Method for insulating coating of soft magnetic powder and use thereof

Abstract

The application provides an insulating coating method of soft magnetic powder and application thereof, and the insulating coating method comprises the following steps: (1) mixing an insulating agent with a solvent to obtain solution A through one-step stirring; (2) mixing the solution A obtained in the step (1) with insulating powder to obtain solution B through two-step stirring; and (3) mixing the soft magnetic powder with the solution B and heating to volatilize the solvent to obtain insulating soft magnetic powder. The insulating coating method of the soft magnetic powder is simple in process and friendly to the environment, the prepared insulating soft magnetic powder has good antirust effect and high stability, and can obviously improve the electrical insulation performance of an integrally-formed inductor.

Description

Technical Field

[0001] This invention belongs to the field of inductor technology and relates to an insulating coating method for soft magnetic powder and its application. Background Technology

[0002] Molded inductors possess excellent properties such as small size, good frequency characteristics, and low loss, and are widely used in power modules, portable electronic devices, PC graphics cards, and other fields. With the advancement of automation control technology, smart terminals, and other electronic manufacturing fields, the application environments of molded inductors are becoming increasingly harsh and diverse, especially in some application environments with high temperature, high humidity, and high acidity / alkalinity. Therefore, it is necessary to insulate the metal powder to prevent it from rusting and causing failure.

[0003] Currently, in terms of rust prevention processes, some high-efficiency rust inhibitors used on the market employ large amounts of chemical solvents, such as organic coatings and traditional phosphating, which cause certain environmental pollution. Some water-based rust inhibitors and their methods are not suitable for the insulation of metal powders in terms of their processability, such as zinc-based and zirconium-based film passivation agents and steel passivation agents.

[0004] CN111063535A discloses a method for preparing carbonyl iron powder for producing rust-preventive powder for integrally molded inductors, comprising the following steps: phosphating carbonyl iron powder; dissolving epoxy resin and silicone resin together in acetone to form an adhesive solution; diluting a special insulating agent with acetone; diluting a film-forming agent with acetone; firstly, adding the adhesive solution to the phosphated carbonyl iron powder and stirring until a slurry is formed, then adding the special insulating agent solution and continuing stirring; after stirring evenly, adding the film-forming agent solution and continuing stirring; after stirring evenly again, granulating, air-drying, and then baking; then adding zinc stearate and stirring evenly; and finally sieving to obtain carbonyl iron powder for rust prevention. The insulating layer formed by this method is generally relatively thick, which affects the soft magnetic properties of the integrally molded inductor.

[0005] CN114628137A discloses an insulating coating method for soft magnetic powder, comprising the following steps: mixing phosphoric acid and banana oil evenly to obtain a passivation solution; mixing soft magnetic powder with the passivation solution, soaking, dispersing the powder, sieving, baking, and cooling to obtain powder A; mixing silicone resin and banana oil evenly to obtain a rust-preventive solution; mixing powder A with the rust-preventive solution, soaking, dispersing, sieving, baking, and cooling to obtain powder B; mixing epoxy resin, curing agent, and banana oil evenly to obtain a binder; mixing powder B with the binder, soaking, dispersing, granulating, baking, and cooling to obtain powder C; sieving powder C, adding lubricant, and mixing evenly to obtain the final product. The insulating layers prepared by this method generally suffer from problems such as unevenness, cracking, peeling, and poor weather resistance, affecting the electrical insulation performance of the integrally molded inductor. Summary of the Invention

[0006] The purpose of this invention is to provide an insulating coating method for soft magnetic powder and its application. The insulating coating method for soft magnetic powder described in this invention is simple and environmentally friendly, and the resulting insulating soft magnetic powder has good rust prevention effect and high stability, which can significantly improve the electrical insulation performance of integrally molded inductors.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an insulating coating method for soft magnetic powder, the insulating coating method comprising the following steps:

[0009] (1) The insulating agent and solvent are mixed and stirred in one step to obtain solution A;

[0010] (2) Mix the solution A obtained in step (1) with the insulating powder, and then stir in two steps to obtain solution B;

[0011] (3) Mix the soft magnetic powder with solution B and heat to evaporate the solvent to obtain insulating soft magnetic powder.

[0012] The solvent used in this invention is water, which does not produce waste liquid and is friendly to human health and the environment. One or more of the insulating powders used have a sheet-like and multi-layered structure. Based on the intercalation principle, the insulating agent is dispersed into the insulating powder layers by ultrasonic dispersion, which makes the insulating layer denser, stronger, and more waterproof. At the same time, the sheet-like structure of the selected insulating powder can also effectively hinder the diffusion of chloride ions to achieve the effect of rust prevention. The drum stirring helps the insulating powder to form a certain orientation in the insulating layer, making the insulating layer thinner and more uniform.

