Transformer component

Abstract

To provide a transformer component with reduced loss.SOLUTION: In a transformer component 10, an inner diameter area S1 of a primary coil L1 is designed to be relatively large so that it is larger than an inner diameter area S2 of a secondary coil L2. As a result, flux saturation is less likely to occur in an inner diameter region of the primary coil L1, thereby providing the transformer component with lower loss. Meanwhile, the inner diameter area S2 of the secondary coil L2 is designed to be relatively small so that a line width of spiral conductors 17A and 17B constituting the secondary coil L2 may be sufficiently ensured, thereby enabling lower resistance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a transformer component. [Background technology]

[0002] The following Cited Document 1 discloses a transformer component having a primary coil and a secondary coil provided within an element body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-89760 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors conducted extensive research into losses in transformer components and discovered a new technique that can reduce losses by reducing magnetic flux saturation.

[0005] An object of one aspect of the present disclosure is to provide a transformer component with reduced loss. [Means for solving the problem]

[0006] A transformer component according to one aspect of the present disclosure comprises a base body, a primary coil provided within the base body and wound around a coil axis along a first direction, and a secondary coil formed on a substrate within the base body perpendicular to the first direction, overlapping with the primary coil in the first direction and wound around the coil axis to have a common magnetic path with the primary coil, wherein the number of turns of the primary coil is greater than the number of turns of the secondary coil, and the inner diameter area of ​​the primary coil is greater than the inner diameter area of ​​the secondary coil.

[0007] In the above transformer component, the primary coil, which has more turns than the secondary coil, has a larger inner diameter area than the secondary coil, which reduces magnetic flux saturation and, as a result, reduces losses. Effect of the Invention

[0008] According to the present disclosure, a transformer component with reduced losses is provided. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic exploded perspective view showing a transformer component according to one embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the transformer component shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various embodiments and examples will be described below with reference to the drawings. Note that the same or corresponding parts in each drawing are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0011] 1 and 2, a transformer component 10 according to an embodiment includes a primary coil L1 and a secondary coil L2 in an element body 11. More specifically, the transformer component 10 includes a ferrite substrate 12, a thin-film coil layer 14 including first and second spiral conductors 13A and 13B formed on the ferrite substrate 12, a printed circuit board 16 provided on the ferrite substrate 12 in a superimposed manner, third and fourth spiral conductors 17A and 17B formed on both sides of the printed circuit board 16, and four terminal electrodes 20a to 20d. In this embodiment, the primary coil L1 includes the ferrite substrate 12 and the thin-film coil layer 14, and the secondary coil L2 includes the printed circuit board 16 and the third and fourth spiral conductors 17A and 17B.

[0012] The element body 11 has a rectangular plate-like outer shape and has a pair of principal surfaces 11a, 11b opposing each other in a first direction D1 and four side surfaces 11c-11f connecting the principal surfaces. The ferrite substrate 12, the thin-film coil layer 14, the printed circuit board 16, and the third and fourth spiral conductors 17A, 17B are embedded in the element body 11. The terminal electrodes 20a-20d are provided on the side surfaces 11c-11f of the element body 11. In this embodiment, of the side surfaces 11c and 11d opposing each other, a pair of terminal electrodes 20a, 20b is provided on the side surface 11c, and a pair of terminal electrodes 20c, 20d is provided on the side surface 11d.

[0013] The element 11 is made of a magnetic material, and in this embodiment, is made of a resin containing metal magnetic powder. When a resin containing metal magnetic powder is used, many small gaps exist between the metal magnetic powder and the resin, which increases the saturation magnetic flux density, so that it is possible to omit gaps between each element arranged in the element 11. The resin containing metal magnetic powder is a magnetic material in which metal magnetic powder is mixed into resin. It is preferable to use a permalloy material as the metal magnetic powder. Specifically, it is preferable to use a metal magnetic powder containing a Pb-Ni-Co alloy having an average particle size of 20 to 50 μm as the first metal magnetic powder and carbonyl iron having an average particle size of 3 to 10 μm as the second metal magnetic powder in a predetermined ratio, for example, 70:30 to 80:20, preferably 75:25 by weight. The content of the metal magnetic powder is preferably 90 to 96% by weight.

