Coil parts

Abstract

To provide a structure in which an air gap is minimized inside a core in which a wire-wound coil is embedded. [Solution] The present invention relates to a coil component including a main body including a wire-wound coil and a core in which the wire-wound coil is embedded, and an external electrode disposed on the outer surface of the main body. The core includes first and second cores, and the first and second cores have a structure in which the first and second cores are joined to each other with a joining surface sandwiched therebetween.

Description

[Technical field]

[0001] The present invention relates to a coil component, and more particularly to a wire-wound power inductor. [Background technology]

[0002] Recently, with the trend of miniaturization and multi-functionalization of electronic products, inductor elements are also required to be miniaturized. In particular, mobile devices such as smartphones require higher currents due to the diversification of functions. Such mobile devices obtain operating power of various voltages required for internal circuits using power circuits such as DC-DC converters. Inductors used in such circuits require high permeability materials that have the characteristics of suppressing magnetic saturation and high inductance. Since the inductance of an inductor is proportional to the permeability, a high inductance inductor can be manufactured by using a material with high permeability, and the same level of characteristics can be obtained with fewer turns compared to when a material with low permeability is used. However, even when a material with high permeability is used, if an air gap occurs in the inductor, magnetic resistance increases, resulting in a decrease in permeability. Of course, when a material with high permeability is used, the effect of the air gap is relatively small compared to when a material with low permeability is used, and a gradual decrease in permeability is observed, but when there is a limit to selecting a high permeability material to improve permeability, it is necessary to minimize the air gap. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-009644 A Summary of the Invention [Problem to be solved by the invention]

[0004] One of the various problems that the present invention seeks to solve is to provide a structure that minimizes air gaps inside a core in which a wire-wound coil is embedded. [Means for solving the problem]

[0005] A coil component according to an embodiment of the present invention includes a body including a wire-wound coil, first and second cores respectively disposed on an upper and lower part of the wire-wound coil and connected to each other, and first and second external electrodes disposed on an outer surface of the body and connected to first and second ends of the wire-wound coil, respectively. A joint surface is disposed between the first and second cores, and the joint surface includes the same type of resin as the resin contained in the first and second cores. Effect of the Invention

[0006] Among the various advantages of the present invention, one advantage is that it provides a coil component having a structure that can maximize inductance and permeability while minimizing chip size. [Brief description of the drawings]

[0007] [Figure 1] 1A to 1C are diagrams showing coil components according to the prior art. [Diagram 2] FIG. 2 is a schematic exploded perspective view showing a state before a main body of a coil device according to an example of the present invention is assembled. [Diagram 3] FIG. 2 is a schematic perspective view showing a state after a main body of a coil component according to an example of the present invention has been assembled. [Figure 4] FIG. 4 is a cross-sectional view of region A shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view according to a modified example of FIG. [Figure 6] 2A is an enlarged view showing the boundary area between the first and second cores in the coil component of the present invention, and FIG. 2B is an enlarged view showing the boundary area between the first and second cores in a conventional coil component manufactured according to the method of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments of the present invention will be described with reference to specific embodiments and the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those having average knowledge in the art. Therefore, the shapes and sizes of elements in the drawings may be enlarged or reduced (or highlighted or simplified) for clearer explanation, and elements indicated by the same reference numerals in the drawings are the same elements.

[0009] In order to clearly explain the present invention, parts that are not relevant to the explanation are omitted in the drawings, thicknesses are enlarged to clearly show various layers and regions, and the same reference symbols are used for components that have the same functions within the same concept.

[0010] Furthermore, throughout the specification, the term "comprising" an element means that it may further include other elements, not that it excludes other elements, unless specifically stated to the contrary.

[0011] A coil component according to an example of the present invention will be described below, but the present invention is not necessarily limited to this.

[0012] 1(a) to (c) show coil parts according to the prior art. Specifically, Fig. 1(a) shows a process of embedding a wire-wound coil inside the first and second cores by crimping the first and second cores using a mold, Fig. 1(b) shows only the first core disposed at the bottom, and Fig. 1(c) is a schematic perspective view showing a structure in which the first and second cores are joined together.

[0013] 1(a), a process is performed in which a predetermined wire-wound coil 52 is fixed between a first core 511 and a second core 512 using a die or a punch. At this time, a joint surface 513 is inevitably formed between the first and second cores.

[0014] The bonding surface 513 is generated by an adhesive 513a for bonding the first and second cores as shown in Fig. 1(b). The adhesive 513a can be appropriately selected by those skilled in the art, and any material can be used as long as it can bond the first and second cores. However, the adhesive 513a generally remains between the first and second cores even after the first and second cores are bonded.

