JP2006344683A - Drum core and inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum core and an inductor capable of improving productivity, reduced in size and lowered in back height, while mechanical strength is enhanced. <P>SOLUTION: A drum core 1 is constituted such that a central cylinder column 1a and guards 1b, 1b of both sides are connected integrally, and a coil 3 is wound around the cylinder 1a. A sleeve core 2 is made in a shape of a cylinder, and surrounds the drum core 1 in a shape of a concentric circle. The drum core 1 and the sleeve core 2 are composed of Li system ferrite which is expressed as a composition formula of x(Li<SB>0.5</SB>Fe<SB>0.5</SB>) O yZnO zFe<SB>2</SB>O<SB>3</SB>(0.15≤x≤0.50, 0.05≤y≤0.33, 0.45≤z≤0.55, x+y+z=1). The height of the drum core 1 is 1 mm, and the thickness of each guard 1b, 1b is 0.3 mm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drum core and an inductor used for a DC / DC converter or the like.

  Inductors used in DC / DC converters of electronic devices such as cellular phones are strongly required to be small and low. As a conventional inductor, a closed magnetic circuit type inductor having a drum core in which a magnet wire is wound as a coil and a sleeve core that concentrically surrounds the drum core is known (for example, see Patent Document 1). The drum core and sleeve core generally use Ni-based ferrite, and the size of the drum core and sleeve core to be used is reduced to reduce the size and height of the inductor.

For the purpose of reducing the size and the height, a multilayer inductor formed by laminating a plurality of magnetic bodies having a coil pattern is also widely used (see, for example, Patent Document 2). Generally, Ni-based ferrite is used for the magnetic material.
JP 2001-338817 A JP-A-60-244097

  In the former inductor described above, the drum core and the sleeve core are thinned in order to realize a reduction in size and height, but the mass productivity in terms of strength is lost by thinning. However, there is a problem that there is a limit to the thickness reduction. On the other hand, in the latter inductor, the thickness is reduced to achieve a smaller size and a lower profile, but the strength of the ferrite is the alumina that is generally used as the base material of the multilayer substrate. As a result, it is difficult to handle as a collective substrate.

  The present invention has been made in view of such circumstances, and by using Li-based ferrite as a material, the mechanical strength is higher than when Ni-based ferrite is used, and further miniaturization and low profile are achieved. It is an object of the present invention to provide a drum core that can be realized and can improve productivity.

  Another object of the present invention is that the drum core or the drum core and the sleeve core are made of Li-based ferrite, so that the mechanical strength is higher than that of the case where the drum core is made of Ni-based ferrite. It is an object to provide an inductor capable of realizing a low profile and improving productivity.

  Still another object of the present invention is that the magnetic material to be laminated is composed of Li-based ferrite, so that the mechanical strength is higher than when composed of Ni-based ferrite and can be handled as a collective substrate. Is to provide an inductor.

  A drum core according to the present invention is characterized in that a drum core having a columnar part and flanges on both sides connected to the cylindrical part is made of Li-based ferrite and has a height of 1.4 mm or less.

  The drum core of the present invention is composed of Li-based ferrite. Therefore, the mechanical strength is improved as compared with the case where it is made of Ni-based ferrite, and sufficient strength can be obtained even when the height is 1.4 mm or less.

  The inductor according to the present invention is composed of a cylindrical portion and flanges on both sides connected to the cylindrical portion, and in the inductor having a drum core in which a coil is wound around the cylindrical portion, the drum core is made of Li-based ferrite, The height is less than 1.5 mm.

  In the inductor of the present invention, the drum core is composed of Li-based ferrite. Therefore, the mechanical strength is improved as compared with the case of being composed of Ni-based ferrite, and sufficient strength can be obtained even if the height is less than 1.5 mm.

  The inductor according to the present invention is characterized in that an adhesive resin is provided between the flanges on both sides of the drum core.

  In the inductor of the present invention, an adhesive resin is provided between both flange portions of the drum core. Therefore, the mechanical strength is improved.

