Patent Application
20240177923
This application claims benefit of priority to Japanese Patent Application No. 2022-189201, filed Nov. 28, 2022, the entire content of which is incorporated herein by reference.
The present disclosure relates to a multilayer coil component and a method of manufacturing a multilayer coil component.
Japanese Unexamined Patent Application Publication No. 2004-207608 discloses a multilayer electronic component manufactured by forming recessed grooves in green sheets, applying a plurality of electrically conductive paste portions to the recessed grooves in a matrix manner, laminating the plurality of green sheets together so as to form a plurality of coils therein, cutting and firing the laminated green sheets, and providing terminal electrodes at the two end portions of each of the obtained element bodies. In a cross-sectional shape of a coil conductor that is made of the electrically conductive paste and that has undergone firing, the coil conductor partially overlaps the two sides of the recessed grooves, and the aspect ratio t/w between a thickness t and a width w of the coil conductor in the cross-section is 0.7 or more.
However, the multilayer coil component described in Japanese Unexamined Patent Application Publication No. 2004-207608 has room for improvement in terms of further increasing an impedance that can be obtained.
Accordingly, the present disclosure provides a multilayer coil component and a method of manufacturing a multilayer coil component capable of increasing an impedance that can be obtained.
A multilayer coil component of the present disclosure includes a multilayer body that includes a plurality of insulating layers and a plurality of coil conductors laminated together in a lamination direction and that is provided with a coil formed inside the multilayer body and an outer electrode that is provided at a surface of the multilayer body and electrically connected to the coil. The multilayer body has a first end surface and a second end surface that face each other in a length direction, a first main surface and a second main surface that face each other in a height direction, which is perpendicular to the length direction, and a first side surface and a second side surface that face each other in a width direction, which is perpendicular to the length direction and the height direction. The outer electrode includes a first outer electrode extending from at least a portion of the first end surface of the multilayer body to a portion of the first main surface and a second outer electrode extending from at least a portion of the second end surface of the multilayer body to a portion of the first main surface. The insulating layers have a magnetic phase and a non-magnetic phase and have a first region that is located between the coil conductors adjacent to each other in the lamination direction and a second region that is a region inside the coil excluding the first region. When a total amount of Si and Fe is 100% by weight, an average Fe content in the first region is greater than an average Fe content in the second region, and a difference between the average Fe contents is 1.7% by weight or more.
A method of manufacturing a multilayer coil component of the present disclosure includes producing coil sheets on which conductor patterns for coil conductors are formed by applying an electrically conductive paste to green sheets, producing a chip by laminating the coil sheets in a lamination direction, and firing the chip so as to produce a multilayer body that is provided with a coil formed inside the multilayer body, the coil including a plurality of coil conductors electrically connected to each other. The green sheets contain a magnetic material and a non-magnetic material. The firing includes pushing out the non-magnetic material from a first region that is located between the coil conductors adjacent to each other in the lamination direction toward a second region that is a region inside the coil excluding the first region. An absolute value of a shrinkage percentage of the electrically conductive paste during firing is smaller than an absolute value of a shrinkage percentage of each of the green sheets during firing, and a difference between the absolute values is 1.2% or more.
The present disclosure can provide a multilayer coil component and a method of manufacturing a multilayer coil component capable of increasing an impedance that can be obtained.
A multilayer coil component of the present disclosure will be described below.
However, the present disclosure is not limited to the following configurations and aspects and can be applied with appropriate modifications within a range that does not alter the gist of the present disclosure. Note that combinations of two or more individual preferable configurations and aspects of the present disclosure that will be described below are also included in the present disclosure.
A multilayer coil component 1 illustrated in
In the multilayer coil component and the multilayer body in the present specification, a length direction, a height direction, and a width direction respectively correspond to the x direction, the y direction, and the z direction in
The length direction (the x direction) is a direction parallel to the lamination direction.
As illustrated in
Although not illustrated in
A first outer electrode and a second outer electrode are each an outer electrode that extends along a main surface of a multilayer body from at least a portion of an end surface of the multilayer body.
In the multilayer coil component 1 illustrated in
The first outer electrode 21 covers a region of the first end surface 11, the region including the ridge portion that intersects the first main surface 13.
Note that, in
As illustrated in
In the multilayer coil component 1 illustrated in
Similar to the first outer electrode 21, the second outer electrode 22 covers a region of the second end surface 12, the region including the ridge portion that intersects the first main surface 13.
Similar to the first outer electrode 21, the shape of the second outer electrode 22 is not particularly limited as long as the second outer electrode 22 covers a portion of the second end surface 12 of the multilayer body 10. For example, the second outer electrode 22 at the second end surface 12 of the multilayer body 10 may have an arch-like shape that increases in height from the end portions toward a center portion thereof. In addition, the shape of the second outer electrode 22 is not particularly limited as long as the second outer electrode 22 covers a portion of the first main surface 13 of the multilayer body 10. For example, the second outer electrode 22 at the first main surface 13 of the multilayer body 10 may have an arch-like shape that increases in length from the end portions toward the center portion thereof.
Similar to the first outer electrode 21, the second outer electrode 22 may be disposed so as to further extend from the second end surface 12 and the first main surface 13 and cover a portion of the first side surface 15 and a portion of the second side surface 16. In this case, it is preferable that a portion of the second outer electrode 22 that covers the first side surface 15 and a portion of the second outer electrode 22 that covers a portion of the second side surface 16 be formed so as to be inclined with respect to the ridge portion that intersects the second end surface 12 and the ridge portion that intersects the first main surface 13. Note that the second outer electrode 22 does not need to be disposed so as to cover a portion of the first side surface 15 and a portion of the second side surface 16.
