JP6724688B2 - Coil parts - Google Patents

Description

The present invention relates to a coil component, and more particularly to a coil component using a drum core.

Unlike the coil component using the toroidal core, the coil component using the drum core can be surface-mounted on the printed circuit board, and thus is widely used in portable electronic devices such as smartphones. Further, since the coil component using the drum core has a low height, it contributes to the reduction in thickness of the portable electronic device.

However, in recent years, portable electronic devices have been required to be further thinned, and in order to realize this, coil components using a drum core are required to be further reduced in height. One method of reducing the height of the coil parts is to remove the magnetic top plate that is normally bonded to the drum core.In this case, however, the leakage of magnetic flux increases, so other circuits such as antennas Could have an adverse effect on. On the other hand, since the magnetic top plate made of ferrite is fragile, if its thickness is made thin, its strength becomes insufficient and it may be damaged during mounting or actual use.

In order to solve such a problem, a magnetic powder-containing resin having flexibility may be used as the material of the magnetic top plate instead of ferrite. Since the magnetic powder-containing resin retains a certain level of strength even if it is thin, using a magnetic powder-containing resin as the material for the magnetic top plate can reduce the height while suppressing magnetic flux leakage. Becomes Examples of using magnetic powder-containing resin as the material of the magnetic top plate include coil components described in Patent Documents 1 and 2.

JP-A-9-219318 JP, 2004-363178, A

However, in many cases, the magnetic powder contained in the magnetic powder-containing resin has conductivity, and therefore it is conceivable that a short circuit failure may occur between the magnetic powder and the terminal electrode or the wire. Further, since the magnetic powder-containing resin has a larger coefficient of thermal expansion than the drum core, it is possible that the resin may be separated from the drum core due to temperature changes.

Therefore, an object of the present invention is to provide a coil component that uses a top plate containing a magnetic powder-containing resin while achieving a low profile, and that does not easily cause a short circuit defect or peeling of the top plate. To do.

A coil component according to the present invention includes a drum core having a winding core portion and first and second flange portions provided at both ends of the winding core portion, a wire wound around the winding core portion, and the first and second winding cores. The terminal plate is provided on each of the second flange portions, and the terminal electrodes to which the ends of the wires are connected; and a top plate fixed to the first and second flange portions, the top plate being a binder. A magnetic layer formed by mixing magnetic powder with resin; and a resin layer containing less magnetic powder than the magnetic layer, the resin layer including at least the first and second collar portions and the magnetic layer. It is characterized by being located between layers.

According to the present invention, since the resin layer is interposed between the first and second flange portions and the magnetic layer, it is possible to prevent a short circuit defect between the magnetic layer and the terminal electrode or wire. .. Further, if a material having a coefficient of thermal expansion between the coefficient of thermal expansion of the magnetic layer and the coefficient of thermal expansion of the drum core is used as the material of the resin layer, peeling of the top plate due to temperature change may be prevented. Become. Further, the resin layer can increase the mechanical strength of the top plate.

In the present invention, it is preferable that the resin layer does not substantially contain the magnetic powder. According to this, it becomes possible to prevent a short circuit defect more reliably.

In the present invention, the resin layer preferably contains a non-magnetic filler. According to this, it becomes possible to adjust the coefficient of thermal expansion to a desired value.

In the present invention, the resin layer may cover the entire surface of the magnetic layer, or may be selectively provided between the first and second flange portions and the magnetic layer. According to the former, it is possible to reduce the manufacturing cost of the top plate and more reliably prevent a short circuit defect. On the other hand, according to the latter, it is possible to more reliably prevent the top plate from peeling due to the temperature change.

It is preferable that the coil component according to the present invention further includes an adhesive that bonds the first and second flanges to the resin layer of the top plate. According to this, the insulating effect of the adhesive can be expected.

