Coil component and circuit board including the same

Disclosed herein is a coil component that includes a coil conductor part, and first and second high permeability parts provided respectively on both sides of the coil conductor part in a coil axis direction. The second high permeability part has a larger thickness in the coil axis direction than the first high permeability part. A low permeability part that segments at least a part of a magnetic path exists between the first and second high permeability parts in an outer diameter area of the coil conductor part when viewed in the coil axis direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a coil component and a circuit board including the same and, more particularly, to a coil component in which magnetic flux leakage to the outside is reduced and a circuit board including the same.

Description of Related Art

A large number of coil components are used in a mobile electronic device such as a smartphone. Along with miniaturization of the mobile electronic device and improvement in performance thereof, the size required of the coil component has been reduced. However, reduction in the size of the coil component involves reduction in the volume of a magnetic member constituting the coil component, with the result that magnetic flux is more likely to leak outside. In addition, when the mounting density becomes high because of miniaturization of each electronic component, the distance between adjacent electronic components is reduced, so that influence of the leakage magnetic flux becomes more prominent.

For example, a coil component described in Japanese Utility Model Application Publication No. H04-076606 has a configuration in which a coil pattern is formed on a green sheet formed of a ferrite magnetic body. In this coil component, a closed magnetic path is formed by the ferrite magnetic body, and thus comparatively less magnetic flux leaks outside. In addition, the size of the coil component is comparatively large (3.6 mm×1.6 mm), so that the volume of a magnetic member constituting the coil component is sufficiently ensured.

However, in recent years, a coil component is required to have a smaller size, which makes it difficult to sufficiently confine magnetic flux in the coil component. In particular, when a low permeability part that segments a part of the magnetic path exists, a large amount of magnetic flux may leak outside from the low permeability part. As described above, such leakage magnetic flux affects other neighboring electronic components more as the mounting density is increased.

SUMMARY

It is therefore an object of the present invention to provide a small-sized coil component in which magnetic flux leakage to the outside is reduced and a circuit board including the same.

A coil component according to the present invention includes a coil conductor part and first and second high permeability parts provided respectively on both sides of the coil conductor part in the coil axis direction. The second high permeability part has a larger thickness in the coil axis direction than the first high permeability part. A low permeability part that segments at least a part of a magnetic path exists between the first and second high permeability parts in the outer diameter area of the coil conductor part when viewed in the coil axis direction.

According to the present invention, the second high permeability part has a larger thickness than the first high permeability part, so that using a surface of the first high permeability part perpendicular to the coil axis as the mounting surface allows spread of magnetic flux leaking from the low permeability part to be suppressed by the second high permeability part.

In the present invention, the low permeability part may be a non-magnetic substrate, and the coil conductor part may be formed on the surface of the non-magnetic substrate. The first or second high permeability part may be a magnetic substrate, the coil conductor part may be formed on the surface of the magnetic substrate, and the low permeability part may be an insulating resin layer that covers the coil conductor part. Further, the first high permeability part may be one of flange parts of a drum-shaped core, and the second high permeability part may be the other one of the flange parts of the drum-shaped core.

A circuit board according to the present invention includes a mounting substrate and the coil component mounted on the mounting substrate such that the mounting surface thereof faces the mounting substrate.

According to the present invention, leakage magnetic flux from the coil component is reduced, enabling high density mounting on the mounting substrate.

In the present invention, the mounting substrate preferably has a ground pattern formed so as to overlap the coil component. With this configuration, leakage magnetic flux to the first high permeability part is shielded by the ground pattern, allowing further reduction in influence that the leakage magnetic flux has on other electronic components.

As described above, according to the present invention, there can be provided a small-sized coil component in which magnetic flux leakage to the outside is reduced and a circuit board having the same, thereby allowing reduction in influence that the leakage magnetic flux has on other electronic components, which in turn enables higher density mounting.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be explained in detail with reference to the drawings.

FIG. 1is a schematic perspective view illustrating the outer shape of a coil component1according to the first embodiment of the present invention.

As illustrated inFIG. 1, the coil component1according to the present embodiment is a surface-mount type chip component and has a coil layer10and first and second magnetic layers21and22provided on both sides of the coil layer10in the illustrated z-direction. The coil component1has a substantially rectangular parallelepiped outer shape, and first and second terminal electrodes31and32are provided on both sides thereof in the illustrated y-direction. The first and second terminal electrodes31and32are formed not only on the illustrated xz plane, but also on the xy and yz planes. Particularly, on the xy plane, the first and second terminal electrodes31and32are formed on both the xy plane constituted by the first magnetic layer21and xy plane constituted by the second magnetic layer22. In the coil component1according to the present embodiment, the xy plane on the first magnetic layer21side is used as a mounting surface. The first and second terminal electrodes31and32can be formed by, e.g., a dipping method.

