Abstract
A multilayer inductor providing improved DC superposition characteristics by a permanent magnet that emits a bias magnetic flux, and having a low-loss material as a magnetic body to improve converter conversion efficiency. The multilayer inductor has a plurality of laminated electrically insulating magnetic layers; and laminated conductive patterns, each of the conductive patterns being connected in sequence in the lamination direction forming a spiral coil inside the magnetic layer. An magnetized annular permanent magnet layer emits a magnetic flux whose direction is opposite that of a magnetic flux excited by the coil is between an outer peripheral edge of the inductor and an outer peripheral edge of the coil so as not to overlap an inner peripheral part of the magnet layer with the conductive patterns and so as to block a space between the conductive patterns and the magnet layer, in axial view of the coil.
Claims
1. A multilayer inductor comprising: a plurality of electrically insulating magnetic layers that are laminated; and conductive patterns that are laminated, each of the conductive patterns being connected in sequence in the lamination direction to form a spirally circulating coil inside the magnetic layers, both ends of the coil being drawn out to an outer peripheral part, wherein an annular permanent magnet layer magnetized so as to emit a magnetic flux whose direction is opposite to a direction of a magnetic flux excited by the coil is disposed between an outer peripheral edge of the multilayer inductor and an outer peripheral edge of the coil so as not to overlap an inner peripheral part of the annular permanent magnet layer with the conductive patterns and so as to block a space between the conductive patterns and the annular permanent magnet layer, in axial view of the coil.
2. A multilayer inductor comprising: a plurality of electrically insulating magnetic layers that are laminated; and conductive patterns that are laminated, each of the conductive patterns being connected in sequence in the lamination direction to form a spirally circulating coil inside the magnetic layers, both ends of the coil being drawn out to an outer peripheral part, wherein an annular permanent magnet layer magnetized so as to emit a magnetic flux whose direction is opposite to a direction of a magnetic flux excited by the coil is disposed over a whole surface of inside of the coil so as not to overlap an outer peripheral part of the annular permanent magnet layer with the conductive patterns and so as to block a space between the conductive patterns and the annular permanent magnet layer, in axial view of the coil.
3. The multilayer inductor according to claim 1, wherein in the axial view, a clearance is formed between the permanent magnet layer and the conductive patterns, and the clearance is blocked by an annular electrically insulating nonmagnetic pattern interposed between the permanent magnet layer and the conductive patterns.
4. The multilayer inductor according to claim 1, wherein the magnetic layers and the permanent magnet layer, or the magnetic layers, the permanent magnet layer, and an annular electrically insulating nonmagnetic pattern, are each formed of a material which is capable of being collectively burned at a temperature of 940 C. or less.
5. The multilayer inductor according to claim 4, wherein a NiZn ferrite based material is used as the magnetic layers, a Zn ferrite based material is used as the nonmagnetic pattern, and a low-temperature sintered magnet material obtained by adding Bi.sub.2O.sub.3 and SiO.sub.2 to Ba ferrite powder or Sr ferrite powder is used as the permanent magnet layer.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) FIG. 1 is a whole perspective view illustrating a first embodiment of a multilayer inductor of the present invention.
(2) FIG. 2 is an exploded perspective view illustrating a laminated body for manufacturing the multilayer inductor of FIG. 1.
(3) FIG. 3 illustrates the multilayer inductor of FIG. 1, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(4) FIG. 4 is a longitudinal sectional view of a principal part illustrating a first modification of the first embodiment.
(5) FIG. 5 is a longitudinal sectional view illustrating a second modification.
(6) FIG. 6 illustrates a third modification, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(7) FIG. 7 illustrates a second embodiment of a multilayer inductor of the present invention, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(8) FIG. 8 illustrates a first modification of the second embodiment, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(9) FIG. 9 illustrates a second modification of the second embodiment, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(10) FIG. 10 illustrates a third modification of the second embodiment, in which (a) is a plane sectional view, and (b) is a longitudinal sectional view.
