An inductor structure and its fabrication method

Abstract

This invention belongs to the field of electronic component technology and discloses an inductor structure and its preparation method. The inductor structure includes: a base with mounting holes; a permanent core rod installed in the mounting holes of the base; a coil winding wound around the permanent core rod, with at least a portion of the free end of the coil winding folded around the surface of the base, the free end serving as an electrical connection portion for electrical connection with an external circuit; and a package tightly encapsulating the permanent core rod, coil winding, and base, with the electrical connection portion located on the outside of the package. The preparation method of the inductor structure includes the following steps: assembling a temporary core rod and base, winding the coil winding, processing the electrical connection portion, folding and fixing the coil winding, replacing the core rod, and processing into a finished product in a molding die. The above-mentioned inductor structure preparation method is simple to operate and has simplified steps, which shortens the production cycle while improving the yield rate of inductor products, resulting in low product loss and low impedance.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, and in particular to an inductor structure and its fabrication method. Background Technology

[0002] An inductor is a passive electronic component that stores electrical energy in the form of magnetic flux. An inductor has a certain inductance and only impedes changes in current. In circuits, inductors primarily function as filters, oscillators, delayers, and notch filters, as well as for signal filtering, noise filtering, current stabilization, and electromagnetic interference suppression. Due to these functions, inductors are widely used in various electronic products.

[0003] Existing conventional inductors include coreless inductors and cored inductors. Cored inductors mainly consist of a coil winding, a magnetic core, and auxiliary support and encapsulation materials. In the prior art, the magnetic core includes a base and a central rod extending vertically from the center of the base. The base and the central rod are an integral structure. The coil winding is wound around the central rod, and the two ends of the coil winding are respectively connected to two terminals located on the bottom surface of the base, as in the patent with authorization publication number CN 101553891 B.

[0004] The existing processing technology for this type of inductor is as follows: 1) First, a base containing a central column is made using an integral molding process; 2) Then, the coil winding is wound around the central column; 3) Insulating varnish is sprayed onto the coil winding, which serves to provide insulation, rust prevention (during hot pressing), and pressure resistance during coil processing, and to prevent wear during winding; 4) The free ends of the coil winding are folded and welded to two terminals located at the lower end of the base; 5) The above structure is then placed in a molding mold and filled with powder, and then hot-pressed and cured; 6) The molded inductor is then ground and chamfered, and then additional insulating varnish is sprayed; 7) The insulating varnish on the exposed terminal surface is then peeled off; 8) An electrode layer is then electroplated onto the peeled terminal surface for electrical connection with external circuits; thus, the basic manufacturing of the inductor is completed.

[0005] It is evident that existing cored inductors are not only structurally complex and have cumbersome manufacturing processes, resulting in high manufacturing and processing costs, but also easily damage the inductor surface during post-curing processing, affecting product qualification rates. Therefore, existing technologies need further improvement. Summary of the Invention

[0006] To address the above problems, this invention provides an inductor structure with a simple structure and a simplified fabrication process, as well as a fabrication method thereof.

[0007] To address the above problems, this application provides the following technical solution:

[0008] In a first aspect, this application provides an inductor structure comprising:

[0009] Base with internal mounting holes;

[0010] A permanent core post, one end of which is installed in the mounting hole of the base;

[0011] A coil winding is wound on the permanent core post, and the free end of the coil winding is at least partially folded around the base surface to achieve positioning on the base, with the free end portion serving as an electrical connection part for electrical connection with external circuitry.

[0012] The package tightly encapsulates the permanent core, coil windings, and base, with an electrical connection located on the outside of the package to allow the inductor to be connected to an external circuit via the electrical connection.

[0013] Optionally, in the inductor structure, the mounting hole is a through hole or a blind hole, and the shape of the horizontal base surface of the mounting hole is basically matched with the cross-section of the permanent core post.

[0014] Optionally, in the inductor structure, the permanent core is made of a soft magnetic material, and the hardness of the permanent core is lower than that of the coil winding.

[0015] Optionally, in the inductor structure, the free end of the coil winding may have less than one turn or more than one turn around the base to achieve fixation between the coil winding and the base.

[0016] Optionally, in the inductor structure, the electrical connection portion is located on the outer surface of the folded portion of the coil winding free end surrounding the base.