  The inductor according to the present invention has a cylindrical sleeve core surrounding the drum core, and the sleeve core is made of Li-based ferrite.

  In the inductor of the present invention, in addition to the drum core, the sleeve core is also composed of Li-based ferrite. Therefore, the mechanical strength is improved as compared with the case of being composed of Ni-based ferrite, and sufficient strength can be obtained.

  The inductor according to the present invention is an inductor in which a magnetic circuit is formed by laminated magnetic bodies, wherein the magnetic body is made of Li-based ferrite and has a thickness of 1.0 mm or less.

  In the inductor of the present invention, the laminated magnetic body is made of Li-based ferrite. Therefore, the mechanical strength is improved as compared with the case of being composed of Ni-based ferrite, and even when the thickness is 1.0 mm or less, sufficient strength can be obtained and handled as a collective substrate.

In the inductor according to the present invention, the composition formula of the Li-based ferrite is x (Li _0.5 Fe _0.5 ) O · yZnO · zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0. 33, 0.45 ≦ z ≦ 0.55, x + y + z = 1).

In the inductor of the present invention, x (Li _0.5 Fe _0.5 ) O.yZnO.zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0.33, 0.45 ≦ z ≦ 0.55, x + y + z = 1) Li-based ferrite whose composition formula is expressed is used. Therefore, preferable magnetic characteristics can be obtained in terms of initial magnetic permeability, Curie temperature, saturation magnetic flux density, anti-magnetostriction and the like.

Inductor according to the present invention, in the composition formula of the Li-based ferrite, replacing a part of ZnO in CuO, and / or by a part of Fe ₂ O ₃ to be replaced by Mn ₂ O ₃ It is characterized by being.

In the inductor of the present invention, a part of ZnO is replaced with CuO. Therefore, densification at a lower firing temperature is possible. Also, substituting a part of Fe ₂ O ₃ with Mn ₂ O _3. Therefore, the generation of Fe ²⁺ is suppressed and a high specific resistance is obtained.

  Since the drum core of the present invention is made of Li-based ferrite, the strength can be improved compared to the case of Ni-based ferrite, and the height and height can be reduced to 1.4 mm or less. Can be realized.

  In the inductor according to the present invention, the drum core is made of Li-based ferrite, so that the strength can be improved as compared with the case of being made of Ni-based ferrite, and the size is reduced to a height of less than 1.5 mm. Can be realized.

  In the inductor according to the present invention, since the adhesive resin is provided between the flanges on both sides of the drum core, the mechanical strength can be further improved.

  In the inductor according to the present invention, since the sleeve core is made of Li-based ferrite in addition to the drum core, the strength can be improved compared with the case of being made of Ni-based ferrite, and the size and height can be reduced. Can be realized.

  In the inductor of the present invention, the laminated magnetic body is made of Li-based ferrite, so that the strength can be improved as compared with the case of being made of Ni-based ferrite, and the thickness is 1.0 mm or less. Can be realized as a collective substrate.

In the inductor of the present invention, the composition formula of the Li-based ferrite used is x (Li _0.5 Fe _0.5 ) O · yZnO · zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0. 33, 0.45 ≦ z ≦ 0.55, x + y + z = 1), it is possible to obtain preferable magnetic characteristics (initial magnetic permeability, Curie temperature, saturation magnetic flux density, coercive strain, etc.).

The inductor of the present invention, replacing a part of ZnO in CuO, and / or, since a part of Fe ₂ O ₃ was set to be replaced by Mn ₂ O _3, realize densification at lower firing temperatures And / or production of Fe ²⁺ is suppressed and a high specific resistance can be obtained.

Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. In addition, this invention is not limited to the following embodiment.
(First embodiment)
FIG. 1 shows the configuration of the drum core 1 and the sleeve core 2 according to the first embodiment. FIG. 1 (a) is an external view thereof, and FIG. 1 (b) is a sectional view thereof.

