Patent Application
20180197666
The present invention relates to a soft magnetic material, a core, and an inductor.
Recently, the electronic devices have attained a high density assembly and also a faster processing, and along with this the inductor is also demanded to have a smaller size while having higher output. However, because of this downsizing, the volume of the core (the core made of a magnetic material) of the inductor decreases which tends to cause a decrease of an inductance and the deterioration of DC superimposition characteristic (the inductance when applying DC current).
Therefore, the core which does not cause the decrease of the inductance and the deterioration of DC superimposition characteristic even in case the inductor is downsized, that is the soft magnetic material having excellent high permittivity and DC superimposition characteristic is in demand.
As the invention relating to the conventional soft magnetic material, for example a soft magnetic material, a core, and an inductor disclosed in the patent document 1 are known. Said soft magnetic material includes a resin, a first soft magnetic metal powder having a particle size of 20 μm or more and 50 μm or less, and a second soft magnetic metal powder having a particle size of 1 μm or more and 10 μm or less, wherein said first and second soft magnetic metal powders are insulation coated. Further, when a ratio between a mass % of the first soft magnetic metal powder and a mass % of the second soft magnetic metal powder is A:B, then “A” and “B” satisfies A+B=100, and 15≤A≤35 and 65≤B≤85.
[Patent document 1] JP Patent Application Laid Open No. 2014-204108
The patent document 1 discloses the constitution wherein the ratio of the second soft magnetic metal powder which is the fine powder having the particle size of 1 μm or more and 10 μm or less is larger than the ratio of the first soft magnetic metal powder which is the coarse powder having the particle size of 20 μm or more and 50 μm or less. Therefore, the filling rate of the soft magnetic material was unable to increase sufficiently. The core having the same constitution as disclosed in the patent document 1 was produced, only to confirm that it was not sufficient enough to attain high permittivity and good DC superimposition characteristic which can satisfy the current needs of downsizing.
Thus, the present invention was attained in view of such circumstances, and the object is to provide the soft magnetic material, the core, and the inductor having high permittivity and excellent DC superimposition characteristic.
The soft magnetic material of the present invention includes a soft magnetic metal powder and a resin, wherein said soft magnetic metal powder is composed of a particle group α and a particle group β, when IA is a peak intensity of the particle group α, IB is a peak intensity of the particle group β, and IC is a minimum intensity present between the particle group α and the particle group β, then an intensity ratio IC/IA satisfies 0.10 or less and an intensity ratio IA/IB satisfies 1.2 or more and 3.0 or less. Note that, the particle group α is the particle group having a maximum peak intensity in a size distribution of said soft magnetic metal powder, the particle group β is the particle group having a peak intensity which is the second largest to the particle group α, and a peak particle size PA of the particle group α is larger than a peak particle size PB of the particle group β.
That is, the particles having the intermediate particle size which falls between the particle group α and the particle group β are little. Therefore, the small size particles of the particle group β can be efficiently filled into the space formed between the large size particles of the particle group α. Also, the filling rate of the soft magnetic particles which is the sum of the particle group α and the particle group β can be increased. It is thought that a high permittivity and a good DC superimposition characteristic can be attained as a result of this. However, the effect is not limited to this.
Preferably, the peak particle size PA of said particle group α is 60 μm or less. By having the peak particle size PA of said particle group α within the above mentioned range, DC superimposition characteristic improves, and forms the compositional state wherein the resin part and the space part are rarely localized. Thereby, the composition of the sample is speculated to be uniform. Note that, the effect is not limited to this.
Preferably, the soft magnetic metal powder constituting said particle group α is Fe or a metal comprising Fe, and the soft magnetic metal powder is coated with an insulation material. By using Fe or the metal including Fe with high saturation magnetization, high permittivity and good DC superimposition characteristic tends to be attained. Also, by coating with the insulation material, good DC superimposition characteristic tends to be attained. Note that, “by coating” means to coat part of or entire particle.