[0017] Optionally, in the inductor structure, the free end of the coil winding has a remaining end after the winding base is folded, and the end extends beyond the area covered by the package as an electrical connection portion.

[0018] Optionally, in the inductor structure, the number of coil windings mounted on the base is one, and an electrical connection part is formed at the corresponding positions of the two free ends; the electrical connection part is obtained by removing the insulating varnish layer from the surface of the coil winding and then tinning it.

[0019] Optionally, in the inductor structure, the two free ends of the coil winding are parallel to each other; or, the two free ends of the coil winding are arranged parallel to each other and perpendicular to each other, and the positions of the electrical connection parts on the two free ends do not interfere with each other.

[0020] Optionally, in the inductor structure, the outer side of the base is recessed to form a limiting groove for the free end of the coil winding to be wound and engaged; the cross-section of the coil winding is circular, elliptical, flat, or polygonal.

[0021] Optionally, in the inductor structure, two coil windings are installed on the base, namely a first coil winding and a second coil winding. The two windings are at least partially and alternately wound on a permanent core post, and each free end of each coil winding has an electrical connection portion.

[0022] Secondly, this application also provides a method for fabricating an inductor structure, which includes the following steps:

[0023] A temporary core post is installed in the mounting hole in the center of a base to complete the assembly of the two;

[0024] Part of the coil winding is wound along the axial direction of the core post, leaving two free ends of the coil winding for subsequent processes;

[0025] The insulating layer on the surface of the electrical connection part on the free end of the coil winding is removed and a conductive metal layer is attached. The electrical connection part is the part of the coil winding exposed outside the package in the finished inductor for electrical connection with external circuits.

[0026] The free end of the coil winding is folded along the surface of the base so that the folded electrical connection is outside the coverage area of ​​the subsequently formed package.

[0027] The temporary core post is removed and replaced with a permanent core post to form the inductor core structure;

[0028] The inductor core structure is placed in a molding die, and powder is filled into the molding die. After processing, the powder forms a package that encapsulates the inductor core structure, while exposing at least part of the electrical connection portion outside the package.

[0029] Optionally, in the method for preparing the inductor structure, the temporary core is made of a hard metal material and has a smooth surface.

[0030] Optionally, in the method for preparing the inductor structure, the method for removing the surface insulation layer of the electrical connection portion of the coil winding is laser stripping or mechanical stripping.

[0031] Optionally, in the method for preparing the inductor structure, the method for attaching a conductive metal layer to the electrical connection portion of the coil winding after removing the surface insulation layer is to perform a tinning process.

[0032] Optionally, in the method for preparing the inductor structure, the permanent core is made of a soft magnetic material, and the hardness of the permanent core is lower than that of the coil winding.

[0033] Optionally, in the method for preparing the inductor structure, the step of folding the free end of the coil winding along the surface of the base is as follows:

[0034] The base has one coil winding installed. The two free ends of the coil winding are folded at least twice along the surface of the base so that the free ends of the coil winding are wrapped together with the base and the electrical connection is located outside the base.

[0035] Optionally, in the method for preparing the inductor structure, the two free ends of the coil winding are parallel to each other and folded four times along the base, so that the electrical connection part is located on the bottom surface of the base and exposed.

[0036] Optionally, in the method for preparing the inductor structure, the side of the base is recessed to form a limiting groove for the free end of the coil winding to be wound and engaged, and the free end of the coil winding is engaged in the corresponding limiting groove of the base when folded along the surface of the base.

[0037] Optionally, in the method for preparing the inductor structure, in the step of winding a portion of the coil winding along the axial direction of the core post, the winding method of the coil winding adopts an external winding.

[0038] The present invention has the following beneficial effects:

[0039] 1. The inductor manufacturing method of the present invention ingeniously adopts the process of removing the paint and tinning the electrical connection parts in advance, setting it before the hot pressing step. This process optimization not only greatly simplifies the inductor process flow, making the hot pressing step the last process step and shortening the production cycle by at least 30%, but also effectively avoids the impact of late-stage paint removal and tinning on the yield of finished inductors, effectively improving the finished product qualification rate. At the same time, standardized production allows for rapid response, completely eliminating the dilemma of long waiting times for customized projects. The manufactured inductors have high structural integrity, low loss, and low impedance, giving them better market competitiveness.

