JP2008205245A - Surface mounting choke coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress damage of a brim part and deterioration of an inductance value when magnetic powder content resin is thermally expanded. <P>SOLUTION: A surface mounting choke coil has a drum core 14 consisting of a winding core 11, an upper brim part 12 arranged at an upper end of the core 11 and a lower brim 13 disposed at a lower end, and a coil conductor 15 wound to a periphery of the winding core. Taper parts 12a and 13a are formed on faces confronted with the other brims of the upper brim and the lower brim on the drum core. An enlargement region A where an interval between the confronted brims is enlarged as it is detached in a radial direction from an outer peripheral face of the wound coil conductor is arranged. Magnetic powder content resin 16 is inserted into the enlargement region. Even if expansion by heat occurs in magnetic powder content resin, magnetic powder content resin can expand in the radial direction detached from the outer peripheral face of the coil conductor along an inner face of the brim. Force which is to extend a part between the upper brim and the lower brim is reduced. Damage of the brim and the occurrence of inner stress in the winding core are suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a winding type surface mount choke coil used for portable electronic devices, thin electronic devices and the like.

As a choke coil used for DC / DC power supply applications of portable electronic devices such as portable telephones and digital still cameras, and peripheral circuits of various flat panel displays, etc., high density mounting while ensuring desired inductor characteristics, Alternatively, there is a demand for a surface mount choke coil having a small size and a low profile that enables low profile mounting.

Since the portable electronic device is used by taking it outdoors or on the go, the temperature of the environment changes drastically, and it is expected that the user will accidentally drop it. For this reason, in the surface mount coil for the above-mentioned use, reliability with respect to temperature change and reliability with respect to impact are required.

Patent Document 1 discloses a surface-mount choke coil that is intended for use in the portable electronic device described above. As shown in FIG. 4, Patent Document 1 includes a drum core 4 composed of an upper collar part 2, a lower collar part 3 and a core part 1, and a coil winding 5 wound around the core part 1. A melt obtained by uniformly mixing ferromagnetic particles in a synthetic resin having viscoelasticity, outside the coil winding 5, between the upper flange portion 2 and the lower flange portion 3 of the drum core 4. There has been proposed a surface mount choke coil which is discharged and solidified to form a buffer shield material 6a. As shown in FIG. 5, Patent Document 1 includes a drum core 4 composed of an upper collar portion 2, a lower collar portion 3 and a core portion 1, and a coil winding 5 wound around the core portion 1. , A viscoelastic synthetic resin containing ferromagnetic particles uniformly is formed into a ring shape, and is fitted between the upper flange portion 2 and the lower flange portion 3 of the drum core 4, and the upper A surface-mounted choke coil in which a buffer shield material 6b is interposed between the flange portion 2 and the lower flange portion 3 has been proposed.
JP 2006-54394 A

The melt obtained by uniformly mixing the ferromagnetic particles in the viscoelastic synthetic resin described in the former background art is discharged between the upper and lower collar portions of the drum core and solidified. In the surface mount choke coil in which the buffer shield material 6a is formed, when the buffer shield material 6a expands due to a temperature change, it works so as to widen the space between the upper and lower flange portions 2, 3 and breaks the flange portions 2, 3. In addition, there is a problem that the internal stress of the winding core portion 1 increases through the flange portions 2 and 3 and the inductance value of the surface mount choke coil is likely to change. Also, a synthetic resin having the viscoelasticity described in the latter background art and containing ferromagnetic particles uniformly is formed into a ring shape, and the upper core portion 2 and the lower flange portion 3 of the drum core 4 are formed. In the surface mount choke coil that is fitted between and the buffer shield material 6b is interposed between the upper flange portion 2 and the lower flange portion 3, there is a gap between the flange portions 2, 3 and the buffer shield material 6b. As a result, the magnetic flux around the coil conductor 5 wound is suppressed, and a high inductance value cannot be obtained.

The object of the present invention is to solve the above-mentioned problems, and when the magnetic powder-containing resin thermally expands, the breakage of the collar part and the generation of internal stress in the core part via the collar part are suppressed, and the inductance value is reduced. An object of the present invention is to provide a surface mount choke coil which is less likely to be lowered.

