Laminated coil component

Abstract

To provide a laminated coil component that enhances a bonding strength of an external electrode.SOLUTION: A laminated coil component 1 has a laminated body 10 in which a plurality of insulating layers 31 are laminated and in which a coil 30 is provided, and an external electrode provided on a surface of the laminated body and connected to the coil. The laminated body has a first end surface 11 and a second end surface 12 opposed to each other in a length direction, a first main surface 13 and a second main surface 14 opposed to each other in a height direction orthogonal to the length direction, and a first side surface and a second side surface opposed to each other in a width direction orthogonal to the length direction and the height direction. The external electrode includes a first external electrode 21 extending from at least a portion of the first end surface to a portion of the first main surface, and a second external electrode 22 extending from at least a portion of the second end surface to a portion of the first main surface. Each of the external electrodes has a base electrode containing at least Ag and glass, and a distance of the glass diffused from an interface between the external electrode and the laminated body to the laminated body is 2.44 μm or more and 6.90 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a multilayer coil component. [Background technology]

[0002] Patent Document 1 discloses a multilayer electronic component that is manufactured by processing grooves in a green sheet, printing multiple amounts of conductive paste vertically and horizontally in the grooves, stacking multiple green sheets to form multiple coils inside, cutting and firing, and providing terminal electrodes on both ends, wherein the coil conductor made of the conductive paste has a cross-sectional shape after firing in which parts of the coil conductor overlap on both sides of the groove, and the aspect ratio t / w of the thickness t to width w of the cross section of the coil conductor is 0.7 or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-207608 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the multilayer coil component described in Patent Document 1, there is a risk that the bonding strength of the terminal electrodes corresponding to the external electrodes may be insufficient.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a multilayer coil component that can increase the bonding strength of external electrodes. [Means for solving the problem]

[0006] The laminated coil component of the present invention includes a laminate formed by stacking a plurality of insulating layers in a stacking direction and having a coil provided therein, and external electrodes provided on the surfaces of the laminate and electrically connected to the coil, the laminate having first and second end faces opposing each other in a longitudinal direction, first and second main faces opposing each other in a height direction perpendicular to the longitudinal direction, and first and second side faces opposing each other in a width direction perpendicular to the longitudinal direction and the height direction, the external electrodes including a first external electrode extending from at least a part of the first end face of the laminate to a part of the first main face, and a second external electrode extending from at least a part of the second end face of the laminate to a part of the first main face, the external electrodes including a base electrode containing at least Ag and glass, and the distance over which the glass diffuses from the interface between the external electrode and the laminate into the laminate is 2.44 μm or more and 6.90 μm or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a multilayer coil component that can increase the bonding strength of external electrodes. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a multilayer coil component according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing an example of the multilayer coil component of the present invention. [Figure 3] FIG. 3 is an exploded perspective view showing the insulating layers that constitute the multilayer coil component shown in FIG. [Figure 4] FIG. 4 is an exploded plan view showing the insulating layers that constitute the multilayer coil component shown in FIG. [Figure 5] FIG. 5 is a schematic diagram for explaining a method for measuring the diffusion distance of glass (Bi). [Figure 6] FIG. 6 is a scatter diagram plotting the diffusion distance of glass (Bi) and the adhesive strength at which the fracture probability is 1% for the multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] The laminated coil component of the present invention will be described below. However, the present invention is not limited to the following configurations and aspects, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual preferred configurations and aspects of the present invention described below.

[0010] FIG. 1 is a perspective view schematically showing an example of a multilayer coil component according to the present invention. The multilayer coil component 1 shown in Fig. 1 includes a laminate (element body) 10, a first external electrode 21, and a second external electrode 22. The laminate 10 has a roughly rectangular parallelepiped shape with six sides. The configuration of the laminate 10 will be described later; it is formed by stacking a plurality of insulating layers in the stacking direction, and has a coil provided inside. The first external electrode 21 and the second external electrode 22 are each electrically connected to the coil.

[0011] In the multilayer coil component and the laminate in this specification, the length direction, height direction, and width direction are defined as the x direction, y direction, and z direction in Fig. 1. Here, the length direction (x direction), height direction (y direction), and width direction (z direction) are perpendicular to one another. The length direction (x direction) is parallel to the stacking direction.

[0012] As shown in FIG. 1, the laminate 10 has a first end face 11 and a second end face 12 that face each other in the length direction (x direction), a first main face 13 and a second main face 14 that face each other in the height direction (y direction) perpendicular to the length direction, and a first side face 15 and a second side face 16 that face each other in the width direction (z direction) perpendicular to the length direction and height direction.

[0013] Although not shown in Fig. 1, the corners and ridges of the laminate 10 are preferably rounded. A corner is a portion where three surfaces of the laminate intersect, and a ridge is a portion where two surfaces of the laminate intersect.

[0014] The first external electrode and the second external electrode are external electrodes that extend from at least a part of the end face of the laminate to the main surface of the laminate. In the laminated coil component 1 shown in FIG. 1, the first external electrode 21 is arranged to cover a portion of the first end face 11 of the laminate 10 and extend from the first end face 11 to cover a portion of the first main surface 13. The first external electrode 21 covers a region of the first end face 11 including the ridge line portion intersecting with the first main surface 13 .

[0015] In FIG. 1 , the height of the first external electrode 21 in the portion covering the first end surface 11 of the laminate 10 is constant, but the shape of the first external electrode 21 is not particularly limited as long as it covers part of the first end surface 11 of the laminate 10. For example, on the first end surface 11 of the laminate 10, the first external electrode 21 may have an arched shape that becomes higher from the end toward the center. Furthermore, the length of the first external electrode 21 in the portion covering the first main surface 13 of the laminate 10 is constant, but the shape of the first external electrode 21 is not particularly limited as long as it covers part of the first main surface 13 of the laminate 10. For example, on the first main surface 13 of the laminate 10, the first external electrode 21 may have an arched shape that becomes longer from the end toward the center.