[0040] Compared to traditional methods, the inductors prepared by the above method have higher saturation current, a 40% reduction in DCR, a 20% reduction in high-frequency loss, superior high-temperature resistance, extremely low interlayer high-frequency short circuits, and significantly shorter delivery cycles.

[0041] 2. The inductor of this application improves processing quality while reducing costs by separating the base and core, and cleverly using cores with different properties at different processing stages. Specifically, in the winding and coil free-end folding steps, temporary cores with higher hardness and smoother surfaces are used, which effectively avoids internal coil damage or cracks during winding and folding, prevents interlayer short circuits or interlayer defects, and results in higher structural integrity. Before hot pressing, the temporary cores are replaced with permanent cores made of soft magnetic material with lower hardness, which not only meets the performance requirements of the finished inductor for high-performance cores, but also effectively avoids coil damage caused by compression during hot pressing (in this process, the surface of the contacting cores is deformed to prevent damage to the coil surface during compression). The separate design of the base and core also effectively reduces inductor losses, reduces impedance, and reduces internal eddy currents.

[0042] Furthermore, since inductors have higher performance requirements for the core column than for the base, and the core column material is more expensive, by making the base and core column separate, the base can be made of low-cost materials that meet the usage requirements, which significantly reduces the manufacturing cost of the inductor.

[0043] 3. By replacing the permanent core with different specifications (such as different heights), the inductor can be given different performance characteristics, thus meeting the manufacturing requirements of inductors of different specifications. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the fabrication process of the inductor structure in Example 1;

[0045] Figure 2 This is a three-dimensional structural diagram of the inductor structure of Example 2, which is a perspective view;

[0046] Figure 3 This is a three-dimensional structural diagram of the inductor structure in Example 2;

[0047] Figure 4 This is a schematic diagram of different implementations of the coil winding's state before folding in Example 1;

[0048] Figure 5 A bottom view of the inductor structure for other implementations;

[0049] Figure 6 This is a process flow diagram of the inductor structure fabrication method in Example 1;

[0050] Figure 7 A is a cross-sectional view of the inductor structure; A is the inductor structure prepared in this application; B is the inductor structure prepared by existing processes.

[0051] The annotations in the attached figures are explained as follows:

[0052] 01 Temporary core post; 1 Permanent core post; 2 Base; 21 Mounting hole; 22 Limiting slot; 3 Coil winding; 31 Free end; 32 Electrical connection part; 4 Encapsulation body. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected to" another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," "upper," "lower," "inner," "outer," "bottom," etc., used in this specification indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. Furthermore, technical features involved in the different embodiments of the invention described below may be combined with each other as long as they do not conflict with each other.

[0056] Example 1

[0057] This embodiment provides a method for fabricating an inductor structure, such as... Figure 2As shown, the inductor structure prepared by this method includes: a base 2, a core rod installed at the center of the base, a coil winding 3 wound on the core rod, and a package 4. The package tightly wraps the core rod, the coil winding, and the base from the outside. The free end of the coil winding is folded along the surface of the base and has a section exposed outside the package. This exposed section is called the electrical connection part 32, so that the inductor can be connected to an external circuit through the electrical connection part.

[0058] Specifically, such as Figure 1 As shown, the method for fabricating the inductor structure includes the following steps:

[0059] S1. Provide a base 2 and a temporary core 01; install the temporary core 01 in the mounting hole of the base to complete the assembly of the two.

[0060] First, remove the inductor base 2 and temporary core 01, and then install the temporary core onto the base. The base is a flat base structure with a mounting hole 21 in the middle for inserting the core.

[0061] The mounting holes 21 of the base are through holes or blind holes, and the shape of the horizontal base surface of the mounting holes basically matches the cross-section of the permanent core. The cross-sections of the temporary core and the permanent core are circular, near-circular, or polygonal.

[0062] Because the temporary / permanent core and the base are separate components, the cross-sections of inductors of different specifications can be standardized (i.e., a standardized base can be used). Therefore, when manufacturing inductors of different specifications, a universal base can be used, along with temporary / permanent cores of varying lengths. This design further reduces the production cost of inductors.

