Inductor and electronic device

Abstract

The present application provides an inductor 30 and an electronic device 100. The inductor 30 comprises a first magnetic core 31, a coil 33, and a second magnetic core 32. The coil 33 is wound on the second magnetic core 32. The first magnetic core 31 encapsulates the coil 33 and the second magnetic core 32. The first magnetic core 31 comprises magnetic particles. The second magnetic core 32 comprises magnetic particles. In the first magnetic core 31, the volume fraction of the magnetic particles of the first magnetic core 31 is P1, and the average particle size of the magnetic particles of the first magnetic core 31 is D1; and in the second magnetic core 32, the volume fraction of the magnetic particles of the second magnetic core 32 is P2, and the average particle size of the magnetic particles of the second magnetic core 32 is D2, wherein 1<P1 / P2≤1.15, and 4 μm≤D1+D2≤40 μm.

Description

Inductors and electronic devices

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 11, 2023, with application number 202311169100.2 and application name “Inductor and Electronic Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field related to power inductor devices, and in particular to inductors and electronic equipment. Background Art

[0003] With the development of internet technology and intelligent products, power inductors are an essential component of the power circuits of small, thin devices such as smartphones. As smart products become increasingly miniaturized, such as thinner foldable smartphones, high levels of integrated functionality and flexible circuit board layouts are required, making the miniaturization and thinning of power inductors an inevitable trend.

[0004] Common small power inductors have a structure where a conductive coil is embedded in a core formed of insulating magnetic material, with both ends of the coil connected to electrodes on the component surface, such as in chip inductors. The main challenge in miniaturizing power inductors is how to maintain high magnetic permeability and good magnetic saturation performance while reducing the size of the inductor.

[0005] Summary of the Invention

[0006] The present application provides an inductor and an electronic device, wherein the inductor can ensure high magnetic permeability and good magnetic saturation performance of the inductor while being miniaturized.

[0007] The embodiment of the present application provides an inductor, which includes a first magnetic core, a coil, and a second magnetic core, wherein the coil is wound around the second magnetic core; the first magnetic core encapsulates the coil and the second magnetic core; the first magnetic core is a hollow magnetic body, which forms a cavity with an opening; the second magnetic core has a "T"-shaped cross-section, which includes a first magnet and a second magnet, wherein the first magnet is protruding from the surface of the second magnet. The second magnetic core is located in the cavity and seals the cavity.

[0008] The first magnetic core includes magnetic particles, and the second magnetic core includes magnetic particles. In the first magnetic core, the volume fraction of the magnetic particles of the first magnetic core is P1, and the average particle size of the magnetic particles of the first magnetic core is D1. In the second magnetic core, the volume fraction of the magnetic particles of the second magnetic core is P2, and the average particle size of the second magnetic particles is D2.

[0009] Among them, 1<P1 / P2≤1.15, 4μm≤D1+D2≤40μm.

[0010] In this embodiment, when the inductor is driven, the current flowing through the coil reacts with the second magnetic core to generate magnetic flux, and the magnetic flux circulates through the first magnetic core to the second magnetic core. In the first magnetic core and the second magnetic core, the volume fraction of the magnetic powder used satisfies the ratio range of 1<P1 / P2≤1.15; that is, the volume fraction of the first magnetic core is greater than the volume fraction of the second magnetic core. The first magnetic core has a higher magnetic permeability than the second magnetic core, which reduces the magnetic flux leaking out of the inductor, can ensure the power stored in the inductor, and effectively prevent magnetic flux leakage. Moreover, the sum of the average particle size D1 and D2 of the particles in the first magnetic core and the second magnetic core of the inductor provided in this application is in the range of 4μm≤D1+D2≤40μm. The larger the particle size, the larger the magnetic domain size inside the particle size, and the magnetic permeability increases with the increase of the magnetic domain size of the magnetic material; the increase in magnetic permeability in the first magnetic core and the second magnetic core is conducive to the miniaturization of the inductor.

[0011] In one embodiment, the magnetic particles of the first magnetic core include first magnetic particles and second magnetic particles, the particle size of the first magnetic particles is a first particle size, the particle size of the second magnetic particles is a second particle size, and the particle size of the first magnetic particles is larger than the particle size of the second magnetic particles, that is, the first particle size is larger than the second particle size; the magnetic particles of the second magnetic core include third magnetic particles and fourth magnetic particles, the third magnetic particles have a third particle size, the fourth magnetic particles have a fourth particle size, and the particle size of the third magnetic particles is larger than the particle size of the fourth magnetic particles, that is, the third particle size is larger than the fourth particle size. In this embodiment, the magnetic particles of the first magnetic core and the magnetic particles of the second magnetic core are particles of two different particle sizes. During the manufacturing process of the magnetic core, the gaps between the particles with large particle size are better filled by the particles with small particle size, which can increase the stacking density of the magnetic material when processing the magnetic core; under the same unit, the density of the magnetic powder is increased, which can increase the magnetic permeability, thereby further improving the magnetic permeability of the first magnetic core and the second magnetic core.

[0012] In a specific embodiment, the second and fourth magnetic particles are composite magnetic particles, each comprising an inner core and a shell coating the outer surface of the inner core. The inner core is an iron particle, and the shell is an inorganic insulating layer. The first and third magnetic particles are both iron-based amorphous alloys. Both the first and second magnetic cores utilize two types of magnetic particles, using both iron particles and an iron-based amorphous alloy to ensure that 1 < P1 / P2 ≤ 1.15, thereby ensuring the inductor's magnetic flux.

[0013] In one embodiment, the magnetic particles of the first magnetic core include composite magnetic particles or iron-based amorphous alloys, wherein the composite magnetic particles include an inner core and a shell coating the outer surface of the inner core, the inner core is an iron particle, and the shell is an inorganic insulating layer; the magnetic particles of the second magnetic core include composite magnetic particles or iron-based amorphous alloys, wherein the composite magnetic particles include an inner core and a shell coating the outer surface of the inner core, the inner core is an iron particle, and the shell is an inorganic insulating layer. It can be understood that iron-based amorphous alloys as magnetic materials can ensure high magnetic permeability and low core loss. Iron powder as a magnetic material has a high saturation magnetic induction intensity. In this embodiment, the first magnetic material and the second magnetic core can be made of iron-based amorphous alloys and composite magnetic particles containing iron powder, which can achieve miniaturization of the inductor while having high magnetic permeability and low core loss.

[0014] In one embodiment, the inorganic insulating layer is silicon oxide, and the iron-based amorphous alloy is carbonyl iron coated with an inorganic insulating layer.

[0015] In one embodiment, the first magnetic core further includes a first resin, the magnetic particles of the first magnetic core are dispersed in the first resin, and the content of the first resin is W1 based on the mass of the first magnetic core. The second magnetic core further includes a second resin, the magnetic particles of the second magnetic core are dispersed in the second resin, and the content of the second resin is W2 based on the mass of the second magnetic core, and W1≤W2.

