Patent ID: 12217916

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electronic component of the present invention and the method of producing an electronic component of the present invention are described below. The present invention is not limited to the following preferred embodiments and may be suitably modified without departing from the gist of the present invention. Combinations of preferred features described in the following preferred embodiments are also within the scope of the present invention.

The following embodiments are examples, and features of different embodiments can be partially exchanged or combined with each other. In the second embodiment and subsequent embodiments, a description of features common to the first embodiment is omitted, and only different points are described. In particular, similar effects by similar features are not mentioned in each embodiment. In the following description, the electronic component and the method of producing an electronic component of each embodiment is simply referred to as “the electronic component of the present invention” and “the method of producing an electronic component of the present invention” when no distinction is made between the embodiments.

Embodiment 1

The electronic component of the present invention includes: a base body which includes a first end surface and a second end surface opposite to each other in a length direction, a first main surface and a second main surface opposite to each other in a thickness direction perpendicular to the length direction, and a first side surface and a second side surface opposite to each other in a width direction perpendicular to the length direction and the thickness direction, a first internal electrode exposed at the first end surface, and a second internal electrode exposed at the second surface; a first external electrode on the first end surface and connected to the first internal electrode; and a second external electrode on the second end surface and connected to the second internal electrode, wherein the first external electrode includes a first resin electrode layer containing a conductive component and a resin component, the first resin electrode layer of the first external electrode includes a first portion facing a whole surface of the first end surface of the base body, and a first plurality of protrusions are arranged periodically side by side on a surface of the first portion of the first resin electrode layer of the first external electrode, the surface of the first portion being opposite to the first end surface of the base body.

In the electronic component of the present invention, the base body may be formed of a resin molding including an electrolytic capacitor element, and a sealing resin sealing a periphery of the electrolytic capacitor element, the electrolytic capacitor element may include an anode, a dielectric layer on a surface of the anode, and a cathode facing the anode via the dielectric layer and including an electrolyte layer, and the first internal electrode may be one of the anode or the cathode. Such an electronic component corresponds to an electrolytic capacitor. In the following description, an electrolytic capacitor will be described below as an electronic component of Embodiment 1 of the present invention.

FIG.1is a schematic perspective view showing an electronic component of Embodiment 1 of the present invention.

As shown inFIG.1, the electrolytic capacitor1includes a resin molding9, a first external electrode11, and a second external electrode13.

Herein, a length direction, a thickness direction, and a width direction are directions indicated by L, T, and W respectively, as shown inFIG.1and elsewhere. Here, the length direction L, the thickness direction T, and the width direction W are perpendicular to one another.

The resin molding9corresponds to the base body in the electronic component of the present invention.

The resin molding9has a substantially rectangular parallelepiped shape, and includes a first end surface9aand a second end surface9bopposite to each other in the length direction L, a first main surface9cand a second main surface9dopposite to each other in the thickness direction T, and a first side surface9eand a second side surface9fopposite to each other in the width direction W.

The first end surface9aand the second end face9bof the resin molding9are not required to be strictly perpendicular to the length direction L. Moreover, the first main surface9cand the second main surface9dof the resin molding9are not required to be strictly perpendicular to the thickness direction T. Furthermore, the first side surface9eand the second side surface9fof the resin molding9are not required to be strictly perpendicular to the width direction W.

The first external electrode11is provided on the first end surface9aof the resin molding9. The first external electrode11may extend from the first end surface9aof the resin molding9to a part of each surface in at least one surface selected from the group consisting of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9f.

The second external electrode13is provided on the second end surface9bof the resin molding9. The second external electrode13may extend from the second end surface9bof the resin molding9to a part of each surface in at least one surface selected from the group consisting of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9f.

FIG.2is a schematic cross-sectional view taken along line A1-A2inFIG.1.

As shown inFIG.2, the resin molding9includes a plurality of electrolytic capacitor elements20, and a sealing resin8for sealing the peripheries of the plurality of electrolytic capacitor elements20. More specifically, the resin molding9includes a stack30in which the plurality of electrolytic capacitor elements20are laminated in the thickness direction T, and the sealing resin8for sealing the periphery of the stack30.

In the stack30, for example, the electrolytic capacitor elements20may be bonded to each other via a conductive adhesive called adhesive silver.

It is preferable that the resin molding9includes a plurality of electrolytic capacitor elements20, but it may have one electrolytic capacitor element20.

A support substrate such as a glass epoxy substrate may be provided at a bottom portion of the resin molding9. When a support substrate is provided, the bottom surface of the support substrate constitutes the first main surface9cof the resin molding9.

The electrolytic capacitor element20includes an anode3, a dielectric layer5, and a cathode7.

The anode3corresponds to the first internal electrode in the electronic component of the present invention.

The anode3includes a valve-action metal substrate3aat the center thereof, and a porous portion (not shown) at the surface thereof.

Examples of valve-action metal of the valve-action metal substrate3ainclude elemental metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, and silicon, and alloys containing at least one of these metals. In particular, aluminum and an aluminum alloy are preferred.

The valve-action metal substrate3ais preferably a flat plate, more preferably foil.

Preferably, the porous portion is an etched layer of the valve-action metal substrate3aetched with hydrochloric acid or the like.

The thickness of the valve-action metal substrate3abefore etching is preferably 60 μm to 180 μm. After etching, the thickness of the non-etched core of the valve-action metal substrate3ais preferably 10 μm to 70 μm. The thickness of the porous portion is designed according to the withstand voltage and capacitance required for the electrolytic capacitor1. In the cross section shown inFIG.2, the total thickness of the porous portions on both sides of the valve-action metal substrate3ais preferably 10 μm to 120 μm. The porous portion may be on one of main surfaces of the valve-action metal substrate3a.

The anode3is exposed at the first end surface9aof the resin molding9, and connected to the first external electrode11.

The dielectric layer5is provided on a surface of the anode3. More specifically, the dielectric layer5is provided on a surface of the porous portion.

Preferably, the dielectric layer5is made of an oxide film of the valve-action metal. For example, when the valve-action metal substrate3ais aluminum foil, the valve-action metal substrate3ais anodized in an aqueous solution containing boric acid, phosphoric acid, adipic acid, a sodium salt or an ammonium salt thereof, or the like, whereby an oxide film that turns into the dielectric layer5is formed. The dielectric layer5is formed along the surface of the porous portion, whereby pores (recesses) are formed in the dielectric layer5.

