Inductor and electronic equipment

Abstract

The invention provides an inductor and electronic equipment, the inductor comprises a first magnetic core, a coil and a second magnetic core, and the coil is wound on the second magnetic core; the coil and the second magnetic core are packaged by the first magnetic core; the first magnetic core comprises magnetic particles, the second magnetic core comprises magnetic particles, in the first magnetic core, 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, in the second magnetic core, the volume fraction of the magnetic particles of the second magnetic core is P2, the average particle size of the magnetic particles of the first magnetic core is D1, and the average particle size of the magnetic particles of the second magnetic core is D2. The average particle size of the second magnetic particles is D2; wherein P1 / P2 is greater than 1 and less than or equal to 1.15, and D1 + D2 is greater than or equal to 4 microns and less than or equal to 40 microns.

Description

Technical Field

[0001] The present application relates to the technical field related to power inductor devices, and in particular to inductors and electronic devices. Background Art

[0002] With the development of Internet technology and intelligent products, power inductors are an important component of power circuit components in the power circuits of small and thin devices such as smartphones. With the miniaturization of smart products, such as thinner foldable smartphones, high integrated functionality and flexible circuit board layout, the miniaturization and thinning of power inductors is an inevitable trend.

[0003] Common small power inductors have a structure in which a conductor coil is embedded in a magnetic core formed by an insulating magnetic material, and the two ends of the coil are connected to electrodes on the surface of the component, such as a chip inductor. The main difficulty in miniaturizing power inductors is how to ensure high magnetic permeability and good magnetic saturation performance of the inductor while reducing its size. Summary of the invention

[0004] The present application provides an inductor and an electronic device, wherein the inductor can ensure the performance of the inductor such as high magnetic permeability and good magnetic saturation under the premise of miniaturization.

[0005] The embodiment of the present application provides an inductor, the inductor includes a first magnetic core, a coil and a second magnetic core, 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, the first magnet is convexly arranged on the surface of the second magnet. The second magnetic core is located in the cavity and seals the cavity.

[0006] 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.

[0007] Among them, 1<P1 / P2≤1.15, 4μm≤D1+D2≤40μm.

[0008] 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, and 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 prevents magnetic flux leakage. Moreover, the sum of the average particle sizes D1 and D2 of the particles in the first magnetic core and the second magnetic core of the inductor provided in the present 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 the magnetic permeability in the first magnetic core and the second magnetic core is conducive to the miniaturization of the inductor.

[0009] 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 the first particle size, the particle size of the second magnetic particles is the second particle size, the particle size of the first magnetic particles is greater than the particle size of the second magnetic particles, that is, the first particle size is greater 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, the particle size of the third magnetic particles is greater than the particle size of the fourth magnetic particles, that is, the third particle size is greater 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 of large particle size are better filled by the particles of small particle size, which can improve 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 improve the magnetic permeability, and thus the magnetic permeability of the first magnetic core and the second magnetic core can be further improved.

[0010] In a specific embodiment, the second magnetic particles and the fourth magnetic particles are both composite magnetic particles, the composite magnetic particles include 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 particles and the third magnetic particles are both iron-based amorphous alloys. The first magnetic core and the second magnetic core both use two types of magnetic particles, and iron particles and iron-based amorphous alloys are selected at the same time to ensure 1<P1 / P2≤1.15, thereby ensuring the magnetic flux of the inductor.

[0011] 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 a core and a shell coated on the outer surface of the core, the 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 a core and a shell coated on the outer surface of the core, the 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 selected from 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.

[0012] In one embodiment, the inorganic insulating layer is silicon oxide. The iron-based amorphous alloy is carbonyl iron coated with an inorganic insulating layer.

[0013] In one embodiment, the first magnetic core also 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 also 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.

[0014] In the process of manufacturing the inductor, by adjusting the values ​​of W1 and W2, it is ensured that 1<P1 / P2≤1.15 can be ensured in the process of manufacturing the first magnetic core and the second magnetic core. In addition, the content of the first resin W1>1%, and the content of the second resin W2>1%. The strength and insulation of the first magnetic core 31 and the second magnetic core 32 can be ensured.