[0016] During the inductor manufacturing process, the values ​​of W1 and W2 are adjusted to ensure that 1 < P1 / P2 ≤ 1.15 is met during the production of the first and second magnetic cores. Furthermore, the first resin content W1 is greater than 1%, and the second resin content W2 is greater than 1%. This ensures the strength and insulation properties of the first and second magnetic cores 31 and 32.

[0017] In one embodiment, the second resin content W2 is 3 wt.% to 4 wt.% based on the mass of the second magnetic core. The second resin content maintains the volume fraction of the magnetic particles in the second magnetic core and provides sufficient strength to the second magnetic core, ensuring that the second magnetic core does not break during the coil winding process.

[0018] In one embodiment, based on the mass of the first magnetic core, the first resin content W1 in the first magnetic core is 1 wt.% to 4 wt.%.

[0019] In one embodiment, the average particle size D1 of the magnetic particles of the first magnetic core is in the range of 2μm≤D1≤20μm, and the average particle size D2 of the magnetic particles of the second magnetic core is in the range of 2μm≤D2≤20μm. Increasing the particle size of the magnetic particles of the first magnetic core and the second magnetic core can improve the magnetic permeability, which is beneficial for reducing the size of the inductor and reducing the power loss caused by the winding resistance. Setting the particle size of the magnetic particles of the first magnetic core and the second magnetic core to a smaller size is beneficial for increasing the saturation current.

[0020] In one embodiment, the volume fraction P1 of the first magnetic material is in the range of 76.5% ≤ P1 ≤ 88%, thereby ensuring the magnetic permeability of the second magnetic core. The volume fraction of the magnetic particles of the second magnetic core is in the range of 76.5% ≤ P2 ≤ 88%, thereby preventing the insulating coating on the surface of the first magnetic material from being damaged by excessive processing during processing and preventing the particles within the first magnetic core from becoming unbound.

[0021] In one embodiment, the second magnetic core is formed by pressing a second composite magnetic material in a mold, wherein the second composite magnetic material is formed by mixing magnetic particles, an organic insulating material, and an organic solvent, drying the mixture, crushing and filtering the mixture, and then pressing the mixture in the mold; the first magnetic core is formed by a first composite magnetic material, and the first composite magnetic material is the same as the second composite magnetic material.

[0022] The coil is wound around the second magnetic core and placed in a mold, and the first magnetic core and the second magnetic core with the coil are pressed into shape in the mold;

[0023] The mixing time is 1 hour, the temperature inside the mold during pressing is 150° C., and the pressure is 500-600 MPa.

[0024] The length L of the inductor is 1.8mm≤L≤2.2mm, the width W of the inductor is 1.0mm≤L≤1.4mm, and the thickness T of the inductor is T≤0.8mm. The first magnet of the second magnetic core is a cylinder with an elliptical cross-section, the height of the first magnet is 0.3mm, the major diameter of the cross-section of the first magnet is 1.2mm, and the minor diameter is 0.5mm; the second magnet is a rectangular parallelepiped, the length of the second magnet is 1.9mm, the width of the second magnet is 1.0mm, and the thickness of the second magnet is 0.2mm. The inductor produced in this embodiment can achieve miniaturization while ensuring magnetic permeability.

[0025] An embodiment of the present application also provides an electronic device comprising a main body and the inductor, wherein the main body comprises a circuit board, and an electrode is provided on the exterior of the second magnetic core of the inductor, the electrode being electrically connected to the circuit board. Compared to the prior art, the inductor used in the electronic device of this embodiment can ensure magnetic permeability, that is, it can maintain an overall performance index while achieving a miniaturized design, thereby saving space occupied by the electronic device and facilitating the miniaturization of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0027] FIG1 is a schematic structural diagram of an electronic device provided in an embodiment of the present application;

[0028] FIG2 is a schematic diagram of the three-dimensional structure of an inductor provided in an embodiment of the present application;

[0029] FIG3 is a schematic diagram of the internal planar structure of an inductor provided in an embodiment of the present application;

[0030] FIG4 is an electron image of a cross section of a magnetic core made of a composite magnetic material used in the inductor shown in FIG2 ;

[0031] FIG5 is a graph showing the relationship between the magnetic permeability and the DC magnetic field of the inductor according to the embodiment of the present application and the inductor according to the comparative example;

[0032] FIG6 shows the (L×Idc / Rdc) of the embodiment of the present invention and the conventional embodiment. 2 / V performance comparison;

[0033] FIG. 7 shows the L / Rdc of the embodiment of the present invention and the conventional embodiment. 2 and L×Idc 2 / V performance comparison;

[0034] FIG8 shows the L / Rdc of the embodiment of the present invention and the conventional embodiment. 2 Performance comparison. DETAILED DESCRIPTION

[0035] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0036] Please refer to FIG. 1 and FIG. 2 . FIG. 1 is a schematic structural diagram of an electronic device 100 provided in an embodiment of the present application.

[0037] The electronic device 100 described in this application can be a mobile phone, a tablet computer, a navigation device, a smart watch, etc. This embodiment is described in detail using a foldable mobile phone as an example. For ease of description, the width direction of the electronic device 100 is defined as the X-axis direction, the length direction of the electronic device 100 is defined as the Y-axis direction, and the thickness direction of the electronic device 100 is defined as the Z-axis direction. The X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. It should be noted that the directional terms such as "top", "bottom", "up", "down", "left", and "right" involved in this application are described with reference to the orientation shown in Figure 1. The direction facing the positive direction of the Y axis is "top", the direction facing the negative direction of the Y axis is "bottom", the direction facing the positive direction of the Z axis is "up", the direction facing the negative direction of the Z axis is "down", the direction facing the positive direction of the X axis is "right", and the direction facing the negative direction of the X axis is "left". It does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting this application.

[0038] The electronic device 100 includes a main body 10 and a display screen 20 mounted on one side of the main body 10. The main body 10 includes a housing (not shown) of the electronic device 100, a circuit board 12, and electronic components and structural parts that implement various functions of the electronic device 100, such as electronic components such as a processor, an inductor 30, a speaker module, a camera, an antenna, and a power supply, and structural parts such as a middle frame and a support structure that support the electronic components. A power management chip 13 is also mounted on the circuit board 12. The inductor 30 is mounted on the circuit board 12 and is adjacent to the power management chip 13. The power management chip 13 and the inductor 30 are both electrically connected to the circuit board 12. The inductor 30 is an important component of electronic products such as mobile phones. The inductor 30 has the characteristic of preventing AC power from passing through while allowing DC power to pass smoothly. The main function of the inductor 30 is to isolate and filter AC signals or form a resonant circuit with capacitors, resistors, etc. The inductor 30 can maintain the stability of the current when the circuit board 12 is powered on, ensuring the safety of the circuit. For example, the inductor 30 can form a filter circuit together with a capacitor; for example, when the electronic device uses wireless, Bluetooth and other functions, the inductor 30 can also suppress the interference of electromagnetic waves on the electronic device.

