Inductors

Abstract

The present disclosure provides an inductor, the inductor comprising a body, the body comprising an internal coil having a first end and a second end, and an encapsulant encapsulating the internal coil and containing magnetic particles. A first external electrode and a second external electrode are located on an outer surface of the body and are electrically connected to the internal coil. A first metal extension surrounds the first end while being in direct contact with the first end of the internal coil and can be located between the body and the first external electrode. A second metal extension surrounds the second end while being in direct contact with the second end of the internal coil and can be located between the body and the second external electrode.

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 17, 2018, application number 201811210084.6, and name “Inductor”. Technical Field

[0002] The present disclosure relates to an inductor, and more particularly, to a power inductor. Background Art

[0003] According to the recent trend of high performance and larger screen size of electronic devices, portable electronic devices such as smart phones require high reliability and miniaturized internal components. The reliability of power inductors can be improved by increasing the breakdown voltage (BDV) by magnetic coating, increasing the body strength of system-in-package (SiP) applications, etc. However, when the power inductor is mounted around the power management integrated circuit (PMIC), the outer electrode may become detached due to stress caused by thermal contraction and expansion, which reduces the reliability of the power inductor. Summary of the invention

[0004] An aspect of the present disclosure may provide an inductor that ensures reliability by increasing contact properties between an internal coil and an external electrode.

[0005] According to one aspect of the present disclosure, an inductor may include: a main body, the main body including an internal coil having a first end and a second end and an encapsulant encapsulating the internal coil and containing magnetic particles; a first external electrode and a second external electrode, which may be located on the outer surface of the main body and electrically connected to the internal coil; a first metal extension, which may surround the first end and be in direct contact with the first end of the internal coil, and the first metal extension may be located between the main body and the first external electrode; a second metal extension, which may surround the second end and be in direct contact with the second end of the internal coil, and the second metal extension may be located between the main body and the second external electrode; and a first connection layer and a second connection layer, each including a plurality of layers, the first connection layer may be between the first metal extension and the first external electrode, and the second connection layer may be between the second metal extension and the second external electrode, and each of the plurality of layers may contain an intermetallic compound.

[0006] According to another aspect of the present disclosure, an inductor may include: a main body, including a coil, the coil having an end exposed at a side surface of the main body, the end having an exposed portion, the exposed portion having a first area; a metal extension portion, located on the side surface, in contact with the exposed portion of the end of the coil, and covering a second area of ​​the side surface, the second area being larger than the first area of ​​the end; a first inner layer, surrounding the metal extension portion and in contact with the metal extension portion, and the first inner layer comprising a first intermetallic compound; a second inner layer, surrounding the first inner layer and in contact with the first inner layer, and the second inner layer comprising a second intermetallic compound; and an outer electrode layer, surrounding the second inner layer and in contact with the second inner layer.

[0007] According to another aspect of the present disclosure, an inductor may include: a main body, including a coil, the coil having an end exposed at a side surface of the main body; an external electrode, located on the side surface of the main body and electrically connected to the end of the coil, wherein the end of the coil is electrically connected to the external electrode through a first layer and a second layer, wherein the first layer has a cross-sectional area wider than a cross-sectional area of ​​the end, and the second layer contains an intermetallic compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above and other aspects, features and advantages of the present disclosure will be more clearly understood through the following detailed description taken in conjunction with the accompanying drawings, in which:

[0009] Figure 1 is a perspective view of an inductor according to an exemplary embodiment of the present disclosure;

[0010] Figure 2 is along Figure 1 A cross-sectional view taken along line II' of ; and

[0011] Figure 3 is based on Figure 1 and Figure 2 A cross-sectional view of an inductor of a modified example of the inductor. DETAILED DESCRIPTION

[0012] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0013] An inductor according to an exemplary embodiment in the present disclosure will be described, but the inductor is not necessarily limited thereto.

[0014] Figure 1 is a perspective view of an inductor 100 according to the present disclosure. Figure 2 is along Figure 1 A cross-sectional view taken along line II'.

[0015] Reference Figure 1 and Figure 2 , the inductor 100 may include a body 1 and first and second external electrodes 21 and 22 located on outer surfaces of the body.