The thickness of the dielectric layer5is designed according to the withstand voltage, capacitance, and the like required for the electrolytic capacitor1. The thickness is preferably 10 nm to 100 nm.

The cathode7corresponds to the second internal electrode in the electronic component of the present invention.

The cathode7is opposite to the anode3via the dielectric layer5.

The cathode7includes an electrolyte layer. More specifically, the cathode7includes a solid electrolyte layer7aon a surface of the dielectric layer5as the electrolyte layer. The electrolytic capacitor1includes the solid electrolyte layer7a, and is thus regarded as a solid electrolytic capacitor.

The electrolytic capacitor1may be an electrolytic capacitor including an electrolytic solution instead of a solid electrolyte, or may be an electrolytic capacitor including a solid electrolyte and an electrolytic solution.

Examples of constituent materials of the solid electrolyte layer7ainclude a conductive polymer having a pyrrole, thiophene, or aniline skeleton. A conductive polymer having a thiophene skeleton is, for example, poly(3,4-ethylenedioxythiophene) (PEDOT), and may be PEDOT:PSS which is a complex with (poly(styrene sulfonate) (PSS)) as a dopant.

The solid electrolyte layer7ais formed by, for example, a method in which a polymerized film of poly(3,4-ethylenedioxythiophene) or the like is formed on the surface of the dielectric layer5using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or a method in which a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) is applied to the surface of the dielectric layer5and then dried. The solid electrolyte layer7ais formed in a predetermined region by applying the treatment liquid or dispersion to the surface of the dielectric layer5by a method such as screen printing, sponge transfer printing, inkjet printing, immersion coating, dispenser coating, or spray coating. Preferably, the solid electrolyte layer7ais obtained by first forming a solid electrolyte layer for an inner layer for filling the pores (recesses) of the dielectric layer5and then forming a solid electrolyte layer for an outer layer for covering the entire dielectric layer5.

The thickness of the solid electrolyte layer7ais preferably 2 μm to 20 μm.

Preferably, the cathode7further includes a conductive layer7bon a surface of the solid electrolyte layer7a.

The conductive layer7bis formed by applying a conductive paste such as a carbon paste, a graphene paste, or a silver paste to a surface of the solid electrolyte layer7aby a method such as screen printing, sponge transfer printing, inkjet printing, immersion coating, dispenser coating, or spray coating.

Preferably, the conductive layer7bis a carbon layer, a graphene layer, or a silver layer formed as described above. The conductive layer7bmay be a composite layer in which a silver layer is disposed on a carbon layer or a graphene layer, or a mixed layer containing a mixture of a carbon paste or a graphene paste with a silver paste.

The thickness of the conductive layer7bis preferably 2 μm to 20 μm.

The cathode7may further include a cathode lead-out layer7con a surface of the conductive layer7b.

The cathode lead-out layer7cis made of metal foil, a resin electrode layer, or the like, for example.

When the cathode lead-out layer7cis metal foil, the metal foil is preferably made of at least one metal selected from the group consisting of aluminum, copper, silver, and an alloy containing at least one of these metals as a main component. When the metal foil is made of the metal described above, the resistance of the metal foil decreases, so that ESR (equivalent series resistance) of the electrolytic capacitor1tends to be low.

As the metal foil may be used, for example, metal foil whose surface is coated with a carbon coat, a titanium coat, or the like by a film forming method such as sputtering or vapor deposition. Carbon-coated aluminum foil is preferably used.

The thickness of the metal foil is preferably 20 μm to 50 μm, from the viewpoints of enhancement in handling performance in the manufacturing process, miniaturization, and reduction of ESR.

When the cathode lead-out layer7cis a resin electrode layer, the resin electrode layer is formed, for example, by applying a conductive paste containing a conductive component and a resin component to the surface of the conductive layer7bby a method such as screen printing, sponge transfer printing, inkjet printing, immersion coating, dispenser coating, or spray coating.

The conductive paste to be used for forming the cathode lead-out layer7cpreferably contains silver, copper, or nickel as a main component of the conductive component.

When the cathode lead-out layer7cis formed by the printing method as described above, it can be formed to be thinner than the metal foil. For example, when the cathode lead-out layer7cis formed by screen printing, the thickness thereof can be set to 20 μm or less.

The cathode lead-out layer7cis preferably formed on the surface of the conductive layer7bin a state where the conductive layer7bis viscous before drying.

The cathode7(here, the cathode lead-out layer7c) is exposed at the second end surface9bof the resin molding9and connected to the second external electrode13. When the cathode7does not include the cathode lead-out layer7c, the conductive layer7bmay be exposed at the second end surface9bof the resin molding9and connected to the second external electrode13.

The sealing resin8contains at least a resin, and preferably contains a resin and filler.

Preferred examples of the resin include an epoxy resin, a phenolic resin, a polyimide resin, a silicone resin, a polyamide resin, and a liquid crystal polymer.

Preferred examples of the filler include silica particles, alumina particles, and metal particles.

Preferably, the sealing resin8includes a material containing a solid epoxy resin, a phenolic resin and silica particles.

In use of the solid sealing resin8, the resin molding9is preferably formed by a method that uses a resin mold such as a compression mold or a transfer mold, with a compression mold being more preferred. In use of the liquid sealing resin8, the resin molding is preferably formed by a method that uses a dispenser or printing. In particular, the periphery of the stack30is preferably sealed by the sealing resin8using a compression mold to produce the resin molding9.

The resin molding9may have rounded corners. The corners of the resin molding9may be rounded by barrel polishing, for example.

The first external electrode11is connected to the anode3exposed at the first end surface9aof the resin molding9.

The first external electrode11includes a resin electrode layer11acontaining a conductive component and a resin component. Since the first external electrode11includes the resin electrode layer11acontaining a resin component, the adhesion between the resin electrode layer11aand the sealing resin8is enhanced in a region where the resin electrode layer11aand the sealing resin8are in contact with each other, thereby improving reliability.

The resin electrode layer11aincludes a first portion11A facing the whole surface of the first end surface9aof the resin molding9, that is, the first end surface9aof the resin molding9is not exposed at the first portion11A of the resin electrode layer11a.

A plurality of protrusions15arranged periodically side by side are provided on a surface of the first portion11A of the resin electrode layer11awhich is located on the opposite side of the first end surface9aof the resin molding9. Here, although a plurality of protrusions are present on the surface of the baked electrode as described in Patent Literature 2, these protrusions are arranged randomly, whereas the plurality of protrusions15are arranged periodically side by side. Since the plurality of protrusions15are provided on the first portion11A of the resin electrode layer11a, a surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9becomes uneven.

