Integrally-formed inductor and preparation method and application thereof

Abstract

The invention discloses an integrally-formed inductor and a preparation method and application thereof, and relates to the technical field of electronic devices.The preparation method comprises the steps that an aluminum oxide layer grows on the surface of magnetic powder in situ, first-stage coating treatment is completed, first-stage coated magnetic powder is obtained, and the magnetic powder comprises gas atomization iron-based alloy powder; the first-stage coated magnetic powder and a second-stage coating agent are mixed, ethyl alcohol is added, stirring and air drying are conducted, second-stage coated magnetic powder is obtained, and the second-stage coating agent comprises methyl cellulose, sub-nanometer molybdenum oxide and sub-nanometer titanium dioxide; carrying out extrusion granulation on the secondary coated magnetic powder to obtain powder; placing the n-shaped copper sheet in a cavity of a molding press, filling powder, and pressing to obtain a molded inductor; glue discharging is carried out on the formed inductor; sintering the molded inductor after glue discharging to obtain a sintered inductor; according to the invention, the technical problem that the loss of the integrally formed inductor is increased due to the traditional high-pressure compression molding can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic devices, and in particular to an integrally formed inductor and a preparation method and application thereof. Background Art

[0002] One-piece molded inductors are usually made by mixing metal magnetic powder (such as sendust, iron-nickel-molybdenum, etc.) with an organic binder. After mold pressing and high-temperature curing, the winding is completely wrapped inside the magnetic material to form a solid overall structure.

[0003] Currently, organic binders are mostly high-temperature-resistant silicone or water glass. However, high temperatures can irreversibly affect the reliability of modified silicone, posing a certain risk of aging. Furthermore, water glass will carbonize with atmospheric carbon dioxide, requiring immediate preparation and use, which is not conducive to large-scale granulation powder reserve production. Furthermore, high-pressure pressing can damage the brittle inorganic coating, which also affects the insulation between powder particles. Reduced surface resistance can increase the loss of the sintered inductor. For press molding, achieving higher density often requires pressing the green body at a pressure of over 2000 MPa. Excessive pressure can cause severe deformation of the powder particles, squeezing and deforming the insulating coating, or even rupturing it, resulting in an irreversible increase in magnetic powder core loss. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an integrally molded inductor and its preparation method and application, aiming to solve the technical problem that traditional high-pressure molding will increase the loss of the integrally molded inductor.

[0005] A first aspect of the present invention is to provide a method for preparing an integrally formed inductor, the method comprising:

[0006] In-situ growing of an aluminum oxide layer on the surface of the magnetic powder to complete a primary coating process to obtain a primary coated magnetic powder, wherein the magnetic powder comprises a gas atomized iron-based alloy powder;

[0007] The primary coated magnetic powder and the secondary coating agent are mixed in a preset mass ratio, and then ethanol of a preset mass concentration is added and stirred. After the ethanol in the powder evaporates, the powder is air-dried for a first preset time to obtain the secondary coated magnetic powder, wherein the secondary coating agent includes methyl cellulose, sub-nanometer molybdenum oxide, and sub-nanometer titanium dioxide;

[0008] Extruding and granulating the secondary coated magnetic powder to obtain a powder;

[0009] Placing several types of copper sheets in a molding press cavity, filling the powder material therein, and pressing at a preset pressing pressure for a second preset time to obtain a molded inductor;

[0010] Debinding the molded inductor at a preset debinding temperature for a third preset time under a preset debinding atmosphere to remove the organic phase;

[0011] sintering the debonded molded inductor at a preset sintering temperature for a fourth preset time under a preset sintering atmosphere to obtain a sintered inductor;

[0012] The sintered inductor is sprayed with paint, and the copper sheets at both ends of the painted sintered inductor are folded to obtain an integrally formed inductor.

[0013] Compared with the prior art, the beneficial effect of the present invention is that: through the preparation method of an integrally molded inductor provided by the present invention, the interfacial reaction between the molybdenum oxide melt and the iron-based alloy powder at high temperature reduces the surface energy, so that the molybdenum oxide melt can fully wet the iron-based alloy powder. The localized interfacial reaction also helps to obtain a higher two-phase (liquid-solid) bonding force, reduce loss, and increase inductance, so that the density of the integrally molded inductor is higher and has better thermal conductivity, which is beneficial to the heat dissipation of the integrally molded inductor. At the same time, titanium dioxide and aluminum oxide have good lattice matching, and the progressive oxygen release of titanium dioxide can ensure the controllable oxidation of the iron-based alloy powder. It itself becomes ferromagnetic under oxygen-deficient conditions, thereby reducing the magnetic dilution effect, reducing loss, and increasing inductance. Furthermore, the iron-based alloy powder particles are effectively isolated by the deposited aluminum oxide insulating layer, further reducing eddy current loss, thereby solving the technical problem that traditional high-pressure die-casting will increase the loss of the integrally molded inductor.