[0015] In one embodiment, based on the mass of the second magnetic core, the content W2 of the second resin is 3wt.%-4wt.%. The content of the second resin maintains the volume fraction of the magnetic particles of the second magnetic core and can provide sufficient strength to the second magnetic core to ensure that the second magnetic core will not break during the winding process of the coil.

[0016] 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.%.

[0017] 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 to 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 to increasing the saturation current.

[0018] In one embodiment, the volume fraction P1 of the first magnetic material is in the range of 76.5%≤P1≤88%, which can ensure 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%, which can avoid the insulation coating on the surface of the first magnetic material from being damaged due to excessive processing during processing, and can avoid the situation where the particles inside the first magnetic core are not combined.

[0019] 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, and then crushing, filtering and pressing the mixture in a mold; the first magnetic core is formed by a first composite magnetic material, wherein the first composite magnetic material is the same as the second composite magnetic material,

[0020] The coil is wound around the second magnetic core and placed into a mold, and the first magnetic core and the second magnetic core with the coil are formed by in-mold pressing;

[0021] The mixing time is 1 hour, the temperature inside the mold during pressing is 150° C., and the pressure is 500-600 MPa.

[0022] 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 long diameter of the cross-section of the first magnet is 1.2mm, and the short 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 manufactured in this embodiment can achieve miniaturization while ensuring magnetic permeability.

[0023] The embodiment of the present application also provides an electronic device, which includes a main body and the inductor, the main body includes a circuit board, and the second magnetic core of the inductor is provided with an electrode on the outside, and the electrode is electrically connected to the circuit board. Compared with the prior art, the inductor used in the electronic device of this embodiment can ensure the magnetic permeability, that is, it can ensure the overall performance index while achieving a miniaturized design, thereby saving the space occupied by the electronic device, which is conducive to the miniaturization of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the three-dimensional structure of an inductor provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the internal planar structure of an inductor provided in an embodiment of the present application;

[0028] Figure 4 for Figure 2 An electron image of a cross section of a magnetic core made of a composite magnetic material used in the inductor shown;

[0029] Figure 5 is a relationship diagram 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;

[0030] Figure 6 The (L×Idc / Rdc) of the embodiment of the present invention and the conventional embodiment is shown. 2 / V performance comparison;

[0031] Figure 7 The L / Rdc of the embodiment of the present invention and the conventional embodiment are shown. 2 With L×Idc 2 / V performance comparison;

[0032] Figure 8 The L / Rdc of the embodiment of the present invention and the conventional embodiment are shown. 2 Performance comparison. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0034] See also Figure 1 and Figure 2 , Figure 1A schematic diagram of the structure of an electronic device 100 provided in an embodiment of the present application.

[0035] The electronic device 100 described in the present application can be a mobile phone, a tablet computer, a navigator, a smart watch, etc. This embodiment is described in detail by taking a folding mobile phone as an example. Among them, for the convenience 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 reference to the attached Figure 1 The description of the orientation shown, with the positive direction of the Y-axis as the "top", the negative direction of the Y-axis as the "bottom", the positive direction of the Z-axis as the "up", the negative direction of the Z-axis as the "down", the positive direction of the X-axis as the "right", and the negative direction of the X-axis as the "left", 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 should not be understood as a limitation on the present application.

[0036] 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 devices and structural parts that realize various functions of the electronic device 100, 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 supporting structure that support the electronic devices. A power management chip 13 is also mounted on the circuit board 12, and the inductor 30 is mounted on the circuit board 12 and arranged 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 and 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 to ensure 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.

[0037] Please also read Figure 2 and Figure 3 , Figure 2 A schematic diagram of the three-dimensional structure of an inductor provided in an embodiment of the present application, wherein a partial internal structure of the inductor is shown; Figure 3 A schematic diagram of the internal planar structure of an inductor provided in an embodiment of the present application.