[0063] The temporary core post 01 serves as a substitute for the permanent core post in the manufacturing process. On the one hand, it can act as a support for coil winding, facilitating the coil winding process. On the other hand, since the temporary core post is assembled with the base, the temporary core post also facilitates the fixation of the coil winding and the base during the folding process around the base, preventing relative displacement between the two in subsequent processes from affecting the product quality.

[0064] Since the core is used temporarily, it does not need to meet the specific performance-based material requirements of the inductor for the permanent core (such as containing soft magnetic materials). Its materials and settings are more flexible, and it can be made of lower-cost rigid materials. It can also avoid irreversible damage to the core during the coil winding and folding process.

[0065] Temporary core posts serve as temporary replacements and have the same specifications as permanent core posts, but the materials can be different.

[0066] Preferably, to avoid damage to the coil winding due to compression and friction with the temporary core post during processing in steps S1 to S4, the temporary core post 01 is made of a hard metal material with a smooth surface. The aforementioned high-hardness and smooth temporary core post has an extremely low surface friction coefficient, which not only better supports the coil winding but also protects the coil, effectively reducing damage to the coil winding in contact with it, improving the structural integrity of the coil winding, and effectively preventing the formation of pulls or cracks in the coil winding within the inductor. For example, the temporary core post is made of stainless steel or other high-hardness materials.

[0067] Specifically, the surface of the temporary core post can be made smooth through mirror treatment, such as by grinding and polishing, thereby reducing the coefficient of friction of the temporary core post surface.

[0068] The permanent core is made of soft magnetic material, making its hardness lower than that of the coil winding. The soft magnetic material can be made from existing iron-silicon alloys or various soft magnetic ferrites and thermosetting materials (such as resin). The permanent core has high permeability, high saturation, high insulation and high stability (inductance, fluidity, and low compression ratio (ensuring high density of the core, so that it is not easily deformed by pressure)).

[0069] The base is made of a mixture of thermosetting material (e.g., resin) and magnetic (or non-magnetic) metal powder (e.g., iron-based amorphous powder, iron-silicon-aluminum alloy powder, magnetically permeable alloy powder, iron-silicon alloy powder, iron-chromium-silicon alloy powder, nanocrystalline alloy powder, etc.).

[0070] The encapsulation material is made of a mixture of thermosetting material (e.g., resin) and magnetic metal powder (e.g., iron-based amorphous powder, iron-silicon-aluminum alloy powder, magnetically permeable alloy powder, iron-silicon alloy powder, iron-chromium-silicon alloy powder, nanocrystalline alloy powder, etc.), and is placed into a thermosetting mold with permanent core and coil winding by hot pressing, cold pressing, or cold pressing followed by hot pressing.

[0071] Optionally, the package and the base can be made of the same material. This arrangement can avoid color differences between the package and the base, resulting in better integration and a better appearance quality.

[0072] S2. Wind part of coil winding 3 along the axial direction of the core post. Leave the two free ends of the coil winding for subsequent folding processes.

[0073] In this embodiment, a coil winding is mounted on the core post. The two free ends extending from the coil winding after winding are located at both ends of the core post, and are subsequently used for folding.

[0074] In other embodiments, two coil windings, namely a first coil winding and a second coil winding, are mounted on the base. The two windings are at least partially and alternately wound on a permanent core post, and each free end of each coil winding has an electrical connection. Multiple sets of applications can be realized by connecting several coils in series.

[0075] Preferably, the coil winding is an outer-outer winding method. This winding method not only ensures that the specifications of each layer of coil winding are consistent, but also effectively avoids inter-layer short circuits.

[0076] S3. Remove the surface insulation layer (i.e., surface varnish layer) of the electrical connection portion 32 located at the free end of the coil winding and attach a conductive metal layer. The electrical connection portion is exposed outside the package after the inductor is manufactured, and is used to connect to external circuits.

[0077] In this embodiment, the two free ends 31 of the coil winding are arranged vertically and parallel to each other. In other embodiments, such as... Figure 4 As shown in B, the two free ends of the coil winding can also be set perpendicular to each other.

[0078] Preferably, the method for removing the surface insulation layer of the electrical connection portion 32 of the coil winding is laser stripping. Using laser stripping here allows for simultaneous processing of two electrical connection portions at different heights, resulting in high efficiency, precise enamel removal, no debris generation, and a cleaner finish.

