JP6955382B2 - Laminated coil - Google Patents

Description

The present disclosure relates to laminated coils. More specifically, the present disclosure relates to a laminated coil including a magnetic substrate made of a sintered body of a magnetic material and a resin layer formed on the magnetic substrate.

In a conventional laminated coil, generally, an insulating resin layer including a coil conductor is formed on a magnetic substrate made of a sintered body of a magnetic material such as ferrite, and a cover resin layer is formed on the insulating resin layer. Made in. This cover resin layer contains, for example, filler particles such as ferrite particles and an insulating resin such as an epoxy resin. Such conventional laminated coils are disclosed in, for example, JP-A-2010-087030 and JP-A-2013-153184.

JP-A-2010-087030 Japanese Unexamined Patent Publication No. 2013-153184

When manufacturing a conventional laminated coil, the resin contained in the insulating resin layer and the cover resin layer is thermally cured by heating the laminated body composed of the magnetic substrate, the insulating resin layer, and the cover resin layer. At this time, the resin of the insulating resin layer and the cover resin layer shrinks, but the magnetic substrate does not shrink because it has already been sintered. Therefore, in the conventional laminated coil, there is a problem that stress acts on the magnetic substrate due to heating in the manufacturing process, and the magnetic substrate is easily deformed. Since the cover resin layer is formed thicker than the insulating resin layer in the laminated coil, a large stress acts on the magnetic substrate due to the shrinkage of the cover resin layer.

Therefore, one of the purposes of the present disclosure is to provide a laminated coil in which the heat shrinkage of the cover resin layer generated during thermosetting is suppressed. Other objects of the present invention will be made clear through the description throughout the specification.

The present inventor has discovered that the amount of shrinkage of the insulating layer during thermosetting can be suppressed by containing the filler in the cover resin layer at a high filling rate.

The laminated coil according to an embodiment of the present invention is formed on a magnetic substrate made of a sintered body of a magnetic material, an insulating resin layer formed on the magnetic substrate, and the insulating resin layer. A cover resin layer and a coil conductor embedded in the insulating resin layer are provided. In one embodiment of the present invention, the insulating resin layer contains a first resin and a first filler particle, and the cover resin layer contains a second resin and a second filler particle.

In one embodiment of the present invention, the filling rate of the second filler particles in the cover resin layer is higher than the filling rate of the first filler particles in the insulating resin layer. According to these embodiments, the filling rate of the second filler particles in the cover resin layer is higher than the filling rate of the first filler particles in the insulating resin layer, so that the second filler particles of the cover resin layer are filled. Even if the resin is heat-cured, the amount of shrinkage of the cover resin layer is small. Therefore, it is possible to prevent the magnetic substrate from being deformed during thermosetting. In a more specific embodiment, the filling rate of the second filler particles in the cover resin layer is 70% by volume or more, more preferably 80% by volume or more.

In one embodiment of the invention, the second filler particles are spherical. This makes it easier to improve the filling rate of the second filler particles as compared with the case where the filler particles are not spherical.

The laminated coil according to an embodiment of the present invention is formed on a magnetic substrate made of a sintered body of a magnetic material, an insulating resin layer formed on the magnetic substrate, and the insulating resin layer. A cover resin layer and a coil conductor embedded in the insulating resin layer are provided. In one embodiment of the present invention, the insulating resin layer contains a first resin, and the cover resin layer contains a second resin and filler particles. In one embodiment of the present invention, the insulating resin layer is configured so as not to contain filler particles. Further, in one embodiment of the present invention, the filler particles contained in the cover resin layer are metallic magnetic particles. In one embodiment of the present invention, the filling rate of the filler particles in the cover resin layer is 80% by volume or more. According to these embodiments, even if the second resin of the cover resin layer is thermally cured, the amount of shrinkage of the cover resin layer can be suppressed to such an extent that the magnetic substrate is not deformed.

