Patent Application
20250111983
The present application claims a priority to Japanese patent application No. 2023-170025 filed on Sep. 29, 2023, which is incorporated herein by reference in its entirety.
The present disclosure relates to a coil component and a power supply apparatus.
Patent Document 1 discloses that improving uniformity of the inside of a molded body in which composite magnetic particles are pressure-molded improves DC superimposition characteristics of a reactor including the molded body as a core.
A coil component according to one aspect of the present disclosure is
A power supply apparatus according to one aspect of the present disclosure includes the above coil component.
One embodiment of the present disclosure is described below with reference to the drawings. The following embodiment of the present disclosure is an exemplification illustrative of the present disclosure. Various elements, such as numerical values, shapes, materials, and manufacturing steps, according to the embodiment of the present disclosure can be modified or changed to the extent that technical problems do not arise.
Shapes and the like illustrated in the drawings of the present disclosure do not necessarily match actual shapes and the like, because the former may be modified for illustration purposes.
An upper surface and a lower surface of the core portion 6 of the inductor 2 according to the one embodiment of the present disclosure are perpendicular to the Z-axis. Side surfaces of the core portion 6 are perpendicular to a plane containing the X-axis and the Y-axis. A winding axis of the winding portion 4 is parallel to the Z-axis. However, the core portion 6 may have any other shapes other than the shape shown in
In the present disclosure, “parallel” denotes not only a complete parallel state but also a substantially parallel state. That is, in some embodiments of the present disclosure, “parallel” denotes a state with variation within manufacturing tolerance. In some embodiments of the present disclosure, “parallel” denotes a state with variation exceeding the manufacturing tolerance. Specifically, a line A being parallel to a line B denotes that an angle formed by the lines A and B is 0° or more and 10° or less unless otherwise specified. The same applies to a situation where either one of the lines is or both of the lines are replaced with a plane or planes.
In the present disclosure, “perpendicular” denotes not only a complete perpendicular state but also a substantially perpendicular state. That is, in some embodiments of the present disclosure, “perpendicular” denotes a state with variation within manufacturing tolerance. In some embodiments of the present disclosure, “perpendicular” denotes a state with variation exceeding the manufacturing tolerance. Specifically, a line A being perpendicular to a line B denotes that an angle formed by the lines A and B is 80° or more and 100° or less unless otherwise specified. The same applies to a situation where either one of the lines is or both of the lines are replaced with a plane or planes.
The inductor 2 according to the embodiment of the present disclosure may have any size. In some embodiments, the inductor 2 has a size of a rectangular parallelepiped having a bottom surface measuring 2 mm×2 mm and a height of 1 mm as lower size limits of portions other than portions not shown in the drawings (e.g., lead portions or terminals described later). In some embodiments, the inductor 2 has a size of a cube having a bottom surface measuring 25 mm×25 mm and a height of 25 mm as upper size limits of the portions other than the portions not shown in the drawings. The height denotes a length in the Z-axis direction in
The conductor (conductive wire) 5 constituting the winding portion 4 is covered, at its periphery, with an insulating coating as necessary. The conductor 5 may be made from any material. In some embodiments, the conductor 5 is made from, for example, Cu, Al, Fe, Ag, Au, or an alloy containing some of these metals. The insulating coating may be made from any material. In some embodiments, examples of materials of the insulating coating include polyurethane, polyamide-imide, polyimide, polyester, polyester-imide, and/or polyester-nylon.
The conductor 5 may have any cross-sectional shape. Examples of cross-sectional shapes include a circular shape and a rectangular shape. In the embodiment of the present disclosure, the conductor 5 has a circular cross-sectional shape.
The core portion 6 includes at least soft magnetic metal particles. The soft magnetic metal particles may be made from any material. In some embodiments, examples of materials of the soft magnetic metal particles include ferrites (e.g., Mn—Zn ferrites and Ni—Cu—Zn ferrites) and soft magnetic alloys (e.g., Fe—Si alloys, Fe—Si—Al alloys, Fe—Si—Cr alloys, and permalloys (Fe—Ni alloys)). The soft magnetic metal particles may have any microstructure. In some embodiments, the microstructure of the soft magnetic metal particles is amorphous. In some embodiments, the microstructure of the soft magnetic metal particles includes crystals. In some embodiments, in a situation where the soft magnetic metal particles are amorphous, the soft magnetic metal particles are flattened in advance with a pulverizer or the like. In a situation where the soft magnetic metal particles include crystals, the crystals may have any crystal grain size. In some embodiments, the crystal grain size is, for example, 1 μm or less.