In the present invention, the magnetic layer of the top plate has a lower surface facing the resin layer side and an upper surface located on the side opposite to the lower surface, and the surface layer on the upper surface side of the surface layer portion on the lower surface side. It is preferable that the part has a higher density of the binder resin. According to this, the insulating property of the upper surface of the top plate is improved. As a result, short-circuit defects due to the top surface of the top plate coming into contact with other electronic components are prevented, so that a highly reliable coil component can be obtained. Moreover, since the density of the magnetic powder is high in the surface layer portion on the lower surface side of the magnetic layer, the magnetic path passing through the top plate is shortened, and higher magnetic characteristics can be obtained.

In the present invention, the magnetic powder is preferably a metal soft magnetic powder. According to this, it becomes possible to obtain high magnetic characteristics. In particular, the soft metal magnetic powder preferably has a flat shape. According to this, it becomes possible to obtain higher magnetic characteristics.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the coil component which implement|achieves a low profile and is hard to produce a short circuit defect and peeling of a top plate.

FIG. 1 is a perspective view of a coil component 11 according to a first embodiment of the present invention as seen from an oblique direction. FIG. 2 is a plan view of the coil component 11 as seen from the mounting surface. FIG. 3 is a sectional view of the coil component 11. FIG. 4 is a schematic cross-sectional view for explaining the structure of the top plate 30. FIG. 5 is a schematic diagram for explaining the shape of the magnetic powder 35 included in the top plate 30. FIG. 6 is a schematic cross-sectional view for explaining the structure of the magnetic layer 31. 7A and 7B are electron micrographs of the magnetic layer 31, in which FIG. 7A is a photograph of the surface 31a and FIG. 7B is a photograph of the surface 31b. FIG. 8 is a schematic diagram for explaining a method of producing the sheet S1 in which the magnetic layer 31 is applied to the surface of the base film F. FIG. 9 is a schematic diagram for explaining a method of manufacturing the sheet S2 in which the resin layer 32 is applied to the surface of the magnetic layer 31. FIG. 10 is a process chart for explaining the method for manufacturing the coil component 11. FIG. 11 is a perspective view of the coil component 12 according to the second embodiment of the present invention as seen from an oblique direction. FIG. 12 is a sectional view of the coil component 12.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
1 to 3 are diagrams showing a configuration of a coil component 11 according to a first embodiment of the present invention, FIG. 1 is a perspective view seen obliquely from above, and FIG. 2 is a plan view seen from a mounting surface. 3 is a sectional view.

As shown in FIGS. 1 to 3, the coil component 11 according to the first embodiment of the present invention includes a drum core 20 and a top plate 30. The drum core 20 has a winding core portion 21 whose axial direction is the x direction, and first and second flange portions 22 and 23 provided at both ends of the winding core portion 21 in the x direction. The drum core 20 is made of a ceramic material having a high magnetic permeability such as ferrite, and has a structure in which a winding core portion 21 and flange portions 22 and 23 are integrated.

Two wires W are wound around the winding core portion 21, and both ends of these wires W are connected to the terminal electrodes E1 to E4 provided on the collar portions 22 and 23. In the present embodiment, the terminal electrodes E1 and E2 are formed on one flange portion 22, and the terminal electrodes E3 and E4 are formed on the other flange portion 23. The terminal electrodes E1 to E4 form the xy planes of the collar portions 22 and 23 forming the mounting surface, the xy planes of the collar portions 22 and 23 forming the upper surface located on the opposite side of the mounting surface, and the outside surfaces. The collar portions 22 and 23 are continuously formed on the yz plane. In the present embodiment, the wires W are connected to the terminal electrodes E1 to E4 provided on the upper surfaces of the collar portions 22 and 23, but the terminal electrodes E1 to E4 provided on the mounting surfaces of the collar portions 22 and 23 are connected. You may connect the wire W to. In this case, it is not necessary to provide the terminal electrodes E1 to E4 on the upper surfaces of the collar portions 22 and 23.

The application of the coil component 11 according to the present embodiment is not particularly limited, and may be a general-purpose coil component for inductance, or a specific application, for example, a coil for a common mode filter, a pulse transformer, a balun transformer, or the like. It may be a component. Therefore, the number of wires W wound around the winding core portion 21, the number of windings, the winding direction, the winding method, and the like are not particularly limited. Although the size of the coil component 11 is not particularly limited, the length in the x direction is about 1.6 mm, the width in the y direction is about 1.0 mm, and the height in the z direction is about 0.55 mm to 0.65 mm.