[0016] 1 , the first external electrode 21 may be arranged so as to further extend from the first end face 11 and the first main face 13 and cover a part of the first side face 15 and a part of the second side face 16. In this case, it is preferable that the parts of the first external electrode 21 covering the first side face 15 and the second side face 16 are both formed obliquely with respect to the ridge line intersecting with the first end face 11 and the ridge line intersecting with the first main face 13. Note that the first external electrode 21 does not have to be arranged so as to cover a part of the first side face 15 and a part of the second side face 16.

[0017] In the laminated coil component 1 shown in FIG. 1, the second external electrode 22 is arranged to cover a portion of the second end face 12 of the laminate 10 and extend from the second end face 12 to cover a portion of the first main surface 13. Similar to the first external electrode 21 , the second external electrode 22 covers a region of the second end face 12 that includes the ridge line portion that intersects with the first main face 13 .

[0018] As with the first external electrode 21, the shape of the second external electrode 22 is not particularly limited as long as it covers a portion of the second end surface 12 of the laminate 10. For example, on the second end surface 12 of the laminate 10, the second external electrode 22 may have an arched shape that becomes higher from the end toward the center. Furthermore, as long as it covers a portion of the first main surface 13 of the laminate 10, the shape of the second external electrode 22 is not particularly limited. For example, on the first main surface 13 of the laminate 10, the second external electrode 22 may have an arched shape that becomes longer from the end toward the center.

[0019] Similar to the first external electrode 21, the second external electrode 22 may be arranged so as to further extend from the second end face 12 and the first main face 13 and cover a part of the first side face 15 and a part of the second side face 16. In this case, it is preferable that the parts of the second external electrode 22 covering the first side face 15 and the second side face 16 are both formed obliquely with respect to the ridge line intersecting with the second end face 12 and the ridge line intersecting with the first main face 13. Note that the second external electrode 22 does not have to be arranged so as to cover a part of the first side face 15 and a part of the second side face 16.

[0020] Since the first external electrodes 21 and the second external electrodes 22 are arranged as described above, when the multilayer coil component 1 is mounted on a substrate, the first main surface 13 of the multilayer body 10 serves as the mounting surface.

[0021] Furthermore, unlike the form shown in Figure 1, the first external electrode may cover the entire first end face of the laminate and extend from the first end face to cover part of the first main surface, part of the second main surface, part of the first side face, and part of the second side face. In addition, the second external electrode may cover the entire second end face of the laminate and extend from the second end face to cover part of the first main surface, part of the second main surface, part of the first side surface, and part of the second side surface. In this case, any one of the first main surface, the second main surface, the first side surface, and the second side surface of the laminated body serves as the mounting surface.

[0022] The size of the multilayer coil component of the present invention is not particularly limited, but is preferably 0603 size, 0402 size, or 1005 size.

[0023] The first external electrode and the second external electrode each have a base electrode containing at least Ag (silver) and glass.

[0024] The volume ratio of the Ag powder to the total volume of Ag and glass is preferably 2% by volume or more and 90% by volume or less.

[0025] The first external electrode and the second external electrode may each have a multi-layer structure, and may have, in order from the surface side of the laminate, for example, the above-mentioned base electrode (base electrode layer), a nickel coating, and a tin coating.

[0026] The distance that the glass contained in the base electrode of the first external electrode diffuses from the interface between the first external electrode and the laminate to the laminate is not less than 2.44 μm and not more than 6.90 μm. This increases the bonding strength between the first external electrode and the laminate. For example, in a bonding strength measurement test, a bonding strength of 3N or more can be obtained, which results in a 1% probability of failure. Similarly, the distance that the glass contained in the base electrode of the second external electrode diffuses from the interface between the second external electrode and the laminate to the laminate is not less than 2.44 μm and not more than 6.90 μm. This increases the bonding strength between the second external electrode and the laminate. For example, in a bonding strength measurement test, a bonding strength of 3N or more can be obtained, which results in a 1% probability of failure. This is thought to be because when glass diffuses into the laminate, the interfaces between the first and second external electrodes and the laminate become stronger (the interfaces become blurred), that is, the glass diffused into the laminate acts as a kind of adhesive. On the other hand, if the glass does not diffuse into the laminate, it is believed that the first and second external electrodes will be more likely to peel off from the base electrode.

[0027] Furthermore, even if the first and second external electrodes are made small, the required bonding strength between the first and second external electrodes and the laminate can be ensured. Therefore, by making the first and second external electrodes small, the stray capacitance can be reduced, and the transmission coefficient S21 in the high frequency range can be improved.

[0028] If the distance over which the glass has diffused is less than 2.44 μm, breakdown may occur between the laminate and the base electrode, making it impossible to improve the bonding strength of the first and second external electrodes. If the distance over which the glass has diffused exceeds 6.90 μm, the laminate around the first or second external electrode may be broken, making it impossible to improve the bonding strength of the first or second external electrode.

[0029] The distance over which the glass is diffused is preferably 2.44 μm or more and 6.90 μm or less, more preferably 2.52 μm or more and 6.72 μm or less, and even more preferably 2.6 μm or more and 5.2 μm or less. When the distance over which the glass is diffused is 2.44 μm or more and 6.90 μm or less, it is possible to obtain a fixing force of 3 N or more which results in a breakage probability of 1%. When the distance over which the glass is diffused is 2.6 μm or more and 5.2 μm or less, it is possible to obtain a fixing force of 4 N or more which results in a breakage probability of 1%.

[0030] The distance over which the glass has diffused can be determined by subjecting a cross section of the multilayer coil component to elemental analysis using, for example, wavelength dispersive X-ray spectrometry (WDX). Specific measurement methods will be explained in the Examples section.