(11) FIG. 11 is a diagram illustrating the result of an example, in which the DC superposition characteristics of the multilayer inductors shown in the first embodiment are compared with the DC superposition characteristics of a multilayer inductor of a comparative example.
(12) FIG. 12 is a diagram illustrating the result of an example, in which the DC superposition characteristics of the multilayer inductors shown in the second embodiment are compared with the DC superposition characteristics of a multilayer inductor of a comparative example.
(13) FIG. 13 is a diagram illustrating the result of an example, in which the DC superposition characteristics of the multilayer inductor shown in the first embodiment are compared with the DC superposition characteristics of a multilayer inductor of a comparative example, which is obtained by overlapping a permanent magnet and an internal conductor.
(14) FIG. 14 is a diagram illustrating the result of an example, in which the DC superposition characteristics of the multilayer inductor shown in the second embodiment are compared with the DC superposition characteristics of a multilayer inductor of a comparative example, which is obtained by overlapping a permanent magnet and an internal conductor.
(15) FIG. 15 is a longitudinal sectional view illustrating a conventional multilayer inductor including a magnet.
DESCRIPTION OF EMBODIMENTS
First Embodiment
(16) FIG. 1 to FIG. 3 each illustrate a first embodiment of a multilayer inductor according to the present invention, and FIG. 4 to FIG. 6 illustrate first to third modifications, respectively.
(17) As illustrated in FIG. 1 to FIG. 3, this multilayer inductor is formed in a rectangular parallelepiped shape, in which a plurality of electrically insulating magnetic layers 1 and conductive patterns 2 are laminated, and each of the conductive patterns 2 is connected in sequence in a lamination direction, so that a spirally circulating coil 2 is formed inside a magnetic body configured by the magnetic layers 1, and both ends of the coil 2 are drawn out to be connected to external electrodes 3. The external electrodes 3 are connected to a land part of a circuit board (not shown), so that the multilayer inductor is surface-mounted.
(18) Herein, between the conductive patterns 2 adjacent in the lamination direction, an electrically insulating nonmagnetic pattern 4 having a shape corresponding to the shape of each of the conductive patterns 2 are disposed. Furthermore, at an intermediate position in the lamination direction, an electrically insulating nonmagnetic layer 5 that becomes a magnetic gap is disposed over a whole surface by one layer in place of the nonmagnetic pattern 4.
(19) In the multilayer inductor according to this embodiment and multilayer inductors according to first to third modifications, in the axial view of each coil 2, each of magnetized permanent magnet layers 6 is disposed over the whole surface between the outer peripheral edge of this multilayer inductor (namely outer peripheral edge of each magnetic layer 1) and the outer peripheral edge of the coil 2 so as to emit a magnetic flux whose direction is opposite to the direction of a magnetic flux excited by the above coil 2.
(20) That is, in the multilayer inductor of this embodiment, as illustrated in FIG. 3, the annular permanent magnet layers 6 are disposed adjacent to the upper and lower conductive patterns 2 located at the both ends of the lamination direction. Additionally, the permanent magnet layers 6 are formed such that the inner dimension is the same as the outer dimension of the conductive patterns 2 so as not to overlap the permanent magnet layers 6 with the coil 2 in the above axial view.
(21) In order to manufacture the multilayer inductor 1 having the above configuration, as illustrated in FIG. 2, FIG. 3A, and FIG. 3B, NiZn based ferrite material paste of an electrically insulating material is first printed by a screen printing method or the like, so that a magnetic layer 1 is formed.
(22) Then, low-temperature sintered magnet material paste obtained by adding Bi.sub.2O.sub.3 and SiO.sub.2 to Ba ferrite powder or Sr ferrite powder is printed on this magnetic layers 1, so that a permanent magnet layers 6 is formed, and a magnetic layer 1 is printed at a part except this permanent magnet layer 6. FIG. 2 illustrates a case where four multilayer inductors are manufactured on one plane at the same time.
