Inductor and DC-DC converter

Abstract

To provide an inductor and a DC-DC converter capable of suppressing structural defects due to thermal expansion of a magnetic body.SOLUTION: A resin material 5 includes coil conductors 3A and 3B and magnetic bodies 2A, 2B, and 2C. Therefore, when a current flows through the coil conductors 3A and 3B to raise the temperature of an inductor 1, the magnetic bodies 2A, 2B, and 2C thermally expand in a resin material 5. On the other hand, the inductor 1 has a gap 20 between the resin material 5 and one side surface 2Ae, 2Be, 2Ce (a first surface) of at least the magnetic bodies 2A, 2B, 2C. The amount of displacement of the magnetic bodies 2A, 2B, and 2C due to thermal expansion is absorbed by the gap 20. Therefore, it is possible to prevent the resin material 5 from being pressed against the thermally expanded magnetic bodies 2A, 2B, and 2C. As described above, structural defects due to thermal expansion of the magnetic bodies 2A, 2B, and 2C can be suppressed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an inductor and a DC-DC converter. [Background technology]

[0002] A conventional inductor is described in Patent Document 1. This inductor includes a coil conductor and a magnetic body that serves as a core. The inductor also includes a resin material that contains the coil conductor and the magnetic body inside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018-079402 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the temperature of the inductor rises during use. At this time, the magnetic material inside the resin material may thermally expand. If the thermal expansion coefficient of the magnetic material is greater than that of the resin material, the thermally expanded magnetic material may be pressed against the resin material, causing structural defects such as cracks.

[0005] Therefore, an object of the present disclosure is to provide an inductor and a DC-DC converter that can suppress structural defects caused by thermal expansion of magnetic materials. [Means for solving the problem]

[0006] An inductor according to one aspect of the present disclosure comprises a coil conductor, a magnetic body, and a resin material containing the coil conductor and the magnetic body therein, and has a gap between the resin material and at least one first surface of the magnetic body.

[0007] A DC-DC converter according to one aspect of the present disclosure includes the inductor described above. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to provide an inductor and a DC-DC converter that can suppress structural defects caused by thermal expansion of a magnetic material. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view of an inductor according to the present embodiment. [Figure 2] FIG. [Figure 3] 2 is a diagram showing a circuit of a DC-DC converter in which the inductor shown in FIG. 1 is used. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] 4, and FIG. 5(b) is a cross-sectional view taken along line Vb-Vb in FIG. [Figure 6] FIG. 10 is a cross-sectional view showing an inductor according to a modified example. [Figure 7] FIG. 10 is a diagram showing a circuit of a DC-DC converter according to a modified example. [Figure 8] FIG. 10 is a diagram illustrating an inductor according to a modified example. [Figure 9] FIG. 10 is a diagram illustrating an inductor according to a modified example. [Figure 10] FIG. 10 is a diagram illustrating an inductor according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0011] First, a schematic configuration of an inductor 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the inductor 1 according to this embodiment. FIG. 2 is a developed view of the inductor 1. Note that FIG. 1 shows the inductor 1 mounted on a substrate 101. The inductor 1 according to this embodiment is formed by stacking magnetic bodies 2A, 2B, and 2C that form cores and coil conductors 3A and 3B in the X-axis direction. In this embodiment, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to one another. In this embodiment, the X-axis direction corresponds to the "first direction" in the claims, and the Y-axis direction that is perpendicular to the X-axis direction corresponds to the "second direction" in the claims.

[0012] As shown in Fig. 1, inductor 1 includes magnetic body 2A, magnetic body 2B, magnetic body 2C, coil conductor 3A, coil conductor 3B, resin material 5, resin member 6A, resin member 6B, and resin member 6C. To facilitate understanding of the features, resin material 5 is shown by a virtual line in Fig. 1. Inductor 1 can be used as a choke coil in a circuit of DC-DC converter 100 shown in Fig. 3.

[0013] The magnetic bodies 2A and 2B are arranged facing each other at a distance in the X-axis direction. The magnetic bodies 2B and 2C are arranged facing each other at a distance in the X-axis direction. The magnetic bodies 2A, 2B, and 2C are arranged in this order from the positive side in the X-axis direction. The magnetic bodies 2A, 2B, and 2C have rectangular parallelepiped shapes. The magnetic bodies 2A, 2B, and 2C have the same shape. Note that the magnetic bodies 2A, 2B, and 2C may have a shape other than a rectangular parallelepiped. The magnetic bodies 2A, 2B, and 2C may be made of magnetic materials such as sintered cores such as MnZn-based ferrite and NiZn-based ferrite, and laminated cores formed by stacking soft magnetic metal plates. The magnetic permeabilities of the magnetic bodies 2A, 2B, and 2C may be 1000 or more. The magnetic properties of the magnetic bodies 2A, 2B, and 2C may be substantially the same or different.