Since the first outer electrode 21 and the second outer electrode 22 are arranged in the manner described above, when the multilayer coil component 1 is mounted onto a substrate, the first main surface 13 of the multilayer body 10 serves as a mounting surface.
In addition, unlike the structure illustrated in
Furthermore, the second outer electrode may cover the entire second end surface of the multilayer body and may extend from the second end surface so as to cover a portion of the first main surface, a portion of the second main surface, a portion of the first side surface, and a portion of the second side surface.
In this case, one of the first main surface, the second main surface, the first side surface, and the second side surface of the multilayer body serves as the mounting surface.
Although the size of the multilayer coil component of the present disclosure is not particularly limited, it is preferable that the size of the multilayer coil component be 0603 size, 0402 size, or 1005 size.
Next, an example of the coil that is built in the multilayer body, which is included in the multilayer coil component, will be described.
The coil is formed as a result of the plurality of coil conductors that are laminated in the lamination direction together with the insulating layers being electrically connected to one another.
As illustrated in
The multilayer body 10 has a region in which the coil conductors 32 are arranged and a region in which a first connection conductor 41 or a second connection conductor 42 is disposed. The lamination direction in the multilayer body 10 and the axial direction of the coil 30 (the direction in which a coil axis A extends in
As described above, the multilayer body 10 has a configuration in which the coil 30, which is formed of the plurality of coil conductors 32, and the first and second connection conductors 41 and 42, each of which is electrically connected to the coil 30, are built in an insulator 50 that includes the plurality of insulating layers.
The insulating layers have (the insulator 50 has) a magnetic phase and a non-magnetic phase. As a result, the Fe content of the insulating layers in regions between the adjacent coil conductors 32 can be set to be different from that in the other regions.
More specifically, the insulating layers have (the insulator 50 has) a plurality of first regions 51 each of which is a region that is located between two of the coil conductors 32 that are adjacent to each other in the lamination direction in the multilayer body 10 and a second region 52 that is a region inside the coil 30 excluding the first regions 51. When the total amount of Si and Fe is 100% by weight, the average Fe content in the first regions 51 is greater than the average Fe content in the second region 52, and the difference between these average Fe contents is 1.7% by weight or more.
As a result, the magnetic permeability in the first regions 51 is relatively larger than that in the second region 52, and this can increase an impedance that can be obtained.
Note that the second region 52 is a region included in a magnetic core portion inside the coil conductors 32.
If the difference between the average Fe contents is less than 1.7% by weight, there may be a case where an impedance that can be obtained cannot be increased.
It is preferable that the difference between the average Fe contents be 2% by weight or more, and more preferably, 4% by weight or more. When the difference between the average Fe contents is 2% by weight or more, the magnetic permeability in the first regions 51 is 1.15 times or more that in the second region 52. When the difference between the average Fe contents is 4% by weight or more, the magnetic permeability in the first regions 51 is 1.3 times or more that in the second region 52.
Although the upper limit of the difference between the average Fe contents is not particularly limited, it is preferable that the upper limit be 10% by weight or less, and more preferably, 7% by weight or less.
In the insulating layers (the insulator 50), there is a third region 53 that is defined, separately from the second region 52, by the first outer electrode 21, the second outer electrode 22, and the internal conductors including the coil conductors 32, the first connection conductor 41, and the like. When the average Fe content in the first regions 51 is greater than the average Fe content in the second region 52 and the difference between these average Fe contents is 1.7% by weight or more, with the total amount of Si and Fe being 100% by weight, the average Fe content in the third region 53 can be set to be less than the average Fe content in the first regions 51. As a result, the dielectric constant of the third region 53 can be reduced, and the stray capacitance between the outer electrodes and the internal conductors can be reduced.
More specifically, for example, when the total amount of Si and Fe is 100% by weight, the average Fe content in the third region 53 can be set to be less than the average Fe content in the first regions 51, and the difference between these average Fe contents can be set to 1.7% by weight or more.
It is preferable that the difference between the average Fe content in the third region 53 and the average Fe content in the first regions 51 be 2% by weight or more, and more preferably, 4% by weight or more. When the difference between the average Fe contents is 2% by weight or more, the magnetic permeability kin the first regions 51 is 1.15 times or more that in the third region 53. When the difference between the average Fe contents is 4% by weight or more, the magnetic permeability in the first regions 51 is 1.3 times or more that in the third region 53.
It is preferable that the upper limit of the difference between the average Fe content in the third region 53 and the average Fe content in the first regions 51 be 10% by weight or less, and more preferably, 7% by weight or less.
In addition, when the total amount of Si and Fe is 100% by weight, it is preferable that the average Si content in the first regions 51 be less than the average Si content in the second region 52, and it is preferable that the difference between these average Si contents be 1.7% by weight or more.
It is preferable that the difference between the average Si contents be 1.8% by weight or more, and more preferably, 3.6% by weight or more.
Although the upper limit of the difference between the average Si contents is not particularly limited, it is preferable that the upper limit be 10% by weight or less, and more preferably, 9% by weight or less.
In addition, when the total amount of Si and Fe is 100% by weight, it is preferable that the average Si content in the third region 53 be greater than the average Si content in the first regions 51, and it is preferable that the difference between these average Si contents be 1.7% by weight or more.
It is preferable that the difference between the average Si content in the third region 53 and the average Si content in the first regions 51 be 1.8% by weight or more, and more preferably, 3.6% by weight or more.
It is preferable that the upper limit of the difference between the average Si content in the third region 53 and the average Si content in the first regions 51 be 10% by weight or less, and more preferably, 9% by weight or less.
The average Fe contents and the average Si contents can each be determined by performing, for example, an elementary analysis using the energy dispersive X-ray spectrometry (EDX) on a cross section of the multilayer coil component and are calculated as the average value of a plurality of measurement points (e.g., three points) in each region.