[0016] The body 1 may form the exterior of the inductor. The body 1 may have: an upper surface and a lower surface, which are opposite to each other in the thickness direction (T); a first end surface and a second end surface, which are opposite to each other in the length direction (L); and a first side surface and a second side surface, which are opposite to each other in the width direction (W). The body 1 may have a substantially hexahedral shape.

[0017] The body 1 may include an encapsulant 11 containing magnetic particles. The encapsulant 11 may be formed using a magnetic particle-resin composition in which magnetic particles are dispersed in a resin. For example, the encapsulant 11 may be formed by filling ferrite or a metal-based soft magnetic material. The ferrite may include ferrites known in the art such as Mn-Zn-based ferrites, Ni-Zn-based ferrites, Ni-Zn-Cu-based ferrites, Mn-Mg-based ferrites, Ba-based ferrites, Li-based ferrites, etc. The metal-based soft magnetic material may be an alloy containing at least one selected from the group consisting of Fe, Si, Cr, Al and Ni. For example, the metal-based soft magnetic material may include Fe-Si-B-Cr-based amorphous metal particles, but is not limited thereto. The metal-based soft magnetic material may have a particle size of 0.1 μm or more to 20 μm or less. The ferrite or the metal-based soft magnetic material may be contained in a state where the ferrite or the metal-based soft magnetic material is dispersed in a polymer such as epoxy resin, polyimide, etc., thereby forming the body.

[0018] The internal coil 12 may be embedded in the body by an encapsulant, and may include a first end portion 121 and a second end portion 122 exposed at a first end surface and a second end surface of the body, respectively, so that the internal coil 12 may be connected to an external component. Although the first end portion and the second end portion are shown as being exposed at the first end surface and the second end surface, respectively, the first end portion and the second end portion are not limited thereto.

[0019] The internal coil may have a completely spiral shape. The specific method of forming the internal coil is not limited. For example, the internal coil may be formed on a substrate by a plating method. Alternatively, the internal coil may be formed by winding a pre-prepared metal (e.g., copper) strip or stacking a plurality of magnetic sheets after printing a portion of the internal coil pattern on a plurality of magnetic sheets.

[0020] The inner coil may be insulated from the magnetic material by the insulating coating 123 formed on the exposed surface of the inner coil. The method of forming the insulating coating is not particularly limited, and the material of the insulating coating is not particularly limited as long as it contains a material having insulating properties.

[0021] Figure 2 The structure between the internal coil and the external electrode is shown in more detail. The first metal extension 31 can be located between the first end of the internal coil and the first external electrode. The second metal extension 32 can be located between the second end of the internal coil and the second external electrode. The first metal extension and the second metal extension can be formed using a metal material. The first metal extension and the second metal extension can both include a Cu plating layer.

[0022] Any metal material can be used without limitation as long as it is suitable for strengthening the electrical connectivity between the internal coil and the external electrode and providing excellent conductivity. For example, since the first metal extension and the second metal extension can contain components substantially the same as the components of the internal coil, the first metal extension and the second metal extension can contain Cu. Because the first metal extension and the second metal extension are used to increase the contact area between the internal coil and the external electrode, the contact area between the first metal extension and the first end surface needs to be larger than the area of ​​the portion of the first end of the internal coil exposed at the first end surface. Similarly, the contact area between the second metal extension and the second end surface needs to be larger than the area of ​​the portion of the second end of the internal coil exposed at the second end surface. The first metal extension can be formed to surround the portion of the first end exposed at the first end surface, and the second metal extension can be formed to surround the portion of the second end exposed at the second end surface. In addition, the first metal extension can extend from the lower end of the first end surface of the main body to the upper end of the first end surface, and the second metal extension can extend from the lower end of the second end surface of the main body to the upper end of the second end surface.

[0023] According to the trend of the inductor toward size reduction, the thickness of the first metal extension and the second metal extension may be in the range of 1 μm to 20 μm. When the thickness is less than 1 μm, it is technically difficult to maintain the shapes of the exposed portion surrounding the first end and the exposed portion of the second end to a uniform thickness. When the thickness is greater than 20 μm, the thickness of the outer electrode needs to be excessively reduced to maintain the overall size of the inductor.