[0014] According to one aspect of the above technical solution, the iron-based alloy powder includes one or a mixture of FeSiCr, FeSiAl, FeSi, and FeNi, and the thickness of the aluminum oxide is 1 μm to 3 μm.

[0015] According to one aspect of the above technical solution, the preset mass ratio is (18-20):1, the preset mass concentration is 5%-10%, and the first preset time is 20min-30min.

[0016] According to one aspect of the above technical solution, the mass ratio of the methyl cellulose, sub-nano molybdenum oxide and sub-nano titanium dioxide is 1: (1-4): (0.5-3).

[0017] According to one aspect of the above technical solution, the preset pressing pressure is 50 MPa to 150 MPa, and the second preset time is 1 s to 10 s.

[0018] According to one aspect of the above technical solution, the preset debinding temperature is 400° C. to 500° C., the third preset time is 50 min to 70 min, and the preset debinding atmosphere is a nitrogen atmosphere.

[0019] According to one aspect of the above technical solution, the preset sintering temperature is 750℃~800℃, the fourth preset time is 50min~70min, and the preset sintering atmosphere is nitrogen and hydrogen atmosphere, and the volume ratio of nitrogen and hydrogen is (2~5):1.

[0020] According to one aspect of the above technical solution, the mesh size of the sieve for extrusion granulation is 20 to 80 meshes.

[0021] A second aspect of the present invention is to provide an integrally formed inductor manufactured by the above-mentioned method for manufacturing an integrally formed inductor.

[0022] A third aspect of the present invention is to provide applications of an integrally formed inductor prepared by the above-mentioned method for preparing an integrally formed inductor in circuit boards and electronic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0024] Figure 1 It is a flowchart of the method for preparing the integrally formed inductor of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0026] See also Figure 1 , which shows a method for preparing an integrally formed inductor provided by the present invention, the method comprising steps S10-S16:

[0027] Step S10, in-situ growing an aluminum oxide layer on the surface of the magnetic powder to complete a primary coating process to obtain a primary coated magnetic powder, wherein the magnetic powder includes a gas atomized iron-based alloy powder;

[0028] The iron-based alloy powder includes one or a mixture of FeSiCr, FeSiAl, FeSi and FeNi.

[0029] In addition, alumina has high density and high resistance. In-situ growth of alumina on the surface of magnetic powder can effectively increase the surface resistance of the magnetic powder and reduce eddy current loss.

[0030] Preferably, the thickness of the aluminum oxide is 1 μm to 3 μm, for example, 1 μm, 2 μm or 3 μm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0031] Step S11, mixing the primary coated magnetic powder and the secondary coating agent according to a preset mass ratio, adding ethanol of a preset mass concentration and stirring, and after the ethanol in the powder evaporates, air-drying for a first preset time to obtain the secondary coated magnetic powder, wherein the secondary coating agent includes methyl cellulose, sub-nanometer molybdenum oxide, and sub-nanometer titanium dioxide;

[0032] The preset mass ratio is (18-20):1, and the mass ratio of the methylcellulose, sub-nano molybdenum oxide, and sub-nano titanium dioxide is 1:(1-4):(0.5-3). Sub-nano molybdenum oxide and sub-nano titanium dioxide are sintering aids that can achieve localized liquid-phase sintering of the iron-based alloy powder / sub-nano molybdenum oxide / sub-nano titanium dioxide.

[0033] In order to reduce the agglomeration phenomenon between particles and improve the uniformity and effect of coating, ethanol of a preset mass concentration is added and stirred. The preset mass concentration is 5% to 10%, for example, it can be 5%, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0034] Furthermore, the stirring time for adding ethanol is 40 min to 60 min.

[0035] In addition, air drying is performed for a first preset time to remove ethanol, wherein the first preset time is 20 minutes to 30 minutes.

[0036] Step S12, extruding and granulating the secondary coated magnetic powder to obtain a powder;

[0037] Wherein, the mesh number of the sieve for extrusion granulation is 20 mesh to 80 mesh.

