JP2007324554A - Laminated inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated inductor capable of providing a high inductance, while obtaining an action of suppressing passing of magnetic flux by a second insulating layer. <P>SOLUTION: The laminated inductor includes a laminate 11 comprising a plurality of laminated first insulation layers 11a, each made of a high-permeability magnetic body; at least one coil 15 where belt-like conductive layers 12 each formed, with each first insulation layer being connected together and formed in a spiral form inside the laminate 11; and the second insulating layer 13 with a permeability lower than that of the first insulating layer and tangent to the conductor layer, and the first insulating layer and the second insulating layer are arranged, such that the conductor layer formed to the first insulating layer is tangent to the second insulating layer, in the vicinity of at least an outer circumferential face between an inner circumferential face and the outer circumferential face of the coil in spiral and the outer circumference of the second insulation layer reaches an end face of the layered body so as to traverse the magnetic path of the coil at its outer circumferential side. Thus, the action of suppressing passing of the magnetic flux is obtained by the second insulation layer, and a large magnetic path cross-sectional area is ensured inside the coil and a high inductance is obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer inductor.

A multilayer inductor is obtained by laminating a magnetic layer having a high magnetic permeability and a conductor layer, and providing a spiral coil inside the multilayer body. When a direct current of a predetermined value or more is applied, a phenomenon occurs in which the inductance value of the multilayer inductor decreases due to magnetic saturation of the magnetic material. This phenomenon can be improved by opening a closed magnetic circuit type multilayer inductor, specifically by interposing a non-magnetic or low-permeability insulator layer between the magnetic layers of the multilayer body. It is.
Specifically, as shown in Background Art 1 (FIG. 6: Patent Document 1), the magnetic layers 101 and the conductors 102 are alternately stacked, and the conductors 102 are 1 to between the magnetic layers 101. There has been proposed an open magnetic circuit type laminated coil that is formed by forming two or more coils and in which a nonmagnetic insulating layer 103 is interposed between the magnetic layers 101. In this case, the conductor 102 and the nonmagnetic insulator layer 103 are in contact with each other in three directions around the conductor 102 forming the coil.
Further, as shown in Background Art 2 (FIG. 7: Patent Document 2), a magnetic ceramic layer 201 and a conductive layer 202 are laminated, and a spiral coil is provided in the magnetic ceramic, thereby providing the magnetic ceramic. There has been proposed a multilayer inductance element in which at least a part of a portion surrounded by the coil is made of a nonmagnetic insulator ceramic 203. In this case, the conductor layer 202 and the nonmagnetic insulator ceramic 203 are in contact with each other in one direction around the conductor layer 202.
JP-A-56-155516 JP-A-11-97245

  However, in the multilayer inductor of Background Art 1 in which the nonmagnetic insulator layer 103 is interposed between the magnetic layers 101, the nonmagnetic insulator layer 103 has a magnetic path inside and outside the multilayer inductor. In order to divide, there was a malfunction that an inductance value fell significantly. Further, in the multilayer inductor according to the background art 2 in which at least a part of the part surrounded by the coil of the magnetic ceramic 201 is made of the nonmagnetic insulating ceramic 203, the part surrounded by the coil of the magnetic ceramic 201 is used. The magnetic flux density is higher in the portion where the conductor layer 202 constituting the coil is in contact with the nonmagnetic insulator ceramic 203 than in the center. However, when the thickness of the nonmagnetic insulator ceramic 203 is reduced, the conductivity constituting the coil is increased. Since the contact state between the body layer 202 and the nonmagnetic insulator ceramic 203 becomes unstable, the nonmagnetic insulator ceramic 203 tends to vary in its action of suppressing the passage of magnetic flux, and when direct current is applied, Inductance value suddenly drops from the initial inductance value without the effect of improving the superimposition characteristics. There is a problem that occurs at a rate of 10-30%. On the other hand, when the thickness of the nonmagnetic insulator ceramic 203 is increased so as not to cause variations in the action of suppressing the passage of magnetic flux as described above, the magnetic path of the multilayer inductor is divided as in the multilayer inductor of the background art 1. Thus, the initial inductance value is inevitably lowered.

  An object of the present invention is to provide a multilayer inductor capable of obtaining a large inductance while obtaining an effect of suppressing the passage of magnetic flux by a second insulator layer.

