Wound core, manufacturing method thereof, and magnetic component

Abstract

To provide a magnetic core having high inductance and low core loss, a manufacturing method thereof, and a magnetic component.SOLUTION: A wound core 1 includes a winding portion 11 formed by winding a soft magnetic ribbon 105, and the winding portion includes an adhesive layer 103 in contact with a main surface of the soft magnetic ribbon. The soft magnetic ribbon has small pieces separated by cracks. The average crack spacing, which indicates the average spacing between the cracks, is 0.015 mm or more and 1.000 mm or less, and the average crack spacing is 1 / 10 or less of the inner peripheral length of the winding portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a winding core, a method for manufacturing the same, and a magnetic component.

Background Art

[0002] In recent years, there has been a demand for higher power density of power supplies. Along with this, in the field of magnetic components used in power supplies and the like, for example, in the field of choke coils, a magnetic core having a high inductance and low core loss is required.

[0003] Soft magnetic thin strips are known as magnetic materials having high soft magnetic properties. And a laminated core in which small pieces of soft magnetic thin strips are laminated is known.

[0004] Patent Document 1 discloses a laminated core using small pieces of thin strips.

[0005] However, in order to increase the thickness of the laminated core, it is necessary to increase the number of laminations. The manufacturing cost of the laminated core tends to increase according to the number of laminations. When punching out the laminated core, stress is applied to the laminated core. It is difficult to avoid a decrease in soft magnetic properties due to the application of stress. In the laminated core, a sufficiently high adhesive strength is required to suppress peeling between the soft magnetic layers. That is, it is necessary to increase the thickness of the adhesive layer between the soft magnetic layers.

[0006] It has been difficult for the laminated core to achieve both high inductance and low core loss, and its applications have been limited despite its high soft magnetic properties.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a magnetic core or the like having a high inductance and a low core loss.

Means for Solving the Problems

[0009] In order to achieve the above object, a wound core of the present invention is a wound core having a wound portion formed by winding a soft magnetic thin strip, the wound portion includes an adhesive layer in contact with the main surface of the soft magnetic thin strip, the soft magnetic thin strip has small pieces separated by cracks, an average crack interval indicating an average of intervals between the cracks is 0.015 mm or more and 1.000 mm or less, and the average crack interval is 1 / 10 or less of the inner peripheral length of the wound portion.

[0010] In a cross section perpendicular to the winding axis of the soft magnetic thin strip, the area ratio of the magnetic material in the wound portion of the wound core may be greater than 75% and less than 97%.

[0011] A structure composed of Fe-based nanocrystals may be observed in the soft magnetic thin strip of the wound core, and the average particle size of the Fe-based nanocrystals may be 5 to 30 nm.

[0012] A magnetic component of the present invention includes the above wound core and a conductor.

[0013] A method for manufacturing a wound core of the present invention includes a step of forming an adhesive layer on at least one main surface of a soft magnetic thin strip, a step of fragmenting the soft magnetic thin strip on which the adhesive layer is formed, and a step of winding the fragmented soft magnetic thin strip.

[0014] In the method for manufacturing the wound core, the adhesive layer may be formed on the surface of a support sheet, the soft magnetic thin strip may be formed on the surface of the adhesive layer, and then the soft magnetic thin strip may be fragmented on the support sheet.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0017] The configuration of the winding core 1 according to this embodiment will be described. FIG. 1 is a schematic diagram of a cylindrical winding core 1 cut along a cross-section perpendicular to the winding axis. The winding core 1 has a winding portion 11. There are no particular restrictions on the outer diameter, inner diameter, and height of the winding portion 11. For example, the outer diameter may be 0.5 mm or more and 150 mm or less. The inner diameter may be 0.2 mm or more and 100 mm or less, or may be 2.0 mm or more and 50 mm or less. The height may be 1.0 mm or more and 250 mm or less. Further, in FIG. 1, the adhesive layer 103 is wound so as to be on the inner side, but it may be wound so that the adhesive layer 103 is on the outer side.

[0018] FIG. 1 three-dimensionally illustrates an example of the winding direction of the conductor 21 when the conductor 21 is wound around the winding portion 11 of the winding core 1 to obtain a magnetic component. However, the winding direction of the conductor 21 is not limited to the direction shown in FIG. 1, and any direction in which the combination of the winding core 1 and the conductor 21 functions as a magnetic component is acceptable. Also, as shown in FIG. 1, the conductor 21 may be wound around a part of the winding portion 11 or may be wound around the entire winding portion 11.

[0019] The magnetic component including the winding core 1 may include components other than the winding core 1 and the conductor 21. For example, a bobbin described later can be mentioned.

[0020] The winding core 1 may include components other than the winding portion 11. For example, a protective film may be provided on the outer peripheral side and / or the inner peripheral side of the winding portion 11. As the protective film, known ones can be used. For example, PET film, polyimide film, aramid film, etc. can be mentioned. Also, the winding portion 11 may be placed in a protective case such as resin or ceramic.

[0021] As shown in FIG. 1, the winding portion 11 is formed by winding a soft magnetic thin strip 105. And the winding portion 11 has an adhesive layer 103 that contacts the main surface of the soft magnetic thin strip 105. The main surface of the soft magnetic thin strip 105 is a surface perpendicular or substantially perpendicular to the thickness direction of the soft magnetic thin strip 105. Note that the sand-like pattern portion in FIG. 1 is a gap portion that inevitably occurs because the soft magnetic thin strip 105 and the adhesive layer 103 have thickness.

[0022] There is no particular limitation on the number of windings of the soft magnetic thin strip 105 in the winding portion 11. For example, it may be 1 or more and 15000 or less.

[0023] As described above, the winding core 1 has the winding portion 11, and the winding portion 11 mainly has the soft magnetic thin strip 105 and the adhesive layer 103. The winding portion 11 may include components other than the soft magnetic thin strip 105 and the adhesive layer 103 as long as it does not inhibit the function of the magnetic component obtained by the combination of the winding core 1 and the conductor 21.