A specific measurement method will be described in the Examples section.
The magnetic phase is a phase containing a magnetic material, and it is preferable that the magnetic phase contain at least Fe, Ni, Zn, and Cu. The magnetic phase may be a phase composed of only a magnetic material.
The magnetic phase may further contain Co, Bi, Sn, Mn, and so forth.
It is preferable that the magnetic material be a Ni—Cu—Zn-based ferrite material, and it is preferable that the magnetic phase be composed of the Ni—Cu—Zn-based ferrite material. As a result of the magnetic phase being composed of the Ni—Cu—Zn-based ferrite material, the inductance of the multilayer coil component is increased.
The Ni—Cu—Zn-based ferrite material may further contain additives such as Co, Bi, Sn, and Mn and incidental impurities.
In addition, the magnetic phase is a phase containing Fe, Ni, Zn, and Cu when an elementary analysis is performed thereon. Furthermore, the magnetic phase may be a phase that further contains Co, Bi, Sn, Mn, and so forth when an elementary analysis is performed thereon.
It is preferable that the magnetic phase contain 40 mol % or more and 49.5 mol % or less (i.e., from 40 mol % to 49.5 mol %) of Fe in terms of Fe2O3, 2 mol % or more and 35 mol % or less (i.e., from 2 mol % to 35 mol %) of Zn in terms of ZnO, 6 mol % or more and 13 mol % or less (i.e., from 6 mol % to 13 mol %) of Cu in terms of CuO, and 10 mol % or more and 45 mol % or less (i.e., from 10 mol % to 45 mol %) of Ni in terms of NiO.
The non-magnetic phase is a phase containing a non-magnetic material, and it is preferable that the non-magnetic phase contain at least Si. The non-magnetic phase may be a phase composed of only a non-magnetic material.
Examples of the non-magnetic material of the non-magnetic phase include a glass material, forsterite (2MgO·SiO2), and willemite [aZnO·SiO2 (where a is 1.8 or more and 2.2 or less (i.e., from 1.8 to 2.2))].
Note that, in the present specification, the phrase “non-magnetic phase containing at least Si” may be formed of only a phase that contains Si or may be formed of a phase that contains Si and a phase that does not contain Si. An example of the phase that does not contain Si may be a crystal phase that does not contain Si.
It is preferable that the non-magnetic phase contain a glass material. In the case where the non-magnetic phase contains a glass material, the Fe content in the first regions 51 and the Fe content in the second region 52 can be set to be different from each other as mentioned above.
It is preferable that borosilicate glass be used as the glass material.
It is preferable that the borosilicate glass contain 70% by weight or more and 85% by weight or less (i.e., from 70% by weight to 85% by weight) of Si in terms of SiO2, 10% by weight or more and 25% by weight or less (i.e., from 10% by weight to 25% by weight) of B in terms of B2O3, 0.5% by weight or more and 5% by weight or less (i.e., from 0.5% by weight to 5% by weight) of an alkali metal Ain terms of A2O, and 0% by weight or more and 5% by weight or less (i.e., from 0% by weight to 5% by weight) of Al in terms of Al2·O3. Examples of the alkali metal A include K and Na.
The non-magnetic phase may further contain forsterite (2MgO·SiO2), a quartz (SiO2), or the like as a filler.
The magnetic phase and the non-magnetic phase can be distinguished from each other as follows. First, a cross section of the multilayer body of the multilayer coil component along the lamination direction is exposed by grinding the multilayer body, and after that, elemental mapping is performed on the multilayer body by performing scanning transmission electron microscopy-energy dispersive X-ray analysis (STEM-EDX). Then, the magnetic phase and the non-magnetic phase are distinguished from each other by regarding a region in which an Fe element, a Ni element, a Zn element, and a Cu element are present as the magnetic phase and by regarding regions other than the magnetic phase as the non-magnetic phase.
Note that the cross section along the lamination direction is a cross section such as that illustrated in
It is preferable that the proportion of the volume of forsterite relative to the total volume of the non-magnetic phase be 1.5% by volume or more and 20% by volume or less (i.e., from 1.5% by volume to 20% by volume).
The proportion of the volume of forsterite contained in the non-magnetic phase can be determined by distinguishing a region in which a Mg element, which is an element contained in forsterite, is present as a region in which forsterite is present and measuring the proportion of the area of the region in which forsterite is present relative to the area of the non-magnetic phase.
When 1.5% by volume or more and 20% by volume or less (i.e., from 1.5% by volume to 20% by volume) of the non-magnetic phase consists of forsterite, the strength of the multilayer body is improved.
As illustrated in
The coil 30 includes a coil conductor 32a, a coil conductor 32b, a coil conductor 32c, and a coil conductor 32d as the coil conductors 32 illustrated in
The coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d are arranged on a main surface of the insulating layer 31a, a main surface of the insulating layer 31b, a main surface of the insulating layer 31c, and a main surface of the insulating layer 31d, respectively.
The coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d each have a length equal to the length of a ¾ turn of the coil 30. In other words, the number of the coil conductors 32 laminated so as to form three turns of the coil 30 is four. In the multilayer body 10, the coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d are repeatedly laminated as a single unit (equivalent to three turns).
The coil conductor 32a includes a line portion 36a and land portions 37a that are positioned at the end portions of the line portion 36a. The coil conductor 32b includes a line portion 36b and land portions 37b that are positioned at the end portions of the line portion 36b. The coil conductor 32c includes a line portion 36c and land portions 37c that are positioned at the end portions of the line portion 36c. The coil conductor 32d includes a line portion 36d and land portions 37d that are positioned at the end portions of the line portion 36d.