In some embodiments, the soft magnetic metal particles include Fe based soft magnetic particles, i.e., soft magnetic particles having an Fe content of 90 at % or more.
The soft magnetic metal particles in the core portion 6 may have any average particle size. In some embodiments, the soft magnetic metal particles observed in a section of the core portion 6 using a SEM have an average equivalent circle diameter of 1 μm or more and 100 μm or less. An equivalent circle diameter of a particle is a diameter of a circle having the same area as the particle. Hereinafter, an equivalent circle diameter of a particle in a section may simply be referred to as a particle size.
The soft magnetic metal particles include specific particles having a particle size of 10 μm or more and 50 μm or less. The specific particles may account for any percentage of the soft magnetic metal particles in the core portion 6. In some embodiments, the total area of the specific particles accounts for 50% or more of the total area of the soft magnetic metal particles in a section of the core portion 6.
In some embodiments, the core portion 6 includes a thermosetting resin (binder). The thermosetting resin may be of any type. Examples of thermosetting resins include an epoxy resin, a diallyl phthalate resin, a phenol resin, polyimide, polyamide-imide, a silicone resin, and a combination of some of these. In some embodiments, the core portion 6 includes an epoxy resin as the thermosetting resin.
The winding portion 4 includes an inner circumferential surface 4β1, an outer circumferential surface 4β4, and a first end surface 4β2 and a second end surface 4β3 opposite each other along the axial centerline 4a.
As shown in
The core portion 6 may have any density. In some embodiments, the density is, for example, 5.00 g/cm3 or more and 7.00 g/cm3 or less.
In some embodiments, the axially central region 6α has a density higher than that of the peripheral region 6γ. With the density of the axially central region 6α being higher than the density of the peripheral region 6γ, the inductor 2 readily has improved DC superimposition characteristics.
As shown in
In some embodiments, 0<D1/D2<1.00 is satisfied, where D1 denotes an average inter-particle distance between the specific particles in the axially central region 6α and D2 denotes an average inter-particle distance between the specific particles in the coil corner neighboring region 6β5. In some embodiments, 0.01≤D1/D2≤0.99 is satisfied. In some embodiments, 0.19≤D1/D2≤0.70 is satisfied. In some embodiments, 0.19≤D1/D2≤0.66 is satisfied.
With D1/D2 being within the above range, the inductor 2 has high inductance and high DC superimposition characteristics. In a situation where D1/D2 is too high, particularly the DC superimposition characteristics are readily reduced.
In some embodiments, 0.20≤R1/R2≤5.00 is satisfied, where R1 denotes an average particle size of the specific particles in the axially central region 6α and R2 denotes an average particle size of the specific particles in the coil corner neighboring region 6β5. In some embodiments, 0.50≤R1/R2≤2.00 is satisfied. In some embodiments, 0.53≤R1/R2≤1.84 is satisfied.
With R1/R2 being within the above range, the inductor 2 readily has improved DC superimposition characteristics even if the difference between the density of the axially central region 6α and the density of the peripheral region 6γ is small (e.g., 0.20 g/cm3 or less).
Methods of measuring R1, R2, D1, and D2 are described below.
First, as shown in
Then, the specific particles included in each region are identified. Any method of identifying the specific particles may be used. In some embodiments, the specific particles are identified visually. In some embodiments, the specific particles are identified using image analysis software.
In the axially central region 6α, particles that have a particle size of 10 μm or more and 50 μm or less and are included in the axially central region 6α in their entirety are defined as the specific particles. By contrast, in the coil corner neighboring region 6β5, particles that have a particle size of 10 μm or more and 50 μm or less and are at least partly included in the coil corner neighboring region 6β5 are defined as the specific particles.
