JP2008288370A - Surface mounting inductor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductor and a manufacturing method thereof in which an inductance and a manufacturing cost equivalent to those in a conventional item, a DC electric resistance less than that in a conventional item, and a countermeasure against larger current are achieved, in a low-profile inductor especially having a thickness of 1 mm or less. <P>SOLUTION: This surface mounting inductor has a coil structure capable of avoiding magnetic saturation suitable for the low-profile inductor by arranging lower permeability layers 1 and higher permeability layers 2 consisting of soft magnetic materials of different relative magnetic permeabilities in the predetermined locations around a coil 3. This method can achieve this structure at a cost equivalent to that of the conventional structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a configuration of a small inductor used in a power supply circuit of a small electronic device and a manufacturing method thereof.

  In portable electronic devices such as mobile phones, notebook computers, and small game machines, in addition to increasing functions, it is required to maintain and improve the power supply duration. As a result, the inductor, which is one of the power circuit elements, has been downsized. In recent years, demand for high current and low loss has been increasing. In order to reduce the size and loss of an inductor, it is extremely important to make the coil core less susceptible to magnetic saturation, to reduce the DC electrical resistance of the coil winding, and to use a core material with a small core loss. is there.

  In order to achieve such an object, as an inductor used in a power supply circuit of a portable electronic device, a winding is applied to a soft magnetic ferrite drum having ridges on both sides of the winding core, and the soft magnetic is wound around the drum. A configuration in which a ferrite ring is arranged has been used. However, in this configuration, the smaller the size and the lower the height, the more precisely the gap width provided between the ferrite drum core and the ferrite ring needs to be managed in order to adjust the inductance. In combination with this, there is a drawback that it is difficult to reduce the cost.

  Further, there is also used a configuration in which a soft magnetic ferrite drum having ridges on both sides of a winding core is wound and a mixture of a soft magnetic material and a resin is disposed around the drum. However, in this configuration, from the viewpoints of avoiding magnetic saturation and maintaining bending strength, the ferrite in the collar portion needs to have a thickness of at least 0.2 mm on one side, and to allow a DC bias current of 1 A or more. Needs to have a DC electric resistance of 150 mΩ or less using a copper wire having a diameter of 0.1 mm or more, so it is difficult to realize a large current of 1 A or more with an inductor thinner than about 1 mm. (Patent Document 1).

  In recent years, in order to meet the demand for lower inductors, a winding is applied to a soft magnetic ferrite core having a flange on only one side of the core, and the periphery of the winding is covered with a mixture of a soft magnetic material and a resin. A configuration is also proposed. However, in this configuration, since the relative magnetic permeability of the soft magnetic material disposed on the side having no defects is low, an inductor having a sufficiently large inductance cannot be realized, and the leakage magnetic flux is increased (patent) Reference 2).

  In addition, as a means to meet the contradictory demands for downsizing and large current, a proposal has been made to eliminate the waste of volume in the winding part by using a flat wire as the winding, but when using a flat wire, There are drawbacks associated with increased material costs and complicated manufacturing processes (Patent Document 3).

  Furthermore, in order to realize a low profile, a configuration in which a coil pattern is sandwiched between a flat ferrite sintered body or a flat soft magnetic powder mixed resin has been proposed, but the winding is a winding portion having a high relative permeability. Therefore, there is a disadvantage that an inductance of about 2.2 μH or more can be obtained and a large current of 1 A or more cannot be handled (Patent Document 4).

Japanese Patent Laid-Open No. 2005-210055 JP 2005-150470 A JP 2006-165429 A JP 2004-14837 A

  Conventionally, it has been difficult to achieve a large current of 1 A or more in a portable electronic device inductor having a thickness of about 1 mm or less and a manufacturing cost comparable to that of a conventional product. The present invention realizes an inductance equivalent to that of a conventional product and a manufacturing cost, particularly in a low-profile inductor having a thickness of 1 mm or less, and has a DC electric resistance lower than that of a conventional product, and an inductor that can handle a larger current and its manufacturing. A method is provided.