A via conductor 33a, a via conductor 33b, a via conductor 33c, and a via conductor 33d are arranged in such a manner as to extend through the insulating layer 31a, the insulating layer 31b, the insulating layer 31c, and the insulating layer 31d, respectively, in the lamination direction.
The insulating layer 31a provided with the coil conductor 32a and the via conductor 33a, the insulating layer 31b provided with the coil conductor 32b and the via conductor 33b, the insulating layer 31c provided with the coil conductor 32c and the via conductor 33c, and the insulating layer 31d provided with the coil conductor 32d and the via conductor 33d are repeatedly laminated as a single unit (each portion surrounded by a dotted line in
The coil 30 that has a solenoid shape and that is built in the multilayer body 10 is configured in the manner described above.
When viewed in plan view in the lamination direction, the coil 30 formed of the coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d may have a circular shape or may have a polygonal shape. In the case where the coil 30 has a polygonal shape when viewed in plan view in the lamination direction, the coil diameter of the coil 30 is the diameter of a circle that is equivalent to the area of the polygonal shape, and the coil axis of the coil 30 is an axis that extends in the lamination direction through the center of the polygonal shape.
Via conductors 33p are arranged such that each of them extends through a corresponding one of the insulating layer 35a1, the insulating layer 35a2, the insulating layer 35a3, and the insulating layer 35a4 in the lamination direction. Land portions that are connected to the via conductors 33p may be arranged on main surfaces of the insulating layers 35a1, 35a2, 35a3, and 35a4.
The insulating layer 35a1 provided with one of the via conductors 33p, the insulating layer 35a2 provided with one of the via conductors 33p, the insulating layer 35a3 provided with one of the via conductors 33p, and the insulating layer 35a4 provided with one of the via conductors 33p are laminated together so as to overlap the insulating layer 31a provided with the coil conductor 32a and the via conductor 33a. Consequently, the via conductors 33p are connected to one another and form the first connection conductor 41, and the first connection conductor 41 is exposed at the first end surface 11. As a result, the first outer electrode 21 and the coil 30 (the coil conductor 32a) are connected to each other by the first connection conductor 41.
It is preferable that the first connection conductor 41 extend linearly and connect the first outer electrode 21 and the coil 30 to each other. The phrase “the first connection conductor 41 extends linearly and connects the first outer electrode 21 and the coil 30 to each other” refers to the case where the via conductors 33p forming the first connection conductor 41 overlap one another when viewed in plan view in the lamination direction, and the via conductors 33p do not need to be aligned exactly in a straight line.
Via conductors 33q are arranged such that each of them extends through a corresponding one of the insulating layer 35b1, the insulating layer 35b2, the insulating layer 35b3, and the insulating layer 35b4 in the lamination direction. Land portions that are connected to the via conductors 33q may be arranged on main surfaces of the insulating layers 35b1, 35b2, 35b3, and 35b4.
The insulating layer 35b1 provided with one of the via conductors 33q, the insulating layer 35b2 provided with one of the via conductors 33q, the insulating layer 35b3 provided with one of the via conductors 33q, and the insulating layer 35b4 provided with one of the via conductors 33q are laminated together so as to overlap the insulating layer 31d provided with the coil conductor 32d and the via conductor 33d. Consequently, the via conductors 33q are connected to one another and form the second connection conductor 42, and the second connection conductor 42 is exposed at the second end surface 12. As a result, the second outer electrode 22 and the coil 30 (the coil conductor 32d) are connected to each other by the second connection conductor 42.
It is preferable that the second connection conductor 42 extend linearly and connect the second outer electrode 22 and the coil 30 to each other. The phrase “the second connection conductor 42 extends linearly and connects the second outer electrode 22 and the coil 30 to each other” refers to the case where the via conductors 33q forming the second connection conductor 42 overlap one another when viewed in plan view in the lamination direction, and the via conductors 33q do not need to be aligned exactly in a straight line.
Note that, in the case where the land portions are connected to the via conductors 33p forming the first connection conductor 41 and the via conductors 33q forming the second connection conductor 42, the shape of the first connection conductor 41 and the shape of the second connection conductor 42 each refer to a shape excluding the land portions.
Although
For example, the number of the coil conductors laminated so as to form a single turn of the coil may be two, that is, the repeated shape may be the shape of a ½ turn.
In addition, although the number of the coil conductors 32 laminated, that is, the total number of the coil conductors 32 that are included in the multilayer body 10 and that are laminated together is not particularly limited, it is preferably 40 or more and 60 or less (i.e., from 40 to 60).
In this case, the stress applied to the insulating layers can be increased, and thus, the difference between the average Fe contents mentioned above can be increased.
From such a standpoint, in the case where the number of the coil conductors 32 laminated so as to form three turns of the coil 30 is four, it is preferable that the number of turns of the coil be 30 turns or more and 45 turns or less (i.e., from 30 turns to 45 turns).
It is preferable that the coil conductors forming the coil overlap one another when viewed in plan view in the lamination direction. In addition, it is preferable that the shape of the coil be a circular shape when viewed in plan view in the lamination direction. Note that, in the case where the coil includes the land portions, the shape of the coil refers to a shape excluding the land portions (i.e., the shape of the line portions).
In addition, in the case where the land portions are connected to the via conductors that form the connection conductors, the shape of the connection conductors refers to a shape excluding the land portions (i.e., the shape of the via conductors).
Note that the coil conductors illustrated in
In addition, the repeated shape of the coil conductors does not need to be the shape of a ¾ turn and may be the shape of a ½ turn.
The first outer electrode and the second outer electrode may each have a single-layer structure or may each have a multilayer structure.