[0031] The distance over which the glass diffuses can be adjusted by changing the baking temperature during the formation of the base electrode, and generally, the higher the baking temperature, the greater the glass diffusion distance. Note that the glass diffusion distance is not determined solely by the baking temperature, but varies depending on the composition of the glass and insulating layer, their combination, baking conditions such as baking time, and so on. Therefore, even if the baking temperature is the same, the diffusion distance of the present invention may not necessarily be achieved.

[0032] Here, the diffusion of glass into the laminate means that the glass diffuses into the insulating layer of the laminate, and normally the glass hardly diffuses into the coil (coil conductor) of the laminate.

[0033] The glass contained in each base electrode of the first external electrode and the second external electrode preferably contains at least Bi, and the distance over which the glass is diffused is preferably the distance over which Bi is diffused. This makes it possible to easily measure the distance the glass has diffused using, for example, wavelength dispersive X-ray analysis (WDX) with Bi as a marker (analysis target).

[0034] It is more preferable that the marker that can be used to calculate the distance the glass has diffused is based on elements that are not contained in the insulating layer but are contained in the glass of the base electrode, and that one element is selected from those with high concentrations excluding Si and O. Specifically, Bi is most preferable, and if measurement is not possible with Bi, K is preferable.

[0035] Furthermore, marker components such as Bi do not usually exist alone, but coexist with other components of the glass, forming an amorphous phase in the base electrode and the insulating layer of the laminate.

[0036] The glass contained in each base electrode of the first external electrode and the second external electrode preferably contains Si in an amount of 3% by weight or more and 90% by weight or less when calculated as SiO2, B in an amount of 0.001% by weight or more and 20% by weight or less when calculated as B2O3, Bi in an amount of 0.001% by weight or more and 20% by weight or less when calculated as Bi2O3, and K in an amount of 0.001% by weight or more and 20% by weight or less when calculated as KO.

[0037] The insulating layer preferably has a magnetic phase containing at least Fe, Ni, Zn, and Cu, and a non-magnetic phase containing at least Si. The insulating layer is, for example, a sintered body such as ferrite or glass, and may contain resin. By forming the insulating layer from a composite material of a magnetic material and a non-magnetic material in this way, the glass contained in the base electrodes of the first and second external electrodes is more likely to diffuse into the laminate.

[0038] The magnetic phase is a phase having a magnetic material, and includes at least Fe, Ni, Zn, and Cu. The magnetic phase may be a phase consisting of only a magnetic material. The magnetic phase may further contain Co, Bi, Sn, Mn, and the like.

[0039] The magnetic material is preferably a Ni-Cu-Zn ferrite material, and the magnetic phase is preferably made of a Ni-Cu-Zn ferrite material. By making the magnetic phase of a Ni-Cu-Zn ferrite material, the inductance of the multilayer coil component is increased.

[0040] The Ni-Cu-Zn ferrite material may further contain additives such as Co, Bi, Sn, Mn, and the like, and unavoidable impurities.

[0041] The magnetic phase is a phase containing Fe, Ni, Zn, and Cu when analyzed by elemental analysis, and may also be a phase further containing Co, Bi, Sn, Mn, etc.

[0042] The magnetic phase preferably contains 40 mol% or more and 49.5 mol% or less of Fe in terms of Fe2O3, 2 mol% or more and 35 mol% or less of Zn in terms of ZnO, 6 mol% or more and 13 mol% or less of Cu in terms of CuO, and 10 mol% or more and 45 mol% or less of Ni in terms of NiO.

[0043] The non-magnetic phase is a phase having a non-magnetic material and contains at least Si. The non-magnetic phase may be a phase consisting of only a non-magnetic material. Examples of non-magnetic materials that constitute the non-magnetic phase include glass materials, forsterite (2MgO·SiO2), and willemite [aZnO·SiO2 (a is 1.8 or more and 2.2 or less)]. In this specification, the "non-magnetic phase containing at least Si" may be composed of only a phase containing Si, or may be composed of a phase containing Si and a phase not containing Si. An example of the phase not containing Si is a crystalline phase not containing Si.

[0044] The non-magnetic phase preferably contains a glass material, which makes it easier for the glass contained in the base electrodes of the first and second external electrodes to diffuse into the laminate.

[0045] The glass material contained in the non-magnetic phase preferably does not contain a marker (such as Bi or K) used to calculate the distance the glass has diffused.

[0046] More specifically, the glass material is preferably borosilicate glass. The borosilicate glass preferably contains 70 to 85% by weight of Si calculated as SiO2, 10 to 25% by weight of B calculated as B2O3, 0.5 to 5% by weight of alkali metal A calculated as A2O, and 0 to 5% by weight of Al calculated as Al2O3. Examples of alkali metal A include K and Na. When K is used as the marker, Na is suitable as the alkali metal A.

[0047] The non-magnetic phase may further contain forsterite (2MgO·SiO2), quartz (SiO2), or the like as a filler.

[0048] The magnetic phase and the nonmagnetic phase can be distinguished as follows. First, a cross section of the laminate of the multilayer coil component along the lamination direction is exposed by polishing, and then element mapping is performed using a scanning transmission electron microscope-energy dispersive X-ray analysis (STEM-EDX). Then, the regions where Fe, Ni, Zn, and Cu elements are present are designated as the magnetic phase, and the regions other than the magnetic phase are designated as the nonmagnetic phase, and the two phases are distinguished. The cross section along the stacking direction is a cross section as shown in FIG. 2, which will be described later.

[0049] Furthermore, the volume ratio of forsterite to the total volume of the non-magnetic phase is preferably 1.5% by volume or more and 20% by volume or less. The region containing Mg, an element contained in forsterite, is distinguished as the region containing forsterite, and the volume fraction of forsterite contained in the non-magnetic phase can be determined by measuring the area ratio of the region containing forsterite to the area of ​​the non-magnetic phase. When the non-magnetic phase is forsterite in an amount of 1.5% by volume or more and 20% by volume or less, the strength of the laminate is improved.