In order to achieve the above object, the present invention provides:
(1) A laminate in which a plurality of first insulator layers made of a high permeability magnetic material and a strip-like conductor layer formed for each first insulator layer are connected to each other to form the laminate. A stack having at least one coil formed in a spiral shape and a second insulator layer having a permeability lower than that of the first insulator layer and in contact with the conductor layer In the inductor,
The conductor layer and the second insulator layer formed on the selected first insulator layer of the laminate at least in the vicinity of the outer circumference surface between the inner circumference surface and the outer circumference surface of the spiral coil. And the outer periphery of the second insulator layer reaches the end face of the laminated body and crosses the magnetic path outside the coil. (... hereinafter referred to as first problem solving means)

The main embodiment of the present invention is as follows.
(2) At least the thickness dimension of the conductor layer formed on the selected first insulator layer of the laminate in the vicinity of at least the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil. The conductor layer and the second insulator layer are in contact with each other so that a part thereof overlaps at least a part of the thickness dimension of the second insulator layer. (Hereinafter referred to as second problem solving means)

In addition, other embodiments of the present invention
(3) The second insulator layer may be provided only in an inner layer excluding both ends of a turning axis of the coil of the laminated body. (Hereinafter referred to as third problem solving means)

In addition, other embodiments of the present invention
(4) The plurality of second insulator layers are provided inside the stacked body independently of each other in the stacking direction. (Hereinafter referred to as fourth problem solving means)

  The operation of the first problem solving means is as follows. That is, at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil, the conductor layer formed on the selected first insulator layer of the laminate and the second insulation And the outer periphery of the second insulator layer reaches the end face of the laminated body and crosses the magnetic path outside the coil, and the second insulator layer provides magnetic flux. A large magnetic path cross-sectional area is secured inside the coil while obtaining the effect of suppressing the passage of the coil, so that a large inductance can be obtained and the number of coil turns required to obtain the same inductance value is small This is particularly suitable for a multilayer inductor having a low load current specification.

  The operation of the second problem solving means is as follows. That is, at least one of the thickness dimensions of the conductor layer formed on the selected first insulator layer of the laminate at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil. Since the conductor layer and the second insulator layer are in contact with each other so that the portion overlaps at least part of the thickness dimension of the second insulator layer, even if the second insulator layer is thinned The state in which the conductor layer and the second insulator layer are in contact with each other can be reliably obtained, and the second insulator layer can be prevented from causing variations in the action of suppressing the passage of magnetic flux. A multilayer inductor having a higher inductance value can be provided.

  The operation of the third problem solving means is as follows. That is, since the second insulator layer is provided only on the inner layer excluding both ends of the pivot axis of the coil of the laminate, the magnetic flux density tends to be high on the outer peripheral side of the coil inside the laminate. Since the second insulator layer is provided, concentration of magnetic flux density inside the stacked body can be suppressed, and local magnetic saturation can be prevented from occurring.

  The operation of the fourth problem solving means is as follows. In other words, since the plurality of second insulator layers are provided independently in the stacking direction inside the stacked body, it is possible to further reduce a change in inductance value when a current is applied, and a current direct current superposition characteristic is improved. It becomes possible to obtain stably.

As described above, the multilayer inductor according to the present invention can obtain a large inductance because a large magnetic path cross-sectional area is secured inside the coil while obtaining the action of suppressing the passage of magnetic flux by the second insulator layer. In addition, there is an advantage that the number of coil turns required to obtain the same inductance value can be reduced.
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 multilayer inductor according to the present invention will be described with reference to FIGS. FIG. 1 is an external perspective view showing a part of the internal structure of the multilayer inductor 10 of the present embodiment as seen through. 2 is a cross-sectional view taken along line AA of FIG. 1 of the multilayer inductor 10 of the first embodiment, FIG. 2A is a cross-sectional view showing the whole, and FIG. 2B is a cross-sectional view of FIG. FIG. 3 is a partial enlarged cross-sectional view showing a region B surrounded by a broken line, and FIG. 2C is a partial enlarged cross-sectional view showing a modification of the structure of a portion where the conductor layer and the second insulator layer are in contact with each other. . FIG. 3 is an exploded perspective view showing the internal structure of the multilayer inductor 10 of the first embodiment, and FIG. 4 is a diagram showing current-DC superposition characteristics of the multilayer inductor 10 of the first embodiment.

