Coil component

Abstract

A coil component is constituted by a composite magnetic material containing alloy grains whose oxygen atom concentration in their surfaces is 50 percent or less, and resin, and also by a coil. The coil component using the composite magnetic material does not require high pressure when formed.

Claims

1. A coil component constituted by a composite magnetic material containing alloy grains and resin and also by a coil, which composite magnetic material is substantially non-compressed, wherein an oxygen atom concentration in a surface of the alloy grains is 50 percent or less and at least about 30 percent as measured by secondary ion mass spectrometry, and the alloy grains have a size of at least 1 m and are composed of amorphous alloy grains containing 77 to 79.5 percent by weight of Fe and/or crystalline alloy grains containing 92.5 to 95.5 percent by weight of Fe.

2. A coil component according to claim 1, wherein the coil is embedded in the composite magnetic material.

3. A coil component according to claim 1, wherein the coil is formed inside the composite magnetic material.

4. A coil component according to claim 1, wherein an average grain size of the alloy grains is 2 to 20 m.

5. A coil component according to claim 4, wherein the alloy grains have a grain size distribution which shows two peaks.

6. A coil component according to claim 1, wherein the amorphous alloy grains further contains 5 to 10 percent by weight of at least one metal selected from the group consisting of Si, Al, Cr, Ni, Mo, and Co.

7. A coil component according to claim 1, wherein the crystalline alloy grains further contains 5 to 10 percent by weight of at least one metal selected from the group consisting of Si, Al, Cr, Ni, Mo, and Co.

8. A coil component according to claim 1, wherein the alloy grains having an oxygen atom concentration of 50% or less in their surfaces account for 80 percent by volume or more in equivalent volume percentage, among all of the alloy grains contained in the composite magnetic material.

9. A coil component according to claim 1, wherein the alloy grains contain at least amorphous alloy grains.

10. A coil component according to claim 1, wherein the oxygen atom concentration is 30 to 40 percent.

11. A coil component according to claim 10, wherein the coil is embedded in the composite magnetic material.

12. A coil component according to claim 10, wherein the coil is formed inside the composite magnetic material.

13. A coil component according to claim 10, wherein the alloy grains having an oxygen atom concentration of 30% to 40% in their surfaces account for 80 percent by volume or more in equivalent volume percentage, among all of the alloy grains contained in the composite magnetic material.

Description

EXAMPLES

(1) The present invention is explained more specifically below using examples. It should be noted, however, that the present invention is not limited to the embodiments described in these examples.

Example 1

(2) A coil component was manufactured as follows.

(3) Product size: 2.52.01.2 mm

(4) Minimum thickness of magnetic body: 0.25 mm

(5) Metal magnetic grains: FeSiCr (Powder of 15 m in average grain size was produced in air according to the water atomization method by mixing Fe, Si, and Cr at a ratio of 92.5 percent by weight, 4 percent by weight, and 3.5 percent by weight, respectively, and the produced powder was heat-treated for one hour in a reducing ambience of 500 C. The resulting metal magnetic grains are referred to as crystalline alloy grains c.)

(6) Resin: Epoxy resin, 3 percent by weight

(7) Hollow coil: Rectangular wire with polyimide sheath (0.30.1 mm), -wound by 9.5 turns

(8) Forming: The hollow coil was placed in a metal mold, and the composite magnetic material was poured into the metal mold that had been heated to 150 C., and then temporarily cured, to form the magnetic body.

(9) Curing: The temporarily cured magnetic body was taken out of the metal mold and cured at 200 C.

(10) Terminal electrodes: The magnetic body was polished to expose the ends of the hollow coil, which were then given Ag sputtering and then coated with Ag-containing conductive paste and plated with Ni and Sn.

(11) The above procedure was carried out as follows.

(12) The coil was produced and placed in the metal mold in a manner aligning the center of the mold with the center of the hollow coil. The composite magnetic material prepared beforehand by mixing the metal magnetic grains and resin was heated to 150 C., and this 150 C.-hot composite magnetic material was poured into the metal mold to obtain the base of magnetic body. Thereafter, the resin was cured further at 200 C. to obtain the magnetic body. This magnetic body was processed as necessary (cut, polished and rust-proofed) and eventually the terminal electrodes were formed to obtain the coil component. The molding pressure used here was 15 MPa, which is very low compared to the pressures traditionally used.

Comparative Example 1

(13) A coil component was obtained in the same manner as in Example 1, except that FeSiCr that had not been given the heat treatment in a reducing ambience was used for the metal magnetic grains. The resulting metal magnetic grains are referred to as crystalline alloy grains a.

Comparative Example 2

(14) A coil component was obtained in the same manner as in Example 1, except for the metal magnetic grains. For the metal magnetic grains, FeSiAlCr powder of 15 m in average grain size was produced in air according to the water atomization method by mixing Fe, Si, Al, and Cr at a ratio of 90 percent by weight, 5 percent by weight, 4 percent by weight, and 1 percent by weight, respectively, and the produced powder was heat-treated for one hour in a reducing ambience of 500 C. The resulting metal magnetic grains are referred to as crystalline alloy grains b.