Each of the drum core 1 and the sleeve core 2 has a composition formula of x (Li _0.5 Fe _0.5 ) O.yZnO.zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0.33, 0 .45 ≦ z ≦ 0.55, x + y + z = 1), and is composed of a Li-based ferrite. The drum core 1 is configured by integrating a central cylindrical portion 1a and flanges 1b and 1b on both sides connected thereto. The sleeve core 2 has a cylindrical shape and surrounds the drum core 1 concentrically.

  The height of the drum core 1 is 1 mm, and the diameters of the flange portions 1b and 1b are 3 mm. The thickness of the flanges 1b and 1b is 0.3 mm or less and is quite thin. The sleeve core 2 has an outer diameter of 3.8 mm, an inner diameter of 3.2 mm, a height of 0.85 mm, a small thickness, and a low height.

  In such a thin and low-profile structure, defects such as cracks occur in the conventional example composed of Ni-based ferrite, but in the present invention, it is composed of Li-based ferrite. Compared to the example, the strength can be improved by about 20%, and no defect occurs. Moreover, since the mechanical strength is improved, the production yield of the drum core can be increased.

(Second Embodiment)
FIG. 2 is a perspective view showing the configuration of the inductor 10 according to an example of the second embodiment. In FIG. 2, the same parts as those in FIG. The inductor 10 shown in FIG. 2 is configured by winding a coil 3 made of a magnet wire around the cylindrical portion 1a of the drum core 1 described in the first embodiment.

  FIG. 3 shows a configuration of an inductor 10 according to another example of the second embodiment. FIG. 3A is an exploded perspective view and FIG. 3B is a cross-sectional view thereof. In FIG. 3, the same parts as those of FIG. The inductor 10 shown in FIG. 3 is formed by winding a coil 3 made of a magnet wire around the cylindrical portion 1a of the drum core 1 described in the first embodiment, and surrounding it with the sleeve core 2 described in the first embodiment. It is composed.

  Inductor 10 having such a thin and low-profile structure is composed of Li-based ferrite, so that it is possible to improve the strength by about 20% compared to the conventional example composed of Ni-based ferrite. . Further, since the mechanical strength is improved, defects due to core cracks or chipping during winding are reduced, and the manufacturing yield of inductors can be increased. Furthermore, defects due to core cracks or chipping caused by an impact when the inductor 10 is automatically mounted are reduced, and the reliability of the performance as the inductor is improved.

(Third embodiment)
FIG. 4 is a perspective view showing the configuration of the inductor 10 according to an example of the third embodiment. 4, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted. In addition to the configuration of the inductor 10 shown in FIG. 2, the inductor 10 shown in FIG. 4 has a resin 4 made of, for example, an epoxy adhesive on the outer peripheral surface of the coil 3 between the flanges 1b and 1b on both sides of the drum core 1. Is provided.

  FIG. 5 shows a configuration of an inductor 10 according to another example of the third embodiment. FIG. 5A is an exploded perspective view and FIG. 5B is a cross-sectional view thereof. In FIG. 5, the same parts as those in FIGS. An inductor 10 shown in FIG. 5 is configured by surrounding the drum core 1 shown in FIG. 4 with the sleeve core 2 described in the first embodiment.

  As described above, in the third embodiment, the strength of the inductor 10 is increased by applying the adhesive resin to the flange portions 1b and 1b of the drum core 1.

  It is conceivable to increase the strength by applying the same resin to conventional inductors in which the drum core and sleeve core are made of Ni-based ferrite. However, since the strength of Ni-based ferrite is low, shrinkage during resin curing As a result, cracks often occur in the drum core, which reduces productivity. In addition, magnetostriction is generated by the stress received from the resin, and the magnetic properties of the drum core are significantly deteriorated. As a result, there are problems such as a decrease in inductance, a deterioration in DC superimposition characteristics, and a decrease in Q. On the other hand, in the inductor 10 of the present invention in which the drum core 1 and the sleeve core 2 are made of Li-based ferrite having excellent strength, cracks due to shrinkage during resin curing can be reduced. In addition, even when stress is applied from the resin, the magnetostriction constant is low, so that the magnetic characteristics are not degraded significantly. As a result, it is possible to suppress a decrease in inductance, a deterioration in DC superimposition characteristics, a decrease in Q, and the like.