[0014] The pair of coil conductors 3 (3A and 3B) included in inductor 1 can be used as each choke coil in the circuit of DC-DC converter 500 shown in Fig. 3. DC-DC converter 500 is a multi-phase converter including a pair of conversion units each consisting of switching elements SW1 and SW2, choke coils 520A and 520B, and diodes D1 and D2, connected in parallel, and inductor 1 can be used as choke coils 520A and 520B in each conversion unit. The configuration of DC-DC converter 500 will be described in more detail below. DC-DC converter 500 includes a pair of input terminals A1 and A2, a pair of output terminals B1 and B2, a switching element SW1 and choke coil 520A connected in series between input terminal A1 and output terminal B1, a switching element SW2 and choke coil 520B connected in series between input terminal A1 and output terminal B1, and a capacitor C1 connected between output terminals B1 and B2. A circuit consisting of switching element SW1 and choke coil 520A and a circuit consisting of switching element SW2 and choke coil 520B are connected in parallel between input terminal A1 and output terminal B1. Input terminal A2 and output terminal B2 form a ground line. Diode D2 is connected in reverse between the connection point of switching element SW1 and choke coil 520A and the ground line, and diode D1 is connected in reverse between the connection point of switching element SW2 and choke coil 520B and the ground line. Switching elements SW1 and SW2 are alternately turned on and off by a control circuit (not shown), thereby generating an output voltage that is a step-down of the input voltage. By configuring the pair of choke coils 520A and 520B in DC-DC converter 500 using the pair of coil conductors 3A and 3B of inductor 1, the number of components constituting DC-DC converter 500 can be reduced.

[0015] As shown in FIG. 2, the magnetic body 2A has main surfaces 2Aa and 2Ab, end surfaces 2Ac and 2Ad, and side surfaces 2Ae and 2Af. The main surfaces 2Aa and 2Ab are surfaces that face each other in the X-axis direction. The main surface 2Aa is located on the positive side of the X-axis direction, and the main surface 2Ab is located on the negative side of the X-axis direction. The end surfaces 2Ac and 2Ad are surfaces that face each other in the Y-axis direction. The end surface 2Ac is located on the positive side of the Y-axis direction, and the end surface 2Ad is located on the negative side of the Y-axis direction. The side surfaces 2Ae and 2Af are surfaces that face each other in the Z-axis direction. The side surface 2Ae is located on the positive side of the Z-axis direction, and the side surface 2Af is located on the negative side of the Z-axis direction.

[0016] The magnetic body 2B has main surfaces 2Ba and 2Bb, end surfaces 2Bc and 2Bd, and side surfaces 2Be and 2Bf. The magnetic body 2C has main surfaces 2Ca and 2Cb, end surfaces 2Cc and 2Cd, and side surfaces 2Ce and 2Cf. These surfaces have the same configuration as the main surfaces 2Aa and 2Ab, end surfaces 2Ac and 2Ad, and side surfaces 2Ae and 2Af of the magnetic body 2A.

[0017] The main surface 2Ab of the magnetic body 2A and the main surface 2Ba of the magnetic body 2B are arranged to face each other while being spaced apart in the X-axis direction. The main surface 2Bb of the magnetic body 2B and the main surface 2Ca of the magnetic body 2C are arranged to face each other while being spaced apart in the X-axis direction. As a result, the magnetic body 2A is arranged so that a portion (region 17A) located between conductor portions 11A and 12A (described later) is sandwiched between the magnetic body 2A and the magnetic body 2B in the X-axis direction. The magnetic body 2C is arranged so that a portion (region 17B) located between conductor portions 11B and 12B (described later) is sandwiched between the magnetic body 2B and the magnetic body 2C in the X-axis direction. In this embodiment, the end faces 2Ac and 2Ad, the end faces 2Bc and 2Bd, and the end faces 2Cc and 2Cd are arranged at the same position in the YZ plane so as to overlap each other when viewed from the X-axis direction. Therefore, the magnetic bodies 2A, 2B, and 2C may have the same area when viewed from the X-axis direction. The thicknesses of the magnetic bodies 2A, 2B, and 2C in the X-axis direction may also be the same. That is, the magnetic bodies 2A, 2B, and 2C may be the same size. In this specification, "same position" includes a range of positional deviation caused by manufacturing errors, etc., and "same" and "same size" include a range of error caused by manufacturing variations.

[0018] The coil conductor 3A includes a conductor portion 11A, a conductor portion 12A, a connecting portion 13A, a terminal portion 14A, and a terminal portion 16A. The material of the coil conductor 3A is made of a metal selected from, for example, Cu, Ag, Au, Al, Ni, Sn, and the like.

[0019] The conductor portions 11A and 12A extend in the Z-axis direction and are arranged between the magnetic bodies 2A and 2B in the X-axis direction. The conductor portion 11A is arranged on the positive side in the Y-axis direction, and the conductor portion 12A is arranged on the negative side in the Y-axis direction. The connecting portion 13A is a member that connects the conductor portions 11A and 12A. The connecting portion 13A connects the positive ends of the conductor portions 11A and 12A in the Z-axis direction to each other and extends in the Y-axis direction. The terminal portion 14A is provided at the negative end of the conductor portion 11A in the Z-axis direction and extends to the positive side in the X-axis direction and the positive side in the Y-axis direction. The terminal portion 14A is configured by forming a portion of the conductor portion 11A near the negative end in the Z-axis direction so that it widens toward the positive side in the Y-axis direction and bending the wide portion toward the positive side in the X-axis direction. Terminal portion 16A is provided at the negative end of conductor portion 12A in the Z-axis direction, and extends toward the positive side in the X-axis direction and the negative side in the Y-axis direction. Terminal portion 16A is configured by forming a portion of conductor portion 12A near the negative end of the Z-axis direction so that it widens toward the negative side in the Y-axis direction, and bending this wide portion toward the positive side in the X-axis direction. Terminal portions 14A and 16A are joined to electrode 102 (see FIG. 1) of substrate 101. In this way, inductor 1 is mounted on substrate 101. Note that conductor portions 11A and 12A do not have to be parallel to the Z-axis direction as long as they extend in the Z-axis direction. Furthermore, connecting portion 13A does not have to be parallel to the Y-axis direction as long as it extends in the Y-axis direction.