In order to achieve the above object, a surface mount choke coil according to the present invention includes (1) a core part, an upper collar part provided at the upper end of the core part, and a lower collar part provided at the lower end of the core part. And a coil conductor wound around the core portion, and the other of at least one flange portion of the upper and lower flange portions of the drum core. A taper portion is formed on a surface facing the flange portion, and an enlarged region is provided in which an interval between the flange portions facing each other increases as the distance from the outer peripheral surface of the wound coil conductor in the radial direction increases. A magnetic powder-containing resin is charged in the enlarged region. (... hereinafter referred to as first problem solving means)

One of the main forms of the surface mount choke coil is as follows. (2) The cross-sectional shape in which the thickness of the magnetic powder-containing resin increases as the distance from the outer peripheral surface of the wound coil conductor increases in the radial direction. It is what has. (... hereinafter referred to as second problem solving means)

Also, one of the forms of the surface mount choke coil is as follows. (3) The upper flange portion and the lower portion where the interval increases as the magnetic powder-containing resin is separated from the outer peripheral surface of the wound coil conductor in the radial direction. It is discharged between the heel part and hardened. (... hereinafter referred to as third problem solving means)

One of the forms of the surface mount choke coil is that (4) the magnetic powder-containing resin is previously formed into an annular shape, and the interval increases as the distance from the outer peripheral surface of the wound coil conductor increases in the radial direction. It is fitted between the upper collar part and the lower collar part. (... hereinafter referred to as fourth problem solving means)

The operation of the first problem solving means is as follows. That is, a taper portion is formed on a surface facing at least one of the upper flange portion and the lower flange portion of the drum core in the radial direction from the outer peripheral surface of the wound coil conductor. An expansion region is provided in which the interval between the opposing buttock portions increases as the distance increases, and the magnetic powder-containing resin is inserted into the expansion region. Even if it exists, this magnetic powder containing resin can expand | swell to the direction spaced apart in the radial direction from the outer peripheral surface of the said coil conductor along the surface which has the taper part of the said collar part. For this reason, the force which pushes and spreads between an upper collar part and a lower collar part is reduced, and generation | occurrence | production of the internal stress of the core part via a collar part and the damage of a collar part is suppressed.

The operation of the second problem solving means is as follows. That is, since the magnetic powder-containing resin has a cross-sectional shape in which the thickness dimension increases as it is separated from the outer peripheral surface of the wound coil conductor in the radial direction, the magnetic powder-containing resin is wound when the magnetic powder-containing resin is thermally expanded. The coil conductor can be easily expanded in a direction away from the outer peripheral surface of the coil conductor in the radial direction.

The operation of the third problem solving means is as follows. That is, the magnetic powder-containing resin is discharged and cured between an upper collar part and a lower collar part whose distance increases as the distance from the outer circumferential surface of the wound coil conductor increases in the radial direction. Therefore, since air bubbles and gaps are not easily generated between the magnetic powder-containing resin and the surface of the flange portion, a decrease in inductance value can be suppressed.

The operation of the fourth problem solving means is as follows. That is, the magnetic powder-containing resin is previously formed into an annular shape, and is fitted between the upper collar portion and the lower collar portion, the interval of which increases as the distance from the outer peripheral surface of the wound coil conductor increases in the radial direction. Therefore, even if a dimensional variation occurs in either one of the magnetic powder-containing resin and the core, a gap is hardly generated between the magnetic powder-containing resin and the surface of the flange portion, so that the inductance A decrease in value can be suppressed.

According to the surface mount choke coil of the present invention, when the magnetic powder-containing resin is thermally expanded, damage to the flange portion of the drum core and generation of internal stress in the winding core portion through the flange portion are suppressed, and the inductance value is reduced. An object of the present invention is to provide a surface mount choke coil which is less likely to be lowered. The above object and other objects, structural features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.

Hereinafter, a first embodiment of a surface mount choke coil according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view for explaining the internal structure of the surface mount choke coil 10 of the first embodiment. FIG. 1A is a longitudinal sectional view of a main part showing the internal structure of the surface mount choke coil 10 of the embodiment, and FIG. 1B shows the magnetic flux and magnetic powder inside the surface mount choke coil 10 of the embodiment. It is a longitudinal cross-sectional view of the principal part which shows the mode of the displacement at the time of the thermal expansion of the containing resin.

