JP6776793B2 - Coil parts - Google Patents

Description

The present invention relates to a coil component having an air-core coil and a core portion in which the air-core coil is embedded. In particular, it relates to a coil component suitable for being mounted on a power supply system circuit.

In recent years, with the miniaturization and high performance of electronic devices, there has been a demand for small and high-performance coil parts corresponding to high frequencies and high currents in power supply circuits such as DC / DC converters that drive these electronic devices. It's getting stronger.

Conventionally, as a coil component capable of achieving the above requirements, a coil-encapsulated magnetic component in which an air core coil is embedded in a powder magnetic core (core) obtained by pressure-molding a mixture of magnetic powder and resin has been known. (See, for example, Patent Document 1).

In order to obtain a compact and high-performance coil component, it is important to suppress magnetic saturation during power supply drive by obtaining high inductance and maintaining high inductance up to a large current region. In order to achieve miniaturization while suppressing magnetic saturation, it is necessary to effectively utilize the entire magnetic core by making the distribution of the magnetic flux density generated in the magnetic core composed of magnetic materials close to uniform. It becomes important. As an index representing the magnetic saturation characteristic, for example, a DC superimposition characteristic is exemplified.

In Patent Document 1, magnetic saturation is suppressed by defining the relationship between the diameter of the through hole of the coil in the coil component and the distance between the coil and the surface of the exterior portion and defining the relationship between the density of the magnetic material in the magnetic core. Although it is described that it can be done, there is a problem that the suppression of magnetic saturation is actually insufficient.

Japanese Patent No. 3654251

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a coil component capable of suppressing magnetic saturation and having excellent DC superimposition characteristics.

The present inventors have focused on the fact that magnetic flux is densely present at the end of the air-core coil, and the presence of the corners at the end limits the direction in which the magnetic flux passes, and the magnetic flux Was found to be concentrated near the corners. As a result, the distribution of the magnetic flux density inside the core is not uniform, magnetic saturation is likely to occur, and the DC superimposition characteristic is deteriorated.

Therefore, the present inventors have found that by removing the corner portion of the end portion of the air core coil, it is possible to suppress the concentration of magnetic flux in the vicinity of the corner portion and magnetic saturation is less likely to occur, and the present invention is completed. I came to let you.

Aspects of the present invention are
[1] A core portion having a magnetic powder and a resin,
It has an air-core coil portion, a drawer portion drawn from the air-core coil, and a terminal portion.
At least the entire air-core coil part is a coil component embedded inside the core part.
A coil component in which one or more corners of the corners formed by the ends of the cross section are removed from a pair of cross sections of the air core coil portion appearing on the surface including the winding shaft of the air core coil portion. ..

Since the coil component having the above structure can suppress the concentration of magnetic flux in the vicinity of the corner portion, it can exhibit good DC superimposition characteristics.

[2] The average value of the cross-sectional area removed from the corners located on the inner peripheral side of the air-core coil portion is larger than the average value of the cross-sectional area removed from the corners located on the outer peripheral side of the air-core coil portion. Is a coil component according to [1].

The above effect can be further enhanced by removing more corners on the inner peripheral side of the air core coil portion.

[3] The ratio of the cross-sectional area per location of the removed corners to the area of the cross section where the corners have not been removed is 0.11% or more and 5.2% or less [1] or [ 2] is the coil component.

By setting the cross-sectional area ratio of the corners to be removed within the above range, the above effect can be further enhanced.

[4] The removed corner portion is the coil component according to any one of [1] to [3], which has a chamfered shape.

By chamfering, the corners can be easily removed.

