WO2022077150A1

WO2022077150A1 - Magnetic composite material and preparation method therefor, and inductor and manufacturing method therefor

Info

Publication number: WO2022077150A1
Application number: PCT/CN2020/120331
Authority: WO
Inventors: 郭峰; 付邦良; 汪贤
Original assignee: 昆山磁通新材料科技有限公司
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2022-04-21

Abstract

A magnetic composite material and a preparation method therefor, and an inductor and a manufacturing method therefor, relating to the technical field of semiconductors. The magnetic composite material comprises a soft magnetic metal material and an adhesive; the soft magnetic metal material and the adhesive are mixed at a preset ratio; the relative density of the soft magnetic metal material is greater than or equal to 0.5; and the relative density is represented by the following formula, wherein ρ' is the relative density of the soft magnetic metal material, ρbt is the tap density of the soft magnetic metal material, and ρ is the real density of the soft magnetic metal material. When the magnetic composite material is placed in a mold for pressing, since the relative density of the soft magnetic metal material is greater than or equal to 0.5, in an actual pressing process, large pressure is not needed, and the magnetic composite material has high forming density only by means of small pressure, thereby avoiding the problem that the magnetic composite material is damaged due to large pressure.

Description

Magnetic composite material and preparation method thereof, inductor and preparation method thereof

technical field

The present application relates to the technical field of semiconductors, and more particularly to a magnetic composite material and a preparation method thereof, an inductor and a preparation method thereof.

Background technique

As one of the main passive components around the chip, inductors are widely used in various intelligent hardware systems, such as smart phones, smart TVs, smart home appliances, tablet computers, notebook computers, various communication terminals and servers, etc. Its main function is electromagnetic signals. and energy conversion, storage and filtering.

A traditional inductor includes a coil and a magnetic body covering the coil. The manufacturing process is generally that the coil is placed in a mold, and the empty space inside and around the coil is filled with metal soft magnetic powder and pressed into shape. In the above pressing process, in order to ensure the stability of the structure, the pressing pressure is often large, which can reach 500MPa, 600MPa, 800MPa, or even higher. However, such a high pressing pressure often damages the metal soft magnetic powder and the internal coil structure, resulting in problems such as overall deformation of the coil structure, which in turn causes problems such as attenuation of the initial voltage withstand capability of the coil, short-circuiting of the inductance, etc., reducing the reliability of the inductance.

SUMMARY OF THE INVENTION

The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

According to various embodiments of the present application, a magnetic composite material and a preparation method thereof, an inductor and a preparation method thereof are provided.

According to an aspect of the present application, a magnetic composite material is provided, comprising a soft magnetic metal material and a binder, wherein the soft magnetic metal material and the binder are mixed in a preset ratio, the soft magnetic metal material The relative density of the material is greater than or equal to 0.5, and the relative density is represented by the following formula:

Wherein, ρ' is the relative density of the soft magnetic metal material, ρ _bt is the tap density of the soft magnetic metal material, and ρ is the true density of the soft magnetic metal material.

In one of the embodiments, the weight percentage of the soft magnetic metal material in the magnetic composite material is greater than or equal to 92% and less than or equal to 97%, and the weight percentage of the adhesive in the magnetic composite material The weight percentage is greater than or equal to 3% and less than or equal to 8%.

In one embodiment, the soft magnetic metal material includes a mixture of several materials with different particle sizes, and the ratio of the largest particle size to the smallest particle size among the particle sizes of the several materials is less than or equal to 8.

In one embodiment, the soft magnetic metal material includes carbonyl iron powder, reduced iron powder, atomized iron powder, atomized Fe _(100-xy) _SixCry powder, _atomized iron-based amorphous soft magnetic powder , A mixture of atomized iron-based amorphous nanocrystalline powder, atomized iron-silicon-aluminum alloy powder and atomized iron-nickel alloy powder, wherein 3.5≤x≤6.5, 0≤y≤6.5.