According to the disclosure of the present specification, it is possible to provide a laminated coil in which the thermal shrinkage of the insulating layer generated at the time of thermosetting is suppressed.

It is a perspective view of the laminated coil which concerns on one Embodiment of this invention. It is an exploded perspective view of the laminated coil which concerns on one Embodiment of this invention. It is a top view which shows the 1st insulating layer provided in the laminated coil of FIG. 2 and the 1st conductor layer formed in the 1st insulating layer. It is a top view which shows the 3rd insulating layer provided in the laminated coil of FIG. 2 and the 3rd conductor layer formed in the 3rd insulating layer. It is a top view which shows the 4th insulating layer provided in the laminated coil of FIG. 2 and the 4th conductor layer formed in the 4th insulating layer. FIG. 5 is a cross-sectional view taken along the line AA of the laminated coil of FIG.

Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. The components common to the plurality of drawings are designated by the same reference numerals throughout the plurality of drawings. It should be noted that each drawing is not always drawn to the correct scale for convenience of explanation.

FIG. 1 is a perspective view of a laminated coil according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the laminated coil shown in FIG. 1, and FIG. 6 is an A- of the laminated coil of FIG. A cross-sectional view. In these figures, a laminated common mode coil is shown as an example of a laminated coil to which the present invention can be applied. The laminated common mode coil 1 includes a magnetic substrate 2, an insulating resin layer 3, a cover resin layer 4, and terminal electrodes 5a, 5b, 7a, and 7b. The laminated common mode coil 1 has dimensions of, for example, 0.45 mm × 0.3 mm × 0.23 mm. As will be apparent to those skilled in the art, laminated coils can be used in a variety of applications other than common mode coils. For example, the multilayer coil may be various inductors incorporated in a power supply line or a signal line. These inductors can be used, for example, for voltage conversion in power supply circuits or for chokes that cut high frequency components, and for matching or resonance in signal lines. The inventions disclosed herein can be applied to these various inductors.

The magnetic substrate 2 is a sintered body made of a magnetic material. The magnetic substrate 2 is obtained, for example, by mixing a magnetic material with an organic binder to prepare a mixture, molding the mixture into a sheet to prepare a molded body, and firing the molded body. The magnetic material used to prepare the magnetic substrate 2 includes, for example, a ferrite material and a metallic magnetic material. As the ferrite material for the magnetic substrate 2, for example, Ni-Zn ferrite and Mn-Zn ferrite can be used. Further, as the metallic magnetic material for the magnetic substrate 2, for example, an alloy-based Fe-Si-Cr, Fe-Si-Al, or Fe-Ni, or a material obtained by mixing these can be used. The material of the magnetic substrate 2 applicable to the present invention is not limited to that specified in the present specification.

The insulating resin layer 3 is formed by laminating a plurality of insulating layers and conductor layers formed on the plurality of insulating layers. In one embodiment of the present invention, each insulating layer is made of a resin in which a large number of filler particles 3a (see FIG. 6) are dispersed. In another embodiment of the invention, each insulating layer is made of a resin that does not contain filler particles. In one embodiment of the present invention, the resin contained in the insulating resin layer 3 is a heat-curable resin having excellent insulating properties, such as epoxy resin, polyimide resin, polystyrene (PS) resin, and high-density polyethylene (HDPE). Resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinyl fluoride (PVDF) resin, phenol (Phenolic) resin, polytetrafluoroethylene (PTFE) resin, or polybenzoxazole (PBO) resin. The insulating resin layer 3 will be further described later with reference to FIG. The insulating resin layer 3 is formed so as to have a thickness of 30 μm to 60 μm.

The cover resin layer 4 is obtained by applying a resin in which a large number of filler particles 4a are dispersed on the insulating resin layer 3. In one embodiment of the present invention, the resin contained in the cover resin layer 4 is a heat-curable resin having excellent insulating properties, such as epoxy resin, polyimide resin, polystyrene (PS) resin, and high-density polyethylene (HDPE). Resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinyl fluoride (PVDF) resin, phenol (Phenolic) resin, polytetrafluoroethylene (PTFE) resin, or polybenzoxazole (PBO) resin. The resin of the cover resin layer 4 may be the same as the resin of the insulating resin layer 3, or may be different.