As shown in FIG. 1A, the surface mount choke coil 10 of this embodiment includes a drum core 14 made of a soft magnetic material and a coil conductor 15 wound around the drum core 14. Further, the end portions of the coil conductor 15 (not shown) are conductively fixed to terminal electrodes (not shown) fixed to the bottom surface of the lower collar portion 13 of the drum core 14, respectively. More specifically, the end of the coil conductor 15 is secured to the terminal electrode with a conductor via a conductive bonding material such as solder or conductive adhesive, or directly by thermocompression bonding. Specifically, the surface mount choke coil 10 according to the present embodiment includes a core 11, an upper collar 12 provided at the upper end of the core 11, and a lower collar provided at the lower end of the core 11. And a coil conductor 15 wound around the winding core portion 11. Further, taper portions 12a and 13a are formed on the surfaces of the upper collar portion 12 and the lower collar portion 13 of the drum core 14 facing the other collar portions of the collar portions 12 and 13, respectively, and the wound coil conductor. An enlarged region A is provided in which the distance between the facing flanges 12 and 13 increases as the distance from the outer peripheral surface of the radial member 15 increases in the radial direction. Specifically, as compared with the distance h11 between the upper collar portion 12 and the lower collar portion 13 in the vicinity of the outer circumferential surface of the coil conductor 15, the upper collar as the distance from the outer circumferential surface of the coil conductor 15 increases in the radial direction. The space h12 between the portion 12 and the lower collar portion 13 is increased, and the enlarged region A is provided. A taper portion 12a is formed in an annular shape at an angle θ12 on the surface of the upper collar portion 12 that faces the lower collar portion 13 of the enlarged region A. Similarly, the surface of the lower flange portion 13 that faces the upper flange portion 12 of the enlarged region A is tapered at an angle θ13.
3a is formed in an annular shape. And the upper collar part 12 and the lower collar part 13 which are formed so that the space | interval between the collar parts 12 and 13 which oppose as it leaves | separates to the radial direction from the outer peripheral surface of the wound coil conductor 15 and the said A magnetic powder-containing resin 16 is inserted into an enlarged region A surrounded by the wound outer peripheral surface of the coil conductor 15. The distance h11 between the upper flange portion 12 and the lower flange portion 13 in the vicinity of the outer peripheral surface of the coil conductor 15 and the upper flange near the outer periphery of the magnetic powder-containing resin 16 that is radially separated from the outer peripheral surface of the coil conductor 15. The dimensional difference between the gap 12 between the part 12 and the lower collar part 13 is, for example, the outer shape of the upper collar part 12 and the lower collar part 13 is 4 mm square, the thickness of the collar part is 0.30 mm, and the core part 11. When the diameter is 2.0 mm, about 0.01 mm to 0.1 mm is preferable.

Further, in the surface mount choke coil 10 of the present embodiment, the magnetic powder-containing resin 16 is separated from the outer peripheral surface of the wound coil conductor 15 in the radial direction along the surfaces of the flange portions 12 and 13. As a result, the thickness h increases in cross section. More specifically, the magnetic powder-containing resin 16 is radially spaced from the outer peripheral surface of the coil conductor as compared to the thickness dimension h11 on the side in contact with the outer peripheral surface of the coil conductor 15. The thickness dimension h12 near the outer periphery is large.

Further, in the surface mount choke coil 10 according to the present embodiment, the upper flange portion 12 and the lower portion where the interval increases as the magnetic powder-containing resin 16 moves away from the outer peripheral surface of the wound coil conductor 15 in the radial direction. It is discharged between the flanges 13 and cured.

Further, in the surface mount choke coil 10 of the present embodiment, the magnetic powder-containing resin 16 is separated from the coil conductor 15 in the radial direction as indicated by a broken line 16B ′ in FIG. Displaces in the direction.