[0039] Please refer to Figures 2 and 3 together. Figure 2 is a schematic diagram of the three-dimensional structure of the inductor provided in an embodiment of the present application, which shows the internal structure of the inductor; Figure 3 is a schematic diagram of the internal planar structure of the inductor provided in an embodiment of the present application.

[0040] The inductor 30 of this embodiment has a hexahedral structure, specifically a rectangular block. The inductor 30 includes a first magnetic core 31, a second magnetic core 32 and a coil 33. The first magnetic core 31 is a hollow magnetic body, which forms a cavity with an opening; the second magnetic core 32 has a "T"-shaped cross-section, which includes a first magnet 322 and a second magnet 321, and the first magnet 322 is protruding from the surface of the second magnet 321. The second magnetic core 32 is located in the cavity and seals the cavity. Specifically, the first magnet 322 is located in the cavity, the second magnet 321 seals the cavity opening, the first magnet 322 connects the second magnet 321 and the inner wall of the cavity, and the surface of the second magnet 321 facing away from the cavity (the first magnet 322) is part of the outer surface of the inductor 30. The coil 33 is wound around the first magnet 322 and extends to the outer surface of the second magnet 321 facing away from the first magnet 322, and is used to form the external electrode 34 (including the positive pole and the negative pole) of the inductor 30. It should be noted that the first magnetic core 31 covers the second magnetic core 32 and the coil 33. The first magnetic core 31 is formed in-mold after the second magnetic core 32 and the coil 33 are formed, and then covers the second magnetic core 32 and the coil 33. The cavity is the portion of the first magnetic core 31 that accommodates the second magnetic core 32 and the coil 33 after they are formed. When the inductor 30 is operating, a magnetic field is generated when the coil 33 is energized. When the current in the coil 33 changes, the magnetic field around the coil 33 also changes accordingly. In fact, the higher the magnetic permeability of the inductor 30, the greater the inductance of the inductor 30, and the smaller the resistance of the coil 33.

[0041] In the embodiment of the present application, the first magnetic core 31 and the second magnetic core 32 are both formed by pressing a composite magnetic material composed of magnetic powder (magnetic particles) and insulating material.

[0042] In one embodiment, the first magnetic core 31 and the second magnetic core 32 both have a type of magnetic particles; the first magnetic core 31 includes first magnetic particles, and the second magnetic core 32 includes third magnetic particles.

[0043] Figure 4 is an electron image of a cross-section of a magnetic core made of a composite magnetic material used in the inductor shown in Figure 2. In another embodiment, both the first magnetic core 31 and the second magnetic core 32 have two types of magnetic particles. When both the first magnetic core 31 and the second magnetic core 32 have two types of magnetic particles, the first magnetic core 31 includes first magnetic particles 311, second magnetic particles 312, and a first resin. The first magnetic particles 311 and the second magnetic particles 312 are dispersed in the first resin, and the first magnetic particles 311, the second magnetic particles 312, and the first resin are mixed and pressed to form the first magnetic core. The second magnetic core includes third magnetic particles (not shown), fourth magnetic particles (not shown), and a second resin. The third and fourth magnetic particles are dispersed in the second resin, and the third and fourth magnetic particles are mixed and pressed to form the second magnetic core. The first and second resins are thermosetting resins.

[0044] It should be noted that, for ease of description below, the first magnetic particles and / or the second magnetic particles can be understood as the magnetic particles forming the first magnetic core; that is, the magnetic particles contained in the first magnetic core 31 described below (the magnetic particles of the first magnetic core 31) can be the first magnetic particles or the second magnetic particles, or the first magnetic particles and the second magnetic particles. The third magnetic particles and / or the fourth magnetic particles can be understood as the magnetic particles forming the second magnetic core 32; that is, the magnetic particles contained in the second magnetic core 32 described below (the magnetic particles of the second magnetic core 32) can be the third magnetic particles or the fourth magnetic particles, or the third magnetic particles and the fourth magnetic particles.

[0045] The volume fraction of the magnetic particles in the first magnetic core 31 is P1, the average particle size of the magnetic particles in the first magnetic core 31 is D1, the volume fraction of the magnetic particles in the second magnetic core is P2, and the average particle size of the magnetic particles in the second magnetic core 32 is D2. The ratio between the volume fraction P1 of the magnetic particles in the first magnetic core 31 and the volume fraction P2 of the magnetic particles in the second magnetic core 32 is in the range of 1<P1 / P2≤1.15. The sum of D1 and D2 is in the range of 4μm≤D1+D2≤40μm. It should be noted that the volume fraction of the magnetic particles refers to the percentage of the total volume of the magnetic core, measured by the volume of the magnetic core. For example, the volume fraction of the magnetic particles in the first magnetic core 31 is measured by the volume of the first magnetic core 31, that is, the percentage of the magnetic particles in the first magnetic core 31 to the volume of the first magnetic core 31. The average particle size D1 of the magnetic particles in the first magnetic core 31 and the average particle size D2 of the magnetic particles in the second magnetic core 32 both refer to the outer diameter of the magnetic particles. It should be noted that particle size refers to the outer diameter of the magnetic particles, and the average particle size is the average of the sum of the outer diameters of the magnetic particles in the magnetic core. The magnetic particles are spherical, elliptical, or nearly spherical. It can also be understood that the average particle size of a single magnetic particle can be obtained. The average particle size D1 of the first magnetic core and the average particle size D2 of the magnetic particles in the second magnetic core 32 can be the average of the sum of the particle sizes of multiple magnetic particles in the magnetic core. For non-spherical single magnetic particles, the average particle size is obtained and then the sum of multiple magnetic particles is calculated to obtain the average particle size of the magnetic core.

[0046] In one embodiment, the volume fraction P1 of the magnetic particles of the first magnetic core 31 is in the range of 76.5% ≤ P1 ≤ 88%, thereby ensuring the magnetic permeability of the first magnetic core 31. The volume fraction P2 of the magnetic particles of the second magnetic core 32 is in the range of 76.5% ≤ P2 ≤ 88%. This prevents the insulating coating on the surface of the second magnetic core 32 from being damaged by excessive processing during processing, and also prevents the particles within the second magnetic core 32 from being unbound.

[0047] It can be understood that the greater the volume fraction P1 of the magnetic particles in the first magnetic core 31 and the volume fraction P2 of the magnetic particles in the second magnetic core 32, the higher the magnetic permeability of the first magnetic core 31 and the second magnetic core 32. When the inductor 30 is driven, the current flowing through the coil 33 interacts with the second magnetic core 32 to generate magnetic flux, which circulates through the first magnetic core 31 to the second magnetic core 32. The volume fractions of the magnetic powder particles used in the first magnetic core 31 and the second magnetic core 32 satisfy the ratio range of 1<P1 / P2≤1.15; that is, the volume fraction of the first magnetic core 31 is greater than the volume fraction of the second magnetic core 32. The first magnetic core 31 has a higher magnetic permeability than the second magnetic core 32, reducing the magnetic flux leaking out of the inductor 30, ensuring the power stored in the inductor 30, and effectively preventing magnetic flux leakage, which is more conducive to the miniaturization of the inductor 30 and avoids affecting the operation of other nearby electronic components.