FIG. 1A is a perspective perspective view of the coil component according to the first embodiment of the present invention, and FIG. 1B is a perspective plan view of the coil component according to the first embodiment of the present invention. FIG. 2A is a cross-sectional view showing the magnetic flux in the vicinity of the air-core coil in the coil component according to the conventional example, and FIG. 2B is a plan view showing the magnetic flux in the vicinity of one end of the air-core coil. 2 (c) is a plan view showing the magnetic flux in the vicinity of the other end of the air core coil. FIG. 3A is a schematic cross-sectional view showing an air-core coil portion having an R-chamfered corner portion in the coil component according to the first embodiment of the present invention, and FIG. 3B is the present invention. FIG. 5 is a schematic cross-sectional view showing an air-core coil portion having a C-chamfered corner portion in the coil component according to the first embodiment of the present invention. FIG. 4A is a schematic cross-sectional view showing an air-core coil portion having an R-chamfered corner portion in the coil component according to the second embodiment of the present invention, and FIG. 4B is the present invention. FIG. 5 is a schematic cross-sectional view showing an air-core coil portion having a C-chamfered corner portion in the coil component according to the second embodiment of the present invention. FIG. 5A is a schematic cross-sectional view showing an air-core coil portion having an R-chamfered corner portion in the coil component according to the third embodiment of the present invention, and FIG. 5B is the present invention. FIG. 5 is a schematic cross-sectional view showing an air-core coil portion having a C-chamfered corner portion in the coil component according to the third embodiment of the present invention. FIG. 6A is a schematic cross-sectional view showing an air-core coil portion having an R-chamfered corner portion in the coil component according to the fourth embodiment of the present invention, and FIG. 6B is the present invention. FIG. 5 is a schematic cross-sectional view showing an air-core coil portion having a C-chamfered corner portion in the coil component according to the fourth embodiment of the present invention. FIG. 7A is a cross-sectional view of an air-core coil formed by winding a wire having a circular cross-sectional shape a plurality of times, and FIG. 7B is a cross-sectional view of a wire having a rectangular cross-sectional shape. It is sectional drawing of the air core coil configured by winding a plurality of times.

Hereinafter, the present invention will be described in detail in the following order based on the embodiments shown in the drawings.
1. 1. Coil parts 1.1 1st embodiment 1.2 2nd embodiment 1.3 3rd embodiment 1.4 4th embodiment 2. Effect of embodiment 3. Modification example

(1. Coil parts)
As shown in FIGS. 1A and 1B, the coil component 10 according to the first embodiment is drawn out from the core portion 2 as a compression molded body, the air core coil portion 4, and the air core coil portion 4. It has a drawer portion (not shown) and a terminal portion (not shown) that is electrically connected to the drawer portion and is provided on the outer periphery of the core portion 2, and the air core coil portion 4 is inside the core portion 2. It is buried. Therefore, in the actual coil component 10, the air-core coil portion 4 cannot be observed from the outside.

As shown in FIGS. 1 (a) and 1 (b), the outer shape of the core portion 2 is such that the square first main surface 2a and the second main surface 2b have four rectangular outer peripheral surfaces (first outer peripheral surface 2c). , The second outer peripheral surface 2d, the third outer peripheral surface 2e, and the fourth outer peripheral surface 2f) have a regular square columnar structure.

The core portion 2 is formed by compression-molding or injection-molding granules containing a magnetic material powder and a resin as a binder for binding magnetic material particles contained in the magnetic material powder, and performing heat treatment as necessary. is there. The material of the magnetic powder is not particularly limited as long as it exhibits predetermined magnetic properties, but for example, Fe-Si (iron-silicon), sendust (Fe-Si-Al; iron-silicon-aluminum), and the like. Examples thereof include iron-based metal magnetic materials such as Fe-Si-Cr (iron-silicon-chromium), permalloy (Fe-Ni), and carbonyl iron-based materials. Further, it may be a ferrite such as Mn-Zn-based ferrite or Ni-Cu-Zn-based ferrite.

The resin as the binder is not particularly limited, and examples thereof include epoxy resin, phenol resin, acrylic resin, polyester resin, polyimide, polyamide-imide, silicon resin, and a combination thereof.

In the present embodiment, the air-core coil portion 4 is composed of a ring-shaped conductor, in other words, the conductor is wound once. Further, an insulating coating layer is formed on the outer periphery of the conductor, if necessary. Examples of the material of the conductor include Cu, Al, Fe, Ag, Au, phosphor bronze and the like. The insulating coating layer is composed of, for example, polyurethane, polyamide-imide, polyimide, polyester, polyester-imide, polyester-nylon and the like.

