JP2014082280A - Laminated coil component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated coil component in which the DC superposition characteristics are enhanced without causing any increase in the DC resistance, and the stress that may be generated in a magnetic material is reduced.SOLUTION: A laminated coil component (11) includes a magnetic material part (2) formed by laminating magnetic material layers, and a conductor part (3) formed by interconnecting a plurality of conductor pattern layers, arranged between the magnetic material layers, in a coil-shape while penetrating the magnetic material layers and by being embedded in the magnetic material part (2). The conductor part (3) consists of a conductor containing silver, the magnetic material part (2) is composed of a sintered ferrite material containing FeO, NiO, ZnO and CuO, the ratio of CuO content of the magnetic material part (2) in a region near the conductor part to CuO content of the magnetic material part (2) in a central region is 0.2-0.5, and at least one cavity is formed in the periphery of the conductor part of the magnetic material part.

Description

  The present invention relates to a laminated coil component, and more specifically, a magnetic body portion formed by laminating magnetic layers and a plurality of conductor pattern layers arranged between the magnetic layers are formed in a coil shape through the magnetic layers. The present invention relates to a laminated coil component having a conductor part that is interconnected and embedded in a magnetic part.

  Conventionally, in a laminated coil part in which a coil conductor part is embedded in a magnetic body part, in order to improve DC superposition characteristics, a non-magnetic material is used around the coil conductor part to form an open magnetic circuit type laminated coil part. Are known. In such a laminated coil component, there is a possibility that cracks may occur inside the laminate due to the difference in the linear expansion coefficient between the magnetic material used and the non-magnetic material.

  In general, cracks in laminated coil components tend to be disliked, and so far, techniques for suppressing the occurrence of cracks have been studied and many reports have been made. For example, Patent Document 1 proposes a nonmagnetic ferrite that can reduce the difference in linear expansion coefficient with the magnetic material used, thereby suppressing the occurrence of cracks in the laminated component. It is said that.

Japanese Patent No. 3251370

  However, in the configuration described in Patent Document 1, there is a possibility that the stress relaxation around the internal electrode and the DC superposition characteristics are insufficient.

  An object of the present invention is to provide a laminated coil component in which the stress around the internal electrode is relieved and the direct current superposition characteristics are improved. Moreover, the further objective of this invention is to provide the manufacturing method of this laminated coil component.

According to one aspect of the present invention, a magnetic part formed by laminating magnetic layers and a plurality of conductor pattern layers disposed between the magnetic layers are interconnected in a coil shape through the magnetic layer, A laminated coil component having a conductor portion embedded in a magnetic body portion,
The conductor portion is made of a conductor containing silver,
The magnetic body portion is made of sintered ferrite material containing Fe, Ni, Zn, Cu,
The ratio of the Cu content (CuO equivalent) in the conductor vicinity region of the magnetic part to the Cu content (CuO equivalent) in the central area of the magnetic part is 0.2 to 0.5, and There is provided a laminated coil component having at least one gap around a conductor portion.

  Conventionally, in a method of manufacturing a laminated coil component, a Ni—Cu—Zn-based ferrite material containing Fe, Ni, Zn, and Cu and having a Cu content (CuO conversion) of 8 mol% or more is usually used. Yes. CuO has a lower melting point than other raw materials of Ni—Cu—Zn ferrite materials, and when the amount of CuO is lowered, the sinterability is lowered. It becomes necessary to raise the temperature to a high temperature, and the green sheet of the Ni—Cu—Zn ferrite material and the conductor paste containing silver cannot be fired simultaneously. Therefore, in order to fire these simultaneously in air, Cu content (CuO conversion) is 8 mol% or more.

  On the other hand, as a result of intensive studies by the present inventors, a green sheet of Ni—Cu—Zn based ferrite material and a conductor paste containing silver are simultaneously fired while reducing the Cu content (CuO conversion). The heat treatment conditions that can be obtained are found (this will be described later), and in the laminated coil component obtained thereby, the Cu content (CuO equivalent) in the central region of the magnetic part (hereinafter referred to as “x” ( The ratio y / x of the Cu content (in terms of CuO) (hereinafter referred to as “y” (weight%) in the present specification) in the region in the vicinity of the conductor portion of the magnetic body portion is 0. It was 5 or less, and it was found that at least one void was formed around the conductor portion of the magnetic body portion.