[0024] As shown in Fig. 6, a plurality of cracks C are formed in the soft magnetic thin strip 105. And due to the plurality of cracks C, the soft magnetic thin strip 105 is divided into a plurality of small pieces. In other words, the soft magnetic thin strip 105 has small pieces separated by cracks. Note that the width of the crack C may be, for example, 10 nm or more and 1000 nm or less.

[0025] In the wound core 1 according to the present embodiment, since a plurality of cracks C are formed in the soft magnetic thin strip 105 and the soft magnetic thin strip 105 is divided into a plurality of small pieces, a change in soft magnetic properties due to stress during manufacturing, particularly an increase in coercive force, is suppressed, and a wound core 1 with high inductance and low core loss can be provided.

[0026] In the present embodiment, when a virtual line B is drawn in the region divided and made into small pieces by the crack C, the value obtained by dividing the number of intersections D where the virtual line B intersects the crack C by the total length of the virtual line B is defined as the average crack interval. The average crack interval is a parameter indicating the average of the intervals between the cracks.

[0027] Hereinafter, with reference to the specific case shown in Fig. 6, a method for calculating the average crack interval will be described. In Fig. 6, a square observation range is shown. In Fig. 6, the crack C is shown by a solid line, and the virtual line B is shown by a dotted line.

[0028] The virtual line B extends in one direction (the horizontal direction in the figure) of the observation range, and 10 virtual lines B extend in parallel at equal intervals in the vertical direction in the figure. At this time, the number of intersections D where the virtual line B intersects the crack C is measured. The number of intersections D becomes the total number of cracks C intersecting the virtual line B. The total length of the virtual line B divided by the total number of cracks C intersecting the virtual line B (the number of intersections D) is defined as the average crack interval. Expressed in a calculation formula, it is as shown in formula (1). Average crack interval (mm) = (Total length of virtual line B) / (Number of intersections D) ··· Formula (1)

[0029] In the example shown in FIG. 6, if the observation range is a square with a side length of 4 mm, the total length of the virtual line B is 40 mm and the number of intersections D is 43. Therefore, the average crack interval is 40 / 43 [mm], which is approximately 0.93 mm.

[0030] Since the average crack interval varies depending on the selected observation range, it is preferable to calculate the average by calculating it in a plurality of observation ranges. Preferably, the average is calculated in three or more different observation ranges. Also, it is preferable to determine how to select the observation range. For example, when using the winding core 1 shown in FIG. 1, when calculating the average crack interval, the observation range to be selected can be selected so as to include a plane perpendicular or substantially perpendicular to the thickness direction of the soft magnetic thin strip 105. The plane perpendicular or substantially perpendicular to the thickness direction of the soft magnetic thin strip 105 may be the surface or the cross section of the soft magnetic thin strip 105. The method for measuring the average crack interval is arbitrary. For example, SEM can be used.

[0031] Cracks are formed in the soft magnetic thin strip 105 such that the average crack interval is 0.015 mm or more and 1.000 mm or less, and the average crack interval is 1 / 10 or less of the inner peripheral length IL of the winding portion 11. The average crack interval may be 0.015 mm or more and 0.750 mm or less. As shown in FIG. 1, the inner peripheral length IL of the winding portion 11 is the length of the inner periphery of the winding portion 11 in a cross section perpendicular to the winding axis. For example, when the inner periphery of the winding portion 11 can be approximated as circular as shown in FIG. 1, with the inner diameter (inner side diameter) of the winding portion 11 being ID, IL is equal to ID×π.

[0032] When the average crack interval is too small, the inductance of the magnetic component obtained by winding the conductor 21 around the winding portion 11 of the winding core 1 decreases. As the average crack interval increases, the inductance of the magnetic component obtained by winding the conductor 21 around the winding portion 11 of the winding core 1 increases, but as the average crack interval increases, the core loss of the magnetic component also increases.

[0033] In a laminated core having a laminate obtained by alternately laminating a soft magnetic layer in which cracks are formed and an adhesive layer, in a cross section parallel to the lamination direction, it is difficult to reduce the area ratio of the adhesive layer to the area of the laminated portion and increase the area ratio of the magnetic material to the area of the laminated portion (usually equal to the area ratio of the soft magnetic layer). This is because when the area ratio of the magnetic material is increased, the strength of the laminated core is significantly reduced and small pieces are peeled off from the adhesive layer. Since it is difficult to increase the amount of magnetic material contained in the laminated core, it is difficult to improve the characteristics of the laminated core.

[0034] In the wound core 1 having the configuration shown in FIG. 1, the area ratio of the magnetic material to the area of the wound portion 11 in a cross section perpendicular to the winding axis corresponds to the area ratio of the magnetic material to the area of the laminated portion in the laminated core.

[0035] In the wound core 1 having the configuration shown in FIG. 1, it is relatively easy to increase the area ratio of the magnetic material in a cross section perpendicular to the winding axis. This is because even if the area ratio of the magnetic material is increased, the strength of the wound core 1 is less likely to decrease and small pieces are less likely to be peeled off from the adhesive layer 103. Therefore, the wound core 1 in which the soft magnetic thin strip 105 is divided into a plurality of small pieces can increase the area ratio of the magnetic material compared to the laminated core in which the soft magnetic layer is divided into a plurality of small pieces, and can improve the inductance and reduce the core loss. There is no particular limitation on the area ratio of the magnetic material. For example, the lower limit may be greater than 75%, may be 76% or more, or may be 79% or more. The upper limit may be less than 99%, may be less than 97%, or may be 96% or less.

[0036] If the average crack interval is too large with respect to the above-mentioned inner peripheral length IL, specifically, if the average crack interval is larger than 1 / 10 of the inner peripheral length IL, winding becomes difficult and it becomes difficult to increase the area ratio of the magnetic material in the cross-section perpendicular to the winding axis. That is, it becomes difficult to improve the inductance and reduce the core loss by increasing the area ratio of the magnetic material. If the average crack interval is too large, the adhesive layer 103 may break. In that case, in particular, small pieces may peel off from the adhesive layer 103 in the vicinity of the inner circumference of the winding portion 11. If the average crack interval is too large and the breakage of the adhesive layer 103 is to be suppressed, it is necessary to increase the ratio of the adhesive layer 103. Therefore, when the average crack interval is too large, it becomes difficult to improve the inductance and reduce the core loss by increasing the area ratio of the magnetic material.