Further, at least a pair of drawing portions are pulled out from the air core coil portion to the outside of the core portion. The drawn-out drawer portion is electrically connected to a pair of terminal portions provided on the outer peripheral surface of the core portion. The terminal portion is not particularly limited, and a known configuration can be applied.

In the air-core coil portion, the cross section including the winding shaft and appearing on the surface along the winding shaft direction is usually rectangular. When a current flows through the conductors constituting the air-core coil portion, the generated magnetic fluxes are combined and the magnetic fluxes directed in a predetermined direction are generated. At this time, as shown in FIG. 2A, the magnetic flux MF is generated in the direction of penetrating the hollow portion inside the air core coil portion 4 (hollow portion). At one end E1 of the air-core coil portion 4, the magnetic flux MF is bent in the direction toward the outside of the air-core coil portion 4, and as shown in FIG. 2B, depending on the outer shape of the air-core coil portion 4. Spreads radially. Then, as shown in FIG. 2A, the air core coil portion 4 is directed from one end E1 to the other end E2 along the outer circumference of the air core coil portion 4. At the other end E2 of the air-core coil portion 4, as shown in FIG. 2C, the magnetic flux MF is bent in the direction toward the inside of the air-core coil portion 4, and all directions of the outer circumference of the air-core coil portion 4 Toward the inside of the air core coil portion 4.

Focusing on the ends E1 and E2 of the air-core coil portion 4 in FIG. 2 (a), magnetic fluxes directed toward the outside or inside of the air-core coil portion are densely present near the corners of the ends E1 and E2. doing. The magnetic flux density represents the density of the magnetic flux per unit area perpendicular to the direction of the magnetic field, and since the magnetic permeability of the magnetic material constituting the core portion 2 is almost the same in the core portion, the magnetic flux density at each location in the core portion is , It is affected by the area where the magnetic flux passes. That is, the fact that the magnetic flux is densely present near the corners of the ends E1 and E2 means that the magnetic flux density near the corners of the ends E1 and E2 is locally large, and the distribution of the magnetic flux density is uniform. It shows that it is not. As a result, magnetic saturation cannot be sufficiently suppressed.

Therefore, in the present embodiment, as shown in FIG. 3, by removing the corner portion forming the end portion of the air core coil portion, the magnetic flux density in the vicinity of the corner portion is brought closer to the magnetic flux density in the other portion, and the magnetic flux is generated. We are trying to make the distribution of density uniform.

3A and 3B show a pair of cross sections of the air core coil portion 4 including the winding axis direction O of the air core coil portion 4 and appearing on a plane parallel to the winding shaft O. The configuration in which the corners at the ends of the air core coil portion are removed is shown. In the present embodiment, the cross-sectional shape of the air core coil portion before the corner portion is removed is rectangular.

The method for removing the corners is not particularly limited, but as shown in FIGS. 3A and 3B, it is preferable that the corners have a chamfered shape. FIG. 3A shows a configuration in which the corner portion forming the end portion of the air core coil portion is R-chamfered, and FIG. 3B shows the corner portion forming the end portion of the air core coil portion. Indicates a configuration in which C is chamfered. The R chamfer removes the corners so that the corners are formed of a curved surface having a predetermined radius, and the C chamfer removes the corners at a surface inclined by 45 ° with respect to the surface forming the corners.

In either case, by removing the corner portion, it is possible to suppress the concentration of the magnetic flux in the vicinity of the corner portion and suppress the local increase in the magnetic flux density at the end portion of the air core coil. Therefore, the distribution of the magnetic flux density in the core portion 2 can be made uniform, and good DC superimposition characteristics can be obtained.

Further, in the vicinity of the corners of the ends E1 and E2 of the air core coil portion, the magnetic flux is denser in the vicinity of the corner portion on the inner peripheral side of the air core coil portion than in the vicinity of the corner portion on the outer peripheral side. .. Therefore, regarding the area of the removed corners, the corners located on the inner peripheral side of the air core coil portion are removed from the average value of the areas removed from the corners located on the outer peripheral side of the air core coil portion. It is preferable to increase the average value of the area.

