JP6468412B2 - Magnetic core and coil device - Google Patents

Description

  The present invention relates to a magnetic core in which terminal electrodes can be easily formed, and a coil device having the magnetic core.

  In order to form a terminal electrode (for example, an Ag electrode film) on a magnetic core used in a coil device or the like, first, Ag powder and glass frit are applied to a predetermined electrode portion of the magnetic core, and heat treatment (firing) is performed. An electrode is formed, followed by Ni and Sn plating.

  Alternatively, as shown in Patent Document 1 below, a terminal electrode is formed by applying solder paste to the base electrode. In any case, it is necessary to apply the Ag powder and the glass frit and to perform heat treatment (firing) to form the base electrode, which has a problem that the process becomes complicated and the workability is poor. In addition, since the base electrode is formed by such a method, a part of the glass frit exists on the surface, and there is a problem that plating may be difficult.

JP 2013-45928 A

  The present invention has been made in view of such a situation, and an object thereof is to provide a magnetic core in which a terminal electrode can be easily formed and a coil device having the magnetic core.

In order to achieve the above object, the magnetic core according to the present invention comprises:
A magnetic core in which metal particles are insulated by an insulating phase,
The insulating phase is removed from only a part of the surface of the magnetic core, and a predetermined electrode portion in which the surface of the metal particle is exposed within a predetermined area region is formed. An electrode is formed.

  In the magnetic core according to the present invention, it is not necessary to apply a metal powder such as Ag and glass frit and to perform heat treatment (firing) to form a base electrode. Instead, for example, only by performing chemical treatment such as applying chemicals on a part of the surface of the magnetic core, or physical treatment such as vacuum plasma treatment, the insulating phase is removed, and the surface of the metal particles is removed. An exposed electrode portion is formed.

  Since the insulating phase is removed and the surface of the metal particles is exposed at the planned electrode portion, the surface can be plated, and the terminal electrode can be easily formed by plating. In the present invention, since glass frit is not used, part of the glass frit does not exist on the surface, and plating can be performed easily and reliably. In addition, it is also easy to form a solder film on the planned electrode portion of the present invention instead of plating. In the present invention, the recording terminal electrode can be composed of a plating film or a solder film.

  In the present invention, the method of forming the electrode planned portion is not particularly limited, but preferably, chemical treatment such as applying a chemical to a part of the surface of the magnetic core or physical treatment such as vacuum plasma treatment is performed.

  The insulating phase may be an inorganic insulating film formed on the surface of the metal particles, or a synthetic resin in which the metal particles are dispersed.

Preferably, the magnetic core includes
A core around which the wire is wound;
And a flange portion located at an end portion in the axial direction of the winding core portion are integrally formed,
The planned electrode portion is formed in the collar portion.

  For example, at least one end of the wire is connected to the terminal electrode.

The coil device according to the present invention includes:
The magnetic core according to the above and a wire wound around the core portion.

FIG. 1A is a partially cutaway perspective view of a coil device according to an embodiment of the present invention. FIG. 1B is a partially cutaway perspective view of a coil device according to another embodiment of the present invention. FIG. 2 is a perspective view of the coil device shown in FIG. 1A as viewed from the bottom side. 3A to 3C are schematic cross-sectional views showing a method for manufacturing the terminal electrode shown in FIG. 1A. FIG. 4 is a perspective view of a magnetic core showing a manufacturing process of a coil device according to another embodiment of the present invention. FIG. 5A is a perspective view showing a modified example of the planned electrode portion, following the step of FIG. FIG. 5B is a perspective view showing a modification of FIG. 5A. FIG. 6A is a perspective view showing a manufacturing process of the coil device showing a continuation process of FIG. FIG. 6B is a perspective view showing a manufacturing process of the coil device showing a manufacturing process different from FIG. 6A and showing a process subsequent to FIG. FIG. 7A is a perspective view of a coil device according to another embodiment of the present invention showing a step subsequent to FIG. 6A. FIG. 7B is a perspective view of a coil device according to still another embodiment of the present invention showing a step subsequent to FIG. 6B. Figure 8 A is a cross-sectional perspective view taken along VIIIA-VIIIA line shown in FIG. 7 A. Figure 8 B is a cross-sectional perspective view taken along VIIIB-VIIIB line shown in FIG. 7 B.