  According to the laminated coil component of the present invention, since the ratio y / x is 0.2 to 0.5, the Cu component derived from CuO is present in the region near the conductor, and the region near the conductor is sintered. The density and permeability can be made smaller than the central region. Since the magnetic permeability in the vicinity of the conductor portion is smaller, the DC superposition characteristics of the laminated coil component can be improved. Furthermore, for example, when the conductor portion and the magnetic body portion contract due to cooling after firing (or heat dissipation, the same applies hereinafter), the conductor portion having a larger thermal expansion coefficient pulls the magnetic body portion having a smaller thermal expansion coefficient, Cracks occur in the sinterability-decreasing portion, and voids are formed. This gap cuts the magnetic path around the conductor, so that the direct current superimposition characteristics of the laminated coil component can be further improved. In addition to the decrease in the sintered density in the vicinity of the conductor portion, the presence of voids can relieve internal stress in the vicinity of the conductor portion, and the laminated coil component is subjected to a thermal shock test. The change in magnetic characteristics (for example, inductance) can be reduced.

  In the present invention, the “central region of the magnetic body portion” means a region of the magnetic body portion that is located on the inner side of the coil formed by the conductor pattern layer and on and near the central axis of the coil. Specifically, it is represented by a region within 10 μm from the central axis of the coil (for example, a region X shown in FIG. 4A). The “region near the conductor portion of the magnetic body portion” means a region of the magnetic body portion that is close to the interface between the magnetic body portion and the conductor portion, and the inside of the magnetic body from the interface between the magnetic body portion and the conductor portion. It is represented by a region (for example, a region Y shown in FIG. 4A) that is 1 μm or more apart and within 10 μm. The Cu content (CuO equivalent) (% by weight) of the magnetic body part is obtained by measuring the Cu content of a predetermined region of the magnetic body part using wavelength dispersion X-ray analysis (WDX method). It is obtained by converting the Cu content to CuO. The measurement area may vary depending on the analytical instrument to be used. For example, the measurement beam diameter is several tens nm to 1 μm, but is not limited thereto. The measurement location can be set as appropriate within the region to be measured, and the Cu content (CuO equivalent) (% by weight) is obtained as an average value of the measurement values measured at several locations within the region.

  In the present invention, the “periphery of the conductor part of the magnetic part” means a region substantially equivalent to the above-mentioned “region near the conductor part of the magnetic part”, and the magnetic substance from the interface between the magnetic part and the conductor part. It is represented by the area | region to 10 micrometers inside.

  In the laminated coil component of the present invention, it is more preferable that the air gap is formed across the conductor pattern layers adjacent to each other. According to this aspect, the magnetic path around the conductor can be cut reliably, and the DC superposition characteristics of the laminated coil component can be further improved.

  In the laminated coil component of the present invention, the ratio y / x of the Cu content (CuO equivalent) y in the conductor vicinity region of the magnetic part to the Cu content (CuO equivalent) x in the central area of the magnetic part is: More preferably, it is 0.2-0.3. According to this aspect, it is possible to further reduce the change in magnetic characteristics when the laminated coil component is subjected to the thermal shock test.

  In one aspect of the present invention, the Cu content (in terms of CuO) in the central region of the magnetic part is 0.2 to 3% by weight. The higher the Cu content (CuO equivalent) in the central region of the magnetic body part, the higher the ratio y / x tends to be. However, when the Cu content (CuO equivalent) in the central region is 3% by weight or less, The ratio y / x can be 0.5 or less. When the Cu content (in terms of CuO) in the central region of the magnetic part is so small, the saturation magnetic flux density (Bs) of the magnetic part is increased, which contributes to the improvement of the DC superposition characteristics. However, when the Cu content (CuO equivalent) in the central region of the magnetic part is less than 0.2% by weight, the Cu content (CuO equivalent) in the central region of the magnetic part and the Cu (CuO equivalent) in the conductor vicinity region ) The difference between the content and the ratio y / x is outside the appropriate range, and the difference in permeability and crystal grain size between the central region and the conductor vicinity region is small. % Or more is preferable. In the laminated coil component of the present invention, the ratio of the average crystal grain size in the region near the conductor portion of the magnetic body portion to the average crystal grain size in the central region of the magnetic body portion is less than 1, preferably less than 0.8.