[0048] The sum of the average particle size D1 of the magnetic particles in the first magnetic core 31 and the average particle size D2 of the magnetic particles in the second magnetic core 32 of the inductor 30 provided herein is within the range of 4 μm ≤ D1 + D2 ≤ 40 μm. Larger magnetic particle sizes increase the size of the magnetic domains within the particles, and the magnetic permeability increases with the size of the magnetic domains in the magnetic material. The increased magnetic permeability in the first and second magnetic cores 31 and 32 facilitates the miniaturization of the inductor 30.

[0049] In one embodiment of the present application, the magnetic particles of the first magnetic core 31 include composite magnetic particles and / or (Fe-Si-B) iron-based amorphous alloys, wherein the composite magnetic particles include an inner core and a shell coating the outer surface of the inner core, wherein the inner core is an iron particle, and the shell is an inorganic insulating layer. The magnetic particles of the second magnetic core 32 include composite magnetic particles and / or iron-based amorphous alloys, wherein the composite magnetic particles include an inner core and a shell coating the outer surface of the inner core, wherein the inner core is an iron particle, and the shell is an inorganic insulating layer.

[0050] Exemplarily, when both the first magnetic core 31 and the second magnetic core 32 have a single type of magnetic particle, the first magnetic particles of the first magnetic core 31 and the third magnetic particles of the second magnetic core 32 are composite magnetic particles. This ensures high saturation magnetic induction in the first magnetic core 31 and the second magnetic core 32. Exemplarily, the first magnetic particles of the first magnetic core 31 and the second magnetic particles of the second magnetic core 32 are both iron-based amorphous alloys, which ensures high magnetic permeability and low core loss.

[0051] In this embodiment, the first magnetic core 31 and the second magnetic core 32 each include two magnetic core particles. The average particle size of the first magnetic particles 311 and the second magnetic particles 312 in the first magnetic core 31 is D1, where 2 μm ≤ D1 ≤ 20 μm. The average particle size of the third magnetic particles and the fourth magnetic particles in the second magnetic core 32 is D2, where 2 μm ≤ D2 ≤ 20 μm.

[0052] In this embodiment, the magnetic particles in the first magnetic core 31 have a first particle size and a second particle size, and the first particle size and the second particle size have different values. Specifically, the particle size of the first magnetic particles 311 is the first particle size, the particle size of the second magnetic particles 312 is the second particle size, and the first particle size is larger than the second particle size. The magnetic particles in the second magnetic core 32 have a third particle size and a fourth particle size. Specifically, the third magnetic particles have a third particle size, the fourth magnetic particles have a fourth particle size, and the third particle size is larger than the fourth particle size. Both the first magnetic core 31 and the second magnetic core 32 use magnetic particles of two different particle sizes. During the manufacturing process of the first magnetic core 31 and the second magnetic core 32, the gaps between the large-size magnetic particles are better filled with the small-size magnetic particles, which can increase the stacking density of the magnetic material when processing the magnetic core; under the same unit, the increased density of the magnetic powder particles can increase the magnetic permeability, thereby further improving the magnetic permeability of the first magnetic core 31 and the second magnetic core 32.

[0053] In this embodiment, the second magnetic particles 312 of the first magnetic core 31 are composite magnetic particles comprising an inner core and a shell coating the outer surface of the inner core. The inner core is an iron particle, the shell is an inorganic insulating layer, and the first magnetic particles 311 are an iron-based amorphous alloy. In one embodiment, specifically, the inorganic insulating layer is made of silicon oxide, and the second magnetic particles are formed of carbonyl iron coated with the inorganic insulating layer.

[0054] The fourth magnetic particle is a composite magnetic particle, comprising a core and a shell coated on the outer surface of the core, wherein the core is an iron particle, the shell is an inorganic insulating layer, and the third magnetic particle is an iron-based amorphous alloy. In one embodiment, specifically, the material of the inorganic insulating layer is silicon oxide, and the fourth magnetic particle is formed by hydroxy iron coated with an inorganic insulating layer. The carbonyl iron coated with the inorganic insulating layer has high saturation magnetism and high magnetization intensity; the iron-based amorphous alloy has low loss and high magnetic permeability characteristics. The iron-based amorphous alloy is also coated with an inorganic insulating layer.

[0055] The first magnetic core 31 and the second magnetic core 32 of the present application meet the above conditions, which can avoid the deterioration of the inductance saturation characteristics due to the physical properties of the magnetic material, and the increase in the current impedance generated by the coil, which will lead to an increase in the power loss of the inductor 30; under the premise of ensuring the magnetic permeability, when the volume of the second magnetic core 32 is reduced, such as the height or cross-sectional area is reduced, the number of turns of the electric coil will also be reduced accordingly; that is, when the magnetic permeability and saturation characteristics of the inductor 30 are met, the volume of the entire inductor 30 can be reduced, the inductor can be miniaturized, and the power loss of the inductor 30 can be avoided.

[0056] It can be understood that the first magnetic core 31 and the second magnetic core 32 are made of the same composite magnetic material, but the particle size and volume fraction of the magnetic powder in the composite magnetic material are different.

[0057] In one embodiment, the first resin content is W1 based on the mass of the first magnetic core 31, and the second resin content is W2 based on the mass of the second magnetic core 32, where W1<W2. The first resin content W1>1% and the second resin content W2>1% ensure the strength and insulation of the first and second magnetic cores 31, 32.

[0058] In one embodiment, the first resin content W1 in the first magnetic core 31 is 1 wt.% to 4 wt.% based on the mass of the first magnetic core 31. The second resin content W2 is 3 wt.% to 4 wt.% based on the mass of the second magnetic core. This maintains the volume fraction of the magnetic particles in the second magnetic core 32 and provides sufficient strength to prevent the second magnetic core 32 from breaking during the winding of the coil 33.

[0059] The performance of the inductor 30 formed by combining the specific embodiments of the first magnetic core 31 and the second magnetic core 32 made of the above-mentioned composite magnetic material will be further described below; the inductor sample prepared using the composite magnetic material of this embodiment is prepared by the same method as the method of preparing the inductor 30 in the prior art, and the coil of the inductor sample (hereinafter referred to as the sample embodiment) has the same cross-sectional area, length and number of turns as the coil of the comparative example (comparative example), and the first magnetic core 31 and the second magnetic core 32 of the sample embodiment have the same dimensions as the first magnetic core 31 and the second magnetic core 32 of the comparative example.