In each region, an inter-particle distance between adjacent specific particles is measured. First, a line is drawn between surfaces of these different specific particles so that the line has a shortest length. The length of this line is the inter-particle distance between these adjacent specific particles.
The “adjacent specific particles” denote those whose line does not overlap any other soft magnetic metal particle having a particle size of 10 μm or more when the line is drawn.
In each region, all adjacent specific particles are identified, and their inter-particle distances are measured. Then, the measured inter-particle distances are averaged to calculate D1 or D2.
In some embodiments, the coil corner neighboring region 6β5 includes two coil corner neighboring regions 6β5 facing each other with respect to the axial centerline 4α. In some embodiments, in such a situation, 0<D1/D2<1.00 is satisfied in both of the two coil corner neighboring regions 6β5. The inductor 2 readily has improved DC superimposition characteristics.
In some embodiments, the coil corner neighboring region 6β5 includes four coil corner neighboring regions 6β5. In some embodiments, in such a situation, 0<D1/D2<1.00 is satisfied in all of the four coil corner neighboring regions 6β5. The inductor 2 readily has improved DC superimposition characteristics.
In particular, in a situation where the core portion 6 including a thermocompression-bonded soft magnetic metal powder is prepared to manufacture the inductor 2 having the shape shown in
Thus, to improve both inductance and DC superimposition characteristics of the inductor 2 as a whole, preferred is locally reducing permeability of the coil corner neighboring region 6β5 to less readily cause magnetic saturation. Thus, in this region, the inter-particle distances between the soft magnetic metal particles are preferably large.
By contrast, in a core central portion including the axially central region 6α, a magnetic path is preferably as short as possible so that a magnetic flux flows straight. Thus, preferred is locally increasing permeability of the core central portion. Thus, in the core central portion, the inter-particle distances between the soft magnetic metal particles are preferably small.
Thus, by satisfying 0<D1/D2<1.00 in the coil corner neighboring region 6β5, the inductor 2 readily has improved inductance and improved DC superimposition characteristics.
The particle sizes of all specific particles included in each region are measured. The measured particle sizes are averaged to calculate R1 or R2.
Methods of manufacturing the inductor 2 shown in
As shown in
As materials of the preliminary compact bodies 60a and 60b, a resin and a soft magnetic metal powder including soft magnetic metal particles are prepared.
The soft magnetic metal particles included in the soft magnetic metal powder may have any shapes. In some embodiments, the soft magnetic metal particles have, for example, a spherical shape. In some embodiments, the soft magnetic metal particles have a flat shape. In some embodiments, the soft magnetic metal particles have a needle-like shape.
In some embodiments, preparation of the preliminary compact bodies involves use of one soft magnetic metal powder. In some embodiments, two or more soft magnetic metal powders having different shapes, different average particle sizes, different compositions, or the like are mixed. In a situation where one soft magnetic metal powder is used, the soft magnetic metal powder may have any average particle size. In some embodiments, the average particle size is, for example, 1 μm or more and 100 μm or less. The average particle size is not limited as long as the powder includes many soft magnetic metal particles that have a particle size of 10 μm or more and 50 μm or less and readily become the specific particles.
In a situation where two or more soft magnetic metal powders are mixed for use, the soft magnetic metal powders may have any average particle sizes. In some embodiments, for example, a soft magnetic metal powder that is mainly to be the specific particles and has an average particle size of 10 μm or more and 50 μm or less and a soft magnetic metal powder that is mainly to be particles smaller than the specific particles and has an average particle size of 1 μm or more and less than 10 μm are mixed for use.
The resin may be of any type. Examples of resins include an epoxy resin, a phenol resin, a polyimide resin, a polyamide-imide resin, and a silicone resin. In some embodiments, a resin in which some of these resins are appropriately combined is prepared.
Next, the soft magnetic metal powder or powders and the resin are mixed and are granulated into granules. Any method of granulation may be used. In some embodiments, for example, the resin is added to the soft magnetic metal powder or powders, and the mixture is stirred and then dried. In some embodiments, an average size of the granules or granule size distribution is appropriately controlled.
The proportion of the resin is not limited. In some embodiments, the resin weighs, for example, 1.0 to 6.0 parts by weight with respect to 100 parts by weight of the soft magnetic metal powder or powders.
