Composite inductor

Abstract

The present invention provides a composite inductor which enables easy adjustment of a negative coupling coefficient regardless of the size of an element body.　Provided is a composite inductor comprising an element body which includes a magnetic body and which has an upper surface and a bottom surface and a pair of conductors which are disposed in the element body, wherein: the pair of conductors are each provided with a pair of first conductor units which extend parallel to each other, second conductor units which extend in a direction orthogonal to the first conductor units and which respectively connect one ends of the first conductor units between the pair of first conductor units, and a third conductor unit which is bent and extends from the other ends of the first conductor units toward the bottom surface of the element body; in a top view of the element body as seen from the upper surface side, the pair of conductors are disposed in the element body such that the first conductor units overlap each other and the second conductor units do not overlap each other; and the second conductor units are formed with a narrower width than the first conductor units.

Description

Composite Inductor

[0001] The present invention relates to a composite inductor.

[0002] Patent Document 1 discloses a magnetic assembly having two coils formed of punched metal or the like as a configuration related to a composite inductor. In the magnetic assembly described in Patent Document 1, the two coils each include a linear first conductive path, a linear second conductive path extending perpendicularly from the first conductive path, and a third conductive path extending perpendicularly from the second conductive path and extending parallel to the first conductive path. In Patent Document 1, the first conductive path and the third conductive path of the first coil overlap the first conductive path and the third conductive path of the second coil in a predetermined viewing direction, and the second conductive path of the first coil and the second conductive path of the second coil do not overlap. In Patent Document 1, the widths of the first conductive path, the second conductive path, and the third conductive path are regarded as constant.

[0003] Japanese Patent Publication No. 2012-526383

[0004] In the composite inductor having the above configuration, since the structure is simple, when the size of the element body is small, there is a problem that it is difficult to adjust the important negative coupling coefficient in the composite inductor.

[0005] One aspect of the present invention is a composite inductor having a body containing a magnetic material and having an upper surface and a bottom surface, and a pair of conductors disposed in the body. Each of the pair of conductors includes a pair of first conductor portions extending parallel to each other, a second conductor portion extending in a direction orthogonal to the first conductor portions and connecting one end of each of the first conductor portions between the pair of first conductor portions, and a third conductor portion bent and extending from the other end of the first conductor portion toward the bottom surface side of the body. In a top view of the body as viewed from the upper surface side, the pair of conductors are disposed in the body such that the first conductor portions overlap each other and the second conductor portions do not overlap each other, and the width of the second conductor portion is formed narrower than the width of the first conductor portion. Note that this specification includes all the contents of Japanese Patent Application No. 2024-196095 filed on November 8, 2024.

[0006] According to the present invention, it is possible to provide a composite inductor that is not limited by the size of the base body and that allows for easy adjustment of the negative coupling coefficient.

[0007] Figure 1 is a perspective view of the composite inductor according to the first embodiment, viewed from the top. Figure 2 is a top view showing the positional relationship of a pair of coil conductors in the composite inductor according to the first embodiment. Figure 3 is a side view showing the positional relationship of a pair of coil conductors in the composite inductor according to the first embodiment. Figure 4 is a diagram showing the relationship between the overlap ratio, coupling coefficient, and width ratio for a pair of coil conductors arranged in the element of the first embodiment. Figure 5 is a diagram showing the relationship between the overlap ratio, coupling coefficient, and width ratio for a pair of coil conductors arranged in the element of the second embodiment. Figure 6 is a diagram showing the relationship between the width ratio, the top view of the coil conductors, and the magnetic flux generated by the coil conductors for a pair of coil conductors arranged in the element of the second embodiment. Figure 7 is a perspective view of the composite inductor according to the second embodiment, viewed from the top. Figure 8 is a top view showing the positional relationship of a pair of coil conductors in the composite inductor according to the second embodiment. Figure 9 is a side view showing the positional relationship of a pair of coil conductors in the composite inductor according to the second embodiment. Figure 10 is a top view showing the positional relationship of a pair of coil conductors in the element of the composite inductor according to the third embodiment. Figure 11 shows the relationship between the overlap ratio, coupling coefficient, and width ratio for a pair of coil conductors arranged in the first embodiment. Figure 12 shows the relationship between the width ratio, the top view of the coil conductors, and the magnetic flux generated by the coil conductors for a pair of coil conductors arranged in the first embodiment. Figure 13 is a side view of a composite inductor according to the fourth embodiment.

[0008] Embodiments of the present invention will be described below with reference to the drawings.

[0009] [1. First Embodiment] [Overall Configuration of the Composite Inductor] Figure 1 is a perspective view of the composite inductor 1 according to the first embodiment, viewed from the top surface 12. The composite inductor 1 of this embodiment is configured as a surface-mount type electronic component. The composite inductor 1 of this embodiment comprises a substantially rectangular parallelepiped base body 2, which is one aspect of a substantially hexahedral shape, and four external electrode portions 4 provided on the surface of the base body 2.

[0010] In the following, in the base body 2, the first main surface that faces the mounting substrate (not shown) during mounting is defined as the bottom surface 10. The second main surface opposite the bottom surface 10 is defined as the top surface 12. Furthermore, a pair of third main surfaces perpendicular to the bottom surface 10 are defined as end surfaces 14. In addition, a pair of fourth main surfaces perpendicular to the bottom surface 10 and the pair of end surfaces 14 are defined as side surfaces 16.

[0011] As shown in Figure 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the base body 2, the distance between the pair of side surfaces 16 is defined as the width W of the base body 2, and the distance between the pair of end surfaces 14 is defined as the length L of the base body 2. Furthermore, the direction of the thickness T is referred to as the thickness direction DT, the direction of the width W is referred to as the width direction DW, and the direction of the length L is referred to as the length direction DL.

