Patent Application
20220336140
The present invention relates to a coil-type electronic component.
Patent Literature 1 describes an invention related to a soft magnetic alloy powder including Fe—Ni-based particles in which each amount of Fe, Ni, Co, and Si is controlled within a specific range.
However, while having high inductance, a multilayer coil in which the Fe—Ni-based particles are included as a magnetic element body unfortunately has low DC superimposition characteristic.
It is an objective of the present invention to provide a coil-type electronic component having sufficiently high inductance (L) and DC superimposition characteristic (Idc).
A coil-type electronic component according to the present invention comprises an element including a magnetic element body and a coil conductor, wherein a portion of the magnetic element body in between layers of the coil conductor adjacent to each other in an axis direction of the coil conductor includes first soft magnetic metal particles, a portion of the magnetic element body on an outer side along the axis includes second soft magnetic metal particles, and the first soft magnetic metal particles have a saturation magnetization higher than that of the second soft magnetic metal particles.
With the above configurations, the coil-type electronic component according to the present invention has sufficiently high inductance and DC superimposition characteristic.
The first soft magnetic metal particles preferably comprise an Fe—Si-based alloy. The saturation magnetization of the first soft magnetic metal particles can thus be further increased. As a result, it is easier to increase the saturation magnetization of the first soft magnetic metal particles compared to the saturation magnetization of the second soft magnetic metal particles, which can improve inductance and DC superimposition characteristic sufficiently.
The second soft magnetic metal particles preferably comprise an Fe—Ni-based alloy. It is thus easier to increase the saturation magnetization of the first soft magnetic metal particles compared to the saturation magnetization of the second soft magnetic metal particles, which can improve inductance and DC superimposition characteristic sufficiently.
A second inner-diameter magnetic element body occupying at least a part of an axis-center inner-diameter region of the element including the axis of the coil conductor preferably includes the second soft magnetic metal particles.
A proportion of an area of the second inner-diameter magnetic element body in an area of the axis-center inner-diameter region is preferably 30% or more in a cross section perpendicular to the axis of the coil conductor. A balance between inductance and DC superimposition characteristic can thus be further improved.
The first soft magnetic metal particles preferably have an average particle size of 1 to 6 μm. When the average particle size of the first soft magnetic metal particles is 1 to 6 μm, inductance can be increased compared to when the average particle size of the first soft magnetic metal particles is smaller than 1 μm. Also, when the average particle size of the first soft magnetic metal particles is 1 to 6 μm, it is possible to increase inductance compared to when the average particle size of the first soft magnetic metal particles exceeds 6 μm, prevent plating elongation, and reduce the number of short circuits.
The second soft magnetic metal particles preferably have an average particle size of 1 to 15 μm. When the average particle size of the second soft magnetic metal particles is 1 to 15 μm, inductance can be increased compared to when the average particle size of the second soft magnetic metal particles is smaller than 1 μm. Also, when the average particle size of the second soft magnetic metal particles is 1 to 15 μm, it is possible to improve DC superimposition characteristic compared to when the average particle size of the second soft magnetic metal particles exceeds 15 μm, prevent plating elongation, and reduce the number of short circuits.
A second outer-diameter magnetic element body occupying at least a part of an axis-center outer-diameter region of the element on an outer side in a radial direction of the coil conductor preferably includes the second soft magnetic metal particles. Inductance can thus be further increased.
A proportion of an area of the second outer-diameter magnetic element body in an area of the axis-center outer-diameter region may be 15% or more in a cross section perpendicular to the axis of the coil conductor. DC superimposition characteristic can thus be further increased.
FIG. 1A1 is a schematic cross-sectional view along the line IAI-IAI in
Hereinafter, a multilayer coil 1 shown in
As shown in
In the present embodiment, an “inner side” means a side closer to a center (an axis N of the coil conductor 5) of the multilayer coil 1 whereas an “outer side” means a side farther from the center of the multilayer coil 1.
A material of the terminal electrodes 3 is not limited as long as it is an electrical conductor. For example, Ag, Cu, Au, Al, a Ag alloy, a Cu alloy, or the like is used. Particularly, Ag is preferably used for being inexpensive and having low resistance. The terminal electrodes 3 may include glass frit. The terminal electrodes 3 may also have a two-layered structure having a metal layer that is formed on the element 2 and comprises the above-mentioned metal or the above-mentioned metal and the glass frit, and a resin layer that is formed on the metal layer and comprises a conductive resin. A metal included in the conductive resin is not limited. For example, Ag may be included. Also, surfaces of the terminal electrodes 3 may be plated. For example, Cu, Ni, Sn, Cu—Ni—Sn, and/or Ni—Sn plating may be carried out appropriately.
Materials of the coil conductor 5 and the leading electrodes Sal and 5a2 can be any materials as long as they are electrical conductors. For example, Ag, Cu, Au, Al, a Ag alloy, a Cu alloy, or the like may be used. Particularly, Ag is preferably used for being inexpensive and having low resistance. The coil conductor 5 may include glass frit.
The number of times the coil conductor 5 is wound around its axis N is not limited and is, for example, 1.5 to 15.5 times. The coil conductor 5 may also have any thickness (Te). The thickness is, for example, 5 to 60 μm.
As shown in
In other words, the element 2 can be divided into the axis center region 2b, where the coil conductor 5 is embedded, and the axis end regions 2a1 and 2a2, where the coil conductor 5 is not embedded, located at the top and the bottom of the axis center region 2b in the axis direction (Z-axis direction). The axis direction of the coil conductor 5 is parallel to the lamination direction of the coil conductor 5.