A preferred embodiment of the drum core 14 is as follows. That is, the drum core 14 is preferably made of a soft magnetic material, and more preferably a high permeability magnetic material mainly composed of Ni—Zn ferrite, Ni—Zn—Cu ferrite, or the like. The magnetic material powder and the binder are mixed and granulated, and then formed into a prismatic shaped body using a powder molding press, and at a predetermined angle θ on at least one of both main surfaces near the rotation axis. A recess is formed by centerless polishing using a grinding disk having a taper portion, and a drum-shaped molded body is obtained. Next, after the obtained drum-shaped molded body is debindered at around 800 ° C., the drum core 14 is obtained by firing at a predetermined temperature according to the sintering temperature of the magnetic material. Further, the drum-shaped molded body is not limited to a method obtained by forming a concave portion on the peripheral side surface of the prismatic molded body by centerless polishing. For example, after the granulation in the same manner as described above, the powder It can also be obtained by dry integral molding using a molding press. The drum core is not limited to a method of preparing and firing a drum-shaped molded body in advance.For example, after preparing a columnar molded body in the same manner as described above, a debinding treatment is performed in the same manner as described above. After firing at a predetermined temperature, the concave portion may be formed by cutting using a diamond wheel or the like on the peripheral side surface of the prismatic sintered magnetic body.

The core part 11 of the drum core 14 is preferably substantially circular or circular in cross section so that the length of the coil conductor necessary for obtaining a predetermined number of turns can be shortened, but is not limited to this. In the case of creating a drum-shaped molded body by dry integral molding, it can be changed as appropriate in consideration of the durability of the mold and the ease of deburring. The outer shape of the lower collar portion 13 is preferably a quadrangle or a quadrangle in plan view in order to reduce the size in response to high-density mounting. There may be. Further, the outer shape of the upper collar part 12 is preferably similar to the lower collar part 13 in order to reduce the size corresponding to high-density mounting, and the same size as the lower collar part 13 or the same A slightly smaller size than the lower collar 13 is preferable. Further, it is preferable to chamfer the four corners of the upper collar portion 12 in order to facilitate the insertion of the magnetic powder-containing resin 16 described later between the collar portions 12 and 13.

The drum core 14 includes a winding core portion 11, an upper flange portion 12 provided at the upper end of the winding core portion 11, and a lower flange portion 13 provided at the lower end of the winding core portion 11. It is preferable that an enlarged region A is provided in which the distance between the flanges 12 and 13 facing each other increases as the distance from the outer peripheral surface of the coil conductor 15 in the radial direction increases. Specifically, the enlarged region A is provided by forming a tapered portion on a surface of the upper collar portion 12 and the lower collar portion 13 that faces the other collar portion of at least one collar portion. Is preferred. For example, at least one of the upper collar portion 12 and the lower collar portion 13 of the enlarged region A in which the magnetic powder-containing resin 16 is inserted is arranged in the radial direction from the outer peripheral surface of the coil conductor 15. You may form in a cup shape so that the space | interval between the collar parts 12 and 13 which oppose may expand as it leaves | separates. Moreover, although the said upper collar part 12 and the lower collar part 13 may provide the said taper part only in the expansion area | region A in which the said magnetic powder containing resin 16 is inserted, or it may form in the said cup shape, it is limited to this. The taper portion may be provided from the base end portion on the winding core portion 11 side to the vicinity of the outer peripheral edge of the upper collar portion 12 and the lower collar portion 13 or may be formed in the cup shape. . The shape of the drum core 14 can be arbitrarily formed by appropriately selecting the shape of the molded body (the shape of the mold corresponding to the molded body) and the cutting conditions. In the cup shape, the upper collar part and / or the lower collar part has substantially the same thickness from the end part on the winding core part side to the outer peripheral part. For this reason, if it is cup-shaped, the damage of a collar part can be suppressed rather than the collar part which provided the taper part. Moreover, the thickness of the upper collar part 12 and the lower collar part 13 is preferably 0.5 mm or less in order to provide a low-profile surface-mounted choke coil. On the other hand, the lower limit value of the thickness of the upper collar part 12 and the lower collar part 13 is predetermined in consideration of the overhanging dimensions of the upper collar part 12 and the lower collar part 13 from the winding core part 11 in the drum core 14. It is preferable to set so as to satisfy the above strength.