[0060] Please refer to Tables 1 and 2. Table 1 shows the process conditions and SEM image analysis of an inductor 30 fabricated using the composite magnetic material of this embodiment in comparison with an inductor of the prior art. Table 2 shows the performance evaluation of an inductor fabricated using the composite magnetic material of this embodiment in comparison with an inductor of the prior art.

[0061] Specifically, Table 1 shows a plurality of sample embodiments and comparative examples, specifically showing the mixing ratio of the first magnetic particles and the second magnetic particles, the resin solid content, and the pressure conditions during the molding process of the first magnetic core. The mixing ratio of the third magnetic particles and the fourth magnetic particles in the composite magnetic material used for the second magnetic core, the blending amount of the resin solid content, and the pressure conditions during the molding process of the second magnetic core. Table 1 also shows the volume fraction and average particle size of the particles (first magnetic particles and second magnetic particles) in the first magnetic core of each inductor calculated by SEM image analysis, as well as the volume fraction and average particle size of the particles in the second magnetic core (third magnetic particles and fourth magnetic particles). Among them, Examples 1-15 and Comparative Examples C1-C7 and Comparative Examples E1-E3 all provide an inductor, which is specifically prepared according to the following steps. In Examples 1-15 and Comparative Examples C1-C7 and Comparative Examples E1-E3, Examples 1-15 refer to the samples of this embodiment, and Comparative Examples C1-C7 and Comparative Examples E1-E3 refer to sample comparisons of different volume fractions.

[0062] The specific steps for preparing the inductor are as follows:

[0063] Step S1 : selecting magnetic particles for making a first magnetic core and a second magnetic core.

[0064] For example, the first magnetic particles of the first magnetic core are made of carbonyl iron coated with silicon oxide, the second magnetic particles are made of an iron-based amorphous alloy, the third magnetic particles of the second magnetic core are made of hydroxyl iron coated with silicon oxide, and the fourth magnetic particles are made of an iron-based amorphous alloy.

[0065] In step S2, the magnetic particles of the first magnetic core 31, the organic insulating material, and the organic solvent are mixed and dried to form a dry first composite powder. The mixing time is 1 hour. The solid content of the organic insulating material relative to the first magnetic core 31 is 1 wt.% to 4 wt.%. The organic insulating material is epoxy resin. The organic solvent content is 5% to 12%.

[0066] The magnetic particles of the second magnetic core 32, the organic insulating material, and the organic solvent are mixed and dried to form a dry second composite powder. The mixing time is 1 hour. The solid content of the organic insulating material relative to the magnetic particles of the second magnetic core 32 is 3 wt.%-4 wt.%. The organic insulating material is epoxy resin. The organic solvent content is 5%-12%. The solid content of the organic insulating material relative to the magnetic particles of the second magnetic core 32 is 3 wt.%-4 wt.% to maintain the volume fraction of the metal powder and provide sufficient strength to the second magnetic core 32, ensuring that the second magnetic core 32 does not break during the winding process.

[0067] Specifically, the first resin content W1 contained in the first magnetic core 31 is less than the second resin content W2 contained in the second magnetic core 32; and 1% < W1 < W2 to ensure the strength and insulation of the first magnetic core 31. Of course, the material of the first magnetic core can be prepared in advance for standby.

[0068] Step S3: Crush the first composite powder and the second composite powder respectively and filter them through a sieve to obtain the composite magnetic material for preparing the first magnetic core and the composite magnetic material for preparing the second magnetic core. Among them, the sieve has a sieve hole size of 90 μm.

[0069] Step S4:压制制成第二磁芯32,其中,成型时模具温度150℃,压强500-600MPa。可以理解的是,调整压强和有机绝缘材料的含量,可以调整制备构成第一磁芯的磁性材料的体积分数,以及构成第二磁芯的磁性材料的体积分数。 Use the composite magnetic material for preparing the second magnetic core to press and form the second magnetic core 32. Among them, the mold temperature is 150 °C and the pressure is 500 - 600 MPa during molding. It can be understood that by adjusting the pressure and the content of the organic insulating material, the volume fraction of the magnetic material constituting the first magnetic core and the volume fraction of the magnetic material constituting the second magnetic core can be adjusted.

[0070] Step S5: Wrap the wire around the second magnetic core 32 to form the coil 33. The ends of the coil are pulled out and glued to the bottom of the second magnetic core 32 to form the external electrode 34.

[0071] Step S6: Place the preliminary magnetic core formed by the second magnetic core 32 and the coil 33 in the mold, cover it with the composite magnetic material formed by the first magnetic core 31 and press it to form the first magnetic core 31 integrated with the second magnetic core 32, that is, form the inductor 30.

[0072] Table 1

[0073] 需要说明的是,原文中“步骤S6”的翻译部分存在一个表述错误,已修正为“压制制成第二磁芯32,其中,成型时模具温度150℃,压强500-600MPa。可以理解的是,调整压强和有机绝缘材料的含量,可以调整制备构成第一磁芯的磁性材料的体积分数,以及构成第二磁芯的磁性材料的体积分数。”完整准确的翻译应该是:“Use the composite magnetic material for preparing the second magnetic core to press and form the second magnetic core 32. Among them, the mold temperature is 150 °C and the pressure is 500 - 600 MPa during molding. It can be understood that by adjusting the pressure and the content of the organic insulating material, the volume fraction of the magnetic material constituting the first magnetic core and the volume fraction of the magnetic material constituting the second magnetic core can be adjusted.” 请根据实际需求进行调整。It can be seen from the column of the mixing mass ratio of the first magnetic particles / the second magnetic particles in Table 1 that the first magnetic core 31 and the second magnetic core 32 of the sample embodiment can both use one type of magnetic particles. For example, in serial number 1, only the first magnetic particles exist in the first magnetic core 31, and only the third magnetic particles exist in the second magnetic core 32. The resin content in the first magnetic core 31 is less than the resin content in the second magnetic core 32; the pressure is 500-600Mpa. In serial number 1, in the first magnetic core 31 and the second magnetic core 32, D1+D2 is 40μm, and P1 / P2 is greater than 1. In comparative example C5, the first magnetic core 31 and the second magnetic core 32 can both use one type of magnetic particles, the resin content in the first magnetic core 31 is equal to the resin content in the second magnetic core 32, and D1+D2 is 40μm; and in comparative example C5, P1 / P2 in the first magnetic core 31 and the second magnetic core 32 is equal to 1. It can be confirmed that P1 / P2 of the inductor of this embodiment is greater than 1 and less than or equal to 1.15, P1 / P2 in comparative example C is equal to 1, and P1 / P2 in comparative example E is less than 1; it can be seen that by adjusting the resin content in the first magnetic core 31 of the sample embodiment to be less than the resin content in the second magnetic core 32, the value of P1 / P2 can be adjusted.