  As shown in FIGS. 1 and 2, a multilayer inductor 10 in which a spiral coil 15 is formed inside a multilayer body 11 made of a magnetic material, provided at a pair of opposing ends of the multilayer body 11. The outer electrode 14 is connected to the end 12a of the coil 15.

Specifically, a laminate 11 in which a plurality of first insulator layers 11a made of a high permeability magnetic material are laminated, and a strip-like conductor layer 12 formed for each of the first insulator layers 11a are mutually connected. At least one coil 15 that is connected and spirally formed inside the multilayer body 11, and a first magnetic layer that has a magnetic permeability lower than the magnetic permeability of the first insulator layer 11a and is in contact with the conductor layer 12. A multilayer inductor 10 having two insulator layers 13;
The conductor layer 12 and the second layer formed on the selected first insulator layer 11a of the laminate 11 at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil 15. And the outer periphery of the second insulator layer 13 reaches the end face of the laminated body 11 and crosses the magnetic path 16b outside the coil 15.

Further, the multilayer inductor 10 of the first embodiment includes a selected first insulator of the multilayer body 11 at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil 15. The conductor layer 12 and the second insulator layer so that at least part of the thickness dimension of the conductor layer 12 formed on the layer 11a overlaps at least part of the thickness dimension of the second insulator layer 13. 13 is in contact.
Specifically, as shown in FIG. 2B, the conductor layer 12 is in contact with the second insulator layer 13 in the vicinity of the outer peripheral surface of the spiral coil 15 in the plane direction dimension L1, and the conductive layer The body layer 12 contacts with the thickness direction dimension T2 corresponding to the thickness dimension of the second insulator in the thickness dimension T1. The present invention is not limited to this. For example, as shown in FIG. 2C, the conductor layer 12 ′ is in contact with the second insulator layer 13 ′ in the vicinity of the outer peripheral surface of the spiral coil 15 in the plane direction dimension L 3, and the conductor layer It may be in contact with a thickness direction dimension T3 corresponding to 12 thickness dimensions, and various other changes are possible as long as the contact is made in the surface direction and the thickness direction.

  In addition, the multilayer inductor 10 of the first embodiment includes the second insulator layer 13 only on the inner layer excluding both ends of the pivot axis of the coil of the multilayer body 11.

  The high permeability magnetic material constituting the first insulator layer 11a can be appropriately selected from those containing Ni—Zn based ferrite, Ni—Zn—Cu based ferrite and the like as main components.

  Moreover, as a material which comprises the said conductor layer, it can select and use suitably from what has Ag, an Ag-Pd alloy, etc. as a main component.

In addition, as a material constituting the second insulator layer, an insulator material that does not exhibit magnetism at room temperature, such as Cu-Zn ferrite and Zn ferrite, or an insulator made of a mixture of glass and TiO ₂ powder It can be appropriately selected from insulator materials having a material or the like as a main component and having a permeability lower than that of the first insulator layer.

The multilayer inductor 10 is formed by alternately laminating the first insulator layers 11 a and the conductor layers 12 made of the magnetic material and firing them, and the spiral coil 15 is formed inside the multilayer body 11. However, the present invention is not limited to this. In addition to the Ni—Zn ferrite and Ni—Zn—Cu ferrite, Mn—Zn ferrite, metal magnetic material powder and epoxy A first insulator layer 11a is formed by mixing a resin or the like, and an insulator material that does not exhibit magnetism at room temperature, such as the Cu-Zn ferrite or Zn ferrite, or a mixture of glass and TiO ₂ powder. In addition to the insulator material, etc., the second insulator layer 13 is constituted by mixing powders of other various fillers and epoxy resin, etc., and the powders of Ag, Ag—Pd alloy In addition to the resin as a main component, the conductor layer 12 is constituted by using metal foils such as Au and Cu, various metal thin films, etc., and these are laminated and integrated by heating and pressing to form a resin composite type laminate. It may be configured.