[0015] 1(c), a joint surface 513 with a certain thickness remains between the first and second cores 511 and 512. However, this joint surface does not smooth the flow of magnetic flux generated from the coil, and may result in leakage of magnetic flux. In addition, an air gap with a certain thickness is likely to be generated around the joint surface, and such an air gap may reduce inductance.

[0016] In addition, the air gap at the joint surface and its periphery may cause problems with the reliability of insulation between the magnetic powder particles in the environment in which the product is actually used. When the first and second cores are molded using high pressure, a part of the coating layer that coats the magnetic powder in the area that comes into contact with the mold is damaged, and the damaged coating layer reduces the inductance in the usage environment. This may cause problems with reduced characteristics in the manufacturing environment.

[0017] A coil device 100 according to an embodiment of the present invention has a modified structure for joining the first and second cores in order to solve the above problems that may arise from the conventional coil device shown in Fig. 1. Therefore, the following description will focus on the joining surfaces of the first and second cores.

[0018] FIG. 2 is a schematic exploded perspective view showing a state before the main body 1 of the coil device 100 according to an embodiment of the present invention is assembled.

[0019] Referring to FIG. 2, the main body 1 includes a first core 11 covering the upper surface and a second core 12 covering the lower surface based on the wound coil 2. The assembly of the first and second cores requires a medium to prevent the first and second cores from being separated from each other. For example, if the first and second cores are fixed only by high pressure, it goes without saying that sufficient fixing force cannot be secured, and the coating layer on which the magnetic powder is coated inside the first and second cores may be damaged. On the other hand, if the first and second cores are fixed by adhesive, the flow of magnetic flux may be hindered due to air gaps formed around the adhesive or residual adhesive.

[0020] 2, a solvent 3 is located on the upper surface of the first core 11. The solvent 3 is sufficient as long as it functions to dissolve the resin contained in the first and second cores, and there is no restriction on the specific type of solvent. The solvent 3 is completely removed from the final coil component, so that the resin in the first core and the resin in the second core can be directly bonded to each other.

[0021] Meanwhile, Fig. 3 is a schematic perspective view showing a final coil component 100 after assembling the main body of the coil component according to an embodiment of the present invention. Referring to Fig. 3, a joint surface 13 is formed between the first and second cores 11, 12. This joint surface 13 is distinguished from the joint surface 513 in Fig. 1 described above. The joint surface 513 in Fig. 1 is a remaining adhesive and is formed of a material having a different composition from the first and second cores, whereas the joint surface 13 in Fig. 3 is formed by dissolving the resin of the first and second cores in a solvent 3 and then hardening. That is, no adhesive is detected at or around the joint surface 13 in Fig. 3.

[0022] The coil component further includes external electrodes connected to both ends of the wire-wound coil 2 within the body, and the coil component can be electrically connected to an external component by the external electrodes.

[0023] Fig. 4 is a schematic cross-sectional view enlarging region A in Fig. 3. The insides and bonding surfaces of the first and second cores will be described in more detail below with reference to Fig. 4.

[0024] Referring to FIG. 4, the first and second cores 11 and 12 are composed of magnetic powder 41 and resin 42 that coats the surface of the magnetic powder. The magnetic powder 41 can be used without limitation as long as it has magnetic properties, and can be formed of at least one selected from Fe, Fe-Ni alloy, Fe-Si alloy, Fe-Si-Al alloy, Fe-Cr-Si alloy, Fe-based amorphous alloy, Fe-Co alloy, Fe-N alloy, MnZn ferrite, NiZn ferrite, etc. In other words, the magnetic powder can be selected without limitation as long as it is a particle having magnetic properties. The magnetic powder is directly coated with resin without a separate oxide layer. Here, the separate oxide layer means a separate inorganic layer for insulating the coated magnetic powder, and includes all coating layers formed by, for example, a part of the composition inside the magnetic powder diffusing to the surface and reacting with oxygen.

[0025] In addition, the content of residual hardener or binder other than the magnetic powder and resin in the first and second cores is 0 wt%. This means that no additional hardener or binder was added from the outside other than the resin constituting the first and second cores. Generally, the hardener or binder is unavoidably left at a certain content. However, the coil component of the present invention uses the resin coating the magnetic powder as a hardener and binder, so no additional hardener or binder is applied.

[0026] The magnetic powder has no insulating layer other than the resin 42 between it and other adjacent magnetic powders. This minimizes the distance between the magnetic powders in coil components, which tend to be miniaturized, and maximizes the magnetic permeability of the coil components.

[0027] The resin 42 is a thermosetting resin, and preferably an epoxy resin. When the resin 42 is an epoxy resin, various types of epoxy resins are adopted according to the required characteristics of the magnetic powder. For example, when high resistance insulating characteristics are required, an epoxy resin without a benzene ring can be adopted.