As described above, the present inventors set heat treatment conditions that can simultaneously fire a green sheet of Ni—Cu—Zn-based ferrite material and a conductive paste containing silver while lowering the Cu content (CuO equivalent). I found it. Specifically, a ferrite material containing Fe, Ni, Zn, and Cu and having a Cu content (CuO conversion) of 0.3 to 4 mol% is used. By firing in the following atmosphere, while securing a high specific resistance (specifically, a specific resistance of 10 ⁶ Ω · cm or more), the ferrite material is melted at a lower temperature than the case of firing in air (melting point of silver The knowledge that it can sinter at a lower temperature was obtained. The sintered ferrite material thus obtained is a soft magnetic material having a high saturation magnetic flux density (Bs) due to a decrease in Cu content (CuO equivalent). According to the above production method of the present invention, a conductor paste layer containing silver and a ferrite material green sheet containing Fe, Ni, Zn, and Cu and having a Cu content (CuO equivalent) of 0.3 to 4 mol% is provided. Since the laminate including the material is heat-treated in an atmosphere having an oxygen concentration of 0.1% by volume or less, a green paste ferrite material and a conductor paste layer containing silver can be simultaneously fired, and a magnetic material obtained thereby The part has a high specific resistance and a high sintered density in the central region. By carrying out the above manufacturing method, the Cu content (CuO equivalent) in the conductor vicinity region of the magnetic part is set to 0.2 to 0.5 with respect to the Cu content (CuO equivalent) in the central region, and further the magnetic substance At least one air gap can be formed around the conductor part of the part, and the laminated coil component is realized.

  According to the present invention, the Cu content (CuO conversion) in the conductor vicinity region of the magnetic body portion is set to 0.2 to 0.5 with respect to the Cu content (CuO conversion) in the central region, and the conductor portion of the magnetic body portion By forming at least one gap in the periphery, a laminated coil component is provided in which direct current superposition characteristics are improved and internal stress that can be generated in the magnetic body can be reduced. Moreover, according to this invention, the manufacturing method of the said multilayer coil component is also provided.

It is a schematic perspective view of the laminated coil component in one embodiment of this invention. FIG. 2 is a schematic exploded perspective view of the laminated coil component in the embodiment of FIG. 1, with the external electrodes omitted. It is a figure which shows the laminated coil component in the modification of embodiment of FIG. 1, Comprising: It is the schematic sectional drawing seen along the A-A 'line of FIG. It is a figure corresponding to FIG. 3, Comprising: (a) is a figure which shows the center area | region of a magnetic body part, and a conductor part vicinity area | region, (b) is a high Cu content (CuO conversion) area | region and low Cu content. It is a figure which shows the quantity (CuO conversion) area | region exemplarily. FIG. 4 is a view corresponding to FIG. 3 for explaining an “inner peripheral surface of the conductor coil” and an “outer peripheral surface of the conductor coil”. It is a figure which shows the laminated coil components in the modification of embodiment of FIG. 1, Comprising: It is a figure corresponding to Fig.3 (a). 2 is a photograph of a cross section of a laminated coil component obtained in Example 1 and Comparative Example 1.

  The multilayer coil component and the manufacturing method thereof according to the present invention will be described below in detail with reference to the drawings.

  As shown in FIG. 1 and FIG. 3, the laminated coil component 11 of the present embodiment schematically includes a magnetic body portion 2, a coil-shaped conductor portion 3 embedded in the magnetic body portion 2, and the conductor The laminate 3 includes at least one gap 6 around the portion 3, and the external electrodes 5 a and 5 b can be provided so as to cover the outer peripheral end faces of the laminate 1 and are located at both ends of the conductor portion 3. The lead portions 4a and 4b can be connected to the external electrodes 5a and 5b, respectively.

  More specifically, with reference to FIG. 2, the magnetic part 2 is formed by laminating magnetic layers 8a to 8h. In addition, the conductor portion 3 is a coil through which the plurality of conductor pattern layers 9a to 9f disposed between the magnetic layers 8a to 8h pass through the magnetic layers 8b to 8f and pass through the via holes 10a to 10e. Connected to each other. Note that the drawer portions 9a 'and 9f' in FIG. 2 correspond to the drawer portions 4b and 4a in FIG. 1, respectively.