[0038] 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 convexly arranged on 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, which 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 the mold after the second magnetic core 32 and the coil 33 are formed and covers the second magnetic core 32 and the coil 33. The cavity is the part that accommodates the second magnetic core 32 and the coil 33 after the first magnetic core 31 is formed. When the inductor 30 is working, the coil 33 will generate a magnetic field after being energized. When the current of 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 value of the inductor 30, and the smaller the resistance value of the coil 33.

[0039] 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.

[0040] 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.

[0041] Figure 4 for Figure 2The electronic image of the cross section of the magnetic core made of the composite magnetic material used in the inductor shown in the figure; In another embodiment, the first magnetic core 31 and the second magnetic core 32 both have two kinds of magnetic particles. When the first magnetic core 31 and the second magnetic core 32 both have two kinds of magnetic particles, the first magnetic core 31 includes the first magnetic particles 311, the second magnetic particles 312 and the 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 the third magnetic particles (not shown), the fourth magnetic particles (not shown) and the second resin. The third magnetic particles and the fourth magnetic particles are dispersed in the second resin, and the third magnetic particles, the fourth magnetic particles and the second resin are mixed and pressed to form the second magnetic core. Wherein, the first resin and the second resin are thermosetting resins.

[0042] It should be noted that, for the sake of convenience in description, 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.

[0043] The volume fraction of the magnetic particles of the first magnetic core 31 is P1, the average particle size of the magnetic particles of the first magnetic core 31 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 32 is D2. The ratio between the volume fraction P1 of the magnetic particles of the first magnetic core 31 and the volume fraction P2 of the magnetic particles of 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 volume of the magnetic core, that is, the percentage of the magnetic particles in the total volume of the magnetic core. For example, the volume fraction of the magnetic particles of the first magnetic core 31 is based on the volume of the first magnetic core 31, that is, the percentage of the magnetic particles of the first magnetic core 31 in the volume of the first magnetic core 31. The average particle size of the magnetic particles of the first magnetic core 31 is D1, and the average particle size of the magnetic particles of the second magnetic core 32 is D2, both of which refer to the outer diameter of the magnetic particles. It should be noted that the particle size refers to the outer diameter of the magnetic particles, and the average particle size is the average value of the sum of the outer diameters of the magnetic particles of the magnetic core. The magnetic particles are spherical, elliptical or nearly spherical; it can also be understood that a single magnetic particle can take an average particle size, and the average particle size of the first magnetic core D1 and the average particle size of the magnetic particles of the second magnetic core 32 D2 can be the average value of the sum of the particle sizes of multiple magnetic particles in the magnetic core. Among them, the average particle size of the non-spherical single magnetic particle is taken, and then the sum of multiple magnetic particles is calculated to obtain the average particle size of the magnetic core.

[0044] 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%, which can ensure 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%, which can avoid the insulation coating on the surface of the second magnetic core 32 from being damaged due to excessive processing during processing, and can avoid the situation where the particles inside the second magnetic core 32 are not combined.

[0045] It can be understood that the greater the volume fraction P1 of the magnetic particles of the first magnetic core 31 and the volume fraction P2 of the magnetic particles of 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 reacts with the second magnetic core 32 to generate magnetic flux, and the magnetic flux circulates to the second magnetic core 32 through the first magnetic core 31, and the volume fraction of the magnetic powder particles used in the first magnetic core 31 and the second magnetic core 32 satisfies 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, and the first magnetic core 31 has a higher magnetic permeability than the second magnetic core 32, which reduces the magnetic flux leaked from the inductor 30, can ensure the power stored in the inductor 30, and effectively prevent the leakage of magnetic flux, which is more conducive to the miniaturization of the inductor 30; and avoids affecting the operation of other nearby electronic components.

[0046] The sum of the average particle size D1 of the magnetic particles of the first magnetic core 31 of the inductor 30 provided in the present application and the D2 of the magnetic particles of the second magnetic core 32 is in the range of 4μm≤D1+D2≤40μm. The larger the particle size of the magnetic particles, 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 of the magnetic permeability in the first magnetic core 31 and the second magnetic core 32 is conducive to the miniaturization of the inductor 30.