Comparative Example 3

(15) A coil component was obtained in the same manner as in Example 1, except for the metal magnetic grains. For the metal magnetic grains, FeSiCrBC powder of 15 m in average grain size was produced in air according to the water atomization method by mixing Fe, Si, Cr, B, and C at a ratio of 70 percent by weight, 8 percent by weight, 5 percent by weight, 15 percent by weight, and 2 percent by weight, respectively. The resulting metal magnetic grains are referred to as amorphous alloy grains d.

Example 2

(16) A coil component was obtained in the same manner as in Example 1, except for the metal magnetic grains. For the metal magnetic grains, FeSiCrBC powder of 15 m in average grain size was produced in air according to the water atomization method by mixing Fe, Si, Cr, B, and C at a ratio of 77 percent by weight, 6 percent by weight, 4 percent by weight, 13 percent by weight, and 2 percent by weight, respectively. The resulting metal magnetic grains are referred to as amorphous alloy grains e.

Example 3

(17) A coil component was obtained in the same manner as in Example 1, except for the metal magnetic grains. For the metal magnetic grains, FeSiBC powder of 15 m in average grain size was produced in air according to the water atomization method by mixing Fe, Si, B, and C at a ratio of 79.5 percent by weight, 5 percent by weight, 13.5 percent by weight, and 2 percent by weight, respectively. The resulting metal magnetic grains are referred to as amorphous alloy grains f.

Example 4

(18) A coil component was obtained in the same manner as in Example 1, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and amorphous alloy grains e used in Example 2 prepared to a different average grain size of 10 m were mixed at a ratio of 6:4, respectively, for use as the composite magnetic material.

Example 5

(19) Here, a coil component was obtained using the same composite magnetic material used in Example 4, by changing the product height to 1.0 mm and the minimum thickness of the magnetic body to 0.2 mm.

Example 6

(20) A coil component was obtained in the same manner as in Example 5, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and amorphous alloy grains e used in Example 2 prepared to a different average grain size of 10 m were mixed at a ratio of 8:2, respectively, for use as the composite magnetic material.

Example 7

(21) A coil component was obtained in the same manner as in Example 5, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and amorphous alloy grains e used in Example 2 prepared to a different average grain size of 10 m were mixed at a ratio of 9:1, respectively, for use as the composite magnetic material.

Example 8

(22) A coil component was obtained in the same manner as in Example 5, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and amorphous alloy grains e used in Example 2 prepared to a different average grain size of 2 m were mixed at a ratio of 8:2, respectively, for use as the composite magnetic material.

Example 9

(23) A coil component was obtained in the same manner as in Example 5, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and amorphous alloy grains e used in Example 2 prepared to a different average grain size of 1.5 m were mixed at a ratio of 8:2, respectively, for use as the composite magnetic material.

Example 10

(24) A coil component was obtained in the same manner as in Example 5, except for the metal magnetic grains. For the metal magnetic grains, amorphous alloy grains f used in Example 3 and Fe grains (containing Fe by 99.6 percent by weight and impurities for the rest) of 1.5 m in average grain size were mixed at a volume ratio of 8:2, respectively, for use as the composite magnetic material.

(25) The SIMS measurement results of the metal magnetic grains contained in the composite magnetic materials are as follows:

(26) TABLE-US-00001 Oxygen atom Metal magnetic grains concentration in surface Crystalline alloy grains a 53% Crystalline alloy grains b 52% Crystalline alloy grains c 48% Amorphous alloy grains d 51% Amorphous alloy grains e 40% Amorphous alloy grains f 30% Fe grains 31%

(27) In the foregoing, the oxygen atom concentration in surface indicates the maximum value of oxygen atom concentration obtained by SIMS measurement as mentioned above (specifically the maximum value among the measurements taken at different etching times from 0 to 10 minutes in 1-minute increments).

(28) For each composite magnetic material, the SIMS measurement covered 20 grains.

(29) The averages of measured results are shown above.

(30) The fill ratio in the composite magnetic materials and the inductances of the coil components are as follows:

(31) TABLE-US-00002 Fill ratio Inductance Example 1 74.0 vol % 1.02 H Comparative Example 1 70.3 vol % 0.8 H Comparative Example 2 71.2 vol % 0.85 H Comparative Example 3 71.3 vol % 0.86 H Example 2 75.2 vol % 1.1 H Example 3 75.4 vol % 1.12 H Example 4 75.8 vol % 1.15 H Example 5 75.5 vol % 1.04 H Example 6 76.4 vol % 1.1 H Example 7 76.1 vol % 1.07 H Example 8 77.3 vol % 1.1 H Example 9 75.5 vol % 1.02 H Example 10 75.5 vol % 1.02 H

(32) In the foregoing, the fill ratio indicates the percentage of the area occupied by the metal magnetic grains in a section of the magnetic body based on microscopic image observation (the fill ratio is different from the amount of resin which refers to the amount of resin added when the composite magnetic material was manufactured).

(33) The inductance indicates the inductance value of the coil component at 1 MHz obtained using a LCR meter.