  The magnetic part 2 is made of a sintered ferrite material containing Fe, Ni, Zn, and Cu. The Cu content (CuO equivalent) of the magnetic part 2 will be described later. The conductor portion 3 may be made of a conductor containing silver, but is preferably made of a conductor containing silver as a main component. The external electrodes 5a and 5b are not particularly limited, but are usually made of a conductor containing silver as a main component, and may be plated with nickel and / or tin as necessary.

  However, it should be noted that the configuration, shape, number of turns, arrangement, and the like of the magnetic body portion 2, the conductor portion 3, and the gap 6 of the present embodiment are not limited to the illustrated example.

  The multilayer coil component 11 of this embodiment is manufactured as follows.

  First, a green sheet of a ferrite material containing Fe, Ni, Zn, and Cu and having a Cu content (CuO conversion) of 0.3 to 4 mol% is prepared.

The ferrite material contains Fe, Zn, Ni and Cu as main components, and may further contain an additive component such as Bi as necessary. Usually, the ferrite material can be prepared by mixing and calcining powders of Fe ₂ O ₃ , NiO, ZnO and CuO at a desired ratio as a raw material, but is not limited thereto.

  In this embodiment, Cu content (CuO conversion) in a ferrite material shall be 0.3-4 mol% (main component total reference | standard). When the Cu content (CuO conversion) is set to 0.3 to 4 mol%, the laminate is fired by heat treatment described later, thereby improving the DC superposition characteristics and reducing the change in magnetic characteristics when subjected to the thermal shock test. be able to.

The Fe content (in terms of Fe ₂ O ₃ ) in the ferrite material is preferably 44 to 49.8 mol% (main component total reference). By setting the Fe content (in terms of Fe ₂ O ₃ ) to 44 mol% or higher, a high magnetic permeability can be obtained in the central region of the magnetic body portion, and a large inductance can be obtained. Further, Fe content of _(Fe 2 _{O 3} basis) by less 49.8Mol, it is possible to obtain a high sintering resistance.

  The Zn content (in terms of ZnO) in the ferrite material is preferably 6 to 33 mol% (main component total reference). By setting the Zn content (ZnO conversion) to 6 mol% or more, a high magnetic permeability can be obtained and a large inductance can be obtained. Moreover, by making Zn content (ZnO conversion) 33 mol% or less, the fall of a Curie point can be avoided and the fall of the operating temperature of laminated coil components can be avoided.

  The Ni content (NiO equivalent) in the ferrite material is not particularly limited, and may be the balance of Cu, Fe, and Zn, which are the other main components described above.

Furthermore, Bi content in the ferrite material _(Bi 2 _{O 3} conversion) (added amount), a main component (Fe _(Fe 2 _{O 3} basis), Zn (ZnO basis), Ni (NiO conversion), Cu (CuO conversion) ) Is preferably 0.1 to 1 part by weight per 100 parts by weight in total. By setting the Bi content (in terms of Bi ₂ O ₃ ) to 0.1 to 1 part by weight, low-temperature firing is further promoted and abnormal grain growth can be avoided. If the Bi content (in terms of Bi ₂ O ₃ ) is too high, abnormal grain growth is likely to occur, the specific resistance is reduced at the abnormal grain growth site, and the abnormal grain growth site is formed during the plating process during external electrode formation. Since plating adheres, it is not preferable.

  A green sheet is prepared using the ferrite material prepared as described above. For example, a green sheet may be obtained by mixing / kneading a ferrite material with an organic vehicle containing a binder resin and an organic solvent, and forming the sheet into a sheet shape, but is not limited thereto.

  Separately, a conductor paste containing silver is prepared. A commercially available silver paste containing silver in powder form can be used, but is not limited thereto.

  And the green sheet of ferrite material (corresponding to the magnetic layers 8a to 8h) is laminated via the conductor paste layer containing silver (corresponding to the conductor pattern layers 9a to 9f), and the conductor paste layer becomes the ferrite material. To obtain a laminated body (unfired laminated body, corresponding to laminated body 1) interconnected in a coil shape through via holes (corresponding to via holes 10a to 10e) provided through the green sheet .