[0028] There is no limitation on the method of forming a structure in which the surface of the magnetic powder is coated with resin and only the resin is disposed between adjacent magnetic powders, but for example, when the entire first core or the entire second core is taken as 100 wt%, it is preferable that the weight ratio of the resin to the magnetic powder is 1% or more and 5% or less. After selecting a magnetic powder that exhibits the desired characteristics, the magnetic powder and the resin are mixed and stirred in a dry or wet manner using a V-type mixer, a ball mill, a bead mill, or various rotary mixers. At this time, mixing is selectively performed for 5 minutes to 200 hours. When wet stirring is used as the stirring, it is also possible to dry using a fluidized bed dryer, a spray dryer, or the like.

[0029] Next, in order to bond the first core and the second core obtained by the above process, a solvent is prepared to dissolve the resin used in forming the first and second cores. Different types of solvents can be selected according to the resins in the first and second cores, and those skilled in the art will select an appropriate solvent taking into consideration the manufacturing environment, process requirements, etc.

[0030] The solvent is placed on the surface of the first core that contacts the second core, so that at least a part of the resin on the upper surface of the first core and at least a part of the resin on the lower surface of the second core facing the upper surface are bonded to each other. The solvent can act as a driving force for bonding the first and second cores while dissolving the resin in the first and second cores. The dissolution by the solvent creates a driving force for bonding the first and second cores, and as a result, the resin on the upper surface of the first core and the lower surface of the second core are both cured to form an integrated core. Of course, a wire-wound coil is embedded inside the core.

[0031] Before the solvent is applied, the first and second cores already have the magnetic powder coated with resin, so the adhesive strength between the first and second cores can be maintained by simply applying a thin layer of low-viscosity solvent.

[0032] When the components of the joint surface 13 are analyzed, no solvent remains after dissolving the resin, and no adhesive is added from the outside other than the solvent, so no components other than the hardened resin are detected in the first and second cores. However, the joint surface is a layer formed by the resin that has been rehardened after dissolving, unlike the resin that coats the magnetic powder in the area excluding the upper surface of the first core and the resin that coats the magnetic powder in the area excluding the lower surface of the second core. Here, the reason why the joint surface is called a "layer" is because the joint surface 13 is arranged in a strip shape based on the LW cross section. The layer thickness of the joint surface is not greatly limited, and does not need to be uniform, but it is preferable that the maximum layer thickness is less than 1 μm. In practice, the layer thickness T of the joint surface 13 can be defined as the shortest distance between the magnetic powder in the first core and the magnetic powder in the second core. Therefore, when the maximum layer thickness of the joint surface 13 is 1 μm or more, it means that the distance between the magnetic powders is so far apart that high magnetic permeability characteristics cannot be maintained. On the other hand, although not specifically shown, the joint surface 13 is not formed on the entire boundary surface between the first and second cores, but is formed in a band shape having a predetermined thickness, extending in the length direction and / or width direction of the main body only in a partial region. A joint surface made of resin is not arranged on the same plane as the band-shaped joint surface, and a space is formed where one surface of the magnetic powder in the first core and one surface of the magnetic powder in the second core contact each other. The contact between one surface of the magnetic powder in the first core and one surface of the magnetic powder in the second core means that the first and second cores are in direct contact with each other without the joint surface being interposed.

[0033] Meanwhile, FIG. 5 is a cross-sectional view according to a modified example of FIG. 4, and the coil part of FIG. 5 has a void layer 6 formed around the joint surface. The void layer 6 is an air gap that may occur when actually manufacturing a coil product. As described above, since the air gap can be a major cause of increasing the magnetic resistance, it is preferable to minimize it, but it is an unavoidable layer. When the first and second cores are bonded using an adhesive paste according to the conventional method, the adhesive paste must be applied relatively thickly to ensure sufficient adhesive strength, and as a result, it is unavoidable that the air gap is also formed relatively thick. However, the void layer 6 around the joint surface 13 in the coil part of FIG. 5 is quite thin, with a thickness of less than 1 μm. This is to the extent that it does not substantially affect the decrease in inductance. The reason why the thickness of the void layer 6 can be controlled on a nanoscale in this way is that by applying a solvent that can dissolve the resin that constitutes the first and second cores, a part of the resin can be directly used as the joint surface, and there is no need to apply an additional adhesive to the boundary surface of the first and second cores. The reason why the void layer 6 is made thin will be described in more detail with reference to FIG.

[0034] Fig. 6(a) is an enlarged view showing the periphery of the boundary between the first and second cores in the coil component of the present invention, and Fig. 6(b) is an enlarged view showing the periphery of the boundary between the first and second cores in a conventional coil component manufactured according to the method of Fig. 1. Figs. 6(a) and 6(b) show the case where the size of the coil component is the rated size of 5050 (width: 5.0 mm, length: 5.0 mm).