In some embodiments, before the soft magnetic metal powder or powders is or are mixed with the resin, an insulating film is provided on surfaces of the soft magnetic metal particles. In some embodiments, for example, a sol gel method is used to provide the insulating film, which is a SiO2 film.
In some embodiments, after addition of the resin to the soft magnetic metal powder or powders and stirring, the stirred mixture is sieved with a mesh to remove coarse granules. In some embodiments, the resin is diluted with a solvent when added to the soft magnetic metal powder or powders. As the solvent, for example, ketone is used.
Next, compression molding is carried out to prepare the preliminary compact bodies 60a and 60b. Specifically, a mold is filled with the resulting granules, and pressure is applied, to give the preliminary compact bodies 60a and 60b. The preliminary compact bodies 60a and 60b prepared by compression molding are compact bodies including the soft magnetic metal particles and the resin.
The pressure applied is not limited. The higher the pressure, the larger and flatter the soft magnetic metal particles tend to be. In some embodiments, the pressure is, for example, 400 MPa to 1000 MPa.
In the manufacturing method 1, the preliminary compact body 60a has a pot-type shape as shown in
First, the preliminary compact body 60a is inserted into a mold. Then, as shown in
Then, thermocompression bonding is carried out. Specifically, after the preliminary compact bodies 60a and 60b inserted into the mold are heated to a temperature at which the resin softens, the preliminary compact bodies 60a and 60b and the insert member 40a are thermocompression-bonded. In some embodiments, the preliminary compact bodies 60a and 60b, the insert member 40a, etc. are heated (preheated) in advance. In some embodiments, the frame, punch, or the like of the mold are heated. The direction in which pressure is applied is the winding axis direction of the coil. By pressing, the winding portion 4 and the core portion 6 are thermocompression-bonded for integration. The preliminary compact bodies 60a and 60b are deformed by thermocompression bonding, and spaces shown in
By thermocompression bonding, the preliminary compact bodies 60a and 60b are integrated to give the core portion 6.
In some embodiments, the inductor 2 taken out from the mold after thermocompression bonding is heated to further cure the resin. The heating temperature at this time is not limited. In some embodiments, the heating temperature is, for example, 150° C. to 200° C.
In a situation where the inductor 2 shown in
Usually, the higher the density of the soft magnetic metal powder, the better the permeability of the core portion 6 of the inductor 2. Thus, the core portion 6 in its entirety preferably has a high density. Thus, to increase permeability, it is assumed that the preliminary compact body 60a having the pot-type shape and the preliminary compact body 60b having the RT-type shape are preferably combined without any spaces therebetween when the preliminary compact bodies 60a and 60b and the insert member 40a are combined.
In some embodiments, in the manufacturing method 1 of manufacturing the inductor 2 according to the one embodiment of the present disclosure, the preliminary compact body 60b having the RT-type shape is tapered at its extremity, i.e., a portion that is eventually located near the coil corner neighboring region 6β5. Tapering provides a space at the portion that is located near the coil corner neighboring region 6β5 when the preliminary compact bodies 60a and 60b and the insert member 40a are combined.
In a situation where the preliminary compact bodies including the soft magnetic metal particles and the resin are thermocompression-bonded, the resin exudes at a joint. In a situation where the extremity of the preliminary compact body 60b is tapered as described above, much of the resin exudes from the preliminary compact bodies 60a and 60b into the space provided by tapering. By contrast, the amount of the soft magnetic metal particles that move into this space from the preliminary compact bodies 60a and 60b is relatively small. Thus, at the space provided by tapering and its vicinity, the density of the soft magnetic metal particles is reduced, and the average inter-particle distance between the specific particles is increased. That is, at two coil corner neighboring regions 6β5 being within the predetermined range from two coil corners 4β5 where the inner circumferential surface 4β1 and the second end surface 4β3 meet in a section of the inductor 2, D2 is increased.
By contrast, the average inter-particle distance between the specific particles in the axially central region 6α almost does not vary according to presence or absence of the tapering. Thus, D1 almost does not vary according to presence or absence of the tapering.