Specifically, regions on the outer side, along the axis N, of an imaginary line that is perpendicular to the axis direction (Z-axis direction) and extends along an outer side of each of the leading electrodes Sal and 5a2 are defined as the axis end regions 2a1 and 2a2 respectively. A region on the inner side, along the axis N, of each imaginary line is defined as the axis center region 2b. In the present embodiment, the axis center region 2b is a region including the leading electrodes 5a1 and 5a2.
The element 2 can also be divided, along the radial direction (Y-axis direction) perpendicular to the axis direction, into an inner diameter region 4b of the coil conductor 5, a coil region 4a where the coil conductor 5 is wound, and an outer diameter region 4c located on an outer side of the radial direction of the coil conductor 5.
In the present embodiment, the element 2 is divided into the axis end regions 2a1 and 2a2 and the axis center region 2b in the Z-axis direction, as well as into the inner diameter region 4b, the coil region 4a, and the outer diameter region 4c in the radial direction, as described above.
Further, in the present embodiment, a region located in both of the axis center region 2b and the inner diameter region 4b is defined as an axis-center inner-diameter region 24bb. A region located in both of the axis center region 2b and the coil region 4a is defined as an axis-center coil region 24ba. A region located in both of the axis center region 2b and the outer diameter region 4c is defined as an axis-center outer-diameter region 24bc.
In the present embodiment, a region located in between adjacent windings of the coil conductor 5 in the axis direction in the axis-center coil region 24ba of the element 2 is defined as an interlayer region 24ba1. The interlayer region 24ba1 may have any thickness (Ti) in the Z-axis direction. The thickness is, for example, 5 to 100 μm.
The magnetic element body 4 according to the present embodiment comprises a first magnetic element body 40 including first soft magnetic metal particles and a second magnetic element body 42 including second soft magnetic metal particles arranged in a predetermined position.
The first magnetic element body 40 comprises a first interlayer magnetic element body 40a located in the axis-center coil region 24ba, a first inner-diameter magnetic element body 40b located in the axis-center inner-diameter region 24bb, and a first outer-diameter magnetic element body 40c located in the axis-center outer-diameter region 24bc, in the present embodiment.
The second magnetic element body 42 comprises second axis-end magnetic element bodies 42a1 and 42a2 located in the axis end regions 2a1 and 2a2, a second inner-diameter magnetic element body 42b located in the axis-center inner-diameter region 24bb, and a second outer-diameter magnetic element body 42c mentioned later, located in the axis-center outer-diameter region 24bc.
Specifically, as shown in
The first inner-diameter magnetic element body 40b is formed continuously from the first interlayer magnetic element body 40a. A shape of the first inner-diameter magnetic element body 40b is not limited. For example, a shape of a cross section of the first inner-diameter magnetic element body 40b is preferably a substantially rectangular shape along the axis center region 2b. The “substantially rectangular shape” in the present embodiment means that there may be some irregularities or tilts in the contour of the rectangular shape.
Further, as shown in
In the present embodiment, the axis end regions 2a1 and 2a2 on the outer side along the coil conductor 5 comprise the second axis-end magnetic element bodies 42a1 and 42a2 respectively.
The second magnetic element body 42 may comprise a region other than the axis end regions 2a1 and 2a2. For example, as shown in
While the above description was provided along the Y-Z cross sectional view shown in
FIG. 1A1 is a cross-sectional view along the line IAI-IAI in
In the cross section perpendicular to the axis N of the coil conductor 5 in the axis center region 2b of the present embodiment, the proportion (hereinafter referred to as a “second inner-diameter magnetic element body proportion”) of the area of the second inner-diameter magnetic element body 42b in the area of the axis-center inner-diameter region 24bb is preferably 30% or more and is more preferably 30% to 75%. In the cross section perpendicular to the axis N of the coil conductor 5 in the axis center region 2b of the present embodiment, the axis-center inner-diameter region 24bb is a region on the inner side of the inner-diameter boundary line R.
Also, in the cross section perpendicular to the axis N of the coil conductor 5 in the axis center region 2b, the proportion (hereinafter referred to as a “second outer-diameter magnetic element body proportion”) of the area of the second outer-diameter magnetic element body 42c in the area of the axis-center outer-diameter region 24bc is preferably 15% or more and is more preferably 15% to 50%. In the cross section perpendicular to the axis N of the coil conductor 5 in the axis center region 2b of the present embodiment, the axis-center outer-diameter region 24bc is a region on the outer side of the outer-diameter boundary line S.
In the present embodiment, the first soft magnetic metal particles have a higher saturation magnetization (Ms) than that of the second soft magnetic metal particles. When the saturation magnetization of the first soft magnetic metal particles and the saturation magnetization of the second soft magnetic metal particles are defined as “first Ms” and “second Ms” respectively, (first Ms/second Ms) is preferably 1.07 to 1.80 and more preferably 1.16 to 1.50. Hereinafter, the first soft magnetic metal particles and the second soft magnetic metal particles may be collectively referred to as “soft magnetic metal particles.”
A material of the first soft magnetic metal particles according to the present embodiment is not limited. The material is, for example, an Fe—Si-based alloy, an Fe—Si—Cr-based alloy, pure Fe, an Fe—Ni-based alloy, or an Fe—Si—Al-based alloy, and is preferably the Fe—Si-based alloy. This makes it possible to further increase the saturation magnetization of the first soft magnetic metal particles.