[0020] The coil conductor 3A has a side surface 3Aa on the positive side in the X-axis direction and a side surface 3Ab on the negative side in the X-axis direction. The side surface 3Aa is formed by arranging the positive side surfaces of the conductor portions 11A and 12A and the connecting portion 13A in the same plane. The terminal portions 14A and 16A protrude toward the positive side in the X-axis direction beyond the side surface 3Aa. The side surface 3Aa faces the main surface 2Ab of the magnetic body 2A in the X-axis direction and is in contact with each other. The side surface 3Ab is formed by arranging the negative side surfaces of the conductor portions 11A and 12A and the connecting portion 13A in the same plane. The side surface 3Ab faces the main surface 2Ba of the magnetic body 2B in the X-axis direction and is in contact with each other. Arranging the magnetic bodies 2A, 2B, and 2C in contact with the coil conductors 3A and 3B stabilizes the positional relationship between the magnetic bodies 2A, 2B, and 2C, especially in the X-axis direction, thereby reducing inductance variations. In this specification, "contact" refers not only to direct contact between the magnetic bodies 2A, 2B and the coil conductor 3A, but also to indirect contact via an insulating layer, adhesive layer, etc. The same applies to contact between the magnetic bodies 2B, 2C and the coil conductor 3B, which will be described later.

[0021] 2, the coil conductor 3B includes a conductor portion 11B, a conductor portion 12B, a connecting portion 13B, a terminal portion 14B, and a terminal portion 16B. The material of the coil conductor 3B may be the same as that of the coil conductor 3A.

[0022] The conductor portions 11B and 12B extend in the Z-axis direction and are arranged between the magnetic body 2B and the magnetic body 2C in the X-axis direction. The conductor portion 11B is arranged on the positive side in the Y-axis direction, and the conductor portion 12B is arranged on the negative side in the Y-axis direction. The connecting portion 13B is a member that connects the conductor portion 11B and the conductor portion 12B. The connecting portion 13B connects the positive ends of the conductor portions 11B and 12B in the Z-axis direction to each other and extends in the Y-axis direction. The terminal portion 14B is provided at the negative end of the conductor portion 11B in the Z-axis direction and extends to the negative side in the X-axis direction and the positive side in the Y-axis direction. The terminal portion 14B is configured by forming a portion of the conductor portion 11B near the negative end in the Z-axis direction so that it widens toward the positive side in the Y-axis direction and bending the wide portion toward the negative side in the X-axis direction. Terminal portion 16B is provided at the negative end of conductor portion 12B in the Z-axis direction and extends toward the negative side in the X-axis direction and the negative side in the Y-axis direction. Terminal portion 16B is configured by forming a portion of conductor portion 12B near the negative end in the Z-axis direction so that it widens toward the negative side in the Y-axis direction and bending the wide portion toward the negative side in the X-axis direction. Terminal portions 14B and 16B are joined to electrode 102 (see FIG. 1) of substrate 101. In this way, inductor 1 is mounted on substrate 101. Note that conductor portions 11B and 12B do not have to be parallel to the Z-axis direction as long as they extend in the Z-axis direction. Furthermore, connecting portion 13B does not have to be parallel to the Y-axis direction as long as it extends in the Y-axis direction.

[0023] The coil conductor 3B has a side surface 3Ba on the positive side in the X-axis direction and a side surface 3Bb on the negative side in the X-axis direction. The side surface 3Ba is formed by arranging the positive side surfaces of the conductor portions 11B and 12B and the connecting portion 13B on the same plane. The side surface 3Ba faces the main surface 2Bb of the magnetic body 2B in the X-axis direction and is in contact with them. The side surface 3Bb is formed by arranging the negative side surfaces of the conductor portions 11B and 12B and the connecting portion 13B on the same plane. The terminal portions 14B and 16B protrude further toward the negative side in the X-axis direction than the side surface 3Bb. The side surface 3Bb faces the main surface 2Ca of the magnetic body 2C in the X-axis direction and is in contact with them.

[0024] Coil conductors 3A and 3B have a plane-symmetrical structure with respect to the ZY plane. Therefore, they are formed with the same shape so that they overlap when viewed from the X-axis direction. Note that "plane-symmetrical" includes a range of misalignment caused by manufacturing errors, etc., and "same shape" includes a range of error caused by manufacturing variations.

[0025] The resin member 6A is arranged to cover the negative side surface 2Af of the magnetic body 2A in the Z-axis direction. The resin member 6B is arranged to cover the negative side surface 2Bf of the magnetic body 2B in the Z-axis direction. The resin member 6C is arranged to cover the negative side surface 2Cf of the magnetic body 2C in the Z-axis direction. The resin members 6A, 6B, and 6C are sheet-like members that cover substantially the entire surfaces of the side surfaces 2Af, 2Bf, and 2Cf. The material of the resin members 6A, 6B, and 6C is not particularly limited, and polyimide, polyamideimide, fluororesin, and the like may be used. For example, Kapton (registered trademark) tape may be used as the resin members 6A, 6B, and 6C.

[0026] The negative side surfaces 2Af, 2Cf (surfaces on the other side) of the magnetic bodies 2A, 2C in the Z-axis direction are placed on the upper surfaces 14a, 16a of the terminal portions 14A, 16A, 14B, 16B via the resin members 6A, 6C. As a result, the resin member 6A is disposed between the magnetic body 2A and the terminal portions 14A, 16A. The resin member 6C is disposed between the magnetic body 2C and the terminal portions 14B, 16B. In this embodiment, the negative side surface 2Bf of the magnetic body 2B in the Z-axis direction is disposed at the same height as the negative side surfaces 2Af, 2Cf of the other magnetic bodies 2A, 2C in the Z-axis direction. Note that "the same height" includes a range of error caused by manufacturing variations.