Next, a typical manufacturing process of the multilayer inductor 10 will be described. For convenience of explanation, the illustration and description of one multilayer inductor 10 will be made. However, the present invention is not limited to this. After a plurality of multilayer inductors 10 are collectively formed, individual multilayer inductors are formed. It may be divided.
As shown in FIG. 3, the magnetic material powder constituting the first insulator layer is mixed with polyvinyl acetate, an organic binder such as ethyl cellulose, a solvent such as terpineol, a dispersing material, etc., and a high permeability insulator material slurry. Is coated on a carrier film made of PET (PolyEthylene Terephthalate) or the like by a known means such as a doctor blade method or a gravure printing method, and dried to obtain a ceramic green sheet corresponding to the first to seventh layers on the inside S11 to S17 and a plurality of ceramic green sheets S18 constituting the upper and lower outer cover layers are prepared. The conductor material powder composing the conductor layer is mixed with a vehicle and a solvent to prepare a conductor material paste, and the insulator material powder composing the second insulator layer is mixed with an organic binder and a solvent. To prepare a low permeability insulator material paste.
Next, through holes H11 to H16 are drilled in predetermined positions of the first to sixth ceramic green sheets S11 to S16 obtained above by known means such as a punching press or laser light irradiation. .
Next, after forming the frame-shaped second insulator material layer L14 on the surface of the fourth ceramic green sheet S14 by printing the low-permeability insulator material paste in a predetermined pattern by a screen printing method. The conductive material paste is screen-printed so that the vicinity of the outer periphery of the so-called 3 / 4-turn U-shaped pattern overlaps from above in the vicinity of the inner periphery of the second insulating material layer L14 of the ceramic green sheet S14. To form a conductive material layer C14 and fill the through hole H14 of the ceramic green sheet S14 with the conductive material paste to form a through-hole conductor. At this time, in the vicinity of at least the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil, at least a part of the thickness dimension of the conductor material layer C14 is the thickness of the second insulator material layer L14. The conductor material layer C14 and the second insulator material layer L14 are in contact with each other so as to overlap at least part of the dimensions.
Further, the conductive layer is formed in a so-called 3/4 turn U-shaped pattern on the surface of the second, third, fifth and sixth layers of ceramic green sheets S12, S13, S15 and S16. The body material paste is printed by a screen printing method to form the conductor material layers C12, C13, C15, C16 and the through holes H12, H13, H15, H16 of the ceramic green sheets S12, S13, S15, S16. Are filled with the conductive material paste to form through-hole conductors.
Further, the conductive material paste is printed by a screen printing method in a pattern having a leading portion C11a at the U-shaped tip of the so-called 3/4 turn similar to the above on the surface of the first ceramic green sheet S11. A conductor material layer C11 is formed, and the conductor material paste is filled into the through hole H11 of the ceramic green sheet S11 to form a through hole conductor.
Further, the conductive material paste is printed by a screen printing method in a pattern having a so-called 3/4 turn U-shaped leading end C17a on the surface of the seventh ceramic green sheet S17, A conductor material layer C17 is formed.
Next, the ceramic green sheets S11 to S17 obtained as described above are the outermost layers of the ceramic green sheets S11 to S17 so that the conductor material layers C11 to C17 and the through-hole conductors are connected to each other to form a spiral coil 15. The ceramic green sheet S18 on which the low-permeability insulator material paste, the conductor material paste, etc. are not printed as the cover layer and the upper layer, the ceramic green sheet C17 are stacked so as to be the lowermost layer. A plurality of sheets S11 to S17 are laminated on the upper and lower parts of the laminate and bonded together, followed by binder removal treatment at 400 to 600 ° C. for 1 to 3 hours, and then firing and lamination at 800 to 1000 ° C. for 1 to 10 hours A body 11 is obtained.
Next, a baking-type conductor material paste having a conductive material powder such as an Ag, Ag-Pd alloy or the like as a main component on the end face where the lead portion 12a of the conductor layer 12 of the obtained laminate 11 is exposed is the same as described above. Alternatively, a thermosetting conductive resin paste containing conductive material powder such as Ag or Ag-Pd alloy is applied by a known application means such as a screen printing method, a dip method, or a transfer method, and baked at a predetermined temperature. Alternatively, the external electrode 14 is formed by thermosetting at a predetermined temperature.
Further, if necessary, Cu plating, Ni plating, Sn plating, or the like is formed on the external electrode 14 for the purpose of solderability.