[0012] Hereinafter, the surface along the length direction DL and the thickness direction DT (the surface perpendicular to the width direction DW) will be referred to as the LT surface, the surface along the thickness direction DT and the width direction DW (the surface perpendicular to the length direction DL) will be referred to as the WT surface, and the surface along the length direction DL and the width direction DW (the surface perpendicular to the thickness direction DT) will be referred to as the LW surface. Furthermore, the cross-sections of the composite inductor 1 along the LT surface, WT surface, and LW surface will be referred to as the LT cross-section, WT cross-section, and LW cross-section, respectively.

[0013] In this embodiment, the base body 2 comprises a pair of coil conductors 20 and 30, and a substantially rectangular parallelepiped-shaped magnetic core (magnetic material) 40 in which the coil conductors 20 and 30 are embedded. The base body 2 in this embodiment is configured as a molded inductor in which the coil conductors 20 and 30 are sealed in the magnetic core 40.

[0014] The magnetic core 40 is a molded body formed by compressing a mixed powder of magnetic particles and resin into a roughly hexahedral shape by pressurizing and heating it while enclosing the coil conductors 20 and 30. During this process, both ends of the coil conductors 20 and 30 are exposed on the bottom surface 10 side. A total of four external electrode portions 4 are formed by the ends of the coil conductors 20 and 30.

[0015] The magnetic particles contained in the mixed powder of this embodiment are made of a soft magnetic material. The magnetic particles are particles having metal particles, an oxide film covering the surface of the metal particles, and an insulating film covering the surface of the oxide film. The insulation resistance and dielectric strength are increased by covering the metal particles with the oxide film and the insulating film. The magnetic particles may have only one particle size, or they may have two or more particle sizes with different particle sizes, and each magnetic particle may be different. In the magnetic particles of this embodiment, amorphous iron powder or crystalline atomized iron powder is used for the larger particle size metal particles, and carbonyl iron powder is used for the smaller particle size metal particles. Furthermore, nanocrystalline materials may be used to further reduce losses. The insulating film for the larger particle size metal particles is phosphate glass formed by a mechanochemical method, and the insulating film for the smaller particle size is iron oxide formed by surface oxidation, or formed by a sol-gel method.

[0016] The resin contained in the mixed powder of this embodiment includes multiple types of resin materials. For example, the resin materials contained in the mixed powder of this embodiment include bisphenol A type epoxy resin and rubber-modified epoxy resin. This makes it possible to manufacture a composite inductor 1 in which both the strength and toughness of the base body 2 are improved. In addition to epoxy resin, thermosetting resins such as phenolic resin, polyester resin, polyimide resin, and polyolefin resin may be used as the resin materials contained in the mixed powder.

[0017] The composite inductor 1 with this configuration is used as an electronic component in electrical circuits where large currents flow, and as a choke coil in DC-DC converter circuits and power supply circuits. Furthermore, the composite inductor 1 is used as an electronic component in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, and medical and industrial machinery. However, the applications of the composite inductor 1 are not limited to these.

[0018] [Conductor Configuration] Figure 2 is a top view showing the positional relationship of a pair of coil conductors 20 and 30 of the composite inductor 1 according to the first embodiment. Figure 3 is a side view showing the positional relationship of a pair of coil conductors 20 and 30 of the composite inductor 1 according to the first embodiment. In Figures 2 and 3, the first coil conductor 20 has a dot pattern. The coil conductors 20 and 30 are formed from metal plates. The coil conductors 20 and 30 in this embodiment are press-formed products made by punching out copper plates. The coil conductors 20 and 30 are roughly U-shaped when viewed from above (viewed from the top surface 12 side of the base body 2) (see Figure 2). The coil conductors 20 and 30 are roughly J-shaped when viewed from the side (viewed from the side surface 16 side of the base body 2) (see Figure 3).

[0019] In detail, the first coil conductor 20 has a pair of extended portions (first conductor portions) 21 that extend in the length direction DL. The pair of extended portions 21 extend parallel to each other. The extended portions 21 are in the shape of a roughly rectangular flat plate. At one end of the extended portions 21, a connecting portion (second conductor portion) 22 is formed between the pair of extended portions 21, extending in the width direction DW. The connecting portion 22 connects the one ends of the pair of extended portions 21. The connecting portion 22 is in the shape of a roughly rectangular flat plate. The connecting portion 22 has a thickness t2 (see Figure 3) similar to the thickness t1 (see Figure 3) of the extended portions 21.

[0020] At the other end of the extended portion 21, that is, on the side opposite to the connecting portion 22 of the extended portion 21 in the longitudinal direction DL, a bent portion (third conductor portion) 23 is formed that curves and extends from the extended portion 21 toward the bottom surface 10 (see Figure 1). The bent portion 23 is in the shape of a roughly L-shaped bent plate. The bent portion 23 has a thickness t3 (see Figure 3) similar to the thickness t1 of the extended portion 21.

[0021] In the following description, the bottom surface 10 side will be considered the "down" side in the thickness direction DT, and the top surface 12 side will be considered the "up" side in the thickness direction DT.

[0022] As shown in Figure 3, the bent portion 23 specifically includes a curved plate-shaped curved connecting portion 23a that curves downward as it moves away from the other end of the extended portion 21, a flat plate-shaped lead portion 23b that extends downward from the lower end of the curved connecting portion 23a, a curved plate-shaped curved connecting portion 23c that curves toward the extended portion 21 in the longitudinal direction DL as it proceeds downward from the lower end of the lead portion 23b, and a flat plate-shaped electrode forming portion 23d that extends in the longitudinal direction DL from the curved connecting portion 23c. The lower surface of the electrode forming portion 23d is exposed to the outside from the magnetic core 40 (see Figure 1). The lower surface of the electrode forming portion 23d forms an external electrode portion 4 (see Figure 1). The external electrode portion 4 is electrically connected to the wiring of a circuit board (not shown) by appropriate mounting means such as solder.

[0023] The second coil conductor 30 is formed in the same manner as the first coil conductor 20, except that the size of the thickness DT of the bent portion 33 is different. That is, the second coil conductor 30 has an extended portion 31, a connecting portion 32, and a bent portion 33, corresponding to the extended portion 21, connecting portion 22, and bent portion 23 of the first coil conductor 20.