[0024] The first metal extension 31 and the second metal extension 32 may be surrounded by the first external electrode 21 and the second external electrode 22, respectively. The first connection layer 41 may be between the first metal extension and the first external electrode and may contact the upper and lower surfaces (thickness surfaces) of the body, and the second connection layer 42 may be between the second metal extension and the second external electrode and may contact the thickness surface of the body. In addition, the external electrode may also contact the thickness surface of the body. The first connection layer and the second connection layer may be an intermetallic compound (IMC) formed by the contact between the first metal extension and the first external electrode and the contact between the second metal extension and the second external electrode, respectively. The intermetallic compound may be formed by the combination of the metal component contained in the first metal extension and the second metal extension and the metal component contained in the layer disposed in the innermost part of the first external electrode and the second external electrode. The intermetallic compound may be a Cu-Sn intermetallic compound. The Cu component may be derived from the copper component in the first metal extension and the second metal extension, and the Sn component may be derived from the tin component contained in the layer formed in the innermost part of the first external electrode and the second external electrode. More specifically, the tin component contained in the first external electrode and the second external electrode can be derived from an Ag-Sn based solder-epoxy resin compound (also referred to as an Ag-Sn based solder-epoxy resin paste) applied when using a paste containing an Ag-epoxy resin to form a layer formed in the innermost part of the first external electrode and the second external electrode. The Sn component may remain according to the ratio between the number of moles of Sn based solder added to the Ag-Sn based solder-epoxy resin compound and the number of moles of Ag particles added to the Ag-Sn based solder-epoxy resin compound. Since the remaining Sn component and the copper component in the first metal extension and the second metal extension form an intermetallic compound again, the first connecting layer and the second connecting layer can be formed. In the Ag-Sn based solder-epoxy resin compound, the Sn based solder can be utilized by Sn, Sn 96.5 Ag 3.0 Cu 0.5 Sn 42 Bi 58 Sn 72 Bi 28 The weight ratio of the conductive particles having a high melting point in the paste, Ag particles, and solder particles may be, for example, 55:45 or higher to 70:30 or lower. When the weight ratio is within the above ratio, a stable connection layer may be formed inside the innermost part of the outer electrode, respectively.

[0025] Figure 2The enlarged view of part A shows the structure of the first connection layer and the second connection layer. Each of the first connection layer 41 and the second connection layer 42 may be divided into at least two layers, and the at least two layers may be in contact with the thickness surface of the body. The inner layers 411 and 421 of the first connection layer and the second connection layer, respectively, which are close to the first metal extension and the second metal extension, may be formed using a Cu6Sn5 alloy. The outer layers 412 and 422 of the first connection layer and the second connection layer, respectively, which are close to the first external electrode and the second external electrode, may be formed using a Cu3Sn alloy. Although the inner and outer layers are Figure 2 It is shown as being continuously formed along the entire first end surface and the second end surface of the body, but when the molar ratio between the Ag component and the Sn component in the Ag-Sn based solder-epoxy resin compound in the first external electrode and the second external electrode is controlled, at least one of the inner layer and the outer layer can be formed as a discontinuous layer.

[0026] The first connection layer and the second connection layer may be surrounded by the first external electrode and the second external electrode, respectively. More specifically, the first connection layer and the second connection layer may have a structure in which the first connection layer and the second connection layer are respectively surrounded by the first layer 211 and 221 disposed in the innermost part of the first external electrode 21 and the second external electrode 22. Since the first connection layer 41 is between the first layer 211 and the first metal extension, and the second connection layer 42 is between the first layer 221 and the second metal extension, the first layers 211 and 221 may be layers formed using Ag-Sn-based solder-epoxy paste. The first layers 211 and 221 may include epoxy resin. Epoxy resin is a thermosetting resin, and those skilled in the art may select another thermosetting resin instead of epoxy resin to change the composition of the first layer without limitation. The structure of the first layer may include a conductive frame and a cured resin filled in the conductive frame. The conductive frame may include an Ag-Sn-based alloy. For example, the Ag-Sn-based alloy constituting the conductive frame may be Ag3Sn. The conductive frame may have a structure in which Ag particles or solder particles having Sn contents different from each other are irregularly dispersed.

[0027] Since the first layer includes the conductive frame having the continuously connected mesh structure, the overall mechanical strength of the outer electrode may be increased, and the DC resistance (Rdc) of the inductor may be reduced.