[0047] 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, the composite magnetic particles include a core and a shell coating the outer surface of the core, the 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, the composite magnetic particles include a core and a shell coating the outer surface of the core, the core is an iron particle, and the shell is an inorganic insulating layer.

[0048] Exemplarily, when the first magnetic core 31 and the second magnetic core 32 both have a type of magnetic particles, the first magnetic particles of the first magnetic core 31 and the third magnetic particles of the second magnetic core 32 are both composite magnetic particles. This can ensure high saturation magnetic induction of 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 can ensure high magnetic permeability and low core loss.

[0049] 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 2μm≤D1≤20μm. The average particle size of the third magnetic particles and the fourth magnetic particles in the second magnetic core 32 is D2, where 2μm≤D2≤20μm.

[0050] 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 particle 311 is the first particle size, the particle size of the second magnetic particle 312 is the second particle size, and the first particle size is greater 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 particle has a third particle size, the fourth magnetic particle has a fourth particle size, and the third particle size is greater than the fourth particle size. The first magnetic core 31 and the second magnetic core 32 both 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 magnetic particles with large particle sizes are better filled with the magnetic particles with small particle sizes, which can improve the stacking density of the magnetic material when processing the magnetic core; under the same unit, the density of the magnetic powder particles is increased, which can improve the magnetic permeability, and thus the magnetic permeability of the first magnetic core 31 and the second magnetic core 32 can be further improved.

[0051] In this embodiment, the second magnetic particles 312 of the first magnetic core 31 are composite magnetic particles, and 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, the shell layer is an inorganic insulating layer, and the first magnetic particles 311 are iron-based amorphous alloys. In one embodiment, specifically, the material of the inorganic insulating layer is silicon oxide, and the second magnetic particles are formed by carbonyl iron coated with the inorganic insulating layer.

[0052] The fourth magnetic particle is a composite magnetic particle, and the composite magnetic particle includes a core and a shell coated on 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. 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. Among them, 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 on the outside.

[0053] 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 cause the power loss of the inductor 30 to increase; 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 to say, when the magnetic permeability and saturation characteristics of the inductor 30 are met, the volume of the entire inductor 30 can be reduced to achieve miniaturization of the inductor, and the increase in the power loss of the inductor 30 can be avoided.

[0054] 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.

[0055] In one embodiment, the content of the first resin is W1 based on the mass of the first magnetic core 31, and the content of the second resin is W2 based on the mass of the second magnetic core 32, where W1<W2. The content of the first resin W1>1%, and the content of the second resin W2>1%, can ensure the strength and insulation of the first magnetic core 31 and the second magnetic core 32.

[0056] In one embodiment, based on the mass of the first magnetic core 31, the first resin content W1 in the first magnetic core 31 is 1wt.% to 4wt.%. Based on the mass of the second magnetic core, the second resin content W2 is 3wt.% to 4wt.%, so as to maintain the volume fraction of the magnetic particles of the second magnetic core 32 and provide sufficient strength to the second magnetic core 32 to ensure that the second magnetic core 32 will not break during the winding process of the coil 33.

[0057] The performance of the inductor 30 formed by combining the specific embodiments of the first magnetic core 31 and the second magnetic core 32 prepared from the above-mentioned composite magnetic material is further described below; the inductor sample prepared using the composite magnetic material of this embodiment is prepared by the same method as the method for 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 size as the first magnetic core 31 and the second magnetic core 32 of the comparative example.

[0058] Please refer to Table 1 and Table 2. Table 1 shows the process conditions and SEM image analysis of the inductor 30 made of the composite magnetic material of this embodiment and the inductor of the prior art. Table 2 shows the performance evaluation of the inductor made of the composite magnetic material of this embodiment and the inductor of the prior art.

[0059] 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 comparative examples of different volume fractions.