(Fourth embodiment)
FIG. 6 shows the configuration of the inductor 20 according to the fourth embodiment. FIG. 6A is an external view thereof, and FIG. 6B is a cross-sectional view thereof.

The inductor 20 is configured by laminating a plurality of magnetic sheets 21 in which a conductor coil pattern is formed on a magnetic body. The magnetic body of each magnetic sheet 21 has a composition formula of x (Li _0.5 Fe _0.5 ) O.yZnO.zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0.33, 0 .45 ≦ z ≦ 0.55, x + y + z = 1), and is composed of a Li-based ferrite.

  The multilayer inductor 20 has a rectangular shape with a long side: 4.5 mm and a short side: 3.2 mm, and the thickness is as thin as 0.6 mm. However. Since Li-based ferrite having excellent strength is used as the base material, the strength is high, and the bending strength is improved to 60 N compared to 48 N in the conventional example using Ni-based ferrite as the base material. .

  FIG. 7 is a configuration diagram of a circuit module 33 in which an electronic component 32 is mounted on a collective substrate 31 having a plurality of circuit substrates 30 incorporating the inductor 20 according to the fourth embodiment. Each circuit board 30 is formed with a surface electrode 34, a side external electrode 35, and a bottom external electrode (not shown). The surface electrode 34 serving as a component land has an IC, a diode, a capacitor, a resistor, or the like. The electronic component 32 is joined. Thus, by mounting the electronic component 32 on the circuit board 30, it functions as a circuit module such as a DC / DC converter.

  The conventional multilayer inductor using Ni-based ferrite as the magnetic material is weak in strength and cannot be handled as a collective substrate. Therefore, in the conventional example, electronic parts are mounted on each individual circuit board, and the production efficiency is extremely low. On the other hand, in the multilayer inductor 20 of the present invention, since Li-based ferrite having excellent strength is used as a magnetic body, even a thin circuit board 30 can be handled as a collective board 31. Become. Therefore, in the present invention, the electronic component 32 can be mounted on each circuit board 30 with the collective substrate 31 as it is, and the production efficiency can be greatly improved as compared with the conventional example.

Hereinafter, the composition of the Li-based ferrite used for the inductors 10 and 20 of the present invention will be described in detail. As described above, the composition formula of the Li-based ferrite is x (Li _0.5 Fe _0.5 ) O · yZnO · zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0.33, 0 .45 ≦ z ≦ 0.55, x + y + z = 1).

X in the above composition formula represents the content ratio of (Li _0.5 Fe _0.5 ) O, and a range of 0.15 to 0.50 is preferable. This is because if the temperature is less than 0.15, the Curie temperature cannot be improved, and if it exceeds 0.50, the initial magnetic permeability is small and impractical. Moreover, y represents the content rate of ZnO and the range of 0.05-0.33 is preferable. This is because an initial permeability of less than 0.05 is small and impractical, and if it exceeds 0.33, an increase in Curie temperature cannot be expected. Since x + y + z = 1 is satisfied and the range of z is narrow, x and y have a substantially inversely proportional relationship.

Z in the above composition formula represents the content ratio of Fe ₂ O ₃ and is preferably in the range of 0.45 to 0.55. This is because if it is less than 0.45, the saturation magnetic flux density and the Curie temperature are lowered, so that it cannot be used for applications requiring large amplitude excitation, and if it exceeds 0.55, the specific resistance becomes low and the magnetic loss decreases. This is because it increases. The range indicated by z does not include Fe in x (Li _0.5 Fe _0.5 ) O.

  By substituting a part of ZnO with CuO, densification at a lower firing temperature becomes possible. A preferable substitution ratio in this case is 0 to 0.5 (50% or less). If the substitution ratio exceeds 0.5, the magnetic permeability decreases, which is not preferable.