In one embodiment, the surface of the soft magnetic metal material has an insulating film, and the insulating film includes phosphate, silicate, borate, chromate, permanganate, nitrate and aluminum One or more complex salts of acid salts.

In one embodiment, the adhesive comprises any one or a mixture of two or more of epoxy resin, phenolic resin, cyanate ester resin, bismaleimide resin and silicone resin, or the above One or a mixture of two or more modified resin materials.

In one embodiment, the molding density of the magnetic composite material is greater than or equal to 5 g/cm ³ and less than or equal to 6.2 g/cm ³ .

According to another aspect of the present application, a preparation method of the above-mentioned magnetic composite material is provided, comprising:

Mix several soft magnetic metal powder materials with different particle sizes to prepare a soft magnetic metal material with a relative density greater than or equal to 0.5, wherein the largest particle size and the smallest particle size among the particle sizes of the several materials are different. The ratio is less than or equal to 8;

The soft magnetic metal material and the binder are mixed in a preset ratio to form a magnetic composite material.

In one embodiment, before the step of mixing the soft magnetic metal material and the binder in a preset ratio to form a magnetic composite material, the preparation method of the magnetic composite material further includes:

Surface modification treatment is performed on the soft magnetic metal material to form an insulating film on the surface of the soft magnetic metal material, and the insulating film includes phosphate, silicate, borate, chromate, high One or more complex salts of manganate, nitrate and aluminate.

In one embodiment, after the step of mixing the soft magnetic metal material and the binder in a preset ratio to form a magnetic composite material, the preparation method of the magnetic composite material further includes:

The magnetic composite material is made into a feed, and the form of the feed includes any one or more of irregular powder, cake and viscous fluid.

According to yet another aspect of the present application, an inductor is provided, comprising a coil and a magnetic body covering the coil, and the magnetic body is made of the above-mentioned magnetic composite material.

According to another aspect of the present application, a method for manufacturing an inductor is provided, comprising:

Winding wires to form coils;

placing the coil in a mold;

Filling the mold with the magnetic composite material as described above;

applying a predetermined pressure into the mold to cause the magnetic composite to flow and form a magnetic body surrounding the coil, the predetermined pressure being less than the plastic deformation strength of the magnetic composite and the plastic deformation of the coil strength.

In one embodiment, the shape of the magnetic body includes a rectangular parallelepiped or an elliptical cylinder.

In one embodiment, both ends of the coil are connected to electrode sheets respectively, and the connection between the two ends of the coil and the electrode sheets includes any one of welding, solder paste sintering and electroplating. .

In one embodiment, the preset pressure is greater than or equal to 1.0 MPa and less than or equal to 15 MPa.

In the preparation process of the above-mentioned inductor, a magnetic composite material composed of a soft magnetic metal material with a relative density of 0.5 or more is used as the pressing material, so that it is not necessary to use too high pressing pressure during pressing, and the plastic deformation strength of the magnetic composite material is smaller than that of the magnetic composite material. And the pressure of the plastic deformation strength of the coil is used to press the magnetic composite material, so as to ensure that the magnetic composite material after pressing has sufficient molding density, and at the same time avoid the deformation or stress of the magnetic composite material and the internal coil structure caused by excessive pressure. It can prevent the short circuit of the inductance and the attenuation of the initial withstand voltage of the coil, and improve the reliability of the inductance.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the present application will become apparent from the description, drawings and claims.

Description of drawings

In order to better describe and illustrate embodiments or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be construed as limiting the scope of any of the disclosed inventions, the presently described embodiments or examples, and the best mode presently understood of these inventions.