[0037] The winding core 1 can suppress the dropout of small pieces by having the adhesive layer 103. As the adhesive layer 103, a known one can be used. For example, adhesives such as acrylic adhesives, silicone resins, butadiene resins, epoxy resins, and hot melts can be mentioned. Also, double-sided tapes containing a PET base material can be used as the adhesive layer.

[0038] There is no particular limitation on the composition of the soft magnetic thin strip 105. For example, it may contain Fe as a main component.

[0039] The soft magnetic thin strip 105 has a composition formula (Fe (1-( α + β )) CoαNiβ) (1-(a+b+c+d+e+f+g)) M1 a M2 b B c P d Si e C f S g (atomic ratio) and may be composed of, M1 is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, V, and W, M2 is one or more selected from the group consisting of Cu, Al, Mn, Ag, Zn, Sn, As, Sb, Bi, O, and Yb, 0 ≤ a ≤ 0.150 0 ≤ b ≤ 0.060 0.010 < c ≤ 0.200 0 ≤ d ≤ 0.120 0 ≤ e ≤ 0.200 0 ≤ f < 0.050 0 ≤ g ≤ 0.040 0.650 < 1 - (a + b + c + d + e + f + g) < 0.900 α ≥ 0 β ≥ 0 0 ≤ α + β ≤ 0.600 may be satisfied.

[0040] 0 ≤ a ≤ 0.140 0 ≤ b ≤ 0.050 0.020 < c ≤ 0.200 0 ≤ d ≤ 0.100 0 ≤ e ≤ 0.180 0 ≤ f < 0.040 0 ≤ g ≤ 0.030 0.700 < 1 - (a + b + c + d + e + f + g) < 0.880 α ≥ 0 β ≥ 0 0 ≤ α + β ≤ 0.500 It is preferable to satisfy.

[0041] There is no particular limitation on the fine structure of the soft magnetic ribbon 105. The soft magnetic ribbon 105 may have a structure composed of amorphous or a structure composed of crystal. It is preferable that the soft magnetic ribbon 105 has a structure composed of Fe-based nanocrystals.

[0042] The Fe-based nanocrystal is a crystal having a particle size in the nano order (specifically, an average particle size of about 30 nm or less) and a bcc (body-centered cubic lattice structure) of the crystal structure of Fe. In this embodiment, it is preferable to precipitate Fe-based nanocrystals having an average particle size of 5 to 30 nm. Further, the structure composed of Fe-based nanocrystals means a structure including Fe-based nanocrystals and having an amorphization rate X of less than 85% as described below.

[0043] When the composition of the soft magnetic ribbon 105 is within the above range and further has a structure composed of Fe-based nanocrystals, a magnetic core 1 having good soft magnetic properties can be manufactured.

[0044] The composition of the soft magnetic ribbon 105 will be described in more detail.

[0045] M1 is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, V, and W. The soft magnetic ribbon 105 may contain at least Nb as M1, or the soft magnetic ribbon 105 may contain substantially only Nb as M1. Specifically, when substantially only Nb is contained as M1, it means that the ratio of the content of Nb to the total content of M1 is 95% or more on an atomic number basis.

[0046] The content (a) of M1 may satisfy 0 ≦ a ≦ 0.150, may satisfy 0 ≦ a ≦ 0.140, or may satisfy 0.020 ≦ a ≦ 0.140.

[0047] M2 is one or more selected from the group consisting of Cu, Al, Mn, Ag, Zn, Sn, As, Sb, Bi, O, and Yb. The soft magnetic ribbon 105 may contain at least Cu as M2, or the soft magnetic ribbon 105 may contain substantially only Cu as M2. Specifically, when substantially only Cu is contained as M2, it means that the ratio of the content of Cu to the total content of M2 is 95% or more on an atomic number basis.

[0048] The content (b) of M2 may satisfy 0 ≦ b ≦ 0.060, may satisfy 0 ≦ b ≦ 0.050, or may satisfy 0.001 ≦ b ≦ 0.045.

[0049] The content (c) of B may satisfy 0.010 < c ≦ 0.200, may satisfy 0.020 < c ≦ 0.200, or may satisfy 0.021 ≦ c ≦ 0.180.

[0050] The content (d) of P may satisfy 0 ≦ d ≦ 0.120, may satisfy 0 ≦ d ≦ 0.100, or may satisfy 0 < d ≦ 0.100.

[0051] The content (e) of Si may satisfy 0 ≦ e ≦ 0.200, or may satisfy 0 ≦ e ≦ 0.180.

[0052] The content (f) of C may satisfy 0 ≦ f < 0.050, may satisfy 0 ≦ f < 0.040, or may satisfy 0 ≦ f ≦ 0.037.

[0053] The content (g) of S may satisfy 0 ≦ g ≦ 0.040, may satisfy 0 ≦ g ≦ 0.030, or may satisfy 0 ≦ g ≦ 0.028.

[0054] In the soft magnetic thin strip 105, part of Fe may be replaced with Co and / or Ni.

[0055] As the range of the substitution ratio for replacing Fe with Co and / or Ni, it may be 60.0% or less of Fe on an atomic number basis, or may be 50.0% or less. That is, 0 ≦ α + β ≦ 0.600 may be satisfied, or 0 ≦ α + β ≦ 0.500 may be satisfied.

[0056] The total content (1-(a + b + c + d + e + f + g)) of Fe, Co, and Ni may satisfy 0.650 < 1-(a + b + c + d + e + f + g) < 0.900, or may satisfy 0.700 < 1-(a + b + c + d + e + f + g) < 0.880.

[0057] The soft magnetic thin strip 105 may contain inevitable impurities within a range that does not significantly affect the properties of elements other than those described above, that is, elements other than Fe, Co, Ni, M1, M2, B, P, Si, C, and S. For example, the total content may be 0.5% by weight or less based on 100% by weight of the soft magnetic alloy.