When the first outer electrode and the second outer electrode each have a single-layer structure, examples of a material of each of these outer electrodes include silver, gold, copper, palladium, nickel, aluminum, and an alloy containing at least one of these metals.
When the first outer electrode and the second outer electrode each have a multilayer structure, each of these outer electrodes may include, for example, a base electrode layer containing silver, a nickel coating, and a tin coating arranged in this order starting from the side on which a surface of the multilayer body is present.
In the multilayer coil component having a configuration such as that illustrated in
It is further preferable that the number of turns of the coil be 33 turns or more and 42 turns or less (i.e., from 33 turns to 42 turns). When the number of turns of the coil is within such a range, the total electrostatic capacitance between the coil conductors can be reduced, and thus, a transmission coefficient S21 can be set to be within a favorable range.
In addition, it is preferable that the coil length be 0.49 mm or more and 0.55 mm or less (i.e., from 0.49 mm to 0.55 mm).
It is preferable that the width of each of the coil conductors be 45 μm or more and 75 μm or less (i.e., from 45 μm to 75 μm). The width of each of the coil conductors is a dimension that is indicated by double-headed arrow W in
It is preferable that the thickness of each of the coil conductors be 3.5 μm or more and 6.0 μm or less (i.e., from 3.5 μm to 6.0 μm). The thickness of each of the coil conductors is a dimension that is indicated by double-headed arrow T in
It is preferable that the distance between the coil conductors be 3.0 μm or more and 5.0 μm or less (i.e., from 3.0 μm to 5.0 μm). The distance between the coil conductors is a dimension that is indicated by double-headed arrow D in
It is preferable that the diameter of each of the land portions of the coil conductors be 30 μm or more and 50 μm or less (i.e., from 30 μm to 50 μm). The diameter of each of the land portions of the coil conductors is a dimension that is indicated by double-headed arrow R in
When the first main surface of the multilayer body serves as the mounting surface, it is preferable that the length of a portion of the first outer electrode, the portion covering the first main surface of the multilayer body, and the length of a portion of the second outer electrode, the portion covering the first main surface of the multilayer body, each be 0.20 mm or less. In addition, it is preferable that these lengths each be 0.10 mm or more.
The length of the portion of the first outer electrode covering the first main surface of the multilayer body and the length of the portion of the second outer electrode covering the first main surface of the multilayer body are each a dimension that is indicated by double-headed arrow E1 in
The multilayer coil component of the present disclosure is manufactured by, for example, the following method.
Fe2O3, ZnO, CuO, and NiO are weighed in predetermined proportions. Each of the oxides may contain incidental impurities. Next, a slurry is produced by wet-blending these weighed materials together and then grinding the materials. In this case, an additive such as Mn3O4, Bi2O3, CO3O4, SiO2, or SnO2 may be added. Subsequently, the obtained slurry is dried and then preliminarily fired. The temperature at which the preliminary firing is performed is, for example, 700° C. or higher and 800° C. or lower (i.e., from 700° C. to 800° C.). The length of time over which the preliminary firing is performed is, for example, 2 hours or longer and 5 hours or shorter. In the manner described above, a powdery ferrite material is produced as the magnetic material.
It is preferable that the ferrite material contain 40 mol % or more and 49.5 mol % or less (i.e., from 40 mol % to 49.5 mol %) of Fe2O3, 2 mol % or more and 35 mol % or less (i.e., from 2 mol % to 35 mol %) of ZnO, 6 mol % or more and 13 mol % or less (i.e., from 6 mol % to 13 mol %) of CuO, and 10 mol % or more and 45 mol % or less (i.e., from 10 mol % to 45 mol %) of NiO.
A non-magnetic material powder is weighed. A glass powder containing an alkali metal such as potassium, boron, silicon, and aluminum in predetermined proportions is prepared as borosilicate glass. In addition, forsterite powder is prepared as a filler. Quartz powder may be further prepared as another filler.
It is preferable that the borosilicate glass contain 70% by weight or more and 85% by weight or less (i.e., from 70% by weight to 85% by weight) of Si in terms of SiO2, 10% by weight or more and 25% by weight or less (i.e., from 10% by weight to 25% by weight) of B in terms of B2O3, 0.5% by weight or more and 5% by weight or less (i.e., from 0.5% by weight to 5% by weight) of an alkali metal Ain terms of A2O, and 0% by weight or more and 5% by weight or less (i.e., from 0% by weight to 5% by weight) of Al in terms of Al2O3.
It is preferable that the non-magnetic material contain 1.5% by volume or more and 20% by volume or less (i.e., from 1.5% by volume to 20% by volume) of forsterite powder serving as the filler.
Ag powder is prepared and kneaded with predetermined amounts of a solvent (such as eugenol), a resin (such as ethyl cellulose), and a dispersant by using a planetary mixer or the like, and then, the resulting mixture is dispersed by using a triple-roll mill, so that an electrically conductive paste for the internal conductors is produced.
In this case, the pigment volume concentration (PVC) that is the concentration of the volume of the Ag powder with respect to the sum of the volume of the Ag powder and the volume of the resin component contained in the electrically conductive paste is adjusted so as to adjust the shrinkage percentage of the electrically conductive paste during firing. When the PVC is increased, the shrinkage percentage of the electrically conductive paste during firing can be increased.
It is preferable that the PVC of the electrically conductive paste be 3% or more and 95% or less (i.e., from 3% to 95%).
The absolute value of the shrinkage percentage of the electrically conductive paste during firing is preferably 3% or more and 30% or less (i.e., from 3% to 30%), more preferably 5% or more and 27% or less (i.e., from 5% to 27%), and further preferably 7% or more and 20% or less (i.e., from 7% to 20%).
The method of measuring the shrinkage percentage of the electrically conductive paste will be described in the Examples section.