[0074] As shown in Table 1, in sample embodiment No. 4, both the first magnetic core 31 and the second magnetic core 32 use two types of magnetic particles, and the resin content in the first magnetic core 31 is less than the resin content in the second magnetic core 32. The value of P1 / P2 in the first magnetic core 31 and the second magnetic core 32 is greater than 1. In comparative embodiment C2, the pressure of the first magnetic core 31 is greater than the pressure of the first magnetic core 31 of No. 4, the resin content in the first magnetic core 31 is equal to the resin content of the second magnetic core 32, and other conditions are the same; the result is that the value of P1 / P2 in the sample embodiment is greater than 1, while the value of P1 / P2 in the comparative example is equal to 1. In E3, the resin content in the first magnetic core 31 is greater than the resin content in the second magnetic core 32. Compared with No. 8 or 11, the result is that the value of P1 / P2 in the sample embodiment is greater than 1, while the value of P1 / P2 in the comparative example is less than 1. It can be seen that the pressure during the manufacturing process can also affect the value of P1 / P2.

[0075] Based on the above several embodiments and comparative examples, it can be confirmed that the relationship between the resin content in the first magnetic core 31 and the resin content in the second magnetic core 32, and the pressure conditions during the manufacturing process will affect the value of P1 / P2. Under the determination of the magnetic particles in the first magnetic core 31 and the second magnetic core 32, adjusting the pressure and resin content can adjust P1 / P2, and P1 / P2 directly affects the magnetic permeability of the inductor 30.

[0076] The performance of the above-mentioned inductor is verified below with reference to Table 2, which shows P1 / P2, D1+D2 and corresponding basic inductance characteristics and performance index values ​​of the embodiment and the comparative example.

[0077] It should be noted that the inductor 30 has characteristics of inductance value L, rated current Idc and DC resistance Rdc; the higher the inductance value L or rated current Idc, the greater the power. DC resistance Rdc is the resistance value generated when the coil is energized. If the resistance value is large, the power loss of the inductor 30 during operation increases. The size of the inductor 30 is composed of the external dimensions of length l, width w and height t and the volume V obtained by multiplying these dimensions. One performance of the inductor 30 is power density, which can be expressed as L×Idc 2 / V, and power density represents the maximum magnetic energy per unit volume that can be stored in the inductor 30. It can be understood that if this index is high, it means that the magnetic permeability of the inductor 30 is high. Another performance index of the inductor 30 is the power efficiency index, which can be expressed as L / Rdc 2 When the second core 32 of the inductor 30 is wound with a coil having the same cross-sectional area, the inductance L is proportional to the square of the number of turns of the coil, and Rdc is proportional to the length of the coil. It can be understood that it is proportional to the number of turns, L / Rdc 2 It can be defined as a constant value. The magnetic core made of the composite magnetic material has a high magnetic permeability, so the inductance value L will also increase and remain constant. Then the number of turns of the coil can be reduced, thereby reducing the DC resistance Rdc. It can be understood that a larger power efficiency index L / Rdc 2 Indicates performance with high inductance and low power loss. The product of these two indicators (L×Idc / Rdc) 2 / V is an overall performance index of the inductor 30, which can be understood as a comprehensive comparison including inductance value, saturation current, DC resistance and volume.

[0078] Table 2

[0079] As shown in Table 2, the P1 / P2 ratio of the sample inductor 30 is greater than 1. The overall performance index (L×Idc / Rdc) of the inductor 30 of the sample embodiment is 2 / V ratio of the overall performance index of all comparative examples (L×Idc / Rdc) 2 / V is large, and it is obvious that the overall performance (magnetic permeability and saturation) of the inductor of the sample embodiment is optimized over that of the comparative example.

[0080] From Table 2, we can confirm that the performance index L×Idc 2 / V and L / Rdc 2 The embodiment of the present invention has better electromagnetic performance than the comparative example, and changes with the size of D1+D2, L / Rdc 2The higher the value of , the better the overall performance index of inductor 30 can be achieved by adjusting the particle size and volume fraction of the first and second magnetic cores 31 and 32 of inductor 30. In other words, increasing the particle size of the magnetic particles in first and second magnetic cores 31 and 32 can increase the magnetic permeability, which helps reduce the inductor size and power loss caused by winding resistance. Setting a smaller particle size for the magnetic particles in first and second magnetic cores 31 and 32 is beneficial for increasing the saturation current. While ensuring that the inductor size is reduced, the optimal particle size and volume fraction should be determined by comprehensively considering the effects of the overall magnetic particle permeability and power consumption.

[0081] Please refer to Figure 5, which is a graph showing the relationship between the magnetic permeability and the DC magnetic field of the inductor of the embodiment of the present application and the inductor of the comparative example. Specifically, it is a graph showing the relationship between the magnetic permeability and the DC magnetic field of the magnetic material (magnetic particles) used in the inductors of Examples No. 4, No. 5, No. C-2 and No. E1 in Table 1. The four magnetic materials are processed into ring samples, wound and the magnetic permeability is measured at 1 MHz while applying a DC bias current to obtain a characteristic curve. The DC bias characteristics of the inductor L value can be obtained by the relationship between the DC magnetic field H and the magnetic permeability μ shown in Figure 6. r The inductance L is proportional to the magnetic permeability, and the DC bias current is proportional to the DC bias magnetic field. For example, the four materials are the first magnetic material, the second magnetic material, the third magnetic material, and the fourth magnetic material.

[0082] The characteristic curve of the first magnetic material in Figure 5 represents the magnetic material used in first magnetic core 31 of Comparative Example C2 in Tables 1 and 2. The magnetic permeability of this material decreases by 30% when subjected to a DC magnetic field of 13.3 kA / m. Idc for Comparative Example C2 represents the current required to reduce the magnetic permeability by 30% when an average magnetic field of 13.3 kA / m is applied to the inductor core.

[0083] The characteristic curve of the second magnetic material in FIG5 is a curve obtained by increasing the volume fraction of the magnetic powder particles of the first magnetic material; as in Sample Example No. 4, the second magnetic material is used for the first magnetic core 31, and the first magnetic material is used for the second magnetic core 32, and the overall performance index is higher than that of Comparative Example C2 by increasing the inductance L value without significantly reducing Idc.

[0084] The characteristic curve of the third magnetic material in Figure 5 is a curve having a larger volume fraction than the volume fraction of the magnetic powder particles of the first magnetic material, but a smaller average particle size of the magnetic powder particles. Due to the small grain size of the powder, when the DC bias magnetic field is 0, the magnetic permeability is lower than that of the first magnetic material, but when the bias magnetic field increases, the magnetic permeability becomes higher than the magnetic permeability of the first magnetic material. According to this characteristic curve, it is assumed that sample embodiment No. 5 (in which the third magnetic material is used for the first magnetic core and the first magnetic core material is used for the second magnetic core) exhibits a higher Idc and overall performance index than comparison example C2. By using the above-mentioned second magnetic material and the third magnetic material for the first magnetic core 31, it is believed that high magnetic permeability is achieved within a larger operating current range, and the magnetic flux leaked from the inductor 30 is reduced, effectively inducing the magnetic flux in the second magnetic core 32, thereby improving the electromagnetic performance.

