Electronic component and method for manufacturing the same

Abstract

To provide an electronic component provided with an external electrode having excellent bonding strength with an external terminal or a plating layer, and a manufacturing method for the electronic component.SOLUTION: A coil component 1 includes an insulating substrate 10, an external electrode 22 provided on the substrate 10, and a functional portion (conductor) electrically connected to the external electrode 22. The external electrode 22 includes a conductive metal portion F made of a metal material, a glass agglomerated region G, and a non-conductive metal oxide H.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The disclosure of this specification relates to electronic components and a method for manufacturing electronic components.

Background Art

[0002] Conventional electronic components such as inductors and capacitors include a substrate, a functional part provided in the substrate, and external electrodes electrically connected to the ends of the functional part. For example, an inductor includes a coil conductor as a functional part, and a capacitor includes a pair of electrodes that generate capacitance as a functional part. The external electrodes of such electronic components are formed, for example, by applying a conductive paste containing conductive metal particles to the surface of the substrate and performing heat treatment. Glass may be added to the conductive paste for the purpose of increasing the adhesion strength between the substrate and the external electrodes. For example, Patent Document 1 discloses a chip inductor including external electrodes formed from a conductive paste to which glass powder is added.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an external electrode is formed by heat-treating a conductive paste containing glass, since glass having a high affinity for the substrate is interposed between the external electrode and the substrate, the adhesion strength between the substrate and the external electrode can be improved. However, when the conductive paste contains glass, glass also exists on the surface of the external electrode, and there is a risk that the bonding strength between an external terminal connected to the surface of the external electrode or a plating layer formed on the surface of the external electrode and the external electrode may decrease.

[0005] One object of the present invention is to provide an electronic component having an external electrode excellent in bonding strength with an external terminal or a plating layer, and a method for manufacturing the electronic component. Other objects of the present invention will be clarified through the description of the entire specification. The invention disclosed in this specification may solve problems grasped other than the description in the column of "Problems to be Solved by the Invention".

Means for Solving the Problems

[0006] A coil component according to an embodiment of the present invention includes an insulating substrate, an external electrode provided on the substrate, and a functional portion electrically connected to the external electrode. This external electrode includes a metal portion made of a metal material and having conductivity, glass, and a non-conductive metal oxide.

[0007] In one embodiment of the present invention, the external electrode has an inner peripheral surface facing the surface of the substrate and an outer peripheral surface on the opposite side of the inner peripheral surface, and is configured such that the metal portion is exposed from the outer peripheral surface. The coil component includes a glass layer provided so as to contact the surface of the substrate and the inner peripheral surface of the external electrode.

[0008] In one embodiment of the present invention, in a region of 3 / 4 or more of the outer peripheral surface, the metal portion may be exposed.

[0009] In one embodiment of the present invention, the external electrode has a glass aggregation region where the glass is aggregated, and the glass aggregation region may contact the metal oxide.

[0010] In one embodiment of the present invention, the metal oxide may be an oxide of a transition metal.

[0011] In one embodiment of the present invention, the electronic component may further include a plating layer provided on the outer peripheral surface of the external electrode.

[0012] In one embodiment of the present invention, the functional portion may include a conductor wound around the coil axis.

[0013] In one embodiment of the present invention, the functional part may include a pair of electrodes that generate capacitance.

[0014] In one embodiment of the present invention, the glass does not contain lead and has a melting point of 500°C or lower.

[0015] In one embodiment of the present invention, the substrate includes an oxide.

[0016] One embodiment of the present invention relates to a circuit board including the electronic component described in any of the above. Further, one embodiment of the present invention relates to an electronic device including the above circuit board.

[0017] A method for manufacturing an electronic component according to one embodiment of the present invention includes a step of preparing a substrate made of an insulating material and having a functional part made of metal, a step of preparing a conductive paste including conductive metal particles, non-conductive metal oxides, and glass, a step of forming the conductive paste layer on the surface of the substrate, and a step of heat-treating the conductive paste layer.

[0018] In one embodiment of the present invention, the volume ratio of the metal oxide contained in the conductive paste may be 2% or more.

[0019] In one embodiment of the present invention, the volume ratio of the glass to the metal oxide contained in the conductive paste may be 2.0 or more and 5.3 or less.

[0020] In one embodiment of the present invention, by the step of heat-treating the conductive paste layer, an external electrode containing metal particles and a glass layer provided between the substrate and the external electrode may be formed.

[0021] In one embodiment of the present invention, the average particle diameter of the plurality of metal particles may be 1 μm or more and 10 μm or less.

[0022] In one embodiment of the present invention, the plurality of metal particles may include high aspect ratio particles having an aspect ratio of 3 or more.

[0023] In one embodiment of the present invention, the average of the minimum radius of curvature of the high aspect ratio particles may be 3 μm or less.

Advantages of the Invention

[0024] According to the present invention, there are provided an electronic component including an external electrode having excellent bonding strength with both a substrate and an external terminal or a plating layer, and a method for manufacturing the electronic component.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0026] Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. Note that the same reference numerals are given to common components in a plurality of drawings. It should be noted that each drawing is not necessarily drawn to an accurate scale for the sake of convenience of explanation.

[0027] Referring to FIGS. 1 to 4, an overview of the coil component 1 according to an embodiment of the present invention will be described. The coil component 1 is a kind of electronic component to which the present invention is applicable. FIG. 1 is a perspective view schematically showing the coil component 1. As shown in FIG. 1, the coil component 1 includes a base body 10, a conductor 25 provided inside the base body 10, an external electrode 21 provided on the surface of the base body 10, and an external electrode 22 provided at a position spaced apart from the external electrode 21 on the surface of the base body 10. In the coil component 1, the conductor 25 is a functional part. The conductor 25 is an example of the "functional part" in the claims. A glass layer 23 is provided between the external electrode 21 and the base body 10, and between the external electrode 22 and the base body 10, respectively. The glass layer 23 is composed of glass, for example, low melting point lead-free glass.

[0028] In this specification, unless otherwise understood from the context, the "length" direction, "width" direction, and "height" direction of the coil component 1 are the "L-axis" direction, "W-axis" direction, and "T-axis" direction of FIG. 1, respectively.

[0029] The coil component 1 is mounted on the mounting substrate 2a. Two lands 3 are provided on the mounting substrate 2a. The coil component 1 can be mounted on the mounting substrate 2a by joining the external electrodes 21 and 22 and the lands 3 corresponding to the external electrodes 21 and 22, respectively. Thus, the circuit board 2 includes the coil component 1 and the mounting substrate 2a on which the coil component 1 is mounted. Electronic devices on which this circuit board 1 can be mounted include smartphones, tablets, game consoles, servers, automotive electrical components, and various other electronic devices.

[0030] The coil component 1 can be applied to inductors, transformers, filters, reactors, and various other coil components having external electrodes 21 and 22 on the surface of the base body 10. The coil component 1 can also be applied to coupled inductors, choke coils, and various other magnetically coupled coil components. The use of the coil component 1 is not limited to those explicitly stated in this specification.

[0031] The base body 10 is made of an insulating material. The base body 10 is composed of, for example, a ceramic material such as ferrite, a soft magnetic metal material, or a mixture thereof. In one embodiment, the base body 10 is mainly composed of a magnetic material and is configured in a rectangular parallelepiped shape. The base body 10 of the coil component 1 according to one embodiment of the present invention is formed such that the length dimension (dimension in the L-axis direction) is 1.0 mm to 4.5 mm, the width dimension (dimension in the W-axis direction) is 0.5 mm to 3.2 mm, and the height dimension (dimension in the T-axis direction) is 0.5 mm to 5.0 mm. The dimensions of the base body 10 are not limited to the dimensions specifically described in this specification. In this specification, when referring to a "rectangular parallelepiped" or "rectangular parallelepiped shape", it does not mean only a "rectangular parallelepiped" in a strictly mathematical sense.

[0032] The base body 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f. The outer surface of the base body 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b respectively form the surfaces at both ends in the height direction, the first end surface 10c and the second end surface 10d respectively form the surfaces at both ends in the length direction, and the first side surface 10e and the second side surface 10f respectively form the surfaces at both ends in the width direction.

[0033] As shown in FIG. 1, since the first main surface 10a is on the upper side of the base body 10, the first main surface 10a may be referred to as the "upper surface". Similarly, the second main surface 10b may be referred to as the "lower surface". Since the coil component 1 is arranged such that the first main surface 10a faces the circuit board, the first main surface 10a may also be referred to as the "mounting surface". When referring to the up and down directions of the coil component 1, the up and down directions in FIG. 1 are used as a reference.

[0034] In one or more embodiments, the substrate 10 is composed of an insulating material having a high affinity for the glass constituting the glass layer 23. The fact that the substrate 10 has a "high affinity" for the glass means that the surface of the substrate 10 has good wettability with respect to the glass and this glass easily adheres to the surface of the substrate 10. When the substrate 10 contains an oxide, the substrate 10 has a high affinity for the glass constituting the glass layer 23. Examples of the oxide contained in the substrate 10 include the oxide of Fe contained in the ferrite material and the oxide film formed on the surface of the metal magnetic particles. In the illustrated embodiment, the substrate 10 includes a plurality of first metal magnetic particles 11 and a plurality of second metal magnetic particles 12. An oxide film is formed on the surface of each of the plurality of first metal magnetic particles 11 and the plurality of second metal magnetic particles 12, and adjacent particles are bonded to each other via this oxide film. In other words, the substrate 10 is composed of a plurality of first metal magnetic particles 11 and a plurality of second metal magnetic particles 12 bonded to each other via an oxide film. The substrate 10 may contain a non-magnetic material.