The resin electrode layer11amay further include a third portion11B that extends from the first portion11A so as to face a part of each surface in at least one surface selected from the group consisting of the first main surface9c, the second main surface9d, the first side surface9e, or the second side surface9fof the resin molding9. More specifically, in the resin electrode layer11a, the third portion11B may extend from the first portion11A so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9, or may extend from the first portion11A so as to face parts of some surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9.

In the case where the resin electrode layer11aincludes the third portion11B, when a plurality of protrusions15are provided on a surface of the third portion11B of the resin electrode layer11awhich is opposite to the resin molding9, the length in the thickness direction T or the width direction W of the first external electrode11tends to be large. Therefore, when the electrolytic capacitor1is regulated to have a predetermined size, the length in the thickness direction T or the width direction W of the resin molding9tends to be small, so that the length of the effective area of the electrolytic capacitor element20in the thickness direction T or in the width direction W tends to be small, and thus the capacitance tends to be small. From this point of view, it is preferable that the plurality of protrusions15are not provided on the surface of the third portion11B of the resin electrode layer11awhich is opposite to the resin molding9.

In the third portion11B of the resin electrode layer11a, the length in the length direction L of a portion facing the first main surface9cof the resin molding9and the length in the length direction L of a portion facing the second main surface9dof the resin molding9may be the same as or different from each other.

In the third portion11B of the resin electrode layer11a, the length in the length direction L of a portion facing the first side surface9eof the resin molding9and the length in the length direction L of a portion facing the second side surface9fof the resin molding9may be the same as or different from each other.

In the third portion11B of the resin electrode layer11a, the lengths in the length direction L of the portions facing the first main surface9cand the second main surface9dof the resin molding9, and the lengths in the length direction L of the portions facing the first side surface9eand the second side surface9fof the resin molding9may be the same as or different from each other.

Preferably, the conductive component of the resin electrode layer11amainly contains an element metal such as silver, copper, nickel, or tin or an alloy containing at least one of these metals, for example.

Preferably, the resin component of the resin electrode layer11amainly contains an epoxy resin, a phenolic resin, or the like.

The resin electrode layer11apreferably contains the conductive component of 80% by weight to 97% by weight, and the resin component of 3% by weight to 20% by weight. More preferably, the resin electrode layer11acontains the conductive component of 85% by weight to 95% by weight, and the resin component of 5% by weight to 15% by weight. Still more preferably, the resin electrode layer11acontains the conductive component of 90% by weight to 95% by weight, and the resin component of 5% by weight to 10% by weight. The resin electrode layer11aparticularly preferably contains the conductive component of 92% by weight to 95% by weight, and the resin component of 5% by weight to 8% by weight.

The composition ratio between the conductive component and the resin component in the resin electrode layer is determined as follows. First, for the cross section shown inFIG.2, the resin electrode layer is observed with a scanning electron microscope/energy dispersive X-ray analysis (SEM/EDX) to acquire a cross-sectional image. Then, the area ratio between the conductive component and the resin component is calculated, for example, in a square range of 100 μm on a side of the cross-sectional image. The area ratio between the conductive component and the resin component obtained in this way is defined as the composition ratio between the conductive component and the resin component.

The resin electrode layer11ais preferably formed by applying a conductive paste containing a conductive component and a resin component to a position facing the whole surface of the first end surface9aof the resin molding9by screen printing. At this time, so-called mesh traces caused by the mesh shape of a screen printing plate are caused to appear on a surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9. As a result, a plurality of protrusions15arranged periodically side by side can be formed on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9.

The resin electrode layer11amay be formed by applying a conductive paste to a position facing the whole surface of the first end face9aof the resin molding9by sponge transfer printing.

The first external electrode11may further include an outer plating layer11bprovided along the surfaces of the plurality of protrusions15of the first portion11A of the resin electrode layer11a. In this case, the respective gaps between the plurality of protrusions15are not completely filled with the outer plating layer11b, and a surface of the outer plating layer11bwhich is opposite to the first end surface9aof the resin molding9becomes uneven. As a result, a surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9becomes uneven.

InFIGS.1and2, a plurality of protrusions15A are present in the uneven portion of the first external electrode11, and the plurality of protrusions15A include the plurality of protrusions15and the outer plating layer11bprovided on the surface of the plurality of protrusions15. In other words, the plurality of protrusions15A are also periodically arranged side by side in the same manner as the plurality of protrusions15.

The outer plating layer11bmay be provided on the surface of the third portion11B of the resin electrode layer11a.

The outer plating layer11bmay have a single-layer structure or a multilayer structure.

When the outer plating layer11bhas the single-layer structure, the outer plating layer11bpreferably contains copper, nickel, or tin as a main component. As a result, the ESR of the electrolytic capacitor1tends to be low.

When the outer plating layer11bhas the multilayer structure, the outer plating layer11bmay include a first outer plating layer11baand a second outer plating layer11bbin order from the resin electrode layer11aside. In this case, surfaces of the first outer plating layer11baand the second outer plating layer11bbwhich are opposite to the first end surface9aof the resin molding9become uneven.

The first outer plating layer11bais preferably a nickel plating layer containing nickel as a main component.

The nickel plating layer as the first outer plating layer11bais formed, for example, by performing electrolytic nickel plating on the resin electrode layer11a.

The second outer plating layer11bbis preferably a tin plating layer containing tin as a main component.

The tin plating layer as the second outer plating layer11bbis formed, for example, by performing electrolytic tin plating so that the first outer plating layer11badoes not come into contact with air immediately after forming the first outer plating layer11ba.

The first external electrode11may not include the outer plating layer11b. In this case, the first portion11A of the resin electrode layer11ais located on the surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9, and the plurality of protrusions15A are configured by the plurality of protrusions15.

The first external electrode11may further include an inner plating layer11cprovided between the anode3and the first portion11A of the resin electrode layer11a. In this case, the inner plating layer11cis connected to the anode3, and the first portion11A of the resin electrode layer11ais provided so as to cover the inner plating layer11c. The anode3and the first portion11A of the resin electrode layer11amay be connected to each other in a state where the inner plating layer11cis not provided. However, when the contact resistance between the anode3and the first portion11A of the resin electrode layer11ais high, the resistance between the anode3and the first portion11A of the resin electrode layer11ais reduced due to provision of the inner plating layer11c, so that the ESR of the electrolytic capacitor1tends to be low.

