Inductor

Abstract

This provides an improved inductor that is compact and capable of handling high currents. [Solution] The inductor comprises a magnetic core 11 and coil elements 12 embedded in the magnetic core 11. The magnetic core 11 has a bottom surface 11a, a top surface 11b, a first side surface 11c connecting the bottom surface 11a and the top surface 11b, and a second side surface 11d facing the first side surface 11c. The coil elements 12 are made up of N flat plate coils, an odd number of 3 or more, stacked in order. The ends of each coil element 12 constitute an external electrode 13. The external electrodes 13 connected to some of the coil elements 12, which are made up of odd-numbered flat plate coils, are provided by bending their ends toward the first side surface 11c. The external electrodes 13 connected to other coil elements 12, which are made up of even-numbered flat plate coils, are provided by bending their ends toward the second side surface 11d.

Description

Technical Field

[0001] The present invention relates to an inductor used in a power supply circuit or the like.

Background Art

[0002] In recent years, large-scale integrated circuits such as CPUs have been operating at lower voltages, and the required current for the elements has reached several tens of amperes. At the same time, there is a demand for a small and low-profile power supply circuit. To cope with the large current, a multi-phase power supply system has been mainly used. Therefore, a coupling system has been used as a power supply system corresponding to this system. The inductor used in this coupling system is driven by an inductor in which a plurality of coils are coupled with a coupling coefficient of about 0.6.

[0003] Note that, as prior art document information related to the invention of this application, for example, Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in terms of realizing an inductor corresponding to an even larger current, there is room for improvement in conventional coupled inductors and the like.

[0006] An object of the present invention is to provide an inductor with further improvement in that it can be made small and can handle a large current.

Means for Solving the Problems

[0007] To solve the above problems, an inductor according to one aspect of the present invention comprises a rectangular parallelepiped-shaped magnetic core formed by mixing magnetic material powder and a binder and press-molding it, and a coil element embedded in the magnetic core, wherein the magnetic core has a bottom surface, a top surface opposite the bottom surface, a first side surface connecting the bottom surface and the top surface, and a second side surface opposite the first side surface, the coil element consists of N flat plate coils, which are an odd number of 3 or more, and the N flat plate coils are stacked in order from the first side surface toward the second side surface, and the ends of the coil elements are each on the bottom surface External electrodes are formed by protruding from and bending along the bottom surface. The external electrodes connected to some of the coil elements, which are odd-numbered flat plate coils from the first side of the N flat plate coils, are provided by bending the ends of the some coil elements toward the first side. The external electrodes connected to other coil elements, which are even-numbered flat plate coils from the first side of the N flat plate coils, are provided by bending the ends of the other coil elements toward the second side. [Effects of the Invention]

[0008] The above configuration provides an improved inductor that is compact and capable of handling high currents. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of an inductor in one embodiment of the present invention. [Figure 2] This is an external view of an inductor in one embodiment of the present invention. [Figure 3] This is a plan view of a coil element in one embodiment of the present invention. [Figure 4] This figure illustrates an example of the use of an inductor in one embodiment of the present invention. [Figure 5] This is a bottom view of another inductor according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] (Background to the present invention) In recent years, large-scale integrated circuits such as CPUs have been driven by lower voltages, and the current required for the components has reached tens of amperes, creating a demand for small, low-profile power supply circuits. To cope with the increased current, multi-phase power supply systems have been the mainstream. Therefore, coupling power supply systems have been used to support this system. The inductors used in this coupling system are driven by inductors that are coupled with multiple coils with a coupling coefficient of about 0.6.

[0011] However, as the demand for even higher currents increased, the conventional coupling method proved insufficient. In response, a method called a multiphase voltage regulator is being considered. This method requires a significantly larger coupling between multiple coils, and the inductors used in conventional coupling methods could not achieve sufficient characteristics. Increasing the coupling coefficient necessitates a larger opposing area between multiple coils, making it difficult to extract electrodes as in conventional coupled inductors.

[0012] Therefore, the present inventors have provided a magnetic core comprising a rectangular parallelepiped formed by mixing magnetic material powder and a binder and press-molding, and coil elements embedded in the magnetic core, wherein the magnetic core has a bottom surface, a top surface opposite the bottom surface, a first side surface connecting the bottom surface and the top surface, and a second side surface opposite the first side surface, and the coil elements consist of at least four flat coils, which are stacked in order from the first side surface toward the second side surface as a first coil element, a second coil element, a third coil element, and a fourth coil element, and the ends of the coil elements each protrude from the bottom surface and are bent along the bottom surface to form external electrodes, and the first coil element An inductor has been devised in which the external electrode connected to the child is designated as the first external electrode, the external electrode connected to the second coil element as the second external electrode, the external electrode connected to the third coil element as the third external electrode, and the external electrode connected to the fourth coil element as the fourth external electrode. The ends of the first coil element and the end of the third coil element are bent toward the first side surface to provide the first and third external electrodes, respectively, and the ends of the second coil element and the end of the fourth coil element are bent toward the second side surface to provide the second and fourth external electrodes, respectively.