  To achieve the above object, the present invention provides a coil-mounted surface mount inductor that is suitable as a low-profile inductor and can avoid magnetic saturation by arranging soft magnetic materials having different relative magnetic permeability around a conductor coil. And the manufacturing method which can implement | achieve the coil structure at the cost equivalent to a conventional structure is proposed.

  The present invention comprises at least three or more layers of soft magnetic material, the surface on which the soft magnetic material layer is disposed so as to be substantially perpendicular to the central axis of the coil around which the conductor is wound and sandwich the coil. A mounted inductor, wherein a first soft magnetic layer having a relative permeability of 3 or more and less than 40 is disposed between second soft magnetic layers having a relative permeability of 50 or more. It is a surface mount inductor.

  The present invention is also a surface mount inductor characterized in that a soft magnetic material having a relative magnetic permeability of 50 or more is disposed in the internal space of the coil.

  According to the present invention, at least one of the second soft magnetic layers is composed of a mixture layer of a soft magnetic powder having a flat shape and a binder, and has an in-plane easy magnetization direction. This is a featured surface mount inductor.

  According to the present invention, in the surface mount inductor, at least one of the second soft magnetic layers is made of soft magnetic ferrite.

  The present invention is also characterized in that at least one of the second soft magnetic layers is a ferrite sintered body having a T-shaped cross section including the central axis of the coil continuous to the coil inner space. It is a surface mount inductor.

  According to the present invention, at least one of the second soft magnetic layers is a soft magnetic metal powder dust core having a T-shaped cross section including the central axis of the coil continuous to the coil inner space. It is a surface mount inductor characterized by being.

  In addition, the present invention provides the surface-mount inductor, wherein at least one of the mixture layers is a flexible sheet.

  The present invention is also a surface-mount inductor, wherein at least one of the mixture layers is formed by curing a flexible sheet-like mixture.

  Further, according to the present invention, when at least a part of the flat soft magnetic powder has a length in the major axis direction as a and a length in the minor axis direction as b, the value of a / b is 3 or more. The surface-mount inductor is characterized by a needle-like soft magnetic powder.

  Further, in the present invention, at least a part of the soft magnetic powder is an Fe-Si-Al alloy having a flat shape, and an in-plane direction of a layer formed by the mixture of the soft magnetic powder and a binder The surface mount inductor has a relative permeability of 50 or more.

  In addition, the present invention provides the surface mount inductor, wherein at least a part of the soft magnetic powder is an Fe—Si alloy having a magnetic flux density of 7000 G or more in the applied magnetic field 100 Oe.

  In addition, the present invention provides the surface mount inductor, wherein at least a part of the soft magnetic powder is an Fe—Si—Cr alloy having a magnetic flux density of 7000 G or more in the applied magnetic field 100 Oe.

  Further, the present invention is the surface mount inductor, wherein at least a part of the soft magnetic powder is a metallic glass having a magnetic flux density of 7000 G or more in the applied magnetic field 100 Oe.

  Further, according to the present invention, at least one of the mixture layers is in the form of a flexible sheet, and the mixture layer is laminated on a structure including at least one conductor coil, and then cut and separated by 1 A method for manufacturing a surface-mount inductor, comprising obtaining an inductor including a single conductor coil.

  Further, in the present invention, at least one of the mixture layers is a sheet having flexibility, and the mixture layer is laminated on a structure including at least one conductor coil, cured, and then cut. A method for manufacturing a surface-mount inductor, wherein an inductor including one conductor coil is obtained by separation.

  More specifically, first, in order to realize a large inductance with a smaller number of coil turns, as much as possible of the magnetic path formed by the soft magnetic material disposed around the conductor coil is subjected to relative permeability. Although it is desirable to use a soft magnetic material having a magnetic permeability of 50 or more, if the relative magnetic permeability of the entire magnetic path is high, magnetic saturation is likely to occur. Therefore, a portion of the soft magnetic material has a lower relative magnetic permeability. The body is effective. In order to easily realize a coil configuration in which different kinds of materials are combined in this way, a conductor coil made of a high permeability material and a low permeability layer (a layer made of a soft magnetic material having a relative permeability of 3 or more and less than 40 are used. (Hereinafter referred to as this)).