Thus, providing the tapering can reduce D1/D2 of the two coil corner neighboring regions 6β5 being within the predetermined range from the two coil corners 4β5 where the inner circumferential surface 4β1 and the second end surface 4β3 meet in a section of the inductor 2 to less than 1.00. That is, in both two coil corner neighboring regions 6β5 facing each other with respect to the axial centerline 4a, 0<D1/D2<1.00 can be satisfied.
In addition to tapering, changing various conditions or the like of, in particular, thermocompression bonding can control D1/D2.
Controlling the temperature of thermocompression bonding can control D1/D2. As the temperature of thermocompression bonding is increased, the resin softens, and the amount of the resin exuding into the space increases. Consequently, D2 is further increased, which readily reduces D1/D2. Conversely, reducing the temperature of thermocompression bonding makes the resin harder, reducing the amount of the resin exuding into the space. By contrast, easiness of the soft magnetic metal particles to move into the space does not readily change. Consequently, even when the tapering is provided, D2 is not readily increased, and D1/D2 is less readily reduced.
Selecting a soft resin as the resin also allows the tapering to readily reduce D1/D2. Conversely, if a hard resin is selected as the resin, D1/D2 is less readily reduced regardless of the tapering being provided.
It is also possible to control D1/D2 by controlling the particle sizes of the soft magnetic metal particles included in the preliminary compact body 60a having the pot-type shape and/or the particle sizes of the soft magnetic metal particles included in the preliminary compact body 60b having the RT-type shape. Relatively reducing the particle sizes of the specific particles included in the preliminary compact body 60b having the RT-type shape readily reduces D1/D2.
Relatively reducing the particle sizes of the soft magnetic metal particles included in the preliminary compact body 60b having the RT-type shape reduces the particle sizes of the soft magnetic metal particles included in the axially central region 6α, reducing D1. By contrast, the soft magnetic metal particles from both of the preliminary compact bodies 60a and 60b μmove into the space provided by tapering. Thus, even when the particle sizes of the soft magnetic metal particles included in the preliminary compact body 60b having the RT-type shape are relatively reduced, D2 is not readily reduced as much as D1. Thus, relatively reducing the particle sizes of the specific particles included in the preliminary compact body 60b having the RT-type shape readily reduces D1/D2.
A manufacturing method 2 is described below. The manufacturing method 2 is similar to the manufacturing method 1 unless otherwise specified.
In the manufacturing method 2,
In this situation, unlike the manufacturing method 1, the coil corner neighboring region 605 being within the predetermined range from the coil corner 4β5 where the inner circumferential surface 4β1 and the first end surface 4β2 shown in
A manufacturing method 3 is described below. The manufacturing method 3 is similar to the manufacturing method 1 unless otherwise specified.
As shown in
The preliminary compact bodies 60c to 60e are similar to the preliminary compact bodies 60a and 60b except for their shapes.
In the manufacturing method 3, as shown in
First, the preliminary compact body 60c is inserted into a mold. Then, as shown in
Then, thermocompression bonding is carried out. Specifically, after the preliminary compact bodies 60c to 60e inserted into the mold are heated to a temperature at which the resin softens, the preliminary compact bodies 60c to 60e and the insert member 40a are thermocompression-bonded. The preliminary compact bodies 60c to 60e, the insert member 40a, etc. may be heated (preheated) in advance. The frame, punch, or the like of the mold may be heated. The direction in which pressure is applied is the winding axis direction of the coil. By pressing, the winding portion 4 and the core portion 6 are thermocompression-bonded for integration. The preliminary compact bodies 60c to 60e are deformed by thermocompression bonding, and spaces shown in
By thermocompression bonding, the preliminary compact bodies 60c to 60e are integrated to give the core portion 6.
In the manufacturing method 3 of manufacturing the inductor 2 according to the one embodiment of the present disclosure, the preliminary compact body 60d having the cylindrical shape may be tapered at its extremities, i.e., portions that are eventually located near the coil corner neighboring region 6β5. The preliminary compact body 60d having the cylindrical shape may be tapered at its extremities. Tapering provides spaces at the portions that are located near the coil corner neighboring region 6β5 when the preliminary compact bodies 60c to 60e and the insert member 40a are combined.