[0035] The plurality of first metal magnetic particles 11 have an average particle size larger than that of the plurality of second metal magnetic particles 12. That is, the average particle size of the plurality of first metal magnetic particles 11 (hereinafter referred to as "first average particle size") is different from the average particle size of the plurality of second metal magnetic particles 12 (hereinafter referred to as "second average particle size"). The first average particle size is, for example, 30 μm, and the second average particle size is, for example, 2 μm. The first average particle size may be larger than 30 μm or smaller than 30 μm. The second average particle size may be larger than 2 μm or smaller than 2 μm. In one embodiment of the present invention, the substrate 10 may further include a plurality of third metal magnetic particles (not shown) having an average particle size different from the first average particle size and the second average particle size. The third average particle size, which is the average particle size of the third metal magnetic particles, may be smaller than the first average particle size and the second average particle size. In the following description, in this specification, when it is not necessary to distinguish the first metal magnetic particles 11, the second metal magnetic particles 12, and the third metal magnetic particles from each other, the first metal magnetic particles 11, the second metal magnetic particles 12, and the third metal magnetic particles included in the magnetic substrate 10 may be collectively referred to as "metal magnetic particles". The "average particle size" of the metal magnetic particles included in the substrate 10 is obtained by cutting the magnetic substrate along its thickness direction (T-axis direction) to expose a cross section, obtaining a particle size distribution based on a photograph taken of the cross section with a scanning electron microscope (SEM) at a magnification of 1000 to 2000 times, and determining it based on the particle size distribution thus obtained. For example, the 50% value (D50) of the particle size distribution obtained based on the SEM photograph can be used as the average particle size of the metal magnetic particles.

[0036] The first metal magnetic particles 11 and the second metal magnetic particles 12 are made of various soft magnetic materials. The first metal magnetic particles 11 are mainly composed of, for example, Fe. Specifically, the first metal magnetic particles 11 are (1) metal particles such as Fe and Ni, (2) crystalline alloy particles such as alloys containing Fe, Si, and Cr, alloys containing Fe, Si, and Al, alloys containing Fe and Ni, etc., (3) amorphous alloy particles such as alloys containing Fe, Si, Cr, B, and C, alloys containing Fe, Si, Cr, and B, etc., or (4) mixed particles in which these are mixed. The composition of the metal magnetic particles contained in the magnetic substrate 10 is not limited to the above. The first metal magnetic particles 11 contain, for example, 85 wt% or more of Fe. Thereby, a magnetic substrate 10 having excellent magnetic permeability can be obtained. The composition of the second metal magnetic particles 12 may be the same as or different from the composition of the first metal magnetic particles 11. When the magnetic substrate 10 contains a plurality of third metal magnetic particles (not shown), the composition of the third metal magnetic particles may be the same as or different from the composition of the first metal magnetic particles 11, similar to the composition of the second metal magnetic particles 12.

[0037] The surface of each of the metal magnetic particles may be coated with an insulating film. This insulating film is formed of, for example, a material having excellent insulating properties such as glass. This insulating film is formed, for example, on the surface of the first metal magnetic particles 11 by mixing the first metal magnetic particles 11 and glass material powder in a friction mixer (not shown). The insulating film formed from the glass material adheres to the surface of the first metal magnetic particles 11 by compressive friction action in the friction mixer. The glass material may contain ZnO and P2O5. This insulating film can be formed from various glass materials. The insulating film may be formed from alumina powder, zirconia powder, or powders of other oxides having excellent insulating properties instead of or in addition to the glass material. The thickness of the insulating film is, for example, 100 nm or less.

[0038] The second metal magnetic particles 12 may be coated with an insulating film different from the insulating film of the first metal magnetic particles 11. This insulating film may be an oxide film formed by oxidation of the second metal magnetic particles 12. The thickness of this insulating film is, for example, 20 nm or less. This insulating film may be an oxide film formed on the surface of the second metal magnetic particles 12 by heat-treating the second metal magnetic particles 12 in an atmospheric atmosphere. This insulating film may be an oxide film containing oxides of Fe and elements contained in the second metal magnetic particles 12 other than this. This insulating film may be an iron phosphate film formed on the surface of the second metal magnetic particles 12 by putting the second metal magnetic particles 12 into phosphoric acid and stirring. The insulating film of the first metal magnetic particles 11 may be an oxide film formed by oxidation of the first metal magnetic particles 11, and the insulating film of the second metal magnetic particles 12 may be a separately provided coating film regardless of the oxidation of the second metal magnetic particles 12.

[0039] The coil component 1 according to an embodiment of the present invention has a conductor 25 as a functional part. The conductor 25 is formed to have a predetermined pattern. In the illustrated embodiment, the conductor 25 is wound around the coil axis Ax. The conductor 25 has, for example, an elliptical shape, a meander shape, a linear shape, or a combination of these shapes in a plan view. The conductor 25 may have any shape other than the above, and may be, for example, a spiral shape.

[0040] The conductor 25 is formed of Cu, Ag, or a conductive material other than these. The entire surface of the conductor 25 other than the end face 25a2 and the cross section 25b2 may be covered with an insulating film. As shown in the figure, when the conductor 25 is wound around the coil axis Ax in a plurality of turns, each turn of the conductor 25 may be separated from another adjacent turn. In this case, the base body 10 is interposed between the adjacent turns.

[0041] In one or more embodiments, the conductor 25 is formed of a metallic material and provided within the substrate 10. As the metallic material for the conductor 25, for example, Ag, Pd, Cu, Al, or an alloy thereof can be used. For example, the conductor 25 has a winding portion 25a spirally wound around a coil axis Ax extending along the thickness direction (T-axis direction), and lead conductors 25b respectively drawn out from both ends of the winding portion 25a to connect both ends to the external electrodes 21 and 22. The conductor 25 is connected to the external electrodes 21 and 22 at the end faces 25b1 of the lead conductors 25b. In the illustrated embodiment, the coil axis Ax intersects the upper surface 10a and the lower surface 10b, but does not intersect the first end face 10c, the second end face 10d, the first side face 10e, and the second side face 10f. In the illustrated embodiment, the winding portion 25a has a plurality of conductor patterns C11 to C15. The conductor patterns C11 to C15 extend along the planar direction orthogonal to the coil axis Ax and are spaced apart from each other in the direction of the coil axis Ax. Each of the conductor patterns C11 to C15 is electrically connected to an adjacent conductor pattern via a via (not shown). Thus, the winding portion 25a of the conductor 25 is constituted by the conductor patterns C11 to C15 and vias. The coil axis Ax of the present invention is not limited to intersecting the upper surface 10a and the lower surface 10b shown in FIG. 2. For example, it may intersect the first end face 10c and the second end face 10d, or may intersect the first side face 10e and the second side face 10f.

[0042] In one embodiment of the present invention, the external electrode 21 is provided on a part of the first main surface 10a, the second main surface 10b, the first end surface 10c, the first side surface 10e, and the second side surface 10f of the substrate 10. The external electrode 22 is provided on a part of the first main surface 10a, the second main surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f of the substrate 10. The external electrode 21 and the external electrode 22 are arranged to be separated from each other. The shapes and arrangements of the external electrodes 21 and 22 are not limited to the illustrated examples. For example, the external electrode 21 and the external electrode 22 may be provided so as to be in contact with only the second main surface 10b. The external electrode 21 may be provided so as to be in contact with the second main surface 10b and other surfaces (for example, one or more surfaces among the first end surface 10b, the first side surface 10e, and the second side surface 10f). Similarly, the external electrode 22 may be provided so as to be in contact with the second main surface 10b and other surfaces (for example, one or more surfaces among the second end surface 10c, the first side surface 10e, and the second side surface 10f). As described above, glass layers 23 are provided between the external electrode 21 and the substrate 10 and between the external electrode 22 and the substrate 10, respectively. FIGS. 3 and 4 show the glass layer 23 formed between the external electrode 22 and the substrate 10. Hereinafter, the external electrode 22 and the glass layer 23 between the external electrode 22 and the substrate 10 will be described with reference to FIGS. 3 and 4. However, the description of the external electrode 22 applies to the external electrode 21 as well unless there are special circumstances, and the description of the glass layer 23 between the external electrode 22 and the substrate 10 applies to the glass layer 23 provided between the external electrode 21 and the substrate 10 as well unless there are special circumstances.

[0043] The external electrode 22 has an inner peripheral surface 22a and an outer peripheral surface 22b facing the surface of the substrate 10. In the illustrated embodiment, the inner peripheral surface 22a of the external electrode 22 faces the first main surface 10a, the second main surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f. The outer peripheral surface 22b of the external electrode 22 refers to the surfaces of the external electrode 22 other than the inner peripheral surface 22a. The outer peripheral surface 22b of the external electrode 22 includes the surface of the external electrode 22 opposite to the surface of the substrate 10. A plating layer may be provided on the outer peripheral surface 22b of the external electrode 22. The external electrode 22 is connected to an external terminal (for example, an external lead terminal or a land 3) via the plating layer or directly on the outer peripheral surface 22b. In the illustrated embodiment, a plating layer 26 is provided on the outer peripheral surface 22b of the external electrode 22. The inner peripheral surface and the outer peripheral surface of the external electrode are also configured and arranged in the same manner as the inner peripheral surface 22a and the outer peripheral surface 22b of the external electrode, respectively. That is, the inner peripheral surface of the external electrode 21 is the inner peripheral surface that faces the first main surface 10a, the second main surface 10b, the second end surface 10c, the first side surface 10e, and the second side surface 10f of the substrate 10, and the outer peripheral surface of the external electrode 21 is the surface other than the inner peripheral surface. The glass layer 23 is in contact with the inner peripheral surface 21a of the external electrode 21 and the surface of the substrate 10. The glass layer 23 is not provided on the end surface 25b1 of the lead-out conductor 25b of the conductor 25, and the end surface 25b1 of the conductor 25 is electrically connected to the external electrode 21. The thickness of the glass layer 23 is, for example, in the range of 0.2 μm to 2 μm.