Next, a preferred embodiment of the coil conductor 15 is as follows. That is, the coil conductor 15 is wound around the core portion 11 of the drum core 14 and is preferably an insulation-coated conductor, such as a polyurethane resin-coated copper wire, a polyester resin-coated copper wire, or an enamel resin-coated wire. A conducting wire or the like is more preferable. Further, the metal wire of the coil conductor 15 is not limited to a single wire, and may be a stranded wire. Further, the metal wire of the coil conductor 15 is not limited to a circular cross-sectional shape, and for example, a rectangular wire having a rectangular cross-sectional shape or a square wire having a square cross-sectional shape can be used. Moreover, you may use the self-bonding wire which coat | covered the outer periphery of the said insulation coating conducting wire with low melting-point resin.

Next, a preferred embodiment of the magnetic powder-containing resin 16 is as follows. That is, the magnetic powder-containing resin 16 preferably has viscoelasticity in the operating temperature range of the surface mount choke coil 10. More specifically, a magnetic powder-containing resin having a glass transition temperature of −20 ° C. or lower in the process of transition from a glass state to a rubber state in a change in rigidity with respect to temperature as a physical property at curing is preferable, and temperature as a physical property at curing is temperature. More preferable is a magnetic powder-containing resin having a glass transition temperature of −50 ° C. or lower in the process of transition from the glass state to the rubber state in the change in the rigidity ratio. The resin used for the magnetic powder-containing resin 16 is preferably a silicone resin, and the lead time of the step of inserting the magnetic powder-containing resin 16 between the flanges 12 and 13 can be shortened, so that epoxy resin and carboxyl group-modified propylene are used. A mixed resin with glycol is more preferable.

Next, various magnetic powders can be used as the magnetic powder used for the magnetic powder-containing resin 16. Specifically, one or more selected from Ni—Zn ferrite powder, Ni—Zn—Cu ferrite powder, Mn—Zn ferrite powder, metal magnetic powder, and the like are mixed. Are preferably used. The particle size of the magnetic powder is preferably 5 to 20 μm. In addition, the content of the magnetic powder in the magnetic powder-containing resin 16 is preferably 30 to 85 wt%.

An example of a method of inserting the magnetic powder-containing resin 16 onto the outer peripheral surface of the coil conductor 15 wound around the core part 11 of the drum core 14 includes the upper collar part 12, the lower collar part 13, and the winding The magnetic powder is formed in an enlarged region A between the upper collar portion 12 and the lower collar portion 13 that is surrounded by the outer peripheral surface of the coiled coil conductor 15 and increases in distance as it is separated from the coiled coil conductor 15. The paste of the contained resin is discharged using a dispenser or the like and cured.

Another example of the method of inserting the magnetic powder-containing resin 16 onto the outer peripheral surface of the coil conductor 15 wound around the winding core portion 11 of the drum core 14 is the outer peripheral surface of the coil conductor 15 in advance. The upper collar portion 12 is formed into an annular shape having a cross-sectional shape similar to that of a so-called V-belt whose thickness dimension increases as the distance from the outer periphery of the coil conductor 15 increases. And the lower collar 13.

In addition, a preferred embodiment of the terminal electrode is as follows. That is, the terminal electrode is preferably disposed on the bottom surface of the lower flange portion 13 of the column core 14 although not shown. As the terminal electrode, for example, a thick film type terminal electrode obtained by applying a baking-type electrode paste mainly composed of Ag powder and zinc borosilicate glass frit by screen printing or the like and baking it is preferable. . Moreover, it is not limited to this, For example, the electroconductive metal plate made into the predetermined shape by punching press molding may adhere to the bottom face of the said lower collar part 13 with an adhesive agent etc.