  The formation method of a laminated body is not specifically limited, You may form a laminated body using a sheet | seat lamination method, a printing lamination method, etc. In the case of the sheet lamination method, via holes are appropriately provided in the ferrite material green sheet, and the conductor paste layer is printed by printing the conductor paste in a predetermined pattern (filling the via holes when via holes are provided). The green sheet with the conductor paste layer formed thereon is laminated and pressure-bonded, and cut into a predetermined size to obtain a laminate. In the case of the printing lamination method, a laminated body is produced by repeating a process of forming a magnetic layer by printing a magnetic paste made of a ferrite material and a step of printing a conductive paste in a predetermined pattern to form a conductive paste layer. To do. In the step of forming the magnetic layer, via holes are provided at predetermined positions so that the upper and lower conductive paste layers are conductive, and finally the magnetic paste is printed to form a magnetic layer (corresponding to the magnetic layer 8a). The laminate can be obtained by cutting it into predetermined dimensions. The laminated body may be a plurality of laminated bodies produced in a matrix at a time, and then cut into individual pieces by dicing or the like (element separation), but is individually produced in advance. May be.

  Next, the laminated body obtained above is heat-treated in an atmosphere having an oxygen concentration of 0.1% by volume or less to sinter a ferrite paste green sheet and a conductor paste layer containing silver, and each of the magnetic layers 8a. To 8h and conductor pattern layers 9a to 9f. In the laminated body 1 thus obtained, the magnetic layers 8 a to 8 h form the magnetic portion 2, and the conductor pattern layers 9 a to 9 f form the conductor portion 3.

  By heat-treating in an atmosphere having an oxygen concentration of 0.1% by volume or less, the ferrite material can be sintered at a lower temperature than when heat-treated in air. For example, the firing temperature can be 850 to 930 ° C. The present invention is not bound by any theory, but when fired in a low oxygen concentration atmosphere, oxygen defects are formed in the crystal structure, and interdiffusion of Fe, Ni, Cu, Zn present in the crystal is promoted, and the low temperature It is considered that the sinterability can be improved.

In addition, by using a Ni—Zn—Cu based ferrite material having a Cu content (CuO equivalent) of 4 mol% or less, the magnetic part can be fired even in an atmosphere having an oxygen concentration of 0.1 volume% or less. 2 can ensure a high specific resistance. The present invention is not bound by any theory, when fired at a low oxygen concentration atmosphere, Cu ²⁺ by the reducing action of the heat treatment atmosphere is reduced to Cu ⁺ with the specific resistance of the magnetic body portion 2 decreases (impedance decreases It is considered that the formation of Cu ⁺ O due to the reduction of Cu ²⁺ can be suppressed by reducing the Cu content (CuO equivalent), thereby suppressing the decrease in specific resistance. However, the oxygen concentration in the firing atmosphere may be 0.1 volume% or less, but is preferably 0.001 volume% or more in order to ensure the specific resistance of the magnetic body portion 2. Although the present invention is not bound by any theory, if the oxygen concentration is too low, oxygen defects may be generated more than necessary, and the specific resistance of the magnetic body part 2 may be reduced. It is considered that the generation of oxygen defects can be avoided and thereby a high specific resistance can be secured.

  Simultaneously with the firing, at least one void may be formed around the conductor portion of the magnetic body portion. The shape and size of the gap are not particularly limited as long as the magnetic path around the conductor can be cut. The gap cuts the magnetic path around the conductor, thereby improving the direct current superposition characteristics of the laminated coil component. Moreover, the stress around the internal electrode is relieved by the gap, and the thermal shock resistance is also improved.

  The air gap preferably extends along the inner peripheral surface and / or the outer peripheral surface of the conductor coil, and is formed between the conductor pattern layers adjacent to each other. That is, the gap has a length that is at least the distance between the conductor pattern layers along the stacking direction of the laminate, and is adjacent to at least two conductor pattern layers. According to this aspect, the air gap can surely cut the magnetic path passing through the conductor pattern layers adjacent to each other, and the direct current superposition characteristics of the laminated coil component can be further improved.

  Preferably, the thickness of the void is 5 μm or less, more preferably 0.1 to 1.0 μm, and the length (stacking direction of the laminate) is equal to or greater than the distance between the conductor pattern layers, more preferably the entire conductor layer. The horizontal (direction along the inner peripheral surface and / or outer peripheral surface of the conductor coil) is 1/4 or more of the inner peripheral surface or outer peripheral surface, more preferably the entire inner periphery or outer peripheral surface.

  The “inner peripheral surface of the conductor coil” and “outer peripheral surface of the conductor coil” are surfaces including the conductor portion (or inner surface) closest to the central axis of the conductor coil (surface z ′ shown in FIG. 5). , And a surface (surface z ″ shown in FIG. 5) including the conductor portion (or outer surface) farthest from the central axis of the conductor coil.