Fig. 1 is a flow chart of an embodiment of a method for preparing a magnetic composite material provided in an embodiment of the present application;

Fig. 2 is a flowchart of another embodiment of the preparation method of the magnetic composite material provided by the embodiment of the application;

FIG. 3 is a flowchart of a method for manufacturing an inductor provided by an embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for the purpose of illustration only and do not represent the only embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the application are for the purpose of describing specific embodiments only, and are not intended to limit the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

With the gradual development and integration of network technology, computer technology, communication technology, and artificial intelligence technology, human beings have entered the era of the fourth industrial revolution; the main feature of this era is that people and people, things and things, and people and things are closely established Therefore, new lifestyles such as smart phones, smart homes, and smart cities have emerged. With the gradual breakthrough of related bottleneck technologies, there will be intelligent transportation (including Internet cars, smart parking, etc.), AI robots, and even Sooner or later, the AI robot society, the intelligence of agriculture and industry, and the related Internet of Things will appear. These complex connections all depend on the transmission, communication and processing of information by the hardware system, which can be the transmitting end of the information, the receiving end of the information and the cloud. The key to intelligent hardware is the chip and related components.

Among them, inductors (such as power inductors), as one of the main passive components around the chip, are widely used in various intelligent hardware systems, such as smart phones, smart TVs, smart home appliances, tablet computers, notebook computers, various communication terminals and servers, etc. , its main function lies in the conversion, storage and filtering of electromagnetic signals and energy. Power inductors include coil windings. The coil windings are preset in the mold, and the empty space inside and around the windings is filled and formed by metal soft magnetic powder, and then the inductor structure is obtained. Magnetic structure.

However, in the existing process of pressing the metal soft magnetic powder, in order to increase the molding density of the metal soft magnetic powder, a higher pressure, such as 500 MPa or 600 MPa or 800 MPa, or even higher, is often used for pressing. Although such a high pressure can ensure that the forming density of the metal soft magnetic powder is high enough, it is easy to cause damage to the metal soft magnetic powder itself and the coil structure inside it, so that the coil structure is deformed as a whole, and the wire cross-sectional area of the coil is formed. Deformation and scratches, which in turn lead to the attenuation of the initial voltage withstand capability of the coil and the short circuit of the inductance, reducing the reliability of the inductance.

In order to solve the above problems, the present application provides a magnetic composite material and a preparation method thereof, an inductor and a preparation method thereof.

The magnetic composite material provided in the embodiment of the present application includes a soft magnetic metal material and a binder, the soft magnetic metal material and the binder are mixed in a preset ratio, and the relative density of the soft magnetic metal material is greater than or equal to 0.5, and the relative consistency Density is expressed by the following formula:

The mixing of the soft magnetic metal material and the binder can make the soft magnetic metal material have a certain fluidity, so that the magnetic composite material formed by mixing can be used in a pressing process.

The tap density refers to the mass of the unit volume measured after the powder in the container is tapped under the specified conditions, and the true density refers to the actual mass of the solid substance per unit volume of the material in an absolutely dense state, that is, the removal of Density after internal voids or voids between particles. This application defines the ratio of tap density to true density as the relative density of the soft magnetic metal material. The higher the relative density, the higher the compaction density of the soft magnetic metal material. Correspondingly, when the magnetic composite material is placed in When pressing in a mold, the filling rate is higher. The relative density of the soft magnetic metal material in this application is greater than or equal to 0.5. In actual pressing, it is not necessary to use a large pressure, and only a small pressure can make the magnetic composite material have a high molding density, avoiding the The larger pressure causes the magnetic composite material itself to be damaged and other problems.

Wherein, the relative density of the soft magnetic metal material may be 0.5 or 0.6 or 0.7 or the like.

The preset mixing ratio of the soft magnetic metal material and the binder is not unique. The mixing ratio of the two can be comprehensively considered from two aspects, one is the fluidity of the mixed magnetic composite material, and the other is the magnetic composite material after mixing. Inductive performance. In one embodiment, the weight percentage of the soft magnetic metal material in the magnetic composite material is greater than or equal to 92% and less than or equal to 97%, and the weight percentage of the adhesive in the magnetic composite material is greater than or equal to 3% and less than or equal to 97%. is equal to 8%. By mixing the soft magnetic metal material and the binder in the above mixing ratio, the prepared magnetic composite material can be compatible with both good fluidity and excellent inductance performance.