In one embodiment of the present invention, the filler particles 3a and the filler particles 4a are ferrite material particles, metallic magnetic particles, _{inorganic material particles such as SiO 2} and Al ₂ O ₃ , and glass-based particles. The particles of the ferrite material applicable to the present invention are, for example, Ni-Zn ferrite particles or Ni-Zn-Cu ferrite particles. The metal magnetic particles applicable to the present invention are materials that exhibit magnetism in unoxidized metal portions, and are, for example, particles containing unoxidized metal particles and alloy particles. Metallic magnetic particles applicable to the present invention include, for example, alloy-based Fe-Si-Cr, Fe-Si-Al, or Fe-Ni, amorphous Fe-Si-Cr-BC, or Fe. Includes particles of −Si—B—Cr, Fe, or a mixture of these. The metallic magnetic particles applicable to the present invention further include Fe-Si-Al and FeSi-Al-Cr particles. The green compact obtained from these particles can also be used as the metal magnetic particles of the present invention. Further, those having an oxide film formed by heat-treating the surface of these particles or green compacts can also be used as the metal magnetic particles of the present invention. The metallic magnetic particles applicable to the present invention are produced, for example, by an atomizing method. Further, the metallic magnetic particles applicable to the present invention can be produced by using a known method. In addition, commercially available metal magnetic particles can also be used in the present invention. Examples of commercially available metal magnetic particles include PF-20F manufactured by Epson Atomix Co., Ltd. and SFR-FeSiAl manufactured by Nippon Atomize Processing Co., Ltd. Such metal magnetic particles have a spherical particle shape, and the particles are easily brought close to each other so that the particles are bonded to each other by an oxide film, and the specific gravity is high. Therefore, Ni—Zn and Mn. The filling rate can be easily increased as compared with the case where the ferrite magnetic particles of −Zn are used. By increasing the filling rate of the filler particles, the shrinkage of the cover resin layer when the resin is thermoset can be further suppressed, and the magnetic permeability (μ) can be increased. By increasing the magnetic permeability (μ), the electrical characteristics of the laminated coil can be improved.

In one embodiment of the present invention, one or both of the filler particles 3a and the filler particles 4a are formed in a flat shape. The filler particles 3a and the filler particles 4a formed in a flat shape may have, for example, an aspect ratio (flatness) of 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more. The aspect ratio of the filler particles means the ratio of the length in the longest axial direction to the length in the shortest axial direction of the particles (length in the direction of the longest axis / length in the shortest axial direction).

In one embodiment of the present invention, the filler particles 3a take a posture in which the longest axial direction of a part or all of the filler particles is oriented in a direction parallel to the coil axis CA and the minor axis thereof is oriented in a direction perpendicular to the coil axis CA. Is included in the insulating resin layer 3. When the filler particles 3a take such an attitude, the magnetic permeability in the direction parallel to the coil shaft CA of the insulating resin layer 3 becomes larger than the magnetic permeability in the direction perpendicular to the coil shaft CA. As a result, the direction parallel to the coil axis CA becomes the direction in which the insulating resin layer 3 is easily magnetized, and the direction perpendicular to the coil axis CA becomes the direction in which the insulating resin layer 3 is difficult to magnetize. Since the magnetic flux is directed in a direction substantially parallel to the coil shaft CA in the insulating resin layer 3, the effective magnetic permeability of the laminated coil can be improved by setting the direction parallel to the coil shaft CA to the easy magnetization direction. When the present invention is applied to a resonance inductor or various other inductors, the flat-shaped filler particles 3a are suitable as filler particles for the insulating resin layer 3.