As shown in FIGS. 1 and 3, the top plate 30 is fixed to the xy planes forming the upper surfaces of the collar portions 22 and 23 with an adhesive 40. As shown in FIG. 4, the top plate 30 has a laminated structure of a magnetic layer 31 and a resin layer 32, and the magnetic layer 31 is laminated on the upper side and the resin layer 32 is laminated on the lower side. That is, the resin layer 32 is located between the collar portions 22 and 23 and the magnetic layer 31.

The magnetic layer 31 is made of a magnetic powder-containing resin in which a magnetic powder 35 is mixed with a binder resin 34, and has a magnetic permeability higher than that of a normal resin. Since the top plate 30 having the magnetic layer 31 is fixed to the upper surfaces of the collar portions 22 and 23 so as to straddle the winding core portion 21, the drum core 20 and the magnetic layer 31 form a closed magnetic circuit. Therefore, leakage of magnetic flux is reduced as compared with the case where a top plate made of only resin is used, and it is possible to reduce magnetic influence on other circuits, for example, an antenna circuit. The top plate 30 is also used as a suction surface for handling when mounting on a printed circuit board.

As described above, the magnetic powder-containing resin forming the magnetic layer 31 is obtained by mixing the binder resin 34 with the magnetic powder 35. Among them, the binder resin 34 preferably has an acrylic acid ester copolymer as a main chain and includes a cross-linked structure by a urethane bond. On the other hand, as the magnetic powder 35, as shown in FIG. 5, it is preferable to use a metal soft magnetic powder having a flat shape in the xy directions. When using the soft metal magnetic powder having a flat shape, it is preferable to mix it with the binder resin 34 so that the main plane of the soft metal magnetic powder is the xy plane. According to this, the magnetic permeability in the x direction, which is the direction of the magnetic flux passing through the magnetic layer 31, is enhanced, and the soft metal magnetic powder having a flat shape also functions as an electromagnetic shield.

The resin layer 32 plays a role of preventing direct contact between the collar portions 22 and 23 and the magnetic layer 31 by interposing the resin layer 32. The resin layer 32 is interposed because the magnetic powder 35 contained in the magnetic layer 31 has conductivity and may be exposed from the binder resin 34. As a material for the resin layer 32, an insulating resin material similar to the binder resin 34 can be used. By using the resin layer 32 made of such an insulating resin material, the withstand voltage between the magnetic layer 31 and the terminal electrodes E1 to E4 and the wire W is significantly improved. can do. Furthermore, since the resin layer 32 also functions as a cushioning material, impact resistance is also improved.

A magnetic or non-magnetic filler may be added to the resin layer 32. However, when the content of the magnetic powder is too large, the insulating property is deteriorated. Therefore, when the magnetic powder is added to the resin layer 32, the content of the magnetic powder needs to be smaller than that of the magnetic layer 31. On the other hand, the non-magnetic filler can be added to adjust the physical properties such as the coefficient of thermal expansion. If the coefficient of thermal expansion of the resin layer 32 is adjusted between the coefficient of thermal expansion of the magnetic layer 31 and the coefficient of thermal expansion of the drum core 20 by adding a non-magnetic filler, peeling of the top plate 30 due to temperature change can be prevented. Will also be possible. Examples of non-magnetic fillers include talc and mica.

As described above, in the coil component 11 according to the present embodiment, the top plate 30 fixed to the drum core 20 has a laminated structure of the magnetic layer 31 and the resin layer 32, and the resin layer 32 includes the drum core 20 and the magnetic layer 31. It is possible to improve the withstand voltage, impact resistance, peeling strength, etc. while achieving a low profile because it is located between the two.

FIG. 6 is a schematic cross-sectional view for explaining the structure of the magnetic layer 31.

As shown in FIG. 6, in the magnetic layer 31, the distribution of the binder resin 34 and the magnetic powder 35 in the thickness direction (z direction) is not completely uniform, and the surface layer portion 31A and the surface layer portion 31B have different characteristics. Sometimes.