The coil layer10has a substrate11and first and second insulating resin layers12and13sandwiching the substrate11in the z-direction. A coil conductor part to be described later is formed on the both sides of the substrate11. The substrate11and the insulating resin layers12and13are each formed of a non-magnetic material and constitute a low permeability part.

The first and second magnetic layers21and22are each a magnetic substrate that constitutes a high permeability part. The high permeability part is a part that is formed of a material having higher permeability than the above low permeability part. As a material for the first and second magnetic layers21and22, a bulk magnetic material such as ferrite, or a metal magnetic powder-containing resin material obtained by mixing metal magnetic powder in resin can be used. The first and second magnetic layers21and22may be formed of the same material or mutually different materials but need to be each formed of a material having high permeability than materials constituting at least the substrate11and insulating resin layers12and13, respectively. When the metal magnetic powder-containing resin material is used as the material of each of the first and second magnetic layers21and22, a permalloy-based material is preferably used as the metal magnetic powder, and liquid or powder epoxy resin is preferably used as the resin.

As illustrated inFIG. 1, a thickness T2of the second magnetic layer22in the z-direction is larger than a thickness T1of the first magnetic layer21in the z-direction. Accordingly, the coil layer10is disposed offset to the mounting surface side.

FIG. 2is a schematic exploded perspective view of the coil component1. InFIG. 2, the first and second terminals31and32are omitted.

As illustrated inFIG. 2, the substrate11has an upper surface11aand a lower surface11b. A first spiral conductor41and a first electrode pattern43are formed on the upper surface11aof the substrate11, and a second spiral conductor42and a second electrode pattern44are formed on the lower surface11b. The first and second spiral conductors41and42constitute a coil conductor part40. The coil axis of the coil conductor part40extends in the z-direction.

The substrate11has a substantially rectangular shape when viewed in the z-direction and has two side surfaces11cand11dextending in the x-direction and two side surfaces11eand11fextending in the y-direction. The substrate11has through holes11gand11hformed therein and has, at its four corners, four quarter-round shaped cutout parts11iobtained by chamfering the four corners.

The first spiral conductor41is formed on the upper surface11aof the substrate11, and the second spiral conductor42is formed on the lower surface11bof the substrate11. The inner peripheral ends of the first and second spiral conductors41and42are located at the same position when viewed from the z-direction and are connected to each other through a through hole conductor19penetrating through the through hole11h. The outer peripheral ends of the first and second spiral conductors41and42are located at the opposite positions with the main parts thereof interposed therebetween. Specifically, the outer peripheral ends of the first spiral conductor41is located near the side surface11cof the substrate11, and the outer peripheral ends of the second spiral conductor42is located near the side surface11dof the substrate11.

The first and second spiral conductors41and42are wound in the opposite directions. That is, when viewed from the upper surface11aside of the substrate11, the first spiral conductor41is wound counterclockwise (left-handed) from the inner peripheral end thereof to the outer peripheral end, while the second spiral conductor42is wound clockwise (right-handed) from the inner peripheral end thereof to the outer peripheral end. With this winding structure, when current is made to flow from one of the outer peripheral ends of the first and second spiral conductors41and42to the other one of them, the current flowing in the first and second spiral conductors41and42generates magnetic fields of the same direction to intensify them. Thus, the coil conductor part40constituted of the first and second spiral conductors41and42functions as a single inductor.

The first electrode pattern43is formed on the upper surface11aof the substrate11and connected to the outer peripheral end of the first spiral conductor41. The first electrode pattern43is located outside the outermost peripheral turn of the first spiral conductor41, and the xz plane thereof is connected to the first terminal electrode31illustrated inFIG. 1. The second electrode pattern44is formed on the lower surface11bof the substrate11and connected to the outer peripheral end of the second spiral conductor42. The second electrode pattern44is located outside the outermost peripheral turn of the second spiral conductor42, and the xz plane thereof is connected to the second terminal electrode32illustrated inFIG. 1.

The first and second spiral conductors41and42and the first and second electrode patterns43and44are formed at the same time through a process of forming a base conductor layer by electroless plating and then an electrolytic plating. Both a material of the base conductor layer and a plating material used in the electrolytic plating are preferably copper (Cu).

The first spiral conductor41and first electrode pattern43formed on the upper surface11aof the substrate11are covered by the insulating resin layer12. The second spiral conductor42and second electrode pattern44formed on the lower surface11bof the substrate11are covered by the insulating resin layer13. The insulating resin layers12and13prevent electrical conduction between the conductor patterns on the substrate11and the first and second magnetic layers21and22and function as an adhesive layer therebetween.

