then, it is evenly mixed with silica sol, and the amount of silica sol added is 20% of the mass of phytic acid in terms of silicon dioxide content, to obtain an insulating coating solution with a solid content of 20%.

[0051] In this embodiment, the density of the obtained magnetic powder core is 5.918 g / cm 3 , the inductance is 17.31μH and the loss is 870kW / m 3 .

[0052] Example 6

[0053] A method for preparing a high-frequency low-loss magnetic powder core, compared with Example 1, using the insulating coating liquid prepared by the following method to replace silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0054] Phytic acid is added to an ethanol aqueous solution with an ethanol volume percentage of 95% to dissolve, and then an ethanol solution of aluminum isopropoxide is added for mixed reaction, and the pH value of the reaction system is controlled to be 7 by controlling the amount of aluminum isopropoxide added to obtain phytic acid aluminum sol. Then, it is evenly mixed with silica sol, and the amount of silica sol added is 60% of the mass of phytic acid in terms of silicon dioxide content, to obtain an insulating coating solution with a solid content of 20%.

[0055] In this embodiment, the density of the obtained magnetic powder core is 5.909 g / cm 3 , the inductance is 16.96μH and the loss is 855kW / m 3 .

[0056] By comparing the results of the above Examples 4 to 6 with Example 1, it can be seen that the present invention further uses a mixed insulating coating liquid of phytic acid aluminum sol and silica sol to perform insulating coating treatment on the ferroalloy soft magnetic powder, which can significantly enhance its insulating coating effect and improve its bonding molding effect, thereby significantly improving the comprehensive magnetic properties.

[0057] Comparative Example 1

[0058] A method for preparing a high-frequency low-loss magnetic powder core. Compared with Example 1, manganese-zinc ferrite powder with an average particle size of 10 μm is used to replace manganese-zinc ferrite powder with an average particle size of 2 μm.

[0059] In this comparative example, the density of the obtained magnetic powder core is 5.679 g / cm 3 , the inductance is 10.26μH and the loss is 1630kW / m 3 .

[0060] By comparing the results with those of Example 1, it can be seen that the use of ferrite powder with the same particle size as the iron alloy soft magnetic powder can significantly reduce the inductance value while reducing the loss of the obtained magnetic powder core. This further proves that the use of a mixture of large-particle-size iron alloy soft magnetic powder and small-particle-size ferrite powder can reduce the adverse effect on the inductance value.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a high-frequency low-loss magnetic powder core, characterized in that: The method comprises the following preparation steps: (1) subjecting an iron alloy soft magnetic powder having a particle size of 5 to 50 μm to an insulation coating treatment to obtain an insulation coated iron alloy soft magnetic powder; (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is evenly mixed with ferrite powder with a particle size of less than 5 μm and a binder, and then injected into a mold for compression molding, and then heated to 600-900° C. for annealing to obtain a high-frequency low-loss magnetic powder core.

2. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The iron alloy soft magnetic powder in step (1) is iron-nickel soft magnetic alloy powder, iron-silicon soft magnetic alloy powder or iron-silicon-aluminum soft magnetic alloy powder; the insulation coating treatment refers to insulation coating treatment using silicon dioxide or insulation coating treatment using silicon dioxide-aluminum phosphate composite.

3. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The insulation coating treatment refers to the use of a silicon dioxide-aluminum phosphate composite for insulation coating treatment; the method for the insulation coating treatment of the silicon dioxide-aluminum phosphate composite is as follows: 1) adding phytic acid to an alcohol aqueous solution to dissolve it, then adding an aluminum alkoxide solution to mix and react to obtain a phytic acid aluminum sol, and then mixing the phytic acid aluminum sol with a silica sol to obtain an insulating coating solution; 2) The ferroalloy soft magnetic powder is evenly mixed with the insulating coating liquid of step 1), first dried at 60-100° C. to remove the solvent, and then heated to 300-800° C. for heat treatment to obtain ferroalloy soft magnetic powder with a silicon dioxide-aluminum phosphate composite insulation coating.

4. The method for preparing a high-frequency low-loss magnetic powder core according to claim 3, characterized in that: The alcohol aqueous solution in step 1) is an ethanol aqueous solution with an ethanol volume percentage of 80 to 95%; The aluminum alkoxide solution is aluminum triethoxide solution, aluminum propoxide solution, aluminum isopropoxide solution or aluminum n-butoxide solution; the amount of the aluminum alkoxide solution added is such that the pH value of the reaction system is 5-7; the amount of the silica sol added is 20-60% of the mass of the phytic acid in terms of silicon dioxide content.

5. The method for preparing a high-frequency low-loss magnetic powder core according to claim 3, characterized in that: The amount of the insulating coating liquid added in step 2) is 0.2-2% of the mass of the ferroalloy soft magnetic powder in terms of solid content.

6. The method for preparing a high-frequency low-loss magnetic powder core according to claim 3, characterized in that: The drying and removing of the solvent in step 2) is carried out under vacuum conditions; the heat treatment is carried out under nitrogen protection conditions, and the heat treatment time is 3 to 10 hours.

7. The method for preparing a high-frequency low-loss magnetic powder core according to claim 3, characterized in that: The ferrite powder in step (2) is manganese-zinc ferrite, copper-zinc ferrite or nickel-zinc ferrite powder; the added amount of ferrite powder is 5% to 20% of the mass of the insulating coated iron alloy soft magnetic powder.

8. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The binder in step (2) is an epoxy resin binder or a silicone resin binder; the amount of the binder added is 0.2 to 1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder, calculated by its solid content.

9. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The temperature of the pressing molding in step (2) is 60-100° C. and the pressure is 500-800 MPa; the time of the annealing treatment is 15-120 min.

10. A high-frequency low-loss magnetic powder core, characterized in that: It is prepared by the method according to any one of claims 1 to 9.