Specifically, in the inner layer portion 31C of the magnetic layer 31, the magnetic powder 35 is distributed almost uniformly in the binder resin 34, while in the surface layer portion 31B, the density of the magnetic powder 35 is lower than that of the inner layer portion 31C. The density of the binder resin 34 is higher than that of the inner layer portion 31C. As a result, the amount of the magnetic powder 35 exposed on the surface 31b is reduced, and typically, the magnetic powder 35 is hardly exposed. In this case, almost the entire surface 31b is covered with the binder resin 34. On the other hand, the surface layer portion 31A is almost the same as the inner layer portion 31C. That is, in the surface layer portion 31A, the density of the magnetic powder 35 in the binder resin 34 is almost the same as that in the inner layer portion 31C. Therefore, the magnetic powder 35 may be exposed to some extent from the surface 31a.

7A and 7B are electron micrographs of the magnetic layer 31 actually manufactured. FIG. 7A is a photograph of the surface 31a, and FIG. 7B is a photograph of the surface 31b. In these photographs, the part shown in black is the binder resin 34, and the part shown in white is the magnetic powder 35.

As shown in FIG. 7A, the surface layer portion 31A on the surface 31a side has a high density of the magnetic powder 35 and a low density of the binder resin 34. Therefore, many magnetic powders 35 appear white when photographed with an electron microscope. I understand. It can also be seen that many magnetic powders 35 are exposed on the surface 31a. On the other hand, as shown in FIG. 7B, the surface layer portion 31B on the front surface 31b side has a low density of the magnetic powder 35 and a high density of the binder resin 34. I understand. In particular, there is almost no magnetic powder 35 exposed on the surface 31b.

As described above, the magnetic layer 31 is characterized in that the surface layer portion 31B has a higher density of the binder resin 34 than the surface layer portion 31A. The difference between the surface layers 31A and 31B is caused by the manufacturing process of the top plate 30 described later.

By utilizing such a difference in surface property, it is possible to give the coil component 11 more preferable characteristics depending on the purpose. For example, if the surface 31a is the lower layer side (the resin layer 32 side) and the surface 31b is the upper layer side, the insulating property on the upper surface side of the top plate 30 is enhanced, so that the upper surface of the top plate 30 contacts with other electronic components. It is possible to prevent a short circuit defect due to Moreover, in the surface layer portion 31A on the lower surface side of the magnetic layer 31, since the density of the binder resin 34 is low and more magnetic powder 35 is present, the magnetic path passing through the top plate 30 is shortened, and the high magnetic field is high. It is also possible to obtain characteristics.

On the contrary, if the surface 31b is the lower layer side (the resin layer 32 side) and the surface 31a is the upper layer side, the dielectric breakdown voltage between the magnetic layer 31 and the terminal electrodes E1 to E4 and the wire W is further increased. In addition, impact resistance and peel strength are further improved.

Although not particularly limited, the thickness of the top plate 30 in the z direction is preferably 100 μm or less, more preferably 75 μm or less, and particularly preferably about 60 μm. If the thickness of the top plate 30 is 100 μm or less, it is possible to reduce the height of the entire coil component 11 in the z direction. When the thickness of the top plate is reduced to 100 μm or less, if ferrite is used, it may be damaged due to insufficient strength. If the top plate 30 is used, damage will not occur even if the thickness is reduced to 100 μm or less. The lower limit of the thickness of the top plate 30 is not particularly limited, but is preferably 30 μm or more. This is because if the thickness of the top plate 30 is reduced to less than 30 μm, the strength will be insufficient and it will be difficult to secure sufficient magnetic characteristics. In order to sufficiently suppress the leakage of magnetic flux, the magnetic permeability of the magnetic layer 31 forming the top plate 30 is preferably 30 or more.