By substituting part of Fe ₂ O ₃ with Mn ₂ O ₃ , formation of Fe ²⁺ is suppressed and a high specific resistance can be obtained. The preferable substitution ratio in this case is 0 to 0.3 (30% or less). When the substitution ratio exceeds 0.3, the saturation magnetic flux density and the Curie temperature decrease, which is not preferable.

Such a Li-based ferrite can be produced by the following process.
(1) A composition after sintering a carbonate powder and an oxide powder as materials is x (Li _0.5 Fe _0.5 ) O · yZnO · zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0. 05 ≦ y ≦ 0.33, 0.45 ≦ z ≦ 0.55, x + y + z = 1) and weigh and mix.
(2) This mixed powder is calcined. The calcination temperature is preferably 800 to 1000 ° C., the calcination time is preferably 2 to 5 hours, and the calcination atmosphere is preferably in the air or in oxygen.
(3) A predetermined amount of Bi ₂ O ₃ is added to the calcined calcined powder and then pulverized. The pulverization is preferably performed in pure water or ethanol. The average particle size of the finely pulverized powder is preferably 0.5 to 1.5 μm. Bi ₂ O ₃ is preferably added after calcination and before pulverization, but it may be added after the material blending stage (step (1) above) or after pulverization.
(4) The finely pulverized powder is formed by a desired forming means. The molding pressure is preferably 70 to 150 MPa. In addition, you may granulate a pulverized powder with a granulator before shaping | molding as needed.
(5) Sinter the compact. The sintering atmosphere is preferably air or oxygen. The sintering temperature is preferably 800 to 1050 ° C, more preferably 850 to 1000 ° C. The sintering time is preferably 2 to 5 hours.

It is a block diagram of the drum core and sleeve core which concern on 1st Embodiment. It is a block diagram of the inductor which concerns on an example of 2nd Embodiment. It is a block diagram of the inductor which concerns on the other example of 2nd Embodiment. It is a block diagram of the inductor which concerns on an example of 3rd Embodiment. It is a block diagram of the inductor which concerns on the other example of 3rd Embodiment. It is a block diagram of the inductor which concerns on 4th Embodiment. It is a block diagram of the circuit module which mounted the electronic component on the aggregate substrate which has several circuit boards incorporating the inductor of 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drum core 1a Cylindrical part 1b collar part 2 Sleeve core 3 Coil 4 Resin 10 Inductor 20 Inductor 21 Magnetic material sheet 30 Circuit board 31 Collective board 32 Electronic component 33 Circuit module 34 Surface electrode 35 External electrode

Claims (7)

  A drum core having a cylindrical part and flanges on both sides connected to the cylindrical part, made of Li-based ferrite and having a height of 1.4 mm or less.   An inductor having a drum core having a cylindrical portion and flanges on both sides connected to the cylindrical portion, and a coil wound around the cylindrical portion, wherein the drum core is made of Li-based ferrite and has a height of less than 1.5 mm An inductor characterized by being.   The inductor according to claim 2, wherein an adhesive resin is provided between the flanges on both sides of the drum core.   An inductor having a cylindrical sleeve core surrounding the drum core, wherein the sleeve core is made of Li-based ferrite.   An inductor in which a magnetic circuit is formed by laminated magnetic bodies, wherein the magnetic body is made of Li-based ferrite and has a thickness of 1.0 mm or less. The composition formula of the Li-based ferrite is x (Li _0.5 Fe _0.5 ) O.yZnO.zFe ₂ O ₃ (0.15 ≦ x ≦ 0.50, 0.05 ≦ y ≦ 0.33, 0.45 ≦ z 6. The inductor according to claim 2, wherein ≦ 0.55, x + y + z = 1). Claims wherein In the composition formula Li ferrite, replacing a part of ZnO in CuO, and / or, characterized in that a part of Fe ₂ O ₃ are to be replaced by Mn ₂ O ₃ Item 7. The inductor according to Item 6.

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