The amount of Fe in each of the first soft magnetic metal particles is preferably 92.0 to 97.0 mass % and more preferably 92.5 to 96.5 mass % in 100 mass % of the total amount of Fe and Si in the first soft magnetic metal particle.
The amount of Cr in the first soft magnetic metal particle is preferably 5 mass % or less and more preferably less than 2 mass % in 100 mass % of the total amount of Fe and Si in the first soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of P in the first soft magnetic metal particle is preferably 10 to 700 ppm and more preferably 40 to 650 ppm in 100 mass % of the total amount of Fe and Si in the first soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of a chemical element other than Fe, Si, Cr, and P in the first soft magnetic metal particle is preferably less than 3 mass % in 100 mass % of the total amount of Fe and Si in the first soft magnetic metal particle. The chemical element other than Fe, Si, Cr, and P in the first soft magnetic metal particle is, for example, Ni, 0, Co, or Al.
A material of the second soft magnetic metal particles according to the present embodiment is not limited. The material is, for example, an Fe—Ni-based alloy, an Fe—Si—Cr-based alloy, or an Fe—Si—Al-based alloy, and is preferably the Fe—Ni-based alloy. It is thus easier to increase the saturation magnetization of the first soft magnetic metal particles compared to the saturation magnetization of the second soft magnetic metal particles, which can improve inductance and DC superimposition characteristic sufficiently.
The amount of Fe in each of the second soft magnetic metal particles is preferably 33.0 to 68.0 mass % and more preferably 37.0 to 55.0 mass % in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle.
The amount of Ni in the second soft magnetic metal particle is preferably 14.0 to 56.0 mass % and more preferably 15.0 to 55.0 mass % in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of Si in the second soft magnetic metal particle is preferably 2.0 to 6.0 mass % in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of Co in the second soft magnetic metal particle is preferably 2.0 to 40.0 mass % in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of Cr in the second soft magnetic metal particle is preferably 1.8 mass % or less in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic.
The amount of P in the second soft magnetic metal particle is preferably 10 to 6000 ppm and more preferably 100 to 5000 ppm in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. This ensures a better balance between inductance and DC superimposition characteristic, further raises evaluation of prevention of plating elongation, and further decreases the number of short circuits.
The amount of a chemical element other than Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle is preferably less than 3 mass % in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle. The chemical element other than Fe, Ni, Si, Co, Cr, and P in the second soft magnetic metal particle is, for example, Al or O.
The first soft magnetic metal particles according to the present embodiment preferably have an average particle size of 1 to 6 μm. When the average particle size of the first soft magnetic metal particles is 1 to 6 μm, inductance can be increased compared to when the average particle size of the first soft magnetic metal particles is smaller than 1 μm. Also, when the average particle size of the first soft magnetic metal particles is 1 to 6 μm, it is possible to increase inductance compared to when the average particle size of the first soft magnetic metal particles exceeds 6 μm, prevent plating elongation, and reduce the number of short circuits.
The second soft magnetic metal particles according to the present embodiment preferably have an average particle size of 1 to 15 μm. When the average particle size of the second soft magnetic metal particles is 1 to 15 μm, inductance can be increased compared to when the average particle size of the second soft magnetic metal particles is smaller than 1 μm. Also, when the average particle size of the second soft magnetic metal particles is 1 to 15 μm, it is possible to improve DC superimposition characteristic compared to when the average particle size of the second soft magnetic metal particles exceeds 15 μm, prevent plating elongation, and reduce the number of short circuits.
The average particle size of the first soft magnetic metal particles is preferably equivalent to or smaller than the average particle size of the second soft magnetic metal particles. When the average particle size of the first soft magnetic metal particles and the average particle size of the second soft magnetic metal particles are defined as a “first average particle size” and a “second average particle size” respectively, (first average particle size/second average particle size) is preferably 0.2 to 1.0 and more preferably 0.2 to 0.5.
A method of measuring the average particle size of the soft magnetic metal particles is not limited. In the present embodiment, the average particle size is calculated as follows. A cross section of the multilayer coil 1 (electronic component) filled with a resin is observed with SEM, STEM, etc., and the area of each soft magnetic metal particle is calculated through an image analysis. A value (area diameter) calculated as a diameter (circle equivalent diameter) of a circle corresponding to the area is defined as a particle size of the soft magnetic metal particle. An average of the diameters of multiple soft magnetic metal particles is defined as the average particle size.
Shapes of the soft magnetic metal particles are not limited.
The magnetic element body 4 according to the present embodiment includes the soft magnetic metal particles connected to each other through firing. Specifically, a chemical element included in the soft magnetic metal particles that came into contact with each other through firing react with another chemical element (e.g., 0), and the soft magnetic metal particles connect with each other through bonding attributable to the reaction. In the magnetic element body 4 according to the present embodiment, the soft magnetic metal particles derived from a soft magnetic metal powder (raw material powder of the soft magnetic metal particles) connect with each other through the heat treatment. However, particle growth of each soft magnetic metal particle hardly occurs.
The amount of the first soft magnetic metal particles in the first magnetic element body 40 is preferably 90 mass % or more and is more preferably 95 mass % or more. As long as at least the above-mentioned amount of the first soft magnetic metal particles is included in the first magnetic element body 40, the first magnetic element body 40 does not have to be comprised entirely of the first soft magnetic metal particles. For example, the first magnetic element body 40 may include some metal particles with the saturation magnetization equivalent to or smaller than that of the second soft magnetic metal particles.