Example 1
Next, examples of the multilayer inductor 10 according to the first embodiment will be described with reference to FIGS. First, a manufacturing process of the multilayer inductor 10 of this embodiment will be described with reference to FIG.

For forming the first insulator layers 11a, main component _FeO 2, CuO, ZnO, ethyl cellulose as a binder in the Ni-Zn-Cu-based ferrite powder after calcination milling consisting NiO, terpineol as a solvent, a dispersing agent, etc. And kneaded to prepare a high permeability magnetic material slurry, which was coated on a PET film by a doctor blade method and dried to prepare ceramic green sheets S11 to S18. In order to form the conductor layer 12, Ag powder, a vehicle, and a solvent are mixed to prepare a conductor material paste, and in order to form the second insulator layer, FeO ₂ , CuO, and ZnO are mainly used. An organic binder, a solvent, and the like were mixed with the ferrite powder as a material to prepare a low-permeability insulator material paste.
Next, through holes H11 to H16 are punched in predetermined positions of the ceramic green sheets S11 to S16 obtained above by a punching press, and the low magnetic permeability insulator is formed on the surface of the obtained ceramic green sheet S14. The material paste was printed in a predetermined pattern by a screen printing method to form the second insulator material layer L14.
Next, the conductor is formed so that the vicinity of the outer periphery of the so-called 3 / 4-turn U-shaped pattern overlaps with the vicinity of the inner periphery of the second insulator material layer L14 of the ceramic green sheet S14 obtained above. The material paste was printed by a screen printing method to form a conductor material layer C14, and the conductor material paste was filled into the through hole H14 of the ceramic green sheet S14 to form a through-hole conductor.
At this time, at least a part of the thickness of the conductor material layer C14 is at least part of the thickness of the second insulator material layer L14 in the vicinity of at least the outer periphery between the inner periphery and the outer periphery of the spiral coil 15. The conductor material layer C14 and the second insulator material layer L14 are arranged so as to be in contact with each other so as to overlap at least a part of the thickness dimension.
Further, the conductive layer is formed in a so-called 3/4 turn U-shaped pattern on the surface of the second, third, fifth and sixth layers of ceramic green sheets S12, S13, S15 and S16. The body material paste is printed by a screen printing method to form the conductor material layers C12, C13, C15, C16 and the through holes H12, H13, H15, H16 of the ceramic green sheets S12, S13, S15, S16. A through-hole conductor was formed by filling the conductor material paste.
Further, the conductive material paste is printed by a screen printing method in a pattern having a leading portion C11a at the U-shaped tip of the so-called 3/4 turn similar to the above on the surface of the first ceramic green sheet S11. A conductor material layer C11 was formed, and the conductor material paste was filled in the through hole H11 of the ceramic green sheet S11 to form a through hole conductor.
Further, the conductive material paste is printed by a screen printing method in a pattern having a so-called 3/4 turn U-shaped leading end C17a on the surface of the seventh ceramic green sheet S17, A conductor material layer C17 was formed.
Next, the ceramic green sheets S11 to S17 obtained as described above are the outermost layers of the ceramic green sheets S11 to S17 so that the conductor material layers C11 to C17 and the through-hole conductors are connected to each other to form a spiral coil 15. The ceramic green sheet S18 obtained by stacking the ceramic green sheet C18 on which the low-permeability insulator material paste, the conductor material paste, etc. are not printed as the cover layer is stacked so that the upper layer, the ceramic green sheet C17 is the lowermost layer. A plurality of sheets were stacked on the upper and lower portions of the laminate of sheets S11 to S17, pressed, and then subjected to binder removal treatment at 500 ° C. for 1 hour, and then fired at 900 ° C. for 2 hours to obtain a laminate 11.
Next, a baking-type conductor material paste mainly composed of Ag powder is applied to the end face where the lead portion 12a of the conductor layer 12 of the obtained laminate 11 is exposed by the dipping method in the same manner as described above. The external electrode 14 was formed by baking for 1 hour.
Further, although not shown, Ni plating and Sn plating were sequentially formed on the external electrode 14 to complete the multilayer inductor 10.