  In order to form the low magnetic permeability layer, a mixture of soft magnetic powder and binder is applied so as to cover the conductor coil by a thick film formation method, or a mixture of soft magnetic powder and binder is applied. What is necessary is just to form in a flexible sheet | seat shape and to crimp | bond and arrange this so that a conductor coil may be covered. The volume filling rate of the soft magnetic powder in the mixture of the soft magnetic powder and the binder can be easily set to about 60%. However, when a flexible sheet is used, the sheet is preliminarily molded under pressure. By doing so, the volume filling rate of the soft magnetic powder can be further improved, and the saturation magnetic flux density of the low magnetic permeability layer can be increased.

  The soft magnetic powder used for the mixture of the soft magnetic powder and the binder may be either ferrite powder or soft magnetic metal powder, but Fe-Si- having a saturation magnetic flux density of 7000 G or more in an external magnetic field of 100 Oe. It is more preferable to use soft magnetic metal powder such as Al-based alloy (Sendust), Fe-Si-based alloy, Fe-Si-Cr-based alloy, and Fe-Si-B-Nb-Al-C-based alloy (metallic glass). desirable. If a soft magnetic powder having a saturation magnetic flux density of 7000 G or more in the external magnetic field 100 Oe is used, the saturation magnetic flux density in the external magnetic field 100 Oe can be obtained even if the volume filling rate of the soft magnetic powder in the mixture of the soft magnetic powder and the binder is 60%. A layer having 4000 G or more can be formed. Since the saturation magnetic flux density in the ferrite sintered body is about 4000 G, if a soft magnetic powder having a saturation magnetic flux density of 7000 G or more in the external magnetic field 100 Oe is used, the direct current is larger than that in a conventional inductor using only ferrite. Magnetic saturation of the bias current can be avoided.

  A high magnetic permeability layer (a layer made of a soft magnetic material having a relative magnetic permeability of 50 or more is hereinafter referred to as this) can be formed by the same method as the low magnetic permeability layer, but only by increasing the volume filling rate of the soft magnetic powder. It is difficult to achieve a relative permeability of 50 or more. In order to obtain a layer with a high saturation magnetic flux density and a high relative magnetic permeability, a layer having a flat or needle-like soft magnetic powder and a binder and having an in-plane easy magnetization direction is used. desirable. A thick film forming method for obtaining a low-permeability layer or a high-permeability layer made of a mixture of a soft magnetic material and a binder is industrially established as a method for forming an electromagnetic noise absorber, and has a relative magnetic permeability of 50 or more. A high magnetic permeability layer can be easily formed.

  Further, the high magnetic permeability layer may be a flat plate of a ferrite sintered body.

  By forming the low-permeability layer and the high-permeability layer by the above-described method and pressing them so as to cover the conductor coil, the conductor coil and the soft magnetic body are integrated without requiring a complicated process. An inductor can be formed. In addition, a large number of inductors can be obtained at once by crimping so that a large number of arranged conductor coils are covered with a soft magnetic material by the above-described method, and then cutting and separating, thereby contributing to an improvement in production efficiency. Is big.

  In the inductor having the configuration according to the present invention, the inductor can be made lower without reducing the allowable bias current as compared with the conventional configuration in which the conductor coil is wound around the ferrite magnetic core having the flanges on both sides of the core. Can be turned upside down.

  Moreover, in the configuration according to the present invention, since the coil periphery is covered with a soft magnetic layer after the winding is completed, restrictions on the thickness of the winding are relaxed, and a thicker copper wire can be used even with the same inductor thickness, DC resistance can be reduced.

  Further, in the configuration of the inductor according to the present invention, since the magnetic core having the flanges on both sides of the winding core is not used, the magnetic core forming process can be simplified, and the yield deterioration due to the low profile of the inductor can be avoided. it can.

  Further, the configuration of the inductor according to the present invention is advantageous in that it is resistant to impact since the conductor coil, the high magnetic permeability layer, the low magnetic permeability layer, the magnetic core of the winding core and the like are integrated.