(Example) Ni-Zn-Cu-based ferrite powder was used as a magnetic material for the drum core, and an organic binder for powder molding was mixed to prepare a prismatic shaped body, and a taper angle was provided near the central axis. A concave portion is formed on the peripheral side surface of the molded body using a grinding wheel, debinding treatment is performed at 800 ° C., and then fired at 1050 ° C., so that the outer shape of the upper collar portion and the lower collar portion is 4.0 mm square. A square drum core having a height of 1.05 mm including the thickness of the part, a diameter of the core part of 2.0 mm, and an inner diameter of the taper part of Φ3.0 mm was obtained. A conductive paste containing Ag powder and zinc borosilicate glass frit was applied to the bottom surface of the obtained drum core by screen printing, baked at 650 ° C., and further subjected to copper plating to form a pair of terminal electrodes. . Next, a polyurethane-coated copper wire having an outer diameter of 100 μm was wound around the core portion of the drum core for 10 turns, and both ends of the coil conductor were conductively fixed to the terminal electrode by soldering. Next, 50% by weight of an Mn—Zn ferrite powder, 5% by weight of a curing agent, and 10% by weight of a solvent are mixed with a resin in which an epoxy resin and a carboxyl group-modified propylene glycol are mixed at a weight ratio of 50:50. Preparing a magnetic powder-containing resin paste, and using a dispenser between the upper collar part and the lower collar part where the interval increases as the distance from the outer peripheral surface of the wound coil conductor increases in the radial direction, A surface mount choke coil was obtained by heating at 150 ° C. for 1 hour to cure. The obtained surface-mounted choke coil had a cross-sectional shape in which the thickness dimension increased as the magnetic powder-containing resin separated from the outer peripheral surface of the wound coil conductor in the radial direction. Further, in the obtained surface mount choke coil, in the heat cycle test at 85 ° C. to −25 ° C. 10 times, the occurrence of cracks in the buttock by visual observation was 0 out of 10; The surface mount choke coil of the comparative example prepared in the same manner except that the taper part is not provided in the lower part and the lower collar part is five out of ten, and the reliability with respect to the temperature change is improved as compared with the comparative example. It was confirmed that Further, as a result of measuring the rate of change ΔL of the inductance value at 85 ° C. when the inductance value at room temperature of the surface mounting choke coil of the above example and the surface mounting choke coil of the comparative example is 100, the surface mounting choke coil of the example is measured. In comparison, the surface mount choke coil of the comparative example was 6%.
It was confirmed that the decrease in the inductance value was suppressed as compared with the comparative example.

Next, a second embodiment of the surface mount choke coil of the present invention will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of a main part showing the internal structure of the surface mount choke coil 20 of the second embodiment.

As shown in FIG. 2, the surface mount choke coil 20 of this embodiment includes a drum core 24 made of a soft magnetic material and a coil conductor 25 wound around the drum core 24. The ends of the coil conductor 25 (not shown) are conductively fixed to terminal electrodes (not shown) fixed to the bottom surface of the lower flange 23 of the drum core. More specifically, the end portion of the coil conductor 25 is directly connected to the end of the coil conductor 25 through a conductive bonding material such as solder or conductive adhesive, or by thermocompression bonding, as in the first embodiment. A conductor is fixed to the terminal electrode. Specifically, the surface mount choke coil 20 according to the present embodiment includes a winding core portion 21, an upper flange portion 22 provided at the upper end of the winding core portion 21, and a lower flange provided at the lower end of the winding core portion 21. A drum core 24 including a portion 23, and a coil conductor 25 wound around the core portion 21. Further, a taper portion 23 a is formed on a surface of the drum core 24 that faces the other collar portion of the upper collar portion 22 and the lower collar portion 23, and the outer periphery of the wound coil conductor 25. An enlarged region B is provided in which the distance between the facing flanges 22 and 23 increases as the distance from the surface increases in the radial direction. Specifically, the upper collar portion closer to the outer periphery separated from the outer peripheral surface of the coil conductor 25 than the distance h21 between the upper collar portion 22 and the lower collar portion 23 in the vicinity of the outer peripheral surface of the coil conductor 25. An interval h22 between 22 and the lower collar portion 23 is increased. The enlarged region B of the lower collar portion 23 is formed in a cup shape with the winding core portion 21 as a base at an angle θ23. And the upper collar part 22 and the lower collar part 23 which are formed so that the space | interval between the collar parts 22 and 23 which oppose as it leaves | separates to the radial direction from the outer peripheral surface of the wound coil conductor 25, A magnetic powder-containing resin 26 is charged in an enlarged region B surrounded by the wound outer surface of the coil conductor 25.