[0013] Preferably, the insulating agent in step (1) comprises any two or at least three of the following: lithium silicate, sodium silicate, potassium silicate, sodium methylsilicate, tetrabutyl orthosilicate, tetrabutyl titanate, nano silica sol, or polyvinyl alcohol.

[0014] Preferably, the solvent includes water.

[0015] Preferably, the stirring method in step (1) includes mechanical stirring.

[0016] Preferably, the stirring time for the first step is 5 to 10 minutes, for example: 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes.

[0017] Preferably, the insulating powder in step (2) includes any two or at least three of the following: nano zinc oxide, nano silicon dioxide, nano titanium dioxide, nano aluminum oxide, ultrafine kaolin, ultrafine talc, ultrafine montmorillonite, or ultrafine diatomaceous earth.

[0018] Preferably, the two-step stirring method in step (2) includes ultrasonic stirring.

[0019] Preferably, the two-step stirring time is 20 to 60 minutes, for example: 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0020] Preferably, the soft magnetic powder in step (3) comprises gas-atomized FeSiCr powder.

[0021] Preferably, the mass ratio of the soft magnetic powder, the insulating agent, and the insulating powder is 100:(0.1~2):(0.1~2), for example: 100:0.1:0.1, 100:0.3:0.4, 100:0.5:0.3, 100:0.6:0.5, or 100:2:2, etc.

[0022] Preferably, the temperature at which the solvent is heated in step (3) is 80 to 100°C, for example: 80°C, 85°C, 90°C, 95°C or 100°C.

[0023] Preferably, in step (3), the solvent is heated and stirred simultaneously.

[0024] Preferably, the stirring speed is 15 to 30 rpm, for example: 15 rpm, 18 rpm, 20 rpm, 25 rpm or 30 rpm.

[0025] In a second aspect, the present invention provides an insulating soft magnetic powder, which is prepared by the coating method described in the first aspect.

[0026] Thirdly, the present invention provides a molded inductor comprising insulating soft magnetic powder as described in the second aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The insulating soft magnetic powder prepared by the insulating coating method of the present invention has a uniform surface insulating layer that is not easy to crack, has high stability and good weather resistance, and can significantly improve the electrical insulation performance of the integrally molded inductor.

[0029] (2) The insulating soft magnetic powder obtained by the insulating method described in this invention is used to prepare a blank using an integrally molded inductor process. The blank has a high magnetic permeability of 25-28 and a high insulation resistance of 10-100 GΩ. At the same time, the blank does not rust at all after a 24-hour neutral salt spray test. Attached Figure Description

[0030] Figure 1This is a 24-hour neutral salt spray test image of an inductor blank formed by pressing the insulating soft magnetic powder obtained in Example 1 of this invention into an integral molded sample.

[0031] Figure 2 This is a 24-hour neutral salt spray test image of an inductor blank formed by pressing the insulating soft magnetic powder obtained in Example 2 of this invention into an integral molded sample.

[0032] Figure 3 This is a 24-hour neutral salt spray test result of the soft magnetic powder of Comparative Example 1, which is pressed into an integral inductor blank.

[0033] Figure 4 This is a 24-hour neutral salt spray test result of an inductor blank made by pressing the insulating soft magnetic powder obtained in Comparative Example 2 into an integral molded sample. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0035] All parts mentioned in the embodiments and comparative examples of this invention are parts by mass.

[0036] Example 1

[0037] This embodiment provides an insulating soft magnetic powder, and the insulating coating method of the insulating soft magnetic powder is as follows:

[0038] (1) Mix 0.2 parts lithium silicate, 0.2 parts sodium silicate, 0.1 parts polyvinyl alcohol and 30 parts water, and stir mechanically for 8 minutes to obtain solution A;

[0039] (2) Mix solution A obtained in step (1) with 0.15 parts of ultrafine talc powder and 0.15 parts of ultrafine diatomaceous earth, and stir ultrasonically for 30 minutes to obtain solution B;

[0040] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 90°C and 20 rpm to evaporate the solvent to obtain the insulating soft magnetic powder.

[0041] Example 2

[0042] This embodiment provides an insulating soft magnetic powder, and the insulating coating method of the insulating soft magnetic powder is as follows:

[0043] (1) Mix 0.1 parts lithium silicate, 0.1 parts sodium silicate, 0.1 parts potassium silicate, 0.1 parts polyvinyl alcohol and 30 parts water, and stir mechanically for 8 minutes to obtain solution A;

[0044] (2) Mix solution A obtained in step (1) with 0.2 parts of ultrafine talc powder and 0.2 parts of ultrafine diatomaceous earth, and stir ultrasonically for 30 minutes to obtain solution B;

[0045] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 95°C and 25 rpm to evaporate the solvent and obtain the insulating soft magnetic powder.