[0027] Next, the resin material 5 will be described. The resin material 5 covers the assembly of the magnetic bodies 2A, 2B, and 2C and the coil conductors 3A and 3B. Thus, the resin material 5 contains the coil conductors 3A and 3B and the magnetic bodies 2A, 2B, and 2C. The resin material 5 exposes at least the lower surfaces of the terminal portions 14A, 16A, 14B, and 16B. Therefore, the resin material 5 covers at least the positive side surfaces 2Ae, 2Be, and 2C in the Z-axis direction of the magnetic bodies 2A, 2B, and 2C. The resin material 5 may contain magnetic powder. Specifically, a thermosetting resin such as epoxy is used as the material for the resin material 5. When the resin material 5 contains magnetic powder, a mixture of soft magnetic metal powder and resin may be used. Examples of the soft magnetic metal powder include iron-silicon alloys, permalloys, sendust, amorphous alloys, nanocrystalline alloys, and mixtures thereof. Furthermore, when the resin material 5 contains magnetic powder, the magnetic permeability of the resin material 5 may be 5 or more, and may be 20 or more. Furthermore, the magnetic permeability of the resin material 5 may be 100 or less, and may be 50 or less. The resin material 5 may have a lower magnetic permeability than the magnetic bodies 2A, 2B, and 2C. The resin material 5 is disposed within the regions 17A and 17B. That is, the resin material 5 is formed so as to cover the inner portions 11Aa, 11Ba, 12Aa, 12Ba, 13Aa, and 13Ba.

[0028] Next, with reference to FIG. 4, the cross-sectional shape of the inductor 1 will be described. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1. As shown in FIG. 4, the inductor 1 has a gap 20 between the resin material 5 and at least one side surface 2Ae, 2Be, 2Ce (first surface) of each of the magnetic bodies 2A, 2B, 2C. The magnetic bodies 2A, 2B, 2C have a laminated structure of magnetic ribbons 30 and adhesive resin 31 (see FIG. 5). The lamination direction of the laminated structure is the Z-axis direction. The side surfaces 2Ae, 2Be, 2Ce that form the gap 20 are the outermost surfaces in the lamination direction (Z-axis direction) of the laminated structure. The side surfaces 2Ae, 2Be, 2Ce are surfaces that intersect with the lamination direction. The side surfaces 2Ae, 2Be, 2Ce are approximately perpendicular to the lamination direction. "Approximately perpendicular" means that the side surfaces 2Ae, 2Be, 2Ce are allowed to bend, as will be described later.

[0029] The magnetic bodies 2A, 2B, and 2C have side surfaces 2Af, 2Bf, and 2Cf (second surfaces) that are outermost surfaces on the opposite side of the stacking direction (Z-axis direction) from the side surfaces 2Ae, 2Be, and 2Ce. The side surfaces 2Af, 2Bf, and 2Cf are surfaces that intersect with the stacking direction (Z-axis direction) in the stacked structure. The side surfaces 2Af, 2Bf, and 2Cf are approximately perpendicular to the stacking direction. The aforementioned resin members 6A, 6B, and 6C are arranged at positions facing the side surfaces 2Af, 2Bf, and 2Cf. The resin members 6A, 6B, and 6C are interposed between the resin material 5 and the side surfaces 2Af, 2Bf, and 2Cf. The resin members 6A, 6B, and 6C are in contact with the side surfaces 2Af, 2Bf, and 2Cf without any gaps. The resin members 6A, 6B, and 6C may be omitted. In this case, the inductor 1 may have gaps 20 between the resin material 5 and the side surfaces 2Af, 2Bf, and 2Cf.

[0030] The resin material 5 adheres to the four surfaces of the magnetic bodies 2A, 2B, and 2C, excluding the side surfaces 2Ae, 2Be, and 2Ce and the side surfaces 2Af, 2Bf, and 2Cf. The resin material 5 adheres to the four surfaces extending along the stacking direction (Z-axis direction). Specifically, the resin material 5 adheres to the main surfaces 2Aa, 2Ba, and 2Ca, the main surfaces 2Ab, 2Bb, and 2Cb, the end surfaces 2Ac, 2Bc, and 2Cc, and the end surfaces 2Ad, 2Bd, and 3Cd. Adhesion refers to a state in which the resin material 5 is in contact with the target surface without any gaps. However, the resin material 5 does not have to be in contact with the entire target surface, and may be separated from a portion of the target surface (for example, an area of less than half of the total area) within the range of manufacturing tolerances, etc. The main surface 2Ab of the magnetic body 2A and a portion of the main surface 2Ba of the magnetic body 2B contact the coil conductor 3A, and the main surface 2Bb of the magnetic body 2B and a portion of the main surface 2Ca of the magnetic body 2C contact the coil conductor 3B, so that all of the main surfaces 2Ab, 2Ba, 2Bb, and 2Ca except for the portions in contact with the coil conductors 3A and 3B are in close contact with the resin material 5.