Further, in the surface mount choke coil 20 according to the present embodiment, the magnetic powder-containing resin 26 is radially separated from the outer peripheral surface of the wound coil conductor 25 along the surfaces of the flange portions 22 and 23. As the thickness dimension h increases, the cross-sectional shape increases. More specifically, the magnetic powder-containing resin 26 is separated from the outer peripheral surface of the coil conductor 25 in the radial direction compared to the thickness dimension h21 on the side in contact with the outer peripheral surface of the coil conductor 25. The thickness dimension h22 near the outer periphery of 26 is large.

Further, in the surface mount choke coil 20 of the present embodiment, the magnetic powder-containing resin 26 has an upper flange portion 22 and a lower portion whose intervals increase as the distance from the outer peripheral surface of the wound coil conductor 25 increases in the radial direction. It is discharged between the flanges 23 and cured.

The surface mount choke coil 20 of this embodiment is different from the surface mount choke coil 10 of the previous embodiment in that only the lower collar portion 23 of the upper collar portion 22 and the lower collar portion 23 is based on the winding core portion 21. It is formed into a cup shape. And between the said upper collar part 22 and the lower collar part 23 which are formed so that the space | interval between the collar parts 22 and 23 which oppose as it leaves | separates from this core part 21 around the said core part 21 may be expanded. A coil conductor 25 is wound therebetween. Other configurations and operational effects are the same as in the first embodiment, and a description thereof will be omitted.

Next, a third embodiment of the surface mount choke coil of the present invention will be described with reference to FIG. FIG. 3 is a longitudinal sectional view of an essential part showing the internal structure of the surface mount choke coil 30 of the third embodiment.

As shown in FIG. 3, the surface mount choke coil 30 of this embodiment includes a drum core 34 made of a soft magnetic material and a coil conductor 35 wound around the drum core 34. Further, the end portions of the coil conductor 35 (not shown) are conductively fixed to terminal electrodes (not shown) fixed to the bottom surface of the lower flange portion 33 of the drum core 34, respectively. More specifically, the end of the coil conductor 35 is directly connected to the end of the coil conductor 35 through a conductive bonding material such as solder or conductive adhesive, as in the first and second embodiments, or by thermocompression bonding. A conductor is fixed to the terminal electrode. Specifically, the surface-mounted choke coil 30 of the present embodiment includes a core 31, an upper collar 32 provided at the upper end of the core 31, and a lower collar provided at the lower end of the core 31. The drum core 34 includes a portion 33 and a coil conductor 35 wound around the winding core portion 31. Further, taper portions 32a and 33a are formed on the surfaces of the upper and lower flange portions 32 and 33 of the drum core 34 which face the other flange portions of the upper and lower flange portions 32 and 33, respectively, and the wound coil is formed. As the distance from the outer peripheral surface of the conductor 35 in the radial direction increases, the interval between the flanges 32 and 33 facing each other increases. Specifically, compared to the distance h31 between the upper flange portion 32 and the lower flange portion 33 in the vicinity of the outer peripheral surface of the coil conductor 35, the outer peripheral surface of the coil conductor 35 that is radially spaced from the outer peripheral surface. An interval h32 between the upper collar portion 32 and the lower collar portion 33 is increased. On the surface of the upper collar portion 32 of the drum core 34 facing the lower collar portion 33, a tapered portion 32a is formed in an annular shape at an angle θ32. Similarly, a taper portion 33a is formed in an annular shape with an angle θ33 on the surface of the lower collar portion 33 of the drum core 34 that faces the upper collar portion 32. And the magnetic powder containing resin 36 is inserted in the expansion area | region C where the space | interval between the collar parts 32 and 33 which oppose as it leaves | separates from the outer peripheral surface of the said coiled coil conductor 35 is expanded.

Further, in the surface mount choke coil 30 of the present embodiment, the magnetic powder-containing resin 36 is separated in the radial direction from the outer peripheral surface of the wound coil conductor 35 along the surfaces of the flange portions 32 and 33. As the thickness dimension h increases, the cross-sectional shape increases. More specifically, the magnetic powder-containing resin 36 is separated from the outer peripheral surface of the coil conductor 35 in the radial direction as compared with the thickness dimension h31 on the side in contact with the outer peripheral surface of the coil conductor 35. The thickness dimension h32 near the outer periphery of 36 is large.