  In the configuration according to the present invention, when flexibility is imparted to both the low magnetic permeability layer and the high magnetic permeability layer, even if a non-flexible magnetic material is used for the core, the entire inductor is slightly Can be bent. When the inductor having the configuration according to the present invention is arranged on the film substrate, the inductor deforms following the bending of the film substrate, so that breakage of the inductor and peeling of the terminals can be prevented.

  A conductor coil is disposed on a mixture on a flat plate made of soft magnetic metal powder and a binder, or on a magnetic core having a ridge only on one side using ferrite. A mixture of soft magnetic metal powder and a binder is adhered so as to cover the entire periphery of the conductor, thereby forming a low magnetic permeability layer having a relative magnetic permeability of 3 or more and less than 40. Further, a mixture of flat metal powder and a binder or a flat ferrite sintered body is disposed so as to cover the mixture, and a high permeability layer having an in-plane relative permeability of 50 or more is formed. And an inductor. At this time, the high magnetic permeability layers are prevented from contacting each other directly.

  In the present invention, it is desirable to use a soft magnetic material having a relative permeability of 50 or more in the in-plane direction for any of the high permeability layers arranged in at least two layers. This is because, when the relative permeability is lower than this, the effect of simultaneously improving the inductance and the superimposition characteristics by forming different relative permeability layers cannot be obtained. Moreover, as a relative magnetic permeability of the low magnetic permeability layer, it is desirable to use a mixture having 3 or more and less than 40. This is because at a lower relative permeability, the thickness of the low relative permeability layer must be reduced to about 20 microns in order to improve the inductance, and the inductance due to the thickness variation of the low relative permeability layer This is because the variation of the above becomes remarkable.

  Next, the present invention will be described in more detail with specific examples. In the first embodiment, as the high permeability layer, the soft magnetic powder is Fe-Si-Al alloy (Sendust), the binder is polyamide resin, and the low magnetic permeability layer is Fe-Si. An example in which NiZ ferrite is used as a water atomized spherical powder of -B-Nb-Al-C-based alloy (metal glass), a polyamide-imide resin as a binder, and a soft magnetic core will be described. The reference drawing is FIG. 4 (e).

  First, in order to form the high magnetic permeability layer 22, an Fe—Si—Al alloy (Sendust) was prepared as a soft magnetic powder. In order to flatten the powder shape, the coarsely pulverized powder was subjected to centrifugation and pulverization using an attritor. Subsequently, in order to remove distortion generated in the flattening step, an annealing treatment was performed at 650 ° C. for 2 hours in a nitrogen atmosphere. Next, using xylene as a solvent, the soft magnetic powder and the polyamide-imide resin as a binder are mixed at a predetermined ratio to prepare a slurry, a sheet is formed by a doctor blade method, and dried at 60 ° C. for 2 hours. The solvent was removed.

  Next, in order to form the low magnetic permeability layer 11, a water atomized spherical powder of Fe—Si—B—Nb—Al—C alloy (metal glass) was prepared as a soft magnetic powder. Using xylene as a solvent, the soft magnetic powder and the polyamide-imide resin, which is a binder, are mixed at a predetermined ratio to produce a slurry, a sheet is formed by the doctor blade method, and dried at 60 ° C. for 2 hours to remove the solvent. did.

Next, in order to obtain a soft magnetic core 4 having a wrinkle only on one side, a NiZn ferrite powder was mixed with 10 wt% of a 9% aqueous solution of polyvinyl alcohol, and this powder was subjected to pressure molding at a pressure of 2000 kg / cm ² , After debinding, sintering was performed at 1200 ° C. in an air atmosphere. The soft magnetic core 4 having a ridge only on one side has a side of 3 mm, a core diameter of 1.2 mm, and a relative permeability of 500.

Subsequently, a coiled conductor having a diameter of 0.12 mm is wound around the obtained soft magnetic core 4 for 8 turns to form a coil 3, and both ends of the winding are joined to the metallized portion on the surface having no core by soldering. did. A low magnetic permeability layer 11 (relative magnetic permeability 12) containing metallic glass spherical powder cut into 3 mm square is disposed as a first sheet so as to cover the coil and the core part. A high permeability layer 22 (relative permeability 100) containing flat powder of Sendust cut to 3 mm square is arranged as a second sheet so as to cover, together with the winding part under the conditions of 500 g / cm ² and 180 ° C. An inductor was manufactured by pressure bonding to the soft magnetic core 4 (ferrite core) (FIGS. 4A to 4E). As comparative examples, inductor comparative products 1 to 3 having the configuration shown in Table 1 were manufactured. Table 1 shows the inductor configurations and inductor characteristics of the product of the present invention and the comparative product.