The amount of the second soft magnetic metal particles in the second magnetic element body 42 is preferably 90 mass % or more and is more preferably 95 mass % or more. As long as at least the above-mentioned amount of the second soft magnetic metal particles is included in the second magnetic element body 42, the second magnetic element body 42 does not have to be comprised entirely of the second soft magnetic metal particles and may include, for example, some metal particles with the saturation magnetization equivalent to or larger than that of the first soft magnetic metal particles.
Each of the soft magnetic metal particles may be covered with a coverage film. Specifically, the coverage film may be an oxide film, which may include a layer comprising a Si-containing oxide. With the coverage film covering the soft magnetic metal particle, insulating properties among the soft magnetic metal particles are increased, which improves a Q factor. Also, with the layer comprising the Si-containing compound included in the oxide film, formation of an Fe oxide can be prevented.
A method of determining regions of the first magnetic element body 40 and the second magnetic element body 42 of the element 2 according to the present embodiment is not limited. The regions may be determined by, for example, obtaining an elemental mapping with EDS and performing a composition analysis.
Because the compositions of the first magnetic element body 40 and the second magnetic element body 42 are different, by performing an image analysis of a cross section of the element 2 with SEM, STEM, etc., it is possible to determine the regions of the first magnetic element body 40 and the second magnetic element body 42 based on their contrast. Further, if the average particle sizes of the first soft magnetic metal particles and the second soft magnetic metal particles are different, it is easier to determine the regions of the first magnetic element body 40 and the second magnetic element body 42 based on their contrast, by performing the image analysis of the cross section of the element 2 with SEM, STEM, etc.
In the present embodiment, a set of raw materials of the first soft magnetic metal particles may be referred to as a “first soft magnetic metal powder,” a set of raw materials of the second soft magnetic metal particles may be referred to as a “second soft magnetic metal powder,” and a set of raw materials of the soft magnetic metal particles may be referred to as a “soft magnetic metal powder.” That is, the set of the raw materials of the first soft magnetic metal particles and the second soft magnetic metal particles may be collectively referred to as the “soft magnetic metal powder.”
Hereinafter, a method of manufacturing the first soft magnetic metal powder and the second soft magnetic metal powder according to the present embodiment is described.
In the present embodiment, a simple substance or an alloy of a constituent chemical element may be used as a raw material of the first soft magnetic metal powder. For example, Fe alone, Si alone, Cr alone, etc. may be used.
Also, an alloy or a simple substance of a constituent chemical element may be used as a raw material of the second soft magnetic metal powder. For example, an Fe—Ni alloy, Fe alone, Ni alone, Si alone, Co alone, Cr alone, etc. may be used.
In the present embodiment, the soft magnetic metal powder can be obtained using a method of manufacturing a known soft magnetic metal powder. Specifically, the soft magnetic metal powder can be manufactured with a gas atomizing method, a water atomizing method, a rotating disk method, etc. Among these, the water atomizing method is preferably used from a perspective of easily obtaining the soft magnetic metal powder having desirable magnetic properties.
In using the water atomizing method, the raw materials having an ingot, a chunk, or a shot shape are prepared, mixed together to have a desired composition, and then placed in a crucible provided in a water atomizing device.
Then, in an inert atmosphere, the crucible is heated to 1600° C. or more through high-frequency induction using a work coil arranged outside the crucible. The ingots, chunks, or shots in the crucible are thus melted and mixed, and a molten metal is obtained.
The melted material (molten metal) is supplied as a linear continuous fluid through a nozzle provided at a bottom of the crucible. Water is sprayed to the supplied molten metal at a high pressure (about 50 MPa), and the molten metal is formed into droplets. At the same time, the molten metal is rapidly cooled, then dehydrated, dried, and classified, so as to obtain the soft magnetic metal powder having a desired average particle size.
In the present embodiment, for example, the soft magnetic metal powder according to the present embodiment can be manufactured in such a manner that each raw material is melted, P is added to this molten material, and then the water atomizing method is used to turn the molten material with P into a fine powder. When P is included as an impurity in the raw material (e.g., the raw material of Fe), a total of the amount of P as the impurity and the amount of P added may be controlled to manufacture the soft magnetic metal powder including an intended amount of P. Alternatively, a plurality of materials of Fe each including a different amount of P may be used for turning the molten material including an adjusted amount of P into a fine powder using the water atomizing method.
In the present embodiment, the first soft magnetic metal powder (raw material powder of the first soft magnetic metal particles) and the second soft magnetic metal powder (raw material powder of the second soft magnetic metal particles) are each prepared using the above-mentioned method.
Next, a method of manufacturing the multilayer coil 1 shown in
Then, using the second paste, a second axis-end green sheet is formed which becomes the second axis-end magnetic element body 42a1 constituting the axis end region 2a1 after firing.
Next, on the second axis-end green sheet, a conductor 50a1, a first green sheet 400a made from the first paste, and a second green sheet 420a made from the second paste are printed in a form of a printed body 100a shown in
The conductor 50a1 and a conductor 50a2 mentioned later are conductors comprising silver (Ag) or the like that become the leading electrodes 5a1 and 5a2 of the coil conductor 5 after firing. Each of the first green sheet 400a and first green sheets 400b to 400h mentioned later becomes the first magnetic element body 40 after firing. Each of the second green sheet 420a and second green sheets 420b to 420h mentioned later becomes the second magnetic element body 42 after firing. Consequently, in the step shown in
Next, a conductor 50b, the first green sheet 400b made from the first paste, and the second green sheet 420b made from the second paste are printed in a form of a printed body 100b shown in
The conductor 50b and conductors 50c to 50g mentioned later are conductors comprising silver (Ag) or the like that become the coil conductor 5 after firing.