(23) Then, a conductive pattern 2 is printed on a layer formed with this permanent magnet layers 6. Similarly, after a magnetic layer 1 is printed at a part except the conductive pattern 2, an electrically insulating Zn ferrite material is printed on the conductive pattern 2 so as to have a shape corresponding to the shape of the conductive pattern 2, so that a nonmagnetic pattern 4 is formed, and a magnetic layer 2 is formed at a part except the nonmagnetic pattern 4.
(24) Thus, as illustrated in FIG. 3 (b), conductive patterns 2 and nonmagnetic pattern 4 are alternately laminated in magnetic layers 1, so that permanent magnet layers 6 are disposed on the both ends in the lamination direction. Additionally, at the intermediate position in the lamination direction, electrically insulating Zn ferrite material paste which is the same as the nonmagnetic pattern 4 is printed over the whole surface, so that a nonmagnetic layer 5 is formed. With this, upper and lower conductive body patterns 2 are electrically connected by utilizing a via hole or the like.
(25) Next, the obtained laminated body is collectively burned at a temperature of 940 C. or less, more specifically, at about 900 C. to be integrated, and thereafter the permanent magnet layers 6 are magnetized so as to emit a magnetic flux whose direction is opposite to the direction of the magnetic flux excited by the coil 2, so that it is possible to manufacture the multilayer inductor illustrated in FIG. 1. In a case illustrated in FIG. 2, four laminated bodies, each of which configures a multilayer inductor, are cut one by one, and thereafter each laminated body is sintered.
(26) Additionally, FIG. 4 illustrates the first modification of this embodiment, and this multilayer inductor is different from the multilayer inductor illustrated in FIG. 1 to FIG. 3, in that a nonmagnetic pattern 7 made of a Zn ferrite material which is similar to each nonmagnetic pattern 4 formed between the conductive patterns 2 is formed between each permanent magnet layer 6 and each conductive pattern 2 in the lamination direction. As illustrated in FIG. 4, in a case where the inner dimension of the permanent magnet layer 6 is the same as the outer dimension of the conductive patterns 2, or in a case where a clearance is formed between the permanent magnet layer 6 and the conductive patterns 2 in the above axial view, the nonmagnetic pattern 7 is formed to have such dimension that the clearance is blocked.
(27) Furthermore, FIG. 5 illustrates the second modification of this embodiment. In this multilayer inductor, each of magnetic layers 8 having magnetic permeability of or less of the magnetic permeability of the magnetic body is disposed over the whole surface between the conductive patterns 2 in place of the nonmagnetic patterns 4 disposed between the conductive patterns 2 and used as insulating layers in the first embodiment.
(28) FIG. 6 illustrates a third modification of this embodiment.
(29) In this multilayer inductor, a permanent magnet layer 6 is disposed over two layers of the whole surfaces of the outer peripheral edge of the multilayer inductor (namely, outer peripheral edge of each magnetic layer 1) and the outer peripheral edge of the coil 2. Herein, the permanent magnet layer 6 is disposed at a layer formed with the nonmagnetic pattern 4, and at a layer formed with the conductive pattern 2 located under, and adjacent to, the nonmagnetic pattern 4.
(30) Then, the permanent magnet layer 6 is formed such that the inner peripheral edge of the permanent magnet layer 6 is in contact with the outer peripheral edge of the nonmagnetic pattern 4 at the layer formed with the nonmagnetic pattern 4, and the inner peripheral edge of the permanent magnet layer 6 is in contact with the outer peripheral edge of the conductive pattern 2 at the layer formed with the conductive pattern 2.
Second Embodiment
(31) FIG. 7 illustrates a second embodiment of a multilayer inductor according to the present invention, and FIG. 8 to FIG. 10 illustrate first to third modifications of the second embodiment, respectively. Hereinafter, the same components as the components illustrated in FIG. 1 to FIG. 6 are denoted by the same reference numerals, and the description thereof is simplified.