[0044] The glass layer 23 is made of glass, for example, low melting point lead-free glass. The low melting point lead-free glass is, for example, a low melting point glass material containing one or more of SiO2, B2O3, V2O3, GeO2, and Bi2O3. In one or more embodiments of the present invention, the melting point of the low melting point lead-free glass constituting the glass layer 23 is 500° C. or lower. If the glass contains lead, the melting point of the glass often exceeds 500° C., and from the perspective of environmental problems, it is desirable that the electronic component does not contain lead. Therefore, the glass 23 is preferably composed of low melting point lead-free glass. Further, the low melting point lead-free glass constituting the glass layer 23 is 10 at the temperature during sintering of the metal particles contained in the external electrodes 21 and 22.4 ~10 7 Preferably has a viscosity of P (Poise).

[0045] As shown in FIG. 4, the external electrode 22 can include a metal part F made of a metal material and having conductivity, a glass aggregation region G where glass has aggregated, and a non-conductive metal oxide H. The external electrode 22 may have a slight void (not shown) inside. The void of the external electrode 22 is reduced or eliminated by increasing the heat treatment time in the manufacturing process of the external electrode described later.

[0046] In one or more embodiments of the present invention, the non-conductive metal oxide H is an oxide of a transition metal. Specifically, as the metal oxide H, TiO2, ZnO, Al2O3, ZrO2, HfO2, Fe2O3, Co3O4, Nb2O5, Ta2O5, NiO, CuO, etc. can be used. As the metal oxide H, it is preferable to use a material that does not form a solid solution with the metal particles F in the temperature range of the heat treatment step of the metal particles F described later (i.e., the temperature range in which the metal particles F sinter). Such a metal oxide H has a high affinity with the low melting point lead-free glass constituting the glass layer 23 in the temperature range during sintering of the metal particles F compared to the metal particles F. Here, "having a high affinity" means that the surface of the metal oxide H has good wettability with respect to the low melting point lead-free glass and the low melting point lead-free glass adheres easily. The average particle size of the metal oxide H is, for example, 1 μm or more and 5 μm or less. The metal oxide H has a melting point higher than that of the low melting point lead-free glass.

[0047] As shown in the figure, the external electrode 22 has a plurality of glass aggregation regions G where low-melting-point lead-free glass has aggregated. The low-melting-point lead-free glass that constitutes the glass aggregation region G is the same material as the low-melting-point lead-free glass that constitutes the glass layer 23. As described above, since the metal oxide H has a high affinity with the low-melting-point lead-free glass that constitutes the glass layer 23 in the temperature range during the sintering of the metal particles F, in the heat treatment process of the metal particles F, the low-melting-point lead-free glass contained in the conductive paste that becomes the external electrode 22 softens and easily moves to the periphery of the metal oxide H. For this reason, the glass aggregation region G is formed in contact with the metal oxide H. In the external electrode 22, the glass aggregation region G is arranged so as to surround a part or all of one or more metal oxides H.

[0048] At least a part of the outer peripheral surface 22b of the external electrode 22 is exposed with a metal part F made of a metal material and having conductivity. For example, on the outer peripheral surface 22b, the total area of the regions where the metal part F is exposed is 3 / 4 or more of the area of the outer peripheral surface 22b. At locations on the outer peripheral surface 22b where the metal part F is not exposed, for example, a glass aggregation region G where low-melting-point lead-free glass has aggregated or a metal oxide H may be exposed. It is not necessary for the glass aggregation region G to be completely exposed from the outer peripheral surface 22b. When the glass aggregation region G is exposed from the outer peripheral surface 22b, the area of the region where the glass aggregation region G is exposed in the area of the outer peripheral surface 22b is less than 1 / 4 of the area of the outer peripheral surface 22b. The ratio of the area occupied by the glass aggregation region G on the outer peripheral surface 22b is less than the area occupied by the glass aggregation region G on the inner peripheral surface 22a. The glass aggregation region G existing on the outer peripheral surface 22b exists in an island shape on the outer peripheral surface 22b, different from the layer-like glass layer 23 that covers the inner peripheral surface 21a. That is, on the outer peripheral surface 22b, the glass aggregation region G exists as a plurality of discrete island-like regions.

[0049] In the illustrated embodiment, a plating layer 26 is provided on the outer peripheral surface 22b of the external electrode 22. The plating layer 26 can cover the entire outer peripheral surface 22b of the external electrode 22 (that is, the entire region of the surface of the external electrode 22 that does not face the surface of the base body 10). The plating layer 26 is composed of, for example, Ni or Sn. In addition to Ni and Sn, the plating layer 26 may be composed of a metal or alloy that serves as a barrier layer exhibiting corrosion resistance against heat during soldering, or may be composed of a metal or alloy having good solder wetting properties. In the illustrated embodiment, the plating layer 26 is a single layer, but the plating layer 26 may have a multilayer structure composed of a plurality of layers. The metal portion F exposed from the outer peripheral surface 22b of the external electrode 22 is in contact with the plating layer 26 and may be metallically bonded to the plating layer 26. The plating layer 26 may not be provided on the outer peripheral surface 22b of the external electrode 22. When the plating layer 26 is not provided on the outer peripheral surface 22b of the external electrode 22, the external electrode 22 may be directly connected to an external terminal (for example, an external lead terminal or a land 3). In this case, the metal portion F exposed from the outer peripheral surface 22b of the external electrode 22 may be metallically bonded to the metal material constituting the external terminal. The plating layer 26 and the metal material constituting the external terminal have poor adhesion to the low melting point lead-free glass present on the outer peripheral surface 22b. There is no glass aggregation region G composed of a low melting point lead-free glass having poor adhesion to the plating layer 26 or the metal material constituting the external terminal on the outer peripheral surface 22b, or even if there is a glass aggregation region G, the region where the glass aggregation region G exists is less than 1 / 4 of the entire outer peripheral surface 22b. Therefore, the bonding strength between the outer peripheral surface 22b of the external electrode 22 and the plating layer 26 or the external terminal can be increased.

[0050] Next, a method for manufacturing the coil component 1 according to one or more embodiments will be described. In one or more embodiments of the present invention, the base body 10 of the coil component 1 is manufactured by a sheet lamination method of laminating insulating sheets. When manufacturing the coil component 1 by the sheet lamination method, first, an insulating sheet is prepared. The insulating sheet is created from a slurry obtained by kneading metal magnetic particles made of a soft magnetic metal material and a resin using various sheet forming machines such as a doctor blade type sheet forming machine. As the metal magnetic particles, for example, mixed particles obtained by mixing relatively large-diameter metal magnetic particles that become the first metal magnetic particles 11 after heat treatment and relatively small-diameter metal magnetic particles that become the second metal magnetic particles 12 after heat treatment are used. As the resin kneaded with the metal magnetic particles, for example, a resin excellent in thermal decomposability such as polyvinyl butyral (PVB) resin and easy to degrease can be used. When the base body 10 contains ferrite, ferrite powder is used instead of the metal magnetic particles.

[0051] The insulating sheet is cut into a predetermined shape, and a through hole penetrating in the thickness direction is formed at a predetermined position. Next, a plurality of unfired conductor patterns that will each become the conductor pattern C11 after firing are formed by applying a conductor paste to the insulating sheet cut into a predetermined shape by a known method such as screen printing. By applying the conductor paste to another insulating sheet in the same manner, a plurality of unfired conductor patterns that will each become the conductor patterns C12 to C15 after firing are formed. When forming the unfired conductor pattern, the conductor paste is embedded in the through hole of the insulating sheet to become an unfired via (unfired via). The conductor paste that becomes the material of the conductor patterns C11 to C15 is obtained, for example, by kneading Ag, Pd, Cu, Al, or an alloy thereof and a resin.

[0052] An unburned conductor pattern, an unburned via, an insulating sheet on which an unburned conductor plate corresponding to the conductor patterns C11 to C15 manufactured as described above is formed, and an insulating sheet on which no conductor is formed are laminated to obtain a mother laminate. The insulating sheets on which no conductor is formed are disposed at the upper and lower ends of the mother laminate. The insulating sheets disposed at the upper and lower ends of this mother laminate become an upper cover layer (reference numeral omitted) between the conductor 25 and the upper surface 10a and a lower cover layer (reference numeral omitted) between the conductor 25 and the lower surface 10b after firing.

[0053] Next, a chip laminate is obtained by singulating the mother laminate using a cutting machine such as a dicing machine or a laser processing machine. Next, this chip laminate is degreased, and a heat treatment is performed on the degreased chip laminate. The heat treatment of the chip laminate is performed, for example, at 400°C to 900°C for 20 minutes to 120 minutes. By this heat treatment, the insulating sheet and the conductor paste are fired, and a substrate 10 containing the conductor 25 inside is obtained.

[0054] Next, the surface of the substrate 10 where the end face 25b1 of the lead-out conductor 25b of the conductor 25 is exposed is smoothed, and oxides are removed from the end face 25b1 and the end face 25b2. To smooth the surface of the substrate 10, for example, polishing is performed on the surface of the substrate 10 using an abrasive. The surface of the substrate 10 may be etched after polishing. As the abrasive, for example, one having a particle size smaller than that of the first metal magnetic particles 11 is selected. If the average particle size of the first metal particles 11 is 30 μm, an abrasive with a particle size of 25 μm may be selected. The etching is performed, for example, by plasma etching. The etching can use plasma etching and any etching that can remove oxides on the surface of the substrate 10 other than this.

[0055] Next, a conductive paste containing conductive metal particles, non-conductive metal oxide H, and a low-melting-point lead-free glass is prepared. The conductive paste may contain TEOS (tetraethoxysilane), GeO2 (germanium dioxide), B2O3 (boron oxide), or the like as a sintering aid. Then, a conductive paste layer is formed by applying the conductive paste that will become the external electrodes 21 and 22 onto the surface of the substrate 10 by a printing method or other known method.