[0050] Next, an example of a coil built into the laminate constituting the multilayer coil component will be described. The coil is formed by electrically connecting a plurality of coil conductors stacked together with insulating layers in the stacking direction.

[0051] FIG. 2 is a cross-sectional view schematically showing an example of the laminated coil component of the present invention, FIG. 3 is an exploded perspective view schematically showing the state of insulating layers constituting the laminated coil component shown in FIG. 2, and FIG. 4 is an exploded plan view schematically showing the state of insulating layers constituting the laminated coil component shown in FIG. 2. 2 is a schematic diagram showing the insulating layers, coil conductors, connecting conductors, and the stacking direction of the laminate, and does not strictly represent the actual shapes and connections, etc. For example, the coil conductors are connected through via conductors.

[0052] As shown in FIG. 2, the multilayer coil component 1 includes a laminate 10 incorporating a coil 30 formed by electrically connecting a plurality of coil conductors 32 stacked together with insulating layers, and a first external electrode 21 and a second external electrode 22 electrically connected to the coil 30. The laminate 10 has a region where the coil conductor 32 is arranged and a region where the first connecting conductor 41 or the second connecting conductor 42 is arranged. The stacking direction of the laminate 10 and the axial direction of the coil 30 (indicated by coil axis A in FIG. 2) are parallel to the first main surface 13.

[0053] 3 and 4, the laminate 10 has insulating layer 31a, insulating layer 31b, insulating layer 31c, and insulating layer 31d as the insulating layer 31 in Fig. 2. The laminate 10 has insulating layer 35a1, insulating layer 35a2, insulating layer 35a3, and insulating layer 35a4 as the insulating layer 35a in Fig. 2. The laminate 10 has insulating layer 35b1, insulating layer 35b2, insulating layer 35b3, and insulating layer 35b4 as the insulating layer 35b in Fig. 2.

[0054] The coil 30 has a coil conductor 32a, a coil conductor 32b, a coil conductor 32c, and a coil conductor 32d as the coil conductor 32 in FIG.

[0055] The coil conductor 32a, the coil conductor 32b, the coil conductor 32c, and the coil conductor 32d are disposed on the main surfaces of the insulating layer 31a, the insulating layer 31b, the insulating layer 31c, and the insulating layer 31d, respectively.

[0056] The length of each of the coil conductors 32a, 32b, 32c, and 32d is 3 / 4 of the length of the turn of the coil 30. In other words, the number of stacked coil conductors 32 required to form three turns of the coil 30 is four. In the laminate 10, the coil conductors 32a, 32b, 32c, and 32d are stacked repeatedly as one unit (three turns).

[0057] The coil conductor 32a has a line portion 36a and a land portion 37a arranged at the end of the line portion 36a. The coil conductor 32b has a line portion 36b and a land portion 37b arranged at the end of the line portion 36b. The coil conductor 32c has a line portion 36c and a land portion 37c arranged at the end of the line portion 36c. The coil conductor 32d has a line portion 36d and a land portion 37d arranged at the end of the line portion 36d.

[0058] Via conductors 33a, 33b, 33c, and 33d are arranged in insulating layer 31a, insulating layer 31b, insulating layer 31c, and insulating layer 31d, respectively, so as to penetrate through the layers in the stacking direction.

[0059] Insulating layer 31a with coil conductor 32a and via conductor 33a, insulating layer 31b with coil conductor 32b and via conductor 33b, insulating layer 31c with coil conductor 32c and via conductor 33c, and insulating layer 31d with coil conductor 32d and via conductor 33d are repeatedly stacked as one unit (the area surrounded by dotted lines in Figures 3 and 4). As a result, land portion 37a of coil conductor 32a, land portion 37b of coil conductor 32b, land portion 37c of coil conductor 32c, and land portion 37d of coil conductor 32d are connected via via conductor 33a, via conductor 33b, via conductor 33c, and via conductor 33d. In other words, the lands of coil conductors adjacent in the stacking direction are connected to each other via the via conductors.

[0060] As a result of the above, the solenoid coil 30 built into the laminate 10 is formed.

[0061] When viewed in a plane from the stacking direction, coil 30, which is composed of coil conductors 32a, 32b, 32c, and 32d, may be circular or polygonal. When coil 30 is polygonal when viewed in a plane from the stacking direction, the diameter of a circle equivalent to the area of ​​the polygon is defined as the coil diameter of coil 30, and the axis passing through the center of gravity of the polygon and extending in the stacking direction is defined as the coil axis of coil 30.

[0062] Via conductors 33p are arranged to penetrate each of insulating layers 35a1, 35a2, 35a3, and 35a4 in the stacking direction. Land portions connected to via conductors 33p may be arranged on the main surfaces of insulating layers 35a1, 35a2, 35a3, and 35a4.

[0063] The insulating layer 35a1 with the via conductor 33p, the insulating layer 35a2 with the via conductor 33p, the insulating layer 35a3 with the via conductor 33p, and the insulating layer 35a4 with the via conductor 33p are stacked so as to overlap the coil conductor 32a and the insulating layer 31a with the via conductor 33a. As a result, the via conductors 33p are connected to each other to form a first connecting conductor 41, and the first connecting conductor 41 is exposed at the first end surface 11. As a result, the first external electrode 21 and the coil 30 (coil conductor 32a) are connected to each other via the first connecting conductor 41.

[0064] The first connecting conductor 41 preferably connects the first external electrode 21 and the coil 30 in a straight line. The first connecting conductor 41 connecting the first external electrode 21 and the coil 30 in a straight line means that the via conductors 33p constituting the first connecting conductor 41 overlap each other when viewed in a plan view from the stacking direction, and the via conductors 33p do not have to be arranged in a strict straight line.

[0065] Via conductors 33q are arranged to penetrate through insulating layers 35b1, 35b2, 35b3, and 35b4 in the stacking direction. Land portions connected to via conductors 33q may be arranged on the main surfaces of insulating layers 35b1, 35b2, 35b3, and 35b4.