In one embodiment of the present invention, the filler particles 4a take a posture in which the longest axial direction of a part or all of the filler particles is oriented in a direction perpendicular to the coil axis CA and the minor axis thereof is oriented in a direction parallel to the coil axis CA. Is included in the cover resin layer 4. When the filler particles 4a take such an attitude, the magnetic permeability in the direction perpendicular to the coil shaft CA of the cover resin layer 4 becomes larger than the magnetic permeability in the direction parallel to the coil shaft CA. As a result, the direction perpendicular to the coil axis CA becomes the direction in which the cover resin layer 4 is easily magnetized, and the direction parallel to the coil axis CA becomes the direction in which the cover resin layer 4 is difficult to magnetize. In the cover resin layer 4, the magnetic flux is oriented in a direction substantially perpendicular to the coil axis CA except for the vicinity of the boundary with the insulating resin layer 3. Therefore, by setting the direction perpendicular to the coil axis CA as the easy magnetization direction, the laminated common The effective magnetic permeability of the mode coil 1 can be improved. Even when the present invention is applied to a resonance inductor or various other inductors, the direction perpendicular to the coil axis CA of the flat-shaped filler particles 4a is set as the direction in which the cover resin layer 4 is easily magnetized. The effective magnetic permeability of various inductors can be improved. When metal magnetic particles are used as the filler particles 3a, eddy currents are generated in the metal magnetic particles, and core loss is likely to occur. In this case, the effective magnetic permeability of the laminated coil of the present invention is increased and the core loss is suppressed to be low by setting the direction perpendicular to the coil axis CA of the flat-shaped filler particles 4a as the direction in which the cover resin layer 4 is easily magnetized. be able to. As a result, such a laminated coil can be used even in a high frequency region. Further, by arranging the flat-shaped filler particles 4a in a posture in which the longest axial direction thereof faces the direction perpendicular to the coil axis CA, the linear expansion coefficient in the direction perpendicular to the coil axis CA can be reduced, and as a result, the cover resin. The thermal stress difference between the layer 4 and the magnetic substrate 2 can be reduced.

In one embodiment, the amounts of the filler particles 4a and the filler particles 3a are adjusted so that the filling rate of the filler particles 4a in the cover resin layer 4 is higher than the filling rate of the filler particles 3a in the insulating resin layer 3. NS. Preferably, the filling rate of the filler particles 4a is 10% or more larger than the filling rate of the filler particles 3a, and more preferably, the filling rate of the filler particles 4a is 20% or more with respect to the filling rate of the filler particles 3a. big.

In one embodiment of the present invention, the filler particles 4a in the cover resin layer 4 form a part of the magnetic circuit. Therefore, the filling rate has a correlation with the magnetic permeability of the magnetic circuit portion. Specifically, the higher the filling rate of the filler particles 4a in the cover resin layer 4, the higher the magnetic permeability of the magnetic circuit. On the other hand, in forming the cover resin layer, considering the handleability in the manufacturing method and considering that a large pressure is not applied in the manufacturing method, the upper limit of the filling rate of the filler particles 4a in the cover resin layer 4 is set. There is a limit. In consideration of these points, in one embodiment of the present invention, the filling rate of the filler particles 4a suitable for forming a good magnetic circuit having a high magnetic permeability in a manufacturing method with good handleability is 70% by volume or more and 90%. It is considered to be less than% by volume. The filling rate of the filler particles 3a is selected so as to be smaller than this value.

In one embodiment of the present invention, the filling rate of the filler particles 4a in the cover resin layer 4 is 80% by volume or more. The insulating resin layer 3 is usually formed thinner than the cover resin layer 4, and since a coil conductor that does not shrink due to heat is embedded in the insulating resin layer 3, it does not easily shrink during thermosetting. Therefore, the shrinkage amount of the insulating resin layer 3 at the time of thermosetting is suppressed as compared with the shrinkage amount of the cover resin layer 4. Therefore, even if the insulating resin layer 3 does not contain the filler particles 3a, shrinkage during thermosetting is suppressed.