[0060] The specific steps for preparing the inductor are as follows:

[0061] Step S1, selecting magnetic particles for making a first magnetic core and a second magnetic core.

[0062] 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 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 iron-based amorphous alloy.

[0063] 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, wherein the mixing time is 1 hour; the solid content of the organic insulating material relative to the first magnetic core 31 is 1wt.% to 4wt.%. The organic insulating material is epoxy resin. The organic solvent content is 5%-12%.

[0064] 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, wherein 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 3wt.%-4wt.%. 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 3wt.%-4wt.%, so as to maintain the volume fraction of the metal powder and provide sufficient strength to the second magnetic core 32, so as to ensure that the second magnetic core 32 will not break during the winding process.

[0065] Specifically, the first resin content W1 included in the first magnetic core 31 is less than the second resin content W2 included 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.

[0066] 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 mesh size of 90 μm.

[0067] 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 for preparing the first magnetic core and the volume fraction of the magnetic material for preparing the second magnetic core can be adjusted.

[0068] 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.

[0069] Step S6: Place the preliminary magnetic core formed by the second magnetic core 32 and the coil 33 in a mold, cover it with the composite magnetic material formed by molding 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.

[0070] Table 1

[0071]

[0072]

[0073] It should be noted that there seems to be an incomplete part in the translation of step S6. The original text "压制制成第二磁芯32" is not clear in its full meaning. The above translation is based on the best understanding and completion of the context. If there are more specific requirements or corrections, please let me know.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, such as in sequence 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 sequence 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 kinds 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 in 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 magnitude of 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. When the magnetic particles of the first magnetic core 31 and the second magnetic core 32 are determined, P1 / P2 can be adjusted by adjusting the pressure and the resin content, and P1 / P2 directly affects the magnetic permeability of the inductor 30.

[0076] The performance of the above inductor is verified below in conjunction with 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 the 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 increases during operation. 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 of the properties 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 of the inductor 30 is the power efficiency index, which can be expressed as L / Rdc 2 When the second magnetic core 32 of the inductor 30 is wound with a coil having the same cross-sectional area, the inductance value L is proportional to the square of the number of turns of the coil, and Rdc is proportional to the length of the coil, which can be understood as being 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, and the inductance value L will also increase and be constant. Then the number of turns of the coil can be reduced, thereby reducing the DC resistance Rdc. It can be understood that the larger the 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, saturation current, DC resistance and volume.

[0078] Table 2

[0079]

[0080]

[0081] As shown in Table 2, the P1 / P2 of the sample inductor 30 is greater than 1, and the overall performance index (L×Idc / Rdc) of the inductor 30 of the sample embodiment is 2 / V ratio Overall performance index of all comparison ratios (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.

[0082] From Table 2, it can be confirmed 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 varies with the size of D1+D2, L / Rdc 2The higher the value, the overall performance index of the inductor 30 can be improved by adjusting the particle size and volume fraction of the first magnetic core 31 and the second magnetic core 32 of the inductor 30. In other words, increasing the particle size of the magnetic particles of the first magnetic core 31 and the second magnetic core 32 can improve the magnetic permeability, which is beneficial to 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 31 and the second magnetic core 32 to a smaller size is beneficial to increasing the saturation current. Under the premise of ensuring that it is beneficial to reduce the size of the inductor, the influence of the magnetic permeability and power consumption of the overall magnetic particles is comprehensively considered to finally determine the appropriate particle size and volume fraction.

[0083] See also Figure 5 , Figure 5 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, the relationship between the magnetic permeability and the DC magnetic field of the magnetic material (magnetic particles) used in the inductors of the embodiments No. 4, No. 5, No. C-2 and No. E1 in Table 1. The above four magnetic materials are processed into ring samples, wound and the magnetic permeability is measured at 1MHz while applying a DC bias current to obtain their characteristic curves. The DC bias characteristics of the L value of the inductor can be obtained by Figure 6 The DC magnetic field H shows the effect of the magnetic permeability μ 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.