The core according to one embodiment of the present invention is produced by said soft magnetic material.
The inductor according to one embodiment of the present invention includes said core.
According to the present invention, the soft magnetic material, the core, and the inductor having a high permittivity and an excellent DC superimposition characteristic can be provided.
Hereinafter, the embodiment of the present invention will be described, however the present invention is not to be limited thereto. Also, the constitution of the embodiment described in below includes those which can be easily attained by ordinary skilled in the art, those which is substantially the same, and those which is within the equivalent range.
The soft magnetic material of the present embodiment includes a soft magnetic metal powder and a resin, wherein said soft magnetic metal powder is comprised of a particle group α and a particle group β, when IA is a peak intensity of the particle group α, IB is a peak intensity of the particle group β, and IC is a minimum intensity present between the particle group α and the particle group β, then an intensity ratio IC/IA satisfies 0.10 or less and an intensity ratio IA/IB satisfies 1.2 or more and 3.0 or less. Note that, the particle group α is the particle group having a maximum peak intensity in a size distribution of said soft magnetic metal powder, the particle group β is the particle group having an peak intensity which is the second largest to the particle group α, and a peak particle size PA of the particle group α is larger than a peak particle size PB of the particle group β. Further, the point having the minimum intensity IC between the group α and the particle group β is “C”, and the particle size of “C” is defined “PC”.
The peaks “A”, “B”, and the point “C” can be determined from the size distribution based on a volume which is calculated using a laser diffraction scattering method; and from the peak and the point thereof, the peak particle size PA and PB, the peak intensity IA and IC, the particle size PC of the point C, and the intensity IC can be calculated.
The intensity ratio IC/IA is the value which is round off to the second decimal place. The intensity ratio IC/IA is preferably 0.01 or more and 0.08 or less, and more preferably 0.01 or more and 0.06 or less. When the intensity ratio IC/IA is small, high filling rate tends to be obtained, but when it is 0.003 or less, the filling rate tends to decrease.
The intensity ratio IA/IB is preferably 1.2 or more and 2.5 or less, more preferably 1.3 or more and 2.4 or less, and further preferably 1.5 or more and 2.0 or less. By having such constitution, the filing rate tends to be high, and the deterioration of DC superimposition characteristic tends to be suppressed from deteriorating.
The peak particle size PA of the particle group α is preferably 60 μm or less. When the peak particle size PA becomes large, DC superimposition characteristic tends to deteriorate; and when the peak particle size PA becomes small, then the permittivity tends to decrease. From the point of the permittivity and DC superimposition characteristic, the peak particle size PA of the particle group α is preferably 10 to 60 more preferably 15 to 60 further preferably 20 to 55 The peak particle size of the powder used for the particle group α can regulate the size distribution by removing the coarse particle and the fine particle using a classifier.
As the particle of the particle group α, the particle produced by an atomization method such as a water atomization method or a gas atomization method can be used. Generally, the particle with higher roundness can be easily obtained using the gas atomization method, however the particle having a high roundness can be obtained by appropriately regulating the spray condition or so even in case of using the water atomization method.
The soft magnetic metal powder constituting the particle group α is preferably Fe or the metal (including alloy) including Fe, and the surface is preferably coated with the insulation material. As the metal including Fe, an amorphous alloy of Fe—B—Si—Cr based, Fe—Si—Cr based, Fe—Ni—Si—Co based, and Fe—Si—B—Nb—Cu based may be mentioned. Also, as the insulation material for coating, any coating material may be selected from phosphate glass; a compound including one or more selected from the group consisting of MgO, CaO, and ZnO; a mixed boron compound made from aqueous solution or water dispersion including boron; titanium oxide made from titanium alkoxides; and silicon oxides or so.