(32) In each of these multilayer inductors, in axial view of a coil 2, a permanent magnet layer 6 magnetized so as to emit a magnetic flux whose direction is opposite to the direction of a magnetic flux excited by the coil 2 is disposed over the whole surface of the inside of the coil 2.
(33) That is, in the multilayer inductor of the second embodiment, as illustrated in FIG. 7, an annular nonmagnetic pattern 7 made of a Zn ferrite material similar to the nonmagnetic pattern 4 formed between the conductive patterns 2 is formed at a layer above a conductive pattern 2 located at an uppermost layer in the figure in a lamination direction so as to extend to the inside of the coil 2, and a quadrangular permanent magnet layer 6 is disposed at an upper layer of this nonmagnetic pattern 7. Herein, the permanent magnet layer 6 is formed such that the outer dimension of the permanent magnet layer 6 is the same as the inner dimension of the conductive pattern 2 so as not to overlap the permanent magnet layer 6 with the coil 2 in the above axial view.
(34) FIG. 8 illustrates the first modification of the multilayer inductor having the above configuration. In this multilayer inductor, a similar annular nonmagnetic pattern 7 is further formed at a layer on the lower side of a conductive pattern 2 located at a lowermost layer in the figure of the drawing in the lamination direction so as to extend to the inside of the coil 2, and a quadrangular permanent magnet layer 6 is further disposed at a lower layer of this nonmagnetic pattern 7, in addition to the above permanent magnet layer 6. This permanent magnet layer 6 is also formed such that the outer dimension of the permanent magnet layer 6 is the same as the inner dimension of the conductive pattern 2 so as not to overlap the permanent magnet layer 6 with the coil 2 in the above axial view.
(35) Next, FIG. 9 illustrates the second modification. In this multilayer inductor, a quadrangular permanent magnet layer 6 is disposed inside a conductive pattern 2 located at an uppermost layer in the figure of the drawing in the lamination direction. This permanent magnet layer 6 is formed at the same layer as the above conductive pattern 2, and is formed such that the outer dimension of the permanent magnet layer 6 is the same as the inner dimension of the conductive pattern 2 so as not to overlap the permanent magnet layer 6 with the coil 2 in the above axial view, and so as not to form a clearance.
(36) Additionally, in the multilayer inductor according to the third modification illustrated in FIG. 10, the outer dimension of the permanent magnet layer 6 illustrated in FIG. 9 is formed in a quadrangle whose size is smaller than the inner dimension of the conductive pattern 2, and, an annular nonmagnetic pattern 7 which blocks a space between the conductive pattern 2 and the permanent magnet layer 6 is formed between the conductive pattern 2 and the permanent magnet layer 6 in the axial view of the coil 2.
(37) According to the multilayer inductors shown and described in the first and second embodiments and the modifications of these, the permanent magnet layer 6 is disposed so as to block the outside of the coil 2 or the inside of the coil 2, in axial view, and therefore a leakage magnetic flux Z which does not work as a bias magnetic flux Y and has an opposite direction, like a permanent magnet illustrated in FIG. 15, is not generated. As a result, the permanent magnet layer 6 can significantly improve DC superposition characteristics. In other words, a low-loss material relatively easily saturated can be used as the magnetic body (magnetic layer) 1, and it is possible to achieve the improvement of converter conversion efficiency.
(38) Furthermore, a NiZn ferrite based material is used as the magnetic layers 1, a Zn ferrite based material is used as each of the nonmagnetic patterns 4 and 7, and a low-temperature sintered magnet material obtained by adding Bi.sub.2O.sub.3 and SiO.sub.2 to Ba ferrite powder or Sr ferrite powder is used as the permanent magnet layer 6, and therefore collective burning is performed at a temperature of about 900 C. at the timing of manufacturing, and thereafter the permanent magnet layer 6 is magnetized, so that it is possible to easily manufacture the multilayer inductor.