[0056] The metal particles contained in the conductive paste may include a plurality of types of metal particles. In one or more embodiments of the present invention, the metal particles may be mixed particles including a plurality of first metal particles having an aspect ratio of 2 or less and a plurality of second metal particles having an aspect ratio of 3 or more. In one or more embodiments of the present invention, the aspect ratio of each of the plurality of second metal particles is in the range of 3 to 15. In this specification, the aspect ratio of the first metal particle means the ratio of the dimension in the short axis direction to the dimension in the long axis direction of the first metal particle in the cross section in the thickness direction of the external electrode 22. The aspect ratio of the second metal particle has the same meaning. In this specification, the dimension in the long axis direction of the first metal particle and the second metal particle is referred to as the maximum particle diameter of the first metal particle and the second metal particle, respectively, and the dimension in the short axis direction of the first metal particle and the second metal particle is referred to as the minimum particle diameter. That is, the aspect ratio of the first metal particle means the value obtained by dividing the maximum particle diameter of the first metal particle by the minimum particle diameter, and the aspect ratio of the second metal particle means the value obtained by dividing the maximum particle diameter of the second metal particle by the minimum particle diameter. In this specification, particles having an aspect ratio of 2 or less are called low aspect ratio particles, and particles having an aspect ratio of 3 or more are called high aspect ratio particles. Since high aspect ratio particles have a shape that is not spherical, they may also be called non-spherical particles. According to this definition, the first metal particle is a low aspect ratio particle, and the second metal particle is a high aspect ratio particle (non-spherical particle). The shapes of the high aspect ratio particles (non-spherical particles) include a flat shape, a scale shape, needle-like particles, and other shapes. Particles having an aspect ratio greater than 2 and less than 3 are particles in the middle between low aspect ratio particles and high aspect ratio particles from the viewpoint of the aspect ratio, and are therefore called medium aspect ratio particles in this specification. The external electrode 22 may include medium aspect ratio particles. The medium aspect ratio particles are included in a small ratio. For example, when the total of the low aspect ratio particles, the medium aspect ratio particles, and the high aspect ratio particles is 100 vol%, the medium aspect ratio particles may be included in the external electrode 22 at a volume ratio of less than 10 vol%.

[0057] In the cross-section in the thickness direction of the external electrode 22, the average of the maximum particle diameters of the second metal particles may be larger than the average of the maximum particle diameters of the first metal particles. For example, the average of the maximum particle diameters of the second metal particles may be 1 μm to 10 μm, and the average of the maximum particle diameters of the first metal particles may be 0.1 μm to 10 μm.

[0058] At both ends in the major axis direction of the second metal particles, the radius of curvature of the outer diameter of the second metal particles is minimized. In one or more embodiments of the present invention, the average of the minimum radii of curvature (i.e., the radii of curvature at the ends in the major axis direction of the second metal particles) of the second metal particles is in the range of 0.1 μm to 3 μm. The average of the minimum radii of curvature of the second metal particles is obtained by cutting the external electrode 21 or the external electrode 22 to expose a cross-section (for example, exposing a cross-section cut along the TL plane as shown in FIG. 4 described later), and obtaining the minimum radius of curvature of each of the second metal particles included in the captured image obtained by photographing the cross-section with a scanning electron microscope (SEM) at a magnification of 2000 times, and the average value of the minimum radii of curvature of each of the second metal particles thus obtained is used.

[0059] When the total of the low aspect ratio particles, the medium aspect ratio particles, and the high aspect ratio particles is 100 vol%, the volume ratio of the low aspect ratio particles (the first metal particles) is, for example, 0 vol% to 70 vol%, and the ratio of the high aspect ratio particles (the second metal particles) is, for example, 30 vol% to 100 vol%. The first metal particles and the second metal particles are heat-treated in the manufacturing process of the coil component 1. By this heat treatment, the first metal particles and the second metal particles are sintered, and the first metal particles with each other, the second metal particles with each other, and the first metal particles and the second metal particles are metallically bonded.

[0060] The first metal particles and the second metal particles are composed of, for example, a metal material excellent in conductivity such as Ag, Cu, Au, Pd, Pt, Ni, an alloy of these metal materials, or a mixture thereof. The first metal particles and the second metal particles may contain metals of the same component. In the illustrated embodiment, both the first metal particles and the second metal particles are composed of Ag. The first metal particles and the second metal particles may contain different metals from each other, or may be composed only of different metals from each other. Even when the first metal particles and the second metal particles contain different metals from each other, the first metal particles and the second metal particles are metallically bonded to each other by the heat treatment described later, and the joint portion between the first metal particles and the second metal particles is alloyed. In this case, it is preferable to select a combination of the metal contained in the first metal particles and the metal contained in the second metal particles such that the bonding strength is stronger than the metallic bond between the same kind of metals. The bonding strength of the alloy formed by the combination of different metals is obvious to those skilled in the art. Both the first metal particles and the second metal particles have a melting point higher than that of the low-melting-point lead-free glass.

[0061] Next, a heat treatment is performed on the substrate 10 on which the conductive paste layer is formed. By this heat treatment, the metal particles contained in the conductive paste layer are sintered to form a metal part F, and the conductive paste layer becomes the external electrodes 21 and 22. The heat treatment is performed, for example, at 550°C to 800°C for 30 minutes to 60 minutes. Further, the heat treatment may be performed in a low-oxygen atmosphere or a reducing atmosphere according to the material of the metal particles.

[0062] In this heat treatment, when the conductive paste layer is heated, the low-melting-point lead-free glass contained in the conductive paste layer melts. The melted low-melting-point lead-free glass is likely to move within the conductive paste layer. Since the low-melting-point lead-free glass has a higher affinity for oxides than for metals, the melted low-melting-point lead-free glass moves toward the metal oxide H within the conductive paste layer. Also, when the plurality of first metal particles and second metal particles contained in the conductive paste layer sinter to form the metal part F in the heat treatment, the conductive paste layer shrinks, and the low-melting-point lead-free glass is extruded toward the outside of the conductive paste layer. At this time, since the low-melting-point lead-free glass has a high affinity for the substrate 10 containing the oxide formed by oxidizing the metal magnetic particles, the melted low-melting-point lead-free glass is likely to move toward the substrate 10. As a result, a glass layer 23 derived from the low-melting-point lead-free glass contained in the conductive paste layer is formed between the external electrode 21 formed by the heat treatment and the surface of the substrate 10. Similarly, a glass layer is also formed between the external electrode 22 and the surface of the substrate 10. The low-melting-point lead-free glass contained in the conductive paste layer also moves to the side opposite to the substrate 10 during the aggregation of the conductive paste layer. However, the conductive paste layer contains the metal oxide H that has a high affinity for the low-melting-point lead-free glass, and the metal oxide H hardly moves from its original position even during the aggregation of the conductive paste layer. Therefore, the movement of the melted low-melting-point lead-free glass to the side opposite to the substrate 10 is suppressed by the metal oxide H. Thus, since the conductive paste contains the metal oxide H, the melted low-melting-point lead-free glass can be held around the metal oxide H. As a result, it is possible to suppress the movement of the melted low-melting-point lead-free glass to the outer peripheral surface 22b side of the external electrode 22 during the heat treatment process. As a result, it is possible to prevent the outer peripheral surface 21b of the external electrode 22 from being covered with the low-melting-point lead-free glass, and it is easy to expose the metal part F made of a metal material and having conductivity from the outer peripheral surface 22b.

[0063] When fabricating the external electrodes 21 and 22, the volume ratio of the metal oxide H contained in the conductive paste to the entire conductive paste can be 2.0 or more. If the amount of the metal oxide H in the conductive paste is too small, it becomes impossible to suppress the movement of the low melting point lead-free glass melted in the heat treatment to the outer peripheral surfaces of the external electrodes 21 and 22 (for example, the outer peripheral surface 22b of the external electrode 22), and a large amount of the low melting point lead-free glass moves to the outer peripheral surfaces of the external electrodes 21 and 22.

[0064] In one or more embodiments of the present invention, the volume ratio of the low melting point lead-free glass to the metal oxide H contained in the conductive paste is set to be 2.0 or more and 5.3 or less. The reason for setting the lower limit of the low melting point lead-free glass with respect to the metal oxide H to 2.0 is that when the ratio of the low melting point lead-free glass with respect to the metal oxide H is less than 2.0, the low melting point lead-free glass melted in the heat treatment is trapped by the metal oxide H and cannot move to the surface of the substrate 10, and there is a possibility that the glass layer 23 may not be formed with a sufficient thickness between the external electrodes 21 and 22 and the substrate 10. If the glass layer 23 is not formed with a sufficient thickness, the bonding strength between the external electrodes 21 and 22 and the substrate 10 may become weak. Therefore, in one or more embodiments of the present invention, by setting the volume ratio of the low melting point lead-free glass to the metal oxide H contained in the conductive paste to 2.0 or more, the external electrodes 21 and 22 and the substrate 10 are firmly bonded by the glass layer 23. Further, when the ratio of the low melting point lead-free glass with respect to the metal oxide H is greater than 5.3, the amount of the low melting point lead-free glass in the conductive paste becomes excessive, and the movement of the excessive low melting point lead-free glass during the heat treatment cannot be suppressed by the metal oxide H. For this reason, when the conductive paste layer contains an excessive amount of the low melting point lead-free glass, a large amount of the low melting point lead-free glass moves not only in the direction toward the substrate 10 but also in the direction toward the outer peripheral surfaces of the external electrodes 21 and 22. As a result, the bonding strength between the outer peripheral surfaces of the external electrodes 21 and 22 and the plating layer 26 or the external terminal is weakened. Therefore, in one or more embodiments of the present invention, by setting the ratio of the low melting point lead-free glass with respect to the metal oxide H to 5.3 or less, the amount of the low melting point lead-free glass moving to the outer peripheral surfaces of the external electrodes 21 and 22 is suppressed, and thereby the external electrodes 21 and 22 and the plating layer 26 or the external terminal are firmly bonded.