[0084] Figure 5 The characteristic curve of the first magnetic material is the magnetic material used in the first magnetic core 31 of Comparative Example C2 in Table 1 and Table 2. The magnetic permeability of this material decreases by 30% when the DC magnetic field is 13.3 kA / m. Idc of Comparative Example C2 represents the current value required to apply an average magnetic field of 13.3 kA / m to the inductor magnetic core and reduce the magnetic permeability by 30%.

[0085] Figure 5 The characteristic curve of the second magnetic material is a curve obtained by increasing the volume fraction of the magnetic powder particles of the first magnetic material; as in sample embodiment 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 a higher overall performance index is exhibited than that of comparative example C2 by increasing the inductance L value without significantly reducing Idc.

[0086] Figure 5The characteristic curve of the third magnetic material 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 the 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 it has a high magnetic permeability within a larger operating current range, and reduces the magnetic flux leaked from the inductor 30, effectively inducing the magnetic flux in the second magnetic core 32, thereby improving the electromagnetic performance.

[0087] Figure 5 The characteristic curve of the fourth magnetic material is a curve of a magnetic powder material having a lower volume fraction and a larger average particle size than the first magnetic material. This curve has a higher magnetic permeability when the DC bias magnetic field is 0 due to the large particle size of the magnetic powder particles, but as the applied DC bias magnetic field increases, the magnetic permeability drops sharply and is lower than that of the first magnetic material. Reflecting this characteristic curve, it is assumed that 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 a lower Idc and overall performance index relative to comparative example C2 and the sample embodiment.

[0088] According to the above embodiments and comparison results, it can be understood that the volume fraction of the 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 magnetic core becomes too low, and a larger number of turns or coils is required to obtain a constant L value, which in turn causes a significant increase in Rdc. When the volume fraction of the magnetic particles of the second magnetic core 32 is calculated from the SEM image, 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 the magnetic particles in the first magnetic core 31 is less than or equal to 88%. When the volume fraction of the 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 destroyed due to excessive processing during the stamping process, and there are many places where metal powder bonding occurs inside the magnetic core. And during the driving process, the eddy current flowing between the magnetic metal powders increases, resulting in a significant decrease in the L value at the driving frequency. In addition, the destruction of the insulating coating will damage the insulation performance of the magnetic core. From the upper limit of P1 (88%) and the lower limit of P2 (77%), the upper limit of P1 / P2 is 1.15. When preparing 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, so that the inductor obtains a good overall performance index.

[0089] The lower limit of D1+D2 is 4μm because the lower limit of the particle size of the magnetic particles used for the first magnetic core 31 and the second magnetic core 32 is 2μm. If a magnetic particle size less than 2μm is 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 obtain a volume fraction of 77% or more 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 for the first magnetic core 31 and the second magnetic core 32 is both 20μm. If magnetic particles larger than 20μm are used, when the inductor 30 is driven, the eddy current generated in the corresponding magnetic powder increases, and the magnetic permeability of the magnetic core at the driving frequency is greatly reduced, resulting in a reduced L value.

[0090] See Table 3 and Figure 5 Table 3 shows the size and performance measurement results of the inductor 30 of the prior art (conventional technology) and the present embodiment. In order to verify the effect of reducing the size of the inductor 30 by applying the present invention, each surface of the inductors of Examples 4 and 11 was polished to reduce the chip size (adjust the inductor size), and the characteristics were evaluated compared with the conventional embodiment C1. Performance indicators (L×Idc / Rdc) of Example 4 and Example 11 2 / V is 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 the performance is the same as that of the traditional inductor 30. L, W and T in Table 3 refer to the height, width and thickness of the inductor respectively, which can be referred to in conjunction with Figure 2 4' and 11' in the table are the characteristics of the samples of Examples 4 and 11 whose surfaces were 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 the values ​​of C1 of the same volume before polishing.