[0031] Next, the configuration of the gap 20 will be described in more detail with reference to FIG. 5. FIG. 5(a) is an enlarged cross-sectional view showing the configuration around the gap 20 of the magnetic body 2C shown in FIG. 4. FIG. 5(b) is a cross-sectional view taken along line Vb-Vb shown in FIG. 4. Note that while FIG. 5 shows the magnetic body 2C, the same configuration also applies to the magnetic bodies 2A and 2B. As shown in FIG. 5(a), the magnetic ribbons 30 and the adhesive resin 31 are alternately stacked in the Z-axis direction. The magnetic ribbons 30 are thin ribbon members made of the materials listed above as materials for the magnetic body 2C. The thickness of the magnetic ribbons 30 is not particularly limited, but may be set to 5 μm to 70 μm. The adhesive resin 31 is a material that is interposed between a pair of magnetic ribbons 30 to bond them to each other. Materials such as epoxy resin, polyimide resin, polyimideamide resin, and silicone resin may be used as the adhesive resin 31. The thickness of the adhesive resin 31 is not particularly limited, but may be set to 2 μm to 15 μm.

[0032] The gap 20 is formed between the side surface 2Ce and the opposing surface 20a of the resin material 5. The opposing surface 20a is spaced from the side surface 2Ce toward the positive side in the Z-axis direction and is opposed to the side surface 2Ce in the Z-axis direction. The opposing surface 20a is a surface that extends so as to be approximately perpendicular to the stacking direction (Z-axis direction).

[0033] The magnetic body 2C has an X-axis direction (first direction) extending along the side surface 2Ce as its short side direction, and a Y-axis direction (second direction) extending along the side surface 2Ce and perpendicular to the X-axis direction as its long side direction. Therefore, the first length dimension of the magnetic body 2C in the X-axis direction is smaller than the second length dimension of the magnetic body 2C in the Y-axis direction. The first length dimension is determined by the distance between the main surface 2Ca and the main surface 2Cb (see FIG. 5(a)). The second length dimension is determined by the distance between the end surface 2Cc and the end surface 2Cd (see FIG. 5(b)). The second length dimension is not particularly limited, but may be set to, for example, 2 mm to 10 mm. The first length dimension is not particularly limited, but may be set to, for example, 10% to 50% of the second length dimension. The third length dimension of the magnetic body 2C in the Z-axis direction is not particularly limited, but may be set to, for example, 1 mm to 10 mm.

[0034] As shown in FIG. 5(a), the gap 20 has a larger separation distance at the center of the side surface 2Ce of the magnetic body 2C in the X-axis direction than at the end 25. The separation distance of the gap 20 increases from the end 25 of the side surface 2Ce of the magnetic body 2C toward the center in the X-axis direction. The separation distance of the gap 20 may be constant in the X-axis direction near the center of the side surface 2Ce of the magnetic body 2C. The resin material 5 contacts the magnetic body 2C at a portion of the side surface 2Ce of the magnetic body 2C closer to the end 25. In this embodiment, the side surface 2Ce has a gently curved surface that is recessed toward the negative side in the Z-axis direction at a central position 26 in the X-axis direction. The side surface 2Ce contacts the opposing surface 20a of the resin material 5 at the position of the end 25 (and a position around the end 25) in the X-axis direction. The separation distance between the opposing surface 20a and the side surface 2Ce increases from the end 25 toward the central position 26. In the example shown in the figure, both end portions 25 in the X-axis direction are in contact with the opposing surface 20a, but either one of the end portions 25 may be in contact. Also, both end portions 25 do not have to be in contact with the opposing surface 20a. Furthermore, the end portions 25 extend in the Y-axis direction. When the end portions 25 are in contact with the opposing surface 20a, the entire area of the end portions 25 in the Y-axis direction may be in contact with the opposing surface 20a, or only a portion of the area may be in contact with the opposing surface 20a.

[0035] As shown in FIG. 5(b), the gap 20 has a larger separation distance at the center of the side surface 2Ce of the magnetic body 2C in the Y-axis direction than at the end 27. The separation distance of the gap 20 increases from the end 27 of the side surface 2Ce of the magnetic body 2C toward the center in the Y-axis direction. The separation distance of the gap 20 may be constant in the Y-axis direction near the center of the side surface 2Ce of the magnetic body 2C. The resin material 5 contacts the magnetic body 2C at a portion of the side surface 2Ce of the magnetic body 2C closer to the end 27. In this embodiment, the side surface 2Ce has a gently curved surface that is recessed toward the negative side in the Z-axis direction at a central position 28 in the Y-axis direction. The side surface 2Ce contacts the opposing surface 20a of the resin material 5 at the position of the end 27 (and a position around the end 27) in the Y-axis direction. The separation distance between the opposing surface 20a and the side surface 2Ce increases from the end 27 toward the central position 28. In the example shown in the figure, both end portions 27 in the Y-axis direction are in contact with the opposing surface 20a, but either one of the end portions 27 may be in contact. Also, both end portions 27 do not have to be in contact with the opposing surface 20a. Furthermore, the end portions 27 extend along the X-axis. When the end portions 27 are in contact with the opposing surface 20a, the entire area of the end portions 27 in the X-axis direction may be in contact with the opposing surface 20a, or only a portion of the area may be in contact with the opposing surface 20a.

[0036] The size of the separation distance of the gap 20 will be described. Here, the separation distance between the central positions 26, 28 will be described. The separation distance may be set to 0.3% to 3% of the third length dimension in the Z-axis direction of the magnetic body 2C. Alternatively, the separation distance may be set to 10% to 200% of the thickness of the magnetic ribbon 30. Furthermore, the separation distance may be set to 10% to 200% of the average particle size of the second magnetic powder 42 described below.