[0065] In one or more embodiments of the present invention, the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles contained in the conductive paste is 12.1 or more and 29.8 or less. When the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles is less than 12.1, the amount of the low melting point lead-free glass is insufficient to form the glass layer 23. As a result, the bonding strength between the external electrodes 21 and 22 and the substrate 10 becomes weak. In one or more embodiments of the present invention, by setting the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles to 12.1 or more, a glass layer 23 with a sufficient thickness is formed, and the glass layer 23 firmly bonds the external electrodes 21 and 22 to the substrate 10. If the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles becomes too large, the resistance value of the external electrodes 21 and 22 will increase (that is, the electrical resistance between the external electrodes 21 and 22 and the external terminals connected to the external electrodes 21 and 22 will increase), which is not desirable. In particular, when the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles is greater than 29.8, the amount of the low melting point lead-free glass becomes excessive, and a large amount of glass moves to the outer peripheral surfaces of the external electrodes 21 and 22 during the heat treatment. When a large amount of glass is present on the outer peripheral surfaces of the external electrodes 21 and 22, the bonding strength between the external electrodes 21 and 22 and the plating layer 26 or the external terminals is weakened. Therefore, in one or more embodiments of the present invention, by setting the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles to 29.8 or less, the amount of the low melting point lead-free glass moving to the outer peripheral surfaces of the external electrodes 21 and 22 is suppressed, thereby firmly bonding the external electrodes 21 and 22 to the plating layer 26 or the external terminals.

[0066] After the external electrodes 21 and 22 are formed by the above heat treatment, a plating layer 26 is formed on the outer peripheral surfaces of the external electrodes 21 and 22 by a plating method. Although the metal material constituting the plating layer 26 has poor adhesion to the low melting point lead-free glass, by adjusting the content ratio of the low melting point lead-free glass in the conductive paste as described above, there is almost no glass aggregation region G where the low melting point lead-free glass has aggregated on the outer peripheral surfaces of the external electrodes 21 and 22, or even if it exists, the area of the region where the glass aggregation region G is exposed on each of the outer peripheral surfaces of the external electrodes 21 and 22 can be made less than 1 / 4 of the area of each outer peripheral surface. Therefore, it is possible to prevent or suppress the bonding strength between the plating layer 26 and the external electrodes 21 and 22 from being reduced by the glass aggregation region G derived from the low melting point lead-free glass. As a result, the plating layer 26 and the external electrodes 21 and 22 can be firmly joined.

[0067] Through the above steps, the coil component 1 is manufactured. The manufactured coil component 1 has the external electrodes 21 and 22 soldered to the lands 3 of the mounting substrate 2a, respectively. When the plating layer 26 is formed on the outer peripheral surfaces of the external electrodes 21 and 22, each of the external electrodes 21 and 22 is connected to the land 3 via the plating layer 26. In this case, since the plating layer 26 is firmly joined to the outer peripheral surfaces of the external electrodes 21 and 22, the detachment of the coil component 1 due to the peeling of the plating layer 26 from the external electrodes 21 and 22 is suppressed. Therefore, the coil component 1 can be firmly joined to the mounting substrate 2a. When the plating layer 26 is not formed on the outer peripheral surfaces of the external electrodes 21 and 22, the external electrodes 21 and 22 are connected to the land 3 on their respective outer peripheral surfaces. As described above, there is no glass aggregation region G derived from the low melting point lead-free glass on the outer peripheral surfaces of the external electrodes 21 and 22, or even if it exists, the amount is small. Therefore, the reduction in the bonding strength between the external electrodes 21 and 22 and the land 3 due to the glass aggregation region G is prevented or suppressed. Thus, the detachment of the coil component 1 due to the peeling of the external electrodes 21 and 22 from the land 3 is suppressed. Therefore, the coil component 1 can be firmly joined to the mounting substrate 2a. In this way, the bonding strength of the coil component 1 to the mounting substrate 2a can be improved.

[0068] As described above, the external electrodes 22 of the coil component 1 contain the non-conductive metal oxide H. Such an external electrode containing the metal oxide H is formed by heat-treating a conductive paste containing the non-conductive metal oxide H. In this heat treatment, the low-melting-point lead-free glass in the conductive paste becomes easy to melt and move. Since the low-melting-point lead-free glass has a higher affinity with the substrate 10 containing the oxide than the metal particles, a part of the melted low-melting-point lead-free glass moves toward the surface of the substrate 10 to form a glass layer 23 between the external electrodes 21, 22 and the substrate 10. On the other hand, since the external electrodes of conventional general coil components do not contain the metal oxide H, the low-melting-point lead-free glass melted in the heat treatment also moves to the outer peripheral surface side of the external electrodes 21, 22.

[0069] With reference to FIG. 5, a conventional coil component and the coil component 1 according to one or more embodiments of the present invention will be described in comparison. FIG. 5 is a cross-sectional view schematically showing a partial cross-section of a conventional coil component. In FIG. 5, a cross-section of a region corresponding to FIG. 4 of the conventional coil component is shown so that the conventional coil component can be understood in comparison with the coil component 1 shown in FIG. 4. As shown in FIG. 5, the conventional coil component includes a base 10p, an external electrode 22p, and a glass layer 23p provided between the base 10p and the external electrode 22p. The external electrode 22p is different from the external electrode 22 of the coil component 1 in that it does not contain the metal oxide H. The base 10p and the glass layer 23p are each configured in the same manner as the base 10 and the glass layer 23 of the coil component 1. In the conventional coil component, since the external electrode 22p does not contain the metal oxide H, in the heat treatment when manufacturing the external electrode 22p, the molten low-melting-point lead-free glass moves to the outer peripheral surface of the external electrode 22p without being trapped by the metal oxide H. Therefore, as shown in FIG. 5, many glass aggregation regions G are generated on the outer peripheral surface of the external electrode 22p as compared with the outer peripheral surface 22b of the external electrode 22 of the coil component 1. Further, inside the external electrode 22p, a void S is formed by the aggregation of the space generated by the movement of the low-melting-point lead-free glass to the outer peripheral surface of the external electrode 22p during the heat treatment. Different from the external electrodes 21 and 22 of the coil component 1 according to the embodiment of the present invention, the external electrode 22p of the conventional coil component does not contain the non-conductive metal oxide H, so the low-melting-point lead-free glass dissolved in the heat treatment easily moves to the surface of the external electrode 22p. For this reason, the external electrode 22p has a large number of voids S and a large volume. By increasing the heating time for generating the external electrode 22p of the conventional coil component, the volume of the void S can be reduced by grain growth. However, even if grain growth is promoted by long-time heat treatment, a large number of voids S remain in the external electrode 22p. The void S formed inside the external electrode 22p in this way causes a decrease in the strength of the external electrode 22p. In addition, many glass aggregation regions G are generated on the outer peripheral surface of the external electrode 22p. Due to this glass aggregation region G, the adhesion strength between the external terminal connected to the surface of the external electrode 22p or the plating layer 26p formed on the surface of the external electrode 22p and the external electrode 22p decreases.

[0070] In contrast, the external electrodes 21 and 22 of the coil component 1 according to one or more embodiments of the present invention are made of a first metal particle, a second metal particle, and a metal material formed by sintering them, and contain a metal oxide H having a higher affinity for a low melting point lead-free glass than the conductive metal part F. Therefore, when heat-treated, the low melting point lead-free glass that has melted moves to the surface side of the base 10 and aggregates around the metal oxide H. Thus, since the metal oxide H is contained in the external electrodes 21 and 22, the low melting point lead-free glass can be held around the metal oxide H during the heat treatment. As a result, compared with a conventional coil component in which the external electrodes 21 and 22 do not contain the metal oxide H, the movement of the low melting point lead-free glass to the outer peripheral surfaces of the external electrodes 21 and 22 can be suppressed. For this reason, the amount of the glass aggregation region G generated on the outer peripheral surfaces of the external electrodes 21 and 22 of the coil component 1 in one or more embodiments of the present invention is less than the amount of the glass aggregation region G generated on the outer peripheral surface of the external electrode 22p of the conventional coil component. Therefore, a coil component 1 having external electrodes 21 and 22 with excellent bonding strength to an external terminal (for example, an external lead terminal or a land 3) or a plating layer 26 can be obtained.

[0071] In one or more embodiments of the present invention, the area of the region where the metal part F is exposed from the outer peripheral surface 22b is set to be 3 / 4 or more of the area of the outer peripheral surface 22b. Thereby, since the metal part F of the external electrode 22 and the metal material constituting the plating layer 26 can be metallically bonded in a region of 3 / 4 or more of the area of the outer peripheral surface 22b, the bonding strength between the plating layer 26 formed on the outer peripheral surface 22b of the external electrode 22 and the external electrode 22 can be increased. In addition, since the area of the region where the glass aggregation region G exposed in the area of the outer peripheral surface 22b is less than 1 / 4 of the area of the outer peripheral surface 22b, the electrical resistance between the external electrode 22 and the plating layer 26 can be reduced compared with a conventional coil component in which more glass aggregation regions G are generated on the outer peripheral surface 22b.

[0072] In one or more embodiments of the present invention, the external electrode 22 may contain second metal particles having an aspect ratio of 3 or more. Further, the average of the minimum curvature radii of the second metal particles may be 0.1 μm or more and 3 μm or less. In such second metal particles, since the energy required for metal bonding is small at both ends in the major axis direction, it is possible to facilitate the formation of metal bonds between the metal particles at both ends in the major axis direction of the second metal particles.