The terminal electrodes 5a, 5b, 7a, 7b are provided on the side surface of the insulating resin layer 3 and extend to the upper surface and the lower surface of the laminated common mode coil 1 as shown in the drawing. The terminal electrodes 5a, 5b, 7a, 7b are formed, for example, by applying Ag paste to the side surface of the insulating resin layer 3.

Next, the insulating resin layer 3 will be described with reference to FIGS. 2 to 5. When the vertical direction is referred to in the present specification, the upper direction of FIG. 2 is referred to as the upper direction and the lower direction of FIG. 2 is referred to as the lower direction, unless otherwise understood in the context. As shown in the exploded perspective view of FIG. 2, in one embodiment of the present invention, the insulating resin layer 3 is an insulating layer 11 and a conductor layer laminated between the magnetic substrate 2 and the cover resin layer 4. 12. An insulating layer 31, a conductor layer 32, an insulating layer 41 for an extraction electrode, and an extraction conductor layer 42 are provided.

The insulating layer 11, the insulating layer 31, and the insulating layer 41 for the extraction electrode are all layers made of a resin in which the filler particles 3a are dispersed, and have excellent insulating properties. The conductor layer 12, the conductor layer 32, and the lead conductor layer 42 are made of a metal material such as Ag. It is desirable that this metal material has excellent conductivity and workability. As this metal material, Cu or Al can be used in addition to Ag. The materials of each of these insulating layers and each conductor layer are merely examples, and various materials other than those explicitly described in the present specification may be used depending on the required performance and required characteristics of the laminated common mode coil 1. Can be used.

As shown in FIG. 2, in the insulating resin layer 3, the insulating layer 11 is formed on the magnetic substrate 2. A conductor layer 12 is formed on the insulating layer 11. As shown in FIG. 3, the conductor layer 12 has a coil conductor 13, a drawer conductor 14 having one end connected to the outer end of the coil conductor 13, and one end thereof to the inner end of the coil conductor 13. A lead-out conductor 15 connected to the lead-out conductor 15 and a lead-out electrode 16 connected to the lead-out conductor 14 are provided. The extraction electrode 16 is electrically connected to the terminal electrode 5a. The coil conductor 13 has a spiral shape in which the coil conductor 13 is wound a plurality of times around the coil shaft CA. The coil shaft CA is a virtual axis extending in the stacking direction of the insulating resin layer 3 (that is, the vertical direction of the laminated common mode coil 1). In one embodiment, the coil shaft CA extends in a direction substantially orthogonal to the insulating layer 11.

An insulating layer 31 is formed on the conductor layer 12. A conductor layer 32 is formed on the insulating layer 31. As shown in FIG. 4, the conductor layer 32 is formed on a spiral-shaped coil conductor 33, a drawer conductor 34 having one end connected to the outer end of the coil conductor 33, and an inner end of the coil conductor 33. An extraction conductor 35 to which one end thereof is connected and an extraction electrode 36 connected to the extraction conductor 34 are provided. The extraction electrode 36 is electrically connected to the terminal electrode 7a. The coil conductor 33 has a spiral shape that is wound a plurality of times around the coil shaft CA.

An insulating layer 41 for an extraction electrode is formed on the conductor layer 32. A lead conductor layer 42 is formed on the lead electrode insulating layer 41. The extraction conductor layer 42 includes an extraction conductor 43a, an extraction conductor 43c, an extraction electrode 44a connected to the extraction conductor 43a, and an extraction electrode 44c connected to the extraction conductor 43c. The extraction electrode 44a is electrically connected to the terminal electrode 5b. The extraction electrode 44c is electrically connected to the terminal electrode 7b.