[0037] The separation distance is not particularly limited as long as the gap 20 is large enough to prevent structural defects between the magnetic body 2C and the resin material 5 due to thermal expansion of the magnetic body 2C. The thermal expansion coefficient of the magnetic body 2C in the stacking direction (Z-axis direction) is greater than its thermal expansion coefficient in directions perpendicular to the stacking direction (X-axis direction, Y-axis direction), and is also greater than the thermal expansion coefficient of the resin material 5 in the Z-axis direction. For example, the thermal expansion coefficient in the directions perpendicular to the stacking direction (X-axis direction, Y-axis direction) may be 5% to 15% of the thermal expansion coefficient of the magnetic body 2C in the stacking direction. The thermal expansion coefficient of the resin material 5 in the Z-axis direction may be 30% to 80% of the thermal expansion coefficient of the magnetic body 2C in the stacking direction.

[0038] As shown in FIGS. 5(a) and 5(b), the inductor 1 further includes a plurality of magnetic powder particles 40. The material of the magnetic powder particles 40 is not particularly limited, and may be pure iron, Fe-Si alloy, permalloy, sendust, amorphous, nanocrystalline soft magnetic material, or the like. The plurality of magnetic powder particles 40 includes first magnetic powder particles 41 present in the resin material 5 and second magnetic powder particles 42 present in the gaps 20. The average particle size of the first magnetic powder particles 41 may be set to 5 μm to 50 μm. The average particle size of the second magnetic powder particles 42 may be set to 5 μm to 50 μm. Note that the second magnetic powder particles 42 may be entirely contained within the gaps 20, or only a portion of the particles may be present within the gaps 20. Note that although the magnetic powder particles 40 shown in the figures are spherical, the shape is not particularly limited.

[0039] Next, the functions and effects of the inductor 1 and DC-DC converter 100 according to this embodiment will be described.

[0040] The inductor 1 of this embodiment comprises coil conductors 3A, 3B, magnetic bodies 2A, 2B, 2C, and a resin material 5 that contains the coil conductors 3A, 3B and the magnetic bodies 2A, 2B, 2C inside, and the inductor 1 has a gap 20 between the resin material 5 and at least one side surface 2Ae, 2Be, 2Ce (first surface) of the magnetic bodies 2A, 2B, 2C.

[0041] The resin material 5 contains the coil conductors 3A and 3B and the magnetic bodies 2A, 2B, and 2C inside. Therefore, when the temperature of the inductor 1 increases due to current flowing through the coil conductors 3A and 3B, the magnetic bodies 2A, 2B, and 2C thermally expand within the resin material 5. In response to this, the inductor 1 has a gap 20 between the resin material 5 and at least one of the side surfaces 2Ae, 2Be, and 2Ce (first surfaces) of the magnetic bodies 2A, 2B, and 2C. The gap 20 absorbs the displacement of the magnetic bodies 2A, 2B, and 2C due to thermal expansion. This prevents the resin material 5 from being pressed against the thermally expanded magnetic bodies 2A, 2B, and 2C. As a result, structural defects due to the thermal expansion of the magnetic bodies 2A, 2B, and 2C can be suppressed.

[0042] The magnetic bodies 2A, 2B, and 2C have a laminated structure of magnetic ribbons 30 and adhesive resin 31, and the side surfaces 2Ae, 2Be, and 2C of the magnetic bodies 2A, 2B, and 2C may be the outermost surfaces in the lamination direction (Z-axis direction) of the laminated structure. The displacement amount due to thermal expansion of the magnetic bodies 2A, 2B, and 2C increases in the lamination direction. Therefore, by providing gaps 20 to the side surfaces 2Ae, 2Be, and 2C where the displacement amount is large, structural defects due to thermal expansion can be suppressed.

[0043] The inductor 1 further includes resin members 6A, 6B, and 6C, and the magnetic bodies 2A, 2B, and 2C have side surfaces 2Af, 2Bf, and 2Cf (second surfaces) that are outermost surfaces on the opposite side of the stacking direction from the side surfaces 2Ae, 2Be, and 2Ce, and the resin members 6A, 6B, and 6C may be arranged in positions facing the side surfaces 2Af, 2Bf, and 2Cf. By arranging the resin members 6A, 6B, and 6C on the other side surfaces 2Af, 2Bf, and 2Cf that have a large amount of displacement due to thermal expansion, the displacement of the side surfaces 2Af, 2Bf, and 2Cf can be suppressed by the resin members 6A, 6B, and 6C.

[0044] The magnetic bodies 2A, 2B, and 2C have side surfaces 2Af, 2Bf, and 2Cf that are outermost surfaces on the opposite side of the stacking direction from the side surfaces 2Ae, 2Be, and 2Ce, and the resin material 5 may be in close contact with surfaces of the magnetic bodies 2A, 2B, and 2C other than the side surfaces 2Ae, 2Be, and 2Ce and the side surfaces 2Af, 2Bf, and 2Cf. In this case, structural defects due to thermal expansion can be suppressed while ensuring close contact between the magnetic bodies 2A, 2B, and 2C and the resin material 5.

[0045] A first length dimension of the magnetic bodies 2A, 2B, and 2C in the X-axis direction (first direction) extending along the side surfaces 2Ae, 2Be, and 2Ce is smaller than a second length dimension of the magnetic bodies 2A, 2B, and 2C in the Y-axis direction (second direction) extending along the side surfaces 2Ae, 2Be, and 2Ce and perpendicular to the X-axis direction, and the gaps 20 may be spaced apart at a greater distance in the X-axis direction at the centers of the side surfaces 2Ae, 2Be, and 2Ce of the magnetic bodies 2A, 2B, and 2C than at their ends. During thermal expansion, the displacement of the side surfaces 2Ae, 2Be, and 2C in the X-axis direction near a central position 26 is greater than that near their ends 25. Therefore, by setting the distance of the gaps 20 to a size that matches the displacement due to thermal expansion, structural defects can be suppressed.