[0038] Step S13, placing the copper sheets in a molding press cavity, filling the powder material therein, and pressing the molded inductor at a preset pressing pressure for a second preset time to obtain a molded inductor;

[0039] Among them, the preset pressing pressure is 50Mpa~150Mpa, and the second preset time is 1s-10s. Low-pressure pressing is to reduce losses, because excessive pressure will cause serious deformation of powder particles, and the coating layer will be squeezed, deformed or even ruptured, causing the loss of the one-piece molded inductor to increase irreversibly.

[0040] Step S14, debinding the molded inductor at a preset debinding temperature for a third preset time under a preset debinding atmosphere to remove the organic phase;

[0041] In order to prevent the organic phase from volatilizing during high-temperature sintering, which would cause pores and defects to form in the one-piece molded inductor and affect the overall performance of the one-piece molded inductor, it is necessary to perform debinding treatment in advance to remove the organic phase.

[0042] Preferably, the preset debinding temperature is 400°C to 500°C, for example, 400°C, 420°C, 450°C, 480°C or 500°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0043] In addition, the third preset time is 50 minutes to 70 minutes, and the preset debinding atmosphere is a nitrogen atmosphere.

[0044] Debinding is performed in a nitrogen atmosphere to prevent oxidation of the iron-based alloy powder and affect performance.

[0045] Step S15, sintering the debinded molded inductor at a preset sintering temperature for a fourth preset time under a preset sintering atmosphere to obtain a sintered inductor;

[0046] The preset sintering temperature is 750°C to 800°C, for example, 750°C, 760°C, 770°C, 780°C, 790°C or 800°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0047] Furthermore, the fourth preset time is 50 minutes to 70 minutes, the preset sintering atmosphere is a nitrogen and hydrogen atmosphere, and the volume ratio of nitrogen to hydrogen is (2 to 5):1.

[0048] It should be noted that the interfacial reaction between the molybdenum oxide melt and the iron-based alloy powder at high temperature reduces the surface energy, allowing the molybdenum oxide melt to fully wet the iron-based alloy powder. The localized interfacial reaction also helps to obtain a higher two-phase (liquid-solid) bonding force. At the same time, titanium dioxide and aluminum oxide have good lattice matching. The gradual oxygen release of titanium dioxide ensures the controlled oxidation of the iron-based alloy powder. Titanium dioxide itself becomes ferromagnetic under oxygen-deficient conditions, thereby reducing the magnetic dilution effect. Furthermore, the iron-based alloy powder particles are effectively isolated by the deposited aluminum oxide insulating layer, thereby reducing eddy current losses.

[0049] It can be understood that the atomic deposition technology is used to in-situ grow an aluminum oxide insulating layer on the surface of the magnetic powder, and then a connection between the powders is formed through a secondary coating agent as a two-phase sintering bonding layer. Sub-nano molybdenum oxide and sub-nano titanium dioxide are used as sintering aids to achieve localized liquid phase sintering of iron-based alloy powder / molybdenum oxide / titanium dioxide, reducing losses and increasing inductance. The structure has higher strength and reliability, making the one-piece molded inductor have a higher density and better thermal conductivity, which is beneficial to the heat dissipation of the one-piece molded inductor.

[0050] Step S16: spray-paint the sintered inductor, and fold the copper sheets at both ends of the painted sintered inductor to obtain an integrally formed inductor.

[0051] Preferably, the anti-rust paint of the spray paint is acrylic paint, and the thickness of the spray paint is 0.15mm to 0.35mm.

[0052] In addition, the present invention also provides an integrally formed inductor prepared by the above-mentioned method for preparing the integrally formed inductor.

[0053] Among them, the size of the one-piece molded inductor is 10.0*7.0*6.0mm.

[0054] In addition, the present invention also provides applications of the integrally formed inductor prepared by the above-mentioned method for preparing the integrally formed inductor in circuit boards and electronic components.

[0055] The present invention is further described below with specific examples:

[0056] Example 1

[0057] A first embodiment of the present invention provides a method for preparing an integrally formed inductor, the method comprising steps S10-S16:

[0058] Step S10, in-situ growing an aluminum oxide layer on the surface of the magnetic powder to complete a primary coating process to obtain a primary coated magnetic powder, wherein the magnetic powder includes a gas atomized iron-based alloy powder;

[0059] Wherein, the iron-based alloy powder is FeSi.

[0060] Preferably, the thickness of the aluminum oxide is 2 μm.