[0024] The bent portion 33 of the second coil conductor 30 has a curved connection portion 33a, an outlet portion 33b, a curved connection portion 33c, and an electrode forming portion 33d, corresponding to the curved connection portion 23a, outlet portion 23b, curved connection portion 23c, and electrode forming portion 23d of the bent portion 23 of the first coil conductor 20. The second coil conductor 30 differs from the first coil conductor 20 in that the size of the thickness direction DT of the outlet portion 33b is smaller than the size of the thickness direction DT of the outlet portion 23b of the first coil conductor 20.

[0025] As shown in Figures 1 to 3, the first coil conductor 20 and the second coil conductor 30 are arranged in the base body 2 so as to overlap when viewed from above. Specifically, the positions of the first coil conductor 20 and the second coil conductor 30 in the width direction DW are aligned. Also, the connecting portion 22 of the first coil conductor 20 and the connecting portion 32 of the second coil conductor 30 are spaced apart in the length direction DL. Furthermore, the first coil conductor 20 on the side with the longer lead portion 23b is arranged to cover the second coil conductor 30 on the side with the shorter lead portion 33b from above. In this way, the first coil conductor 20 and the second coil conductor 30 are arranged in the base body 2 so as to overlap when viewed from above with their extended portions 21 and 31 facing each other.

[0026] Here, the overlap ratio is defined as the ratio of overlap between the extended portions 21 and 31. That is, in Figures 2 and 3, when the second coil conductor 30 is positioned at the location indicated by the dashed line, the second coil conductor 30 is spaced apart from the first coil conductor 20, indicated by the solid line, and the overlap ratio is 0%. Then, as the second coil conductor 30 is positioned at the location indicated by the dashed line and the solid line, the amount of overlap between the extended portions 21 and 31 between the coil conductors 20 and 30 increases sequentially, and the overlap ratio increases.

[0027] A flat insulating member 50 (see Figure 1) is placed between the first coil conductor 20 and the second coil conductor 30. The insulating members 50 are placed in pairs, corresponding to the pair of extended portions 21 and 31. The insulating members 50 are made of, for example, resin. The insulating members 50 ensure insulation between the coil conductors 20 and 30 and form a predetermined insulating gap. The insulating members 50 are formed to the same width (length DW in the width direction) as the extended portions 21 and 31. The insulating members 50 are placed so as not to protrude from the extended portions 21 and 31, with their width DW positions coinciding with the extended portions 21 and 31.

[0028] Instead of arranging the insulating member 50 between the coil conductors 20 and 30, an insulating layer may be formed on the lower surface of the extended portion 21 of the first coil conductor 20 and on the upper surface of the extended portion 31 of the second coil conductor 30. The insulating layer is made of, for example, polyimidoamide resin. While polyimidoamide resin is preferable for the insulating layer, polyurethane resin, polyester resin, epoxy resin, etc. may be used instead.

[0029] The first coil conductor 20 and the second coil conductor 30 overlap in a top view with a predetermined insulation gap, provided by the insulating member 50 or insulating layer. In a top view, the enclosed shape of the pair of coil conductors 20 and 30 forms a substantially rectangular opening Op (see Figure 2).

[0030] In this embodiment, the conductor width (length in the length direction DL) w2 of the connecting sections 22 and 32 is formed to be narrower than the conductor width (length in the width direction DW) w1 of the extended sections 21 and 31. Here, the conductor width w1 is defined by the conductor width of the extended sections 21 and 31 at a position corresponding to the center of the opening Op. Similarly, the conductor width w2 is defined by the conductor width of the connecting sections 22 and 32 at a position corresponding to the center of the opening Op. More specifically, the conductor width w1 of the extended sections 21 and 31 is defined by the conductor width at a position where the length in the extension direction (length in the length direction DL) of the extended sections 21 and 31 is bisected. Similarly, the conductor width w2 of the connecting sections 22 and 32 is defined by the conductor width at a position where the length in the extension direction (length in the width direction DW) of the connecting sections 22 and 32 is bisected.

[0031] Generally, the coupling coefficient of two inductors is determined by the magnetic flux circulating around both inductor portions, i.e., the two coils. For example, in the composite inductor 1 of this embodiment, the coupling coefficient is determined by the magnetic flux Φ1 (see Figure 1) circulating around both the extended portions 21 and 31 of the coil conductors 20 and 30. Furthermore, in the composite inductor 1 having substantially U-shaped coil conductors 20 and 30, as in this embodiment, the reactance values ​​of the extended portions 21 and 31 contribute to the negative coupling of the composite inductor 1, while the reactance values ​​of the connecting portions 22 and 32 and the bent portions 23 and 33 contribute to the positive coupling of the composite inductor 1 and do not contribute to the negative coupling.

[0032] In this context, it is important to adjust the coupling coefficient to a negative value in a composite inductor. The most common and simple way to adjust the coupling coefficient of a composite inductor to a negative value is to narrow the insulation gap. However, in a composite inductor 1 having roughly U-shaped coil conductors 20 and 30, even if the insulation gap is narrowed, the effect of the difference in narrowness is small, making it difficult to increase the absolute value of the negative coupling coefficient.

[0033] Therefore, in the composite inductor 1, in order to adjust the negative coupling coefficient, it is conceivable to increase the length of the extensions 21 and 31 that contribute to the negative coupling, instead of adjusting the insulation gap. This is because if the length of the extensions 21 and 31 is increased, the magnetic flux Φ1 circulating around the extensions 21 and 31 increases, and the absolute value of the negative coupling coefficient can be increased. However, when the length of the extensions 21 and 31 is increased, there is a problem that the size of the main body 2 tends to increase.