[0046] The magnetic bodies 2A, 2B, and 2C may have a first length dimension in the X-axis direction extending along the side surfaces 2Ae, 2Be, and 2Ce that is smaller than a second length dimension in the Y-axis direction extending along the side surfaces 2Ae, 2Be, and 2Ce and perpendicular to the X-axis direction, and the gaps 20 may have a larger separation distance in the Y-axis direction at the centers of the side surfaces 2Ae, 2Be, and 2C of the magnetic bodies 2A, 2B, and 2C than at their ends. During thermal expansion, the displacement of the side surfaces 2Ae, 2Be, and 2C in the Y-axis direction near a central position 28 is larger than that near end portions 27. Therefore, by setting the separation distance of the gaps 20 to a size that matches the displacement due to thermal expansion, structural defects can be suppressed.

[0047] The resin material 5 may be in contact with the magnetic bodies 2A, 2B, 2C at portions of the side surfaces 2Ae, 2Be, 2Ce of the magnetic bodies 2A, 2B, 2C near the ends 25. In this case, the adhesion between the magnetic bodies 2A, 2B, 2C and the resin material 5 can be increased in portions that are less displaced due to thermal expansion.

[0048] The inductor 1 further includes a plurality of magnetic powders 40, which may include first magnetic powders 41 present in the resin material 5 and second magnetic powders 42 present in the gaps 20. In this case, structural defects due to thermal expansion can be suppressed while maintaining the magnetic properties of the inductor 1.

[0049] The DC-DC converter 500 may include the inductor 1 described above.

[0050] According to the DC-DC converter 500, the same functions and effects as those of the inductor 1 described above can be obtained.

[0051] The present disclosure is not limited to the above-described embodiments.

[0052] In the above-described embodiment, the inductor has multiple coil conductors. However, the number of coil conductors is not particularly limited, and an inductor having a single coil conductor may be provided. For example, the inductor 1 shown in FIG. 6 includes a single coil conductor 3A and magnetic materials 2A and 2B. Such a single coil conductor 3A may be employed in a DC-DC converter 100 shown in FIG. 7. As shown in FIG. 7, the DC-DC converter 100 includes a pair of input terminals to which a DC input voltage is input, a pair of output terminals, a switching element 105 and a choke coil 106 connected in series to the high-potential sides of the pair of input terminals, a diode 103 connected between the junction of the switching element 105 and the choke coil 106 and the low-potential sides of the pair of input terminals, and a capacitor 104 connected between the pair of output terminals. The DC-DC converter 100 operates as a step-down converter that steps down the input DC voltage by switching the switching element 105 on and off based on a control signal from a control circuit (not shown).

[0053] The structures of the coil conductor and magnetic body are not limited to those employed in the above-described embodiments, and may be modified as appropriate without departing from the spirit of the present disclosure. For example, the structures shown in Figures 8 to 10 may be employed. In each of Figures 8 to 10, the resin material 5 is partially cut away to show the coil conductor and magnetic body inside.

[0054] For example, an inductor 1 as shown in FIGS. 8(a) and 8(b) may be employed. The inductor 1 shown in FIG. 8 includes a coil conductor 3C and a pair of magnetic bodies 2D and 2E. In FIG. 8(b), the resin material 5 is cut in the Z-axis direction at the position of the magnetic body 2E on the negative side in the Z-axis direction, thereby showing a gap 20 between the resin material 5 and the side surface 2e of the magnetic body 2E with a solid line. In FIG. 8(b), the magnetic body 2D on the positive side in the Z-axis direction is omitted, thereby showing the shape of the conductor portion 50 with a solid line. The coil conductor 3C has terminal portions 14A and 14B formed on surfaces of the resin material 5 facing each other in the Y-axis direction, and a conductor portion 50 extending in the Y-axis direction between the terminal portions 14A and 14B. The magnetic body 2D is disposed on the positive side of the conductor portion 50 in the X-axis direction, and the magnetic body 2E is disposed on the negative side in the X-axis direction. The stacking direction of the magnetic bodies 2D and 2E is set to the Y-axis direction. The inductor 1 has a gap 20 between the resin material 5 and the side surface 2e on one side in the stacking direction (the negative side in the Y-axis direction).

[0055] For example, an inductor 1 as shown in FIGS. 9(a) and 9(b) may be employed. The inductor 1 shown in FIGS. 9(a) and 9(b) includes a coil conductor 3D and a magnetic body 2F. The coil conductor 3D has terminal portions 14A and 14B formed on the negative surface of the resin material 5 in the Z-axis direction, and a gate-shaped conductor portion 50. The conductor portion 50 has portions extending from the terminal portions 14A and 14B toward the positive side in the Z-axis direction and a portion connecting the upper ends of the extending portions. The conductor portion 50 has a through portion 51 penetrating in the X-axis direction. The magnetic body 2F is provided so as to penetrate the through portion 51 in the X-axis direction. The stacking direction of the magnetic body 2F is set to the Z-axis direction. The inductor 1 has a gap 20 between the resin material 5 and a side surface 2e on one side in the stacking direction (the positive side in the Z-axis direction).