[0058] Hereinafter, the manufacturing method of the wound core 1 according to the present embodiment will be described.

[0059] First, a method for manufacturing the soft magnetic thin strip 105 included in the winding core 1 will be described. Hereinafter, the soft magnetic thin strip 105 may sometimes be simply referred to as the thin strip.

[0060] The method for manufacturing the soft magnetic thin strip 105 is not particularly limited. For example, there is a method of manufacturing by the single roll method. Further, the soft magnetic thin strip 105 may be a continuous thin strip.

[0061] In the single roll method, first, pure metals of each metal element included in the finally obtained soft magnetic thin strip 105 are prepared and weighed so as to have the same composition as the finally obtained soft magnetic thin strip 105. Then, the pure metals of each metal element are melted and mixed to produce a master alloy. Note that the method for melting the pure metal is not particularly limited. For example, there is a method of melting by high frequency heating after evacuating in a chamber. Note that the master alloy and the soft magnetic alloy composed of the finally obtained Fe-based nanocrystals usually have the same composition.

[0062] Next, the produced master alloy is heated and melted to obtain a molten metal (molten bath). The temperature of the molten metal is not particularly limited, but for example, it can be set to 1100 to 1600 °C.

[0063] In the single roll method, the thickness of the obtained thin strip can be adjusted mainly by adjusting the rotation speed of the roll. However, the thickness of the obtained thin strip can also be adjusted by adjusting, for example, the distance between the nozzle and the roll and the temperature of the molten metal. The thickness of the thin strip may be appropriately determined according to, for example, the area ratio of the magnetic material to the area of the winding portion 11 in the cross section perpendicular to the winding axis of the finally obtained winding core 1. For example, it may be 10 to 50 μm.

[0064] There are no particular restrictions on the temperature of the roll, the rotation speed, and the atmosphere inside the chamber. When the soft magnetic ribbon 105 contained in the finally obtained wound core 1 has a structure composed of Fe-based nanocrystals, the temperature of the roll is generally set to be not lower than room temperature and not higher than 80 °C. The lower the temperature of the roll, the smaller the average grain size of the fine crystals described later tends to be. The higher the rotation speed of the roll, the smaller the average grain size of the fine crystals described later tends to be. For example, it is set to 10 to 30 m / sec. Considering the cost, the atmosphere inside the chamber is preferably air.

[0065] At the time point before the heat treatment described later, the ribbon has a structure composed of amorphous. That is, it has a structure composed only of amorphous or a nanoheterostructure. By subjecting the ribbon having a structure composed of amorphous to the heat treatment described later, a ribbon having a structure composed of Fe-based nanocrystals can be obtained. Also, a ribbon having a nanoheterostructure may be obtained by performing a heat treatment on a ribbon having a structure composed only of amorphous.

[0066] The nanoheterostructure refers to a structure composed of amorphous and fine crystals, and the fine crystals are present in the amorphous. Also, being composed of amorphous and fine crystals indicates that the fine crystals are scattered in the amorphous. That the fine crystals are scattered in the amorphous means that the amorphization rate X measured by ordinary X-ray diffraction measurement (XRD) is 85% or more, and the crystal phase can be confirmed by the electron diffraction image and the high-resolution image in the transmission electron microscope. Also, the fine crystal refers to a crystal having a particle size of 30 nm or less. Note that the average grain size of the fine crystals may be in the range of 0.3 to 5 nm.

[0067] Whether the ribbon of the soft magnetic alloy has a structure composed of amorphous or a structure composed of crystals can be confirmed by ordinary X-ray diffraction measurement (XRD).

[0068] Specifically, X-ray structure analysis is performed by XRD, the amorphization rate X (%) shown in the following formula (1) is calculated, and when it is 85% or more, it is considered to have a structure composed of amorphous, and when it is less than 85%, it is considered to have a structure composed of crystals. X(%) = 100 - (Ic / (Ic + Ia)×100)…(1) Ic: Crystalline scattering integral intensity Ia: Amorphous scattering integral intensity

[0069] To calculate the amorphization rate X, first, X-ray crystallographic analysis is performed on the soft magnetic alloy according to this embodiment by XRD to obtain the chart shown in FIG. 7. Profile fitting is performed on the chart using the Lorentz function shown in the following formula (2).

Equation

[0070] As a result of profile fitting, a crystal component pattern α showing the crystalline scattering integral intensity shown in FIG. 8 c , an amorphous component pattern α showing the amorphous scattering integral intensity a , and a combined pattern α of them c+a are obtained. The crystalline scattering integral intensity Ic and the amorphous scattering integral intensity Ia are obtained from each of the obtained patterns. The amorphization rate X is obtained from Ic and Ia according to the above formula (1). Note that the measurement range is the range of diffraction angle 2θ where a halo derived from the amorphous material can be confirmed. Specifically, it is in the range of 2θ = 30° to 60°. In this range, the error between the actually measured integral intensity by XRD and the integral intensity calculated using the Lorentz function is made within 1%.

[0071] The amorphization rate (X A ) on the surface of the soft magnetic thin strip 105 that was in contact with the roll surface and the amorphization rate (X B ) on the surface that was not in contact with the roll surface may be different. In this case, the average of X A and X B is taken as the amorphization rate X.

[0072] The thin strip before heat treatment may have a structure consisting only of amorphous, but preferably has a nanohetero structure. Note that there is no particular limitation on the grain size of the microcrystals in the nanohetero structure, but it is preferably in the range of 0.3 to 5 nm in average grain size.

[0073] When observing the presence or absence of microcrystals and the average grain size in the case where the thin strip before heat treatment has a nanoheterostructure, for example, for a sample thinned by ion milling, the electron diffraction image and the high-resolution image can be obtained using a transmission electron microscope for confirmation. When using the electron diffraction image, in the case of a structure consisting only of amorphous in the diffraction pattern, ring-shaped diffraction is formed, whereas in the case of a structure containing microcrystals, diffraction spots due to the microcrystals are formed. Further, when using the high-resolution image, the presence or absence of microcrystals and the average grain size can be observed by visual observation at a magnification of 1.00×10 5 ~3.00×10 5 times.