[0014] If the amount of the metal magnetic powder is reduced relative to the resin, the saturation magnetic flux density becomes smaller, and conversely, if the amount of the metal magnetic powder is increased, the saturation magnetic flux density becomes larger, so the saturation magnetic flux density can be adjusted only by the amount of the metal magnetic powder. Furthermore, it is particularly preferable that the metal magnetic powder is a mixture of a first metal magnetic powder having an average particle size of 5 μm and a second metal magnetic powder having an average particle size of 50 μm, mixed at a predetermined ratio, for example, 75:25. In this way, when two types of metal magnetic powders with different particle sizes are used, a high-density magnetic core can be molded under low pressure or non-pressure molding, and a magnetic core with high magnetic permeability and low loss can be realized. The resin contained in the metal magnetic powder-containing resin functions as an insulating binder. It is preferable to use a liquid epoxy resin or a powder epoxy resin as the resin material. Also, the resin content is preferably 4 to 10% by weight.

[0015] The ferrite substrate 12 is a rectangular flat plate extending perpendicular to the first direction D1, and constitutes a part of a closed magnetic circuit. Although not particularly limited, the planar dimensions of the ferrite substrate 12 may be, for example, about 3.2×2.5 mm. The material of the ferrite substrate 12 is preferably sintered ferrite, and in particular, it is preferable to use a material with high magnetic permeability such as Ni-Cu-Zn ferrite or Mn-Zn ferrite. By using such a magnetic material, the magnetic characteristics of the transformer can be improved.

[0016] The thin-film coil layer 14 is formed on one main surface 12a (upper surface) of the ferrite substrate 12. The thin-film coil layer 14 is formed by laminating a first insulating layer 15a, a first spiral conductor 13A, a second insulating layer 15b, a second spiral conductor 13B, and a third insulating layer 15c in this order.

[0017] The first spiral conductor 13A is formed on the surface of a first insulating layer 15a formed on the ferrite substrate 12. This is to reduce the unevenness of the surface of the ferrite substrate 12 to ensure a flat surface and enable the formation of a fine pattern. However, if the flatness of the ferrite substrate 12 is sufficient, the first insulating layer 15a may not be necessary, and in that case, the first spiral conductor 13A may be formed directly on the ferrite substrate 12.

[0018] The first to third insulating layers 15a to 15c can be formed by spin-coating a photosensitive insulating non-magnetic resin (for example, a photosensitive polyimide resin), exposing it to light, developing it, and thermally curing it.

[0019] The first and second spiral conductors 13A and 13B are circular spirals. The first and second spiral conductors 13A and 13B are both wound around a coil axis Z parallel to a first direction D1. The first and second spiral conductors 13A and 13B roughly overlap each other in a plan view, but do not completely coincide with each other.

[0020] That is, the first spiral conductor 13A viewed from above forms a counterclockwise spiral from the outer peripheral end 13a to the inner peripheral end 13b, and the second spiral conductor 13B viewed from above also forms a counterclockwise spiral from the inner peripheral end 13b to the outer peripheral end 13a. This allows the directions of magnetic fluxes generated by currents flowing through the spiral conductors 13A and 13B to match. For example, magnetic fluxes along the coil axis Z are generated in the inner diameter regions of the spiral conductors 13A and 13B. The magnetic fluxes generated in the spiral conductors 13A and 13B are superimposed and reinforce each other, so a large inductance can be obtained.

[0021] The outer peripheral ends 13a of the first and second spiral conductors 13A and 13B are drawn out to the side of the ferrite substrate 12 or the first insulating layer 15a and connected to a pair of terminal electrodes 20a and 20b, respectively. The inner peripheral end 13b of the first spiral conductor 13A and the inner peripheral end 13b of the second spiral conductor 13B are connected to each other via a contact hole conductor 13c that penetrates the second insulating layer 15b. As a result, the first and second spiral conductors 13A and 13B are connected in series to each other to form a single coil (i.e., a primary coil).

[0022] The first and second spiral conductors 13A and 13B are formed by a fine wiring process. In detail, a Cu film or a multilayer film (Cr / Cu film) in which a Cu film and a Cr film are laminated in order is formed as an underlying conductive film by sputtering or vapor deposition, and then a photoresist film is formed by a spin coating method. Next, the photoresist film is exposed and developed to form a negative pattern of the spiral conductor, and the underlying conductive film is selectively plated and grown using this mask pattern.

