Preparation method of high-temperature magnetic slurry capable of being formed at low pressure and used for inductor

Abstract

The invention discloses a preparation method of high-temperature magnetic slurry for an inductor capable of being formed at low pressure, and relates to the technical field of electronic component materials. Magnetic powder is pretreated through a coupling agent, a uniform molecular layer can be formed on the surface of the magnetic powder, the acting force between the magnetic powder and organic molecules of a glue solution is improved, dispersity is enhanced, and eddy-current loss is reduced; the epoxy resin system with a specific ratio uniformly coats the magnetic powder by means of a high-speed rotation mode of a homogenizer, and can be converted into a viscous flow state after being heated, so that the magnetic powder has excellent warm-pressure fluidity, improves the magnetic density through pressing, can be matched with a curing agent to be rapidly cured, can be stably formed under the low pressure of 30-50 MPa, and avoids coil damage and magnetic core cracking; and the method is suitable for preparation of complex-structure composite inductors.

Description

Technical Field

[0001] This invention relates to the field of electronic component materials technology, specifically to magnetic powder materials for composite inductor fabrication, and more particularly to a method for preparing high-temperature magnetic slurry for inductors that can be low-pressure molded. Background Technology

[0002] Composite inductors, as core components in electronic devices for energy storage, signal filtering, and electromagnetic interference suppression, are widely used in various electronic terminal products such as new energy vehicles, smartphones, AI servers, and smart homes. As electronic devices develop towards miniaturization, lightweighting, and high power density, higher requirements are placed on the size, magnetic properties, and molding process compatibility of composite inductors.

[0003] As the core functional material of composite inductors, the molding performance of magnetic powder directly determines the manufacturing efficiency, product qualification rate, and overall performance of composite inductors. Currently, the molding process for magnetic powder used in composite inductors mostly adopts high-pressure pressing, which has many drawbacks: on the one hand, high-pressure molding requires extremely high mold strength, and long-term use can easily lead to mold wear and deformation, increasing the maintenance and replacement costs of production equipment; on the other hand, the high-pressure molding process can easily squeeze the coil, causing coil deformation or insulation layer damage. At the same time, high pressure can easily cause internal stress in the composite inductor core, which can lead to core cracking, making it difficult to meet the manufacturing requirements of composite inductors with complex structures.

[0004] To improve molding performance, existing technologies have attempted to modify magnetic powder by adding binders. However, conventional binders suffer from poor flowability and incompatible compatibility with magnetic powder, resulting in uneven coating and requiring high pressure during molding to ensure product density. Furthermore, the magnetic powders used in current low-pressure pressing processes generally suffer from insufficient flowability under hot pressing, making them unsuitable for molding complex inductor structures. This leads to defects such as powder shortages, incomplete molding, or core cracking, further affecting the structural stability and magnetic properties of composite inductors. Therefore, developing a high-temperature magnetic slurry for inductors that combines good hot-pressing flowability, adaptability to complex structural molding, stable molding under low pressure, and guarantees high permeability and low loss has become a pressing technical problem in the field of electronic materials. Summary of the Invention

[0005] To address the aforementioned drawbacks of low-pressure molding of magnetic slurry for inductors, such as insufficient fluidity, low magnetic density, and unstable magnetic properties, this invention provides a method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure. Through a two-step coating process using a homogenizer, the compatibility and dispersibility between the magnetic powder and the organic phase are improved. The adhesive formulation used transforms into a viscous magnetic slurry at high temperature, exhibiting high fluidity and rapid curing, enabling stable molding under low pressure, and resulting in good magnetic properties and processability.

[0006] This invention is achieved through the following technical solution: A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure, specifically including the following steps: Step S1, Material preparation: Prepare 1000 parts by weight of soft magnetic alloy powder, 10-70 parts by weight of thermosetting resin, 1-15 parts by weight of silane coupling agent, 20-50 parts by weight of diluent, 10-20 parts by weight of curing agent, and 30-100 parts by weight of solvent. Step S2: Mix the coupling agent and diluent, add them to the magnetic powder, and stir to complete the pretreatment. Step S3: The resin and curing agent are dissolved in the solution. The pretreated magnetic powder and resin solution are uniformly coated by high-shear stirring in a homogenizer. The target magnetic powder is obtained by granulation and drying.

[0007] Preferably, the soft magnetic alloy powder includes at least one or a combination of two of FeNi, FeSiAl, or FeNiMo.