The inner plating layer11cmay have a single-layer structure or a multilayer structure.

When the inner plating layer11chas the single-layer structure, the inner plating layer11cpreferably contains copper, nickel, or silver as a main component. As a result, the ESR of the electrolytic capacitor1tends to be low.

When the inner plating layer11chas the multilayer structure, the inner plating layer11cmay include a first inner plating layer11caand a second inner plating layer11cbin order from the anode3side.

The first inner plating layer11cais preferably a nickel plating layer containing nickel as a main component.

The nickel plating layer as the first inner plating layer11cais formed, for example, by performing a zincate treatment on the first end surface9aof the resin molding9, and then performing a displacement plating treatment using electroless nickel plating. The zincate treatment is a treatment for removing oxides on the surface of the metal to be plated and forming a zinc coating on the surface of the metal.

The second inner plating layer11cbis preferably a silver plating layer containing silver as a main component.

The silver plating layer as the second inner plating layer11cb is formed, for example, by performing electrolytic silver plating so that the first inner plating layer11ca does not come into contact with air immediately after forming the first inner plating layer11ca.

The first external electrode11may not include the inner plating layer11c. In this case, the first portion11A of the resin electrode layer11ais connected to the anode3.

The second external electrode13is connected to the cathode7exposed at the second end surface9bof the resin molding9, in this case, the cathode lead-out layer7c.

The second external electrode13preferably includes a resin electrode layer13acontaining a conductive component and a resin component. Since the second external electrode13includes the resin electrode layer13acontaining a resin component, the adhesion between the resin electrode layer13aand the sealing resin8is enhanced in a region where the resin electrode layer13aand the sealing resin8are in contact with each other, thereby improving reliability.

The resin electrode layer13apreferably includes a second portion13A facing the whole surface of the second end surface9bof the resin molding9. In this case, the second end surface9bof the resin molding9is not exposed at the second portion13A of the resin electrode layer13a.

A plurality of protrusions16arranged periodically side by side are preferably provided on a surface of the second portion13A of the resin electrode layer13awhich is located on the opposite side of the second end surface9bof the resin molding9. Since the plurality of protrusions16are provided on the second portion13A of the resin electrode layer13a, a surface of the second external electrode13which is opposite to the second end surface9bof the resin molding9becomes uneven.

The resin electrode layer13amay further include a fourth portion13B extending from the second portion13A so as to face of a part of each surface in at least one surface selected from the group consisting of the first main surface9c, the second main surface9d, the first side surface9e, or the second side surface9fof the resin molding9. More specifically, in the resin electrode layer13a, the fourth portion13B may extend from the second portion13A so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9, or may extend from the second portion13A so as to face parts of some surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9.

In the case where the resin electrode layer13aincludes the fourth portion13B, when a plurality of protrusions16are provided on a surface of the fourth portion13B of the resin electrode layer13awhich is opposite to the resin molding9, the length in the thickness direction T or the width direction W of the second external electrodes13tends to be large. Therefore, when the electrolytic capacitor1is regulated to have a predetermined size, the length in the thickness direction T or the width direction W of the resin molding9tends to be small, so that the length of the effective area of the electrolytic capacitor element20in the thickness direction T or in the width direction W tends to be small, and thus, the capacitance tends to be small. From this point of view, it is preferable that the plurality of protrusions16are not provided on the surface of the fourth portion13B of the resin electrode layer13awhich is opposite to the resin molding9.

In the fourth portion13B of the resin electrode layer13a, the length in the length direction L of a portion facing the first main surface9cof the resin molding9and the length in the length direction L of a portion facing the second main surface9dof the resin molding9may be the same as or different from each other.

In the fourth portion13B of the resin electrode layer13a, the length in the length direction L of a portion facing the first side surface9eof the resin molding9and the length in the length direction L of a portion facing the second side surface9fof the resin molding9may be the same as or different from each other.

In the fourth portion13B of the resin electrode layer13a, the lengths in the length direction L of the portions facing the first main surface9cand the second main surface9dof the resin molding9, and the lengths in the length direction L of the portions facing the first side surface9eand the second side surface9fof the resin molding9may be the same as or different from each other.

Preferably, the conductive component of the resin electrode layer13amainly contains an element metal such as silver, copper, nickel, or tin or an alloy containing at least one of these metals, for example.

Preferably, the resin component of the resin electrode layer13amainly contains an epoxy resin, a phenolic resin, or the like.

The resin electrode layer13apreferably contains the conductive component of 80% by weight to 97% by weight, and the resin component of 3% by weight to 20% by weight. More preferably, the resin electrode layer13acontains the conductive component of 85% by weight to 95% by weight, and the resin component of 5% by weight to 15% by weight. Still more preferably, the resin electrode layer13acontains the conductive component of 90% by weight to 95% by weight, and the resin component of 5% by weight to 10% by weight. The resin electrode layer13aparticularly preferably contains the conductive component of 92% by weight to 95% by weight, and the resin component of 5% by weight to 8% by weight.

The resin electrode layer13ais preferably formed by applying a conductive paste containing a conductive component and a resin component to a position facing the whole surface of the second end surface9bof the resin molding9by screen printing. At this time, mesh traces during screen printing are caused to appear on a surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9. As a result, a plurality of protrusions16arranged periodically side by side can be formed on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9.

The resin electrode layer13amay be formed by applying a conductive paste to a position facing the whole surface of the second end surface9bof the resin molding9by sponge transfer printing.

The second external electrode13may further include an outer plating layer13bprovided along the surfaces of the plurality of protrusions16of the second portion13A of the resin electrode layer13a. In this case, the respective gaps between the plurality of protrusions16are not completely filled with the outer plating layer13b, and a surface of the outer plating layer13bwhich is opposite to the second end surface9bof the resin molding9becomes uneven. As a result, the surface of the second external electrode13which is opposite to the second end surface9bof the resin molding9becomes uneven.

InFIGS.1and2, a plurality of protrusions16A are present in the uneven portion of the second external electrode13, and the plurality of protrusions16A include the plurality of protrusions16and the outer plating layer13bprovided on the surface of the plurality of protrusions16. In other words, the plurality of protrusions16A are also periodically arranged side by side in the same manner as the plurality of protrusions16.