That is, as shown in FIG. 3 (b), the areas removed at the corners on the inner peripheral side are SI ₁ and SI _2, and the areas removed at the corners on the outer circumference are SO ₁ and SO _2. , The average value of the removed areas SI ₁ and SI ₂ on the inner circumference side (SI ₁ + SI ₂ ) / 2 is the average value of the removed areas SO ₁ and SO ₂ on the outer circumference side (SO ₁ + SO). ₂ ) It is preferably larger than / 2. By doing so, the distribution of the magnetic flux density in the vicinity of the end portion of the air core coil portion can be made closer to uniform.

Further, the ratio of the area of the removed corners to each part of the cross section where the corners have not been removed is preferably 0.11% or more, preferably 0.58% or more. Is more preferable. Considering the increase in DC resistance of coil parts and the increase in current density flowing through the air-core coil, the ratio of the area of the removed corners to the area of the cross section where the corners are not removed is It is preferably 5.2% or less.

The area of the cross section in which the corner portion is not removed is the area indicated by the cross section of the air core coil portion when it is assumed that the corner portion of the end portion of the air core coil portion is not removed. In 3 (b), it is the area obtained by adding SI ₁ , SI ₂ , SO ₁ and SO ₂ to the area of the air core coil portion 4.

The coil components according to the present embodiment include, for example, a power supply circuit such as a DC / DC converter mounted on a personal computer or a portable electronic device, a choke coil in a power supply line mounted on a personal computer or a portable electronic device, or the like. It is suitable as a coil component that requires high frequency and high current.

(1.2 Second Embodiment)
As shown in FIGS. 4A and 4B, the coil component 10a according to the second embodiment is the first embodiment except that one of the corners located on the inner peripheral side of the air core coil is removed. It is the same as the coil component 10 of the form, and the overlapping description will be omitted. In the present embodiment, the area SI ₂ removed at the corner on the inner peripheral side is 0, and the areas SO ₁ and SO ₂ removed at the corner on the outer peripheral side are both 0.

FIG. 4A shows a configuration in which the corners are R-chamfered, and FIG. 4B shows a configuration in which the corners are C-chamfered. Since the corners where the magnetic flux is densely present are removed, the coil component 10a according to the present embodiment can have the same effect as the coil component 10 according to the first embodiment.

(1.3 Third Embodiment)
As shown in FIGS. 5A and 5B, in the coil component 10b according to the third embodiment, the first embodiment is performed except that two corners located on the inner peripheral side of the air core coil are removed. It is the same as the coil component 10 of the form, and the overlapping description will be omitted. In the present embodiment, the areas SO ₁ and SO ₂ removed at the corners on the outer peripheral side are both 0.

FIG. 5A shows a configuration in which the corners are R-chamfered, and FIG. 5B shows a configuration in which the corners are C-chamfered. Since the corners where the magnetic flux is densely present are removed, the coil component 10b according to the present embodiment can have the same effect as the coil component 10 according to the first embodiment.

(1.4 Fourth Embodiment)
As shown in FIGS. 6A and 6B, the coil component 10c according to the fourth embodiment has two corners located on the inner peripheral side of the air core coil and one of the corners located on the outer peripheral side. It is the same as the coil component 10 of the first embodiment except that the coil component 10 is removed, and the duplicate description will be omitted. In the present embodiment, the area SO ₂ removed at the corners on the outer peripheral side is 0.

FIG. 6A shows a configuration in which the corners are R-chamfered, and FIG. 6B shows a configuration in which the corners are C-chamfered. Since the corners where the magnetic flux is densely present are removed, the coil component 10c according to the present embodiment can have the same effect as the coil component 10 according to the first embodiment.