[0034] Therefore, in this embodiment, the conductor width w2 of the connecting portions 22 and 32 is made narrower than the conductor width w1 of the extended portions 21 and 31. This allows for a wider opening area of ​​the opening Op while suppressing the size of the main body 2. In other words, even if the length of the extended portions 21 and 31 remains the same as that of the main body 2, the length of the extended portions 21 and 31 that form the opening Op becomes longer, and the magnetic flux Φ1 circulating around the extended portions 21 and 31 can be increased. That is, the absolute value of the negative coupling coefficient of the composite inductor 1 can be increased while suppressing the size of the main body 2.

[0035] Figure 4 shows the relationship between the overlap ratio, coupling coefficient, and width ratio w1 / w2 for a pair of coil conductors 20 and 30 arranged in the base body 2 of the first embodiment. Figure 5 shows the relationship between the overlap ratio, coupling coefficient, and width ratio w1 / w2 for a pair of coil conductors 20 and 30 arranged in the base body 2 of the second embodiment. Figures 4 and 5 show the simulation analysis results by magnetic field analysis assuming a pair of coil conductors 20 and 30 arranged in the base body 2 of each embodiment. Femtet® (manufactured by Murata Software Co., Ltd.) was used for the simulation. In this embodiment, the base body 2 of the first embodiment is assumed to have a length L dimension of 9.1 mm and a width W dimension of 6.5 mm. In this embodiment, the base body 2 of the second embodiment is assumed to have a length L dimension of 6.5 mm and a width W dimension of 6.5 mm.

[0036] In Figures 4 and 5, the vertical axis represents the coupling coefficient, and the horizontal axis represents the overlap rate. In Figures 4 and 5, the black circles on the thick solid line indicate the values ​​when the width ratio w1 / w2 is 0.7. The black circles on the dashed line indicate the values ​​when the width ratio w1 / w2 is 0.8. The black circles on the thin solid line indicate the values ​​when the width ratio w1 / w2 is 1.0. The white circles on the dashed line indicate the values ​​when the width ratio w1 / w2 is 1.3. The white circles on the dashed line indicate the values ​​when the width ratio w1 / w2 is 1.8.

[0037] As shown in Figures 4 and 5, it can be observed that the absolute value of the negative coupling coefficient increases as the overlap ratio increases, regardless of the width ratio w1 / w2. In other words, it can be observed that the absolute value of the negative coupling coefficient increases as the opening Op increases in the length direction DL. Furthermore, even with the same overlap ratio, it can be observed that the absolute value of the negative coupling coefficient increases as the width ratio w1 / w2 increases. In other words, even when the lengths of the extended portions 21 and 31 are the same, it can be observed that the absolute value of the negative coupling coefficient increases as the length of the extended portions 21 and 31 that form the opening Op increases.

[0038] Therefore, in the composite inductor 1 of this embodiment, the width ratio w1 / w2 is greater than 1, and the absolute value of the negative coupling coefficient can be easily adjusted by appropriately changing the overlap ratio and the width ratio w1 / w2. In particular, when the overlap ratio is small, that is, when the aperture Op is small, the absolute value of the negative coupling coefficient can be effectively adjusted by the width ratio w1 / w2.

[0039] Here, it is observed that the case shown in Figure 5, based on the base body 2 of the second embodiment, shows a larger difference in the coupling coefficient due to the value of the width ratio w1 / w2 compared to the case shown in Figure 4, based on the base body 2 of the first embodiment, and that the influence of the width ratio w1 / w2 on the coupling coefficient tends to be greater.

[0040] Figure 6 shows the relationship between the width ratio w1 / w2 of a pair of coil conductors 20 and 30 arranged in the base body 2 of the second embodiment, the top view of the coil conductors 20 and 30, and the magnetic flux Φ2 generated by the coil conductors 20 and 30. Figure 6 is based on the results of a simulation analysis using magnetic field analysis assuming a pair of coil conductors 20 and 30 arranged in the base body 2 of the second embodiment, i.e., the results of a magnetic field simulation. In this magnetic field simulation, the width ratio w1 / w2 of the conductor width w1 of the extended parts 21 and 31 to the conductor width w2 of the connecting parts 22 and 32 was changed to determine the magnetic flux Φ2 generated in the center of the width direction DW of the coil conductors 20 and 30.

[0041] The upper part of Figure 6 shows the width ratio w1 / w2. The middle part of Figure 6 shows a top view of a pair of coil conductors 20 and 30 corresponding to the width ratio w1 / w2 in the upper part of Figure 6. The lower part of Figure 6 visualizes the state of the magnetic flux Φ2 in the LT cross section at the center of the width direction DW of the coil conductors 20 and 30 in the middle part of Figure 6.

[0042] As shown in the lower part of Figure 6, when the width ratio w1 / w2 is 1.8 and the conductor width w2 of the connecting sections 22 and 32 is smaller than the conductor width w1 of the extended sections 21 and 31, a magnetic flux Φ2 circulating around each connecting section 22 and 32 is observed. In other words, a state is observed where there is little interference between the magnetic flux Φ2 around connecting section 22 and the magnetic flux Φ2 around connecting section 32.

[0043] On the other hand, when the width ratio w1 / w2 is 0.7 and the conductor width w2 of the connecting portions 22 and 32 is larger than the conductor width w1 of the extending portions 21 and 31, a magnetic flux Φ2 that circulates around both the connecting portion 22 and the connecting portion 32 is confirmed. That is, it is confirmed that the magnetic fluxes Φ2 generated between the connecting portions 22 and 32 are positively coupled with each other.

[0044] Therefore, in the case of the element body 2 of the second embodiment where the length L dimension is 6.5 mm, the width W dimension is 6.5 mm, and the aspect ratio (W / L) is 1:1, since the distance between the connecting portions 22 and 32 tends to be close, it was confirmed that the magnetic flux Φ2 between the connecting portions 22 and 32 is likely to be positively coupled. That is, in the case of the element body 2 of the second embodiment, if the conductor width w2 of the connecting portions 22 and 32 is reduced, the influence of the increase in the distance between the connecting portions 22 and 32 is large, and the influence of suppressing the positive coupling is relatively likely to increase. Therefore, when the aspect ratio (W / L) approaches 1:1 as in the element body 2 of the second embodiment, the negative coupling coefficient can be effectively and easily adjusted by the width ratio w1 / w2.