(34) All comparative examples resulted in a low fill ratio, suggesting defects (exposed conductive wire) due to insufficient filling around the coil. As a result, the electrical characteristics in all comparative examples were also lower than those in the examples, and were insufficient for a coil component. As is evident from these results, a magnetic body having thin parts could not be formed before. In the examples, on the other hand, a magnetic body of 0.25 mm, or even 0.2 mm, in thickness could be obtained without filling defects. Consequently, a smaller component can be produced with a level of thinness not heretofore achievable with powder compacting with high molding pressure.

Example 11

(35) In this example, a wire was wound around a drum core and a composite magnetic material was formed on the exterior of the winding.

(36) Product size: 2.52.01.2 mm

(37) Drum core: FeSiCr (Fe, Si, and Cr were mixed at a ratio of 90 percent by weight, 6 percent by weight, and 4 percent by weight, respectively, and the mixture was heat-treated in air for one hour.)

(38) Composite magnetic material: Amorphous alloy grains e above were used.

(39) Coil: Conductive wire with polyimide sheath (rectangular wire 0.30.1 mm), -wound by 9.5 turns

(40) Forming: The drum core with the winding was placed in a rubber mold, and the composite magnetic material was poured into the rubber mold and then temporarily cured to form the magnetic body.

(41) Curing: The temporarily cured magnetic body was taken out of the rubber mold and cured at 200 C.

(42) Terminal electrodes: The exterior surfaces of the flanges of the drum core were given Ti and Ag sputtering and then coated with Ag-containing conductive paste and plated with Ni and Sn.

(43) The above procedure was carried out as follows.

(44) The drum core was produced by forming and heat-treating the FeSiCr magnetic material. Next, terminal electrodes were formed on the exterior surfaces of the flanges of the drum core and the conductive wire wound externally around the shaft of the drum core was connected to the terminal electrodes. Lastly, the drum core with the winding was placed in a rubber mold and the composite magnetic material prepared beforehand by mixing the metal magnetic grains and resin was heated to 50 C. and molded on the exterior of the coil, after which the obtained coil component was taken out of the rubber mold and the resin was cured further at 200 C., to obtain the coil component. The molding pressure used here was 5 MPa, which is very low compared to the pressures traditionally used.

(45) When the coil component was evaluated in the same manner as described above, the measured inductance was 1.15 H and fill ratio was 74.5 percent by volume, indicating good current characteristics. This suggests that a stable component free from filling defects can be produced.

(46) As shown, a magnetic body can be made thinner than ever possible, and a component smaller in size and higher in performance than ever possible can be manufactured, using the composite magnetic material proposed by the present invention.

(47) The evaluations made other than those of electrical characteristics are described below.

(48) Each composite magnetic material can be evaluated based on its section. For the fill ratio of metal magnetic grains, a scanning electron microscope (SEM) was used to obtain a SEM image (3000 times) which was then processed. In the obtained section, the area occupied by metal magnetic grains and area not occupied by metal magnetic grains were identified and the ratio of the area occupied by metal magnetic grains was used as the fill ratio. In the section, metal magnetic grains were discriminated based on presence/absence of oxygen, and those visible grains in the section with a size (maximum length) of 1 m or more were considered metal magnetic grains. This range was adopted because metal magnetic grains of less than 1 m in grain size would have little effect on the magnetic characteristics.

(49) The content of iron (Fe element) in the metal magnetic grain can also be measured by SEM-EDX. A SEM image (3000 times) of a section of the composite magnetic material was obtained and grains of the same composition were selected by mapping, and then an average content of iron (elemental Fe) was obtained from at least 20 metal magnetic grains. If grains of different compositions are found by mapping, it can be judged that metal magnetic grains of different compositions have been mixed in. Also, for the grain size of metal magnetic grains, a SEM image (approx. 30000 times) of a section of the composite magnetic material was obtained and at least 300 average-sized grains were selected in the measured area, and then the area occupied by these grains was measured in the SEM image to calculate the grain size by assuming that the grains are spherical. If the obtained grain size distribution shows two peaks, it can be judged that metal magnetic grains of a different average grain size have been mixed in. All measurements were performed by selecting the center area of the section of the magnetic body formed with the composite magnetic material. In addition, all measurements were taken by selecting visible grains in the section with a size of 1 m or more.

(50) In the present disclosure where conditions and/or structures are not specified, a skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. Also, in the present disclosure including the examples described above, any ranges applied in some embodiments may include or exclude the lower and/or upper endpoints, and any values of variables indicated may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, a may refer to a species or a genus including multiple species, and the invention or the present invention may refer to at least one of the embodiments or aspects explicitly, necessarily, or inherently disclosed herein. The terms constituted by and having refer independently to typically or broadly comprising, comprising, consisting essentially of, or consisting of in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

(51) The present application claims priority to Japanese Patent Application No. 2014-176673, filed Aug. 30, 2014, and No. 2015-153929, filed Aug. 4, 2015, each disclosure of which is incorporated herein by reference in its entirety.

(52) It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.