[0074] There are no particular restrictions on the heat treatment conditions for manufacturing a thin strip having a structure composed of Fe-based nanocrystals. The preferred heat treatment conditions vary depending on the composition of the soft magnetic thin strip 105. Usually, the preferred heat treatment temperature is generally 400 to 700 °C, and the preferred heat treatment time is generally 0.1 to 6 hours. However, depending on the composition, there may be cases where the preferred heat treatment temperature and heat treatment time exist outside the above range. Also, there are no particular restrictions on the atmosphere during heat treatment. It may be carried out under an active atmosphere such as in the air, or under an inert atmosphere such as in Ar gas or N2 gas. By heat treatment, the soft magnetic thin strip becomes brittle and is in a state where it is easy to perform the chip-forming treatment. Further, the residual strain in the soft magnetic thin strip is removed.

[0075] Also, there are no particular restrictions on the method for calculating the average grain size of the crystals contained in the obtained soft magnetic thin strip. For example, it can be calculated by observing using a transmission electron microscope. Also, there are no particular restrictions on the method for confirming that the crystal structure is bcc (body-centered cubic lattice structure). For example, it can be confirmed using X-ray diffraction measurement.

[0076] There are no particular restrictions on the method for manufacturing the wound core 1. For example, as shown in FIGS. 9 and 10, an adhesive layer forming step of applying an adhesive to the support sheet 101 to form the adhesive layer 103, an adhesion step of forming the adhesive layer 103 on at least one main surface of the soft magnetic thin strip 105, a crack forming step (fragmentation step) of fragmenting the soft magnetic thin strip 105 having the adhesive layer 103 formed thereon, a peeling step of peeling the support sheet 101 from the adhesive layer 103, a winding step of cutting the soft magnetic thin strip 105 to a predetermined length and winding the soft magnetic thin strip 105 cut to the predetermined length.

[0077] The adhesion step of forming the adhesive layer 103 on at least one main surface of the soft magnetic thin strip 105 can also be said to be an adhesion step of forming the soft magnetic thin strip 105 on the surface of the adhesive layer 103.

[0078] Hereinafter, an outline of each step will be described.

[0079] (Adhesive layer forming step) First, as shown in FIG. 9, the support sheet 101 is pulled out from the support sheet roll 201 around which the support sheet 101 is wound. There are no particular restrictions on the material of the support sheet 101. The material of the support sheet 101 is typically a PET film. However, in addition to the PET film, resin films such as polyimide films, polyester films, polyphenylene sulfide (PPS) films, polypropylene (PP) films, and fluororesin films such as polytetrafluoroethylene (PTFE) can be mentioned.

[0080] Then, an adhesive is applied to the support sheet 101 to form the adhesive layer 103. The adhesive layer 103 is formed, for example, by applying an adhesive to the support sheet 101 using the adhesive application nozzle 203. Note that in FIGS. 9 and 10, the thickness of the adhesive layer 103 is exaggerated. In reality, the adhesive layer 103 is often much thinner compared to the soft magnetic thin strip 105.

[0081] (Adhesion step) As shown in FIG. 9, the soft magnetic thin strip 105 is drawn out from the thin strip roll 205 around which the soft magnetic thin strip 105 is wound. At least one main surface of the drawn soft magnetic thin strip 105 is brought into contact with the surface of the adhesive layer 103. Then, by applying pressure in the thickness direction of the soft magnetic thin strip 105 with the bonding roller 207, the adhesive layer 103 is formed on at least one main surface of the soft magnetic thin strip 105. In other words, the soft magnetic thin strip 105 is formed on the surface of the adhesive layer 103.

[0082] In addition, when the soft magnetic thin strip 105 included in the finally obtained winding core 1 has a structure composed of Fe-based nanocrystals, it is preferable to perform heat treatment before the bonding step and use the soft magnetic thin strip 105 having a structure composed of Fe-based nanocrystals in the bonding step. However, heat treatment may be performed after the bonding step so that the soft magnetic thin strip 105 has a structure composed of Fe-based nanocrystals.

[0083] (Crack formation step (fragmentation step)) Cracks are generated in the soft magnetic thin strip 105 on which the adhesive layer 103 is formed to fragment it. There is no particular limitation on the method of generating cracks. For example, as shown in FIG. 9, a method of fragmenting using a pair of fragmentation rollers 209 can be mentioned. The pair of fragmentation rollers 209 is composed of two rollers, a roller on the adhesive layer 103 side and a roller on the soft magnetic thin strip 105 side. There is no particular limitation on the method of controlling the average crack interval. For example, the average crack interval can be controlled by appropriately controlling (the shape of the unevenness of each roller constituting the fragmentation roller 209, the density of the unevenness of each roller constituting the fragmentation roller 209, the number of sets of the fragmentation roller 209, the size of the gap of the fragmentation roller 209). Note that the gap of the small piece roller 209 refers to the interval between the roller on the adhesive layer 103 side and the roller on the soft magnetic thin strip 105 side.

[0084] When cracks are generated in the soft magnetic thin strip 105 where the adhesive 103 is not formed and the strip is fragmented, the small pieces divided by the cracks are likely to scatter. By forming the adhesive layer 103 in advance, it becomes easier to prevent the small pieces divided by the cracks from scattering. That is, although the soft magnetic thin strip 105 after crack formation is divided into a plurality of small pieces, the positions of all the small pieces are fixed via the adhesive layer 103. As a whole, the shape of the soft magnetic thin strip 105 before crack formation is substantially maintained even after crack formation.

[0085] The support sheet 101 is not essential, but considering stably generating cracks in the soft magnetic thin strip 105, it is preferable to generate cracks in the soft magnetic thin strip 105 on the support sheet 101. For example, as a method of manufacturing without the support sheet 101, there is a method of directly applying the adhesive layer 103 to the soft magnetic thin strip 105. However, when using the fragmentation roller 209 shown in FIG. 9 without the support sheet 101, the adhesive layer 103 comes into contact with the fragmentation roller 209 and the adhesive adheres to the fragmentation roller 209. Therefore, it becomes difficult to stably generate cracks in the soft magnetic thin strip 105.