[0046] Example 3

[0047] This embodiment provides an insulating soft magnetic powder, and the insulating coating method of the insulating soft magnetic powder is as follows:

[0048] (1) Mix 0.1 parts of lithium glass with 30 parts of water and stir mechanically for 8 minutes to obtain solution A;

[0049] (2) Mix solution A obtained in step (1) with 0.15 parts of ultrafine talc powder and 0.15 parts of ultrafine diatomaceous earth, and stir ultrasonically for 30 minutes to obtain solution B;

[0050] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 90°C and 20 rpm to evaporate the solvent to obtain the insulating soft magnetic powder.

[0051] Example 4

[0052] This embodiment provides an insulating soft magnetic powder, and the insulating coating method of the insulating soft magnetic powder is as follows:

[0053] (1) Mix 0.3 parts lithium silicate, 0.3 parts sodium silicate, 0.3 parts potassium silicate, 0.3 parts polyvinyl alcohol and 30 parts water, and stir mechanically for 8 minutes to obtain solution A;

[0054] (2) Mix solution A obtained in step (1) with 0.2 parts of ultrafine talc powder and 0.2 parts of ultrafine diatomaceous earth, and stir ultrasonically for 30 minutes to obtain solution B;

[0055] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 95°C and 25 rpm to evaporate the solvent and obtain the insulating soft magnetic powder.

[0056] Example 5

[0057] (1) Mix 0.2 parts lithium silicate, 0.2 parts sodium silicate, 0.1 parts polyvinyl alcohol and 30 parts water, and stir mechanically for 8 minutes to obtain solution A;

[0058] (2) Mix solution A obtained in step (1) with 0.15 parts of ultrafine talc powder and stir ultrasonically for 30 min to obtain solution B;

[0059] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 90°C and 20 rpm to evaporate the solvent to obtain the insulating soft magnetic powder.

[0060] Example 6

[0061] (1) Mix 0.2 parts lithium silicate, 0.2 parts sodium silicate, 0.1 parts polyvinyl alcohol and 30 parts water, and stir mechanically for 8 minutes to obtain solution A;

[0062] (2) Mix solution A obtained in step (1) with 0.6 parts of ultrafine talc powder and 0.6 parts of ultrafine diatomaceous earth, and stir ultrasonically for 30 minutes to obtain solution B;

[0063] (3) Weigh 100 parts of atomized FeSiCr powder and add it to an inclined heatable drum. Slowly add solution B and stir and heat at 90°C and 20 rpm to evaporate the solvent to obtain the insulating soft magnetic powder.

[0064] Comparative Example 1

[0065] The only difference between this comparative example and Example 1 is that only 100 parts of FeSiCr powder were used, without any treatment.

[0066] Comparative Example 2

[0067] This comparative example provides a soft magnetic powder, and the preparation method of the soft magnetic powder is as follows:

[0068] Take 0.2 parts of phosphoric acid and add it to 20 parts of acetone solution. Stir mechanically for 5-10 minutes. Take 100 parts of gas-atomized FeSiCr powder and add it to acetone solution containing phosphoric acid. Stir ultrasonically until the solvent is completely evaporated. Dry at 160℃ for 1 hour to obtain the soft magnetic powder.

[0069] Performance testing:

[0070] Take 100 parts of each of the soft magnetic powders obtained in Examples 1-6 and Comparative Examples 1-2 and set them aside. Then, weigh 2.8 parts of epoxy resin and 0.28 parts of curing agent, add 20 parts of acetone solution, stir for 5 minutes, and then add 100 parts of the weighed insulating powder. Continue stirring until the solvent has completely evaporated. Pass the insulating powder coated with epoxy resin and curing agent through a 40-mesh sieve and dry it to obtain granulated powder. Then, weigh an appropriate amount of granulated powder and granulate it at 6T / cm. 2 The magnetic rings were pressurized to 17*9*5mm, and after annealing, test sample blanks were obtained. The test results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] As can be seen from Table 1, the insulating soft magnetic powder prepared by the method of the present invention, as obtained from Examples 1-2, has high magnetic permeability (26-28) and insulation resistance (10-50 GΩ) while ensuring the rust prevention effect.

[0075] A comparison of Examples 1 and 3-4 shows that in the insulating coating method of the present invention, the mass ratio of soft magnetic powder to insulating agent affects the effect of obtaining insulating soft magnetic powder. Controlling the mass ratio of soft magnetic powder to insulating agent to 100:0.1-2 results in better performance of the insulating soft magnetic powder. If the amount of insulating agent added is too large, the insulation resistance of the blank increases significantly. However, since the insulating agent is a non-magnetic substance, excessive addition will lead to a loose insulating layer, low blank density, and consequently, reduced magnetic permeability. If the amount of insulating agent added is too small, the insulating powder cannot completely adhere to the surface of the metal powder, resulting in a thin, incomplete, uniform, and dense insulating layer. Although the magnetic permeability is improved, the insulation resistance between the powders decreases significantly, leading to a decrease in the overall electrical insulation properties of the blank and poor rust prevention effect.