  For example, the gap uses the fact that the coefficient of thermal expansion of the conductor part is larger than the coefficient of thermal expansion of the magnetic part, and makes the amount of contraction of the conductor part during cooling larger than the amount of contraction of the magnetic part. Can be formed. The method for efficiently forming the voids is not limited, but for example, firing at a low temperature lowers the sintered density of the magnetic body part and lowers the strength of the magnetic body part; increases the thickness of the internal conductor. In the conductor paste, the amount of solvent is increased, and metal (Ag) having a sharp particle size (with a uniform particle size) is used to increase the shrinkage amount by firing. Etc.

  Next, external electrodes 5a and 5b are formed so as to cover both end faces of the laminate 1 obtained above. The external electrodes 5a and 5b are formed by, for example, applying a paste of silver powder together with glass or the like to a predetermined region, and heat-treating the obtained structure at, for example, 800 to 850 ° C. Can be carried out by baking.

  As described above, the laminated coil component 11 of the present embodiment is manufactured. In the laminated coil component 11, as shown in FIG. 4A, the central region X of the magnetic body portion 2 is defined as a region within 10 μm from the central axis (indicated by a dotted line) of the coil formed by the conductor portion 3. The conductor portion vicinity region Y of the magnetic body portion 2 is defined as a region within 1 to 10 μm from the interface between the magnetic body portion 2 and the conductor portion 3 toward the inside of the magnetic body 2. FIG. 4A shows an example in which the conductor vicinity region Y is separated between the conductor pattern layers, but the present embodiment is not limited to this, and may overlap between the conductor pattern layers.

  The Cu content (CuO equivalent) y in the conductor vicinity region Y of the magnetic part 2 is lower than the Cu content (CuO equivalent) x in the central area X of the magnetic part 2. Although the present invention is not limited by any theory, a ferrite material having a Cu content (CuO conversion) of 0.3 to 4 mol% and a conductor paste containing silver in an atmosphere having an oxygen concentration of 0.1 vol% or less. When co-firing, in this firing process, the conductor portion derived from the conductor paste absorbs Cu from the ferrite material, and therefore, the Cu content (converted to CuO) in the conductor portion vicinity region Y is considered to decrease. That is, as exemplarily shown in FIG. 4B, in the magnetic body portion 2, a low Cu content (CuO equivalent) region Y ′ (including the conductor vicinity region Y) is formed around the conductor portion 3. Thus, the other bulk regions (excluding the region adjacent to the outer surface of the laminate 1) have a relatively high Cu content (CuO conversion) and a high Cu content (CuO conversion) region X ′. It becomes. The Cu content (CuO equivalent) in the central region X of the magnetic part 2 can be understood as representing the Cu content (CuO equivalent) in the high Cu content (CuO equivalent) region X ′. The Cu content (CuO equivalent) in the conductor portion vicinity region Y can be understood as representing the Cu content (CuO equivalent) in the low Cu content (CuO equivalent) region Y ′. As shown in FIG. 4B, the low Cu content (CuO equivalent) region Y ′ is preferably formed without gaps between the conductor pattern layers, but the present invention is not limited to this.

  In the laminated coil component 11, the ratio y / x of the Cu content (CuO equivalent) is 0.2 to 0.5, preferably 0.2 to 0.3. The reference Cu content (CuO equivalent) x depends on the Cu content (CuO equivalent) of the ferrite material used, but is, for example, 0.2 to 3% by weight. Thus, the lower Cu content (CuO equivalent) in the conductor portion vicinity region Y of the magnetic body portion 2 reduces the sinterability of the conductor portion vicinity region Y, suppresses particle growth, and sintering. The density is lowered, and as a result, the permeability is also lowered. On the other hand, in the central region X of the magnetic body portion 2, since the Cu content (CuO conversion) is relatively high, the sinterability is high, the particle growth is sufficiently promoted, and the sintering density is increased. As a result, the magnetic permeability is also increased. In other words, in the multilayer coil component 11 of the present embodiment, in the magnetic body portion 2 in the conductor portion vicinity region Y, it is possible to simultaneously achieve low permeability and low sintering density. In addition, by making the sinterability of the region Y near the conductor portion of the magnetic body portion 2 lower than the sinterability of the central region X of the magnetic body portion 2, the portion where the air gap is formed is changed to the conductor of the magnetic body portion 2. It can be a part periphery. By forming the air gap around the conductor part of the magnetic body part 2, it becomes possible to cut the magnetic path around the conductor part. In addition, the ratio of the average crystal grain size in the vicinity of the conductor portion of the magnetic body portion to the average crystal grain size in the central region of the magnetic body portion of the laminated coil component 11 is less than 1, preferably less than 0.8.