  As shown in Table 1, when a low permeability layer having a relative permeability of 12 is arranged between a high permeability layer having a relative permeability of 100 and a ferrite core having a ridge only on one side, Compared to the NiZn ferrite drum core 6 having ridges on both sides, magnetic saturation does not occur even under a larger bias current, and a large inductance is maintained. That is, it can be seen that the DC superposition characteristics of the inductor having the configuration according to the present invention are good.

  In the second embodiment, as a high magnetic permeability layer, a ferrite flat plate, as a low magnetic permeability layer, soft magnetic powder is Fe-Si-Cr alloy water atomized spherical powder, binder is epoxy resin, soft magnetic core An example using NiZn ferrite will be described. The reference drawing is FIG. 4 (e).

First, in order to form the low permeability layer 11 by coating, water atomized spherical powder of Fe—Si—Cr alloy is prepared as magnetic powder, mixed with epoxy resin as a binder, and the relative permeability after drying Was adjusted to be less than 3 to prepare a paste for coating. Next, in order to obtain a soft magnetic core 4 (ferrite core) having a ridge only on one side and a ferrite flat plate used as the high magnetic permeability layer 22, 10 wt% of a 9% aqueous solution of polyvinyl alcohol is mixed with NiZn ferrite powder. The powder was subjected to pressure molding at a pressure of 2000 kg / cm ² , and after binder removal treatment, sintered at 1200 ° C. in an air atmosphere. A magnetic core having a ridge only on one side has a shape of 3 mm on one side, a diameter of a core of 1.2 mm, and Masataka Takagi 0.25 mm. A ferrite flat plate has a side of 3 mm and a thickness of 0.3 mm. It has a magnetic permeability of 500.

  A coil lead having a diameter of 0.12 mm was wound around the winding core of the soft magnetic core 4 for 7 turns to form a coil 3, and both ends of the winding were joined to a metallized portion on the surface having no winding core with solder. This magnetic core was placed in a mold for paste application, and a paste containing an Fe—Si—Cr alloy was applied so as to cover the coil 3 and the core part. After adjusting the coating thickness of the paste on the core as shown in Table 2, a 3 mm square NiZn ferrite flat plate is placed on the coated paste and epoxy resin is used at 150 ° C. for 30 min. Were cured, and a NiZn ferrite flat plate was bonded to obtain Invention Product 2 and Invention Product 3. Table 2 shows the inductance characteristics of the product 2 of the present invention and the product 3 of the present invention together with the inductance characteristics of the comparative product 5 and the comparative product 6 in which the relative permeability of the low permeability layer is less than 3.

  As shown in Table 2, when the relative permeability of the magnetic paste constituting the low permeability layer is less than 3, the absolute value of the inductance when the distance between the ferrite core with the winding and the ferrite plate fluctuates ± 5 μm. Fluctuates by ± 15% or more. Generally, the inductance of a product is required to be a value within ± 20% from a specification value. On the other hand, from the viewpoint of improving the yield, it is desirable that a variation of ± 5 μm is allowed for the distance between the high permeability layers. From Table 2, if the relative permeability of the low permeability layer is 3 or more and less than 40, even if the distance between the high permeability layers fluctuates up to ± 5 μm, the fluctuation range of the inductance may be less than ± 20%. It is possible to improve the yield.

The figure which shows typically the structure of the surface mount inductor concerning this invention, Fig.1 (a) is a perspective view, FIG.1 (b) is sectional drawing. The figure which shows typically the structure of the surface mount inductor concerning this invention, Fig.2 (a) is a perspective view, FIG.2 (b) is sectional drawing. Sectional drawing which shows typically the structure of the surface mount inductor concerning this invention. Sectional drawing which shows the structure typically about the Example and comparative example of a surface-mount inductor concerning this invention. 4 (a) to 4 (d) are cross-sectional views of a comparative example, and FIG. 4 (e) is a cross-sectional view of an embodiment according to the present invention. Sectional drawing which shows the conventional inductor which has a ridge on both sides of a core part. Sectional drawing which shows the conventional inductor which has a collar only in the one side of a core part, and coat | covered the coil part with the single kind of soft magnetic resin. The conceptual diagram of the manufacturing method of the surface mount inductor concerning this invention.