The binder resin used for the magnetic layer 31 is required to have predetermined flexibility, heat resistance and strength. The reason why flexibility and strength are required is that damage is not caused even when the thickness of the top plate 30 is reduced to, for example, 100 μm or less, and the reason why heat resistance is required is that deformation occurs during reflow. This is because it does not occur. Therefore, a material having high strength but low flexibility, or a material having high flexibility but low heat resistance is not suitable. Since the reflow temperature is about 260° C., it is necessary to use at least a binder resin that does not deform at the temperature.

In consideration of these points, in this embodiment, a binder resin having an acrylic acid ester copolymer as a main chain and including a cross-linked structure by a urethane bond is used. Although the composition is not particularly limited, it is preferable that the acrylate copolymer contains at least a copolymer structure of ethyl acrylate and a copolymer structure of butyl acrylate. This is because flexibility is added by the copolymer structure of butyl acrylate while ensuring high strength by the copolymer structure of ethyl acrylate. In addition, it is preferable that the acrylic acid ester copolymer further contains a copolymer structure of acrylonitrile. This is because the heat resistance and strength are increased by including the copolymer structure of acrylonitrile.

The top plate 30 can be manufactured by the following method. First, a binder solution is prepared by dissolving a solute containing ethyl acrylate, butyl acrylate, and acrylonitrile as a main monomer having a hydroxyl group or a carboxyl group as a functional group in an organic solvent such as methyl ethyl ketone, and the magnetic powder and the curing agent are added to the binder solution. Are mixed to prepare a mixed solution. Isocyanate is preferably used as the curing agent. As the isocyanate, for example, an aromatic isocyanate or an isocyanate having a triazine ring in its structure is preferably used, and more preferably one molecule has a plurality of isocyanate groups. As a result, the hydroxyl group or carboxyl group that the acrylic acid ester copolymer has as a functional group reacts with the isocyanate to form a crosslinked structure. Further, fillers other than magnetic powder, such as talc and mica, may be further mixed.

Next, as shown in FIG. 8, the above-mentioned mixed solution is applied to the base film F, and heated to wind the solvent in the mixed solution to dry the solvent and cure the binder resin, and wind the film on a roll. The magnetic powder may be oriented in a predetermined direction by applying a magnetic field when the mixed solution is applied to the base film F. Thereby, the sheet S1 in which the magnetic layer 31 made of the magnetic powder-containing resin is applied to the surface of the base film F is obtained. As the base film F, a PET film can be used. Here, the content ratio of the magnetic powder in the cured magnetic powder-containing resin is preferably 50 to 90% by weight. This is because if the content ratio of the magnetic powder is less than 50% by weight, sufficient magnetic permeability cannot be obtained, and if it exceeds 90% by weight, the magnetic powder is more likely to fall off from the cut surface of the top plate 30.

When the magnetic layer 31 made of a magnetic powder-containing resin is applied to the surface of the base film F, the magnetic powder-containing resin has a slightly different characteristic between the surface layer on the base film F side and the exposed surface layer on the opposite side. .. It is considered that this is due to the surface tension of the uncured binder resin, and the density of the magnetic powder 35 is low in the surface layer portion 31B on the base film F side, while the magnetic powder is low in the surface layer portion 31A on the exposed side. The density of 35 becomes high.

Next, after peeling off the magnetic layer 31 from the base film F, as shown in FIG. 9, a resin material forming the resin layer 32 is applied to the surface 31a located on the opposite side of the base film F and heated. Take up with a roll while curing by. Thereby, the sheet S2 in which the resin layer 32 is applied to the surface of the magnetic layer 31 is obtained.

Next, as shown in FIG. 10A, the sheet S2 is die-cut into a plane shape of the top plate 30 with a die. Next, as shown in FIG. 10B, an epoxy adhesive 40 is applied to the die-cut portion, and then the drum core 20 around which the wire W is wound is adhered as shown in FIG. 10C. .. Then, by separating the drum core 20 to which the top plate 30 is adhered from the sheet body, the coil component 11 according to the present embodiment is completed.

When the coil component 11 is manufactured by such a method, the surface of the magnetic powder-containing resin facing the base film F side at the time of coating, that is, the surface 31b of the magnetic layer 31 on the side where the binder resin 34 has a high density is formed. As an upper surface, it can be adhered to the drum core 20. The resin layer 32 may be formed without peeling the magnetic layer 31 from the base film F. In this case, the base film F may be peeled off after performing the step shown in FIG.