As illustrated inFIG. 2, the through hole11gis formed at the center of the substrate11, and the quarter-round shaped cutout parts11iare formed at the four corners of the substrate11. The insulating resin layers12and13each also have a through hole and cutout parts at positions overlapping the through hole11gand the cutout parts11iin a plan view. A magnetic member24is disposed corresponding to the through hole11gand magnetic members25are disposed corresponding to the respective cutout parts11i. Thus, the first and second magnetic layers21and22are magnetically connected to each other through the magnetic members24and25, whereby a closed magnetic path structure can be obtained. As a material for the magnetic members24and25, a metal magnetic powder-containing resin material is preferably used.

The magnetic member24constitutes a magnetic path in the inner diameter area of the coil conductor part40, and the magnetic members25constitute a magnetic path in the outer diameter area of the coil conductor part40. The inner diameter area refers to an area surrounded by the coil conductor part40when viewed in the coil axis direction (z-direction), and the outer diameter area refers to an area outside the coil conductor part40when viewed in the coil axis direction (z-direction). As illustrated inFIG. 2, the magnetic member25is partially disposed at four positions outside the coil conductor part40, and in portions where the magnetic member25does not exist, the magnetic path is segmented by the substrate11and the insulating resin layers12and13. In the portions where the magnetic member25does not exist, the substrate11and the insulating resin layers12and13are exposed outside, so that leakage of magnetic flux to the outside is prominent.

FIG. 3is a schematic cross-sectional view of a circuit board on which the coil component1is mounted.

The circuit board illustrated inFIG. 3has a mounting substrate5and the coil component1mounted on the mounting substrate5. The coil component1is mounted on the mounting substrate5such that the xy plane of the first magnetic layer21serving as the mounting surface faces the mounting substrate5. Land patterns6and7are provided on the surface of the mounting substrate5. The land patterns6and7and the first and second terminal electrodes31and32are electrically and mechanically connected to each other through solder fillets F, respectively.

A ground pattern8is provided on the back surface of the mounting substrate5. The ground pattern8is provided so as to overlap the coil component1when viewed in the z-direction. The ground pattern8plays a role of providing a reference level of a differential signal and shielding magnetic flux leaking from the coil component1to the mounting substrate5side.

As described above, the ground pattern8that shields leakage magnetic flux is provided on the mounting substrate5, so that the lower side (negative side in the z-direction) relative to the coil component1is less influenced by the leakage magnetic flux. On the other hand, the upper side (positive side in the z-direction) relative to the coil component1is made to be an open space where such a magnetic shielding member is not provided and thus tends to be much influenced by the leakage magnetic flux. However, in the coil component1according to the present embodiment, the thickness T2of the second magnetic layer22located on the side opposite to the mounting substrate5when viewed from the coil layer10is larger than the thickness T1of the magnetic layer21, so that the magnetic path on the upper side of the coil layer10is expanded. This makes it possible to reduce leakage magnetic flux to the upper side relative to the coil component1.

Further, in addition to an increase in the thickness T2of the second magnetic layer22, the position of the coil layer10is offset in the z-direction to reduce the thickness T1of the first magnetic layer21, thereby making it possible to minimize increase in the dimension of the coil component1in the z-direction.

As described above, in the coil component1according to the present embodiment, the coil layer10is offset in the z-direction, so that when the first magnetic layer21having a smaller thickness is used as the mounting side, it is possible to suppress magnetic flux from leaking upward by the second magnetic layer22having a larger thickness.

FIG. 4is a cross-sectional view for explaining the structure of a coil component2according to the second embodiment of the present invention.

As illustrated inFIG. 4, the coil component2according to the present embodiment has a configuration in which the coil layer10is arranged on the surface of the first magnetic layer21in a stacked manner. Specifically, insulating resin layers51to53are stacked in this order on the surface of the first magnetic layer21, a spiral conductor42is formed between the insulating resin layers51and52, and a spiral conductor41is formed between the insulating resin layers52and53. Other configurations are basically the same as those in the coil component1according to the first embodiment, so the same reference numerals are given to the same elements, and overlapping description will be omitted.

In the manufacturing process of the coil component2, first, the first magnetic layer21is prepared, and then the insulating resin layer51is formed on the surface of the first magnetic layer21using a spin-coating method, etc., followed by formation of the spiral conductor42on the surface of the insulating resin layer51. Subsequently, the surface of the spiral conductor42is covered with the insulating resin layer52using a spin-coating method, etc., followed by formation of the spiral conductor41on the surface of the insulating resin layer52. Then, the surface of the spiral conductor41is covered with the insulating resin layer53using a spin-coating method, etc., followed by bonding of the second magnetic layer22and formation of the first and second terminal electrodes31and32, whereby the coil component2according to the present embodiment is completed.