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

First Embodiment As shown in FIGS. 1A and 2, a coil device 1 according to an embodiment of the present invention has a magnetic core 2. The magnetic core 2 has a core portion 4 around which the wire 12 is wound, and flanges 6 and 8 that are positioned at both ends in the axial direction (Z-axis direction) of the core portion 4, respectively. Is integrally molded.

  In the present embodiment, the winding core portion 4 has a cylindrical shape, and the wire 12 is wound in a single layer or a plurality of layers around the winding core portion 4 to constitute the coil portion 10. However, the core part 4 is not limited to a cylindrical shape, and may be an elliptical column shape, a prismatic shape, or other shapes. Moreover, although the collar parts 6 and 8 are rectangular plate shapes in this embodiment, any shape can be used as long as it is a polygonal plate shape, a disk shape, an elliptical plate shape, or any other size larger than the core portion 4. Such a shape may be used.

  The flanges 6 and 8 do not necessarily have the same shape as each other, but have the same shape in the present embodiment. The size of the coil device 1 is not particularly limited, but the length (X-axis direction) is 0.4 to 20 mm, the width (Y-axis direction) is 0.2 to 20 mm, and the height (Z-axis direction) is. 0.2 to 15 mm. Note that the X axis, the Y axis, and the Z axis are perpendicular to each other.

  In the present embodiment, of the two flange portions 6 and 8, the back surface 8a of the flange portion 8 on the side where the coil device 1 is mounted is insulated by a predetermined distance on both sides in the X-axis direction, and the terminal electrode 24 and 26 is formed. The terminal electrode 24 is formed continuously from the electrode body 24a fixed to the back surface 8a of the flange 8 and both ends of the electrode body 24a in the Y-axis direction, and is opposed to the Y-axis direction of the flange 8. And auxiliary electrode pieces 24b fixed to the side surfaces 8b and 8c.

  Similarly to the terminal electrode 24, the terminal electrode 26 is formed continuously from the electrode body 26 a fixed to the back surface 8 a of the collar portion 8 and both ends of the electrode body 26 a in the Y-axis direction. And auxiliary electrode pieces 26b fixed to side surfaces 8b and 8c facing each other in the Y-axis direction. On the auxiliary electrode pieces 24b and 26b formed on one side surface 8b in the Y-axis direction, both ends 12a and 12b of the wire 12 wound around the coil portion 10 are respectively formed by laser welding, resistance welding, or soldering. Connected. Note that both ends 12 a and 12 b of the wire 12 may be directly connected to electrode bodies 24 a and 26 a fixed to the back surface 8 a of the flange portion 8.

  In the present embodiment, the wire 12 is not particularly limited, and may be a single wire or a stranded wire. Examples of the material include copper, silver, gold, and alloys thereof. Further, the cross section of the wire 12 is not limited to a circle, and may be a flat section as shown in FIG. 1B. These wires 12 are preferably covered with insulation at portions other than both ends 12a and 12b connected to the auxiliary electrode pieces 24b and 26b. In FIG. 1B, the wire 12 is edgewise wound around the core 4 but may be crosswise wound.

  In this embodiment, as shown in FIG. 3A, the magnetic core 2 has a microstructure in which a large number of metal particles 30 are insulated from each other by an inorganic insulating film 32 as an insulating phase. The metal particles 30 are not particularly limited as long as they are magnetic metals. For example, Fe-Ni alloy powder, Fe-Si alloy powder, Fe-Si-Cr alloy powder, Fe-Si-Al alloy powder, permalloy powder, Amorphous powder, Fe powder, etc. are illustrated. These ferromagnetic metal powders are suitable because they have a higher saturation magnetic flux density than the ferrite powders, and the DC superposition characteristics are maintained up to a high magnetic field.

  The inorganic insulating film 32 is made of, for example, a silicon oxide film, a metal oxide film, a glass film, or the like. The particle size of the metal particles 30 is not particularly limited, but is preferably an average particle size of 0.5 to 100 μm. The thickness of the inorganic insulating coating 32 is not particularly limited, but is preferably 1/1000 to 1/10 of the particle size of the metal particles 30. Although the metal particles 30 themselves have conductivity, the metal particles 30 are insulated from each other by an insulating coating 32, and the whole magnetic core 2 can be said to be an insulator.