Also, as the soft magnetic metal powder constituting the particle group α, plurality of metal particles may be mixed and used. For example, the surface of the particle made of Fe and the surface of the particle made of Fe—B—Si—Cr based amorphous alloy which are insulation coated with boron compound can be mixed and used; and the particle made of Fe—B—Si—Cr based amorphous alloy of which the surface is the insulation coated with boron compound can be mixed with the particle made of Fe and used.
Form the point of improving the filling rate of the soft magnetic metal particle, the peak particle size PB of the particle group β is preferably 0.5 μm to 5 μm, more preferably 0.7 μm to 4 μm, and further preferably 0.7 μm to 2 μm. The peak particle size of the powder used for the particle group β can be set to have a desirable peak particle size by regulating the size distribution by removing the coarse particle and the fine particle using the classifier.
As the particle of the particle group β, the particle produced by the atomization method such as the water atomization method or the gas atomization method similar to the particle group α, also several μm particle produced by a carbonyl method and submicron particle produced by the spray pyrolysis method or so can be used.
As the soft magnetic metal powder constituting the particle group β, Fe or the metal (including alloy) including Fe can be used, and the composition may differ from the particle group α. As the metal including Fe, for example Fe—Ni based alloy may be mentioned. Regarding the particle group β, the particle of which the surface is coated with the insulation material can be used as similar to the particle group α. As the insulation material, any coating material such as mentioned in the above can be selected.
Also, as the soft magnetic metal powder constituting the particle group β, plurality of metal particles may be mixed and used as similar to the above mentioned particle group α.
For the soft magnetic material of the present embodiment, the insulation between the soft magnetic particles is maintained by the resin. However, by using the powder carried out with the insulation treatment to the surface of the soft magnetic particle, higher insulation property and better DC superimposition characteristic can be attained, and when used as the inductor, further preferable insulation property, the voltage resistance, and DC superimposition characteristic can be attained.
Also, the soft magnetic material of the present embodiment preferably includes 65 to 83 wt % of the particle of the particle group α, 15 to 30 wt % of the particle of particle group β, and 1.5 to 5 wt % of the resin. By constituting as such, the resin can fill between the particle of the particle group α and the particle of particle group β; thereby the space can be decreased.
As the resin, for example various organic polymer resins such as a silicone resin, a phenol resin, an acrylic resin, and an epoxy resin or so may be mentioned, but it is not limited thereto. These can be used alone or by combining two or more. Further, if necessary, known curing agent, crosslinking agent, and lubricant or so may be blended. Also, a liquid form resin, or a resin dissolved in an organic solvent may be used, but the epoxy resin of liquid form is preferable.
On the other hand, the soft magnetic material of the present embodiment is preferably used as the paste capable of print coating or so, and if necessary, the viscosity of the paste may be regulated by a solvent or a dispersant.
The core of the present embodiment can be produced by filling the paste including the above mentioned soft magnetic material to the mold of any shape, and then carrying out the heat curing. If a volatile component such as the solvent or so is included, it can be dried to a semi-cured condition, then the pressure is applied, followed by heat curing thereby the core can be produced. Note that, the particle size of the soft magnetic metal powder during the production of the core does not change, hence when the soft magnetic material is a core, the particle group α and the particle group maintain the size distribution of the soft magnetic material mentioned in above.
The core of the present embodiment can be used to various types of the inductor such as a thin film inductor, a multilayer inductor, a coil inductor or so. As one example, the constitution of the thin film inductor is shown.
Next, the production method of the thin film inductor as an example of the inductor will be described.
The internal electrode of a spiral shape is formed to the top and bottom faces of the resin substrate by the spattering method or a photolithography method. Further, the soft magnetic material of a paste form of the present embodiment is printed to said substrate face to form the magnetic layer, then heat curing is carried out at the temperature of 150 to 200° C. Thereby, the base substrate formed with plurality of the internal electrodes of the spiral form is obtained. This base substrate is formed with plurality of the internal electrode patterns, and then it is cut into individual chip via a cutting step using a slicer. Then, a barrel polishing or so is carried out so that the internal electrode and the external electrode can be connected easily. The chip obtained as such is fixed such that the face where the internal electrode is exposed is facing up, and then the external electrode is formed via a thinning step such as spattering or so. Further, the thin film inductor can be produced by going through the step of nickel plating and tin plating to the external electrode surface.