[0066] The insulating layer 35b1 with the via conductor 33q, the insulating layer 35b2 with the via conductor 33q, the insulating layer 35b3 with the via conductor 33q, and the insulating layer 35b4 with the via conductor 33q are stacked so as to overlap the coil conductor 32d and the insulating layer 31d with the via conductor 33d. As a result, the via conductors 33q are connected to each other to form a second linking conductor 42, and the second linking conductor 42 is exposed at the second end surface 12. As a result, the second external electrode 22 and the coil 30 (coil conductor 32d) are connected to each other via the second linking conductor 42.

[0067] The second connecting conductor 42 preferably connects the second external electrode 22 and the coil 30 in a straight line. The second connecting conductor 42 connecting the second external electrode 22 and the coil 30 in a straight line means that the via conductors 33q constituting the second connecting conductor 42 overlap each other when viewed in a plan view from the stacking direction, and the via conductors 33q do not have to be arranged in a strict straight line.

[0068] In addition, when a land portion is connected to each of the via conductor 33p that constitutes the first connecting conductor 41 and the via conductor 33q that constitutes the second connecting conductor 42, the shapes of the first connecting conductor 41 and the second connecting conductor 42 mean the shapes excluding the land portions.

[0069] Figures 3 and 4 illustrate an example in which the number of layers of coil conductor 32 required to form three turns of coil 30 is four, i.e., the repeating shape is a 3 / 4 turn shape, but the number of layers of coil conductor 32 required to form one turn of the coil is not particularly limited. For example, the number of layers of the coil conductor for forming one turn of the coil may be two, that is, the repeating shape may be a 1 / 2 turn shape.

[0070] When viewed in a plane from the stacking direction, the coil conductors that make up the coil preferably overlap each other. Also, when viewed in a plane from the stacking direction, the coil preferably has a circular shape. Note that if the coil includes a land portion, the shape excluding the land portion (i.e., the shape of the line portion) is the shape of the coil. Furthermore, when a land portion is connected to a via conductor that constitutes the connecting conductor, the shape of the connecting conductor excluding the land portion (that is, the shape of the via conductor) is defined as the shape of the connecting conductor.

[0071] Although the coil conductor shown in FIG. 3 has a shape in which the repeated pattern is circular, the coil conductor may have a repeated pattern in the shape of a polygon such as a square. Furthermore, the repeating shape of the coil conductor may be a 1 / 2 turn shape instead of a 3 / 4 turn shape.

[0072] In the multilayer coil component having the configuration shown in FIGS. 2, 3, and 4, when the size of the multilayer coil component is 0603 size, it is preferable to design it as follows in order to improve the high frequency characteristics.

[0073] The number of turns in the coil is preferably 33 to 42. With this number of turns, the total capacitance between the coil conductors can be reduced, and the transmission coefficient S21 can be kept within a favorable range. It is also preferable that the coil length is 0.49 mm or more and 0.55 mm or less.

[0074] The width of the coil conductor is preferably 45 μm or more and 75 μm or less, and is the dimension indicated by the double-headed arrow W in FIG. The thickness of the coil conductor is preferably 3.5 μm or more and 6.0 μm or less, and is the dimension indicated by the double-headed arrow T in FIG. The distance between the coil conductors is preferably 3.0 μm or more and 5.0 μm or less, and is the dimension indicated by the double-headed arrow D in FIG.

[0075] The diameter of the land portion of the coil conductor is preferably 30 μm or more and 50 μm or less The diameter of the land portion of the coil conductor is the dimension indicated by the double arrow R in FIG.

[0076] When the first main surface of the laminate is the mounting surface, the length of the first external electrode and the length of the second external electrode that cover the first main surface of the laminate are preferably 0.20 mm or less, and more preferably 0.10 mm or more. The length of the first external electrode and the length of the second external electrode that cover the first main surface of the laminate are dimensions indicated by double-headed arrows E1 in FIG.

[0077] The multilayer coil component of the present invention is produced, for example, by the following method.

[0078] <Magnetic material manufacturing process> Fe2O3, ZnO, CuO, and NiO are weighed out to a predetermined ratio. Each oxide may contain unavoidable impurities. Next, these weighed materials are wet mixed and then pulverized to prepare a slurry. At this time, additives such as Mn3O4, Bi2O3, Co3O4, SiO2, and SnO2 may be added. The obtained slurry is then dried and pre-fired. The pre-fired temperature is, for example, 700°C or higher and 800°C or lower. The pre-fired time is, for example, 2 hours or higher and 5 hours or lower. In this way, a powdered ferrite material is prepared as a magnetic material.

[0079] The ferrite material preferably contains 40 mol% to 49.5 mol% of Fe2O3, 2 mol% to 35 mol% of ZnO, 6 mol% to 13 mol% of CuO, and 10 mol% to 45 mol% of NiO.

[0080] <Non-magnetic material manufacturing process> A powder of a non-magnetic material is weighed. A glass powder containing an alkali metal such as potassium, boron, silicon, and aluminum in a predetermined ratio is prepared as borosilicate glass. Forsterite powder is also prepared as a filler. Quartz powder may also be prepared as a filler.

[0081] The borosilicate glass preferably contains 70% to 85% by weight of Si calculated as SiO2, 10% to 25% by weight of B calculated as B2O3, 0.5% to 5% by weight of alkali metal A calculated as A2O, and 0% to 5% by weight of Al calculated as Al2O3.

[0082] The non-magnetic material preferably contains forsterite powder as a filler in an amount of 1.5% by volume or more and 20% by volume or less.

[0083] <Conductive paste manufacturing process> Ag powder is prepared and kneaded in a planetary mixer with a specified amount of solvent (e.g., eugenol), resin (e.g., ethyl cellulose), and dispersant, and then dispersed in a three-roll mill to create a conductive paste for the internal conductor.