[0086] The soft magnetic thin strip 105 after crack formation may be once wound around the winding roll 211 as shown in FIG. 9. Then, as shown in FIG. 10, the soft magnetic thin strip 105 after crack formation may be pulled out from the winding roll 211 and the peeling process described later may be performed. Alternatively, the peeling process described later may be directly performed on the soft magnetic thin strip 105 after the crack formation process.

[0087] (Peeling Process) As shown in FIG. 10, the support sheet 101 is removed by peeling the support sheet 101 from the adhesive layer 103. There is no particular limitation on the method of peeling the support sheet 101.

[0088] (Winding Process) First, as shown in FIG. 10, the soft magnetic thin strip 105 is wound together with the adhesive layer 103 to form a wound portion 11. When the winding reaches a predetermined length, the soft magnetic thin strip 105 is cut together with the adhesive layer 103 using a cutting device 213. The predetermined length is determined by the size of the target wound portion 11. There are no particular restrictions on the cutting method or the type of cutting device 213.

[0089] If necessary, a tension adding roller 215 for adding a certain tension to the soft magnetic thin strip 105 and a stabilizing roller 217 for winding the soft magnetic thin strip 105 with a certain force may be used.

[0090] Also, a winding core may be used when winding the soft magnetic thin strip 105. By controlling the size of the winding core, the inner diameter ID and the inner peripheral length IL of the wound portion 11 can be controlled. The winding core may or may not be removed after the winding process. If the winding core is not removed, the winding core may be included in the magnetic component including the winding core 1 and the conductor 21.

[0091] The winding core 1 can be manufactured by the above steps. At least the bonding step, the crack forming step (fragmentation step), and the winding step are essential. The adhesive layer forming step and the peeling step are not essential when the support sheet 101 is not used.

[0092] In FIG. 1, a cylindrical winding core 1 is illustrated, but the shape of the winding core 1 is not particularly limited.

[0093] For example, as shown in FIG. 2, a cut (air gap) may be provided in a part of the wound portion 11. In this case, the inner peripheral length IL of the wound portion 11 is calculated assuming that there is no wound portion 11 in the cut portion.

[0094] In a conventional winding core, the magnetic permeability becomes too high, making it difficult to control the DC superposition characteristics. Although the magnetic permeability can be reduced by providing a large air gap, the leakage magnetic flux increases and the core loss increases.

[0095] In the wound core of the present embodiment in which the soft magnetic ribbon has cracks, it is not necessary to provide an air gap to control the magnetic permeability, and even when an air gap is provided, the air gap can be made small, so that the influence of leakage magnetic flux can be easily suppressed.

[0096] As shown in FIG. 3, the shape of the wound core 1 may be a shape in which the divided wound portions 11 are combined. In this case, the inner peripheral length IL of the wound portion 11 is calculated assuming that there is no wound portion 11 in the gap portion between the wound portions 11.

[0097] As shown in FIG. 4, the shape of the wound core 1 may be a shape other than a perfect circle, for example, a polygonal cylindrical shape. As shown in FIG. 5, the shape of the magnetic core 1 may be a shape in which three wound portions 11a to 11c having a polygonal cylindrical shape are combined. The magnetic core 1 shown in FIG. 5 is understood to be a magnetic core in which three wound cores are combined. An example of a location where the conductor 21 is wound around the magnetic core 1 shown in FIG. 5 is shown three-dimensionally. Also, in FIG. 5, the inner peripheral length of the wound portion 11a is denoted as ILa, the inner peripheral length of the wound portion 11b is denoted as ILb, and the inner peripheral length of the wound portion 11c is denoted as ILc.

[0098] The use of the wound core 1 is not particularly limited, but for example, it can be used for coil components (such as transformers and choke coils) including conductors.

Example

[0099] (Experimental Example 1) <Fabrication of Soft Magnetic Ribbon> The raw material metals were weighed so that the alloy composition was Fe in atomic ratio 0.820 Nb 0.055 Cu 0.005 B 0.090 P 0.030 and melted by high-frequency heating to produce a master alloy.

[0100] Thereafter, the prepared master alloy was heated and melted to form a molten metal at 1250°C, and then the metal was sprayed onto a roll by a single-roll method using a roll at 60°C rotating at a speed of 20 m / sec in the atmosphere to create a thin strip. The thickness of the thin strip was set to 20 μm (= 0.02 mm). The width of the thin strip was made the same as the height of the winding portion described later.

[0101] Thereafter, heat treatment was performed on the thin strip. Regarding the heat treatment conditions, the heat treatment temperature was 600°C, the holding time was 60 minutes, the heating rate was 10°C / min, and the cooling rate was 10°C / min.

[0102] <Microstructure of Soft Magnetic Thin Strip> The microstructure of each thin strip after heat treatment was confirmed by X-ray diffraction measurement (XRD) and observation using a transmission electron microscope (TEM). Specifically, it was observed which structure among a structure composed of Fe-based nanocrystals, a nanoheterostructure, or a structure composed only of amorphous was observed in each thin strip. As a result, it was confirmed that all the thin strips had a structure composed of Fe-based nanocrystals in the experimental examples other than Experimental Example 5 described later. And in the experimental examples other than Experimental Example 5 described later, it was confirmed that the average grain size of the Fe-based nanocrystals in all the thin strips was 50 nm or less.

[0103] <Fabrication of Winding Core> A winding core was fabricated by the method shown in FIGS. 9 and 10. And the winding cores of each example were fabricated through the above respective steps. In Experimental Example 1, the shape of the winding core was a cylindrical shape with a height of 5 mm (excluding sample numbers 6a, 6, and 6L). In sample numbers 6a, 6, and 6L, the shape of the winding core was a cylindrical shape with a height of 3 mm. The outer diameter OD and the inner diameter ID were made to be the values shown in Table 1.