In order to connect the end of the lead conductor 15 of the conductor layer 12 and the end of the lead conductor 43a, a pad P17 is formed in the insulating layer 11 and a through hole TH37 is formed in the insulating layer 31 for the lead electrode. Through holes TH47 are formed in the insulating layer 41. The through holes TH37 and TH47 are formed by embedding a metal material such as Ag in the through holes formed in the insulating layer 31 and the insulating layer 41 for the extraction electrode. Further, in order to connect the end of the lead conductor 35 of the conductor layer 32 and the end of the lead conductor 43c, a pad P39 is formed in the insulating layer 31 and a through hole TH49 is formed in the insulating layer 41 for the lead electrode. Will be done. Each of these pads and through holes is formed in the same manner as the pads P17 and through holes TH27, respectively.

With the above configuration and arrangement, in the laminated common mode coil 1, two coils are provided between the terminal electrodes 5a and 7a and the terminal electrodes 5b and 7b. That is, the outer end of the coil conductor 13 is electrically connected to the terminal electrode 5a via the extraction conductor 14 and the extraction electrode 16, and the inner end of the coil conductor 13 is the extraction conductor 15, pad P17, through hole TH27, and through. Since it is electrically connected to the terminal electrode 5b via the hole TH37, the through hole TH47, the extraction conductor 43a, and the extraction electrode 44a, the first one including the coil conductor 13 between the terminal electrode 5a and the terminal electrode 5b. Coil is constructed. Further, the outer end of the coil conductor 33 is electrically connected to the terminal electrode 7a via the extraction conductor 34 and the extraction electrode 36, and the inner end of the coil conductor 33 is the extraction conductor 35, the pad P39, the through hole TH49, and the drawer. Since it is electrically connected to the terminal electrode 7b via the conductor 43c and the extraction electrode 44c, a second coil including the coil conductor 33 is formed between the terminal electrode 7a and the terminal electrode 7b. Each of these two coils is a planar coil formed on a plane. Each of these two coils is connected to a signal line in an external circuit, respectively. The laminated common mode coil 1 can also be configured to include three or more coils. When the laminated common mode coil 1 has three coils, the laminated common mode coil 1 is connected to each of the three signal lines in the C-PHY compliant differential transmission circuit established by the MIPI Alliance. It can be used as a mode choke coil.

Next, an example of a method for manufacturing the laminated common mode coil 1 will be described. First, the magnetic substrate 2 is formed from the magnetic material. More specifically, first, a magnetic material such as Ni—Zn ferrite is mixed with an organic binder to prepare a mixture, and this mixture is molded into a sheet to prepare a molded body. Next, this molded body is sintered to obtain a sheet-shaped sintered body. Then, the magnetic substrate 2 is obtained by performing the post-treatment (cutting treatment and polishing treatment) necessary for the sintered body.

Next, a thermosetting resin (for example, epoxy resin) in which filler particles 3a are dispersed is applied to the upper surface of the magnetic substrate 2 by, for example, a spin coating method, and the applied resin is thermally cured to obtain an insulating layer. 11 is obtained. The insulating layer 11 is formed so that its thickness is, for example, about 1.0 to 20 μm. Through holes are formed in the insulating layer 11 at positions corresponding to the through holes.

Next, the conductor layer 12 is formed on the insulating layer 11 by a known method. The conductor layer 12 is formed by, for example, a photolithography method. The conductor layer 12 is formed so that its thickness is, for example, about 5.0 to 20 μm.

Next, the insulating layer 31 is formed on the conductor layer 12 in the same manner as the insulating layer 11. Specifically, the insulating layer 31 is formed by, for example, applying a thermosetting resin (for example, an epoxy resin) in which filler particles 3a are dispersed by, for example, a spin coating method, and then heat-curing the applied resin. Will be done. The insulating layer 31 is formed so that its thickness is, for example, about 1.0 to 20 μm. Through holes are formed in the insulating layer 31 at positions corresponding to the through holes.

Next, the conductor layer 32 is formed on the insulating layer 31 in the same manner as the conductor layer 12. Specifically, the conductor layer 32 is formed by a photolithography method, like the conductor layer 12, for example. The conductor layer 12 is formed so that its thickness is, for example, about 5.0 to 20 μm. The conductor layer 32 is formed so that its thickness is, for example, about 5.0 to 20 μm.