[0079] In other embodiments, the insulating layer on the surface of the electrical connection can also be removed by mechanical stripping, but this process easily generates debris and cannot process two electrical connections simultaneously, resulting in lower efficiency.

[0080] In this embodiment, the method for attaching a conductive metal layer to the electrical connection portion 32 of the coil winding after removing the surface insulation layer is as follows: a tinning process is performed. This allows a layer of tin to be tightly adhered to the electrical connection portion. The advantages of the tinning process are: firstly, it enables precise positioning, because areas with the insulation layer remaining cannot be tinned; therefore, only the areas where the enamel has been removed will have a uniform tin layer attached precisely and firmly. Secondly, the tin layer formed by the tinning process not only gives the electrical connection portion better conductivity, but also has strong adhesion, preventing it from falling off during subsequent circuit board soldering or in the event of impact, thus improving the service life and reliability of the inductor product.

[0081] Currently, conventional electroplating is quite cumbersome, requiring the non-target areas to be masked first, then the target area to be electroplated, and finally the masking process for the non-target areas to be removed. Furthermore, the plating layer formed by electroplating is not firmly attached and is prone to peeling off.

[0082] S4. Fold the free end 31 of the coil winding along the surface of the base 2 so that the folded electrical connection is outside the package 4.

[0083] The electrical connection portion can be parallel to the surface of the package or set at a certain angle to the surface of the package.

[0084] In this embodiment, the number of coil windings installed on the base is one. The two free ends of the coil winding are wrapped around the surface of the base and folded at least twice, so that the free ends of the coil winding are tightly pressed together with the base, and the electrical connection is exposed outside the processed package.

[0085] In this embodiment, as Figure 3 As shown, in the inductor formed by subsequent processing, the electrical connection portion 32 is exposed parallel to the bottom surface of the package 4 and is flush with the bottom surface of the package, which facilitates subsequent circuit connection.

[0086] In other embodiments, the two electrical connection portions, after adopting a folding method not limited to this embodiment, may be located on the bottom surface or other side surface of the inductor's package, and the two electrical connection portions may be non-parallel, such as... Figure 5 As shown.

[0087] In this embodiment, preferably, as follows: Figure 1 As shown, the two free ends of the coil winding are parallel to each other and are wound around the base four times, almost one turn around the base, so that the electrical connection part is attached to the bottom surface of the base, thereby ensuring that it is exposed outside the bottom surface of the package after processing.

[0088] The above folding method achieves a firm fixation between the coil winding, electrical connection and base, and rapid positioning of the electrical connection while using a shorter free end, thus avoiding positional displacement of the electrical connection or internal structure during subsequent use or transportation, which would affect the inductor quality.

[0089] This setup not only simplifies the manufacturing process but also eliminates the step of welding the ends of the coil windings to the terminals of the base, which is a traditional method, thus improving manufacturing efficiency.

[0090] To prevent positional shift during rapid folding of the free end, a recessed groove 22 is formed on the side of the base to allow the free end of the coil winding to be wound and engaged. When the free end of the coil winding is folded along the surface of the base, it engages with the corresponding groove. The width of the groove is greater than or equal to the width of the coil.

[0091] In this embodiment, the cross-section of the coil winding 3 is flat. In other embodiments, the cross-section of the coil winding is circular, elliptical, or polygonal. In the wound state, the flat surface of the coil winding is perpendicular to the central axis of the core post 01.

[0092] S5. Remove the temporary core post 01 and replace it with the permanent core post 1 to form the inductor core structure.

[0093] Since most of the processes have been completed at this stage, replacing the temporary core with a permanent core at this point can maximize the function of the temporary core and protect the permanent core to the greatest extent.

[0094] The permanent core is made of soft magnetic material, and its hardness is lower than that of the coil winding.

[0095] The soft magnetic material can be made from existing iron-silicon alloys or various soft magnetic ferrites and thermosetting materials (such as resins).

[0096] There is a certain tolerance between the coil winding after winding and the temporary core post, that is, there is a certain gap. The surface of the temporary core post is smooth, so the removal of the temporary core post is relatively smooth and convenient and will not cause wear to the coil winding. Since the permanent core post is made of soft magnetic material with low material hardness, it is also not easy to wear down the contact coil winding.

[0097] S6. Place the inductor core structure into the molding mold and fill the molding mold with powder. After processing, the powder forms a package 4 that wraps around the inductor core structure, while exposing the electrical connection part 32 outside the package, thus completing the preparation of the inductor structure.