Hereinafter, the present invention will be described based on the examples and the comparative examples; however the present invention is not to be limited to the examples.
As the powder of the particle group α, the powder having the peak particle size of 10.1 μm wherein the surface is insulation coated with phosphate glass, and made of Fe-2.4 mass % of B-6.4 mass % of Si-2.1 mass % of Cr based amorphous alloy produced by the water atomization method was prepared. Further, as the powder of the particle group β, the powder having the peak particle size of 0.5 μm made of iron powder produced by the spray pyrolysis method was prepared. The powder of the particle group β and the powder of the particle group α were blended in the weight ratio of 1:3, thereby the soft magnetic metal powder of the example 1 having the peak particle size shown in Table 1 was obtained. Next, 2.5 wt % of liquid epoxy resin was added, and thoroughly kneaded while regulating the viscosity by adding the organic solvent, thereby the soft magnetic material of a paste form of the example 1 was obtained. Further, the soft magnetic material of a paste form was filled into the mold having a groove of a toroidal shape, then this was dried to a semi-dried state and the pressure was applied. Then it was taken out of the mold, and the heat curing was carried out in the thermostat chamber, thereby the core of the example 1 of a toroidal shape having the outer diameter of 15 mm, the inner diameter of 9 mm, and the thickness of 0.7 mm was obtained.
Note that, the above mentioned “Fe-2.4 mass % of B-6.4 mass % of Si-2.1 mass % of Cr” means that when the total is 100 mass %, B was 2.4 mass %, Si was 6.4 mass %, and Cr was 2.1 mass %, and the rest was Fe. For the examples hereinafter, the same applies.
The soft magnetic powder, the soft magnetic material, and the core of the example 2 were obtained as same as the example 1 except for using the powder having the peak particle size of 18.5 μm as the powder of the particle group α, and using the powder having the peak particle size of 0.9 μm and made of carbonyl iron powder produced by a carbonyl method was used as the powder of the particle group β.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 3 were obtained as same as the example 1 except for using the powder having the peak particle size of 24.0 μm as the powder of the particle group α, and using the powder having the peak particle size of 1.3 μm and made of carbonyl iron powder produced by a carbonyl method was used as the powder of the particle group β.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 4 were obtained as same as the example 3 except for blending the powder of the particle group β and the particle group α in a weight ratio of 1:4. Also, the soft magnetic metal powder, the soft magnetic material, and the core of the example 5 were obtained as same as the example 3 except for blending the powder of the particle group β and the particle group α in a weight ratio of 1:2.3.
The soft magnetic metal powder, the soft magnetic material, and the core of the examples 6, 7, 8, 14, 15, and 16 were obtained as same as the example 3 except for using the powder having peak particle size of 34.0, 44.0, 52.3, 57.1, 62.2, and 80.7 μm respectively as the powder of the particle group α.
The soft magnetic metal powder, the soft magnetic material, and the core of the examples 9, 10, 12, 13, and the comparative examples 4 and 5 were obtained as same as the example 8 except for blending the powder of the particle group β and the particle group α in a weight ratio of 1:4, 1:4.5, 1:2.3, 1:2, 1:5, and 1:1.5 respectively.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 11 were obtained as same as the example 9 except for using the powder having the peak particle size of 3.3 μm as the powder of the particle group β.
The soft magnetic metal powder, the soft magnetic material, and the core of the comparative example 1 were obtained as same as the example 3 except for using the powder having the peak particle size of 18.5 μm as the powder of the particle group α.
The soft magnetic material and the core of the comparative example 2 were obtained as same as the example 1 except for only using the powder having the peak particle size of 1.3 μm and made of carbonyl iron powder produced by a carbonyl method as the soft magnetic metal powder.