[0084] <Green sheet manufacturing process> The magnetic material and non-magnetic material are weighed out in a predetermined ratio. Next, these weighed materials are mixed with an organic binder such as polyvinyl butyral resin, an organic solvent such as ethanol or toluene, a plasticizer, etc., and then pulverized to produce a slurry. The resulting slurry is then formed into a sheet of a predetermined thickness using a doctor blade method or the like, and then punched into a predetermined shape, such as a rectangle, to produce a green sheet. The thickness of the green sheet is preferably 20 μm or more and 30 μm or less.

[0085] The volume ratio of the magnetic material to the total volume of the magnetic material and non-magnetic material is preferably 10% by volume or more and 80% by volume or less, more preferably 15% by volume or more and 70% by volume or less, and even more preferably 20% by volume or more and 60% by volume or less. If the volume ratio of the magnetic material to the total volume of the magnetic material and non-magnetic material is less than 10% by volume, the strength of the laminate may be weakened. If the volume ratio of the magnetic material to the total volume of the magnetic material and the non-magnetic material exceeds 80 volume %, it may become difficult to sinter the magnetic material and the non-magnetic material.

[0086] <Conductor pattern formation process> First, a via hole is formed by irradiating a predetermined portion of the green sheet with a laser.

[0087] Next, a conductive paste is applied to the surface of the green sheet by screen printing or the like, filling the via holes. This forms via conductor patterns in the via holes of the green sheet, while forming coil conductor conductor patterns connected to the via conductor patterns on the surface. In this manner, a coil sheet is produced in which the coil conductor conductor patterns and the via conductor conductor patterns are formed on the green sheet. Multiple coil sheets are produced, and each coil sheet is provided with a coil conductor conductor pattern corresponding to the coil conductors shown in Figures 3 and 4 and a via conductor pattern corresponding to the via conductors shown in Figures 3 and 4.

[0088] In addition, via sheets, in which conductive patterns for via conductors are formed on green sheets, are produced separately from the coil sheets by filling via holes with conductive paste using a screen printing method, etc. Multiple via sheets are also produced, and conductive patterns for via conductors corresponding to the via conductors shown in Figures 3 and 4 are formed on each via sheet.

[0089] <Laminated block manufacturing process> The coil sheets and via sheets are stacked in the stacking direction in the order corresponding to FIGS. 3 and 4, and then thermocompression bonded to form a laminated block.

[0090] <Laminate / coil manufacturing process> First, the laminate block is cut into a predetermined size using a dicer or the like to produce individual chips.

[0091] Next, the individual chips are fired at a firing temperature of, for example, 900° C. to 920° C. for, for example, 2 hours to 4 hours.

[0092] By firing the individual chips, the green sheets of the coil sheet and via sheet become insulating layers. As a result, a laminate is produced in which multiple insulating layers are stacked in the stacking direction, in this case, the length direction. Magnetic and non-magnetic phases are formed in the laminate.

[0093] By firing the singulated chips, the conductor patterns for the coil conductors and the conductor patterns for the via conductors of the coil sheet become coil conductors and via conductors, respectively, resulting in the creation of a coil in which multiple coil conductors are stacked in the stacking direction and electrically connected through the via conductors.

[0094] This completes the production of the laminate and the coil provided inside the laminate. The stacking direction of the insulating layers and the direction of the coil axis are parallel to the first main surface, which is the mounting surface of the laminate, and in this case, are parallel along the length direction.

[0095] By firing the individual chips, the via conductor patterns of the via sheet become via conductors. As a result, first and second connecting conductors are produced, each consisting of a plurality of via conductors stacked lengthwise and electrically connected. The first connecting conductor is exposed from a first end surface of the laminate, and the second connecting conductor is exposed from a second end surface of the laminate.

[0096] The corners and ridges of the laminate may be rounded by, for example, barrel polishing.

[0097] <External electrode formation process> First, a conductive paste containing Ag powder and glass containing Bi is applied to the first end surface and the second end surface of the laminate.

[0098] The volume ratio of the Ag powder to the total volume of the Ag powder and the glass is preferably 2% by volume or more and 90% by volume or less.

[0099] The glass contained in the conductive paste preferably contains Bi in an amount of 0.001% by weight or more and 20% by weight or less when converted to Bi2O3, Si in an amount of 3% by weight or more and 90% by weight or less when converted to SiO2, B in an amount of 0.001% by weight or more and 20% by weight or less when converted to B2O3, and K in an amount of 0.001% by weight or more and 20% by weight or less when converted to KO.

[0100] Next, the resulting coating films are baked to form a base electrode on the surface of the laminate. More specifically, a base electrode is formed that extends from the first end face of the laminate to a portion of each of the first main surface, the first side face, and the second side face. Furthermore, a base electrode is formed that extends from the second end face of the laminate to a portion of each of the first main surface, the first side face, and the second side face. Here, the baking of each coating film is carried out in an oxidizing atmosphere such as air, but may also be in a reducing atmosphere.

[0101] The baking temperature for each coating is preferably 750°C or higher and 870°C or lower, more preferably 800°C or higher and 850°C or lower, and even more preferably 800°C or higher and 830°C or lower.

[0102] The baking time for each coating is preferably 10 minutes or more and 120 minutes or less, more preferably 20 minutes or more and 90 minutes or less, and even more preferably 30 minutes or more and 60 minutes or less.

[0103] Thereafter, a nickel coating and a tin coating are formed in this order on the surface of each base electrode by electrolytic plating or the like.

[0104] In this way, a first external electrode electrically connected to the coil via the first connecting conductor and a second external electrode electrically connected to the coil via the second connecting conductor are formed. In this manner, a multilayer coil component is manufactured.