[0008] The particle size D50 is 1~15μm.

[0009] Preferably, the coupling agent includes at least one or a combination of two of silane coupling agents, aluminate coupling agents, or phthalate coupling agents.

[0010] Preferably, the diluent includes at least one or a combination of two of ethanol, ethylene glycol, or glycerol.

[0011] Preferably, the mass ratio of the diluent to the coupling agent is 20:(1~3).

[0012] Preferably, in step S2, the mixing time of the magnetic powder in the homogenizer is 30~180 s, and the rotation speed is 1000~1500 rpm.

[0013] Preferably, the thermosetting resin includes at least one or a combination of two of bisphenol A type epoxy resin, phenolic epoxy resin and modified epoxy silicone resin, in a mass ratio of (40~60):(50~35):(0~15).

[0014] Preferably, the epoxy value of the epoxy resin is in the range of 0.52 to 0.86.

[0015] Preferably, the curing agent includes at least one or a combination of two of 2-ethyl-4-methylimidazole, 1-(3-aminopropyl)imidazole and modified imidazole curing agents, and the curing agent accounts for 2-6% of the total mass of the resin.

[0016] Preferably, the solvent includes at least one or a combination of two of acetone, butanone, ethanol, and propanol.

[0017] Preferably, the mass ratio of the solvent to the thermosetting resin is 2:(1~2).

[0018] Preferably, in step S3, the mixing time of the pretreated magnetic powder and the thermosetting resin solution in the homogenizer is 180~300 s, and the rotation speed is 1000~1500 rpm.

[0019] Preferably, the temperature of the vacuum drying oven is 40°C, the vacuum drying time is 4~6 hours, and the product is then sieved after drying.

[0020] Preferably, the sieve mesh size is 60-100 mesh, and the magnetic powder for low-pressure molding of the composite inductor is obtained by sieving.

[0021] The present invention has the following beneficial effects: Pre-treating magnetic powder with a coupling agent can form a uniform molecular layer on the surface of the magnetic powder, enhancing its interaction with organic molecules in the adhesive solution, improving dispersibility and reducing eddy current loss. A specific ratio of epoxy resin system can be used to uniformly coat the magnetic powder with a high-speed rotating homogenizer. After heating, it can be transformed into a viscous flow state, giving the magnetic powder excellent thermo-pressure flowability. Pressing can increase the magnetic density, and it can be quickly cured with a curing agent. It can be stably molded under low pressure of 30~50 MPa, avoiding coil damage and core cracking, and is suitable for the preparation of complex composite inductors. Detailed Implementation

[0022] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0024] Example 1 A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure includes the following steps: Step S1: Material preparation. Weigh a predetermined amount of soft magnetic alloy powder, with a predetermined mass of 1.0 kg, wherein the mass ratio of FeNi to FeSiAl is 70:30, the D50 of FeNi powder is 15 μm, and the D50 of FeSiAl powder is 1.5 μm; 2.0 g of silane coupling agent; 40 mL of ethanol as diluent; 30 g of thermosetting resin, wherein the mass ratio of bisphenol A epoxy resin, phenolic epoxy resin, and modified epoxy silicone resin is 50:40:10, and the average epoxy value is 0.79; 1.2 g of imidazole curing agent; and 50 g of acetone as solvent.

[0025] In step S2, the silane coupling agent is dissolved in the diluent ethanol. The magnetic powder and silane coupling agent are then poured into a homogenizer and mixed at high speed. The homogenizer speed is set to 1500 rpm for 30 seconds to obtain a mud-like magnetic slurry.

[0026] In step S3, the thermosetting resin and curing agent are dissolved in a solution. The resin and curing agent solution is poured into a homogenizer and mixed with the magnetic slurry at high speed. The homogenizer speed is set to 1500 rpm for 180 s to obtain a mud-like magnetic slurry. The slurry is granulated using a 60-mesh sieve, and the granulated powder is then placed in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40°C, and the vacuum drying time is 4 h. The dried magnetic powder is then sieved using a 60-mesh sieve to obtain the target magnetic powder.

[0027] Magnetic powder was pressed into magnetic rings at 30 MPa, and then baked at 180°C for 1 hour before testing their electrical and mechanical properties. The powder was then filled into a pre-wound composite inductor core, pressed and baked at a hot-pressing temperature of 140°C and a pressure of 50 MPa, and sliced ​​to observe cracking.