The magnetic material and the non-magnetic material are weighed in predetermined proportions. Next, these weighed materials, an organic binder such as a polyvinyl butyral-based resin, an organic solvent such as ethanol or toluene, a plasticizer, and so forth are mixed together and then ground, so that a slurry is produced. Then, the obtained slurry is formed into a sheet shape having a predetermined thickness by a doctor blade method or the like, and then, the sheet-shaped slurry is punched into a predetermined shape, which is, for example, a rectangular shape, so that a green sheet is produced.
It is preferable that the thickness of the green sheet be 12 μm or more and 50 μm or less (i.e., from 12 μm to 50 μm).
The absolute value of the shrinkage percentage of the green sheet during firing is preferably 7% or more and 40% or less (i.e., from 7% to 40%), more preferably 10% or more and 30% or less (i.e., from 10% to 30%), and further preferably 13% or more and 27% or less (i.e., from 13% to 27%).
The method of measuring the shrinkage percentage of the green sheet will be described in the Examples section.
The proportion of the volume of the magnetic material relative to the sum of the volume of the magnetic material and the volume of the non-magnetic material is preferably 10% by volume or more and 80% by volume or less (i.e., from 10% by volume to 80% by volume), more preferably 15% by volume or more and 70% by volume or less (i.e., from 15% by volume to 70% by volume), and further preferably 20% by volume or more and 65% by volume or less (i.e., from 20% by volume to 65% by volume).
It is preferable that (the absolute value of) the shrinkage percentage of the electrically conductive paste during firing be smaller than (the absolute value of) the shrinkage percentage of the green sheet during firing. In other words, it is preferable that the electrically conductive paste exhibit less shrinkage than the green sheet during firing. As a result, the stress applied to the insulating layers by the coil conductors increases, and the non-magnetic material having fluidity is pushed out from between the coil conductors during firing. As a result, the Fe content in the first regions can be set to be higher than the Fe content in the second region.
More specifically, it is preferable that the difference between the absolute value of the shrinkage percentage of the green sheet during firing and the absolute value of the shrinkage percentage of the electrically conductive paste during firing be 1.2% or more. As a result, when the total amount of Si and Fe is 100% by weight, the difference between the average Fe content in the first regions and the average Fe content in the second region can be set to 1.7% by weight or more. The difference in the absolute value of the shrinkage percentage is more preferably 4% or more, and further preferably 6% or more.
The upper limit of the difference between the absolute value of the shrinkage percentage of the green sheet during firing and the absolute value of the shrinkage percentage of the electrically conductive paste during firing may be suitably set. However, the upper limit is preferably 30% or less, more preferably 25% or less, and further preferably 20% or less.
Coil sheets on which conductor patterns for the coil conductors are formed by applying an electrically conductive paste to the green sheets are produced.
More specifically, first, a laser beam is radiated onto predetermined portions of the green sheets so as to form via holes.
Next, the electrically conductive paste is applied to surfaces of the green sheets by screen printing or the like while filling the via holes with the electrically conductive paste. As a result, while conductor patterns for the via conductors are formed in the via holes, the conductor patterns for the coil conductors that are connected to the conductor patterns for the via conductors are formed on the surfaces of the green sheets. In this manner, the conductor patterns for the coil conductors and the conductor patterns for the via conductors are formed on and in the green sheets, so that the coil sheets are produced. The number of the coil sheets that are produced is two or more, and each of the coil sheets is provided with one of the conductor patterns for the coil conductors that correspond to the coil conductors illustrated in
In addition, via sheets that are the green sheets in which the conductor patterns for the via conductors are formed by filling the via holes with the electrically conductive paste by screen printing or the like are produced separately from the coil sheets. The number of the via sheets that are produced is also two or more, and each of the via sheets is provided with one of the conductor patterns for the via conductors that correspond to the via conductors illustrated in
Subsequently, a chip is produced by laminating the coil sheets, and the formed chip is fired so as to produce the multilayer body. More specifically, a multilayer body block production step and a multilayer body and coil production step that will be described below are performed.
The coil sheets and the via sheets are laminated together in the lamination direction in an order corresponding to that illustrated in
First, the multilayer body block is cut into pieces each having a predetermined size by using a dicer or the like so as to produce individual chips.
Next, the individual chips are fired. The temperature at which the firing is performed is, for example, 900° C. or higher and 920° C. or lower (i.e., from 900° C. to 920° C.). The length of time over which the firing is performed is, for example, 2 hours or longer and 4 hours or shorter.
By firing the individual chips, the green sheets of the coil sheets and the green sheets of the via sheets become the insulating layers. As a result, multilayer bodies in each of which the plurality of insulating layers are laminated together in the lamination direction, which is the length direction in this case, are produced. A magnetic phase and a non-magnetic phase are formed in each of the multilayer bodies.
By firing the individual chips, the conductor patterns for the coil conductors and the conductor patterns for the via conductors of the coil sheets become the coil conductors and the via conductors. As a result, a coil in which the plurality of coil conductors are laminated together in the lamination direction and electrically connected to one another by the via conductors is produced.
In the manner described above, the multilayer body and the coil formed inside the multilayer body are produced. The lamination direction of the insulating layers and the direction in which the coil axis of the coil extends are parallel to the first main surface of the multilayer body, which is the mounting surface, and in this case, they are parallel to the length direction.
By firing the individual chips, the conductor patterns for the via conductors of the via sheets become the via conductors. As a result, the first connection conductor and the second connection conductor in each of which the plurality of via conductors are laminated together in the length direction and electrically connected to one another are produced. The first connection conductor is exposed at the first end surface of the multilayer body. The second connection conductor is exposed at the second end surface of the multilayer body.