[0013] The above inductor can achieve an inductance of approximately 120 nH for each component (combined inductance of the first and third coil elements, and combined inductance of the second and fourth coil elements), a DC resistance of approximately 0.5 mΩ for each component, and a coupling coefficient of approximately 0.98. In this way, by combining multiple primary coils and multiple secondary coils, it is possible to obtain a compact inductor that can handle high currents and has a large coupling coefficient.

[0014] On the other hand, the inductors mentioned above, as well as the conventional inductors described in the background technology section, have room for improvement in terms of realizing inductors that can handle high currents. Specifically, the DC resistance of the primary coil connected to the power line needs to be further reduced. If the DC resistance of the primary coil can be reduced, the upper limit of the current value can be further increased. In other words, by reducing the DC resistance of the primary coil, a more improved inductor that can handle high currents can be realized. In this invention, an inductor is constructed by stacking multiple flat plate coils and making the number of such coils N an odd number, so that the number of flat plate coils used as the primary coil is one more than the number of flat plate coils used as the secondary coil. As a result, the DC resistance of the primary coil can always be kept lower than that of the secondary coil, so that an inductor with a large coupling coefficient can be obtained and a more improved inductor that can handle high currents can be realized by stacking multiple flat plate coils.

[0015] The embodiments described below are all specific examples of the present invention. The numerical values, shapes, materials, components, arrangement positions of components, connection configurations, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, those components not described in an independent claim are described as optional components.

[0016] Furthermore, in this specification, terms indicating relationships between elements, such as parallelism, and terms indicating the shape of elements, such as rectangular parallelepipeds, as well as numerical ranges, do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0017] Furthermore, each figure is a schematic diagram that has been appropriately emphasized, omitted, or had its proportions adjusted to illustrate the present invention, and is not necessarily a strictly accurate representation; it may differ from the actual shape, positional relationships, and proportions. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations may be omitted or simplified.

[0018] In addition, in this specification, the terms "top surface" and "bottom surface" in the configuration of the inductor do not refer to the top surface (the surface on the vertically upper side) and the bottom surface (the surface on the vertically lower side) in the absolute spatial recognition, but are used as terms defined by the relative positional relationship of the components of the inductor.

[0019] In the embodiments described below, an example in which the number N of flat plate coils to be stacked is 3 is used for explanation, but the number N may be more than 3. If the number N is 3 or more, an inductor with a large coupling coefficient can be obtained by a configuration in which a plurality of flat plate coils are stacked, and by using the remaining one after dividing N by 2 for the primary coil, the DC resistance of the primary coil can always be kept lower than that of the secondary coil, and a more improved inductor corresponding to a large current can be realized. Thus, as long as N is an odd number of 3 or more, its value is not particularly limited.

[0020] (Embodiment) Hereinafter, an inductor according to an embodiment of the present invention will be described with reference to the drawings.

[0021] FIG. 1 is a perspective view of an inductor according to an embodiment of the present invention as viewed from the bottom surface side. FIG. 2 is an external view of the inductor according to an embodiment of the present invention. (a) of FIG. 2 shows an external view of the side surface side of the inductor according to an embodiment of the present invention, (b) of FIG. 2 shows an external view of the bottom surface side thereof, and (c) of FIG. 2 shows an external view of the end surface side thereof. In FIG. 2, the internal coil element is shown by a broken line.

[0022] An inductor in one embodiment of the present invention consists of a rectangular parallelepiped-shaped magnetic core 11 formed by mixing a magnetic material powder consisting of Fe-Si-Cr powder and a binder consisting of silicone and press-molding it, and a coil element 12 embedded in the magnetic core 11. The external shape of the magnetic core 11 is, for example, a rectangular parallelepiped with a width of about 6 mm, a length of about 13 mm, and a height of about 5 mm, and has a bottom surface 11a from which the end of the coil element 12 protrudes, a top surface 11b opposite to the bottom surface 11a, a first side surface 11c connecting the bottom surface 11a and the top surface 11b, a second side surface 11d opposite to the first side surface 11c, a first end surface 11e connecting the first side surface 11c and the second side surface 11d, and a second end surface 11f opposite to the first end surface 11e.