On the other hand, when the surface 31 a of the magnetic layer 31 on the side where the binder resin 34 has a low density is used as the upper surface to adhere to the drum core 20, the base film F itself can be used as the resin layer 32. According to this, it is possible to reduce the manufacturing cost because the coating process is performed only once. However, in this case, as the material of the base film F, it is necessary to use a resin material having higher heat resistance instead of the PET resin.

<Second Embodiment>
11 and 12 are views showing the configuration of the coil component 12 according to the second embodiment of the present invention, FIG. 11 is a perspective view seen obliquely from above, and FIG. 12 is a sectional view.

As shown in FIGS. 11 and 12, in the coil component 12 according to the second embodiment of the present invention, the resin layer 32 is selectively provided between the collar portions 22 and 23 and the magnetic layer 31. Different from the coil component 11 according to the first embodiment described above. That is, the resin layer 32 is divided into two in plan view. Since the other configurations are the same as those of the coil component 11 according to the first embodiment, the same reference numerals are given to the same elements, and duplicate description will be omitted.

According to the present embodiment, since the resin layer 32 is divided into two, even if there is a relatively large difference between the thermal expansion coefficient of the resin layer 32 and the thermal expansion coefficient of the drum core 20, the top plate 30 is peeled off. Has the advantage of being less likely to occur. In the examples shown in FIGS. 11 and 12, the resin layer 32 and the flange portions 22 and 23 have substantially the same plane size. However, at least a part of the flange portions 22 and 23 and the magnetic layer 31 are provided. It is sufficient if the resin layer 32 is interposed. However, in order to further ensure the dielectric strength and impact resistance, it is preferable to cover the entire surfaces of the flange portions 22 and 23 with the resin layer 32 in plan view (viewed from the z direction).

The coil component 12 according to the present embodiment is preferably manufactured by pasting the resin layer 32, which has been cut into a predetermined size, on the upper surfaces of the collar portions 22 and 23, and then bonding the magnetic layer 31. According to this method, the positioning work of the resin layer 32 can be performed more easily than the method of attaching the resin layer 32 to the magnetic layer 31.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. It goes without saying that it is included in the range.

11, 12 Coil parts 20 Drum core 21 Core parts 22, 23 Collar part 30 Top plate 31 Magnetic layers 31A, 31B Surface layer part 31C Inner layer parts 31a, 31b Surface 32 Resin layer 34 Binder resin 35 Magnetic powder 40 Adhesives E1 to E4 terminals Electrode F Base film S1, S2 Sheet W Wire

Claims (8)

A drum core having a winding core portion and first and second flange portions provided at both ends of the winding core portion;
A wire wound around the winding core,
Terminal electrodes provided on the first and second flanges, respectively, and connecting the ends of the wires to each other;
A top plate fixed to the first and second flanges,
The top plate includes a magnetic layer formed by mixing a binder resin with magnetic powder, and a resin layer in which the content of the magnetic powder is less than that of the magnetic layer,
The resin layer is located at least between the first and second flange portions and the magnetic layer ,
The magnetic layer has a lower surface facing the resin layer side and an upper surface located on the opposite side to the lower surface, and the surface layer portion on the upper surface side of the binder resin is more than the surface layer portion on the lower surface side. Coil parts characterized by high density . The coil component according to claim 1, wherein the resin layer does not substantially contain the magnetic powder. The coil component according to claim 1, wherein the resin layer contains a non-magnetic filler. The coil component according to any one of claims 1 to 3, wherein the resin layer covers the entire surface of the magnetic layer. The coil component according to claim 1, wherein the resin layer is selectively provided between the first and second flange portions and the magnetic layer. The coil component according to claim 1, further comprising an adhesive that bonds the first and second flanges to the resin layer of the top plate. The coil component according to any one of claims 1 to 6 , wherein the magnetic powder is a soft metal magnetic powder. The coil component according to claim 7 , wherein the metal soft magnetic powder has a flat shape.