[0045] Therefore, even in the case of the composite inductor 1 with low L and high current, by making the conductor width w2 of the connecting portions 22 and 32 smaller than the conductor width w1 of the extending portions 21 and 31 as in the present embodiment, it is easy to reduce the negative coupling coefficient of the composite inductor 1. Therefore, even in the case of the composite inductor 1 with low L and high current, by appropriately changing the length in the extending direction of the extending portions 21 and 31 and the width ratio w1 / w2, it is not restricted by the size of the element body 2, and it is easy to adjust the negative coupling coefficient.

[0046] As described above, the composite inductor 1 of the first embodiment includes a magnetic core 40 and a base body 2 having a top surface 12 and a bottom surface 10, and a pair of coil conductors 20 and 30 disposed in the base body 2. In this composite inductor 1, each of the pair of coil conductors 20 and 30 includes a pair of extending portions 21 and 31 that extend parallel to each other, a connecting portion 22 and 32 that extends in a direction orthogonal to the extending portions 21 and 31 and connects one ends of the extending portions 21 and 31 between the pair of extending portions 21 and 31, and bending portions 23 and 33 that are bent from the other ends of the extending portions 21 and 31 and extend toward the bottom surface 10 side of the base body 2. At this time, in a top view of the base body 2 viewed from the top surface 12 side, the pair of coil conductors 20 and 30 are disposed in the base body 2 such that the extending portions 21 and 31 overlap each other and the connecting portions 22 and 32 do not overlap each other. Further, the conductor width w2 of the connecting portions 22 and 32 is formed to be narrower than the conductor width w1 of the extending portions 21 and 31. According to this configuration, it is possible to provide the composite inductor 1 that is not restricted by the size of the base body 2 and is easy to adjust the negative coupling coefficient.

[0047] In the first embodiment, the base body 2 includes a magnetic core 40 composed of metal magnetic particles and resin, and the pair of coil conductors 20 and 30 are embedded in the base body 2. According to this configuration, in the composite inductor 1 embedded in the base body 2 including metal magnetic particles and resin, the composite inductor 1 is not restricted by the size of the base body 2, and the negative coupling coefficient of the composite inductor 1 can be easily adjusted.

[0048] [2. Second Embodiment] Next, the second embodiment will be described. Note that the same components as those in the above-described first embodiment may be denoted by the same reference numerals and the description thereof may be omitted.

[0049] Figure 7 is a perspective view of the composite inductor 1 according to the second embodiment, viewed from the top surface 12. Figure 8 is a top view showing the positional relationship of the pair of coil conductors 220 and 230 of the composite inductor 1 according to the second embodiment. Figure 9 is a side view showing the positional relationship of the pair of coil conductors 220 and 230 of the composite inductor 1 according to the second embodiment. Figures 7 to 9 correspond to Figures 1 to 3 of the first embodiment, respectively. In the second embodiment, the thickness t2 of the connecting portions 222 and 232 of the coil conductors 220 and 230 (see Figure 9) is thicker than the thickness t1 of the extended portions 21 and 31 (see Figure 9), which is different from the first embodiment.

[0050] In detail, the connecting portion 222 of the first coil conductor 220 in the second embodiment has a connecting portion main body 222a in the center of the extension direction (center of the width direction DW). The connecting portion main body 222a has a constant or substantially constant cross-sectional shape of the LT cross section. Connecting portions 222b are formed at both ends of the connecting portion main body 222a in the extension direction (both ends of the width direction DW). At both ends of the connecting portion main body 222b in the extension direction (both ends of the width direction DW), the thickness decreases and the conductor width increases as it moves away from the connecting portion main body 222a. The pair of connecting portions 222b are connected to their respective extension portions 21.

[0051] The second coil conductor 230 also has a connecting portion 232 formed in the same way as the connecting portion 222 of the first coil conductor 220. That is, the connecting portion 232 of the second coil conductor 230 has a connecting portion body 232a and a pair of connecting portions 232b, corresponding to the connecting portion body 222a and a pair of connecting portions 222b of the connecting portion 222 of the first coil conductor 220.

[0052] The connecting portions 222 and 232 in this embodiment may be formed by plastic deformation. That is, the connecting portions 222 and 232 formed by punching out a copper plate may be formed by compressing the portion in the longitudinal direction DL (direction of the conductor width w2).

[0053] Specifically, for example, portions that will become the connecting portions 222 and 232 are punched out with the same conductor width w1 as the extended portions 21 and 31. Then, the portions that will become the connecting portions 222 and 232 are compressed in the length direction DL (direction of the conductor width w2). This forms the connecting portions 222 and 232. As an example, in the extended portions 21 and 31, the conductor width w1 is set to 1.4 mm and the thickness t1 is set to 0.4 mm. In the connecting portions 222 and 232, the conductor width w2 is set to 0.8 mm and the thickness t2 is set to 0.7 mm. The thickness t2 of the connecting portions 222 and 232 (see Figure 9) is the thickness of the central part of the connecting portions 222 and 232 in the extension direction (central part in the width direction DW). In this embodiment, the thickness t2 of the connecting portions 222 and 232 is defined by the thickness of the connecting portion main body portions 222a and 232a.

[0054] As described above, in the composite inductor 1 of the second embodiment, similar to the first embodiment, when viewed from above, the pair of coil conductors 220 and 230 are arranged in the base body 2 such that the extended portions 21 and 31 overlap each other, but the connecting portions 222 and 232 do not overlap each other. Furthermore, the conductor width w2 of the connecting portions 222 and 232 is formed to be narrower than the conductor width w1 of the extended portions 21 and 31. Therefore, in the second embodiment as well, similar to the first embodiment, a composite inductor 1 can be provided that is not limited by the size of the base body 2 and allows for easy adjustment of the negative coupling coefficient.