  The magnetic core 2 of the present embodiment is a sintered body, and is obtained by firing granulated powder containing the metal particles 30 into a predetermined shape after being pressure-molded in a mold. The molding method is not limited to this embodiment. For example, injection molding, extrusion molding, lamination molding, transfer molding and the like are exemplified. By firing the core molded body before firing at, for example, 600 to 1100 ° C., the magnetic core 2 after firing is obtained.

  A method for forming the terminal electrodes 24 and 26 on the magnetic core 2 shown in FIGS. 1A and 1B will be described below.

  Only the planned electrode portion 20 of the magnetic core 2 where the terminal electrodes 24 and 26 are formed is subjected to chemical treatment on the surface of the core 2. In this chemical treatment, only the surface of the magnetic core 2 corresponding to the planned electrode portion 20 is exposed, and the surface of the other portion of the core 2 is masked with a resist film (removed after the chemical treatment) or the like. In this state, only the surface of the magnetic core 2 corresponding to the planned electrode portion 20 is immersed in a chemical within a predetermined area corresponding to the planned electrode portion 20. As the chemical, a chemical that dissolves and removes the insulating coating 32 is preferable.

  For example, when the insulating coating 32 is a silicon oxide film, hydrofluoric acid, chemical conversion soda, or the like is used as the chemical. When the insulating film 32 is a (metal oxide film), an oxide film remover, nitric acid, sulfuric acid, hydrochloric acid, ammonia, or the like is used as the chemical.

  As conditions for immersing the surface of the magnetic core 2 corresponding to the planned electrode portion 20 in the chemical, as shown in FIG. 3B, the surface of the metal particle 30 on the surface of the core 2 corresponding to the planned electrode portion 20 is The conditions are such that the metal particles 30 that are exposed and located on the final surface after treatment do not fall off the surface. In order to prevent the metal particles 30 from falling off the surface, it is preferable that the metal particles are exposed only on the outer surface of the metal particles 30 and the insulating coating 32 is not removed on the inner surface of the metal particles 30.

  The method for realizing the surface state as shown in FIG. 3B is not limited to the chemical immersion treatment. For example, physical processing such as vacuum plasma processing may be used.

  Moreover, sandblasting etc. are illustrated as another method for implement | achieving a surface state as shown to FIG. 3 (B).

Then, in the present embodiment, as shown in FIG. 3 (C), the insulating film 32 is removed on the surface of the electrode scheduled portion 20 where the surface of the metal particles 30 are exposed, electrolytic plating or electroless solutions plating Thus, a desired plating film is deposited to form terminal electrodes 24 and 26 having a predetermined thickness. The plating film may be a single layer or multiple layers. For example, a plating film such as Ni—Sn plating, Cu—Ni—Sn plating, Sn plating, Ni—Au plating, or Au plating is formed. The thickness of the terminal electrodes 24 and 26 is not particularly limited, but is preferably 0.1 to 15 μm.

  In the magnetic core 2 according to the present embodiment, it is not necessary to apply a metal powder such as Ag and glass frit and perform heat treatment (firing) to form a base electrode. Instead, for example, an electrode in which the surface of the metal particle 30 is exposed by removing the insulating coating 32 only by chemical treatment or physical treatment of only a part of the surface of the magnetic core 2 (predetermined electrode portion 20). A planned portion 20 is formed.

  Since the insulating coating 32 is removed and the surface of the metal particles 30 is exposed at the planned electrode portion 20, the surface can be easily plated, and the terminal electrodes 24 and 26 can be easily formed by plating. it can. In the present embodiment, since glass frit is not used, part of the glass frit does not exist on the surface, and plating can be performed easily and reliably. Further, in the present embodiment, it is not necessary to form a base electrode by applying a metal powder such as Ag and glass frit and performing heat treatment (firing), which contributes to a reduction in manufacturing cost.

In the present embodiment, the terminal electrodes 24 and 26 may be formed by forming a solder film at the planned electrode portion 20 instead of plating. In order to form a solder film, as shown in FIGS. 3B and 3C, the surface 20 of the planned electrode portion where the surface of the metal particles 30 is exposed by removing the insulating film 32 is selected. Then, a solder film is formed, and terminal electrodes 24 and 26 are obtained. In forming the solder film, the terminal electrodes 24 and 26 may be formed by forming a solder film by dipping after applying the flux.