[0104] A PET film was used as the support sheet. A resin was used as the adhesive. The amount of the resin was controlled so that the area ratio of the magnetic material in the winding portion was 82% in a cross section parallel to the winding axis of the finally obtained wound core. The size of the fragmentation roller, the magnitude of the pressure applied to the soft magnetic thin strip by the fragmentation roller, the shape of the fragmentation roller (e.g., the shape of the unevenness on the surface of the fragmentation roller), the number of times the soft magnetic thin strip passes through the fragmentation roller, etc. were appropriately changed to adjust the average crack interval (A) to the value shown in Table 1.

[0105] The size of the winding core in the winding process was controlled so that the inner peripheral length IL of the winding portion included in the wound core was the size shown in Table 1. The number of winding turns of the soft magnetic thin strip was controlled so that the wound core had a desired outer diameter. Note that the winding core was removed after the soft magnetic thin strip was wound.

[0106] The area ratio of the magnetic material was calculated by the following formula, where N1 is the number of winding turns of the soft magnetic thin strip, t is the thickness of the soft magnetic thin strip, ID is the inner diameter of the winding portion, and OD is the outer diameter of the winding portion. Area ratio of magnetic material (%) = 100 × {(N1 × t) / (OD - ID)}

[0107] However, for the wound cores of sample numbers 5a and 6a in Table 1 where A / B was too large, the strength decreased and small pieces peeled off from the adhesive layer. Therefore, wound cores of sample numbers 5 and 6 were produced under the same conditions as sample numbers 5a and 6a except that the amount of the adhesive was increased to reduce the area ratio of the magnetic material.

[0108] <Fabrication of laminated core> A resin solution was applied to the same soft magnetic thin strip as that used for the production of the wound core. Then, the solvent was dried to form an adhesive layer on both sides of the soft magnetic thin strip, thereby producing a magnetic sheet provided with the adhesive layer. The thickness of the adhesive layer was set so that the area ratio of the magnetic material in a cross section parallel to the lamination direction in the finally obtained laminated core was 75%.

[0109] Next, a crack formation process was performed on the produced magnetic sheet so that the average crack interval of the soft magnetic thin strip became the value described in Table 1, and a fragmented magnetic sheet was produced.

[0110] Next, punching was performed on the obtained fragmented magnetic sheet. Specifically, the fragmented magnetic sheet was sandwiched between a punching die and a face plate, and pressure was applied from the face plate side toward the punching die side. By punching, the shape of the fragmented magnetic sheet was made into a cylindrical shape with the same inner diameter ID and outer diameter OD as the wound core of the corresponding example.

[0111] Next, a plurality of the punched fragmented magnetic sheets were laminated by bonding them together so as to have the same height as the height of the wound core of the corresponding example to obtain a magnetic core. Regarding the obtained magnetic core, the area ratio of the magnetic material in the cross section parallel to the lamination direction was measured and confirmed to be 75%.

[0112] The wound core and the laminated core produced in the same cylindrical shape using the same soft magnetic thin strip and the same resin as each other were regarded as corresponding magnetic cores to each other. For example, in each sample shown in Table 1 and Tables 6 to 21, the wound core and the laminated core with the same sample number except for the presence or absence of L were regarded as corresponding magnetic cores to each other.

[0113] <Evaluation of Magnetic Core> The magnetic properties of the magnetic core (the wound core in the example and the laminated core in the comparative example) were evaluated by measuring the magnetic properties of the magnetic component (coil component) obtained by winding a conductor in the direction shown in FIG. 1. That is, the magnetic properties of the magnetic component obtained by winding a conductor along the circumferential direction of the wound portion included in the magnetic core were measured and evaluated.

[0114] The inductance was measured at a frequency of 100 kHz using an LCR meter. The results are shown in Table 1. Note that the inductance shown in Table 1 is the value obtained by dividing the measured value of the inductance by the square of the number of turns N of the conductor. It is known that the inductance is proportional to the square of the number of turns N. Therefore, by comparing the values obtained by dividing the inductance by the square of N, the inductance can be evaluated on the same basis even when the number of turns of the conductors is different from each other.

[0115] The core loss was measured at room temperature using a BH analyzer at a measurement frequency of 100 kHz and a maximum magnetic flux density of 200 mT. The results are shown in Table 1.

[0116] The inductance of the wound core was considered good when the inductance was 10 nH / N 2 or more, and equal to or higher than the inductance of the corresponding laminated core. The inductance was considered even better when it was 10 nH / N 2 or more and 4% or higher than the inductance of the corresponding laminated core. The core loss of the wound core was considered good when it was 2% or lower than the core loss of the corresponding laminated core, and even better when it was 10% or lower.

[0117]

Table 1

[0118] From Table 1, when the average crack interval is 0.015 mm or more and 1.000 mm or less, and A / B is 0.100 or less, comparing the corresponding wound core and laminated core with each other, the area ratio of the magnetic material is higher in the wound core. And the inductance and core loss of the wound core are better than those of the corresponding laminated core.

[0119] On the other hand, when A / B exceeds 0.100, it becomes difficult to increase the area ratio of the magnetic material in the wound core. And the inductance of the wound core with a reduced area ratio of the magnetic material rather decreased compared with the inductance of the laminated core.

[0120] (Experimental Example 2) For sample numbers 1 to 4 of Experimental Example 1, wound cores were produced by changing only the average crack interval (A), and the inductance and core loss were measured. That is, in Experimental Example 2, OD is 18 mm and ID is 9.0 mm. The results are shown in Table 2.

[0121] [Table 2]

[0122] From Table 2, when the average crack interval was changed in the range of 0.015 mm or more and 1.000 mm or less, it was confirmed that the larger the average crack interval, the larger the inductance and the larger the core loss. Also, for sample number 21 where the average crack interval was too small, the inductance was too small to be accurately measured.

[0123] In addition, in each example of Table 2, corresponding laminated cores were produced and the characteristics were compared. As a result, in all examples, it was confirmed that the inductance was larger than that of the corresponding laminated core and the core loss was 2% or less and small.