[0055] In particular, in the second embodiment, the thickness t2 of the connecting portions 222 and 232 is greater than the thickness t1 of the extended portions 21 and 31. With this configuration, by making the thickness t2 of the connecting portions 222 and 232 greater than that of the extended portions 21 and 31, it is possible to suppress the reduction in the cross-sectional area of ​​the connecting portions 222 and 232 (cross-sectional area of ​​the LT section) relative to the cross-sectional area of ​​the extended portions 21 and 31 (cross-sectional area of ​​the WT section). Therefore, it is possible to reduce the conductor width w2 of the connecting portions 222 and 232 while making it easier to suppress the increase in the DC resistance of the connecting portions 222 and 232.

[0056] Furthermore, in the second embodiment, the cross-sectional area of ​​the extended portions 21 and 31 (cross-sectional area of ​​the WT section) and the cross-sectional area of ​​the connecting portions 222 and 232 (cross-sectional area of ​​the LT section) are equal. With this configuration, it is easier to reduce the DC resistance of the connecting portions 222 and 232 compared to the case where the cross-sectional area of ​​the connecting portions 222 and 232 is smaller than the cross-sectional area of ​​the extended portions 21 and 31. In addition, with this configuration, it is possible to form connecting portions 222 and 232 with a thickness t2 by utilizing plastic deformation.

[0057] [3. Third Embodiment] Next, a third embodiment will be described. Note that components similar to those in the first embodiment described above may be denoted by the same reference numerals and their descriptions may be omitted.

[0058] Figure 10 is a top view showing the positional relationship of a pair of coil conductors 320 and 330 in the base body 2 of the composite inductor 1 according to the third embodiment. Figure 10 corresponds to Figure 2 of the first embodiment. In the third embodiment, the bent portions (widened portions) 323 and 333 of the coil conductors 320 and 330 are wider than the extended portions 21 and 31, which is different from the first embodiment. In detail, in the third embodiment, the conductor width w3 of the bent portions 323 and 333 is wider than the conductor width w1 of the extended portions 21 and 31, and the bent portions 323 and 333 are located inside the width direction DW of the extended portions 21 and 31. The conductor width w3 of the bent portions 323 and 333 is defined by the conductor width at the center of the extension direction (center of the thickness direction DT) of the lead-out portions 323b and 333b.

[0059] In this embodiment, the bent portions 323 and 333 are formed to be wider than the conductor width w1 of the extended portions 21 and 31 on both sides in the width direction DW. The bent portions 323 and 333 are the same as the bent portions 23 and 33 of the first embodiment, except that they are wider than the bent portions 23 and 33. That is, in this embodiment, the entirety of the bent portions 323 and 333 is wider than the conductor width w1 of the extended portions 21 and 31.

[0060] Figure 11 shows the relationship between the overlap ratio, coupling coefficient, and width ratio w3 / w1 for a pair of coil conductors 320 and 330 arranged in the first embodiment of the element 2. Figure 11 shows the analysis results from a magnetic field simulation assuming a pair of coil conductors 320 and 330 arranged in the first embodiment of the element 2.

[0061] In Figure 11, the vertical axis represents the coupling coefficient, and the horizontal axis represents the overlap rate. In Figure 11, the black circles on the thick solid line indicate the values ​​when the width ratio w3 / w1 is 1.07. The black circles on the dashed line indicate the values ​​when the width ratio w3 / w1 is 1.14. The black circles on the thin solid line indicate the values ​​when the width ratio w3 / w1 is 1.21. The white circles on the dashed line indicate the values ​​when the width ratio w3 / w1 is 1.29. The white circles on the dashed line indicate the values ​​when the width ratio w3 / w1 is 1.36. The white circles on the dashed line indicate the values ​​when the width ratio w3 / w1 is 1.43.

[0062] As shown in Figure 11, it can be observed that the absolute value of the negative coupling coefficient increases as the overlap rate increases, regardless of the width ratio w3 / w1. Furthermore, even with the same overlap rate, it can be observed that the absolute value of the negative coupling coefficient increases as the width ratio w3 / w1 increases. In particular, it can be observed that the greater the overlap rate, specifically when the overlap rate is around 70% or higher, the greater the influence of the difference in the width ratio w3 / w1 on the negative coupling coefficient.

[0063] Figure 12 shows the relationship between the width ratio w3 / w1 of a pair of coil conductors 320 and 330 arranged in the base body 2 of the first embodiment, the top view of the coil conductors 320 and 330, and the magnetic flux Φ2 generated by the coil conductors 320 and 330. Figure 12 is based on the analysis results of a magnetic field simulation assuming a pair of coil conductors 320 and 330 arranged in the base body 2 of the first embodiment. In this magnetic field simulation, the width ratio w3 / w1 of the conductor width w3 of the bent portions 322 and 332 to the conductor width w1 of the extended portions 21 and 31 was changed to determine the magnetic flux Φ2 generated near the extended portions 21 and 31 of the connecting portions 22 and 32 of the coil conductors 320 and 330.

[0064] The upper part of Figure 12 shows the width ratio w3 / w1. The middle part of Figure 12 shows a top view of a pair of coil conductors 320 and 330 corresponding to the width ratio w3 / w1 in the upper part of Figure 12. The lower part of Figure 12 visualizes the state of the magnetic flux Φ2 in the LT cross section near the extended portions 21 and 31 of the connecting portions 22 and 32 of the coil conductors 320 and 330 in the middle part of Figure 12. Specifically, it visualizes the state of the magnetic flux Φ2 in the cross section of the line XII-XII in the middle part of Figure 12.