  The multilayer inductor 10 according to the first embodiment thus obtained includes a multilayer body 11 in which a plurality of first insulator layers 11a made of a high magnetic permeability magnetic body mainly composed of Ni—Zn—Cu ferrite are stacked. At least a 3/4 turn strip-shaped conductor layer 12 mainly composed of Ag formed for each of the first insulator layers 11a is connected to each other to be spirally formed inside the stacked body 11. A multilayer inductor 10 having one coil 15 and a second insulator layer 13 having a magnetic permeability lower than that of the first insulator layer 11a and in contact with the conductor layer 12, The conductor layer 12 and the second layer formed on the selected first insulator layer 11a of the laminate 11 at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil 15. In contact with the insulator layer 13 and 2 of the outer circumference of the insulator layer 13 is disposed so as to cross the outer magnetic path 16b of the coil 15 reaches the end surface of the laminate 11.

(Comparative example)
A multilayer inductor according to Background Art 2 was produced in the same manner as in the first embodiment except for the arrangement of the second insulator layer 13.
FIG. 4 shows the results obtained by measuring the current-DC superposition characteristics of the multilayer inductor 10 of the first embodiment and the multilayer inductor of the comparative example (background art 2). The horizontal axis represents a superimposed DC current value (unit: mA) of 0 to 1000 mA, and the vertical axis represents an inductance value (unit: μH) of 0 to 5 μH. The broken line shows the measurement result of the multilayer inductor according to the background art 2. The initial inductance value is about 3 μH, and the inductance value is larger than the initial inductance value as the superimposed DC current increases in the range of 100 mA from the initial stage. The decrease is about 1 μH and a rapid decrease is observed.
On the other hand, the solid line is the measurement result of the multilayer inductor 10 of the first embodiment, and the initial inductance value is 4.5 μH, which is 1.5 times higher than the background art 2, and the multilayer inductor of the background art 2 of the comparative example. It can be seen that a high inductance value can be obtained from the initial stage until the load current reaches 1000 mA. In addition, with the increase of the superimposed DC current in the range of 100 mA from the initial stage, the decrease in the inductance value is about 1 μH compared to the initial inductance value, which is almost the same as that of the background art 2, and the relative inductance value It can be seen that the degree of decrease is reduced.

  As described above, the multilayer inductor 10 according to the first embodiment of the present invention secures a large magnetic path cross-sectional area inside the coil 15 while obtaining the action of suppressing the passage of magnetic flux by the second insulator layer 13. Therefore, there is an advantage that a large inductance can be obtained and the number of coil turns necessary to obtain the same inductance value is reduced, which is particularly suitable for a multilayer inductor with a low load current specification.

  In the multilayer inductor 10 of the first embodiment, the state in which the conductor layer 12 and the second insulator layer 13 are in contact with each other can be reliably obtained even if the second insulator layer 13 is thinned. Variations in the action of suppressing the passage of magnetic flux by the two insulator layers 13 can be prevented, and as a result, a higher inductance value can be obtained.

  In the multilayer inductor 10 according to the first embodiment, the second insulator layer 13 is disposed in a portion where the magnetic flux density tends to be high on the outer peripheral side of the coil 15 inside the multilayer body 11. 11 can suppress the concentration of the magnetic flux density inside 11, and prevent the occurrence of local magnetic saturation.

Next, a second embodiment of the multilayer inductor of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the internal structure of the multilayer inductor 20 of the second embodiment.
As shown in FIG. 5, a multilayer inductor 20 in which a spiral coil 25 is formed inside a multilayer body 21 made of a magnetic material, and external electrodes respectively provided at a pair of opposed end portions of the multilayer body 21. 24, the end of the coil 25 is connected.

In particular,
A laminated body 21 in which a plurality of first insulator layers 21a made of a high permeability magnetic body are laminated and a strip-like conductor layer 22 formed for each of the first insulator layers 21a are connected to each other to form the laminated body. At least one coil 25 spirally formed inside the body 21;
A multilayer inductor 20 having a second insulator layer 23 having a permeability lower than that of the first insulator layer 21a and in contact with the conductor layer 22;
The conductor layer 22 formed on the selected first insulator layer 21a of the multilayer body 21 and the second layer at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil. While being in contact with the insulator layer 23, the outer periphery of the second insulator layer 23 reaches the end face of the laminate 21 and is disposed so as to cross the magnetic path 26 b outside the coil 25.