[0023] The printed circuit board 16 extends perpendicular to the first direction D1, similar to the ferrite substrate 12. The printed circuit board 16 is placed on one side (upper side) of the ferrite substrate 12 with respect to the first direction D1. The printed circuit board 16 is a support substrate for providing a surface for forming the third and fourth spiral conductors 17A and 17B, and has a circular opening 16a in the center. The opening 16a of the printed circuit board 16 is formed in an area corresponding to the coil axis Z. The thickness of the printed circuit board 16 can be, for example, about 0.06 mm. The material of the printed circuit board 16 is preferably a general printed circuit board material in which glass cloth is impregnated with epoxy resin, and for example, a BT substrate, an FR4 substrate, an FR5 substrate, etc. can be used. A ceramic substrate can also be used as the printed circuit board material. When these printed circuit board materials are used, the spiral conductor can be formed by plating, not by sputtering in the so-called thin film method, so that the thickness of the conductor can be made sufficiently thick. In order to avoid an increase in stray capacitance, the dielectric constant of the printed circuit board 16 is preferably 7 or less (μ≦7).

[0024] The third and fourth spiral conductors 17A and 17B are also circular spirals. The third and fourth spiral conductors 17A and 17B are both wound around a coil axis Z parallel to the first direction D1. The third and fourth spiral conductors 17A and 17B are disposed so as to surround the opening 16a of the printed circuit board 16.

[0025] The third and fourth spiral conductors 17A and 17B roughly overlap each other in a plan view, but do not completely match each other.

[0026] That is, the third spiral conductor 17A viewed from above forms a clockwise spiral from the outer peripheral end 17a to the inner peripheral end 17b, and the fourth spiral conductor 17B viewed from above also forms a clockwise spiral from the inner peripheral end 17b to the outer peripheral end 17a.

[0027] As a result, the directions of magnetic fluxes generated by current flowing through the spiral conductors 17A and 17B are the same. For example, magnetic fluxes are generated in the inner diameter regions of the spiral conductors 17A and 17B along the coil axis Z, which is parallel to the first direction D1. The magnetic fluxes generated in the spiral conductors 17A and 17B are superimposed and reinforce each other, so a large inductance can be obtained.

[0028] The outer circumferential ends 17a of the third and fourth spiral conductors 17A and 17B are drawn out to the side surface of the printed circuit board 16 and connected to a pair of terminal electrodes 20c and 20d, respectively. The inner circumferential end 17b of the third spiral conductor 17A and the inner circumferential end 17b of the fourth spiral conductor 17B are connected to each other via a through-hole conductor 17c that penetrates the printed circuit board 16. As a result, the third and fourth spiral conductors 17A and 17B are connected in series to each other to form a single coil (i.e., a secondary coil).

[0029] In this embodiment, the primary coil L1 and the secondary coil L2 overlap in the first direction D1 and have a common magnetic path. The formation area of ​​the first and second spiral conductors 13A and 13B constituting the primary coil L1 and the formation area of ​​the third and fourth spiral conductors 17A and 17B constituting the secondary coil L2 substantially overlap in a plan view. The formation area of ​​the coil here refers to the occupied area of ​​the planar coil constituted by the spiral conductor. With such a configuration in which the coil formation areas of the primary coil L1 and the secondary coil L2 overlap, the magnetic flux generated by the primary coil L1 and the magnetic flux generated by the secondary coil L2 overlap and reinforce each other, so that a large mutual inductance can be obtained. Therefore, the magnetic coupling between the primary coil L1 and the secondary coil L2 can be strengthened, and a transformer component with high conversion efficiency can be provided.

[0030] Both ends of the primary coil L1 including the first and second spiral conductors 13A and 13B are connected to a pair of terminal electrodes 20a and 20b, respectively, and both ends of the secondary coil L2 including the third and fourth spiral conductors 17A and 17B are connected to a pair of terminal electrodes 20c and 20d, respectively. The first and second spiral conductors 13A and 13B are fine patterns with a narrow pitch, and the conductor width is preferably 2 to 10 μm. With this configuration, the primary coil L1 including the first and second spiral conductors 13A and 13B can be preferably used as a secondary coil of a step-up transformer.

[0031] The thin-film coil layer 14 including these spiral conductors 13A, 13B is formed by a so-called thin-film technique, so that a spiral conductor with a large number of turns can be formed at a very narrow pitch. On the other hand, the third and fourth spiral conductors 17A, 17B are thick-film patterns wider than the first and second spiral conductors 13A, 13B, and preferably have a conductor width of 20 to 100 μm and a conductor thickness of 25 to 150 μm, for example. With this configuration, the secondary coil L2 including the third and fourth spiral conductors 17A, 17B can be preferably used as a primary coil of a step-up transformer. Although not particularly limited, the turn ratio of the primary coil to the secondary coil is preferably 1:2 to 1:20.