[0098] In this embodiment, the processing method is hot pressing. In other embodiments, cold pressing or cold pressing with hot pressing can also be used for processing. The inductor is fabricated through the above steps.

[0099] Since the stripping and tinning processes of the electrical connection parts are performed in advance in this method, the inductor processing steps are basically completed after step S6.

[0100] The powder comprises a mixture of curable magnetic powder and / or non-magnetic powder, such as magnetic metal or non-metal powder and thermosetting material (e.g., plastic).

[0101] Compared to existing processes, the inductor structure preparation method described in this application not only eliminates the need for painting the coil windings, but also cleverly advances the paint stripping and tinning processes of the electrical connections to the pre-processing stage, simplifying the process steps. This significantly shortens the production cycle while improving the yield of inductor products, effectively avoiding the impact of late-stage paint stripping and electroplating processes on the yield of finished inductors, effectively increasing the yield of finished products, improving the integrity of the internal structure of the product, reducing losses and impedance, and giving it better market competitiveness.

[0102] The inductor structure prepared by the method of this embodiment is smaller in size, saves more coil material, has higher structural reliability, less loss, and lower impedance, and has wide application value in actual production.

[0103] Example 2

[0104] This embodiment provides an inductor structure, which is prepared using the preparation method of Embodiment 1 of the present invention, such as... Figures 2-3 As shown, the inductor structure includes:

[0105] Base 2, with mounting holes 21 inside;

[0106] The permanent core post 1 is installed at one end in the mounting hole of the base 2;

[0107] The coil winding 3 is wound around the permanent core post 1, and the two free ends 31 of the coil winding are at least partially folded along the base surface, with the free ends serving as electrical connection parts 32.

[0108] The package 4 tightly encloses the permanent core, coil winding and base, and exposes at least a portion of the electrical connection portion 32 so that the inductor can be connected to an external circuit through the electrical connection portion.

[0109] Optionally, the mounting hole 21 of the base is a through hole or a blind hole, and the shape of the cross-section of the mounting hole matches the cross-section of the permanent core.

[0110] Optionally, in the inductor structure, the permanent core is made of a soft magnetic material, and the hardness of the permanent core is lower than that of the coil winding. The soft magnetic material can be an existing iron-silicon alloy or various soft magnetic ferrites, etc.

[0111] Optionally, the free end of the coil winding is folded around the base, and the number of turns can be less than one turn or more than one turn.

[0112] Preferably, the free end of the coil winding is folded around the base to secure both. This arrangement helps prevent the coil winding and base from shifting during subsequent processing or use, improving the internal structural stability of the inductor.

[0113] In this embodiment, the electrical connection portion is located on the outer surface of the folded portion surrounding the base at the free end. For example, in this embodiment, the electrical connection portion is located on the lower surface of the folded portion on the bottom surface of the base. Figures 2-3 Alternatively, in other embodiments, the electrical connection is located on the outer surface of the folded portion surrounding the side of the base. The electrical connection is at least partially exposed outside the package to enable electrical connection to external circuitry.

[0114] Optionally, the free end of the coil winding is placed close to the base surface. This arrangement further improves the stability of the connection between the coil winding and the permanent core.

[0115] In other embodiments, after the free end of the coil winding is fixed by folding around the base, a section remains at the end, which extends beyond the area covered by the package as an electrical connection portion (not shown in the figures). This is another way to implement the electrical connection portion, requiring a longer coil winding length.

[0116] In this embodiment, the number of coil windings installed on the base is one. The two free ends of the coil winding are folded along at least two adjacent surfaces of the base, and an electrical connection portion 32 is formed at the corresponding positions of the two free ends 31.

[0117] Specifically, the electrical connection portion is obtained by removing the insulating varnish from the surface of the coil winding and then applying tin. Optionally, the insulating varnish is removed by laser processing.

[0118] In this embodiment, the two free ends of the coil winding are parallel to each other.

[0119] In other embodiments, the two free ends of the coil winding are arranged perpendicularly to each other, and the positions of the electrical connections on the two free ends do not interfere with each other.

[0120] In this embodiment, the two electrical connection portions 32 are located parallel to each other on the same surface of the package body 4, such as the bottom surface, and each electrical connection portion is I-shaped.