[0065] As shown in the lower part of Figure 12, it can be confirmed that the larger the conductor width w3 of the bent portions 323 and 333 is compared to the conductor width w1 of the extended portions 21 and 31, the greater the magnetic flux Φ2 generated around the connecting portions 22 and 32. This is because, as shown in the middle part of Figure 12, the larger the conductor width w3 of the bent portions 323 and 333 is compared to the conductor width w1 of the extended portions 21 and 31, the more the positions occupied by the bent portions 323 and 333 overlap with the positions occupied by the connecting portions 22 and 32 in the width direction DW, and as a result, the bent portions 323 and 333 block the magnetic flux Φ2 generated in the connecting portions 22 and 32.

[0066] In this case, if the overlap ratio is large, the bent portions 323 and 333 tend to approach the connecting portions 22 and 32 in the longitudinal direction DL. For this reason, the larger the overlap ratio, the greater the effect of blocking by the bent portions 323 and 333 tends to be, and the greater the influence of the width ratio w3 / w1 on the negative coupling coefficient.

[0067] Therefore, in this embodiment, since the conductor width w3 of the bent portions 323 and 333 is larger than the conductor width w1 of the extended portions 21 and 31, it is easier to increase the absolute value of the negative coupling coefficient of the composite inductor 1. In particular, in this embodiment, the conductor width w3 of the electrode forming portions 323d and 333d (see Figure 12) of the bent portions 323 and 333 is also widened, so the connection strength with the mounting substrate (not shown) can be increased. In addition, because the conductor width w3 of the bent portions 323 and 333 is widened, the current density at the connection portion with the mounting substrate (not shown) can be reduced, and heat generation at the external electrode portion 4 can also be reduced.

[0068] As described above, in the composite inductor 1 of the third embodiment, similar to the first embodiment, the pair of coil conductors 320 and 330 are arranged in the base body 2 such that, when viewed from above, the extended portions 21 and 31 overlap each other, but the connecting portions 22 and 32 do not overlap each other. Furthermore, the conductor width w2 of the connecting portions 22 and 32 is formed to be narrower than the conductor width w1 of the extended portions 21 and 31. Therefore, in the third embodiment as well, similar to the first embodiment, a composite inductor 1 can be provided that is not limited by the size of the base body 2 and allows for easy adjustment of the negative coupling coefficient.

[0069] In particular, in the third embodiment, the bent portions 323 and 333 are widened portions that are wider than the conductor width w1 of the extended portions 21 and 31. With this configuration, the bent portions 323 and 333, acting as widened portions, make it easier to block the magnetic flux Φ2 generated in the connecting portions 22 and 32, which do not contribute to negative coupling but tend to contribute to positive coupling. Therefore, it is easier to relatively increase the influence of the magnetic flux Φ1 generated around the extended portions 21 and 31, and to increase the absolute value of the negative coupling coefficient of the composite inductor 1. In addition, the bent portions 323 and 333, acting as widened portions, make it easier to reduce the DC resistance while adjusting the negative coupling coefficient. In particular, since the electrode forming portions 323d and 333d (see Figure 12) are wide and the mounting terminals are large, the fixing strength is increased and mounting reliability is improved.

[0070] [4. Fourth Embodiment] Next, a fourth embodiment will be described. Note that components similar to those in the first embodiment described above may be denoted by the same reference numerals and their descriptions may be omitted.

[0071] Figure 13 is a side view of the composite inductor 401 according to the fourth embodiment. The composite inductor 401 of the fourth embodiment differs from the first embodiment in that the base body 402 is composed of two ferrite pieces 441 and 444 instead of a magnetic core 40 composed of metallic magnetic particles and resin.

[0072] In this embodiment, the base body 402 includes two ferrite pieces 441 and 444 stacked in the thickness direction DT. The ferrite pieces 441 and 444 are bonded together to form a rectangular parallelepiped.

[0073] A recess 442 is formed on the lower surface of the ferrite piece 441, capable of accommodating the extended portion 21 and the connecting portion 22 of the first coil conductor 20. The recess 442 is recessed upward in the thickness direction DT.

[0074] A recess 443 is formed on the upper surface of the ferrite piece 444, capable of accommodating the extended portion 31 and the connecting portion 32 of the second coil conductor 30. The recess 443 is recessed downward in the thickness direction DT.

[0075] A coil conductor 20 is housed in the recess of ferrite piece 441, and a coil conductor 30 is housed in the recess 443 of ferrite piece 444. The ferrite pieces 441 and 444 are joined together with the coil conductors 20 and 30 sandwiched between them from above and below, thereby forming a composite inductor 401 in which the ferrite pieces 441 and 444 and the pair of coil conductors 20 and 30 are integrated. In the composite inductor 401, the bent portions 23 and 33 are not sandwiched between the ferrite pieces 441 and 444, but are exposed to the outside from the base body 402.

[0076] As described above, in the composite inductor 401 of the fourth embodiment, similar to the first embodiment, the pair of coil conductors 20 and 30 are arranged in the base body 402 such that, when viewed from above, the extended portions 21 and 31 overlap with each other, but the connecting portions 22 and 32 do not overlap. Furthermore, the conductor width w2 of the connecting portions 22 and 32 is formed to be narrower than the conductor width w1 of the extended portions 21 and 31. Therefore, in the fourth embodiment as well, similar to the first embodiment, a composite inductor 401 can be provided that is not restricted by the size of the base body 402 and allows for easy adjustment of the negative coupling coefficient.

[0077] In particular, in the fourth embodiment, the base body 402 includes a plurality of ferrite pieces 441, 444, and a pair of coil conductors 20, 30 are sandwiched between the ferrite pieces 441, 444. With this configuration, in a composite inductor 401 in which a pair of coil conductors 20, 30 are sandwiched by the ferrite pieces 441, 444, the negative coupling coefficient of the composite inductor 401 can be easily adjusted without being restricted by the size of the base body 402. Alternatively, an insulator may be placed between the first coil conductor 20 and the second coil conductor 30 to adjust the negative coupling coefficient. Furthermore, a base body may be formed by combining three or more ferrite pieces.