Example
(39) In order to verify the effects of the multilayer inductors according to the present invention, the DC superposition characteristics of the multilayer inductors of the present invention, and the DC superposition characteristics of multilayer inductors of comparative examples were obtained to be compared by simulation.
(40) In both the multilayer inductors of the present invention and the multilayer inductors of the comparative examples, chip size was 2.52.01.0 mm, the number of turns of the internal conductor was 5 turns, a film thickness of the internal conductor was 120 m, and the thickness of an insulating layer between the internal conductors was 15 m.
(41) First, FIG. 11 illustrates a case where the DC superposition characteristics of multilayer inductors (1) and (2) having the configurations shown in the first embodiment and the first modification are compared with the DC superposition characteristics of a multilayer inductor (3) of a comparative example formed with a clearance of 50 m between a permanent magnet layer and an internal conductor. As is clear from FIG. 11, the DC superposition characteristics of the multilayer inductor (1), in which the permanent magnet layer and the internal conductor are disposed so as to be in contact with each other in axial view, is more excellent than the DC superposition characteristics of the multilayer inductor (3) of the above comparative example.
(42) Additionally, also in a case where a clearance is formed between the permanent magnet layer and the internal conductor, the multilayer inductor (2) which blocks the clearance by the nonmagnetic pattern can obtain DC superposition characteristics equivalent to the DC superposition characteristics of the above multilayer inductor (1).
(43) FIG. 12 illustrates a case where the DC superposition characteristics of multilayer inductors (4) and (5) having the configurations shown in the second modification and the third modification of the second embodiment are compared with the DC superposition characteristics of a multilayer inductor (6) of a comparative example formed with a clearance of 50 m between an internal conductor and a permanent magnet layer disposed inside the internal conductor. Also in the result of the simulation of the DC superposition characteristics illustrated in FIG. 12, the DC superposition characteristics of the multilayer inductors (4) and (5) according to the present invention are more excellent than the DC superposition characteristics of the multilayer inductor (6) of the comparative example.
(44) FIG. 13 illustrates a case where the DC superposition characteristics of the above multilayer inductor (1) was compared with the DC superposition characteristics of a multilayer inductor (7) of a comparative example, in which a permanent magnet layer and an internal conductor are overlapped with each other by 150 m in the axial view of a coil. From this figure of the drawing, it is found that the DC superposition characteristics of the multilayer inductor (7) of the comparative example, in which the permanent magnet layer and the internal conductor are overlapped with each other, remarkably deteriorates compared to the DC superposition characteristics of the multilayer inductor (1) according to the present invention.
(45) FIG. 14 illustrates a case where the DC superposition characteristics of the above multilayer inductor (4) was compared with the DC superposition characteristics of a multilayer inductor (8) of a comparative example, in which a permanent magnet layer disposed in an internal conductor, and the internal conductor are overlapped with each other by 150 m in the axial view of a coil. From this figure, it is found that an initial value of the multilayer inductor (8) of the comparative example, in which the permanent magnet layer and the internal conductor are overlapped with each other, particularly largely lowers compared to an initial value of the multilayer inductor (4) according to the present invention. Accordingly, it is found that a structure in which the permanent magnet layer overlaps with the internal conductor in the above axial view is not preferable similarly to the result illustrated in FIG. 13.
INDUSTRIAL APPLICABILITY
(46) It is possible to provide a multilayer inductor, in which it is possible to significantly improve DC superposition characteristics by a permanent magnet which emits a bias magnetic flux, and in which it is possible to use a low-loss material as a magnetic body so as to also achieve the improvement of converter conversion efficiency.
REFERENCE SIGNS LIST
(47) 1 Magnetic layer
(48) 2 Conductive pattern (coil)
(49) 3 External electrode
(50) 4, 5, 7, 8 Nonmagnetic pattern
(51) 6 Permanent magnet layer