In a situation where the preliminary compact bodies including the soft magnetic metal particles and the resin are thermocompression-bonded, the resin exudes at a joint. In a situation where the extremities of the preliminary compact body 60d are tapered as described above, much of the resin exudes from the preliminary compact bodies 60c to 60e into the spaces provided by tapering. By contrast, the amount of the soft magnetic metal particles that move into these spaces from the preliminary compact bodies 60c to 60e is relatively small. Thus, at the spaces provided by tapering the extremities at both sides of the preliminary compact body 60d and their vicinity, the density of the soft magnetic metal particles is reduced, and the average inter-particle distance between the specific particles is increased. That is, at two coil corner neighboring regions 6β5 being within the predetermined range from two coil corners 4β5 where the inner circumferential surface 4β1 and the first end surface 4β2 meet and at two coil corner neighboring regions 6β5 being within the predetermined range from two coil corners 4β5 where the inner circumferential surface 4β1 and the second end surface 4β3 meet in a section of the inductor 2, D2 is increased. That is, in all of the four coil corner neighboring regions 6β5 shown in
By contrast, the average inter-particle distance between the specific particles in the axially central region 6α almost does not vary according to presence or absence of the tapering. Thus, D1 almost does not vary according to presence or absence of the tapering.
Thus, providing the tapering can reduce D1/D2 of all four coil corner neighboring regions 6β5 to less than 1.00, allowing 0<D1/D2<1.00 to be satisfied.
In the manufacturing method 3, D1/D2 of all four coil corner neighboring regions 6β5 of the inductor 2 can be reduced to less than 1.00, allowing 0<D1/D2<1.00 to be satisfied. That is, inductance and DC superimposition characteristics of this inductor 2 are more readily improved than when the manufacturing method 1 or 2 is used.
Methods of manufacturing the inductor 2 according to the present disclosure are not limited to those described above. In particular, the shapes and the number of cores are not limited as long as the inductor 2 shown in
Coil components according to the present disclosure are not limited to inductors. In some embodiments, for example, the coil components are coil components such as transformers or reactors. However, a fact that the coil components according to the present disclosure readily have improved inductance and a fact that it is difficult for a transformer or a reactor to be integrally molded being considered, the coil components according to the present disclosure are inductors in some embodiments.
A power supply apparatus according to the present disclosure includes the above coil component. In some embodiments, the power supply apparatus is, for example, a power supply such as a switching power supply or a power amplifier.
Hereinafter, the present disclosure is described based on further detailed examples. However, the present disclosure is not limited to these examples.
A method of manufacturing inductor samples of Examples and Comparative examples shown in Table 1 is described.
First, preliminary compact bodies 60a and 60b having respective shapes shown in
As materials of the preliminary compact body 60a, a resin and a soft magnetic metal powder including soft magnetic metal particles were prepared. The soft magnetic metal particles were made from an Fe—Si alloy (Fe 93.5 wt %, Si 6.5 wt %). The soft magnetic metal powder had a particle size such that R2 was as shown in Table 1. As the resin, an epoxy resin was used.
Then, an insulating film was provided on surfaces of the soft magnetic metal particles. Specifically, a sol gel method was used to provide the insulating film, which was a SiO2 film. The insulating film had a thickness of about 4βnm.
Next, the soft magnetic metal powder and the resin were mixed and were granulated into granules. Specifically, the resin was added to the soft magnetic metal powder, and the mixture was stirred and then dried at 4β° C. for 10 hours. With regard to the proportion of the resin, the resin weighed 2 to 3 parts by weight with respect to 100 parts by weight of the soft magnetic metal powder. The type of the resin was the epoxy resin. After addition of the resin to the soft magnetic metal powder and stirring, the stirred mixture was sieved with a mesh to remove coarse granules. Specifically, the mixture was sieved with a mesh with an opening of 100 μm. Eventually resulting granules had an average size of about 60 μm.
Next, a mold was filled with the resulting granules, and a core was molded, to give the preliminary compact body 60a having a pot-type shape shown in
The preliminary compact body 60b having an RT-shape shown in
In each Example, the preliminary compact body 60b was appropriately tapered at its extremity so that D1/D2 was as shown in Table 1.