Further, in the surface mount choke coil 30 of the present embodiment, the magnetic powder-containing resin 36 has a so-called V-belt-shaped cross section and is formed in an annular shape in advance and has a radius from the outer peripheral surface of the wound coil conductor 35. It is fitted between the upper collar part 32 and the lower collar part 33 whose distances increase as they are separated in the direction.

The surface mount choke coil 30 of the present embodiment is different from the surface mount choke coil 10 of the first embodiment in that the upper flange portion 32 and the lower flange portion 33 are arranged on the outer peripheral portion of the coil conductor 35 on which the winding is performed. The base end portion is formed in a dish shape having taper angles θ32 and θ33, respectively. Further, as described above, the magnetic powder-containing resin 36 is previously formed into an annular shape having a so-called V-belt-shaped cross section, and the interval increases as the distance from the outer peripheral surface of the wound coil conductor 35 in the radial direction increases. It is fitted between the collar part 32 and the lower collar part 33. Other configurations and operational effects are the same as in the first embodiment, and a description thereof will be omitted.

In addition, in the principal part sectional drawing of each said embodiment, although the coil conductor was abbreviate | omitted and described, while the outer peripheral surface of the wound coil conductor has some unevenness | corrugations, there is a little clearance gap between each conductor, respectively. Remains. For this reason, in the first and second embodiments, the magnetic powder-containing resin is inserted into a slight gap between the wound coil conductors. It's not different.

The present invention is suitable for a surface mount choke coil used for various portable and thin electronic devices.

It is a longitudinal cross-sectional view of the principal part which shows 1st Embodiment of the surface mount choke coil of this invention. It is a longitudinal cross-sectional view of the principal part which shows 2nd Embodiment of the surface mount choke coil of this invention. It is a longitudinal cross-sectional view of the principal part which shows 2nd Embodiment of the surface mount choke coil of this invention. It is a longitudinal cross-sectional view of the principal part which shows an example of background art. It is a longitudinal cross-sectional view of the principal part which shows the other example of background art.

Explanation of symbols

10: surface mount choke coil 11: core portion 12: upper flange portion 12a: taper portion 13: lower flange portion 13a: taper portion 14: drum core 15: coil conductor 16: magnetic powder-containing resin 16 ': magnetism during thermal expansion Powder-containing resin 20: Surface mount choke coil 21: Core portion 22: Upper flange portion 23: Lower flange portion 23a: Tapered portion 24: Drum core 25: Coil conductor 26: Magnetic powder-containing resin 26 ': Magnetic powder during thermal expansion Containing resin 30: surface mount choke coil 31: core portion 32: upper flange portion 32a: taper portion 33: lower flange portion 33a: taper portion 34: drum core 35: coil conductor 36: magnetic powder-containing resin 36 ': during thermal expansion Magnetic powder-containing resin

Claims (4)

A drum core comprising a core part, an upper collar part provided at the upper end of the core part and a lower collar part provided at the lower end of the core part, and a coil conductor wound around the core part In the surface mount type choke coil having a taper portion formed on a surface facing the other flange portion of at least one flange portion of the upper flange portion and the lower flange portion of the drum core, the wound A surface characterized in that an enlarged region is provided in which the interval between the flanges facing each other increases as the distance from the outer peripheral surface of the coil conductor in the radial direction increases, and a magnetic powder-containing resin is charged in the enlarged region. Mounting choke coil. 2. The surface-mount choke coil according to claim 1, wherein the magnetic powder-containing resin has a cross-sectional shape in which a thickness dimension increases as the distance from the outer peripheral surface of the wound coil conductor in the radial direction increases. The magnetic powder-containing resin is discharged and cured between an upper collar part and a lower collar part, the interval of which increases as the distance from the outer peripheral surface of the wound coil conductor in the radial direction increases. 3. The surface mount choke coil according to claim 2, wherein The magnetic powder-containing resin is preliminarily molded into an annular shape, and is fitted between an upper collar part and a lower collar part, the interval of which increases as the distance from the outer peripheral surface of the wound coil conductor increases in the radial direction. 3. The surface mount choke coil according to claim 2, wherein the surface mount choke coil is provided.

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