[0105] The present specification discloses the following:

[0106] <1> a laminate in which a plurality of insulating layers are laminated in a lamination direction and a coil is provided inside, and an external electrode is provided on the surface of the laminate and electrically connected to the coil, the laminate has a first end face and a second end face opposing each other in a length direction, a first main face and a second main face opposing each other in a height direction perpendicular to the length direction, and a first side face and a second side face opposing each other in a width direction perpendicular to the length direction and the height direction, the external electrodes include a first external electrode extending from at least a portion of the first end face of the laminate to a portion of the first main surface, and a second external electrode extending from at least a portion of the second end face of the laminate to a portion of the first main surface, the external electrode has a base electrode containing at least Ag and glass, a distance over which the glass has diffused from the interface between the external electrode and the laminate into the laminate is 2.44 μm or more and 6.90 μm or less.

[0107] <2> a stacking direction of the laminate and a coil axis of the coil are parallel to the first main surface; <1> The multilayer coil component according to claim 1.

[0108] <3> The glass contains at least Bi, The distance through which the glass has diffused is the distance through which Bi has diffused. <1> or <2> The multilayer coil component according to claim 1.

[0109] <4> The size of the multilayer coil component is 0603 size, 0402 size, or 1005 size. <1> from <3> 10. The multilayer coil component according to claim 9, wherein the first and second layers are laminated.

[0110] <5> the insulating layer has a magnetic phase containing at least Fe, Ni, Zn, and Cu, and a non-magnetic phase containing at least Si; <1> from <4> 10. The multilayer coil component according to claim 9, wherein the first and second layers are laminated. [Example]

[0111] EXAMPLES Hereinafter, examples will be given that more specifically disclose the multilayer coil component of the present invention, but the present invention is not limited to these examples.

[0112] [Examples 1 to 6 and Comparative Examples 1 to 3] The laminates for the multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3 were produced by the following method.

[0113] <Magnetic material manufacturing process> The main components were weighed out to a ratio of 48.0 mol% Fe2O3, 30.0 mol% ZnO, 14.0 mol% NiO, and 8.0 mol% CuO. Next, these weighed components, pure water, and a dispersant were mixed in a ball mill along with PSZ media and then pulverized to produce a slurry. The resulting slurry was then dried and pre-fired at 800°C for 2 hours. In this way, a powdered ferrite material was produced as a magnetic material.

[0114] <Non-magnetic material manufacturing process> A borosilicate glass powder containing Si, B, K, and Al in predetermined proportions, and forsterite and quartz powders as fillers were prepared. The borosilicate glass powder, forsterite powder, and quartz powder were weighed out to a volume ratio of borosilicate glass:forsterite:quartz = 93:6:1. Next, these weighed materials, pure water, and a dispersant were placed in a ball mill along with PSZ media and mixed, then pulverized to produce a slurry. The resulting slurry was then dried to produce a powdered nonmagnetic material.

[0115] <Green sheet manufacturing process> The magnetic material and non-magnetic material were weighed so that the volume ratio of the magnetic material to the non-magnetic material was 60:40. Next, these weighed materials, polyvinyl butyral resin as an organic binder, and ethanol and toluene as organic solvents were placed in a ball mill along with PSZ media, mixed, and then pulverized to produce a slurry. The resulting slurry was then formed into a sheet of a predetermined thickness using a doctor blade method, and then punched into a predetermined shape to produce a green sheet.

[0116] <Conductor pattern formation process> Ag powder, a predetermined amount of solvent (eugenol), resin (ethyl cellulose), and dispersant were kneaded in a planetary mixer, and then dispersed in a three-roll mill to prepare a conductive paste. Via holes were formed in predetermined locations on the green sheet and filled with conductive paste to form via conductors, after which a coil conductor pattern was printed to obtain a coil sheet. Separately, via holes were formed in predetermined locations of the green sheet by irradiating them with a laser, and the via holes were filled with a conductive paste to form via conductors, thereby obtaining a via sheet.

[0117] <Laminated block manufacturing process> The coil sheets and via sheets were stacked in the stacking direction in the order corresponding to FIGS. 3 and 4, and then thermocompression bonded to form a laminate block.

[0118] <Laminate / coil manufacturing process> The laminate block was cut with a dicer to produce individual chips. The individual chips were then fired at 910°C for 4 hours to produce a laminate. A magnetic phase and a non-magnetic phase were formed in the laminate.

[0119] <External electrode formation process> A conductive paste for the external electrodes, containing Ag powder and Bi-containing glass, was poured into a coating film-forming tank to form a coating film of a predetermined thickness, and the portions of the laminate where the external electrodes were to be formed were immersed in this coating film. After immersion, the substrate electrodes for the external electrodes were formed by baking in the atmosphere for 1 hour at the temperature shown in Table 1. The substrate electrodes had a thickness of approximately 5 μm. In the base electrode after baking, the weight ratio of Bi to Si was Bi(Bi2O3):Si(SiO2)=0.0001 to 1:1 when converted to Bi2O3 and SiO2, respectively. Subsequently, a nickel coating and a tin coating were successively formed as plating electrodes on the base electrodes by electrolytic plating to form external electrodes.

[0120] In this manner, the multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3 were manufactured. The manufactured multilayer coil component had dimensions of 0.6 mm in the length direction, 0.3 mm in the height direction, and 0.3 mm in the width direction.