[0056] For example, an inductor 1 as shown in FIGS. 9(c) and 9(d) may be employed. The inductor 1 shown in FIGS. 9(a) and 9(b) includes a coil conductor 3D and a pair of magnetic bodies 2G and 2H. The pair of magnetic bodies 2G and 2H are arranged to sandwich a through portion 51 in the X-axis direction. The stacking direction of the magnetic bodies 2G and 2H is set to the Z-axis direction. The inductor 1 has a gap 20 between the resin material 5 and a side surface 2e on one side in the stacking direction (the positive side in the Z-axis direction).

[0057] For example, an inductor 1 as shown in FIGS. 10(a) and 10(b) may be employed. The inductor 1 shown in FIGS. 10(a) and 10(b) includes a coil conductor 3E and a magnetic body 2K. The coil conductor 3E has terminal portions 14A and 14B formed on surfaces of a resin material 5 facing each other in the Y-axis direction, and a conductor portion 50 wound in a rectangular ring shape. The conductor portion 50 is wound with its winding axis extending in the Z-axis direction. The magnetic body 2K is disposed inside the conductor portion 50. The stacking direction of the magnetic body 2K is set to the Y-axis direction. The inductor 1 has a gap 20 between the resin material 5 and a side surface 2e on one side in the stacking direction (the positive side in the Y-axis direction). The shape of the conductor portion 50 is not particularly limited, and a coil conductor 3F having a ring-shaped conductor portion 50 may be employed as shown in FIGS. 10(c) and 10(d).

[0058] [Form 1] A coil conductor; A magnetic material, a resin material containing the coil conductor and the magnetic material therein, An inductor having a gap between the resin material and at least one first surface of the magnetic body. [Form 2] the magnetic body has a laminated structure of a magnetic ribbon and an adhesive resin, 2. The inductor according to claim 1, wherein the first surface of the magnetic body is the outermost surface in the stacking direction of the stacked structure. [Form 3] Further provided with a resin member, the magnetic body has a second surface that is an outermost surface on the opposite side of the first surface in the stacking direction, The inductor according to aspect 2, wherein the resin member is disposed at a position facing the second surface. [Form 4] the magnetic body has a second surface disposed on the opposite side of the first surface in the stacking direction, The inductor according to aspect 2 or 3, wherein the resin material is in close contact with surfaces of the magnetic body other than the first surface and the second surface. [Form 5] a first length dimension of the magnetic body in a first direction extending along the first surface is smaller than a second length dimension of the magnetic body in a second direction extending along the first surface and perpendicular to the first direction; 5. The inductor according to any one of aspects 1 to 4, wherein the gap has a greater separation distance in the first direction at the center of the first surface of the magnetic body than at the end of the first surface. [Form 6] a first length dimension of the magnetic body in a first direction extending along the first surface is smaller than a second length dimension of the magnetic body in a second direction extending along the first surface and perpendicular to the first direction; The inductor according to any one of modes 1 to 5, wherein the gap has a greater separation distance in the second direction at the center of the first surface of the magnetic body than at the end of the first surface. [Form 7] 6. The inductor according to claim 5, wherein the resin material is in contact with the magnetic body at a portion of the first surface of the magnetic body near an end portion thereof. [Form 8] Further comprising a plurality of magnetic powders; 8. The inductor according to any one of aspects 1 to 7, wherein the plurality of magnetic powders include a first magnetic powder present in the resin material and a second magnetic powder present in the gaps. [Form 9] A DC-DC converter comprising the inductor according to any one of the first to eighth aspects. [Explanation of symbols]

[0059] 1...inductor, 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2K...magnetic body, 3A, 3B, 3C, 3D, 3F...coil conductor, 5...resin material, 6A, 6B, 6C...resin member, 20...gap, 30...magnetic ribbon, 31...adhesive resin, 40...magnetic powder, 41...first magnetic powder, 42...second magnetic powder, 100, 500...DC-DC converter.

Claims

1. A coil conductor; A magnetic material, a resin material containing the coil conductor and the magnetic material therein, An inductor having a gap between the resin material and at least one first surface of the magnetic body.

2. the magnetic body has a laminated structure of a magnetic ribbon and an adhesive resin, The inductor according to claim 1 , wherein the first surface of the magnetic body is an outermost surface in the stacking direction of the stacked structure.

3. Further provided with a resin member, the magnetic body has a second surface that is an outermost surface on the opposite side of the first surface in the stacking direction, The inductor according to claim 2 , wherein the resin member is disposed at a position facing the second surface.

4. the magnetic body has a second surface that is an outermost surface on the opposite side of the first surface in the stacking direction, The inductor according to claim 2 , wherein the resin material adheres closely to surfaces of the magnetic body other than the first surface and the second surface.

5. a first length dimension of the magnetic body in a first direction extending along the first surface is smaller than a second length dimension of the magnetic body in a second direction extending along the first surface and perpendicular to the first direction; The inductor according to claim 1 , wherein the gap is spaced apart at a greater distance in the first direction at the center of the first surface of the magnetic body than at the ends of the first surface.

6. a first length dimension of the magnetic body in a first direction extending along the first surface is smaller than a second length dimension of the magnetic body in a second direction extending along the first surface and perpendicular to the first direction; The inductor according to claim 1 , wherein the gap is spaced apart at a greater distance in the second direction at the center of the first surface of the magnetic body than at the ends of the first surface.

7. The inductor according to claim 5 , wherein the resin material is in contact with the magnetic body at a portion of the first surface of the magnetic body near an end portion of the magnetic body.

8. Further comprising a plurality of magnetic powders; The inductor according to claim 1 , wherein the plurality of magnetic powders include a first magnetic powder present in the resin material and a second magnetic powder present in the gap.

9. A DC-DC converter comprising the inductor according to any one of claims 1 to 8.

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