The soft magnetic material and the core of the comparative example 3 were obtained as same as the example 1 except for only using the powder having the peak particle size of 52.3 μm which the surface was insulation coated by phosphate glass, and made of Fe—B—Si—Cr based amorphous alloy of sphere shape produced by the water atomization method as the soft magnetic metal powder.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 17 were obtained as same as the example 1 except for the conditions shown in below. That is, in the example 17, as the powder of the particle group α, the powder having the peak particle size of 52.3 μm made of Fe-2.5 mass % of B-6.4 mass % of Si-2.1 mass % of Cr based amorphous alloy of spherical shape produced by the water atomization method was prepared. Further, as the powder of the particle group β, the powder having the peak particle size of 1.3 μm made of carbonyl iron powder produced by the carbonyl method was prepared. The powder of the particle group β and the powder of the particle group α were blended in the weight ratio of 1:4.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 18 were obtained as same as the example 17 except for the powder having the peak particle size of 26.0 μm wherein the surface is insulation coated with silica, and made of Fe-2.5 mass % of B-6.4 mass % of Si-2.1 mass % of Cr based amorphous alloy of spherical shape produced by the water atomization method was used as the powder of the particle group α.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 19 were obtained under the same condition as the example 17 except for the powder having the peak particle size of 48.0 μm wherein the surface is insulation coated with phosphate glass, and made of Fe-6.5 mass % of Si-2.5 mass % of Cr based amorphous alloy of spherical shape produced by the water atomization method was used as the powder of the particle group α.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 20 were obtained as same as the example 17 except that the powder having the peak particle size of 26.0 μm wherein the surface is insulation coated with phosphate glass, and made of Fe-44 mass % of Ni-2.1 mass % of Si-4.5 mass % of Co based amorphous alloy of spherical shape produced by the water atomization method was used as the powder of the particle group α.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 21 were obtained as same as the example 17 except for the conditions shown in below. That is, in the example 21, as the powder of the particle group α, the powder having the peak particle size of 24.0 μm which the surface was insulation coated with phosphate glass, and made of Fe—13.0 mass % of Si—9.0 mass % of B—3.0 mass % of Nb—1.0 mass % of Cu based amorphous alloy of spherical shape produced by the water atomization method was prepared. The powder of the particle group β and the powder of the particle group α were blended in the weight ratio of 1:3.5.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 22 were obtained as same as the example 17 except for the conditions shown in below. That is, in the example 22, as the powder of the particle group α, the powder having the peak particle size of 52.3 μm wherein the surface is insulation coated with phosphate glass, and made of Fe-2.5 mass % of B-6.4 mass % of Si-2.1 mass % of Cr based amorphous alloy produced by the water atomization method was prepared. Further, as the powder of the particle group β, the powder having the peak particle size of 1.4 μm made of carbonyl iron powder produced by the carbonyl method was prepared. The powder of the particle group β and the powder of the particle group α were blended in the weight ratio of 1:3.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 23 were obtained as same as the example 22 except that the powder having the peak particle size of 0.8 μm which the surface is insulation coated with silica, and made of Fe-50 mass % of Ni based alloy produced by the spray pyrolysis method was used as the powder of the particle group β.
The soft magnetic metal powder, the soft magnetic material, and the core of the example 24 were obtained as same as the example 17 except for the powder having the peak particle size of 44.0 μm made of Fe of spherical shape produced the water atomization method was used as the powder of the particle group α.
The size distribution measuring method, the measuring condition of the filling rate of the soft magnetic metal powder, the permittivity and DC superimposition characteristic of the core having the toroidal shape were as described in below.