The outer plating layer13bmay be provided on the surface of the fourth portion13B of the resin electrode layer13a.

The outer plating layer13bmay have a single-layer structure or a multilayer structure.

When the outer plating layer13bhas the single-layer structure, the outer plating layer13bpreferably contains copper, nickel, or tin as a main component. As a result, the ESR of the electrolytic capacitor1tends to be low.

When the outer plating layer13bhas the multilayer structure, the outer plating layer13bmay include a first outer plating layer13baand a second outer plating layer13bbin order from the resin electrode layer13aside. In this case, the surfaces of the first outer plating layer13baand the second outer plating layer13bbwhich are opposite to the second end surface9bof the resin molding9become uneven.

The first outer plating layer13bais preferably a nickel plating layer containing nickel as a main component.

The nickel plating layer as the first outer plating layer13bais formed, for example, by performing electrolytic nickel plating on the resin electrode layer13a.

The second outer plating layer13bbis preferably a tin plating layer containing tin as a main component.

The tin plating layer as the second outer plating layer13bbis formed, for example, by performing electrolytic tin plating so that the first outer plating layer13badoes not come into contact with air immediately after forming the first outer plating layer13ba.

The second external electrode13may not include the outer plating layer13b. In this case, the second portion13A of the resin electrode layer13ais located on a surface of the second external electrode13which is opposite to the second end surface9bof the resin molding9, and the plurality of protrusions16A are configured by the plurality of protrusions16.

The second external electrode13may further include an inner plating layer13cprovided between the cathode7and the second portion13A of the resin electrode layer13a. In this case, the inner plating layer13cis connected to the cathode7, and the second portion13A of the resin electrode layer13ais provided so as to cover the inner plating layer13c. The cathode7and the second portion13A of the resin electrode layer13amay be connected to each other in a state where the inner plating layer13cis not provided. However, when the contact resistance between the cathode7and the second portion13A of the resin electrode layer13ais high, the resistance between the cathode7and the second portion13A of the resin electrode layer13ais reduced due to provision of the inner plating layer13c, so that the ESR of the electrolytic capacitor1tends to be low.

The inner plating layer13cmay have a single-layer structure or a multilayer structure.

When the inner plating layer13chas the single-layer structure, the inner plating layer13cpreferably contains copper, nickel, or silver as a main component. As a result, the ESR of the electrolytic capacitor1tends to be low.

When the inner plated layer13chas the multilayer structure, the inner plating layer13cmay include a first inner plating layer13caand a second inner plating layer13cbin order from the cathode7side.

The first inner plating layer13cais preferably a nickel plating layer containing nickel as a main component.

The nickel plating layer as the first inner plating layer13cais formed, for example, on the second end surface9bof the resin molding9by the same method as the nickel plating layer as the first inner plating layer11ca. The zincate treatment may not be performed. However, when the cathode7, in this case, the cathode lead-out layer7c, contains aluminum as a main component, it is preferable to perform the zincate treatment.

The second inner plating layer13cbis preferably a silver plating layer containing silver as a main component.

The silver plating layer as the second inner plating layer13cbis formed, for example, by performing electrolytic silver plating so that the first inner plating layer13cadoes not come into contact with air immediately after forming the first inner plating layer13ca.

The second external electrode13may not include the inner plating layer13c. In this case, the second portion13A of the resin electrode layer13ais connected to the cathode7.

FIG.3is a schematic cross-sectional view showing a state in which an electrolytic capacitor shown inFIG.2is mounted on a wiring board via a conductive bonding material.

As shown inFIG.3, the electrolytic capacitor1is mounted on a wiring board50via a conductive bonding material54such as solder. The wiring board50includes a printed board51, a land electrode52provided on a surface of the printed board51, and a land electrode53provided on the surface of the printed board51at a position different from that of the land electrode52. In a state where the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the first external electrode11and the land electrode52are electrically connected to each other via a conductive bonding material54, and the second external electrode13and the land electrode53are electrically connected to each other via another conductive bonding material54.

InFIG.3, a plurality of protrusions15are provided on a surface of the first portion11A of the resin electrode layer11aof the first external electrode11which is opposite to the first end surface9aof the resin molding9, so that the surface of the first external electrode11, in this case, the outer plating layer11bwhich is opposite to the first end surface9aof the resin molding9becomes uneven. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the first external electrode11and the conductive bonding material54is increased, and also an anchor effect is exhibited. Therefore, the adhesion between the first external electrode11and the conductive bonding material54is enhanced. Further, when measuring the electrical characteristics of the electrolytic capacitor1, a measurement probe can be brought into contact with the plurality of protrusions15A present in an uneven portion of the first external electrode11, so that the measurement is stabilized.

InFIG.3, a plurality of protrusions16are provided on a surface of the second portion13A of the resin electrode layer13aof the second external electrode13which is opposite to the second end surface9bof the resin molding9, so that the surface of the second external electrode13, in this case, the outer plating layer13bwhich is opposite to the second end surface9bof the resin molding9becomes uneven. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the second external electrode13and the conductive bonding material54is increased, and the anchor effect is exhibited. Therefore, the adhesion between the second external electrode13and the conductive bonding material54is enhanced. Further, when measuring the electrical characteristics of the electrolytic capacitor1, a measurement probe can be brought into contact with the plurality of protrusions16A present in an uneven portion of the second external electrode13, so that the measurement is stabilized.

The form of the first external electrode11, particularly the form of the resin electrode layer11awill be described below.

On the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9, the plurality of protrusions15are preferably arranged periodically side by side in at least one direction, and more preferably arranged periodically side by side in a plurality of intersecting directions. Examples of a mode in which the plurality of protrusions15are periodically arranged side by side in a plurality of intersecting directions include, for example, a mode in which the plurality of protrusions15are arranged in a matrix form. In this case, the plurality of protrusions15may be arranged along the thickness direction T and the width direction W in a matrix form.

Likewise, on the surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9, the plurality of protrusions15A are preferably arranged periodically side by side in at least one direction, and more preferably arranged periodically side by side in a plurality of intersecting directions. Examples of a mode in which the plurality of protrusions15A are periodically arranged side by side in the plurality of intersecting directions include, for example, a mode in which the plurality of protrusions15A are arranged in a matrix form. In this case, the plurality of protrusions15A may be arranged along the thickness direction T and the width direction W in a matrix form.

It is preferable that the plurality of protrusions15are provided in a region on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9, the area of the region being 80% or more of the area of the surface. More preferably, the plurality of protrusions15are provided on the whole surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9.