Next, an insulating layer 41 for an extraction electrode is formed on the conductor layer 32 in the same manner as the insulating layer 11 and the insulating layer 31. Specifically, in the lead-out electrode insulating layer 31, for example, a thermosetting resin (for example, an epoxy resin) in which filler particles are dispersed is applied onto the conductor layer 32 by, for example, a spin coating method, and the coating is applied. It is formed by thermosetting the resin. The lead electrode insulating layer 41 is formed so that its thickness is, for example, about 1.0 to 20 μm. Through holes are formed in the lead electrode insulating layer 41 at positions corresponding to the through holes.

Next, the lead conductor layer 42 is formed on the lead electrode insulating layer 41 in the same manner as the conductor layer 12 and the conductor layer 32. Specifically, the lead conductor layer 42 is formed by a photolithography method, like the conductor layer 12 and the conductor layer 32, for example. The lead conductor layer 42 is formed so that its thickness is, for example, about 5.0 to 20 μm.

Next, a thermosetting resin (for example, an epoxy resin) in which the filler particles 4a are dispersed is applied onto the lead conductor layer 42 by, for example, a spin coating method, and the applied resin is thermally cured to obtain a cover resin. Layer 4 is obtained. The cover resin layer 4 is formed so that its thickness is, for example, about 50 to 300 μm. Since the surface of the cover resin layer 4 is polished as necessary, the thickness of the cover resin layer 4 may be thinner in the laminated common mode coil 1 of the finished product.

In the above-mentioned steps, each through hole (TH37 or the like) and each pad (P17 or the like) are also formed together with a pattern corresponding to the conductor layer 12 and the conductor layer 32.

Terminal electrodes 5a, 5b, 7a, 7b are formed by plating, for example, on the side surfaces of the laminated chip thus formed. In this way, the laminated common mode coil 1 is created. The method for producing the laminated common mode coil 1 described above is only an example, and the method for producing the laminated common mode coil to which the present invention can be applied is not limited to the method described above.

In the laminated common mode coil 1 thus obtained, the filling rate of the filler particles 4a in the cover resin layer 4 is higher than the filling rate of the filler particles 3a in the insulating resin layer 3, so that the cover resin layer 4 is less likely to shrink during thermosetting than the insulating resin layer 3. Further, the insulating resin layer 3 is formed thinner than the cover resin layer 4, and since the coil conductor 12 that does not shrink due to heat is embedded in the insulating resin layer 3, it is difficult to shrink during thermosetting. In particular, in the laminated common mode coil 1, since the coil conductor is arranged on almost the entire surface of the insulating resin layer 3, it is difficult to shrink during thermosetting. As described above, in the laminated common mode coil 1, the amount of shrinkage of the insulating resin layer 3 and the cover resin layer 4 at the time of thermosetting is suppressed.

As described above, in one embodiment of the present invention, the filling rate of the filler particles 4a in the cover resin layer 4 is 80% by volume or more. By setting the filling rate of the filler particles 4a in the cover resin layer 4 to 80% or more, the heat shrinkage of the cover resin layer 4 at the time of thermosetting can be sufficiently suppressed.

It was confirmed as follows that heat shrinkage was suppressed when the filling rate of the filler particles 4a in the cover resin layer 4 was 80% by volume or more. First, a laminated body sample was prepared by laminating a magnetic substrate 2, an insulating resin layer 3, and a cover resin layer 4 in this order on a working substrate according to the above-mentioned manufacturing method. In each of these samples, seven types of samples were prepared by changing the filling rate of the filler particles 4a in the cover resin layer 4. Specifically, these seven types of samples have the filling rates of the filler particles 4a in the cover resin layer 4 of 50% by volume, 60% by volume, 70% by volume, 75% by volume, 80% by volume, and 85% by volume, respectively. , 90% by volume. Polyimide was used as the resin material of the insulating resin layer 3, and SiO2 was used as the filler particles 3a. In addition, polyimide was used as the resin material of the cover resin layer 4, and Fe—Si—Cr-based metal magnetic particles were used as the filler particles 4a. The insulating resin layer 3 and the cover resin layer 4 were heated at 200 ° C. for 40 minutes to thermally cure the resin contained in these layers.