  The multilayer inductor 20 according to the second embodiment includes a selected first insulator of the multilayer body 21 at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil 25. The conductor layer 22 and the second insulator layer so that at least a part of the thickness dimension of the conductor layer 22 formed on the layer 21 a overlaps at least a part of the thickness dimension of the second insulator layer 23. 23 is in contact.

  The multilayer inductor 20 of the second embodiment includes the second insulator layer 23 only on the inner layer of the multilayer body 21 excluding both ends of the turning shaft of the coil 25.

  The multilayer inductor 20 of the second embodiment includes a plurality of the second insulator layers 23 inside the multilayer body 21 independently of each other in the stacking direction.

The difference between the second embodiment and the first embodiment is that the center between the inner layers excluding both ends of the pivot axis of the coil 15 of the laminate 11 in the first embodiment. The second insulator layer 13 is provided corresponding to one conductor layer 12 close to the two, whereas in the second embodiment, both ends of the turning shaft of the coil 25 of the laminate 21 are connected to each other. Three second insulator layers 23 are provided corresponding to the three conductor layers 22 close to the center between the removed inner layers.
As a result, it is possible to reduce the change in characteristics when a current is applied, and the effect of further improving the stability of the current direct current superposition characteristics is obtained.

In the first and second embodiments, the manufacturing method of the multilayer inductor by the green sheet method has been described. However, the present invention is not limited to this, and for example, the manufacturing method of the multilayer inductor by the slurry build method is used. be able to.
Further, in the first and second embodiments, the multilayer inductor using the multilayer body made of the ceramic magnetic body integrated by firing is exemplified, but the present invention is not limited to this, and as described above. In addition, the present invention can be applied to a multilayer inductor using a resin composite type multilayer body. Moreover, these multilayer inductors can be applied to various known electronic devices.

  The present invention is suitable for a multilayer inductor that has a good current direct current superposition characteristic and can acquire a high inductance value.

It is the perspective view which saw through the partial internal structure which shows the external appearance of 1st Embodiment of the multilayer inductor of this invention. It is sectional drawing in the AA of FIG. 1 which shows the internal structure of the said 1st Embodiment. It is a disassembled perspective view for demonstrating the internal structure of the said 1st Embodiment. It is a figure which shows the measurement result of the current direct current | flow superimposition characteristic of the multilayer inductor of the said 1st Embodiment. It is sectional drawing which shows the internal structure of 2nd Embodiment of the multilayer inductor of this invention. It is sectional drawing which shows an example of background art. It is sectional drawing which shows the other example of background art.

Explanation of symbols

10: multilayer inductor 11: multilayer body 11a: first insulator layer 12: conductor layer 12a: lead portion 13: second insulator layer 14: external electrode 15: coil 16a: inner magnetic path 16b: outer magnetic path 20: multilayer inductor 21: multilayer body 21a: first insulator layer 22: conductor layer 22a: lead 23: second insulator layer 24: external electrode 25: coil 26a: inner magnetic path 26b: outer magnetic path

Claims (4)

A laminate in which a plurality of first insulator layers made of a high permeability magnetic material are laminated and a strip-like conductor layer formed for each of the first insulator layers are connected to each other inside the laminate. In a multilayer inductor having at least one coil formed in a spiral shape and a second insulator layer having a permeability lower than that of the first insulator layer and in contact with the conductor layer,
The conductor layer and the second insulator layer formed on the selected first insulator layer of the laminate at least in the vicinity of the outer circumference surface between the inner circumference surface and the outer circumference surface of the spiral coil. And the outer periphery of the second insulator layer reaches the end face of the multilayer body and is disposed so as to cross the magnetic path outside the coil.   At least part of the thickness dimension of the conductor layer formed on the selected first insulator layer of the laminate is at least in the vicinity of the outer peripheral surface between the inner peripheral surface and the outer peripheral surface of the spiral coil. 2. The multilayer inductor according to claim 1, wherein the conductor layer and the second insulator layer are in contact with each other so as to overlap at least part of the thickness dimension of the second insulator layer.   2. The multilayer inductor according to claim 1, wherein the second insulator layer is provided only on an inner layer excluding both ends of a pivot axis of the coil of the multilayer body.   The multilayer inductor according to claim 1, further comprising a plurality of the second insulator layers that are independent of each other in the stacking direction inside the multilayer body.

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