Likewise, it is preferable that the plurality of protrusions15A are provided in a region on the surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9, the area of the region being 80% or more of the area of the surface. More preferably, the plurality of protrusions15A are provided on the whole surface of the first external electrode11which is opposite to the first end surface9aof the resin molding9.

When viewing a cross section along the thickness direction T and the width direction W, the cross-sectional shape of each of the plurality of protrusions15may be polygonal or circular.

Likewise, when viewing the cross section along the thickness direction T and the width direction W, the cross-sectional shape of each of the plurality of protrusions15A may be polygonal or circular.

FIG.4is a schematic cross-sectional view showing an enlarged region near the first external electrode in the electrolytic capacitor shown inFIG.2.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, it is preferable that the cross-sectional shape of each of the plurality of protrusions15is a so-called tapered shape in which the length thereof in the thickness direction T decreases from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a. In this case, the ridgeline of each of the plurality of protrusions15may be a curved line or a straight line.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, the cross-sectional shape of each of the plurality of protrusions15may be a shape in which the length thereof in the thickness direction T is constant from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a.

Likewise, when viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, it is preferable that the cross-sectional shape of each of the plurality of protrusions15A is a tapered shape in which the length thereof in the thickness direction T decreases from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a. In this case, the ridgeline of each of the plurality of protrusions15A may be a curved line or a straight line.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, the cross-sectional shape of each of the plurality of protrusions15A may be a shape in which the length thereof in the thickness direction T is constant from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, it is preferable that the surface of the first portion11A of the resin electrode layer11ahas an arithmetic mean roughness Ra defined in JIS B 0601:2013 of 20 μm to 100 μm. In this case, in the first portion11A of the resin electrode layer11a, the lengths in the length direction L of the plurality of protrusions15are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the first external electrode11and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the first external electrode11and the conductive bonding material54is sufficiently enhanced. Further, when forming the outer plating layer11b, it can be easily formed along the surfaces of the plurality of protrusions15.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.4, it is preferable that bottom surfaces11Aa located in respective gaps between the plurality of protrusions15and top surfaces11Ab of the plurality of protrusions15are present on the surface of the first portion11A of the resin electrode layer11a. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the first external electrode11and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the first external electrode11and the conductive bonding material54is sufficiently enhanced.

With respect to the surface of the first portion11A of the resin electrode layer11a, when viewing the cross section shown inFIG.4, the bottom surface11Aa includes surfaces located between the plurality of protrusions15, and indicates a range which includes a point closest to the first end surface9aside of the resin molding9in the length direction L and has an arithmetic mean roughness Ra of 5 μm or less as defined in JIS B 0601:2013 in each surface.

With respect to the surface of the first portion11A of the resin electrode layer11a, when viewing the cross section shown inFIG.4, the top surface11Ab indicates a range which includes a point located on the most opposite side to the first end surface9aof the resin molding9in the length direction L and has an arithmetic mean roughness Ra of 5 μm or less defined in JIS B 0601:2013 in each of the plurality of protrusions15.

The length Taa in the thickness direction T of the bottom surface11Aa is preferably 50 μm to 200 μm. In this case, in the first portion11A of the resin electrode layer11a, the intervals in the thickness direction T between the plurality of protrusions15are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions15A present in the uneven portions of the first external electrodes11. Further, when forming the outer plating layer11b, the outer plating layer11bis easily formed along the surfaces of the plurality of protrusions15.

When the bottom surfaces11Aa are present at 20 or more locations, the length Taa in the thickness direction T of the bottom surface11Aa is defined by an average value of the lengths in the thickness direction T of the bottom surfaces11Aa at 20 locations out of the 20 or more locations, and when the bottom surfaces11Aa are not present at 20 or more locations, the length Taa in the thickness direction T of the bottom surface11Aa is defined by an average value of the lengths in the thickness direction T of all the present bottom surfaces11Aa.

The shortest distance Tpa in the thickness direction T between the top surfaces11Ab of two adjacent protrusions15out of the plurality of protrusions15is preferably 50 μm to 100 μm. In this case, in the first portion11A of the resin electrode layer11a, the intervals in the thickness direction T between the plurality of protrusions15are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions15A present in the uneven portion of the first external electrode11. Further, when forming the outer plating layer11b, the outer plating layer11bis easily formed along the surfaces of the plurality of protrusions15.

When the region between the top surfaces11Ab are present at 20 or more locations, the shortest distance Tpa in the thickness direction T between the top surfaces11Ab is defined by an average value of the shortest distances in the thickness direction T for the regions at 20 locations out of the 20 or more locations, and when the regions between the top surfaces11Ab are not present at 20 or more locations, the shortest distance Tpa in the thickness direction T between the top surfaces11Ab is defined by an average value of the shortest distances in the thickness direction T for all the regions.

The shortest distance Tpa in the thickness direction T between the top surfaces11Ab is preferably larger than the length Taa in the thickness direction T of the bottom surface11Aa. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions15A present in the uneven portion of the first external electrode11. Further, when forming the outer plating layer11b, the outer plating layer11bis easily formed along the surfaces of the plurality of protrusions15.

The shortest distance Tpa in the thickness direction T between the top surfaces11Ab may be the same as the length Taa in the thickness direction T of the bottom surface11Aa, or may be smaller than the length Taa in the thickness direction T of the bottom surface11Aa.

The length Tba in the thickness direction T of the top surface11Ab is preferably 10 μm to 100 μm. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the first external electrode11and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the first external electrode11and the conductive bonding material54is sufficiently enhanced. Further, when forming the outer plating layer11b, the outer plating layer11bis easily formed along the surfaces of the plurality of protrusions15.

When the top surfaces11Ab are present at 20 or more locations, the length Tba in the thickness direction T of the top surface11Ab is defined by an average value of the lengths in the thickness direction T of the top surfaces11Ab at 20 locations out of the 20 or more locations, and when the top surfaces11Ab are not present at 20 or more locations, the length Tba in the thickness direction T of the top surface11Ab is defined by an average value of the lengths in the thickness direction T of all the top surfaces11Ab.

The length Taa in the thickness direction T of the bottom surface11Aa is preferably larger than the length Tba in the thickness direction T of the top surface11Ab. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions15A present in the uneven portion of the first external electrode11. Further, when forming the outer plating layer11b, the outer plating layer11bis easily formed along the surfaces of the plurality of protrusions15.