For example, the weight percentage of the soft magnetic metal material in the magnetic composite material is 92%, the weight percentage of the binder in the magnetic composite material is 8%, or the weight percentage of the soft magnetic metal material in the magnetic composite material is 8%. The weight percentage is 95%, the weight percentage of the adhesive in the magnetic composite material is 5%, or the weight percentage of the soft magnetic metal material in the magnetic composite material is 97%, and the adhesive agent is in the magnetic composite material. The weight percentage is 3%. Of course, auxiliary materials such as related coupling agents or toughening agents or leveling agents can also be added to the magnetic composite material to optimize the mixing effect between the metal magnetic material and the adhesive or the flexibility of the magnetic composite material. For example, the magnetic composite material also contains a toughening agent, a leveling agent, a mold release agent, etc. At this time, the weight percentage of the soft magnetic metal material in the magnetic composite material can be 95%, and the adhesive is in the magnetic composite material. The weight percentage of the material can be 3%, and the weight percentage of other adjuvants in the magnetic composite material can be 2%. Of course, there are other distribution methods, which are not listed here, as long as the weight percentage of the binder in the magnetic composite material is between 92% and 97%, and the weight percentage of the binder in the magnetic composite material is between 92% and 97%. Between 3%-8% can be.

In one embodiment, the soft magnetic metal material includes a mixture of several materials with different particle sizes, and the ratio of the largest particle size to the smallest particle size among the particle sizes of the several materials is less than or equal to 8. That is, in the present application, the soft magnetic metal material includes a variety of materials with different particle sizes. When materials with different particle sizes are mixed, a higher tap density can be achieved, thereby increasing the relative density. Moreover, the applicant found that when the ratio of the maximum particle size to the minimum particle size in the particle sizes of several materials in the mixture is limited to 8 or less, such as 8 or 7 or 6, the tap density can be maintained at a higher value.

In this embodiment, the particle sizes of several mixed materials in the soft magnetic metal material are all between 10 microns and 80 microns.

In one embodiment, the soft magnetic metal material includes carbonyl iron powder, reduced iron powder, atomized iron powder, atomized Fe _(100-xy) _SixCry powder, _atomized iron-based amorphous soft magnetic powder, atomized iron powder, atomized iron powder A mixture of several kinds of iron-based amorphous nanocrystalline powder, atomized iron-silicon-aluminum alloy powder and atomized iron-nickel alloy powder, wherein 3.5≤x≤6.5, 0≤y≤6.5. For example, the soft magnetic metal material may include carbonyl iron powder, reduced iron powder, and a mixture of atomized iron powder, and may also include carbonyl iron powder, reduced iron powder, atomized iron powder, and atomized Fe _(100-xy) _Six Cr The mixture of _y powder (x=4, y=5) can also include reduced iron powder, atomized iron-based amorphous soft magnetic powder, atomized iron-based amorphous nanocrystalline powder, atomized iron-silicon-aluminum alloy powder and mist Mixtures of iron-nickel alloy powders, etc., are not listed here.

In one embodiment, the surface of the soft magnetic metal material has an insulating film, and the insulating film includes one of phosphate, silicate, borate, chromate, permanganate, nitrate and aluminate. one or two or more complex salts. The insulating film can be directly coated on the surface of the soft magnetic metal material by physical coating, or it can be chemically reacted with the surface of the soft magnetic metal material, so as to modify the surface of the soft magnetic metal material to form an insulating film. . The insulating film is a covalent bond or ionic bond compound, so it has good insulating properties and heat resistance. When the magnetic composite material is applied to the inductor structure, the insulating film can meet the requirements of heat aging and resistance during the use of the inductor. voltage breakdown requirements.

It should be noted that due to the relatively high relative density of soft magnetic metal materials, in the pressing process, only a small pressure can be used to make the magnetic composite material have a high molding density, in addition to preventing the magnetic composite material itself In addition to being damaged by a large pressure, the insulating film structure on the surface of the soft magnetic metal material can also be prevented from being damaged.

In one embodiment, the thickness of the insulating film is less than or equal to 50 nanometers.