[0073] In one or more embodiments of the present invention, the external electrodes 21 and 22 may be formed from a conductive paste containing 2% or more of metal oxide H by volume ratio. If the amount of metal oxide H in the conductive paste is too small, it becomes impossible to suppress the movement of the low-melting-point lead-free glass melted in the heat treatment to the outer peripheral surfaces of the external electrodes 21 and 22 (for example, the outer peripheral surface 22b of the external electrode 22), and a large amount of low-melting-point lead-free glass moves to the outer peripheral surfaces of the external electrodes 21 and 22.

[0074] In one or more embodiments of the present invention, the external electrodes 21 and 22 may be formed from a conductive paste having a volume ratio of metal oxide H to low-melting-point lead-free glass of 2.0 or more and 5.3 or less. By setting the volume ratio of the low-melting-point lead-free glass to the metal oxide H contained in the conductive paste to 2.0 or more, the low-melting-point lead-free glass can easily move to the surface of the substrate 10 in the heat treatment of the conductive paste, and thereby a glass layer 23 can be formed on the surface of the substrate 10. As a result, the glass layer 23 can firmly bond the external electrodes 21 and 22 to the substrate 10. Further, by setting the ratio of the low-melting-point lead-free glass to the metal oxide H to 5.3 or less, the amount of the low-melting-point lead-free glass moving to the outer peripheral surfaces of the external electrodes 21 and 22 can be suppressed. The metal materials constituting the plating layer 26 and the land 3 have poor adhesion to the low-melting-point lead-free glass (or the glass aggregation region G where the low-melting-point lead-free glass aggregates). Therefore, by suppressing the amount of the low-melting-point lead-free glass moving to the outer peripheral surfaces of the external electrodes 21 and 22, the bonding strength between the external electrodes 21 and 22 and the plating layer 26 or the external terminals (for example, external lead terminals and land 3) can be made higher.

[0075] In one or more embodiments of the present invention, the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles contained in the conductive paste may be 12.1 or more and 29.8 or less. By setting the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles to 12.1 or more, a glass layer 23 with a sufficient thickness can be formed, and the glass layer 23 can firmly bond the external electrodes 21, 22 and the base 10. Further, by setting the volume ratio of the low melting point lead-free glass to the total volume of the first metal particles and the second metal particles to 29.8 or less, the amount of the low melting point lead-free glass moving to the outer peripheral surfaces of the external electrodes 21, 22 can be suppressed, and thereby the external electrodes 21, 22 and the plating layer 26 or the external terminals can be firmly bonded.

[0076] The coil component 1 is an example of an electronic component to which the present invention is applicable, and the present invention can be applied to various types of coil components other than the coil component 1. For example, the present invention can also be applied to a wound type coil component. With reference to FIG. 6, a coil component 101 according to another embodiment of the present invention will be described. The coil component 101 shown in FIG. 6 is a wound type inductor in which a coil conductor 125 (winding 125) is wound around a base 110. As shown in the figure, the coil component 101 includes a base 110, a coil conductor 125, a first external electrode 121, and a second external electrode 122.

[0077] The magnetic base 110 has a bobbin 111, a rectangular parallelepiped flange 112a provided at one end of the bobbin 111, and a rectangular parallelepiped flange 112b provided at the other end of the bobbin 111. The coil conductor 125 is wound around the bobbin 111. The coil conductor 125 has a conducting wire made of a metal material with excellent conductivity and an insulating coating covering the periphery of the conducting wire. The first external electrode 121 is provided along the lower surface of the flange 112a, and the second external electrode 122 is provided along the lower surface of the flange 112b. Glass layers 123 are provided between the surface of the flange 112a of the base 110 and the external electrode 121 and between the surface of the flange 112b of the base 110 and the external electrode 122, respectively.

[0078] The glass layer 123 is composed of glass, like the glass layer 23, and is composed of, for example, a low melting point lead-free glass. The substrate 110 is composed of an insulating material having a high affinity with the glass constituting the glass layer 123, like the substrate 10.

[0079] Next, an example of a method for manufacturing the coil component 101 will be described. First, the substrate 110 is manufactured. First, metal magnetic particles are kneaded with a resin to obtain a mixed resin composition. Next, this mixed resin composition is put into a mold having a cavity with a shape corresponding to the magnetic substrate 110, and a molded body is manufactured by pressurizing the mixed resin composition in this mold at a predetermined molding pressure while heating. Next, this molded body is degreased, and the substrate 110 is obtained by performing a heat treatment on the degreased molded body. The heating time in this heat treatment is, for example, 20 minutes to 120 minutes, and the heating temperature is, for example, 550 to 850°C.

[0080] Next, a conductive paste that will become the external electrodes 121 and 122 is applied to the flanges 112a and 112b of the substrate 110 obtained by the above heat treatment process to form a conductive paste layer. The same conductive paste as the conductive paste used for forming the external electrodes 21 and 22 of the coil component 1 can be used. That is, as the conductive paste used for manufacturing the external electrodes 121 and 122, it contains conductive first metal particles and second metal particles, non-conductive metal oxide H, and low melting point lead-free glass. Next, a heat treatment is performed on the substrate 110 on which this conductive paste layer is applied and formed. By this heat treatment, the first metal particles and the second metal particles contained in the conductive paste layer are sintered to form a metal part having conductivity, and the conductive paste layer becomes the external electrodes 121 and 122. The heat treatment is performed, for example, at 550°C to 800°C for 30 minutes to 60 minutes. In this heat treatment, the low melting point lead-free glass contained in the conductive paste moves to the surfaces of the flanges 112a and 112b, and a glass layer 123 is generated between the surface of the flange 112a and the external electrode 121 and between the surface of the flange 112b and the external electrode 122.

[0081] Next, a coil conductor 125 is wound around the substrate 110 obtained by the above heat treatment process, one end of this coil conductor 125 is connected to the first external electrode 121, and the other end is connected to the second external electrode 122. Thus, the coil component 101 is obtained.

[0082] The shape and arrangement of each component of the coil conductor 101 are not limited to those shown in FIG. 6. For example, the magnetic substrate 110 may be a ring-shaped toroidal core. The coil component 101 may be a toroidal coil including a ring-shaped substrate 110 (toroidal core 110) and a coil conductor 125 wound around the magnetic substrate 110. Further, it may have an exterior portion that covers the wound coil conductor 125. The exterior portion may contain resin or glass, and may also contain a filler. As the filler, ferrite powder or metal magnetic particles may be used.

[0083] The external electrodes 121 and 122 of the coil component 101 also contain a non-conductive metal oxide H, similar to the external electrodes 21 and 22 of the coil component 1. Therefore, when heating the conductive paste that becomes the external electrodes 121 and 122, a low-melting-point lead-free glass can be held around the metal oxide H. Thus, compared with a conventional coil component in which the external electrodes do not contain the metal oxide H, the amount of low-melting-point lead-free glass generated on the outer peripheral surfaces of the external electrodes 121 and 122 can be suppressed. For this reason, it is possible to suppress the deterioration of the bonding strength between the external electrodes 121 and 122 due to the glass aggregation region formed from the low-melting-point lead-free glass and the plating layer provided on the outer peripheral surfaces of these external electrodes 121 and 122 or the external terminals joined to the outer peripheral surfaces of the external electrodes 121 and 122. Further, since the substrate 110 is made of an insulating material having a high affinity with the low-melting-point lead-free glass, a glass layer 123 is generated between the surface of the flange 112a and the external electrode 121 and between the surface of the flange 112b and the external electrode 122, and the external electrodes 121 and 122 can be firmly joined to the flanges 112a and 112b by this glass layer 123.

[0084] Next, with reference to FIG. 7, a coil component 201 according to another embodiment of the present invention will be described. The illustrated coil component 201 includes a base body 210, a coil conductor 225 provided in the base body 210, an external electrode 221 electrically connected to one end of the coil conductor 225, and an external electrode 222 electrically connected to the other end of the coil conductor 225. A glass layer 223 is provided between the surface of the base body 210 and the external electrode 221 and between the surface of the base body 210 and the external electrode 222, respectively. Similar to the glass layer 23, the glass layer 223 is made of glass, for example, low melting point lead-free glass. Similar to the base body 10, the base body 210 is made of an insulating material having a high affinity with the glass constituting the glass layer 223.

[0085] Next, a method for manufacturing the coil component 201 will be described. First, metal magnetic particles are prepared. Next, the metal magnetic particles 30 and the resin composition are mixed to produce a slurry (mixture). Next, a coil conductor prepared in advance is placed in a molding die, the above slurry is put into the molding die in which the coil conductor is installed, and a molding pressure is applied to obtain a molded body containing the coil conductor inside. Next, the molded body is heat-treated. This molded body is heat-treated, for example, at 550°C to 850°C for 20 minutes to 120 minutes. Thereby, a base body 210 having a coil conductor 225 inside is obtained. Next, a conductive paste layer is formed by applying a conductive paste that becomes the external electrodes 221 and 222 to the surface of the base body 210 obtained as described above. As this conductive paste, the same conductive paste used for forming the external electrodes 21 and 22 of the coil component 1 can be used. That is, the conductive paste used for manufacturing the external electrodes 221 and 222 contains conductive first metal particles and second metal particles, non-conductive metal oxide H, and low-melting-point lead-free glass. Next, a heat treatment is performed on the base body 210 on which the conductive paste layer is applied and formed. By this heat treatment, the first metal particles and the second metal particles contained in the conductive paste layer are sintered to form a conductive metal part, and the conductive paste layer becomes the external electrodes 221 and 222. The heat treatment is performed, for example, at 550°C to 800°C for 30 minutes to 60 minutes. In this heat treatment, the low-melting-point lead-free glass contained in the conductive paste moves to the surface of the base body 210, and a glass layer 223 is formed between the surface of the base body 210 and the external electrode221 and between the surface of the base body 210 and the external electrode 222. Thus, the coil component 201 is obtained.