[0023] Three flat coil elements 12 are embedded inside the magnetic core 11. The first coil element 12a, the second coil element 12b, and the third coil element 12c are embedded in a stacked arrangement, facing each other in the planar direction, from the first side surface 11c to the second side surface 11d of the magnetic core 11. The ends of each coil protrude from the bottom surface 11a of the magnetic core 11 and are bent along the bottom surface 11a to form the external electrode 13. Each coil element 12 is formed by punching out a copper plate, for example, with a thickness of approximately 0.4 mm and a coil pattern width of approximately 0.8 mm. Furthermore, the surface of the coil element 12 embedded in the magnetic core 11 is provided with an insulating layer made of epoxy resin, phenolic resin, acrylic resin, etc., with a thickness of approximately 0.03 mm, by pad printing or the like.

[0024] Here, the external electrode connected to the first coil element 12a is referred to as the first external electrode 13a, the external electrode connected to the second coil element 12b is referred to as the second external electrode 13b, and the external electrode connected to the third coil element 12c is referred to as the third external electrode 13c. The ends of the first coil element 12a and the third coil element 12c are bent toward the first side surface 11c to form the first external electrode 13a and the third external electrode 13c, respectively, and the end of the second coil element 12b is bent toward the second side surface 11d to form the second external electrode 13b. Furthermore, each of the first external electrode 13a, the second external electrode 13b, and the third external electrode 13c is extended toward the first end face 11e or the second end face 11f, and its tip portion is bent along the first end face 11e or the second end face 11f. By bending the ends of the coil element to protrude from the bottom surface in this way, an inductor with a small mounting area can be obtained.

[0025] Furthermore, the bottom surface 11a of the magnetic core 11 includes a portion from which the coil element 12 protrudes, and a recess 15 with a depth of approximately 0.4 mm is provided in the region connecting the first side surface 11c and the second side surface 11d. If the end of the coil element 12 is made to protrude from the bottom surface 11a and bent along the bottom surface 11a, a bulge will inevitably occur at the bent portion, resulting in poor stability when mounted. Therefore, as in this embodiment, by making the end of the coil element 12 protrude from the recess 15 provided on the bottom surface 11a of the magnetic core 11, the flatness of the mounting surface of this inductor can be improved. The depth of the recess 15 is preferably 80% or more and 200% or less of the thickness of the external electrode 13. If the depth of the recess 15 is shallower than 80% of the thickness of the external electrode, the flatness will be poor. Conversely, if it exceeds 200%, the core volume will be small and the inductance value will decrease, which is undesirable.

[0026] The inductor is configured as described above, and the first external electrode 13a and the third external electrode 13c adjacent to each other on the mounting board are connected to form the first inductor (i.e., a partial inductor composed of a part of the inductor of the embodiment), and the adjacent second external electrode 13b is used to form the second inductor (i.e., another partial inductor composed of another part of the inductor of the embodiment). In this way, the second coil element 12b is sandwiched between the first coil element 12a and the third coil element 12c. Furthermore, since the coil elements overlap with at least one other coil element across all regions embedded in the magnetic core 11, an inductor with a high coupling coefficient can be obtained between the first inductor and the second inductor. In other words, when the multiple coil elements 12 are counted in order from the first side surface 11c or the second side surface 11d, the external electrodes of the odd-numbered coil elements are all connected to form the first inductor, and the external electrodes of the even-numbered coil elements are all connected to form the second inductor. Since the coil element 12 consists of an odd number of flat coils, the total number of odd-numbered coil elements is necessarily one more than the total number of even-numbered coil elements.

[0027] The coil element 12 will now be described in more detail. Figure 3 is a plan view of a coil element in one embodiment of the present invention. Figure 3(a) shows a plan view of the first coil element, Figure 3(b) shows a plan view of the second coil element, and Figure 3(c) shows a plan view of the third coil element. In Figure 3, the outer shape of the magnetic core 11 when these coil elements are embedded in the magnetic core 11 is shown by dashed lines. The ends of the coil elements that protrude outside the dashed lines are bent along the bottom surface after embedding to form external electrodes. Also in Figure 3, the boundaries between the first to seventh parts are shown by dashed lines to make them easier to understand.