For each of these samples, after the cover resin layer 4 was heat-cured, it was visually confirmed whether or not each sample (laminate) was peeled off from the working substrate. Specifically, 10 samples of each type were prepared, and the number of samples from which the laminate was peeled off from the work substrate was counted. The results are shown in Table 1 below.

From the results shown in Table 1, the samples (Samples 1 to 4) in which the filling rate of the filler particles 4a in the cover resin layer 4 was 75% by volume or less were defective because one or more samples were peeled off from the working substrate. I decided. On the other hand, the samples (Samples 5 to 7) in which the filling rate of the filler particles 4a in the cover resin layer 4 was 80% by volume or more were judged to be good because no sample was peeled off from the working substrate. As described above, it was confirmed that the heat shrinkage of the cover resin layer 4 was suppressed when the filling rate of the filler particles 4a in the cover resin layer 4 was 80% by volume or more.

The dimensions, materials, and arrangement of each component described herein are not limited to those expressly described in the embodiments, and each component may be included within the scope of the present invention. Can be transformed to have the dimensions, materials, and arrangement of. In addition, components not explicitly described in the present specification may be added to the described embodiments, or some of the components described in the respective embodiments may be omitted.

1 Laminated common mode coil 2 Magnetic substrate 3 Insulation resin layer 4 Cover resin layer 13, 23 Coil conductor

Claims (13)

A magnetic substrate that having a second surface facing a sintered body of magnetic material on the first surface Ri formed to the first surface,
An insulating resin layer formed only on the first surface of the magnetic substrate and containing the first resin and the first filler particles.
A cover resin layer formed on the insulating resin layer and containing the second resin and the second filler particles,
A coil conductor embedded in the insulating resin layer so as not to come into contact with the magnetic substrate,
With
A laminated coil in which the filling rate of the second filler particles in the cover resin layer is higher than the filling rate of the first filler particles in the insulating resin layer. The second filler particles of the cover resin layer is a magnetic body, the filling factor of the second filler particles of the cover resin layer is 70 vol% or more, the laminated coil according to claim 1 .. The laminated coil according to claim 1 or 2, wherein the first filler particles are spherical. The laminated coil according to claim 1 or 2, wherein the first filler particles are formed in a flat shape. The laminated coil according to any one of claims 1 to 4, wherein the second filler particles are spherical. The laminated coil according to any one of claims 1 to 4, wherein the second filler particles are formed in a flat shape. The laminated coil according to any one of claims 1 to 6, wherein the second filler particles are metallic magnetic particles. A magnetic substrate made of a sintered body of magnetic material and
An insulating resin layer formed on the magnetic substrate and containing the first resin,
A cover resin layer formed on the insulating resin layer and containing a second resin and filler particles,
The coil conductor embedded in the insulating resin layer and
An external electrode provided so as to be in contact with the side surface of the insulating resin layer but not to the upper surface of the insulating resin layer.
With
The insulating resin layer does not contain filler particles and does not contain filler particles.
The filler particles contained in the cover resin layer are metallic magnetic particles.
Multilayer coil. The laminated coil according to claim 8, wherein the filling rate of the filler particles in the cover resin layer is 80% by volume or more. The laminated coil according to claim 8 or 9, wherein the filler particles are spherical. The laminated coil according to claim 8 or 9, wherein the filler particles are formed in a flat shape. With external electrodes
A drawer conductor connecting the external electrode and the coil conductor,
The laminated coil according to any one of claims 1 to 7 , further comprising. The laminated coil according to any one of claims 1 to 12 , which is configured as a common mode coil.

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