[0086] The external electrodes 221 and 222 of the coil component 201 also contain a non-conductive metal oxide H, similar to the external electrodes 21 and 22 of the coil component 1. Therefore, when heating the conductive paste that becomes the external electrodes 221 and 222, low-melting-point lead-free glass can be held around the metal oxide H. Thus, compared with a conventional coil component in which the external electrodes do not contain the metal oxide H, the amount of low-melting-point lead-free glass generated on the outer peripheral surfaces of the external electrodes 221 and 222 can be suppressed. Deterioration of the bonding strength between the external electrodes 221 and 222 due to the glass aggregation region formed from the low-melting-point lead-free glass and the plating layer provided on the outer peripheral surfaces of the external electrodes 221 and 222 or the external terminals joined to the outer peripheral surfaces of the external electrodes 221 and 222 can be suppressed. Also, since the base 210 is made of an insulating material having a high affinity with the low-melting-point lead-free glass, a glass layer 223 is generated between the surface of the base 210 and the external electrode 221 and between the surface of the base 210 and the external electrode 222, and the external electrodes 221 and 222 can be firmly joined to the base 210 by this glass layer 223.

[0087] The dimensions, materials, and arrangements of the respective components described in the various embodiments above are not limited to those explicitly described in each embodiment, and each of these components can be deformed to have any dimensions, materials, and arrangements that can be included in the scope of the present invention. Also, components not explicitly described in this specification can be added to each of the above embodiments, or a part of the components described in each embodiment can be omitted.

[0088] For example, an electronic component according to an embodiment of the present invention may be a capacitor including a pair of electrodes that generate capacitance as functional parts. In this case, the external electrode 21 is electrically connected to one electrode of the functional part, and the external electrode 21 is electrically connected to the other electrode of the functional part. When the electronic component according to an embodiment of the present invention is a capacitor, as the oxide contained in the base, for example, ceramic materials such as alumina (Al2O3), zirconia, and barium titanate (BaO3Ti) can be used.

Example

[0089] Next, examples of the present invention will be described. Samples to be evaluated were prepared as follows. An insulating sheet was produced from a slurry obtained by kneading metal magnetic particles and polyvinyl butyral (PVB) resin using a doctor blade type sheet forming machine, and this insulating sheet was heated at 550 ° C for 60 minutes to obtain a fired body of the insulating sheet. The fired body of this insulating sheet was cut to produce 24 insulator substrates of the same shape. Next, a conductive paste containing Ag particles, a low melting point lead-free glass (TiO2 - SiO2 - B2O3 - based glass), and a metal oxide (CuO) was applied to each of the insulator substrates by screen printing to form a conductive paste layer. As the Ag particles, mixed particles obtained by mixing spherical Ag particles with an aspect ratio of approximately 1 and an average particle diameter of 0.2 μm and Ag particles with an aspect ratio of 10 and an average minimum curvature radius of 0.3 at a weight ratio of 4:6 were used. Among these mixed particles, the spherical Ag particles with an average particle diameter of 0.2 μm are an example of the first metal particles, and the Ag particles with an aspect ratio of 10 and an average minimum curvature radius of 0.3 are an example of the second metal particles. Then, at a temperature of 0.7Tm (Tm is the melting point of Ag), the insulator substrate coated with the conductive paste was heated for 60 minutes to sinter the Ag particles contained in the conductive paste, and the conductive paste layer was made into an Ag sintered layer. Next, a copper wire with a diameter of 180 μm was prepared, and one end vicinity of the copper wire was pressure-bonded to the Ag sintered layer at a pressure of 250 kPa, and the conductive paste and the copper wire were solid-phase bonded at 650 ° C. Then, the copper wire was bent in a direction perpendicular to the conductive paste layer, the other end of the bent copper wire was connected to a tension gauge, and the copper wire was pulled in a direction perpendicular to the conductive paste by the tension gauge to measure the 90-degree peel strength. As the tension gauge, a Mitutoyo 546 series dial tension gauge DTG-30N (30 - 300 - 30 gf range) was used. The above measurements were performed on 24 samples (sample A1 to sample A24) with different ratios of Ag metal particles, low melting point lead-free glass, and metal oxide contained in the conductive paste. The ratios of Ag metal particles, low melting point lead-free glass, and metal oxide contained in the conductive paste in each sample, as well as the measurement results of the bonding strength in each sample, were as shown in Table 1 below. Note that in Table 1, sample number A15 is missing.In each sample, since an Ag sintered layer is formed on the insulator substrate and a copper wire is solid-phase bonded to this Ag sintered layer, peeling can occur between the insulator substrate and the Ag sintered layer and between the Ag sintered layer and the copper wire in the peeling test. In the column of "Peeling Mode" in Table 1, for the samples where peeling occurred between the insulator substrate and the Ag sintered layer during measurement, "First Mode Peeling" was entered, and for the samples where peeling occurred between the Ag sintered layer and the copper wire, "Second Mode Peeling" was entered. Also, since there was a sample in which first mode peeling occurred when the copper wire was pulled with a force exceeding the measurement upper limit of 25 GPa, for this sample, " > 25.0" was described in the column of "90-degree Tensile Strength" and "First Mode Peeling" was described in the column of "Peeling Mode". Since there was a sample in which neither first mode peeling nor second mode peeling occurred and the copper wire broke during measurement when the copper wire was pulled with a force exceeding the measurement upper limit of 25 GPa, for this sample, "No Peeling" was entered in the column of "Peeling Mode" in Table 1.

Table 1

[0090] From the measurement results of the peeling strength of Samples A1 to A3 in Table 1, when the conductive paste does not contain glass, peeling is likely to occur between the insulator substrate and the Ag sintered layer. By adding a small amount of glass and metal oxide to the conductive paste, it was confirmed that the peeling strength is improved compared to the case where the conductive paste does not contain glass.

[0091] From the measurement results of Samples A1, A3, and A4, it was confirmed that when the glass content ratio in the conductive paste is low, the peeling mode is the first mode, whereas when the glass content ratio in the conductive paste is high, the peeling mode is the second mode.

[0092] From the measurement results of Samples A4 and A5, it was confirmed that by adding a metal oxide to the conductive paste, the peel strength of the joint surface between the Ag sintered layer and the copper wire was improved. Also, from the measurement results of Samples A4 to A9, when the ratio of glass to the metal oxide contained in the conductive paste is low (that is, when the ratio of the metal oxide to the glass contained in the conductive paste is high), the first-mode peeling is likely to occur. Conversely, when the ratio of glass to the metal oxide contained in the conductive paste is high (that is, when the ratio of the metal oxide to the glass contained in the conductive paste is low), it was confirmed that the second-mode peeling is likely to occur. Further, particularly from the measurement results of Samples A6 and A7, when the ratio of glass to the metal oxide contained in the conductive paste is in the range of 2.0 or more and 5.3 or less, it was confirmed that the 90-degree peel strength is high at both the joint surface between the insulator substrate and the Ag sintered layer and the joint surface between the Ag sintered layer and the copper wire.

[0093] From the comparison between the measurement results of Sample A10 and the measurement results of Samples A11 to A14, it was confirmed that by adding a metal oxide to the conductive paste, the peel strength of the joint surface between the Ag sintered layer and the copper wire was improved. Also, from the measurement results of Samples A10 to A14, it was confirmed that when the ratio of glass to the metal oxide contained in the conductive paste is low, the first-mode peeling is likely to occur. Further, particularly from the measurement results of Samples A12 to A14, when the ratio of glass to the metal oxide contained in the conductive paste is in the range of 2.6 or more and 5.0 or less, it was confirmed that the 90-degree peel strength is high at both the joint surface between the insulator substrate and the Ag sintered layer and the joint surface between the Ag sintered layer and the copper wire.

[0094] From the comparison between the measurement results of Sample A16 and those of Samples A17 to A21, it was confirmed that by adding a metal oxide to the conductive paste, the peel strength of the bonding surface between the Ag sintered layer and the copper wire was improved. Similarly, from the measurement results of Samples A16 to A21, it was also confirmed that when the ratio of glass to the metal oxide contained in the conductive paste was low, the first-mode peeling was likely to occur, and conversely, when the ratio of glass to the metal oxide contained in the conductive paste was high, the second-mode peeling was likely to occur. Further, particularly from the measurement results of Samples A6 and A7, when the ratio of glass to the metal oxide contained in the conductive paste was in the range of 3.0 or more and 3.9 or less, it was confirmed that the 90-degree peel strength was high at both the bonding surface between the insulator substrate and the Ag sintered layer and the bonding surface between the Ag sintered layer and the copper wire.

[0095] From the comparison between the measurement results of Sample A22 and those of Samples A23 to A25, it was confirmed that by adding a metal oxide to the conductive paste, the peel strength of the bonding surface between the Ag sintered layer and the copper wire was improved.

[0096] From the measurement results of Samples A3, A8, and A9, when the volume ratio of glass to the metal (Ag) contained in the conductive paste was 7.7 or less, it was found that the bonding strength between the insulator substrate and the Ag sintered layer was lower and the first-mode peeling was relatively likely to occur compared to the case where the volume ratio of glass to the metal (Ag) contained in the conductive paste was 12.1 or more. By setting the volume ratio of glass to the metal (Ag) contained in the conductive paste to 12.1 or more, it was confirmed that the first-mode peeling was unlikely to occur.

[0097] Regarding Samples A23 to A25, it was confirmed that a large amount of glass was aggregated on the bonding surface between the Ag sintered layer and the copper wire. Therefore, there is a possibility that the conductivity between the Ag sintered layer and the copper wire may deteriorate compared to other samples. By setting the volume ratio of glass to the metal (Ag) contained in the conductive paste to 29.8 or less, the amount of glass generated on the bonding surface between the Ag sintered layer and the copper wire can be reduced, and the deterioration of conductivity due to the glass generated on this bonding surface can be suppressed.