As exemplified in the present embodiment, the coil component according to the present invention may not necessarily have the substrate11, but instead may have a configuration in which the coil layer10is formed on the surface of the first magnetic layer21in a stacked manner. In this case, the insulating resin layers51to53constitute the low permeability part.

FIG. 5is a cross-sectional view for explaining the structure of a coil component3according to the third embodiment of the present invention.

As illustrated inFIG. 5, the coil component3according to the present embodiment has a configuration in which the coil layer10is arranged on the surface of the second magnetic layer22in a stacked manner. Specifically, insulating resin layers61to63are stacked in this order on the surface of the second magnetic layer22, a spiral conductor41is formed between the insulating resin layers61and62, and a spiral conductor42is formed between the insulating resin layers62and63. Other configurations are basically the same as those in the coil component2according to the second embodiment, so the same reference numerals are given to the same elements, and overlapping description will be omitted.

In the manufacturing process of the coil component3, first the second magnetic layer22is prepared, and then the insulating resin layer61is formed on the surface of the second magnetic layer22using a spin-coating method, etc., followed by formation of the spiral conductor41on the surface of the insulating resin layer61. Subsequently, the surface of the spiral conductor41is covered with the insulating resin layer62using a spin-coating method, etc., followed by formation of the spiral conductor42on the surface of the insulating resin layer62. Then, the surface of the spiral conductor42is covered with the insulating resin layer63using a spin-coating method, etc., followed by bonding of the first magnetic layer21and formation of the first and second terminal electrodes31and32, whereby the coil component3according to the present embodiment is completed.

As exemplified in the second and third embodiments, when the coil layer10is formed by a stacking method, the stacking may be started from either the first magnetic layer21side or second magnetic layer22side. When the stacking of the coil layer10is started from the second magnetic layer22side as in the third embodiment, the vertical direction at the time of mounting is reversed to the vertical direction at the time of stacking. In the present embodiment, the insulating resin layers61to63constitute the low permeability part.

FIG. 6is a cross-sectional view for explaining the structure of a coil component4according to the fourth embodiment of the present invention.

As illustrated inFIG. 6, the coil component4according to the present embodiment has a configuration in which a wire W is wound around a drum-shaped core70. The drum-shaped core70has a pair of flange parts71and72and a winding core part73connecting the flange parts71and72. The wire W is wound around the winding core part73. One end of the wire W is connected to a first terminal electrode81provided on the flange part71, and the other end thereof is connected to a second terminal electrode82provided on the flange part71. In the present embodiment, the wire W wound around the winding core part73constitutes the coil conductor part.

The coil component4according to the present embodiment is mounted on the mounting substrate5in an upright posture with the flange part71as the mounting surface. In a state where the coil component4is mounted on the mounting substrate5, the terminal electrodes81and82are connected to the land patterns6and7, respectively. A thickness T2of the flange part72of the coil component4in the coil axis direction is larger than a thickness T1of the flange part71in the coil axis direction, so that, as in the above embodiments, it is possible to suppress magnetic flux from leaking upward by the flange part72having a larger thickness. In the present embodiment, the flange parts71and72constitute the high permeability part, and a space S located outside the coil conductor part constituted of the wire W and sandwiched between the flange parts71and72constitutes the low permeability part.

As exemplified in the present embodiment, the coil component according to the present invention may be a coil component of a type that uses the drum-shaped core and wire. Further, a space may constitute the low permeability part.

EXAMPLES

A magnet field distribution generated when current is made to flow in the coil conductor part40was simulated by using the coil component1described usingFIGS. 1 to 3. The size of the coil component1is set such that x=1.6 mm, y=2.0 mm, and z=1.0 mm, the thickness of the substrate11is set to 75 μm, and the dimensions of the spiral conductors41and42in the z-direction are set to 220 μm. Further, the position of the substrate11in the z-direction is set to a position at a ratio of 4:5 in terms of the dimension of the coil component1in the z-direction. That is, the substrate11is offset in the z-direction such that the relationship between the distance from the center of the substrate11to the xy plane of the first magnetic layer21and distance from the center of the substrate11to the xy plane of the second magnetic layer22is set to a ratio of 4:5.

The results of the simulation are illustrated inFIG. 7.

As illustrated inFIG. 7, it can be confirmed that leakage magnetic flux ϕ to the outside is less at the second magnetic layer22side than at the first magnetic layer21side. Further, spread of the leakage magnetic flux ϕ in the side surface direction (xy direction) is less than spread of the magnetic flux leaking from the mounting surface.