[0028] Each coil element 12, within the magnetic core 11, comprises a first portion 12e extending from the bottom surface 11a toward the top surface 11b, a second portion 12f connected to the top surface 11b end of the first portion 12e and extending toward the first end surface 11e, a third portion 12g connected to the top surface 11b end and first end surface 11e end of the second portion 12f and extending toward the top surface 11b, and the top surface 11b end of the third portion 12g It has a fourth portion 12h extending toward the second end face 11f, a fifth portion 12i connected to the bottom surface 11a side of the fourth portion 12h and the end toward the second end face 11f, a sixth portion 12j connected to the bottom surface 11a side of the fifth portion 12i and extending toward the first end face 11e, and a seventh portion 12k connected to the bottom surface 11a side of the sixth portion 12j and the end toward the first end face 11e, and extending toward the bottom surface 11a.

[0029] The ends of each coil element 12 on the bottom surface 11a side protrude from the ends of the first portion 12e and the seventh portion 12k, respectively, onto the bottom surface 11a of the magnetic core 11, and are bent along the bottom surface 11a of the magnetic core 11 to form their respective external electrodes 13.

[0030] The lengths of the second portion 12f and the sixth portion 12j of the first coil element 12a and the second coil element 12b (L1 in Figure 3(a)) are formed to be longer than the width of the coil pattern compared to the lengths of the second portion 12f and the sixth portion 12j of the third coil element 12c (L2 in Figure 3(c)).

[0031] Furthermore, the first coil element 12a and the second coil element 12b overlap in all paths embedded in the magnetic core 11. In addition, in the third section 12g to the fifth section 12i, the first coil element 12a, the second coil element 12b, and the third coil element 12c all overlap. By doing so, a large coupling coefficient can be obtained between the first inductor and the second inductor.

[0032] Furthermore, the third coil element may be formed by extending the third and fifth portions to the bottom surface without forming the first, second, sixth, and seventh portions. However, it is preferable that at least a portion of the second and sixth portions of each coil element overlap, as this increases the coupling coefficient between the multiple coils. Also, although the coil loop is rectangular in Figure 3, it may also be rounded into an Ω shape.

[0033] With the above configuration, a region is created on the bottom surface 11a where the ends of the second coil element 12b and the ends of the third coil element 12c are in close proximity and facing each other. If the ends of the second coil element 12b and the ends of the third coil element 12c are conductive in this opposing region, a short circuit is likely to occur during mounting. Therefore, it is desirable to provide an insulating layer 14 in the region where the ends of the second coil element 12b and the ends of the third coil element 12c face each other. In Figure 2(b), the area where the insulating layer 14 is provided is shaded for clarity. It is desirable to provide this insulating layer 14 at the same time as forming the insulating layer on the coil element 12 that will be embedded in the magnetic core 11. Doing so simplifies the process.

[0034] Figure 4 is a diagram illustrating an example of the use of an inductor in one embodiment of the present invention. As shown in Figure 4, a multiphase voltage regulator can be configured by connecting two or more inductors. Focusing on one inductor in the multiphase voltage regulator, the first external electrode 13a of the first coil element 12a and the third external electrode 13c of the third coil element 12c (i.e., the external electrodes connected to odd-numbered coil elements) that constitute the first inductor are primary side electrodes connected to the power line between the power source and the load. The second external electrode 13b of the second coil element 12b that constitutes the second inductor (i.e., the external electrode connected to even-numbered coil elements) is a secondary side electrode connected to a coupling line for interlocking each phase. The secondary side coil element 12 connected to the coupling line is also called a coupling coil. By connecting coupling coils between two or more inductors, the phases can be interlocked.

[0035] (Effects, etc.) As described above, the inductor according to the first embodiment comprises a rectangular parallelepiped-shaped magnetic core 11 formed by mixing magnetic material powder and a binder and press-molding it, and a coil element 12 embedded in the magnetic core 11. The magnetic core 11 has a bottom surface 11a, a top surface 11b opposite to the bottom surface 11a, a first side surface 11c connecting the bottom surface 11a and the top surface 11b, and a second side surface 11d opposite to the first side surface 11c. The coil element 12 consists of N flat plate coils, an odd number of 3 or more, arranged in order from the first side surface 11c side toward the second side surface 11d side, and the ends of the coil element 12 are External electrodes 13 are formed by protruding from the bottom surface 11a and being bent along the bottom surface 11a. The external electrodes 13 connected to some of the coil elements 12, which are odd-numbered flat plate coils from the first side surface 11c side out of the N flat plate coils, are provided by bending the ends of some of the coil elements 12 toward the first side surface 11c. The external electrodes 13 connected to other coil elements 12, which are even-numbered flat plate coils from the first side surface 11c side out of the N flat plate coils, are provided by bending the ends of other coil elements 12 toward the second side surface 11d.