The length Taa in the thickness direction T of the bottom surface11Aa may be the same as the length Tba in the thickness direction T of the top surface11Ab, or may be smaller than the length Tba in the thickness direction T of the top surface11Ab.

The shortest distance La in the length direction L between the bottom surface11Aa and the first end surface9ais preferably 10 μm to 50 μm.

InFIG.4, each of the plurality of protrusions15is provided at a position facing the anode3in the length direction L, but it may not be provided at a position facing the anode3in the length direction L. For example, each of the plurality of protrusions15may be provided at a position facing the region between the anodes3in the length direction L.

InFIG.4, each of the plurality of protrusions15is provided at a position facing the inner plating layer11cin the length direction L, but it may not be provided at a position facing the inner plating layer11cin the length direction L. For example, each of the plurality of protrusions15may be provided at a position facing the region between the inner plating layers11cin the length direction L.

Although not shown, when viewing the cross section along the length direction L and the width direction W, it is preferable that the cross-sectional shape of each of the plurality of protrusions15is a tapered shape in which the length thereof in the width direction W decreases from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a. In this case, the ridgeline of each of the plurality of protrusions15may be a curved line or a straight line.

When viewing the cross section along the length direction L and the width direction W, the cross-sectional shape of each of the plurality of protrusions15may be a shape in which the length thereof in the width direction W is constant from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a.

Likewise, when viewing the cross section along the length direction L and the width direction W, it is preferable that the cross-sectional shape of each of the plurality of protrusions15A is a tapered shape in which the length thereof in the width direction W decreases from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a. In this case, the ridgeline of each of the plurality of protrusions15A may be a curved line or a straight line.

When viewing the cross section along the length direction L and the width direction W, the cross-sectional shape of each of the plurality of protrusions15A may be a shape in which the length thereof in the width direction W is constant from the first end surface9aside of the resin molding9to the opposite side to the first end surface9a.

When viewing the cross section along the length direction L and the width direction W, it is preferable that the surface of the first portion11A of the resin electrode layer11ahas an arithmetic mean roughness Ra defined in JIS B 0601:2013 of 20 μm to 100 μm.

The arithmetic mean roughness Ra of the surface of the first portion11A of the resin electrode layer11amay be the same or different between when viewing the cross section along the length direction L and the thickness direction T and when viewing the cross section along the length direction L and the width direction W.

When viewing the cross section along the length direction L and the width direction W, similarly to when viewing the cross section along the length direction L and the thickness direction T, it is preferable that the bottom surfaces located in respective gaps between the plurality of protrusions15and the top surfaces of the plurality of protrusions15are present on the surface of the first portion11A of the resin electrode layer11a.

The length in the width direction W of the bottom surface is preferably 50 μm to 200 μm.

The length in the width direction W of the bottom surface may be the same as or different from the length Taa in the thickness direction T of the bottom surface11Aa.

The shortest distance in the width direction W between the top surfaces of two adjacent protrusions15out of the plurality of protrusions15is preferably 50 μm to 100 μm.

The shortest distance in the width direction W between the top surfaces is preferably larger than the length in the width direction W of the bottom surface.

The shortest distance in the width direction W between the top surfaces may be the same as the length in the width direction W of the bottom surface, or may be smaller than the length in the width direction W of the bottom surface.

The shortest distance in the width direction W between the top surfaces may be the same as or different from the shortest distance Tpa in the thickness direction T between the top surfaces11Ab.

The length in the width direction W of the top surface is preferably 10 μm to 100 μm.

The length in the width direction W of the top surface may be the same as or different from the length Tba in the thickness direction T of the top surface11Ab.

The length in the width direction W of the bottom surface is preferably larger than the length in the width direction W of the top surface.

The length in the width direction W of the bottom surface may be the same as the length in the width direction W of the top surface, or may be smaller than the length in the width direction W of the top surface.

In the first external electrode11, a cross section along the length direction L and the thickness direction T, a cross section along the length direction L and the width direction W, and a cross section along the thickness direction T and the width direction W are observed with a scanning electron microscope (SEM). Various parameters of the resin electrode layer11asuch as the above-described arithmetic mean roughness Ra of the surface of the first portion11A of the resin electrode layer11aare measured from cross-sectional images captured by the scanning electron microscope.

The form of the second external electrode13, particularly the form of the resin electrode layer13awill be described below.

On the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9, the plurality of protrusions16are preferably arranged periodically side by side in at least one direction, and more preferably arranged periodically side by side in a plurality of intersecting directions. Examples of a mode in which the plurality of protrusions16are periodically arranged side by side in a plurality of intersecting directions include, for example, a mode in which the plurality of protrusions16are arranged in a matrix form. In this case, the plurality of protrusions16may be arranged in the thickness direction T and the width direction W in a matrix form.

Likewise, on the surface of the second external electrode13which is opposite to the second end face9bof the resin molding9, the plurality of protrusions16A are preferably arranged periodically side by side in at least one direction, and more preferably arranged periodically side by side in a plurality of intersecting directions. Examples of a mode in which the plurality of protrusions16A are periodically arranged side by side in the plurality of intersecting directions include, for example, a mode in which the plurality of protrusions16A are arranged in a matrix form. In this case, the plurality of protrusions16A may be arranged along the thickness direction T and the width direction W in a matrix form.

It is preferable that the plurality of protrusions16are provided in a region on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9, the area of the region being 80% or more of the area of the surface. More preferably, the plurality of protrusions16are provided on the whole surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9.

Likewise, it is preferable that the plurality of protrusions16A are provided in a region on the surface of the second external electrode13which is opposite to the second end surface9bof the resin molding9, the area of the region being 80% or more of the area of the surface. More preferably, the plurality of protrusions16A are provided on the whole surface of the second external electrode13which is opposite to the second end surface9bof the resin molding9.

When viewing a cross section along the thickness direction T and the width direction W, the cross-sectional shape of each of the plurality of protrusions16may be polygonal or circular.

Likewise, when viewing a cross section along the thickness direction T and the width direction W, the cross-sectional shape of each of the plurality of protrusions16A may be polygonal or circular.

FIG.5is a schematic cross-sectional view showing an enlarged region near the second external electrode in the electrolytic capacitor shown inFIG.2.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.5, it is preferable that the cross-sectional shape of each of the plurality of protrusions16is a so-called tapered shape in which the length thereof in the thickness direction T decreases from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b. In this case, the ridgeline of each of the plurality of protrusions16may be a curved line or a straight line.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.5, the cross-sectional shape of each of the plurality of protrusions16may be a shape in which the length thereof in the thickness direction T is constant from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b.