Next, the conductor 50c, the first green sheet 400c made from the first paste, and the second green sheet 420c made from the second paste are printed in a form of a printed body 100c shown in
Next, the conductor 50d, the first green sheet 400d made from the first paste, and the second green sheet 420d made from the second paste are printed in a form of a printed body 100d shown in
Next, the conductor 50e, the first green sheet 400e made from the first paste, and the second green sheet 420e made from the second paste are printed in a form of a printed body 100e shown in
Next, the conductor 50f, the first green sheet 400f made from the first paste, and the second green sheet 420f made from the second paste are printed in a form of a printed body 100f shown in
Then, printing shown in
Next, the conductor 50a2, the first green sheet 400h made from the first paste, and the second green sheet 420h made from the second paste are printed in a form of a printed body 100h shown in
In each of
Further, using the second paste, on the printed body 100h shown in
In a multilayer body obtained in this way, first, the conductor 50a1 of the printed body 100a shown in
The 50b1 of the conductor 50b of the printed body 100b shown in
The 50c2 of the conductor 50c of the printed body 100c shown in
The conductor 50d of the printed body 100d shown in
The 50e1 of the conductor 50e of the printed body 100e shown in
The 50f2 of the conductor 50f of the printed body 100f shown in
The conductor 50g of the printed body 100g shown in
Here, with the printed body 100d shown in
Although the leading electrode 5a1 and the leading electrode 5a2 in
For example, 1 to 2 times of the printing shown in
While the method of manufacturing the multilayer body using a printing method is described above, the multilayer body having the above-mentioned configuration can also be obtained using a sheet method.
The obtained multilayer body is subjected to a heat treatment (a binder removal step and a firing step). Through this, the binder is removed, and a fired body (element) is obtained in which the soft magnetic metal particles included in the soft magnetic metal powder are connected with and fixed to (consolidated with) each other. A holding temperature (binder removal temperature) in the binder removal step is not limited as long as the binder can be decomposed and removed as gas. The binder removal temperature may be 300° C. or more to 450° C. or less, for example. A holding time (binder removal time) of the binder removal step is also not limited, and may be 0.5 hours or more to 2.0 hours or less, for example.
A holding temperature (firing temperature) in the firing step is not limited as long as the soft magnetic metal particles constituting the soft magnetic metal powder connect with each other. The firing temperature may be 550° C. or more to 850° C. or less. A holding time (firing time) of the firing step is also not limited, and may be 0.5 hours or more to 3.0 hours or less.
Note that, in the present embodiment, preferably an atmosphere during the binder removal and the firing is adjusted.
An annealing treatment (heat treatment) may be carried out after firing. Conditions for carrying out the annealing treatment are not limited. For example, the annealing treatment may be carried out at a temperature ranging from 500 to 800° C. for 0.5 to 2.0 hours. An atmosphere after the annealing is also not limited.
Next, the terminal electrodes 3 are formed on the element. A method of forming the terminal electrodes 3 is not limited. Usually, a metal (e.g., Ag) that becomes the terminal electrodes 3 is made into slurry together with an additive, such as a solvent and a binder.
The multilayer coil 1 according to the present embodiment is obtained using the above-mentioned method.
In the multilayer coil 1 according to the present embodiment, the interlayer magnetic element body 40a positioned in the interlayer region 24ba1 of the coil conductor 5 includes the first soft magnetic metal particles, and the axis-end magnetic element bodies 42a1 and 42a2 positioned on the outer side along the axis N of the coil conductor 5 include the second soft magnetic metal particles. The saturation magnetization of the first soft magnetic metal particles is higher than that of the second soft magnetic metal particles. With such configurations, the multilayer coil 1 (coil-type electronic component) according to the present embodiment has sufficiently high inductance and DC superimposition characteristic.
Hereinafter, the second embodiment is described. What is not described is similar to those in the first embodiment.
As shown in
Specifically, in a cross section shown in
Because the double helix structure of the coil conductor 5 makes the coil dense, inductance can be increased.
Although the number of windings in the double helix structure of the coil conductor 5 in
A method of manufacturing the multilayer coil 1 according to the present embodiment is not limited. For example, it is possible to obtain the multilayer coil 1 according to the present embodiment by obtaining a green multilayer body in which the positions of the coil conductors, the first green sheets, and the second green sheets in
Hereinafter, the third embodiment is described. What is not described is similar to those in the first embodiment.
As shown in
In the third embodiment, regions on the outer side along imaginary lines extending along the outer sides of the outermost portions of the coil conductor 5 are the axis end regions 2a1 and 2a2, and a region on the inner side is the axis center region 2b. That is, in the third embodiment, the axis center region 2b is a region that does not include the leading electrodes Sal and 5a2.
Hereinafter, the fourth embodiment is described. What is not described is similar to those in the first embodiment.
The magnetic element body according to the present embodiment comprises the soft magnetic metal particles and a resin.
In the element obtained using the method described in the first to third embodiments, there is a void space in an area of the magnetic element body where the soft magnetic metal particles are not present. In the present embodiment, for example, the element is impregnated with the resin so that the space is filled with the resin.