[0028] The first and second external electrodes 21 and 22 may further include second layers 212 and 222 respectively on the first layers 211 and 221 disposed in the innermost portions of the first and second external electrodes 21 and 22. Preferably, the second layer may be a Ni plating layer. The first and second external electrodes 21 and 22 may further include plating layers including Sn as third layers 213 and 223 respectively on the second layer to improve welding characteristics when the inductor is mounted on an external board.

[0029] Table 1 below shows tensile strength results of the outer electrodes obtained by measuring a force required to separate the outer electrodes while pulling them outward after pins were welded to both ends of the outer electrodes of the inductor.

[0030] The inductor of Inventive Example 1 includes a metal extension according to the present disclosure, a connection layer, and an outer electrode having an innermost layer including a conductive frame filled with resin. The inductor of Inventive Example 1 contains about 60 wt% of Ag in the Ag-epoxy resin in its outer electrode, and contains copper, tin, and various resin materials (such as epoxy bisphenol A resin, polyvinyl butyral), etc. in addition to Ag. The size of the inductor is 1.4 mm×2.0 mm×1.0 mm (width×length×thickness), and the series inductance (Ls) is 0.47 μH.

[0031] In contrast, the inductor of Comparative Example 1 is different from the inductor of Inventive Example 1 in that the end of the inner coil is in direct contact with the outer electrode, and each outer electrode sequentially includes a plating layer containing Ni and a plating layer containing Sn from its innermost portion. The inductor of Comparative Example 2 is different from the inductor of Comparative Example 1 in that a metal-resin paste of Ag-epoxy resin is applied before forming the plating layer containing Ni.

[0032] [Table 1]

[0033]

[0034] As shown in Table 1, in the inductor of Inventive Example 1, the tensile strength of the outer electrode is nearly twice that of the inductor of Comparative Example 1. The inductor of Inventive Example 1 has improved tensile strength due not only to the first metal extension between the first end of the inner coil and the first outer electrode and the second metal extension between the second end and the second outer electrode, but also to the first and second connection layers connected thereto, the skeleton structure of the conductive frame formed using the IMC compound in the first layer in the innermost portions of the first and second outer electrodes, and the cured resin filled in the skeleton structure.

[0035] Figure 3 is a cross-sectional view of an inductor 200 in which an insulating layer 5 for insulating the body is also added to Figure 1and Figure 2 The inductor is 100. Figure 3 The inductor consists of Figure 1 and Figure 2 The inductor 200 has substantially the same configuration as that of the inductor 100 and further includes an insulating layer 5. For example, the inductor 200 may include first and second metal extensions 531 and 532, first and second connection layers 541 and 542, and first and second external electrodes 521 and 522, and the description of the structures and positional relationships of the above components may be the same as the description of the corresponding components in the inductor 100. Therefore, for the convenience of explanation, the description of repeated aspects is omitted.

[0036] Reference Figure 3 , the insulating layer 5 may be located on the upper and lower surfaces of the main body to prevent the plating diffusion of the first metal extension and the second metal extension located on the first end surface and the second end surface of the main body. In addition, the insulating layer 5 may also be located on the first side surface and the second side surface of the main body. The insulating layer 5 may include a material with insulating properties (e.g., polyimide, polyparaxylene, epoxy resin, etc.). Figure 3 As shown in , the first metal extension and the second metal extension do not need to extend above the upper surface of the insulating layer. However, whether the first metal extension and the second metal extension extend above the upper surface of the insulating layer is irrelevant as long as the extension is performed within the error range of the overall size of the inductor.

[0037] As set forth above, according to exemplary embodiments in the present disclosure, an inductor may be provided in which the tensile strength between the internal coil and the external electrode is enhanced and the Rdc characteristics of the inductor are improved by improving the contact property between the internal coil and the external electrode.

[0038] While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. An inductor, comprising: a body including an inner coil having a first end and a second end and an encapsulant encapsulating the inner coil and containing magnetic particles; A first outer electrode and a second outer electrode are located on an outer surface of the body and connected to the internal coil, a first metal extension portion, located between the main body and the first external electrode and in direct contact with the first end portion; a second metal extension portion, located between the main body and the second external electrode and in direct contact with the second end portion; as well as a first connection layer and a second connection layer, each comprising a plurality of layers, the first connection layer being located between the first metal extension and the first external electrode, and the second connection layer being located between the second metal extension and the second external electrode, each of the plurality of layers comprising a Cu-Sn intermetallic compound, wherein each of the first and second external electrodes includes a plurality of layers, and a first layer located at an innermost portion of the plurality of layers of each of the first and second external electrodes includes a conductive frame including an intermetallic compound of an Ag-Sn based alloy.