  In this case, since no plating process is required, the workability is further improved and the manufacturing cost is reduced. Furthermore, by not performing the plating process, it is possible to effectively prevent IR deterioration due to the remaining plating solution.

  In the above-described embodiment, the terminal electrodes 24 and 26 are continuously formed not only on the bottom surface 8a of the flange portion 8 but also on the side surfaces 8b and 8c, but may be formed only on one of the surfaces. good. Further, the positions where the terminal electrodes 24 and 26 are formed are not particularly limited.

Second Embodiment The present embodiment is the same as the first embodiment except for the following, and has the same effects.

  In this embodiment, the magnetic body core 2 is not a sintered body but is formed of a molded body obtained by compacting and includes a synthetic resin. At the time of compacting, a molten synthetic resin in which metal particles are dispersed is poured into a mold, and the synthetic resin is cured by heat, for example. In that case, the magnetic core 2 is made of a synthetic resin in which the metal particles 30 are dispersed, and the synthetic resin becomes an insulating phase. Examples of the synthetic resin used for compacting include epoxy resins, urethane resins, acrylic resins, diallyl phthalate resins, silicone resins, polyimide amide resins, polyimide resins, PVA resins, and the like.

  In this embodiment, for example, when the synthetic resin is an epoxy resin, toluene, xylene, sulfuric acid, nitric acid, or the like is used as a chemical that dissolves and removes the synthetic resin present on the surfaces of the metal particles 30.

  As a condition for immersing the surface of the magnetic core 2 corresponding to the planned electrode portion 20 in the chemical, the surface of the metal particles 30 is exposed on the surface of the core 2 corresponding to the planned electrode portion 20, and the final surface after the treatment is exposed. The condition is such that the positioned metal particles 30 do not fall off the surface. In order to prevent the metal particles 30 from falling off the surface, the metal particles are exposed only on the outer surface of the metal particles 30, and the synthetic resin as an insulating phase is not removed on the inner surface of the metal particles 30. Is preferred.

  The method for realizing such a surface state is not limited to the chemical immersion treatment. For example, physical processing such as vacuum plasma processing may be used. The preferable conditions for the vacuum plasma treatment for removing the synthetic resin on the surface of the metal particles 30 are preferably the same as the conditions for removing the inorganic insulating film in the first embodiment.

Third Embodiment A coil device according to a third embodiment of the present invention is the same as the coil device 1 of the first embodiment except for the following, and has the same effects. That is, in the present embodiment, as shown in FIGS. 4, 5A, and 5B, a pair that extends along the X-axis direction away from the Y-axis direction on the back surface 8a of the flange portion 8. The groove 8a1 is formed.

  The groove 8a1 is a portion that is recessed from the back surface 8a of the magnetic core 2 by grinding, polishing, or cutting. As shown in FIG. 5A, a frame portion 8a2 is formed on the outer side in the X-axis direction of each groove 8a1. It may remain, or the frame portion 8a2 may be removed as shown in FIG.

  The groove depth in the Z-axis direction of each groove 8a1 is not particularly limited, but is preferably smaller than the thickness t0 of the flange portion 8 and ½ or less of t0. From the viewpoint of reducing the height of the coil device 1 in the Z-axis direction, the groove depth of the groove 8a1 is such that at least a part (preferably all) of the groove 8a1 is accommodated in the terminal electrodes 24 and 26. preferable. By forming the groove 8a1 by grinding, polishing, or cutting, a predetermined electrode portion 20 is formed in that portion, as in the first embodiment. In addition, when it is not necessary to make the Z-axis direction height of the coil apparatus 1 small, you may grind | polish or polish the applicable surface, without forming the groove | channel 8a1, and may form the electrode planned part 20. FIG.

  As shown in FIG. 6A, the end portions 12a and 12b of the wire 12 may be inserted into the predetermined electrode portion 20 of each groove 8a1 after being wound by the wire 12, as shown in FIG. 6A. In addition, the solder 24A and 26A may be selectively attached to the predetermined electrode portion 20 of each groove 8a1 before the wire 12 is wound.