With the space filled with the resin, strength (particularly bending strength) of the multilayer coil is increased. Also, with the insulation properties among the soft magnetic metal particles further increased, inductance and the Q factor are more easily improved. Further, reliability and heat resistance improve, and short circuits become less likely to occur in the multilayer coil.
A method of impregnating the resin is not limited. One example is a method through vacuum impregnation. The vacuum impregnation is carried out by immersing the element of the above multilayer coil in the resin and controlling an air pressure. The resin enters inside the magnetic element body by reducing the air pressure. Because the space is present in the magnetic element body, the resin can enter the inside, particularly the interlayer region, which is the most difficult part to enter, of the magnetic element body through capillary action via the space. The resin is impregnated in the magnetic element body, and then is cured by heating. Heating conditions differ depending on the type of the resin.
The type of the resin is not limited. For example, when a phenol resin or an epoxy resin is used, the resin sufficiently enters the space inside the magnetic element body (particularly the interlayer region), and easily fills the space sufficiently even after the curing. Further, the resin is not easily decomposed trough heating, which allows for high heat resistance. Particularly when the phenol resin or the epoxy resin is used, the resin sufficiently and easily enters the space inside the magnetic element body (particularly the interlayer region), compared to when a silicone resin is used. Note that the resin is preferably the phenol resin for being inexpensive and easily handled.
The amount of the resin in the magnetic element body of the multilayer coil obtained in the end is preferably 0.5 mass % or more to 3.0 mass % or less. Note that, the amount of the resin can be controlled by changing a resin solution concentration at the time of immersing, an immersing time, the number of times of immersing, and the like during impregnation, for example.
In the present embodiment, electroplating can be carried out on the terminal electrodes after resin filling. Because the space is filled with the resin, a plating solution scarcely enters inside the magnetic element body even when the magnetic element body is introduced into the plating solution. Consequently, a short circuit does not occur in the multilayer coil even after plating, and inductance is maintained high.
Although the embodiments of the present invention have been described above, the present invention is not at all limited to the above embodiments. The present invention may be put into practice in various forms without departing from the scope of the invention.
For example, as shown in
For example, as shown in
For example, as shown in
For example, as shown in
A method of changing the positions of the first magnetic element body 40 and the second magnetic element body 42 as shown in
Also, while the second inner-diameter magnetic element body proportion and the second outer-diameter magnetic element body proportion are calculated using a cross section perpendicular to the axis direction of the coil conductor 5 above, the second inner-diameter magnetic element body proportion and the second outer-diameter magnetic element body proportion may be calculated by obtaining and using multiple cross sections parallel to the axis direction of the coil conductor 5.
Although the multilayer coil is used an example of the coil-type electronic component in the present embodiments, transformers, choke coils, coils, etc. are known as other coil-type electronic components. Also, the coil-type electronic component according to the present embodiments is suitably used in a power supply circuit or the like in various electronic apparatus (e.g., mobile devices) to serve as an inductor or impedance.
Hereinafter, the present invention is described in detail using examples. However, the present invention is not limited to these examples.
(Each sample of Tables 1 to 3)
Each raw material was prepared so that each soft magnetic metal powder had a composition shown in Table 1 or Table 2. Each of [Mass %] and [ppm] in Table 1 is the amount of each constituent in 100 mass % of the total amount of Fe and Si. Each of [Mass %] and [ppm] in Table 2 is the amount of each constituent in 100 mass % of the total amount of Fe, Ni, Si, Co, Cr, and P.
Each obtained soft magnetic metal powder was subjected to a composition analysis using an ICP analysis method, and thus was confirmed to have a composition shown in Table 1 or Table 2. Therefore, also in examples and comparative examples described later, a composition of prepared raw materials and a composition of each soft magnetic metal powder were deemed to be the same.
A saturation magnetization of each obtained soft magnetic metal powder was measured using a vibrating sample magnetometer (VSM-3S-15 manufactured by Toei Industry Co., Ltd.) at an external magnetic field of 795.8 kA/m (10 kOe). Tables 1 and 2 show results.
The obtained first soft magnetic metal powder was used to prepare a first paste, and the obtained second soft magnetic metal powder was used to prepare a second paste.
In printed bodies 100a to 100h shown in
Next, a binder removal treatment was carried out for the obtained green multilayer coil at 400° C. in an inert atmosphere (N2 gas atmosphere). After that, the green multilayer coil was fired at 750° C. for 1 hour in a reduced atmosphere (mixed gas atmosphere of N2 gas and H2 gas, having a hydrogen concentration of 1.0%). A fired body was thus obtained.
A terminal electrode paste was applied to both end faces of the obtained fired body and dried, then a baking treatment was carried out at 700° C. for 1 hour in an atmosphere having an oxygen partial pressure of 1%. Thus, terminal electrodes 3 were formed, and a baked multilayer coil was obtained.
Each obtained baked multilayer coil was impregnated with a resin. Specifically, the baked multilayer coil was vacuum impregnated with a mixture of phenol resin raw materials, then heated at 150° C. for 2 hours to have the resin cured. Thus, the resin filled a void space of the baked multilayer coil. Note that, a solvent and the like included in the raw material mixture evaporated when the resin was cured. Then, electroplating was carried out to form a Ni plating layer and a Sn plating layer on the terminal electrodes. Thus, a multilayer coil 1 was obtained.