(2. Effect of the embodiment)
In the above embodiment, the corners constituting the end of the air core coil are removed. By doing so, the state in which the magnetic flux is densely present in the vicinity of the corner portion can be alleviated, and the distribution of the magnetic flux density in the vicinity of the corner portion can be made uniform.

As a result, saturation magnetization can be effectively suppressed without changing the shape of the coil component, the density distribution of the magnetic material constituting the core portion, or the like.

Further, in the vicinity of the corner portion on the inner peripheral side of the air core coil, the local magnetic flux density increases more than in the vicinity of the corner portion on the outer peripheral side. Therefore, the above-mentioned effect can be obtained by increasing the average value of the area where the corners located on the inner peripheral side are removed from the average value of the area where the corners located on the outer peripheral side of the air core coil are removed. Can be enhanced.

Further, the area of the corner portion to be removed is set to the above range by setting the ratio of the corner portion located at the end of the air core coil to the cross-sectional area of the air core coil when it is assumed that the corner portion is not removed. Saturation magnetization is suppressed, and good DC superimposition characteristics can be exhibited. Further, it is possible to suppress an increase in the DC resistance of the coil component, an increase in the current density flowing through the air-core coil portion, and the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

(3. Modification example)
In the above-described embodiment, the air-core coil is a ring-shaped conductor composed of one turn, but as shown in FIG. 7, the air-core coil has a wire wound at two or more turns. It may be a winding part formed by the above. The wire may be composed of a lead wire and, if necessary, an insulating coating layer covering the outer periphery of the lead wire, as in the above-described embodiment.

In the case of the configuration shown in FIG. 7, for example, the winding method of the wire may be appropriately adjusted so that the corner portion as the winding portion is removed. Therefore, the cross-sectional shape of the wire is not particularly limited, and examples thereof include a circular shape and a flat shape.

FIG. 7A shows a wound portion when the cross-sectional shape of the wire is circular, but it is assumed that the corner portion located at the end of the air core coil portion is not removed. The cross-sectional area of the air-core coil portion and the cross-sectional area of the removed corner portion may be obtained as shown in FIG. 7A. That is, in a pair of cross sections of the air-core coil portion appearing on the surface including the winding shaft of the air-core coil portion, the outer shape formed by the outermost side of the air-core coil portion in contact with the wire is used as a reference. It is sufficient to specify the cross-sectional area of the air-core coil portion and the cross-sectional area of the removed corner portion when it is assumed that the corner portion located at the end portion of the core coil portion is not removed.

FIG. 7B shows a wound portion when the cross-sectional shape of the wire is rectangular. Also in this case, as shown in FIG. 7B, in the pair of cross sections of the air core coil portion appearing on the surface including the winding shaft of the air core coil portion, the wires located on the outermost side of the air core coil portion come into contact with each other. Based on the outer shape composed of the sides, the cross-sectional area of the air core coil portion assuming that the corner portion located at the end of the air core coil portion has not been removed, and the removed corner portion The cross-sectional area may be specified.

(Experimental Example 1)
Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to the following Examples.

A metallic magnetic material powder containing iron as a main component as a magnetic material powder and an epoxy resin as a resin were mixed and granulated into granules. Subsequently, on a copper wire having a rectangular cross section, an insulating film was applied to a copper wire having an insulating film formed after removing corners by performing R chamfering at 1 to 4 points and a copper wire not undergoing R chamfering. The air-core coil produced using the formed insulating film copper wire and the granules obtained by granulation are put into a mold and pressure-molded at a predetermined pressure to embed the air-core coil. A molded body was obtained. These samples were heat-treated under predetermined temperature conditions to obtain coil parts. The size of the coil component produced in Experimental Example 1 was a square shape with a side of 3 mm and a height of 1 mm.