  When a current is passed through the conductor portion 3 using such a laminated coil component 11, the magnetic flux formed around the conductor portion 3 is likely to pass through a region having a higher magnetic permeability, so a low Cu content (CuO equivalent) ) Higher Cu content (CuO equivalent) region X ′ (high magnetic permeability region) located outside the region Y ′ (low magnetic permeability region including the conductor vicinity region Y) , Including the central region X), and the magnetic path becomes longer as compared with the case where the entire magnetic body portion 2 has a high magnetic permeability. As the magnetic path becomes longer, a stable inductance can be obtained over a larger DC current region. That is, it is possible to obtain improved direct current superposition characteristics. In addition, since the magnetic path is cut by the air gap 6, the direct current superposition characteristics of the laminated coil component 11 of the present embodiment are further improved.

  Moreover, although this laminated coil component 11 differs in the thermal expansion coefficient (especially linear expansion coefficient) by the magnetic body part 2 which consists of a sintered ferrite material, and the conductor part 3 which consists of a conductor containing silver, Among them, in addition to the low sintered density in the conductor vicinity region Y, since there is a void around the conductor portion 3 of the magnetic body portion 2, it is generated in the magnetic body portion 2 due to a cooling process after heat treatment (firing). The internal stress (or stress strain) that can be reduced can be reduced or reduced. Therefore, when the laminated coil component 11 is subjected to a thermal shock test, or when the laminated coil component 11 is used (reflow processing when mounted on a substrate or actually used by a user), it is exposed to a sudden temperature change or external stress. When the load is applied, the fluctuation of the internal stress can be reduced by the conductor vicinity region Y (region where the sintered density is low) and the gap 6, thereby reducing the change in magnetic characteristics such as inductance and impedance. be able to.

  Although one embodiment of the present invention has been described above, the present embodiment can be variously modified. For example, as shown in FIG. 6, a nonmagnetic layer 12 may be provided so as to cross the magnetic path, and an open magnetic path type may be used. The non-magnetic layer 12 is made of a material having a thermal expansion coefficient similar to that of the magnetic unit 2 (magnetic layers 8a to 8h), for example, Ni of the Ni—Cu—Zn-based ferrite material of the magnetic unit 2 is entirely contained in Zn. Substituted Zn-Cu ferrite materials can be used. As described above, in addition to forming a gap around the conductor portion, the open magnetic circuit type laminated coil component by inserting the non-magnetic material layer can further improve the DC superposition characteristics.

Example 1
As raw materials for the ferrite material, Fe ₂ O ₃ (49 mol%), ZnO (20 mol%), NiO (30 mol%), and CuO (1 mol%) powders were prepared. Bi ₂ O ₃ was weighed and added at 0.25 parts by weight with respect to 100 parts by weight in total. Next, the powder was put into a pot mill made of vinyl chloride together with pure water and PSZ (Partial Stabilized Zirconia) balls, and was sufficiently mixed and pulverized in a wet manner. The pulverized product was evaporated to dryness and calcined at a temperature of 750 ° C. for 2 hours. The calcined material obtained in this way is put into a pot mill made of vinyl chloride together with ethanol and PSZ balls, sufficiently mixed and pulverized, further added with polyvinyl butyral binder (organic binder), mixed, and a slurry containing a ferrite material (Ceramic slurry) was obtained.

  Next, using the doctor blade method, the ferrite material slurry obtained above was formed into a sheet having a thickness of 25 μm. The obtained molded body was punched into a size of 50 mm in length and 50 mm in width to produce a green sheet of ferrite material.

  Separately, a conductor paste containing silver powder, varnish and organic solvent was prepared. After forming a via hole at a predetermined position of the green sheet produced above using a laser processing machine, this conductor paste is screen printed on the surface of the green sheet while filling the via hole formed in the green sheet. A conductor paste layer was formed.