[0078] [5. Other Embodiments] In the embodiments described above, a configuration was described in which the corners on one end of the extension portion 21, 31 in the extension direction are rounded. However, the shape of both ends of the extension portion 21, 31 in the extension direction is arbitrary as long as the entire extension portion 21, 31 is rectangular or substantially rectangular flat plate. That is, in each coil conductor 20, 30, 220, 230, 320, 330, the portion between the pair of flat plate-shaped extension portions 21, 31 is the connecting portion 22, 32, 222, 232, and the portion from the curved plate-shaped part extending from the other end of the pair of flat plate-shaped extension portions 21, 31 in the extension direction is the bent portion 23, 33, 323, 333.

[0079] In the second embodiment described above, the connecting portions 222 and 232 were formed by compressing the portions that will become the connecting portions 222 and 232, which are formed by punching out a copper plate, in the longitudinal direction DL (direction of the conductor width w2). However, the method of forming the connecting portions 222 and 232 is not limited to this. For example, the portions that will become the connecting portions 222 and 232 may be punched out to be wider than a predetermined conductor width w2, and the wider portions may be folded back and overlapped to form connecting portions 222 and 232 that have the conductor width w2 and a thickness t2.

[0080] In the second embodiment described above, a configuration was described in which connecting portions 222 and 232 having a conductor width w2 and a thickness t2 are formed by plastic deformation. However, the method of forming the connecting portions 222 and 232 is not limited to plastic deformation. For example, copper plates may be formed with different thicknesses, and the portion with a thickness t2 may be punched out to have a conductor width w2, thereby forming connecting portions 222 and 232 having a conductor width w2 and a thickness t2.

[0081] In the third embodiment described above, a configuration was described in which the entire bent portion 323, 333 corresponds to the widened portion. However, for example, a configuration in which only the lead-out portion 323b, 333b serves as the widened portion and has a conductor width w3 that is wider than the conductor width w1 of the extended portion 21, 31.

[0082] In the third embodiment described above, the thickness t2 of the connecting portions 22 and 32 was described as being the same as the thickness t1 of the stretched portions 21 and 31. However, by incorporating the configuration of the second embodiment, the thickness t2 of the connecting portions 22 and 32 may be thicker than the thickness t1 of the stretched portions 21 and 31.

[0083] In the fourth embodiment described above, a configuration was described in which the coil conductors 20 and 30 of the first embodiment are sandwiched between ferrite pieces 441 and 444. However, the coil conductors 220 and 230 of the second embodiment, or the coil conductors 320 and 330 of the third embodiment may be sandwiched between ferrite pieces. Alternatively, a coil conductor having a connecting portion that is thicker than the extended portions 21 and 31, and a bent portion that is wider than the extended portions 21 and 31, may be sandwiched between ferrite pieces.

[0084] All embodiments described above illustrate one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, unless otherwise specified, the directions such as horizontal, orthogonal, and vertical, as well as various numerical values, shapes, and materials in the embodiments described above, include a range that produces the same effect as those directions, numerical values, shapes, and materials (a so-called equivalent range).

[0085] 1...Composite inductor, 2...Basic body, 4...External electrode part, 10...Bottom surface, 12...Top surface, 14...End surface, 16...Side surface, 20...First coil conductor (coil conductor, conductor), 21...Extended part (first conductor part), 22...Transfer part (second conductor part), 23...Bent part (third conductor part), 23a...Bent connection part, 23b...Derivation part, 23c...Bent connection part, 23d...Electrode forming part, 30...Second coil conductor (coil conductor, conductor), 31...Extended part (first conductor part), 32...Transfer part (second conductor part), 33...Bent part (third conductor part), 33a...Bent connection part, 33b...Derivation part, 33c...Bent connection part, 33d...Electrode forming part, 40...Magnetic core (magnetic material), 50...Insulating member, 220...First coil conductor (coil conductor, conductor), 222...Transfer part (second conductor Body, 222a...Transfer section main body, 222b...Transfer section connection, 230...Second coil conductor (coil conductor, conductor), 232...Transfer section (second conductor section), 232a...Transfer section main body, 232b...Transfer section connection, 320...First coil conductor (coil conductor, conductor), 323...Bent section (third conductor section, widening section), 323b...Derivation section, 330...Second coil conductor (coil conductor, conductor), 333...Bent section (third conductor section, widening section), 333b...Extended plate section, 401...Composite inductor, 402...Elemental body, 441...Ferrite piece, 444...Ferrite piece, 442...Recess, 443...Recess, Op...Opening, t1...Thickness, t2...Thickness, t3...Thickness, w1...Conductor width, w2...Conductor width, w3...Conductor width, Φ1...Magnetic flux, Φ2...Magnetic flux.

Claims

1. A composite inductor comprising a base body containing a magnetic material and having an upper surface and a lower surface, and a pair of conductors disposed within the base body, wherein each of the pair of conductors comprises a pair of first conductor portions extending parallel to each other, a second conductor portion extending in a direction perpendicular to the first conductor portions and connecting one end of the first conductor portions between the pair of first conductor portions, and a third conductor portion extending from the other end of the first conductor portions, bent toward the lower surface side of the base body, wherein, in a top view of the base body viewed from the upper surface side, the pair of conductors are arranged within the base body such that the first conductor portions overlap and the second conductor portions do not overlap, and the width of the second conductor portion is formed to be narrower than the width of the first conductor portion.

2. The composite inductor according to claim 1, wherein the thickness of the second conductor portion is greater than the thickness of the first conductor portion.

3. The composite inductor according to claim 2, wherein the cross-sectional area of ​​the first conductor portion and the cross-sectional area of ​​the second conductor portion are equal.

4. The composite inductor according to claim 1, wherein the third conductor portion includes a widened portion that is wider than the width of the first conductor portion.

5. The composite inductor according to any one of claims 1 to 4, wherein the substrate comprises metallic magnetic particles and resin, and the pair of conductors are embedded in the substrate.

6. The composite inductor according to any one of claims 1 to 3, wherein the element comprises a plurality of ferrite pieces, and the pair of conductors are sandwiched between the ferrite pieces.

Images