[0091] It can be understood that Figure 2 The inductor shown is a sample inductor made by 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 maximum value of the thickness T is 0.8 mm. Through this verification, it is confirmed that the magnetically compatible 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 long diameter of the cross section of the first magnet 322 is 1.2 mm, and the short diameter is 0.5 mm; the second magnet 321 is a cuboid, 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.

[0092] Table 3

[0093]

[0094]

[0095] 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.

[0096] The inductor 30 sample of the above-mentioned embodiment can be tested to obtain the volume fraction P1 of the magnetic particles in the first magnetic core 31 of the actual sample inductor 30, the average particle size D1 of the magnetic particles in the first magnetic core 31, the volume fraction P2 of the magnetic particles in the second magnetic core, and the average particle size D2 of the magnetic particles in the second magnetic core 32.

[0097] And test performance parameters, such as μ-H curve, inductance value L, DC resistance Rdc and rated current Idc.

[0098] The values ​​of D1, D2, P1 and P2 of the inductor sample are tested. First, the prepared inductor sample is made into a metallographic sample (the inductor is embedded in a mold and polished until the cross section of the second magnetic core 32 can be seen), and the metallographic sample of the inductor is surface polished by an ion polisher to make the surface of the cross section smoother and clean the surface impurities, so that the magnetic particles can be tested more clearly. Among them, the appearance size of the inductor sample can be measured by a spiral side micrometer.

[0099] Then, a scanning electron microscope (SEM) was used to magnify the metallographic sample (cross section) of the inductor by 500 times in the backscattering mode, and three scattered electron signal (BSD) photos were taken; finally, the Winroof image analysis software was used to analyze each BSD photo to obtain the parameters D1, D2, P1, and P2, and then the average value of each parameter of the three photos was taken. Finally, the D1, D2, P1, and P2 values ​​of the inductor sample were obtained.

[0100] Test the performance parameters of the inductor sample. μ-H curve, using a vibrating sample magnetometer, for example, put the magnetic particle sample of the inductor into a magnetic field, and vibrate the sample magnetic particle sample, and obtain the μ-H curve as the magnetic field changes through a probe, etc. Equipment model: TOEI VSM (Type 5-15).

[0101] To test the inductance value L of the inductor sample, an impedance analyzer is used under the test conditions of 1MHz and 0.5V. The equipment model used is: Agilent4991A impedance analyzer. A microohmmeter can be used to test the Rdc of the inductor sample; of course, any test equipment with equivalent performance can be used. To test the Idc of the inductor sample, a Microtest 6575 impedance analyzer and a programmable current source (used to control the DC current of the inductor) are used. Specifically, the inductor sample is placed on the test fixture of the impedance analyzer, the DC-bias function is turned on, and the DC current loaded on the inductor is gradually increased until the L value is confirmed under the conditions of 1MHz and 0.5V, and then L is reduced by 30% of the current to obtain the Idc value.

[0102] See also Figures 6 to 8 ,in, Figure 6 The (L×Idc / Rdc) of the embodiment of the present invention and the conventional embodiment is shown. 2 / V performance comparison. The materials of the first magnetic core and the second magnetic core used in the inductor and the corresponding performance indicators, wherein P1 / P2 is 1.01 to 1.15, and D1+D2 is 4 to 40 μm, that is, the embodiment of the present invention obtains performance indicators that are better than those of the conventional embodiment and the embodiment.

[0103] Figure 7 The L / Rdc of the embodiment of the present invention and the conventional embodiment are shown. 2 With L / Idc 2 Performance comparison, Figure 8 The L / Rdc of the embodiment of the present invention and the conventional embodiment are shown. 2 The embodiments of the present invention are shown to have lower power consumption and better overall performance index than conventional embodiments. In more detail, the performance characteristics vary with the size of D1+D2, such as Figure 7 The larger the D1+D2, the greater the L / Rdc 2 The higher the value of; this characteristic shows that the overall performance of the inductor can be improved by properly setting the powder particle size according to the performance parameters to be concerned in the inductor design.

[0104] The above are only some embodiments and implementation methods of the present application, and the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope 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.

Images