  Next, after appropriately laminating a green sheet of ferrite material in which a conductor paste layer is formed in a predetermined pattern, these are sandwiched between green sheets of ferrite material in which a conductor paste layer is not formed, and 100 MPa at a temperature of 60 ° C. A pressure-bonding block was produced by pressure bonding under the pressure of And this press-bonded block was cut into a predetermined size to produce a laminate.

The laminate obtained above was sufficiently degreased by heating to 400 ° C. in the atmosphere. Next, the laminate was put into a firing furnace in which the oxygen concentration was controlled to 0.1 volume% with a mixed gas of N ₂ —O ₂ , heated to 900 ° C., and held for 2 hours for heat treatment (firing). .

  Then, after preparing a conductive paste for external electrodes containing silver powder, glass frit, varnish and organic solvent, the conductive paste for external electrodes was applied to both ends of the heat-treated laminate and dried, Baking was performed at 750 ° C., and Ni and Sn plating were sequentially performed by electrolytic plating to form external electrodes.

  Thus, a laminated coil component was produced. The outer diameter of the laminated coil component was 2.0 mm in length, 1.2 mm in width, and 1.0 mm in thickness, and the number of turns of the conductor (coil) was 10.5.

  When the longitudinal direction of the obtained laminated coil component was set up and contained in a non-shrinkable resin and polished to a position where the inside of the conductor was exposed, the cross section was observed. As shown in the photograph of FIG. A gap between adjacent conductor pattern layers was confirmed around the conductor portion.

(Comparative Example 1)
As raw materials for the ferrite material, Fe ₂ O ₃ (49 mol%), ZnO (20 mol%), NiO (26 mol%), and CuO (6 mol%) powders were prepared. Created a part.

(Evaluation)
The laminated coil parts obtained in Example 1 and Comparative Example 1 were evaluated for DC superposition characteristics.

-DC superimposition characteristic In accordance with JIS standard (C2560-2), 30 laminated coil parts obtained in Example 1 and Comparative Example 1 were used to superimpose a 1 A direct current on the laminated coil parts. The inductance L of the laminated coil component was measured at a frequency of 1 MHz before applying current (initially), when applying 1A, and after applying current. Average values of 30 samples were obtained, and the results are shown in Table 1.

  From Table 1, the laminated coil part of Example 1 having a gap around the conductor part of the magnetic part has a lower inductance reduction rate when applying a 1A DC current than the laminated coil part of Comparative Example 1 having no gap. It was confirmed. It was also confirmed that the inductance return rate after application of current was superior to that of Comparative Example 1.

  The laminated coil component obtained by the present invention can be used in a wide variety of applications, for example, as an inductor or a transformer of a high frequency circuit and a power supply circuit.

DESCRIPTION OF SYMBOLS 1 Laminated body 2 Magnetic body part 3 Conductor part 4a, 4b Lead part 5a, 5b External electrode 6 Space | gap 8a-8h Magnetic body layer 9a-9f Conductor pattern layer 9a ', 9f' Lead part 10a-10e Via 11 Laminated coil components 12 Non-magnetic layer X Central region Y Conductor region nearby X 'High Cu content region (CuO equivalent)
Y 'Low Cu content region (CuO conversion)

Claims (4)

A magnetic part formed by laminating magnetic layers, and a conductor part formed by embedding a plurality of conductor pattern layers arranged between the magnetic layers through the magnetic layer in a coil shape and embedded in the magnetic part A laminated coil component having
The conductor portion is made of a conductor containing silver,
The magnetic body portion is made of sintered ferrite material containing Fe, Ni, Zn, Cu,
The ratio of the Cu content (CuO equivalent) in the conductor vicinity region of the magnetic part to the Cu content (CuO equivalent) in the central area of the magnetic part is 0.2 to 0.5, and A laminated coil component having at least one gap around a conductor portion.   The multilayer coil component according to claim 1, wherein the air gap is formed across conductor pattern layers adjacent to each other.   The ratio of the Cu content (CuO equivalent) in the conductor vicinity region of the magnetic part to the Cu content (CuO equivalent) in the central area of the magnetic part is 0.2 to 0.3. The laminated coil component according to claim 2.   The multilayer coil component according to any one of claims 1 to 3, wherein a Cu content (CuO equivalent) in a central region of the magnetic part is 0.2 to 3% by weight.