[0098] Next, the density of the Ag sintered layer according to the shape of the Ag particles contained in the conductive paste and the amount of glass aggregates generated on the surface of the Ag sintered layer were confirmed as follows. First, insulator substrates were produced in the same manner as Samples A1 to A25, and a conductive paste containing 81.7 vol% Ag particles, 12.1 vol% low melting point lead-free glass (TiO2 - SiO2 - B2O3 - based glass), and 6.1 vol% metal oxide (CuO) was applied to each of the insulator substrates by screen printing to form a conductive paste layer. The Ag particles were small-diameter spherical particles with an aspect ratio of approximately 1 and an average particle diameter of 0.2 μm, large-diameter spherical particles with an aspect ratio of approximately 1 and an average particle diameter of 0.6 μm, first non-spherical particles with an aspect ratio of 10 and an average minimum curvature radius of 0.3, second non-spherical particles with an aspect ratio of 7 and an average minimum curvature radius of 2.0, or mixed particles obtained by mixing these. The small-diameter spherical particles and the large-diameter spherical particles are examples of the first metal particles, and the first non-spherical particles and the second non-spherical particles are examples of the second metal particles. Next, at a temperature of 0.7Tm (Tm is the melting point of Ag), the insulator substrate coated with the conductive paste was heated for 60 minutes to sinter the Ag particles contained in the conductive paste, and the conductive paste layer was used as the Ag sintered layer. This Ag sintered layer is an example of the external electrodes 21 and 22, and the insulator substrate is an example of the base body 10.

[0099] Next, the surface of the Ag sintered layer (the surface opposite to the insulator substrate) is photographed with a scanning electron microscope (SEM) at a magnification of 2000 times. Image processing is performed on the thus obtained photographed image, and based on the difference in brightness, the photographed area is divided into an area where glass aggregates are present and an area other than that (an area where silver particles or metal oxides are exposed). The area where glass aggregates are present and the area other than that can be easily distinguished by the difference in brightness of the photographed image. Next, the area of the region where glass aggregates are present and the ratio of the area of the region where glass aggregates are present to the total area of the region included in the photographed image (hereinafter referred to as the "glass presence ratio") are determined. Further, the Ag sintered layer is cut along its thickness direction to expose the cross section, and a cross-sectional photographed image is obtained by photographing the cross section with a scanning electron microscope (SEM) at a magnification of 2000 times. Image processing is performed on this cross-sectional photographed image, and based on the difference in brightness, the photographed area is divided into a void area and an area other than the void area. The void area and the area other than that can be easily distinguished by the difference in brightness of the photographed image. Next, the area of the void and the ratio of the area of the void to the total area of the region included in the photographed image (hereinafter referred to as the "void presence ratio") are determined.

[0100] The measurement of the area of the region where the above-mentioned glass aggregates exist and the area of the voids was performed on nine different samples (Sample B1 to Sample B9) containing Ag particles in the conductive paste. Sample B1 was prepared using only small-diameter spherical particles as Ag particles, and Sample B2 was prepared using only large-diameter spherical particles as Ag particles. Sample B3 was prepared using only the first non-spherical particles as Ag particles, and Sample B4 was prepared using only the first non-spherical particles as Ag particles. Sample B5 was prepared using mixed particles obtained by mixing small-diameter spherical particles and the first non-spherical particles at a weight ratio of 1:1 as Ag particles. Sample B6 was prepared using mixed particles obtained by mixing large-diameter spherical particles and the first non-spherical particles at a weight ratio of 1:1 as Ag particles. Sample B7 was prepared using mixed particles obtained by mixing small-diameter spherical particles and the second non-spherical particles at a weight ratio of 1:1 as Ag particles. Sample B8 was prepared using mixed particles obtained by mixing large-diameter spherical particles and the first non-spherical particles at a weight ratio of 1:1 as Ag particles. Sample B9 was prepared using mixed particles obtained by mixing the first non-spherical particles and the second non-spherical particles at a weight ratio of 1:1 as Ag particles.

[0101] The evaluation results of the void ratio and the glass ratio for each sample are as shown in Table 2 below. The void ratio was evaluated as "low" when it was less than 15%, "medium" when it was 15% or more and less than 25%, and "high" when it was 25% or more. The glass ratio was evaluated as "low" when it was less than 10%, "medium" when it was 10% or more and less than 25%, and "high" when it was 25% or more.

Table 2

[0102] From the evaluation results of Samples B5 to B7, by producing an Ag sintered layer using a conductive paste containing mixed particles in which small-diameter spherical particles or large-diameter spherical particles and first non-spherical particles or second non-spherical particles are mixed as Ag particles, it was found that there was less glass on the surface of the Ag sintered layer on the side opposite to the insulator substrate, and there were fewer voids inside the Ag sintered layer (that is, the Ag sintered layer had high density). Therefore, Samples B5 to B7 have low electrical resistance on the surface of the Ag sintered layer and also have high mechanical strength.

[0103] By comparing the evaluation results of Samples B1 and B2 with the evaluation results of Samples B3 to B9, it was found that an Ag sintered layer produced from a conductive paste containing first non-spherical particles or second non-spherical particles as Ag particles had less glass generated on the surface of the Ag sintered layer on the side opposite to the insulator substrate and fewer voids inside the Ag sintered layer compared to an Ag sintered layer produced from a conductive paste containing only small-diameter spherical particles or only large-diameter spherical particles as Ag particles. It is considered that there is less glass on the surface of the Ag sintered layer produced from a conductive paste containing first non-spherical particles or second non-spherical particles as Ag particles and fewer voids inside the Ag sintered layer because the movement of the glass in which the first non-spherical particles and the second non-spherical particles are dissolved is suppressed.

[0104] From the above, it was found that by including first non-spherical particles or second non-spherical particles (that is, high aspect ratio particles) in the Ag particles used for producing the external electrode, the generation of glass on the outer peripheral surface (the surface opposite to the substrate) of the external electrode is suppressed, and an external electrode with excellent mechanical strength can be obtained.

Explanation of Reference Numerals

[0105] 1, 101, 201 Coil components 10, 110, 210 Substrates 21, 22, 121, 122, 221, 222 External electrodes 23, 123, 223 Glass layers 25 Conductors 26 Plated layers F Metal parts G glass aggregation region H metal oxide

Claims

1. An insulating substrate, a metal part provided on the substrate, made of a metal material and having conductivity, a glass aggregation region in which a low melting point non-lead glass having a melting point of 500°C or lower and not containing lead has aggregated, and an external electrode containing a non-conductive metal oxide, a glass layer provided in a layer so as to cover the inner peripheral surface of the external electrode between the inner peripheral surface of the external electrode and the surface of the substrate, and composed of the low melting point non-lead glass, and a functional part made of a metal electrically connected to the external electrode. An electronic component comprising:

2. The electronic component according to claim 1, wherein the external electrode has an outer peripheral surface on the side opposite to the inner peripheral surface, and the metal part is configured to be exposed from the outer peripheral surface.

3. The electronic component according to claim 2, wherein the metal part is exposed in a region of 3 / 4 or more of the outer peripheral surface.

4. The electronic component according to any one of claims 1 to 3, wherein the glass aggregation region contacts the metal oxide.

5. The electronic component according to any one of claims 1 to 4, wherein the metal oxide is an oxide of a transition metal.

6. The electronic component according to any one of claims 1 to 5, further comprising a plating layer provided on the outer peripheral surface of the external electrode.

7. The electronic component according to any one of claims 1 to 6, wherein the functional part includes a conductor wound around a coil axis.

8. The electronic component according to any one of claims 1 to 6, wherein the functional part includes a pair of electrodes that generate capacitance.

9. The electronic component according to any one of claims 1 to 8, wherein the volume ratio of the glass to the metal oxide is 2.0 or more and 5.3 or less.

10. The electronic component according to any one of claims 1 to 9, wherein the substrate contains an oxide.

11. A circuit board comprising the electronic component according to any one of claims 1 to 10.

12. An electronic device comprising the circuit board according to claim 11.

13. A step of preparing a substrate made of an insulating material and having a functional part made of a metal, a step of preparing a conductive paste containing conductive metal particles, non-conductive metal oxides, and a low melting point non-lead glass having a melting point of 500°C or lower and not containing lead, a step of applying the conductive paste to the surface of the substrate to form a layer of the conductive paste, By heat-treating the layer of the conductive paste, (1) a metal part formed by sintering the metal particles, a glass aggregation region where the low-melting-point lead-free glass has aggregated, and an external electrode containing the metal oxide, and (2) a glass layer formed in a layered manner so as to cover the inner peripheral surface of the external electrode between the inner peripheral surface of the external electrode and the surface of the substrate and composed of the low-melting-point lead-free glass are formed. A method for manufacturing an electronic component comprising the steps of.

14. The method for manufacturing an electronic component according to claim 13, wherein the volume ratio of the metal oxide contained in the conductive paste is 2% or more.

15. The method for manufacturing an electronic component according to claim 13 or 14, wherein the volume ratio of the glass to the metal oxide contained in the conductive paste is 2.0 or more and 5.3 or less.

16. The method for manufacturing an electronic component according to any one of claims 13 to 15, wherein the average particle diameter of the plurality of metal particles is 1 µm or more and 10 µm or less.

17. The method for manufacturing an electronic component according to any one of claims 13 to 16, wherein the plurality of metal particles include high aspect ratio particles having an aspect ratio of 3 or more.

18. The method for manufacturing an electronic component according to claim 17, wherein the average of the minimum curvature radii of the high aspect ratio particles is 3 µm or less.

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