[0028] Tests showed that the magnetic powder prepared in this example had a permeability of 20.60, a baking strength of 88.1 N, no cracking when pressed into a magnetic core, and no cracks when sliced.

[0029] Example 2 A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure includes the following steps: Step S1: Material preparation. Weigh a predetermined mass of soft magnetic alloy powder, 1.0 kg, wherein the mass ratio of FeNi to FeSiAl is 70:30, the D50 of FeNi powder is 15 μm, and the D50 of FeSiAl powder is 1.5 μm; 2.0 g of silane coupling agent; 40 mL of ethanol as diluent; 50 g of thermosetting resin, wherein the mass ratio of bisphenol A epoxy resin, phenolic epoxy resin, and modified epoxy silicone resin is 50:40:10, with an average epoxy value of 0.79; 1.2 g of imidazole curing agent; and 50 g of acetone as solvent. The only difference between this embodiment and Example 1 is that the mass of the thermosetting resin is adjusted to 50 g.

[0030] In step S2, the silane coupling agent is dissolved in the diluent ethanol. The magnetic powder and silane coupling agent are then poured into a homogenizer and mixed at high speed. The homogenizer speed is set to 1500 rpm for 30 seconds to obtain a mud-like magnetic slurry.

[0031] In step S3, the thermosetting resin and curing agent are dissolved in a solution. The resin and curing agent solution is poured into a homogenizer and mixed with the magnetic slurry at high speed. The homogenizer speed is set to 1500 rpm for 180 seconds to obtain a mud-like magnetic slurry. The slurry is then granulated using a 60-mesh sieve. The granulated powder is placed in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40°C, and the vacuum drying time is 4 hours. The dried magnetic powder is then sieved using a 60-mesh sieve to obtain the target magnetic powder.

[0032] Magnetic powder was pressed into magnetic rings at 30 MPa, and then baked at 180°C for 1 hour before testing their electrical and mechanical properties. The powder was then filled into a pre-wound composite inductor core, pressed and baked at a hot-pressing temperature of 140°C and a pressure of 50 MPa, and sliced ​​to observe cracking.

[0033] Tests showed that the magnetic powder prepared in this example had a permeability of 20.71, a baking strength of 108.8 N, no cracking when pressed into a magnetic core, and no cracks when sliced.

[0034] Example 3 A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure includes the following steps: Step S1: Material preparation. Weigh a predetermined mass of soft magnetic alloy powder, 1.0 kg, wherein the mass ratio of FeNi to FeSiAl is 70:30, the D50 of FeNi powder is 15 μm, and the D50 of FeSiAl powder is 1.5 μm; 2.0 g of silane coupling agent; 40 mL of ethanol as diluent; 30 g of thermosetting resin, wherein the mass ratio of bisphenol A epoxy resin, phenolic epoxy resin, and modified epoxy silicone resin is 80:10:10, with an average epoxy value of 0.63; 1.2 g of imidazole curing agent; and 50 g of acetone as solvent. The only difference between this embodiment and Example 1 is that the mass ratio of bisphenol A epoxy resin, phenolic epoxy resin, and modified epoxy silicone resin is adjusted to 80:10:10.

[0035] In step S2, the silane coupling agent is dissolved in the diluent ethanol. The magnetic powder and silane coupling agent are then poured into a homogenizer and mixed at high speed. The homogenizer speed is set to 1500 rpm for 30 s to obtain a mud-like magnetic slurry.

[0036] In step S3, the thermosetting resin and curing agent are dissolved in a solution. The resin and curing agent solution is poured into a homogenizer and mixed with the magnetic slurry at high speed. The homogenizer speed is set to 1500 rpm for 180 s to obtain a mud-like magnetic slurry. The slurry is granulated using a 60-mesh sieve, and the granulated powder is then placed in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40°C, and the vacuum drying time is 4 h. The dried magnetic powder is then sieved using a 60-mesh sieve to obtain the target magnetic powder.

[0037] Magnetic powder was pressed into magnetic rings at 30 MPa, and then baked at 180°C for 1 h before testing their electrical and mechanical properties. The powder was then filled into a pre-wound composite inductor core, pressed and baked at a hot-pressing temperature of 140°C and a pressure of 50 MPa, and sliced ​​to observe cracking.

[0038] The magnetic powder prepared in this example has a permeability of 22.16, a baking strength of 105.9 N, and the magnetic core does not crack when pressed. The slice has a slight crack (2 / 4) in the middle of the magnetic core.