The winding portion 4 of the insert member 40a had an outside diameter of 4.67 mm, an inside diameter of 2.80 mm, a wire diameter (diameter of a conductor 5) of 0.22 mm, a number of turns N of 61.5 ts., and a height H of 4.16 mm. The conductor 5, the lead-out wires, and the terminals were made from Cu.
First, the preliminary compact body 60a was inserted into a mold. Then, as shown in
Then, thermocompression bonding was carried out. Specifically, after the preliminary compact bodies 60a and 60b and the insert member 40a inserted into the mold were heated at 80° C. to soften the resin, pressure was applied to them. The direction in which pressure was applied was a winding axis direction of the coil. By pressing, the coil and the preliminary compact bodies were thermocompression-bonded for integration. The molding pressure of thermocompression bonding was 100 MPa.
Each inductor 2 taken out from the mold after molding by thermocompression bonding was heated to cure the resin. The heating temperature was 150° C. to 200° C. The heating time was 1 hour to 3 hours. The heating temperature and the heating time were appropriately controlled so that D1/D2 was as shown in Table 1.
The above steps gave the inductor 2 shown in
R1, R2, D1, and D2 of each sample inductor were calculated using sectional SEM images of the inductor cut in a section containing an axial centerline. Table 1 shows the results. The magnification of the SEM images was ×500. R2 and D2 were measured in two coil corner neighboring regions 6β5 being within a predetermined range from two coil corners 405 where an inner circumferential surface 4β1 and a second end surface 4β3 met in the section. It was confirmed that R2 was the same between the two coil corner neighboring regions 6β5 and that D2 was the same between the two coil corner neighboring regions 6β5. In calculation of R1 and R2, the soft magnetic metal particles having a particle size of less than 10 μm or a particle size exceeding 50 μm were not taken into account. In calculation of D1 and D2, the soft magnetic metal particles having a particle size of less than 10 μm were not taken into account.
Inductance L0 of each sample before a direct current was applied was measured. L0 was measured using an RF impedance material analyzer (4491A manufactured by Agilent Technologies) at a measurement frequency of 1.0 MHz and a measurement voltage of 500 μmV. Table 1 shows the results.
Isat of each sample was measured to evaluate DC superimposition characteristics. Specifically, with a direct current starting from 0 being applied to each inductor, the direct current at which inductance was reduced to 0.8×L0 (inductance at a direct current of 0) was defined as Isat. Table 1 shows the results.
For each sample, L0×Isat was calculated. Table 1 shows the results. When L0× Isat was 6.0 (H×A) or more, inductance and DC superimposition characteristics were defined as good. Table 1 shows the results.
Using an X-ray density distribution measuring apparatus, it was confirmed in all samples that an axially central region 6α had a density higher than that of a peripheral region 6γ and that difference between the density of the axially central region 6α and the density of the peripheral region 6γ was 0.20 g/cm3 or less.
According to Table 1, the coil components satisfying 0<D1/D2<1.00 had higher L0×Isat, better inductance, and better DC superimposition characteristics than the coil components satisfying D1/D2≥1.00.
The technology of the present disclosure includes the following example configurations but may include any other configurations.
[1]A coil component including:
[2] The coil component according to [1] satisfying 0.20≤R1/R2≤5.00, where R1 denotes an average particle size of the specific particles in the axially central region and R2 denotes an average particle size of the specific particles in the coil corner neighboring region.
[3] The coil component according to [1] or [2], in which
[4] The coil component according to [3], in which difference between the density of the axially central region and that of the peripheral region is 0.20 g/cm3 or less.
[5] The coil component according to any one of [1] to [4], in which the soft magnetic metal particles include Fe based soft magnetic particles.
[6] The coil component according to any one of [1] to [5], in which the resin includes an epoxy resin.
[7] The coil component according to any one of [1] to [6], in which
[8] The coil component according to any one of [1] to [7], in which
[9] The coil component according to any one of [1] to [8] satisfying 0.19<D1/D2<0.70.
[10]A power supply apparatus including the coil component according to any one of [1] to [9].
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-170025 | Sep 2023 | JP | national |