In one embodiment, the adhesive includes any one or a mixture of two or more of epoxy resin, phenolic resin, cyanate ester resin, bismaleimide resin and silicone resin, or each of the above resin materials One or a mixture of two or more of the modifiers.

In one of the embodiments, the molding density of the magnetic composite material is greater than or equal to 5 g/cm ³ and less than or equal to 6.2 g/cm ³ . For example, in the process of pressing the magnetic composite material for the inductor, on the basis of ensuring a sufficiently high molding density, the pressing pressure on the magnetic composite material can be further reduced, the damage and deformation of the magnetic composite material during the pressing process can be reduced, and Reduce the amount of deformation of the coil covered by the magnetic composite material.

1, the preparation method of the magnetic composite material provided in the embodiment of the present application includes the following steps:

Step S20, mixing several kinds of soft magnetic metal powder materials with different particle sizes to prepare a soft magnetic metal material with a relative density greater than or equal to 0.5, wherein the largest particle size and the smallest particle size among the particle sizes of several materials The ratio is less than or equal to 8.

Step S22, mixing the soft magnetic metal material and the adhesive in a preset ratio to form a magnetic composite material.

In the above preparation method, since the soft magnetic metal material and the binder are mixed, the prepared magnetic composite material has certain fluidity and can be used in the pressing process. In addition, since the relative density of the prepared soft magnetic metal material is greater than or equal to 0.5, when the magnetic composite material is used in the pressing process, only a small pressing pressure is needed to make the magnetic composite material have a higher molding capacity. Density, to avoid problems such as damage or deformation of the magnetic composite material itself due to large pressure.

In one embodiment, in step S20, when the soft magnetic metal powder materials of different particle sizes are mixed, a higher tap density can be achieved, thereby improving the relative density. Moreover, the applicant found that when the ratio of the maximum particle size to the minimum particle size in the particle sizes of several soft magnetic metal powder materials in the mixture is limited to be less than or equal to 8, such as 8 or 7 or 6, the tap density can be maintained at Higher values, i.e. greater than or equal to 0.5.

In one of the embodiments, the particle sizes of several soft magnetic metal powder materials in the soft magnetic metal material are all between 10 microns and 80 microns.

For the content of the relative density, reference may be made to the relevant description of the aforementioned magnetic composite material, which will not be repeated here.

In one embodiment, in step S20, carbonyl iron powder, reduced iron powder, atomized iron powder, atomized Fe _(100-xy) Si _x C _y powder, atomized iron-based amorphous soft magnetic powder can be mixed , atomized iron-based amorphous nanocrystalline powder, atomized iron-silicon-aluminum alloy powder and atomized iron-nickel alloy powder are mixed to prepare a soft magnetic metal material, wherein 3.5≤x≤6.5, 0≤y≤ 6.5. When selecting the above materials, it is necessary to meet the requirements that the particle sizes are not all the same, and the ratio of the maximum particle size to the minimum particle size is less than or equal to 8.

In one embodiment, in step S22, the weight percentage of the binder in the mixture may be greater than or equal to 3% and less than or equal to 8%, and the weight percentage of the soft magnetic metal material in the mixture may be greater than or equal to 92% and Less than or equal to 97%. When the soft magnetic metal material and the binder are mixed uniformly, the desired magnetic composite material can be prepared.

Wherein, the adhesive includes epoxy resin, phenolic resin, cyanate ester resin, bismaleimide resin and silicone resin, any one or a mixture of two or more, or a modified product of the above resin materials one or a mixture of two or more.

2, in one embodiment, after step S20 and before step S22, the preparation method of the magnetic composite material provided by the present application further includes the following steps:

Step S21, performing surface modification treatment on the soft magnetic metal material to form an insulating film on the surface of the soft magnetic metal material, the insulating film includes phosphate, silicate, borate, chromate, permanganate One or more complex salts of , nitrate and aluminate.