The corner portions and the ridge portions of the multilayer body may be rounded by performing, for example, barrel polishing.
First, an electrically conductive paste containing Ag powder and glass is applied to the first end surface and the second end surface of the multilayer body. Next, the obtained coating films are baked, so that base electrode layers are formed on surfaces of the multilayer body. More specifically, one of the base electrode layers is formed on the multilayer body in such a manner as to extend from the first end surface to a portion of the first main surface, a portion of the first side surface, and a portion of the second side surface. The other base electrode layer is formed on the multilayer body in such a manner as to extend from the second end surface to a portion of the first main surface, a portion of the first side surface, and a portion of the second side surface. The temperature at which each of the coating films is baked is, for example, 800° C. or higher and 820° C. or lower (i.e., from 800° C. to 820° C.).
After that, a nickel coating and a tin coating are sequentially formed on the surface of each of the base electrode layers by performing electrolytic plating or the like.
In this manner, the first outer electrode electrically connected to the coil by the first connection conductor and the second outer electrode electrically connected to the coil by the second connection conductor are formed.
The multilayer coil component is manufactured in the manner described above.
The present specification discloses the following contents.
<1> A multilayer coil component comprising a multilayer body that includes a plurality of insulating layers and a plurality of coil conductors laminated together in a lamination direction and that is provided with a coil formed inside the multilayer body; and an outer electrode that is provided at a surface of the multilayer body and electrically connected to the coil. The multilayer body has a first end surface and a second end surface that face each other in a length direction, a first main surface and a second main surface that face each other in a height direction, which is perpendicular to the length direction, and a first side surface and a second side surface that face each other in a width direction, which is perpendicular to the length direction and the height direction. The outer electrode includes a first outer electrode extending from at least a portion of the first end surface of the multilayer body to a portion of the first main surface and a second outer electrode extending from at least a portion of the second end surface of the multilayer body to a portion of the first main surface. The insulating layers have a magnetic phase and a non-magnetic phase and have a first region that is located between the coil conductors adjacent to each other in the lamination direction and a second region that is a region inside the coil excluding the first region. When a total amount of Si and Fe is 100% by weight, an average Fe content in the first region is greater than an average Fe content in the second region, and a difference between the average Fe contents is 1.7% by weight or more.
<2> The multilayer coil component according to <1>, wherein the lamination direction in the multilayer body and a coil axis of the coil are parallel to the first main surface.
<3> The multilayer coil component according to <1> or <2>, wherein the insulating layers have a third region that is defined by the first outer electrode, the second outer electrode, and an internal conductor including the coil conductor. Also, when the total amount of Si and Fe is 100% by weight, an average Fe content in the third region is less than the average Fe content in the first region, and a difference between the average Fe contents is 1.7% by weight or more.
<4> The multilayer coil component according to any one of <1> to <3>, wherein the magnetic phase contains at least Fe, Ni, Zn, and Cu, and the non-magnetic phase contains at least Si.
<5> The multilayer coil component according to <4>, wherein the non-magnetic phase contains at least a glass material.
<6> The multilayer coil component according to any one of <1> to <5>, wherein the number of the coil conductors laminated is 40 or more and 60 or less (i.e., from 40 to 60).
<7> A method of manufacturing a multilayer coil component comprising producing coil sheets on which conductor patterns for coil conductors are formed by applying an electrically conductive paste to green sheets; producing a chip by laminating the coil sheets in a lamination direction; and firing the chip so as to produce a multilayer body that is provided with a coil formed inside the multilayer body, the coil including a plurality of coil conductors electrically connected to each other. The green sheets contain a magnetic material and a non-magnetic material. The firing includes pushing out the non-magnetic material from a first region that is located between the coil conductors adjacent to each other in the lamination direction toward a second region that is a region inside the coil excluding the first region. Also, an absolute value of a shrinkage percentage of the electrically conductive paste during firing is smaller than an absolute value of a shrinkage percentage of each of the green sheets during firing, and a difference between the absolute values is 1.2% or more.
<8> The method of manufacturing a multilayer coil component according to <7>, wherein the non-magnetic material contains at least Si.
<9> The method of manufacturing a multilayer coil component according to <8>, wherein the non-magnetic material contains at least a glass material.
Examples that disclose the multilayer coil component of the present disclosure and the method of manufacturing a multilayer coil component of the present disclosure in a more specific manner will be described below. Note that the present disclosure is not limited to the following examples.
Multilayer bodies for multilayer coil components of Examples 1 to 3 and Comparative Example 1 were manufactured by the following method.
Main components were weighed so as to achieve the following proportions: 48.0 mol % of Fe2O3, 30.0 mol % of ZnO, 14.0 mol % of NiO, and 8.0 mol % of CuO. Next, a slurry was formed by putting these weighed materials, pure water, and a dispersant into a ball mill together with PSZ media, mixing them, and then grinding them. After that, the obtained slurry was dried and then preliminarily fired at 800° C. for two hours. In this manner, a powdery ferrite material was produced as the magnetic material.
Borosilicate glass powder containing Si, B, K, and Al in predetermined proportions was prepared, and forsterite powder and quartz powder were prepared as fillers. The borosilicate glass powder, the forsterite powder, and the quartz powder were weighed such that the volume ratio between borosilicate glass, forsterite, and quartz was 93:6:1. Next, a slurry was formed by putting these weighed materials, pure water, and a dispersant into a ball mill together with PSZ media, mixing them, and then grinding them. Then, the obtained slurry was dried, so that a powdery non-magnetic material was produced.