[0085] The characteristic curve of the fourth magnetic material in FIG5 is a curve for a magnetic powder material having a lower volume fraction and a larger average particle size than the first magnetic material. Due to the large particle size of the magnetic powder particles, this curve has a higher magnetic permeability when the DC bias magnetic field is 0. However, as the applied DC bias magnetic field increases, the magnetic permeability drops sharply, becoming lower than that of the first magnetic material. Reflecting this characteristic curve, comparative example E1 (using the fourth magnetic material for the first magnetic core 31 and the first magnetic material for the second magnetic core 32) exhibits lower Idc and overall performance index than comparative example C2 and the sample embodiment.

[0086] Based on the above examples and comparative results, it can be understood that the volume fraction of magnetic particles in the second magnetic core 32 should be at least 76.5%. If the volume fraction is less than 76.5%, the magnetic permeability of the core becomes too low, requiring a larger number of turns or coils to achieve a constant L value, which in turn leads to a significant increase in Rdc. When calculating the volume fraction of magnetic particles in the second magnetic core 32 from SEM images, a 1% variation can be allowed. Therefore, when it can be said that P1 is greater than P2, the minimum value of P1 / P2 is 1.01. The volume fraction of magnetic particles in the first magnetic core 31 is 88% or less. When the volume fraction of magnetic particles in the first magnetic core 31 exceeds 88%, the insulating coating on the surface of the magnetic particles in the first magnetic core 31 is damaged by excessive processing during the stamping process, and many metal powders are bonded together within the core. Moreover, during the driving process, eddy currents flowing between the magnetic metal powder increase, resulting in a significant decrease in the L value at the driving frequency. In addition, the damage to the insulating coating impairs the insulation performance of the magnetic core. Given the upper limit of 88% for P1 and the lower limit of 77% for P2, the upper limit of P1 / P2 is 1.15. When manufacturing the inductor, the volume fraction of the magnetic particles in the first magnetic core 31 is ensured to be higher than the volume fraction of the magnetic particles in the second magnetic core 32 to achieve a good overall performance index for the inductor.

[0087] The lower limit of D1+D2 is 4μm because the lower limit of the particle size of the magnetic particles used in the first magnetic core 31 and the second magnetic core 32 is 2μm. If magnetic particles with a particle size less than 2μm are used, the specific surface area of ​​the corresponding magnetic particles increases, and the amount of resin required to cover the surface of the magnetic particles increases significantly, resulting in an inability to achieve a volume fraction of 77% or higher of the magnetic powder. The upper limit of D1+D2 is 40μm because the upper limit of the particle size of the magnetic particles used in the first magnetic core 31 and the second magnetic core 32 is 20μm. If magnetic particles larger than 20μm are used, the eddy current generated in the corresponding magnetic powder increases when the inductor 30 is driven, and the magnetic permeability of the magnetic core at the driving frequency is greatly reduced, resulting in a lower L value.

[0088] Please refer to Table 3 and Figure 5. Table 3 shows the size and performance measurement results of inductor 30 of the prior art (conventional technology) and this embodiment. To verify the effect of reducing the size of inductor 30 by applying the present invention, each surface of the inductors of Examples 4 and 11 was polished to reduce the chip size (inductor size adjustment), and the characteristics were evaluated in comparison with conventional Example C1. Performance indicators (L×Idc / Rdc) of Examples 4 and 11 are: 2 / V are 15.0% and 25.6% higher than C1, respectively. If these performance advantages are used to reduce the size of the inductor 30, the volume of the inductor 30 can be reduced by 15% or 25.6% while maintaining the same performance as the conventional inductor 30. L, W, and T in Table 3 refer to the height, width, and thickness of the inductor, respectively, and can be found in Figure 2. 4' and 11' in the table are the characteristics of the samples of Examples 4 and 11 whose surfaces have been polished. The volume of 4' is 15% smaller than that of Example 4, and the volume of 11' is 25.6% smaller than that of Example 11. However, the performance indexes of 4' and 11' are almost the same as those of C1 of the same volume before polishing.

[0089] It can be understood that the inductor shown in Figure 2 is a sample inductor made using the aforementioned method and materials. The length L of the inductor of the present application is less than or equal to 2.2 mm and greater than or equal to 1.8 mm. The width W is less than or equal to 1.4 mm and greater than or equal to 1.0 mm. The thickness T is a maximum of 0.8 mm. Through this verification, it is confirmed that the magnetic composite material of the above embodiment of the present invention is effective in reducing the size of the inductor 30. Among them, the first magnet 322 of the second magnetic core 32 is a cylinder with an elliptical cross-section, the height of the first magnet 322 is 0.3 mm, the major diameter of the cross-section of the first magnet 322 is 1.2 mm, and the minor diameter is 0.5 mm; the second magnet 321 is a rectangular parallelepiped, the length of the second magnet 321 is 1.9 mm, the width of the second magnet 321 is 1.0 mm, and the thickness of the second magnet is 0.2 mm.

[0090] Table 3

[0091] It should be noted that the embodiments of the present invention are characterized by samples of the chip inductor 30 structure, but the benefits of the present invention are not limited to the disclosed inductor 30 structure.

[0092] The inductor 30 sample of the above-mentioned embodiment can be tested to obtain the volume fraction P1 of the magnetic particles of the first magnetic core 31 of the actual sample inductor 30, the average particle size D1 of the magnetic particles of the first magnetic core 31, the volume fraction P2 of the magnetic particles of the second magnetic core, and the average particle size D2 of the magnetic particles of the second magnetic core 32.

[0093] And test performance parameters such as μ-H curve, inductance value L, DC resistance Rdc and rated current Idc.

[0094] The D1, D2, P1, and P2 values ​​of the inductor sample were tested. First, the prepared inductor sample was made into a metallographic specimen (the inductor was embedded in a mold and polished until the cross-section of the second magnetic core 32 was visible). The surface of the inductor sample was then polished using an ion polisher. This smoothed the cross-section and removed any surface impurities, allowing for clearer magnetic particle testing. The external dimensions of the inductor sample were measured using a spiral micrometer.

[0095] Next, a scanning electron microscope (SEM) was used in backscattering mode to magnify the inductor metallographic sample (cross section) 500x and capture three scattered electron signal (BSD) images. Finally, WinRoof image analysis software was used to analyze each BSD image to obtain the parameters D1, D2, P1, and P2. The average value of each parameter across the three images was then taken. Finally, the D1, D2, P1, and P2 values ​​for the inductor sample were obtained.

[0096] Testing the performance parameters of inductor samples. μ-H curves are measured using a vibrating sample magnetometer. For example, a magnetic particle sample of the inductor is placed in a magnetic field and vibrated. A probe is used to measure the μ-H curve as the magnetic field changes. Equipment model: TOEI VSM (Type 5-15).