  As shown in FIG. 6A, when the ends 12a and 12b of the wire 12 are inserted after the winding by the wire 12, as shown in FIG. 7A, the ends are located in the grooves 8a1. The terminal electrodes 24 and 26 are formed by attaching solder to the planned electrode portions 20 of the grooves 8a1 so as to cover the ends 12a and 12b of the wire 12. In that case, as shown in FIG. 8A, each end 12a, 12b of the wire 12 covered with the terminal electrodes 24, 26 made of solder is in close contact with the bottom surface of each groove 8a1.

  As shown in FIG. 6B, when the solders 24A and 26A are selectively attached to the predetermined electrode portion 20 of each groove 8a1 before the wire 12 is wound, as shown in FIG. The wire 12 is wound. After that, each end 12a, 12b of the wire 12 is reattached with solder so as to be embedded in the solder 24A and 24B shown in FIG. 6B, and as shown in FIG. 7B, the terminal electrodes 24, 26 made of solder are installed. Embedded inside. In this case, as shown in FIG. 8B, a gap is formed between each end 12a, 12b of the wire 12 covered with the terminal electrodes 24, 26 and the bottom surface of each groove 8a1, and solder is interposed therebetween. become.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, the outer periphery of the coil portion 10 may be filled with a synthetic resin containing magnetic powder in the gap between the flange portions 6 and 8. In that case, the inductance of the coil device is improved.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
The mold was filled with granulated powder containing the metal particles 30 and subjected to pressure molding to obtain a core compact before firing. The core body before firing was fired at 600 to 850 ° C. to obtain a magnetic core 2 after firing. Only a part of the surface of the magnetic core 2 was chemically treated by a chemical immersion method under conditions of 5% diluted sulfuric acid solution for 5 minutes. A plating film was formed on the surface under the condition of two-layer plating of barrel plating Ni—Sn to obtain a terminal electrode. It was confirmed that the plating film was formed only on the chemical immersion surface of the core 2. The total thickness of the plating film was 8 μm. In addition, the inorganic insulating coating 32 of the metal particles 30 is a silicon-based oxide coating, and the chemical for removal thereof is sulfuric acid.

Example 2
In Example 1, a terminal electrode was formed in the same manner as in Example 1 except that the solder film was formed by dipping the solder solution without plating. It was confirmed that the solder coating was formed only on the chemically treated surface of the core 2. The thickness of the solder coating was 20 μm.

DESCRIPTION OF SYMBOLS 1 ... Coil apparatus 2 ... Magnetic body core 4 ... Core part 6, 8 ... Eaves part 8a1 ... Groove 8a2 ... Frame part 10 ... Coil part 12 ... Wire 20 ... Electrode planned part 24, 26 ... Terminal electrode 24A, 26A ... Solder 30 ... Metal particle 30a ... Extending portion 32 of metal particle in planar direction ... Insulating coating

Claims (6)

A magnetic core in which metal particles are insulated by an insulating phase,
The magnetic core is made of a sintered body,
The average particle diameter of the metal particles is 0.5 to 100 μm,
The insulating phase is an inorganic insulating film formed on the surface of the metal particles,
The thickness of the inorganic insulating coating is 1/1000 to 1/10 of the average particle diameter of the metal particles,
Wherein only a portion of the surface of the magnetic core, wherein the inorganic insulating film is removed, only the outer surface of the adjacent metal particles are exposed at a predetermined area region, the inorganic inside surface of the metal particles The electrode planned part where the insulating film is not removed is formed,
A magnetic core in which a terminal electrode is formed in the predetermined electrode portion.   The magnetic core according to claim 1, wherein the terminal electrode is a plating film or a solder film.   3. The magnetic core according to claim 1, wherein the predetermined electrode portion is formed by performing chemical treatment or physical treatment on a part of the surface of the magnetic core. In the magnetic core,
A core around which the wire is wound;
And a flange portion located at an end portion in the axial direction of the winding core portion are integrally formed,
The electrode will part, the magnetic core according to any one of claims 1 to 3 is formed on the flange portion. The magnetic core according to claim 4 , wherein at least one end of the wire is connected to the terminal electrode. A magnetic core according to claim 4 or 5 ,
The coil apparatus which has a wire wound around the said winding core part.

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