The magnetic material and the non-magnetic material were weighed such that the volume ratio between the magnetic material and the non-magnetic material was 60:40. Next, a slurry was formed by putting these weighed materials, a polyvinyl butyral-based resin serving as an organic binder, and ethanol and toluene each serving as an organic solvent into a ball mill together with PSZ media, mixing them, and then grinding them. Then, the obtained slurry was formed into a sheet shape having a predetermined thickness by the doctor blade method and then punched into a predetermined shape, so that each green sheet was produced.
Ag powder was kneaded with predetermined amounts of a solvent (eugenol), a resin (ethyl cellulose), and a dispersant by using a planetary mixer, and then, the resulting mixture was dispersed by using a triple-roll mill, so that an electrically conductive paste was produced.
In this case, four types of electrically conductive pastes A to D whose shrinkage percentages during firing were different from one another were prepared by adjusting the pigment volume concentration (PVC).
Via holes were formed in predetermined portions of the green sheets and filled with one of the electrically conductive pastes so as to form via conductors, and after that, coil conductor patterns were printed, so that coil sheets were obtained.
In addition, via holes were formed by radiating a laser beam onto predetermined portions of the other green sheets. Via conductors were formed by filling these via holes with one of the electrically conductive pastes, so that via sheets were obtained.
The coil sheets and the via sheets were laminated together in the lamination direction in an order corresponding to that illustrated in
The number of the coil conductors laminated so as to form three turns of the coil was set to four, and the total number of the coil conductors laminated was set to 44. The number of turns of the coil was set to 33.
The multilayer body block was cut into pieces by using a dicer, so that individual chips were produced. Subsequently, the individual chips were fired at 910° C. for four hours, so that multilayer bodies were obtained. A magnetic phase and a non-magnetic phase were formed in each of the multilayer bodies.
An electrically conductive paste containing Ag powder and glass was poured into a coating-film forming tank so as to form a coating film having a predetermined thickness. Portions of the multilayer body at which the outer electrodes were to be formed were dipped into the coating film.
After dipping, baking was performed at a temperature of about 800° C., so that base electrode layers of the outer electrodes were formed. The thickness of each of the base electrode layers was set to about 5 m.
Subsequently, a nickel coating and a tin coating were sequentially formed as plating electrodes on each of the base electrode layers by electrolytic plating, so that the outer electrodes were formed.
In the manner described above, the multilayer coil components of Examples 1 to 3 and Comparative Example 1 were manufactured.
Regarding the size of each of the produced multilayer coil components, the dimension in the length direction was 0.6 mm. The dimension in the height direction was 0.3 mm. The dimension in the width direction was 0.3 mm.
A green sheet that has been produced by the above-described method was cut so as to have a size of about 5 mm×about 5 mm, and after that, changes in sample dimensions were measured by using a thermomechanical analyzer (TMA) under heating conditions the same as those under which the above-mentioned firing was performed. In other words, as illustrated in
Δ(%)=(L1−L0)/L0×100
In addition, each of the above-mentioned electrically conductive pastes A to D was applied to a polyethylene terephthalate (PET) film and dried. After that, each of the PET films was cut so as to have a size of about 5 mm×about 5 mm, and then, changes in sample dimensions were measured by using the thermomechanical analyzer (TMA) under the heating conditions the same as those under which the above-mentioned firing was performed (see
The results of the shrinkage percentage measurement are shown in Table 1 below.
Measurement of Difference between Fe Content in First Regions and Fe Content in Second Region
Produced samples (the multilayer coil components of Examples 1 to 3 and Comparative Example 1) were each placed upright such that the width direction thereof (the z direction) is parallel to the vertical direction and covered with a resin. Each of the samples was ground in the width direction thereof by using a grinder to a depth at which a substantially central portion of the sample in the width direction was exposed. In the obtained cross section of each of the samples, the compositions of the first and second regions of the insulating layers (the insulator) were measured by using the energy dispersive X-ray spectrometry (EDX) in the following manner. In other words, as illustrated in
Furthermore, when the total amount of Si and Fe is 100% by weight, the difference between the average Si content (% by weight) in the second region 152 and the average Si content (% by weight) in the first regions 151 in each of the samples was determined by subtracting the measured average Si content in the first regions 151 from the measured average Si content in the second region 152.
The results are shown in Table 2 below.
When the difference in shrinkage percentage between the green sheet and one of the electrically conductive pastes is a negative value, the shrinkage percentage of the electrically conductive paste is lower (the absolute value is smaller) than that of the green sheet, that is, the amount of shrinkage of the electrically conductive paste is smaller than that of the green sheet.
In this case, it is assumed that the stress applied to the insulating layers by the coil conductors increases and that the non-magnetic material having fluidity is pushed out from between the coil conductors during firing. Thus, in Examples 1 to 3, it is assumed that the amount of the ferrite (i.e., the average Fe content) in the first regions, each of which is located between two of the coil conductors that are adjacent to each other, became greater than the amount of the ferrite (i.e., the average Fe content) in the second region excluding the first regions (the difference between them is 1.7% by weight or more).
In contrast, when the difference in shrinkage percentage between the green sheet and one of the electrically conductive pastes is a positive value, the shrinkage percentage of the electrically conductive paste is higher (the absolute value is larger) than that of the green sheet, that is, the amount of shrinkage of the electrically conductive paste is larger than that of the green sheet.
In this case, it is assumed that the coil conductors do not apply stress to the insulating layers and that there is no difference (or there is a small difference) in the average Fe content between the regions in the insulating layers (the insulator). Thus, in Comparative Example 1, there was only a small difference in the amount of the ferrite (i.e., the average Fe content) between the first regions and the second region.
In addition, the impedance at the 100 MHz in each of the multilayer coil components of Examples 1 to 3 and Comparative Example 1 was evaluated, and as a result, higher values were obtained in Examples 1 to 3 compared with Comparative Example 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-189201 | Nov 2022 | JP | national |