[0076] A comparison of Examples 1 and 5-6 shows that in the insulating coating method of the present invention, the mass ratio of soft magnetic powder to insulating powder affects the effect of obtaining insulating soft magnetic powder. Controlling the mass ratio of soft magnetic powder to insulating powder at 100:0.1-2 results in better performance of the insulating soft magnetic powder. If the amount of insulating powder added is too large, since the insulating auxiliary materials are all non-magnetic inorganic oxides, excessive addition will reduce the proportion of magnetic powder and decrease the magnetic permeability. Simultaneously, due to the small particle size and high hardness of the insulating auxiliary materials, they are prone to accumulation and agglomeration, which in turn affects the uniformity and strength of the insulating layer, resulting in no significant improvement in electrical insulation and affecting its rust-preventive effect. If the amount of insulating powder added is too small, the density of the insulating layer decreases, affecting the integrity and uniformity of the insulating layer. While the magnetic permeability may increase, the electrical insulation performance is not significantly improved.

[0077] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, the insulating soft magnetic powder prepared by the method of the present invention, compared with FeSiCr metal powder obtained without any treatment or through common phosphating processes, exhibits complete rust prevention in a 24-hour neutral salt spray test, while also possessing higher magnetic permeability (26-28) and insulation resistance (10-50 GΩ). Furthermore, the method of the present invention is simple to operate, uses low-cost materials, is environmentally friendly, and is suitable for mass production.

[0078] The soft magnetic powders obtained in Examples 1-2 and Comparative Examples 1-2 were pressed into integrally formed inductor blanks, and subjected to 24-hour neutral salt spray tests. The test results are shown in the figure below. Figure 1-4 As shown, by Figure 1-4 It can be seen that the insulation coating method described in this application significantly improves the rust prevention effect compared with uncoated or conventionally coated soft magnetic powder.

[0079] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for insulating coating of soft magnetic powder, characterized in that, The insulation coating method includes the following steps: (1) Mix the insulating agent with the solvent and stir in one step to obtain solution A; (2) The solution A obtained in step (1) is mixed with insulating powder, wherein one or more of the insulating powder has a sheet-like and multilayer structure, and the mixture is ultrasonically stirred to obtain solution B; wherein the ultrasonic stirring enables the insulating agent to be dispersed into the interlayer of the insulating powder. (3) Mix the soft magnetic powder with solution B, and stir in a drum while heating to evaporate the solvent to obtain insulating soft magnetic powder; wherein the mass ratio of the soft magnetic powder, insulating agent and insulating powder is 100:(0.1~1.2):(0.1~1.2).

2. The insulation coating method as described in claim 1, characterized in that, The insulating agent in step (1) includes any two or at least three of the following: lithium silicate, sodium silicate, potassium silicate, sodium methyl silicate, tetraethyl orthosilicate, tetrabutyl titanate, nano silica sol, or polyvinyl alcohol.

3. The insulation coating method as described in claim 1, characterized in that, The solvent includes water.

4. The insulation coating method as described in claim 1, characterized in that, The stirring method described in step (1) includes mechanical stirring.

5. The insulation coating method as described in claim 1, characterized in that, The stirring time for this step is 5-10 minutes.

6. The insulation coating method as described in claim 1, characterized in that, The insulating powder in step (2) includes any two or at least three of the following: nano zinc oxide, nano silicon dioxide, nano titanium dioxide, nano aluminum oxide, ultrafine kaolin, ultrafine talc, ultrafine montmorillonite powder, or ultrafine diatomaceous earth, and one or more of the insulating powders have a sheet-like and multilayered structure.

7. The insulation coating method as described in claim 1, characterized in that, The two-step stirring time is 20~60 min.

8. The insulation coating method as described in claim 1, characterized in that, The soft magnetic powder in step (3) includes gas-atomized FeSiCr powder.

9. The insulation coating method as described in claim 1, characterized in that, The temperature for heating the volatile solvent in step (3) is 80~100 ℃.

10. The insulation coating method as described in claim 1, characterized in that, The stirring speed is 15~30 rpm.

11. An insulating soft magnetic powder, characterized in that, The insulating soft magnetic powder is prepared by the coating method as described in any one of claims 1-10.

12. A molded inductor, characterized in that, The integrally molded inductor comprises the insulating soft magnetic powder as described in claim 11.

Images