Explanation of symbols

1 Low permeability layer (first soft magnetic layer)
2 High permeability layer (second soft magnetic layer)
3 Coil 4 Soft magnetic core 5 Soft magnetic resin 6 NiZn ferrite drum core
11 Low permeability layer 12 (of the first sheet) High permeability layer 13 (of the first sheet) Low permeability layer 21 (of the first sheet) Low permeability layer 22 (of the second sheet) ) High permeability layer

Claims (15)

  A surface-mount inductor comprising at least three or more soft magnetic layers, wherein the soft magnetic layer is disposed so as to be substantially perpendicular to the central axis of the coil around which the conductor is wound and to sandwich the coil. And a first soft magnetic layer having a relative magnetic permeability of 3 or more and less than 40 is disposed between the second soft magnetic layers having a relative magnetic permeability of 50 or more. .   The surface mount inductor according to claim 1, wherein a soft magnetic material having a relative magnetic permeability of 50 or more is disposed in an internal space of the coil.   The at least one layer of the second soft magnetic layer is composed of a mixture layer of a soft magnetic powder having a flat shape and a binder, and has an in-plane easy magnetization direction. Or the surface mount inductor of 2.   4. The surface mount inductor according to claim 1, wherein at least one of the second soft magnetic layers is made of soft magnetic ferrite.   2. The ferrite sintered body according to claim 1, wherein at least one of the second soft magnetic layers is a ferrite sintered body having a T-shaped cross section including a central axis of a coil continuous with the coil inner space. 5. The surface mount inductor according to any one of 4 above.   At least one of the second soft magnetic layers is a dust core of soft magnetic metal powder having a T-shaped cross section including a central axis of a coil continuous with the coil inner space. The surface mount inductor according to any one of claims 1 to 4.   The surface-mount inductor according to claim 3, wherein at least one of the mixture layers is a sheet having flexibility.   The surface-mount inductor according to claim 3, wherein at least one of the mixture layers is formed by curing a sheet-like mixture having flexibility.   At least a part of the soft magnetic powder having the flat shape is a needle-like soft powder having a / b value of 3 or more, where a is the length in the major axis direction and b is the length in the minor axis direction. The surface-mount inductor according to claim 3, wherein the surface-mount inductor is a magnetic powder.   At least a part of the soft magnetic powder is a flat Fe-Si-Al alloy, and the relative magnetic permeability in the in-plane direction of the mixture layer composed of the soft magnetic powder and the binder is 50 or more. The surface mount inductor according to claim 3, wherein the surface mount inductor is provided.   The surface mount inductor according to any one of claims 3 to 6, wherein at least a part of the soft magnetic powder is an Fe-Si alloy having a magnetic flux density of 7000 G or more in an applied magnetic field 100 Oe.   The surface mount inductor according to any one of claims 3 to 6, wherein at least a part of the soft magnetic powder is an Fe-Si-Cr alloy having a magnetic flux density of 7000 G or more in an applied magnetic field 100 Oe.   7. The surface mount inductor according to claim 3, wherein at least a part of the soft magnetic powder is a metallic glass having a magnetic flux density of 7000 G or more in an applied magnetic field 100 Oe.   At least one layer of the mixture layer is in the form of a flexible sheet, and after laminating the mixture layer on a structure including at least one conductor coil, one conductor coil is formed by cutting and separating. 14. The method for manufacturing a surface mount inductor according to claim 3, wherein an inductor including the inductor is obtained.   At least one of the mixture layers is in the form of a flexible sheet, and the mixture layer is laminated on a structure including at least one conductor coil, cured, and then separated by cutting and separating. 14. The method of manufacturing a surface mount inductor according to claim 3, wherein an inductor including a conductor coil is obtained.

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