[0039] Comparative Example 1 - No Coupling Agent Pretreatment A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure includes the following steps: Step S1: Material preparation. Weigh a predetermined amount of soft magnetic alloy powder, with a predetermined mass of 1.0 kg, wherein the mass ratio of FeNi to FeSiAl is 70:30, the D50 of FeNi powder is 15 μm, and the D50 of FeSiAl powder is 1.5 μm; 0 g of silane coupling agent; 40 mL of ethanol as diluent; 30 g of thermosetting resin, wherein the mass ratio of bisphenol A epoxy resin, phenolic epoxy resin, and modified epoxy silicone resin is 60:30:10, with an average epoxy value of 0.79; 1.2 g of imidazole curing agent; and 50 g of acetone as solvent. The only difference between this comparative example and Example 1 is that the silane coupling agent is not added.

[0040] In step S2, the silane coupling agent is dissolved in the diluent ethanol. The magnetic powder and silane coupling agent are then poured into a homogenizer and mixed at high speed. The homogenizer speed is set to 1500 rpm for 30 seconds to obtain a mud-like magnetic slurry.

[0041] In step S3, the thermosetting resin and curing agent are dissolved in a solution. The resin and curing agent solution is poured into a homogenizer and mixed with the magnetic slurry at high speed. The homogenizer speed is set to 1500 rpm for 180 s to obtain a mud-like magnetic slurry. The slurry is granulated using a 60-mesh sieve, and the granulated powder is then placed in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40°C, and the vacuum drying time is 4 h. The dried magnetic powder is then sieved using a 60-mesh sieve to obtain the target magnetic powder.

[0042] Magnetic powder was pressed into magnetic rings at 30 MPa, and then baked at 180°C for 1 h before testing their electrical and mechanical properties. The powder was then filled into a pre-wound composite inductor core, pressed and baked at a hot-pressing temperature of 140°C and a pressure of 50 MPa, and sliced ​​to observe cracking.

[0043] Tests showed that the magnetic powder prepared in this example had a permeability of 16.93, a baking strength of 58.1 N, no cracking when pressed into a magnetic core, and a transverse crack (4 / 4) in the middle of the slice in the inductor.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-temperature magnetic slurry for inductors that can be molded under low pressure, characterized in that, Includes the following steps: Step S1, Material preparation: Prepare 1000 parts by weight of soft magnetic alloy powder, 10-70 parts by weight of thermosetting resin, 1-15 parts by weight of silane coupling agent, 20-50 parts by weight of diluent, 10-20 parts by weight of curing agent, and 30-100 parts by weight of solvent. Step S2: Mix the coupling agent and diluent, add them to the magnetic powder, and stir to complete the pretreatment. Step S3: The resin and curing agent are dissolved in the solution. The pretreated magnetic powder and resin solution are uniformly coated by high-shear stirring in a homogenizer. The target magnetic powder is obtained by granulation and drying.

2. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, the soft magnetic alloy powder includes at least one or a combination of two of FeNi, FeSiAl or FeNiMo, and the particle size D50 is 1~15μm.

3. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, the coupling agent includes at least one or a combination of two of silane coupling agents, aluminate coupling agents, or phthalate coupling agents.

4. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, wherein the diluent comprises at least one or a combination of two of ethanol, ethylene glycol or glycerol, and the mass ratio of the diluent to the coupling agent is 20:(1~3).

5. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, the thermosetting resin includes at least one or a combination of two of bisphenol A type epoxy resin, phenolic epoxy resin and modified epoxy silicone resin, with a mass ratio of (40~60):(50~35):(0~15), and the epoxy value is in the range of 0.52~0.

86.

6. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, the curing agent includes at least one or a combination of two of 2-ethyl-4-methylimidazole, 1-(3-aminopropyl)imidazole and modified imidazole curing agents, and the curing agent accounts for 2 to 6% of the total mass of the resin.

7. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S1, wherein the solvent includes at least one or a combination of two of acetone, butanone, ethanol, and propanol, and the mass ratio of the solvent to the thermosetting resin is 2:(1~2).

8. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, In step S2, the magnetic powder is pretreated in a homogenizer for 30-180 seconds and the rotation speed is 1000-1500 rpm.

9. The method for preparing the low-pressure moldable high-temperature magnetic slurry for inductors according to claim 1, characterized in that, Step S3: The mixing time of the pretreated magnetic powder and the thermosetting resin solution in the homogenizer is 180~300 s, and the rotation speed is 1000~1500 rpm.