The purpose of surface modification treatment of soft magnetic metal material is to form an insulating film on its surface. A chemical reaction occurs on the surface of the magnetic metal material, so that an insulating film is formed after the surface of the soft magnetic metal material is modified. The insulating film is a covalent bond or ionic bond compound, so it has good insulating properties and heat resistance. When the magnetic composite material is applied to the inductor structure, the insulating film can meet the requirements of heat aging and resistance during the use of the inductor. voltage breakdown requirements.

2, in one embodiment, after step S22, the following steps are further included:

Step S24 , making the magnetic composite material into a feed, and the form of the feed includes any one or more of irregular powder, cake and viscous fluid.

The molding density of the magnetic composite material prepared by the above preparation method is greater than or equal to 5 g/cm ³ and less than or equal to 6.2 g/cm ³ .

The inductor provided by the embodiment of the present application includes a coil and a magnetic body covering the coil, and the magnetic body is made of the aforementioned magnetic composite material.

Since the relative density of the soft magnetic metal material in the magnetic composite material is greater than or equal to 0.5, when it presses the magnetic composite material, it is not necessary to use a large pressure, only a small pressure can make the magnetic composite material have higher It can avoid the problems such as damage or deformation of the magnetic composite material and the coil structure covered by the large pressure, thereby preventing the occurrence of short circuit of the inductance and the attenuation of the initial withstand voltage of the coil, and improving the reliability of the inductance. sex.

In one of the embodiments, the coil is an air-core coil with an iron core central column inside, that is, the coil is arranged around the iron core central column. Preferably, the height of the central column of the iron core is greater than or equal to the height of the coil and less than or equal to 80% of the height of the magnetic body.

In one of the embodiments, the center column of the iron core is prepared by using the above-mentioned magnetic composite material, and can also be prepared by using other magnetic composite materials, which is not specifically limited here.

As an alternative embodiment, the center column of the iron core is made of a soft magnetic metal material, which may be a ferrosilicon magnetic powder core, an amorphous magnetic powder core, a ferrosilicon aluminum magnetic powder core, or the like.

In this embodiment, the compressive fracture strength of the central column of the iron core is greater than or equal to 15MPa, and the deformation amount is between 0.1% and 1%.

In one embodiment, the coil is wound by enameled wire, and the outermost enameled wire of the coil is coated with hot-melt glue, and the function of the hot-melt glue is to shape the wound part of the coil when the coil is wound.

In one embodiment, two ends of the coil are respectively connected to corresponding external electrodes, and the external electrodes extend out of a magnetic body to serve as external connection terminals of the inductor.

Referring to FIG. 3 , the preparation method of the inductor provided by the embodiment of the present application includes the following steps:

Step S40, winding a wire to form a coil.

Step S42, placing the coil in the mold.

Step S44, filling the magnetic composite material into the mold.

Step S46 , applying a preset pressure to the mold to make the magnetic composite material flow and form a magnetic body covering the coil, the preset pressure being less than the plastic deformation strength of the magnetic composite material and the plastic deformation strength of the coil.

Since the magnetic composite material composed of soft magnetic metal material with a relative density greater than or equal to 0.5 is used as the pressing material, it is not necessary to use too high pressing pressure during pressing, and the plastic deformation strength of the magnetic composite material and the plastic deformation strength of the coil are smaller than that of the magnetic composite material. Pressing the magnetic composite material at a high pressure can ensure that the magnetic composite material after compression molding has sufficient molding density, and at the same time avoid the deformation or damage of the magnetic composite material and the internal coil structure caused by excessively high pressure, and prevent inductance short circuit, The initial withstand voltage capability of the coil is attenuated, which improves the reliability of the inductor.

In step S40, the wire may include a metal wire and an insulating layer (enameled wire) covering the metal wire, and the metal wire may include any one of copper wire, aluminum wire, aluminum alloy, and copper alloy. In addition, the cross-sectional shape of the coil may be circular, oval, rectangular, or the like.