In Experimental Example 1, an air-core coil was produced in which the R-chamfered portion was arranged as follows. That is, in Example 1, there is one place where R chamfering was performed on the inner peripheral side (Example 1a) or the outer peripheral side (Example 1b) of the air core coil, and in Example 2, the place where R chamfering was performed. There are two locations on the inner peripheral side (Example 2a) or the outer peripheral side (Example 2b) of the air core coil, and in Example 3a, there are two locations on the inner peripheral side of the air core coil where R chamfering is performed. There is one place on the side, in Example 3b, there is one place on the inner peripheral side of the air core coil and two places on the outer peripheral side, and in Example 4, the place where R chamfering was performed is the air core. There are two locations on the inner peripheral side of the coil and two locations on the outer peripheral side. In Experimental Example 1, the cross-sectional area of the air-core coil of each example in which the corners were removed was the same as the cross-sectional area of the air-core coil of Comparative Example 1 in which the corners were not removed. Further, in each embodiment, when the cross-sectional area of the air core coil assuming that the corners are not removed is 100%, the cross-sectional area removed is 1.7% per location.

The saturation characteristics of the obtained coil component samples when the initial inductance value and the inductance value were superimposed on DC were evaluated. A DC current was applied using an LCR meter (4284A manufactured by Agilent Technologies) and a DC bias power supply (42841A manufactured by Agilent Technologies) to measure the inductance value.

The initial inductance value was the inductance value when no DC current was applied, and the saturation characteristics of the inductance values when DC was superimposed were the respective inductance values when DC currents of 1.5A and 3.0A were applied.

The larger the initial inductance value, the better the performance as a coil component, and the larger the inductance value at the time of DC superimposition, the higher the inductance value can be maintained up to the large current region, which is an index showing the magnetic saturation characteristics. It is shown that the DC superimposition characteristic is excellent. The results are shown in Table 1.

From Table 1, it was confirmed that in Examples 1 to 4, both the initial inductance value and the saturation characteristics of the inductance values at the time of DC superimposition were better than those in Comparative Example 1.

It was also confirmed that the larger the number of removed corners, the better the saturation characteristics of the initial inductance value and the inductance value when DC is superimposed.

Further, by comparing Example 1a and Example 1b, comparing Example 2a and Example 2b, and comparing Example 3a and Example 3b, the area where the corner portion located on the outer peripheral side was removed. It was confirmed that the saturation characteristics of the initial inductance value and the inductance value at the time of DC superimposition are better when the average value of the removed area of the corners located on the inner peripheral side is larger than the average value of.

(Experimental Example 2)
In Experimental Example 2, coil parts were produced in the same manner as in Experimental Example 1 except that the R chamfered locations were set to two locations on the inner peripheral side of the air core coil and the area per removed location was changed. Then, in addition to the same evaluation as in Experimental Example 1, the DC resistance was measured. The results are shown in Table 2. In Table 2, Example 7 is the same as Example 2a, and Comparative Example 2 is the same as Comparative Example 1. Further, in Table 2, the DC resistance of each sample was evaluated as a relative value with respect to the DC resistance value of Comparative Example 2.

From Table 2, by setting the area per removed location within the above-mentioned range, the saturation characteristics of the initial inductance value and the inductance value at the time of DC superimposition are improved, and the increase in DC resistance can be suppressed. Was confirmed.

10, 10a, 10b, 10c ... Coil parts 2 ... Core part 4 ... Air core coil 4a ... Wire

Claims (2)

A core part having magnetic powder and resin,
It has an air-core coil portion, a drawer portion drawn from the air-core coil, and a terminal portion.
At least the entire air-core coil portion is a coil component embedded inside the core portion.
In a pair of cross sections of the air core coil portion appearing on the surface including the winding shaft of the air core coil portion, among the corner portions formed by the end portions of the cross section, the air core coil portion is located on the inner peripheral side of the air core coil portion. all corners are removed, one or more on the corner portion located on the outer peripheral side of the air-core coil portion has been removed,
The average value of the cross-sectional area removed from the corners located on the inner peripheral side of the air-core coil portion is larger than the average value of the cross-sectional areas removed from the corners located on the outer peripheral side of the air-core coil portion. big,
A coil component in which the ratio of the cross-sectional area of each of the removed corners to the area of the pair of cross sections from which the corners have not been removed is 0.11% or more and 5.2% or less . The coil component according to claim 1, wherein the removed corner portion has a chamfered shape.

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