2. The inductor according to claim 1, wherein The first metal extension surrounds an exposed surface of the first end portion exposed at the outer surface of the body, and the second metal extension surrounds an exposed surface of the second end portion exposed at the outer surface of the body.

3. The inductor according to claim 1, wherein: The first connecting layer and the second connecting layer are both double layers.

4. The inductor according to claim 3, wherein: The first connection layer includes an inner layer close to the first metal extension and an outer layer close to the first external electrode, and the second connection layer includes an inner layer close to the second metal extension and an outer layer close to the second external electrode.

5. The inductor according to claim 4, wherein: The inner layer comprises a Cu6Sn5 alloy.

6. The inductor according to claim 4, wherein: The outer layer comprises a Cu3Sn alloy.

7. The inductor according to claim 1, wherein: The conductive frame has a structure in which Ag particles or solder particles containing Sn are dispersed in the conductive frame.

8. The inductor according to claim 1, wherein The first external electrode further includes a Sn plating layer located at an outermost portion of the first external electrode, and the second external electrode further includes a Sn plating layer located at an outermost portion of the second external electrode.

9. The inductor according to claim 1, wherein: The first external electrode and the second external electrode each further include a Ni plating layer.

10. The inductor according to claim 1, wherein The first metal extension and the second metal extension both include a Cu plating layer.

11. The inductor according to claim 1, wherein The first metal extension portion and the second metal extension portion completely cover corresponding outer surfaces of the main body, and the first end portion and the second end portion are exposed to corresponding outer surfaces of the main body.

12. The inductor according to claim 1, wherein The first metal extension and the second metal extension each have an average thickness of 1 μm to 20 μm.

13. The inductor according to claim 1, wherein An insulating layer is located on at least a portion of the outer surface of the body other than the outer surface.

14. An inductor, comprising: a body including a coil having an end portion exposed at a side surface of the body, the end portion having an exposed portion, the exposed portion having a first area; a metal extension located on the side surface, in contact with the exposed portion of the end of the coil, and covering a second area of ​​the side surface, the second area being larger than the first area of ​​the end; a first inner layer surrounding the metal extension and contacting the metal extension, and the first inner layer comprises a first Cu-Sn intermetallic compound; a second inner layer surrounding the first inner layer and contacting the first inner layer, wherein the second inner layer comprises a second Cu—Sn intermetallic compound; as well as an outer electrode layer surrounding the second inner layer and contacting the second inner layer, wherein the outer electrode layer comprises a first layer, the first layer contacts the second inner layer and comprises a conductive frame and a curing resin in the conductive frame, Wherein, the conductive frame comprises an intermetallic compound of an Ag-Sn based alloy.

15. The inductor according to claim 14, wherein Each of the first inner layer, the second inner layer, and the outer electrode layer contacts a thickness surface of the body connected to the side surface.

16. The inductor according to claim 14, wherein The metal expansion portion extends from a lower end of the side surface to an upper end of the side surface.

17. The inductor according to claim 14, wherein: The metal extension comprises Cu; The first inner layer comprises a Cu6Sn5 alloy; The second inner layer includes a Cu3Sn alloy.

18. An inductor comprising: a main body including a coil having an end portion exposed at a side surface of the main body; as well as an outer electrode, located on the side surface of the body and connected to the end of the coil, wherein the end of the coil is connected to the external electrode through a first layer and a second layer, wherein the first layer has a cross-sectional area wider than a cross-sectional area of ​​the end, the second layer includes a plurality of layers, and each of the plurality of layers contains a Cu-Sn intermetallic compound, wherein the outer electrode comprises an inner layer, the inner layer comprises a conductive frame and a curing resin located in the conductive frame, Wherein, the conductive frame comprises an intermetallic compound of an Ag-Sn based alloy.

19. The inductor according to claim 18, wherein The connection of the end of the coil to the external electrode through the intermetallic compound of the second layer includes a first connection through a first intermetallic compound and a subsequent second connection through a second intermetallic compound different from the first intermetallic compound.

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