Regarding internal dimensions of the obtained multilayer coil, a coil conductor 5 had a thickness (Te) of 40 μm and the interlayer region 24ba1 had a thickness (Ti) of 15 μm.
A composition analysis and measurement of an average particle size, saturation magnetization, inductance, and DC superimposition characteristic of the obtained multilayer coil were carried out as follows.
Regarding the multilayer coil of Example 1, elemental mapping photographs of the axis end regions 2a1 and 2a2, the axis-center inner-diameter region 24bb, the interlayer region 24ba1, and the axis-center outer-diameter region 24bc were obtained to carry out the composition analysis. From the analysis results, it was confirmed that first soft magnetic metal particles having the same composition as that of the first soft magnetic metal powder were formed in a portion where the first soft magnetic metal powder was used, and second soft magnetic metal particles having the same composition as that of the second soft magnetic metal powder were formed in a portion where the second soft magnetic metal powder was used. Consequently, also in the examples and comparative examples described later, it was assumed that the first soft magnetic metal particles having the same composition as that of the first soft magnetic metal powder were formed in the portion where the first soft magnetic metal powder was used, and the second soft magnetic metal particles having the same composition as that of the second soft magnetic metal powder were formed in the portion where the second soft magnetic metal powder was used.
Circle equivalent diameters of the first soft magnetic metal particles and the second soft magnetic metal particles were calculated by analyzing an image of a cross section of the multilayer coil of Example 1 using SEM. The circle equivalent diameters were used as particle sizes. The particle sizes of four hundred first soft magnetic metal particles and the particle sizes of four hundred second soft magnetic metal particles were calculated, and an average particle size of the first soft magnetic metal particles and an average particle size of the second soft magnetic metal particles were calculated. Table 1 shows the average particle size of the first soft magnetic metal particles, and Table 2 shows the average particle size of the second soft magnetic metal particles.
The first magnetic element body and the second magnetic element body of the multilayer coil of Example 1 were subjected to microfabrication through laser processing to be cut. Saturation magnetization of the first soft magnetic metal particles and the second soft magnetic metal particles was measured using a vibrating sample magnetometer (VSM-3S-15 manufactured by Toei Industry Co., Ltd.) at an external magnetic field of 795.8 kA/m (10 kOe). From the results, it was confirmed that the saturation magnetization of the first soft magnetic metal particles was the same as that of the first soft magnetic metal powder, and the saturation magnetization of the second soft magnetic metal particles was the same as that of the second soft magnetic metal powder. Consequently, also in the examples and comparative examples described later, it was assumed that the saturation magnetization of the first soft magnetic metal particles was the same as that of the first soft magnetic metal powder, and the saturation magnetization of the second soft magnetic metal particles was the same as that of the second soft magnetic metal powder.
Inductance (L) of the obtained multilayer coil was measured using an LCR meter (4285A manufactured by HEWLETT PACKARD) at f=2 MHz and I=0.1 A. An average of the L values of thirty multilayer coils in each example or comparative example was calculated. Table 3 shows the results. Also, ΔL/L was calculated as a rate of change in comparison to the average value of L of “Comparison target in terms of ΔL/L and ΔIdc/Idc” in Table 3. For example, because the “Comparison target in terms of ΔL/L and ΔIdc/Idc” of Example 1 was “Comparative Example 1,” ΔL/L of Example 1 was calculated using the following equation (1).
ΔL/Lof Example1=100×{(Lof Example1−Lof Comparative Example1)/Lof Comparative Example1} (1)
Inductance of the obtained multilayer coil at the time when a DC current was applied was measured. The inductance was measured while the applied DC current was changed from 0 to 3 A and was graphed with the horizontal axis of DC current and the vertical axis of inductance. An electric current value at the time when the inductance decreased by 30% compared to the inductance value at the time when a DC current of 0 A was applied was calculated as an Idc. An average of the Idc values of thirty multilayer coils in each example or comparative example was calculated. Table 3 shows the results. Also, ΔIdc/Idc was calculated as a rate of change in comparison to the average value of Idc of a comparison target. For example, because the “Comparison target in terms of ΔL/L and ΔIdc/Idc” of Example 1 was “Comparative Example 1,” ΔIdc/Idc of Example 1 was calculated using the following equation (2).
ΔIdc/Idcof Example1=100×{(Idcof Example1−Idcof Comparative Example1)/Idcof Comparative Example1} (2)
When ΔL/L was −30% or more and ΔIdc/Idc was 50% or more, an example or a comparative example was deemed passed and was marked “OK” in Table 3. When ΔL/L or ΔIdc/Idc was out of the above range, an example or a comparative example was marked “NG” (not good) in Table 3.
From Tables 1 to 3, it was confirmed that an example was deemed OK in the determination and had sufficiently high inductance and DC superimposition characteristic, when the interlayer region was comprised of the first magnetic element body, the axis end regions were comprised of the second magnetic element body, and the saturation magnetization of the first soft magnetic metal particles was higher than that of the second soft magnetic metal particles (Examples 1, la, 2, 3, 3a, 3b, 3c, and 3d).