[0121] In other embodiments, the electrical connection portions 32 on the two free ends of the coil winding are located on two adjacent surfaces of the package.

[0122] In other embodiments, a single electrical connection may be configured to be exposed on two adjacent surfaces of the package, for example, the electrical connection may be L-shaped and continuously distributed on two adjacent surfaces of the package.

[0123] In this embodiment, the free end of the coil winding is folded four times around the base surface. This arrangement provides a more stable connection between the coil winding and the base, ensuring that the processing quality and precision will not decrease due to changes in their relative positions during subsequent processing.

[0124] In this embodiment, the two free ends of the coil winding extend parallel from the upper and lower ends of the permanent core column and are folded and wound along the surface of the base, with the number of winding turns being close to one turn; the winding portion located on the bottom surface of the base forms an electrical connection portion.

[0125] In order to limit the free end of the fold, the outer side of the base is recessed to form a limiting groove 22 for the free end of the coil winding to be wound and locked.

[0126] In this embodiment, the limiting groove is an L-shaped slot located at the corner of the base. In other embodiments, the limiting groove is U-shaped. The width of the limiting groove opening is not less than the cross-sectional width of the coil winding.

[0127] In this embodiment, the cross-section of the coil winding is flat. The upper and lower adjacent coil layers are parallel to each other, meaning that the coil does not twist during winding.

[0128] In other embodiments, the cross-section of the coil winding is circular, elliptical, or polygonal.

[0129] Example 3

[0130] This embodiment provides an inductor structure that differs from Embodiment 2 in that: two coil windings, namely a first coil winding and a second coil winding, are mounted on the base. The two windings are at least partially and alternately wound on a permanent core post, and each free end of each coil winding has an electrical connection portion. Other configurations are the same as in Embodiment 2.

[0131] Test Implementation Examples

[0132] 1. Measure multiple properties of the inductor under test, including inductance after inductance change rate, inductance value under saturation current, etc.

[0133] In the experimental group, the inductor of Example 2 was used as the test object, while the control group was an inductor prepared using the conventional method mentioned above.

[0134] The drop ratio = the inductance value with saturation current applied / the inductance value without saturation current applied.

[0135] The inductor was sliced, and the shape of the slice was observed.

[0136] 2. Test Results

[0137] (1) Measurement results of inductance, descent ratio, and resistance:

[0138] The test results are shown in Table 1. The saturation current of the inductor in this application is significantly improved to 16.5A, which is better than the prior art (11A) and can adapt to higher operating current. In addition, the DCR (i.e. DC resistance) of the inductor in this application is as low as 6.072mΩ, which is 40% lower than the prior art and 20% lower in high frequency loss. Therefore, its high frequency loss during operation is also significantly reduced.

[0139] Table 2 shows the comparison results between the inductor of this application and the existing inductor of the comparison. It can be seen that the inductor has better high temperature resistance, extremely low interlayer high frequency short circuit, and significantly shorter delivery cycle.

[0140] Table 1 Comparison of inductance, descent ratio, and resistance values ​​of the two products

[0141]

[0142] Table 2 Comparison of existing inductors and inductors of this application

[0143]

[0144] (2) Observation of inductor cross-section

[0145] Observe a slice of the inductor structure under a magnifying glass, such as Figure 7 As shown in A, in the cross-section of the inductor structure prepared in this application, the multilayer coil structure sheets are neatly arranged, accurately positioned, and without deformation; Figure 7 In the inductor structure prepared by the existing process shown in B, the coil of the bottom layer of the structure on the left is significantly displaced, and the coil on the right side of the structure is deformed, tilting upward and converging, and also undergoing significant deformation. These will seriously affect the performance of the inductor.

[0146] Therefore, it can be seen that the inductor prepared by the method of this application has a complete structure without deformation, and thus has extremely low interlayer short circuit and more stable performance.

[0147] Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and concept of this invention, and all such changes or substitutions should fall within the protection scope of the appended claims.