[0097] To test the inductance value (L) of the inductor sample, an impedance analyzer was used at 1MHz and 0.5V. The device used was the Agilent 4991A impedance analyzer. A microohmmeter can be used to test the Rdc of the inductor sample; of course, any test equipment with equivalent performance will do. To test the Idc of the inductor sample, a Microtest 6575 impedance analyzer and a programmable current source (used to control the inductor's DC current) were used. Specifically, the inductor sample was placed in the impedance analyzer's test fixture, the DC-bias function was enabled, and the DC current applied to the inductor was gradually increased until the L value was confirmed at 1MHz and 0.5V. Then, the current L was reduced by 30% to obtain the Idc value.

[0098] Please refer to FIG. 6 to FIG. 8 , wherein FIG. 6 shows (L×Idc / Rdc) of the embodiment of the present invention and the conventional embodiment. 2 The materials used in the first and second magnetic cores of the inductor and their corresponding performance indicators are compared. In particular, P1 / P2 is 1.01 to 1.15, and D1+D2 is 4 to 40 μm. This means that the embodiments of the present invention achieve better performance indicators than the conventional embodiments and the embodiments.

[0099] FIG. 7 shows the L / Rdc of the embodiment of the present invention and the conventional embodiment. 2 and L / Idc 2 Figure 8 shows the performance comparison of the L / Rdc of the embodiment of the present invention and the traditional embodiment. 2 The embodiment of the present invention is proved to have lower power consumption and better overall performance index than the conventional embodiment. In more detail, the performance characteristics vary with the size of D1+D2. As shown in Figure 7, the larger the D1+D2, the higher the L / Rdc 2 The higher the value of ; this characteristic shows that the overall performance of the inductor can be improved by appropriately setting the powder particle size according to the performance parameters to be concerned in the inductor design.

[0100] The above are only some of the embodiments and implementations of this application. The scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. An inductor, characterized in that: The inductor comprises a first magnetic core, a coil and a second magnetic core, wherein the coil is wound around the second magnetic core; the first magnetic core encapsulates the coil and the second magnetic core; The first magnetic core and the second magnetic core both include magnetic particles, the volume fraction of the magnetic particles of the first magnetic core is P1, the average particle size of the magnetic particles of the first magnetic core is D1, the volume fraction of the magnetic particles of the second magnetic core is P2, and the average particle size of the magnetic particles of the second magnetic core is D2; Among them, 1<P1 / P2≤1.15, 4μm≤D1+D2≤40μm.

2. The inductor according to claim 1, characterized in that The magnetic particles of the first magnetic core include first magnetic particles and second magnetic particles, and the particle size of the first magnetic particles is larger than the particle size of the second magnetic particles; The magnetic particles of the second magnetic core include third magnetic particles and fourth magnetic particles, and the particle size of the third magnetic particles is larger than that of the fourth magnetic particles.

3. The inductor according to claim 2, characterized in that The second magnetic particle is a composite magnetic particle, comprising a core and a shell layer covering the outer surface of the core, the core is an iron particle, the shell layer is an inorganic insulating layer, and the first magnetic particle is an iron-based amorphous alloy; The fourth magnetic particle is a composite magnetic particle, comprising a core and a shell coating the outer surface of the core, the core is an iron particle, the shell is an inorganic insulating layer, and the third magnetic particle is an iron-based amorphous alloy.

4. The inductor according to claim 1, wherein: The magnetic particles of the first magnetic core include composite magnetic particles or iron-based amorphous alloys, wherein the composite magnetic particles include a core and a shell layer coated on the outer surface of the core, the core is an iron particle, and the shell layer is an inorganic insulating layer; The magnetic particles of the second magnetic core include composite magnetic particles or iron-based amorphous alloys, wherein the composite magnetic particles include an inner core and a shell layer covering the outer surface of the inner core, the inner core is an iron particle, and the shell layer is an inorganic insulating layer.

5. The inductor according to any one of claims 1 to 4, characterized in that: The first magnetic core also includes a first resin, in which the magnetic particles of the first magnetic core are dispersed, and the content of the first resin is W1 based on the mass of the first magnetic core. The second magnetic core also includes a second resin, in which the magnetic particles of the second magnetic core are dispersed, and the content of the second resin is W2 based on the mass of the second magnetic core, and W1≤W2.

6. The inductor according to claim 5, characterized in that The content of the first resin W1>1%, and the content of the second resin W2>1%.

7. The inductor according to claim 5, characterized in that Based on the mass of the second magnetic core, the content W2 of the second resin is 3wt.%-4wt.%.

8. The inductor according to claim 5, characterized in that Based on the mass of the first magnetic core, the first resin content W1 in the first magnetic core is 1 wt.% to 4 wt.%.

9. The inductor according to claim 3 or 4, characterized in that: The inorganic insulating layer is silicon oxide.

10. The inductor according to claim 3 or 4, characterized in that: The iron-based amorphous alloy is carbonyl iron coated with an inorganic insulating layer.

11. The inductor according to any one of claims 1 to 4, characterized in that: The average particle size D1 of the magnetic particles of the first magnetic core is in the range of 2 μm≤D1≤20 μm, and the average particle size D2 of the magnetic particles of the second magnetic core is in the range of 2 μm≤D2≤20 μm.

12. The inductor according to any one of claims 1 to 4, characterized in that: The volume fraction P1 of the magnetic particles of the first magnetic core has a value range of 76.5%≤P1≤88%, and the volume fraction P2 of the magnetic particles of the second magnetic core has a value range of 76.5%≤P2≤88%.

13. The inductor according to any one of claims 1 to 4, characterized in that: The length L of the inductor is 1.8 mm ≤ L ≤ 2.2 mm, the width W of the inductor is 1.0 mm ≤ L ≤ 1.4 mm, and the thickness T of the inductor is T ≤ 0.8 mm.

14. The inductor according to any one of claims 1 to 4, characterized in that: The first magnet of the second magnetic core is a cylinder with an elliptical cross-section, a height of the first magnet is 0.3 mm, a major diameter of the cross-section of the first magnet is 1.2 mm, and a minor diameter is 0.5 mm; the second magnet is a rectangular parallelepiped, a length of the second magnet is 1.9 mm, a width of the second magnet is 1.0 mm, and a thickness of the second magnet is 0.2 mm.

15. The inductor according to any one of claims 1 to 8, characterized in that: The first magnetic core and the second magnetic core are formed by mixing magnetic particles, organic insulating materials and organic solvents, drying them, crushing them, filtering them, and finally pressing them in a mold; The mixing time is 1 hour, the temperature inside the mold is 150° C. during pressing, and the pressure is 500-600 MPa.

16. An electronic device, characterized in that: It comprises a main body and the inductor according to any one of claims 1 to 15, wherein the main body comprises a circuit board, and an electrode is provided outside the second magnetic core of the inductor, and the electrode is electrically connected to the circuit board.

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