Note that, in Comparative Examples 1, 2, 3, 3b, and 3d, the first soft magnetic metal particles and the second soft magnetic metal particles had the same composition and had a structure shown in
Comparative Example 1a had a structure shown in
(Each sample of Tables 4 to 6)
In each sample of Tables 4 to 6, the composition of the soft magnetic metal powder was changed to have the composition shown in Table 4 or Table 5, and the second inner-diameter magnetic element body proportion and the second outer-diameter magnetic element body proportion were changed to be as shown in Table 6. Other than the above conditions, the multilayer coil was obtained in the same manner as the samples of Tables 1 to 3 were obtained, the average particle sizes of the soft magnetic metal particles were measured, L and Idc were measured, and (ΔL/L) and (ΔIdc/Idc) were calculated. Table 4 shows the average particle size of the first soft magnetic metal particles, and Table 5 shows the average particle size of the second soft magnetic metal particles. Table 6 shows L, Idc, (ΔL/L), and (ΔIdc/Idc).
In each sample of Tables 4 to 6, “(ΔL/L)+(ΔIdc/Idc)” was also calculated as a balance indicator of “Inductance L” and “DC superimposition characteristic Idc.” Table 6 shows the results.
From Table 6 and
From Table 6, it was confirmed that, when the second outer-diameter magnetic element body proportion was 15% or more, a better balance between inductance and DC superimposition characteristic was ensured.
Comparative Example 4 had a structure shown in
(Each sample of Tables 7 to 9)
In each sample of Tables 7 to 9, the composition of the soft magnetic metal powder was changed to have the composition shown in Table 7 or Table 8. In addition, the positions of the coil conductors, the first green sheets, and the second green sheets in
From Table 9, it was confirmed that an example was deemed OK in the determination and had sufficiently high inductance and DC superimposition characteristic even when the coil conductor 5 had the three-dimensional and double helix structure, as long as the interlayer region was comprised of the first magnetic element body, the axis end regions were comprised of the second magnetic element body, and the saturation magnetization of the first soft magnetic metal particles was higher than that of the second soft magnetic metal particles (Examples 11 to 15).
(Each sample of Tables 10 to 21)
In each sample of Table 10 to Table 21, the multilayer coil was obtained in the same manner as in Example 4, except that the composition and the average particle sizes of the soft magnetic metal powder were changed to the composition and the average particle size shown in Tables 10, 11, 13, 14, 16, 17, 19, and 20. That is, each sample of Tables 10 to 21 was prepared so that the sample had a structure shown in
Regarding the obtained multilayer coil, the average particle sizes of the soft magnetic metal particles were measured, L and Idc were measured, and (ΔL/L) and (ΔIdc/Idc) were calculated in the same manner as described above. Tables 10, 13, 16, and 19 show the average particle size of the first soft magnetic metal particles, and Tables 11, 14, 17, and 20 show the average particle size of the second soft magnetic metal particles. Tables 12, 15, 18, and 21 show L, Idc, (ΔL/L), and (ΔIdc/Idc).
Additionally, in each sample of Tables 10 to 21, “Prevention of plating elongation” and “Number of short circuits” were measured using a method described below.
Evaluation of prevention of plating elongation was performed through observation of the appearance of the multilayer coil. When plating elongation was not observed at all, an example or a comparative example was evaluated as A. When a plating elongation of 50 μm or less was observed, an example or a comparative example was evaluated as B. When a plating elongation of more than 50 μm to less than 400 μm was observed, an example or a comparative example was evaluated as C. When a plating elongation of 400 μm or more was observed, an example or a comparative example was evaluated as D. Tables 12, 15, 18, and 21 show the results.
Thirty multilayer coils were prepared, and the number of the multilayer coils in which a short circuit occurred was measured using an LCR meter. An example or a comparative example was deemed good when the number of short circuits was 0/30. Tables 12, 15, 18, and 21 show the results.
From Tables 10 to 12, it was confirmed that, when the average particle size of the first soft magnetic metal particles was 1 to 6 μm (Examples 4 and 16 to 18), a better balance between inductance and DC superimposition characteristic was ensured, prevention of plating elongation was more highly evaluated, and the number of short circuits was smaller.
From Tables 10 to 12, it was confirmed that, when the average particle size of the second soft magnetic metal particles was 1 to 15 μm (Examples 4 and 20 to 23), a better balance between inductance and DC superimposition characteristic was ensured, and the number of short circuits was smaller.
From Tables 13 to 15, it was confirmed that, when the amount of P in the first soft magnetic metal particles was 10 to 40 ppm (Examples 26 to 28), prevention of plating elongation was more highly evaluated, and the number of short circuits was smaller.
From Tables 13 to 15, it was confirmed that, when the amount of P in the second soft magnetic metal particles was 100 to 6000 ppm (Examples 30 to 33), prevention of plating elongation was more highly evaluated, and the number of short circuits was smaller.
From Tables 16 to 18, it was confirmed that, when the amount of Ni in the second soft magnetic metal particles was larger than 14.0 mass % and less than 56.0 mass % (Examples 35 to 38), inductance was large, and a better balance between inductance and DC superimposition characteristic was ensured.
From Tables 19 to 21, it was confirmed that, when the amount of Si in the first soft magnetic metal particles was 3.5 to 7.5 mass % (Examples 41 to 43), a better balance between inductance and DC superimposition characteristic was ensured, prevention of plating elongation was more highly evaluated, and the number of short circuits was smaller.
From Tables 19 to 21, it was confirmed that, when the amount of Si in the second soft magnetic metal particles was 2.0 to 6.0 mass % (Examples 46 and 47), a better balance between inductance and DC superimposition characteristic was ensured, prevention of plating elongation was more highly evaluated, and the number of short circuits was smaller.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-067203 | Apr 2021 | JP | national |