[0121] <Measurement of diffusion distance in glass> FIG. 5 is a schematic diagram illustrating a method for measuring the diffusion distance of glass (Bi). The fabricated samples (multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3) were set upright with the width direction (z direction) vertical, and the periphery of the sample was hardened with resin. The samples were polished in the width direction using a polishing machine to a depth that exposed the approximate center of the width direction. Wavelength-dispersive X-ray spectroscopy (WDX) was used to measure the distance that the glass contained in the base electrode of the external electrode (here, Bi, a component of glass) diffused from the interface between the external electrode and the laminate, as follows, for the cross section of the obtained sample. That is, as shown in FIG. 5, linear analysis of Bi element was performed in a square region spanning a 20-μm section in the x direction from a position approximately 0 μm from the external electrode 120 side to a position approximately 20 μm from the laminate 110 side, sandwiching the interface (10 μm position) between the external electrode 120 (base electrode 120a) and the laminate 110. In addition, a 20-μm section in the y direction from a position approximately 20 μm from the bottom surface of the laminate 110 was performed. Specifically, the square region was divided into 256 × 256 unit square regions, and the detected amount of Bi element was measured for each unit square. The detected amount of Bi element in the x direction was defined as the average of the detected amount of Bi element for every 256 unit squares in the y direction, every other unit square in the x direction. The measurement area in the y direction was limited to the area where the interface between the external electrode and the laminate was present. The area in the y direction where no interface was present was excluded from the measurement results. The distance from the interface to the point where the X-ray intensity became flat (background) was defined as the distance through which the glass (Bi) diffused. A five-point moving average of the detected amount of Bi element in the x direction was calculated, and the first point in the +x direction (direction from the external electrode toward the laminate) where the difference from the previous point was within 3% was defined as the background. The results are shown in Table 1 below. The position of the interface can be determined from the observed image of the chip cross section. Naturally, the position of the interface also has a range (varies) in the x direction in most cases, but in that case, it is sufficient to obtain the average of the x coordinate values ​​of the interface determined by each y coordinate value. For example, it is preferable to divide the chip cross section image into the same unit square regions (20 μm square region divided into 256 × 256 regions) as used in the detection of Bi element by WDX described above, perform image analysis, and calculate the average of the x coordinate values ​​of the interface determined by each y coordinate value. In this measurement, the position of the interface coincided with the peak position of the X-ray intensity, so for convenience the position where the X-ray intensity peaked was taken as the position of the interface between the base electrode and the laminate.

[0122] <Measurement of external electrode bond strength> Fifteen samples each of the fabricated samples (multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3) were prepared, and each sample was mounted on a glass epoxy substrate. The adhesive strength was measured using a bond tester. The results were plotted as a Weibull plot to determine the adhesive strength at which the probability of failure was 1%. The failure modes of the 15 evaluated samples were also evaluated to determine which mode was dominant. The failure modes were divided into failure between the laminate and the base electrode (Ag), failure between the base electrode (Ag) and the plated electrode, failure in the laminate around the external electrode, and failure at the fillet. The results are shown in Table 1 below.

[0123] [Table 1]

[0124] Fig. 6 shows a scatter diagram plotting the diffusion distance of glass (Bi) and the bonding strength at which the fracture probability is 1% for the multilayer coil components of Examples 1 to 6 and Comparative Examples 1 to 3. Fig. 6 shows an approximation line passing through four points for Comparative Example 2 and Examples 1 to 3, and an approximation line passing through four points for Examples 4 to 6 and Comparative Example 3. These approximation lines reveal that the bonding strength at which the fracture probability is 1% is 3 N or more when the diffusion distance of glass (Bi) is 2.44 μm or more and 6.90 μm or less.

[0125] As shown in Table 1 and FIG. 6, in Examples 1 to 6, in which the diffusion distance of Bi, i.e., glass, was 2.44 μm or more and 6.90 μm or less, a bonding strength of 3 N or more was obtained, which resulted in a fracture probability of 1%, and the fracture mode was mainly fracture in the laminate or fillet around the external electrode, so it is believed that sufficient bonding strength was obtained. In Examples 1 to 6 and Comparative Examples 1 to 3, the diffusion length of the glass (Bi) is the average value of 15 samples.

[0126] Generally, a multilayer coil component is considered to be able to withstand the mounting environment in the market if the adhesive force exceeds 2N, which results in a 1% probability of failure; however, to allow for some margin, we evaluated the bonding strength using 1.5 times that amount, or 3N, as the standard. [Explanation of symbols]

[0127] 1. Multilayer coil components 10, 110 laminate 11 First end surface 12 Second end face 13 First main surface 14 Second main surface 15 First aspect 16 Second aspect 21 1st external electrode 22 2nd external electrode 30 coils 31, 31a, 31b, 31c, 31d, 35a, 35a1, 35a2, 35a3, 35a4, 35b, 35b1, 35b2, 35b3, 35b4 insulating layers 32, 32a, 32b, 32c, 32d Coil conductors 33a, 33b, 33c, 33d, 33p, 33q via conductors 36a, 36b, 36c, 36d line section 37a, 37b, 37c, 37d Land section 41 First connecting conductor 42 Second connecting conductor 120 External electrode 120a Base electrode

Claims

1. a laminate in which a plurality of insulating layers are laminated in a lamination direction and a coil is provided inside, and an external electrode is provided on the surface of the laminate and electrically connected to the coil, the laminate 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 perpendicular to the length direction, and a first side surface and a second side surface that face each other in a width direction perpendicular to the length direction and the height direction, the external electrodes include a first external electrode extending from at least a portion of the first end face of the laminate to a portion of the first main surface, and a second external electrode extending from at least a portion of the second end face of the laminate to a portion of the first main surface, the external electrode has a base electrode containing at least Ag and glass; a distance over which the glass has diffused from the interface between the external electrode and the laminate into the laminate is 2.44 μm or more and 6.90 μm or less.

2. The laminated coil component according to claim 1 , wherein a lamination direction of the laminate and a coil axis of the coil are parallel to the first main surface.

3. The glass contains at least Bi, 3. The multilayer coil component according to claim 1, wherein the distance through which the glass is diffused is the distance through which Bi is diffused.

4. 3. The laminated coil component according to claim 1, wherein the size of the laminated coil component is 0603 size, 0402 size, or 1005 size.

5. 3. The multilayer coil component according to claim 1, wherein the insulating layer has a magnetic phase containing at least Fe, Ni, Zn, and Cu, and a non-magnetic phase containing at least Si.

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