[0061] Step S11, mixing the primary coated magnetic powder and the secondary coating agent according to a preset mass ratio, adding ethanol of a preset mass concentration and stirring, and after the ethanol in the powder evaporates, air-drying for a first preset time to obtain the secondary coated magnetic powder, wherein the secondary coating agent includes methyl cellulose, sub-nanometer molybdenum oxide, and sub-nanometer titanium dioxide;

[0062] The mass percentage of the primary coated magnetic powder is 95%, the mass percentage of methyl cellulose is 1%, the mass percentage of sub-nano molybdenum oxide is 2.5%, and the mass percentage of sub-nano titanium dioxide is 1.5%.

[0063] The preset mass concentration of ethanol is 7%, and the stirring time after adding ethanol is 40 minutes.

[0064] In addition, air drying is performed for a first preset time to remove ethanol, wherein the first preset time is 25 minutes.

[0065] Step S12, extruding and granulating the secondary coated magnetic powder to obtain a powder;

[0066] Wherein, the mesh number of the sieve for extrusion granulation is 50 meshes.

[0067] Step S13, placing the copper sheets in a molding press cavity, filling the powder material therein, and pressing the molded inductor at a preset pressing pressure for a second preset time to obtain a molded inductor;

[0068] Wherein, the preset pressing pressure is 100 MPa, and the second preset time is 5 seconds.

[0069] Step S14, debinding the molded inductor at a preset debinding temperature for a third preset time under a preset debinding atmosphere to remove the organic phase;

[0070] Preferably, the preset debinding temperature is 450°C.

[0071] In addition, the third preset time is 60 minutes, and the preset binder removal atmosphere is a nitrogen atmosphere.

[0072] Step S15, sintering the debinded molded inductor at a preset sintering temperature for a fourth preset time under a preset sintering atmosphere to obtain a sintered inductor;

[0073] The preset sintering temperature is 780° C., the fourth preset time is 60 min, and the preset sintering atmosphere is a nitrogen and hydrogen atmosphere, with a volume ratio of nitrogen to hydrogen of 3:1.

[0074] Step S16: spray-paint the sintered inductor, and fold the copper sheets at both ends of the painted sintered inductor to obtain an integrally formed inductor.

[0075] Preferably, the anti-rust paint of the spray paint is acrylic paint, and the thickness of the spray paint is 0.15mm to 0.35mm.

[0076] Example 2

[0077] A second embodiment of the present invention provides a method for manufacturing an integrally formed inductor. The method for manufacturing the integrally formed inductor in this embodiment differs from the method for manufacturing the integrally formed inductor in the first embodiment in that:

[0078] The iron-based alloy powder is FeSiCr.

[0079] Example 3

[0080] A third embodiment of the present invention provides a method for manufacturing an integrally formed inductor. The method for manufacturing the integrally formed inductor in this embodiment differs from the method for manufacturing the integrally formed inductor in the first embodiment in that:

[0081] The iron-based alloy powder is FeSiAl.

[0082] Example 4

[0083] A fourth embodiment of the present invention provides a method for manufacturing an integrally formed inductor. The method for manufacturing the integrally formed inductor in this embodiment differs from the method for manufacturing the integrally formed inductor in the first embodiment in that:

[0084] The iron-based alloy powder is FeNi.

[0085] Comparative Example 1

[0086] The first comparative example of the present invention provides a method for preparing an integrally formed inductor. The method for preparing the integrally formed inductor in this comparative example differs from the method for preparing the integrally formed inductor in the first embodiment in that:

[0087] It is prepared by compression molding, with a preset pressing pressure of 2200 MPa and a preset sintering temperature of 180°C.

[0088] Comparative Example 2

[0089] A second comparative example of the present invention provides a method for preparing an integrally formed inductor. The method for preparing the integrally formed inductor in this comparative example differs from the method for preparing the integrally formed inductor in the first embodiment in that:

[0090] The iron-based alloy powder is FeSiCr, which is prepared by compression molding, with a preset compression pressure of 2200 MPa and a preset sintering temperature of 180°C.

[0091] Comparative Example 3

[0092] A third comparative example of the present invention provides a method for preparing an integrally formed inductor. The method for preparing the integrally formed inductor in this comparative example differs from the method for preparing the integrally formed inductor in the first embodiment in that:

[0093] The iron-based alloy powder is FeSiAl, which is prepared by compression molding, with a preset compression pressure of 2200 MPa and a preset sintering temperature of 180°C.