[0036] Such an inductor, by stacking multiple flat coils, can be made to have a large coupling coefficient. For example, by using a number of coil elements 12 equal to N divided by 2 for the secondary coil, and using the remaining coil elements 12, including the remainder of the division (1), for the primary coil, the DC resistance of the primary coil can always be kept lower than that of the secondary coil, thereby realizing a more improved inductor that can handle large currents.

[0037] Furthermore, the inductor according to the second embodiment is the inductor described in the first embodiment, wherein the external electrodes 13 connected to some of the coil elements 12 are primary side electrodes connected to the power line, and the external electrodes 13 connected to other parts of the coil elements 12 are secondary side electrodes connected to the coupling line.

[0038] According to this, the above-mentioned inductor can be used as a more improved inductor.

[0039] Furthermore, the inductor according to the third embodiment is the inductor described in the first or second embodiment, wherein an insulating layer 14 is provided on the bottom surface 11a in a region where the ends of some coil elements 12 and the ends of other coil elements 12 face each other.

[0040] According to this, if a region is formed on the bottom surface 11a where the ends of the second coil element 12b and the ends of the third coil element 12c are close together and facing each other, and the ends of the second coil element 12b and the ends of the third coil element 12c are conductive, a short circuit is likely to occur during mounting. Therefore, by providing an insulating layer 14 in the region where the ends of the second coil element 12b and the ends of the third coil element 12c face each other, the possibility of such a short circuit can be reduced. In other words, a highly reliable inductor can be realized by reducing the possibility of a short circuit.

[0041] (Other embodiments, etc.) Although embodiments of the present invention and various modifications relating to inductors, etc. have been described above, the present invention is not limited to the above embodiments and modifications. Without departing from the spirit of the present invention, various modifications that a person skilled in the art can conceive of may be applied to the embodiments and modifications, as well as other forms constructed by combining some of the components of the embodiments and modifications, are also included in the scope of the present invention.

[0042] For example, in Figures 1 and 2, the external electrodes 13 are brought out to the first end face 11e side or the second end face 11f side, but as shown in Figure 5, some of the external electrodes 13 may be brought out to the first side surface 11c side or the second side surface 11d side. By doing so, the degree of freedom of the wiring pattern on the mounting board can be increased and the DC resistance of the wiring pattern can be reduced.

[0043] Furthermore, the present invention also includes, for example, electrical products or circuits that use the inductor described above. Examples of electrical products include power supply devices equipped with the inductor described above, and various devices equipped with said power supply devices. [Industrial applicability]

[0044] The inductor according to the present invention is small, can handle high currents, and can produce an inductor with a large coupling coefficient, making it industrially useful. [Explanation of symbols]

[0045] 11 magnetic core 11a bottom 11b Top surface 11c First aspect 11d Second aspect 11e First end face 11f Second end face 12 coil elements 12a First coil element 12b Second coil element 12c third coil element 12e Part 1 12f Part 2 12g third part 12h Part 4 12i Part 5 12j Part 6 12k part 7 13 external electrodes 13a First external electrode 13b Second external electrode 13c third external electrode 14 insulating layers 15 recesses

Claims

1. A rectangular magnetic core formed by mixing magnetic material powder and a binder and then press-molding it, The magnetic core comprises a coil element embedded in the magnetic core, The magnetic core has a bottom surface, a top surface facing the bottom surface, a first side surface connecting the bottom surface and the top surface, and a second side surface facing the first side surface. The coil element consists of N flat plate coils, which are an odd number of three or more, and the N flat plate coils are arranged in order from the first side to the second side. The ends of the coil element each protrude from the bottom surface and are bent along the bottom surface to form an external electrode. The external electrodes connected to some of the coil elements, which are composed of odd-numbered flat plate coils from the first side of the N flat plate coils, are provided by bending the ends of the some coil elements toward the first side. The external electrode connected to the coil element of the other part, which is composed of an even-numbered flat plate coil from the first side side among the N flat plate coils, is provided by bending the end of the coil element of the other part toward the second side side. Inductor.

2. The external electrodes connected to some of the coil elements are primary side electrodes connected to the power line. The external electrode connected to the coil element in the other part is a secondary electrode connected to the coupling line. The inductor according to claim 1.

3. An insulating layer is provided in the bottom surface in the region where the ends of some of the coil elements and the ends of other coil elements face each other. The inductor according to claim 1 or 2.

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