In one embodiment, before step S40, the iron core center post may also be prepared in advance. Specifically, the above-mentioned magnetic composite material can be used to prepare the core column, or the soft magnetic metal material in the magnetic composite material can be used. When the magnetic composite material is used to prepare the iron core central column, the forming pressure of the iron core central column is between 400-1500 MPa, and the higher the pressure, the higher the magnetic permeability, the higher the strength and density, and the curing is performed as needed after forming. After treatment, the iron core center column is finally obtained.

When the center post of the iron core is prepared, in step S40, the coil can be wound around the center post of the iron core. The center column of the iron core is arranged inside the coil, which helps to reduce the deformation of the coil in the subsequent pressing process.

In one embodiment, after step S40, it further includes:

Step S41, coating hot melt adhesive on the outermost periphery of the coil formed by winding. The function of hot melt adhesive is to shape the wound part of the coil when winding the coil.

In one embodiment, in step S42, the coil can be placed in the mold, and at the same time, both ends of the coil can be connected to electrode sheets respectively, and the electrode sheets connected to the two ends are fixed in position, so as to ensure that the coil is far away from the inner wall of the mold. The distance is uniform, and then the mold is closed to form a molding cavity. The connection method between the two ends of the coil and the electrode sheet includes any one of a welding method, a solder paste sintering method and an electroplating method.

It should be noted that the present application adopts the molding transfer molding process to prepare the inductor. Among them, the used mold is divided into an upper mold and an upper mold, and the lower mold has an area for placing coils and a silo for placing magnetic composite materials. In step S42, the coil is placed in the area corresponding to the lower mold of the mold, and in step S44, the magnetic composite material is filled into the silo of the lower mold of the mold.

In step S46, a preset pressure is applied to the magnetic composite material in the silo by using the principle of pressure. At the same time, under the action of heating, the magnetic composite material becomes liquid and flows into the cavity formed by the upper and lower molds until it is squeezed. The mold cavity is filled, and the magnetic composite material completely covers the coil. After that, hold the pressure for 30-180s to cure the thermosetting resin (ie, the adhesive) in the magnetic composite material, thereby forming a magnetic body covering the coil, and finally demolding.

In one of the embodiments, the shape of the finally formed magnetic body may include a rectangular parallelepiped or an elliptical cylinder. Specifically, the top corner of the cuboid may also have a chamfered shape, and the elliptical cylinder may further include a cylindrical shape.

Since the relative density of the magnetic composite material is greater than or equal to 0.5, that is, it has a high relative density, so it is not necessary to use a high pressing pressure during molding, and the molding with a small pressure can satisfy the high density of the magnetic composite material after molding. Density and the need for no damage to magnetic composites and coils.

In one of the embodiments, the preset pressure is greater than or equal to 1 MPa and less than or equal to 15 MPa. In the traditional solution, 500MPa, 600MPa, 800MPa, or even higher pressing pressures are generally used to suppress the inductor, which will undoubtedly cause certain damage to the inductor structure. In this application, since the magnetic composite material with relatively high density is used, the inductor can be formed only with a pressure of less than or equal to 15MPa. It is important that the magnetic composite material and the internal coil structure are not deformed or damaged, preventing the inductor Short circuit, the initial voltage withstand capability of the coil is attenuated, which improves the reliability of the inductor.

The DC withstand voltage of the inductor prepared by the above preparation method can reach more than 1000V/cm.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as a limitation on the scope of the patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the present application should be determined by the appended claims.

Claims

A magnetic composite material, characterized in that it includes a soft magnetic metal material and a binder, wherein the soft magnetic metal material and the binder are mixed in a preset ratio, and the relative density of the soft magnetic metal material is Greater than or equal to 0.5, the relative density is represented by the following formula:

Wherein, ρ' is the relative density of the soft magnetic metal material, ρ bt is the tap density of the soft magnetic metal material, and ρ is the true density of the soft magnetic metal material.
The magnetic composite material according to claim 1, wherein the weight percentage of the soft magnetic metal material in the magnetic composite material is greater than or equal to 92% and less than or equal to 97%, and the adhesive is present in the magnetic composite material. The weight percentage of the magnetic composite material is greater than or equal to 3% and less than or equal to 8%.
The magnetic composite material according to claim 1, wherein the soft magnetic metal material comprises a mixture of several materials with different particle sizes, and the ratio of the largest particle size to the smallest particle size among the particle sizes of the several materials Less than or equal to 8.
The magnetic composite material according to claim 1, wherein the soft magnetic metal material comprises carbonyl iron powder, reduced iron powder, atomized iron powder, atomized Fe (100-xy) Si x C y powder, mist A mixture of several kinds of iron-based amorphous soft magnetic powder, atomized iron-based amorphous nanocrystalline powder, atomized iron-silicon-aluminum alloy powder, and atomized iron-nickel alloy powder, wherein 3.5≤x≤6.5, 0≤y ≤6.5.
The magnetic composite material according to claim 1, wherein the surface of the soft magnetic metal material has an insulating film, and the insulating film comprises phosphate, silicate, borate, chromate, high One or more complex salts of manganate, nitrate and aluminate.
The magnetic composite material according to claim 1, wherein the adhesive comprises any one or both of epoxy resin, phenolic resin, cyanate resin, bismaleimide resin and silicone resin A mixture of one or more kinds, or a mixture of one or two or more of the above-mentioned modified resin materials.
The magnetic composite material according to claim 1, wherein the molding density of the magnetic composite material is greater than or equal to 5.0 g/cm 3 and less than or equal to 6.2 g/cm 3 .
A method for preparing a magnetic composite material as claimed in any one of claims 1-7, characterized in that, comprising:

Mix several soft magnetic metal powder materials with different particle sizes to prepare a soft magnetic metal material with a relative density greater than or equal to 0.5, wherein the largest particle size and the smallest particle size among the particle sizes of the several materials are different. The ratio is less than or equal to 8;

The soft magnetic metal material and the binder are mixed in a preset ratio to form a magnetic composite material.
The method for preparing a magnetic composite material according to claim 8, wherein before the step of mixing the soft magnetic metal material and the binder in a preset ratio to form the magnetic composite material, the magnetic composite material is The preparation method of the material also includes:

Surface modification treatment is performed on the soft magnetic metal material to form an insulating film on the surface of the soft magnetic metal material, and the insulating film includes phosphate, silicate, borate, chromate, high One or more complex salts of manganate, nitrate and aluminate.
The method for preparing a magnetic composite material according to claim 8, wherein the adhesive comprises any one of epoxy resin, phenolic resin, cyanate ester resin, bismaleimide resin and silicone resin One or a mixture of two or more, or a mixture of one or two or more of the above-mentioned modified resin materials.
The method for preparing a magnetic composite material according to claim 8, wherein after the step of mixing the soft magnetic metal material and the binder in a preset ratio to form the magnetic composite material, the magnetic composite material has a The preparation method also includes:

The magnetic composite material is made into a feed, and the form of the feed includes any one or more of irregular powder, cake and viscous fluid.
An inductor is characterized in that it comprises a coil and a magnetic body covering the coil, and the magnetic body is made of the magnetic composite material according to any one of claims 1-7.
A method for preparing an inductor, comprising:

Winding wires to form coils;

placing the coil in a mold;

Filling the magnetic composite material according to any one of claims 1-7 into the mould;

applying a predetermined pressure into the mold to cause the magnetic composite to flow and form a magnetic body surrounding the coil, the predetermined pressure being less than the plastic deformation strength of the magnetic composite and the plastic deformation of the coil strength.
The method for manufacturing an inductor according to claim 13, wherein the shape of the magnetic body comprises a rectangular parallelepiped or an elliptical cylinder.
The method for manufacturing an inductor according to claim 13, wherein the two ends of the coil are respectively connected to electrode sheets, and the connection methods between the two ends of the coil and the electrode sheets include welding, solder paste sintering Either the method or the plating method.
The method for manufacturing an inductor according to claim 13, wherein the preset pressure is greater than or equal to 1.0 MPa and less than or equal to 15.0 MPa.