The powder, water, and the dispersant were introduced in the homogenizer (made by Nippon Seiki Co., Ltd.) and dispersed. Then, the peak A, the peak B, and the minimum C were determined by the size distribution based on a volume obtained by a wet laser diffraction particle size distribution analyzer (Microtrac MT3300EXII made by Nikkiso Co., Ltd.). Then, the peak particle size PA and PB, the peak intensity (frequency) IA and IB, the particle size PC of the minimum C, and the intensity (frequency) IC were calculated. Note that, when the same size distribution measurement was carried out to the soft magnetic metal powder included in the obtained soft magnetic material and the core, the same size distribution as the soft magnetic metal powder before being used to the soft magnetic material and the core was obtained.
The density was measured by Archimedes method using the core having the toroidal shape, and then the filling rate was obtained by the specific gravity of various materials.
Size of the core having the toroidal shape: outer diameter of 15 mm×inner diameter of 9 mm×thickness of 0.7 mm
Measuring device: E4991A (made be Aglient) RF impedance/Material analyzer
Measuring frequency: 3 MHz
Size of the core having the toroidal shape: outer diameter of 15 mm×inner diameter of 9 mm×thickness of 0.7 mm
Number of coils: 30
Measuring device: 4284A (made be Aglient) Precision LCR meter
Frequency of high frequency signal: 100 kHz
DC superimposition characteristic was evaluated based on the decreasing rate of the inductance when DC bias current was applied from 0 A to 10 A.
Table 1 shows the peak particle size PA and PB of the particle group α and the particle group β calculated from the size distribution measurement, the peak intensity IA and IB, the minimum intensity IC, the intensity ratio IC/IA and IA/IB, and the filling rate, the permittivity, and the inductance decreasing rate of the soft magnetic powder measured from the core having the toroidal shape.
The examples 1 to 24 shown in Table 1 all satisfied the condition of the intensity ratio of IC/IA of 0.10 or less and the intensity ratio IA/IB of 1.2 or more and 3.0 or less, also the examples 1 to 24 exhibited high permittivity of more than 30.
According to Table 1, the comparative examples 1, 4, and 5 did not satisfy the condition of the intensity ratio of IC/IA of 0.10 or less and the intensity ratio of IA/IB of 1.2 or more and 3.0 or less. Further, the comparative examples 1, 4, and 5 had low filling rate of the soft magnetic metal powder, and the permittivity was less than 30. Particularly, as shown in the comparative examples 2 and 3, when the sample only has the particle group α and has single size distribution, then the filling rate of the soft magnetic metal powder of the toroidal core cannot exceed 70 vol %, and the permittivity at 3 MHz was 20 or less.
The examples 3, 6 to 8, 21, and 22 exhibited the intensity ratio IC/IA of 0.01 or more and 0.06 or less, the intensity ratio of IA/IB of 1.5 or more and 2.0 or less, the filling rate larger than 80 vol %, and the permittivity of more than 39 which is high. The examples 3, 6 to 8, 21, and 22 exhibited good DC superimposition characteristic, and the inductance decreasing rate was 33% or less.
The examples 15 and 16 of which the peak particle size PA of the particle group α was larger than 60 μm exhibited relatively large specific permittivity as shown in Table 1, but the inductance decreasing rate was larger than 40%, and also exhibited the deterioration of DC superimposition characteristic. However, when the peak particle size PA of the particle group α was 60 μm or less, then relatively good DC superimposition characteristic was obtained. The cause of the deterioration of DC superimposition characteristic is thought to be largely influenced by unevenness of the composition in the sample. This is because, when the peak particle size PA of the particle group α becomes larger, the space in the samples tends to enlarge as well, and thus it is speculated that the composition is at the state that the distribution of the resin part and the space part easily localize.
Note that, for the representative samples of the soft magnetic material shown in Table 1, the size distribution of the sample thereof are shown in
The soft magnetic material of the present invention has high permittivity and excellent DC superimposition characteristic, thus it can be widely used for inductor, electric and magnetic device such as various trances; and devices, equipment and systems or so which includes those.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-003003 | Jan 2017 | JP | national |
| 2017-229172 | Nov 2017 | JP | national |