Claims

1. A method for fabricating an inductor structure, characterized in that, Inductor structure includes: Base (2), with mounting holes (21) inside; A permanent core post (1) is installed at one end in the mounting hole of the base (2); The coil winding (3) is wound on the permanent core (1), and the free end (31) of the coil winding is at least partially wrapped around the base surface and folded to achieve positioning on the base. The free end portion serves as an electrical connection part (32) for electrical connection with an external circuit. The package (4) tightly wraps the permanent core, coil winding and base, and the electrical connection (32) is located outside the package so that the inductor can be connected to the external circuit through the electrical connection; The fabrication method of the inductor structure includes the following steps: Install a temporary core post (01) in the mounting hole (21) at the center of a base (2) to complete the assembly of the two; Part of the coil winding (3) is wound along the axial direction of the core post, leaving the two free ends of the coil winding for subsequent processes; Remove the insulating layer from the surface of the electrical connection part (32) on the free end of the coil winding and attach a conductive metal layer. The electrical connection part (32) is the part of the coil winding exposed outside the package (4) in the finished inductor for electrical connection with an external circuit. The free end of the coil winding is folded along the surface of the base so that the folded electrical connection is outside the coverage area of ​​the subsequently formed package (4); The temporary core post (01) is removed and replaced with the permanent core post (1) to form an inductor core structure; the hardness of the temporary core post is higher than that of the permanent core post, and the surface of the temporary core post is smooth. The inductor core structure is placed in a molding die, and powder is filled into the molding die. After processing, the powder forms a package (4) that encapsulates the inductor core structure, while exposing at least part of the electrical connection (32) outside the package.

2. The method for preparing the inductor structure according to claim 1, characterized in that, The temporary core (01) is made of hard metal material.

3. The method for preparing the inductor structure according to claim 2, characterized in that, The method for removing the insulating layer on the surface of the electrical connection portion (32) at the free end of the coil winding is laser stripping or mechanical stripping.

4. The method for preparing the inductor structure according to claim 3, characterized in that, The method for attaching a conductive metal layer is to perform a tinning process.

5. The method for preparing the inductor structure according to claim 1, characterized in that, The step of folding the free end of the coil winding along the surface of the base is as follows: The base has one coil winding installed. The two free ends of the coil winding are folded at least twice along the surface of the base so that the free ends of the coil winding are wrapped together with the base and the electrical connection is located outside the base.

6. The method for preparing the inductor structure according to claim 5, characterized in that, The two free ends of the coil winding are parallel to each other and folded four times along the base, so that the electrical connection is located on the bottom surface of the base and exposed.

7. The method for preparing the inductor structure according to claim 1, characterized in that, The base has a recessed side forming a limiting groove (22) for the free end of the coil winding to be wound and engaged. When the free end of the coil winding is folded along the surface of the base, it is engaged in the corresponding limiting groove of the base.

8. The method for preparing the inductor structure according to claim 1, characterized in that, In the step of winding part of the coil winding (3) along the axial direction of the core post, the winding method of the coil winding adopts the outer winding method.

9. The method for preparing the inductor structure according to claim 1, characterized in that, The mounting hole is either a through hole or a blind hole, and the shape of the cross-section of the mounting hole matches the cross-section of the permanent core post.

10. The method for preparing the inductor structure according to claim 1, characterized in that, The number of turns of the free end of the coil winding around the base is less than one turn or more than one turn, in order to fix the coil winding and the base.

11. The method for preparing the inductor structure according to claim 10, characterized in that, The electrical connection part (32) is located on the outer surface of the folded part of the coil winding base at the free end of the coil winding.

12. The method for preparing the inductor structure according to claim 10, characterized in that, The free end of the coil winding has a remaining end after the winding base is folded, and the end extends beyond the area covered by the package as an electrical connection (32).

13. The method for preparing the inductor structure according to claim 1, characterized in that, The number of coil windings installed on the base is one, and an electrical connection part (32) is formed at the corresponding positions of the two free ends (31); the electrical connection part is obtained by removing the insulating varnish layer from the surface of the coil winding and tinning it.

14. The method for preparing the inductor structure according to claim 13, characterized in that, The two free ends of the coil winding are parallel to each other; or, the two free ends of the coil winding are arranged parallel to each other and perpendicular to each other, and the positions of the electrical connection parts on the two free ends do not interfere with each other.

15. The method for preparing the inductor structure according to claim 12, characterized in that, The outer side of the base is recessed to form a limiting groove (22) for the free end of the coil winding to be wound and snapped; the cross-section of the coil winding is circular, elliptical, flat or polygonal.

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