[0035] 6(a), the boundary between the first core and the second core can be distinguished through the thin band-shaped joint surface, but the air gap between the first core and the second core is minimized and the degree of the air gap formed within the first core and the second core itself is not distinguished.

[0036] However, in the case of Fig. 6(b), the boundary between the first and second cores in the conventional coil component is clearly distinguished by the air gap. Specifically, it can be seen that an air gap layer of about 23.13 μm is formed around the above-mentioned boundary. Therefore, in the case of the conventional coil component in Fig. 6(b), it is clear that the air gap significantly reduces the inductance.

[0037] According to the coil component of the present invention, in spite of the active development of high permeability materials, it is currently difficult to develop a coil component having high permeability and high inductance. In this situation, the resin contained in the first and second cores is melted and then re-hardened to form a joint surface without adding a separate adhesive, thereby minimizing magnetic resistance and providing a coil component with high inductance.

[0038] Although the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereto, and that various modifications and variations are possible within the scope of the technical idea of ​​the present invention described in the claims.

[0039] Meanwhile, the expressions "one example" and "another example" used in the present invention do not mean the same embodiment, but are provided to emphasize and describe unique features that are different from each other. However, the above-mentioned one example does not exclude being realized in combination with features of another example. For example, even if a matter described in a particular example is not described in another example, it can be understood as being a description related to the other example, unless there is a description in the other example that is opposite or contradictory to the matter.

[0040] In addition, the terms used in the present invention are merely explained to explain an example, and are not intended to limit the present invention. In this case, the singular expression includes the plural, unless the context clearly indicates otherwise. [Explanation of symbols]

[0041] 100, 100' coil parts 1 Main unit 11 First Core 12 Second Core 13 Joint surface 3. Solvent 2 Winding Coil 6 Void Layer

Claims

1. a main body including a wire-wound coil and first and second cores disposed on an upper portion and a lower portion of the wire-wound coil, respectively, and connected to each other; external electrodes disposed on an outer surface of the body and coupled to both ends of the wire-wound coil; a joint surface is disposed between the first and second cores; the joint surface is made of a resin that is formed by dissolving a part of the resin contained in the first and second cores and then re-hardening the resin, Each of the first and second cores includes a magnetic powder and a resin that directly coats the surface of the magnetic powder and has a weight ratio of 1% to 5% when the entire first core or the entire second core is taken as 100% by weight. Coil parts.

2. The coil component according to claim 1 , wherein the resin is a thermosetting resin.

3. The coil component according to claim 2 , wherein the thermosetting resin is an epoxy resin.

4. The coil component according to claim 1 , wherein adjacent ones of the magnetic powder particles are insulated from each other only by the resin.

5. The coil component according to claim 1 , wherein a surface of the magnetic powder does not include an inorganic layer having a composition identical to or different from a composition constituting the magnetic powder.

6. The coil component according to any one of claims 1 to 5, wherein the magnetic powder includes one or more selected from the group consisting of Fe, Fe-Ni based alloy, Fe-Si based alloy, Fe-Si-Al based alloy, Fe-Cr-Si based alloy, Fe based amorphous alloy, Fe based nanocrystalline alloy, Co based amorphous alloy, Fe-Co based alloy, Fe-N based alloy, MnZn based ferrite, and NiZn based ferrite.

7. The coil component according to claim 1 , wherein a content of a residual hardener or a residual binder other than the resin in the first and second cores is 0 wt %.

8. A coil component described in any one of claims 1 to 7, further comprising a void layer between the first and second cores.

9. The coil component according to claim 8 , wherein the void layer is an air gap.

10. The coil component according to claim 8 or 9, wherein the maximum thickness of the void layer is less than 1 μm.

11. 11. The coil component according to claim 1, wherein the joining surface does not contain any adhesive other than a resin formed by dissolving a portion of the resin contained in the first and second cores and then re-hardening the resin.

12. 12. The coil component according to claim 1, wherein the main body includes a first side surface and a second side surface opposing each other in a width direction, a first end surface and a second end surface opposing each other in a length direction, and an upper surface and a lower surface opposing each other in a thickness direction, and the main body is configured in a 5050 size having a width and a length of 5.0 mm and 5.0 mm, respectively.

13. The coil component according to claim 1 , wherein the resin in the first core and the resin in the second core are in direct contact with each other in at least a partial region.

14. The coil component of claim 1 , wherein the bonding surface comprises a cured epoxy.

15. The coil component according to claim 1 , wherein the joining surface is in a strip shape having a predetermined thickness.

Images