[0094] Comparative Example 4

[0095] A fourth comparative example of the present invention provides a method for preparing an integrally formed inductor. The method for preparing the integrally formed inductor in this comparative example differs from the method for preparing the integrally formed inductor in the first embodiment in that:

[0096] The iron-based alloy powder is FeNi, which is prepared by compression molding, with a preset compression pressure of 2200 MPa and a preset sintering temperature of 180°C.

[0097] Please refer to Table 1 below, which shows the performance test results of the one-piece molded inductors prepared under different embodiments and comparative examples.

[0098] Table 1

[0099]

[0100] It should be noted that the loss test method is to test the loss power per unit volume (per cubic centimeter) of the one-piece molded inductor under the conditions of magnetic induction intensity of 50mT and frequency of 100kHz. The test method for the percentage decrease in inductance L@78A is to test the percentage decrease in inductance compared to the initial inductance when a current of 78A passes through the one-piece molded inductor, reflecting the DC bias capability. The temperature rise current test method is to load current on the one-piece molded inductor at room temperature. The current when the temperature reaches 65°C is the temperature rise current.

[0101] As shown in Table 1, the one-piece molded inductor prepared by the present invention can effectively increase inductance and reduce losses. It also has excellent thermal conductivity, good heat dissipation performance, and excellent DC bias capability. Although the DC bias capability of the molded inductor is relatively better, its initial permeability is low (low inductance) and the loss is high, which cannot meet the high inductance requirements of the chip.

[0102] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0103] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an integrally formed inductor, characterized in that: The preparation method comprises: In-situ growing of an aluminum oxide layer on the surface of the magnetic powder to complete a primary coating process to obtain a primary coated magnetic powder, wherein the magnetic powder comprises a gas atomized iron-based alloy powder; The primary coated magnetic powder and the secondary coating agent are mixed in a preset mass ratio, and then ethanol of a preset mass concentration is added and stirred. After the ethanol in the powder evaporates, the powder is air-dried for a first preset time to obtain the secondary coated magnetic powder, wherein the secondary coating agent includes methyl cellulose, sub-nanometer molybdenum oxide, and sub-nanometer titanium dioxide; Extruding and granulating the secondary coated magnetic powder to obtain a powder; Placing several types of copper sheets in a molding press cavity, filling the powder material therein, and pressing at a preset pressing pressure for a second preset time to obtain a molded inductor; Debinding the molded inductor at a preset debinding temperature for a third preset time under a preset debinding atmosphere to remove the organic phase; sintering the debonded molded inductor at a preset sintering temperature for a fourth preset time under a preset sintering atmosphere to obtain a sintered inductor; The sintered inductor is sprayed with paint, and the copper sheets at both ends of the painted sintered inductor are folded to obtain an integrally formed inductor.

2. The method for preparing an integrally formed inductor according to claim 1, wherein: The iron-based alloy powder includes one or a mixture of FeSiCr, FeSiAl, FeSi, and FeNi, and the thickness of the aluminum oxide is 1 μm to 3 μm.

3. The method for preparing an integrally formed inductor according to claim 1, wherein: The preset mass ratio is (18-20):1, the preset mass concentration is 5%-10%, and the first preset time is 20 minutes-30 minutes.

4. The method for preparing an integrally formed inductor according to claim 3, wherein: The mass ratio of the methyl cellulose, sub-nano molybdenum oxide and sub-nano titanium dioxide is 1: (1-4): (0.5-3).

5. The method for preparing an integrally formed inductor according to claim 1, wherein: The preset pressing pressure is 50 MPa to 150 MPa, and the second preset time is 1 s to 10 s.

6. The method for preparing an integrally formed inductor according to claim 5, wherein: The preset debinding temperature is 400° C. to 500° C., the third preset time is 50 min to 70 min, and the preset debinding atmosphere is a nitrogen atmosphere.

7. The method for preparing an integrally formed inductor according to claim 1, wherein: The preset sintering temperature is 750° C. to 800° C., the fourth preset time is 50 min to 70 min, and the preset sintering atmosphere is a nitrogen and hydrogen atmosphere, with a volume ratio of nitrogen to hydrogen of (2 to 5):

1.

8. The method for preparing an integrally formed inductor according to claim 1, wherein: The mesh number of the sieve for extrusion granulation is 20 mesh to 80 mesh.

9. An integrally formed inductor prepared by the method for preparing an integrally formed inductor according to any one of claims 1 to 8.

10. Use of an integrally formed inductor prepared by the method for preparing an integrally formed inductor according to any one of claims 1 to 8 in circuit boards and electronic components.

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