[0124] (Experimental Example 3) The average crack interval (A) was fixed at 0.200 mm, and the outer diameter OD, inner diameter ID, and inner circumference (B) were appropriately changed to produce wound cores, and the inductance and core loss were measured. The results are shown in Table 3. Furthermore, the average crack interval (A) was fixed at 0.100 mm, and the outer diameter OD, inner diameter ID, and inner circumference (B) were appropriately changed to produce wound cores, and the inductance and core loss were measured. The results are shown in Table 4. In Experimental Example 3, the height of the wound core was 5 mm.

[0125]

Table 3

[0126]

Table 4

[0127] From Tables 3 and 4, when the outer diameter and the average crack interval (A) are fixed and the inner diameter and the inner circumference (B) are changed, the inductance increases as the inner diameter and the inner circumference become smaller and A / B becomes larger, but the core loss also tends to increase. The inner circumference was changed to vary A / B within the range of 0.100 or less.

[0128] In each example of Tables 3 and 4, the corresponding laminated cores were fabricated and their characteristics were compared. As a result, it was confirmed that in all examples, the inductance was larger than that of the corresponding laminated core, and the core loss was 2% or more and small. As an example, Table 3 shows the results of the laminated cores of sample numbers 41, 45, 48 and their corresponding sample numbers 41L, 45L, 48L. Table 4 shows the results of the laminated cores of sample numbers 51, 55, 58 and their corresponding sample numbers 51L, 55L, 58L.

[0129] (Experimental Example 4) Regarding sample number 3 in Experimental Example 1, by changing the amount of resin used, the area ratio of the magnetic material in the winding part was changed to fabricate a wound core, and the inductance and the core loss were measured. The results are shown in Table 5. Each example in Table 5 has a laminated core corresponding to the laminated core of sample number 3L.

[0130]

Table 5

[0131] From Table 5, it was confirmed that even when the area ratio of the magnetic material was changed, the inductance was equal to or greater than that of the corresponding laminated core (sample number 3L), and the core loss was small. In particular, when the area ratio of the magnetic material in the winding part was 79% or more and 96% or less, the inductance and core loss were further improved.

[0132] (Experimental Example 5) (Sample numbers 71, 71L) For sample numbers 3 and 3L, the experiment was carried out under the same conditions except that the composition of the soft magnetic ribbon was changed and no heat treatment was performed, and the average crack interval was changed. The fine structure of each ribbon was confirmed by observation using X-ray diffraction measurement (XRD) and transmission electron microscope (TEM). It was confirmed that each ribbon had a structure composed of amorphous without Fe-based nanocrystals. The results are shown in Table 6.

[0133] (Sample numbers 72 to 77, 72L to 77L) The composition of the soft magnetic ribbon was the same as that of sample numbers 3 and 3L, but the heat treatment conditions were changed to change the average particle size of the Fe-based nanocrystals. Other points were carried out under the same conditions as sample numbers 3 and 3L. The results are shown in Table 6.

[0134]

Table 6

[0135] From Table 6, it was confirmed that even when the composition and fine structure of the soft magnetic ribbon were changed, the inductance of the wound core in each example was larger and the core loss was smaller than that of the corresponding laminated core.

[0136] (Experimental Example 6) The experiment was carried out under the same conditions as sample numbers 3 and 3L, except that the composition of the soft magnetic ribbon was further changed. It was confirmed that all the soft magnetic ribbons used in Experimental Example 6 had a structure composed of Fe-based nanocrystals. The average particle size of the Fe-based nanocrystals varied depending on the composition, but it was confirmed that the average particle size of any soft magnetic ribbon was 5 nm or more and 50 nm or less. The results are shown in Tables 7 to 21.

[0137]

Table 7

[0138]

Table 8

[0139]

Table 9

[0140]

Table 10

[0141]

Table 11

[0142]

Table 12

[0143]

Table 13

[0144]

Table 14

[0145]

Table 15

[0146]

Table 16

[0147]

Table 17

[0148]

Table 18

[0149]

Table 19

[0150]

Table 20

[0151]

Table 21

[0152] From Tables 7 to 21, it was confirmed that even when the composition of the soft magnetic thin strip was changed, the inductance of the wound core in each example was larger and the core loss was smaller than that of the corresponding laminated core.

Explanation of Reference Signs

[0153] 1 ··· Wound core (magnetic core) 11, 11a to 11c ··· Winding part 21 ··· Conductor 101 ··· Support sheet 103 ··· Adhesive layer 105 ··· Soft magnetic thin strip 201 ··· Support sheet roll 203 ··· Adhesive application nozzle 205 ··· Thin strip roll 207 ··· Laminating roller 209 ··· Fragmenting roller 211 ··· Take-up roll 213 ··· Cutting device 215 ··· Tension adding roller 217 ··· Stabilizing roller B ··· Virtual line C... Crack D... Intersection

Claims

1. A wound core having a wound portion formed by winding a soft magnetic ribbon, wherein the wound portion includes an adhesive layer that contacts a main surface of the soft magnetic ribbon, the soft magnetic ribbon has pieces separated by cracks, and an average crack interval indicating an average of intervals between the cracks is 0.015 mm or more and 1.000 mm or less, and the average crack interval is 1 / 10 or less of an inner peripheral length of the wound portion. The wound core.

2. The wound core according to claim 1, wherein in a cross section perpendicular to a winding axis of the soft magnetic ribbon, an area ratio of a magnetic material in the wound portion is greater than 75% and less than 97%.

3. A structure composed of an Fe-based nanocrystal is observed in the soft magnetic ribbon, The wound core according to claim 1 or 2, wherein an average particle diameter of the Fe-based nanocrystal is 5 to 30 nm.

4. A magnetic component including the wound core according to claim 1 or 2 and a conductor.

5. A method for manufacturing a wound core, the method including: a step of forming an adhesive layer on at least one main surface of a soft magnetic ribbon; a step of fragmenting the soft magnetic ribbon on which the adhesive layer is formed; and a step of winding the fragmented soft magnetic ribbon.

6. The method for manufacturing a wound core according to claim 5, wherein the adhesive layer is formed on a surface of a support sheet, the soft magnetic ribbon is formed on a surface of the adhesive layer, and then the soft magnetic ribbon is fragmented on the support sheet.

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