[0032] The third and fourth spiral conductors 17A, 17B are formed on the surface of the printed circuit board 16, and therefore can be formed by a so-called semi-additive method.

[0033] In the transformer component 10 according to this embodiment, the number of turns of the primary coil L1 is designed to be greater than the number of turns of the secondary coil L2. In this case, the magnetic flux density of the primary coil L1 is higher than the magnetic flux density of the secondary coil L2.

[0034] In the transformer component 10, the inner diameter area S1 of the primary coil L1 is designed to be relatively large, and is larger than the inner diameter area S2 of the secondary coil L2. This makes it difficult for magnetic flux saturation to occur in the inner diameter region of the primary coil L1, resulting in a transformer component with low loss. On the other hand, the inner diameter area S2 of the secondary coil L2 is designed to be relatively small, which ensures a sufficient line width for the spiral conductors 17A and 17B that constitute the secondary coil L2, thereby achieving low resistance.

[0035] Moreover, the transformer component 10 is designed such that the volume V1 of the magnetic material constituting the main surface 11b on the primary coil L1 side is larger than the volume V2 of the magnetic material constituting the main surface 11a on the secondary coil L2 side in the first direction D1. In other words, the thickness of the magnetic material between the primary coil L1 and the main surface 11b is larger than the thickness of the magnetic material between the secondary coil L2 and the main surface 11a. This makes it difficult for magnetic flux saturation and magnetic flux leakage to occur on the main surface 11b on the primary coil L1 side.

[0036] Furthermore, the primary coil L1 and the secondary coil L2 are positioned very close to each other. In this embodiment, only the insulating layer 15c is interposed between the second spiral conductor 13B and the third spiral conductor 17A. This further strengthens the magnetic coupling between the primary coil L1 and the secondary coil L2, thereby realizing a transformer with high conversion efficiency.

[0037] The third and fourth spiral conductors 17A, 17B can be formed by forming an underlying conductive film (e.g., a Cu film) by electroless plating, attaching a photoresist sheet, exposing and developing the photoresist sheet to form a negative pattern of the spiral conductor, and selectively growing the underlying conductive film by plating using this mask pattern.

[0038] The third and fourth spiral conductors 17A, 17B thus formed are sufficiently thicker than the first and second spiral conductors 13A, 13B, and therefore the DC resistance can be sufficiently reduced.

[0039] The present invention is not limited to the above-described embodiment, and can be modified in various ways. For example, the coil is not limited to a circular ring shape, and may be, for example, an elliptical ring shape or a rectangular ring shape. Furthermore, the number of turns of the coil can be increased or decreased as appropriate.

[0040] As can be understood from the above description, the present specification discloses the following. [Appendix 1] The body and a primary coil provided within the element body and wound around a coil axis along a first direction; a secondary coil formed on a substrate orthogonal to the first direction within the element body, overlapping with the primary coil in the first direction and wound around the coil axis to have a common magnetic path with the primary coil; Equipped with A transformer component, wherein the number of turns of the primary coil is greater than the number of turns of the secondary coil, and the inner diameter area of ​​the primary coil is greater than the inner diameter area of ​​the secondary coil. [Appendix 2] 2. The transformer component of claim 1, wherein the primary coil is formed on a magnetic substrate. [Appendix 3] 3. A transformer component as described in claim 1 or 2, wherein the body is made of a magnetic material, and a volume of the magnetic material constituting the body surface on the primary coil side is larger than a volume of the magnetic material constituting the body surface on the secondary coil side in the first direction. [Explanation of symbols]

[0041] 10...transformer component, 11...element body, 12...ferrite substrate, 16...printed substrate, D1...first direction, L1...primary coil, L2...secondary coil, S1, S2...inner diameter area, Z...coil axis.

Claims

1. The body and a primary coil provided within the element body and wound around a coil axis along a first direction; a secondary coil formed on a substrate orthogonal to the first direction within the element body, overlapping with the primary coil in the first direction and wound around the coil axis to have a common magnetic path with the primary coil; Equipped with A transformer component, wherein the number of turns of the primary coil is greater than the number of turns of the secondary coil, and the inner diameter area of ​​the primary coil is greater than the inner diameter area of ​​the secondary coil.

2. The transformer component according to claim 1 , wherein the primary coil is formed on a magnetic substrate.

3. 3. The transformer component according to claim 1, wherein the base body is made of a magnetic material, and the volume of the magnetic material constituting the base body surface on the primary coil side is larger than the volume of the magnetic material constituting the base body surface on the secondary coil side in the first direction.

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