Likewise, when viewing the cross section along the length direction L and the thickness direction T shown inFIG.5, it is preferable that the cross-sectional shape of each of the plurality of protrusions16A is a tapered shape in which the length thereof in the thickness direction T decreases from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b. In this case, the ridgeline of each of the plurality of protrusions16A may be a curved line or a straight line.

When viewing the cross section along the length direction L and thickness direction T shown inFIG.5, the cross-sectional shape of each of the plurality of protrusions16A may be a shape in which the length thereof in the thickness direction T is constant from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.5, it is preferable that the surface of the second portion13A of the resin electrode layer13ahas an arithmetic mean roughness Ra defined in JIS B 0601:2013 of 20 μm to 100 μm. In this case, in the second portion13A of the resin electrode layer13a, the length in the length direction L of the plurality of protrusions16are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the second external electrode13and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the second external electrode13and the conductive bonding material54is sufficiently enhanced. Further, when forming the outer plating layer13b, it can be easily formed along the surfaces of the plurality of protrusions16.

When viewing the cross section along the length direction L and the thickness direction T shown inFIG.5, it is preferable that bottom surfaces13Aa located in respective gaps between the plurality of protrusions16and top surfaces13Ab of the plurality of protrusions16are present on the surface of the second portion13A of the resin electrode layer13a. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the second external electrode13and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the second external electrode13and the conductive bonding material54is sufficiently enhanced.

With respect to the surface of the second portion13A of the resin electrode layer13a, when viewing the cross section shown inFIG.5, the bottom surface13Aa includes surfaces located between the plurality of protrusions16and indicates a range which includes a point closest to the second end surface9bside of the resin molding9in the length direction L and has an arithmetic mean roughness Ra of 5 μm or less as defined in JIS B 0601:2013 in each surface.

With respect to the surface of the second portion13A of the resin electrode layer13a, when viewing the cross section shown inFIG.5, the top surface13Ab indicates a range which includes a point located on the most opposite side to the second end surface9bof the resin molding9in the length direction L and has an arithmetic mean roughness Ra of 5 μm or less defined in JIS B 0601:2013 in each of the plurality of protrusions16.

The length Tab in the thickness direction T of the bottom surface13Aa is preferably 50 μm to 200 μm. In this case, in the second portion13A of the resin electrode layer13a, the intervals in the thickness direction T between the plurality of protrusions16are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions16A present in the uneven portion of the second external electrode13. Further, when forming the outer plating layer13b, the outer plating layer13bis easily formed along the surfaces of the plurality of protrusions16.

When the bottom surfaces13Aa are present at 20 or more locations, the length Tab in the thickness direction T of the bottom surface13Aa is defined by an average value of the lengths in the thickness direction T of the bottom surfaces13Aa at 20 locations out of the 20 or more locations, and when the bottom surfaces13Aa are not present at 20 or more locations, the length Tab in the thickness direction T of the bottom surface13Aa is defined by an average value of the lengths in the thickness direction T of all the bottom surfaces13Aa.

The shortest distance Tpb in the thickness direction T between the top surfaces13Ab of two adjacent protrusions16out of the plurality of protrusions16is preferably 50 μm to 100 μm. In this case, in the second portion13A of the resin electrode layer13a, the intervals in the thickness direction T between the plurality of protrusions16are relatively large. Therefore, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions16A present in the uneven portion of the second external electrodes13. Further, when forming the outer plating layer13b, the outer plating layer13bis easily formed along the surfaces of the plurality of protrusions16.

When the regions between the top surfaces13Ab are present at 20 or more locations, the shortest distance Tpb in the thickness direction T between the top surfaces13Ab is defined by an average value of the shortest distances in the thickness direction T for the regions located at 20 locations out of the 20 or more locations, and when the regions between the top surfaces13Ab are not present at 20 or more locations, the shortest distance Tpb in the thickness direction T between the top surfaces13Ab is defined by an average value of the shortest distances in the thickness direction T for all the regions.

The shortest distance Tpb in the thickness direction T between the top surfaces13Ab is preferably larger than the length Tab in the thickness direction T of the bottom surface13Aa. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions16A present in the uneven portion of the second external electrode13. Further, when forming the outer plating layer13b, the outer plating layer13bis easily formed along the surfaces of the plurality of protrusions16.

The shortest distance Tpb in the thickness direction T between the top surfaces13Ab may be the same as the length Tab in the thickness direction T of the bottom surface13Aa, or may be smaller than the length Tab in the thickness direction T of the bottom surface13Aa.

The length Tbb in the thickness direction T of the top surface13Ab is preferably 10 μm to 100 μm. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the contact area between the second external electrode13and the conductive bonding material54is sufficiently increased, and the anchor effect is sufficiently exhibited, so that the adhesion between the second external electrode13and the conductive bonding material54is sufficiently enhanced. Further, when forming the outer plating layer13b, the outer plating layer13bis easily formed along the surfaces of the plurality of protrusions16.

When the top surfaces13Ab are present at 20 or more locations, the length Tbb in the thickness direction T of the top surface13Ab is defined by an average value of the lengths in the thickness direction T of the top surfaces13Ab at 20 locations out of the 20 or more locations, and when the top surfaces13Ab are not present at 20 or more locations, the length Tbb in the thickness direction T of the top surface13Ab is defined by an average value of the lengths in the thickness direction T of all the top surfaces13Ab.

The length Tab in the thickness direction T of the bottom surface13Aa is preferably larger than the length Tbb in the thickness direction T of the top surface13Ab. In this case, when the electrolytic capacitor1is mounted on the wiring board50via the conductive bonding material54, the conductive bonding material54easily infiltrates into the gaps between the plurality of protrusions16A present in the uneven portion of the second external electrode13. Further, when forming the outer plating layer13b, the outer plating layer13bis easily formed along the surfaces of the plurality of protrusions16.

The length Tab in the thickness direction T of the bottom surface13Aa may be the same as the length Tbb in the thickness direction T of the top surface13Ab, or may be smaller than the length Tbb in the thickness direction T of the top surface13Ab.

The shortest distance Lb in the length direction L between the bottom surface13Aa and the second end surface9bis preferably 10 μm to 50 μm.

InFIG.5, each of the plurality of protrusions16is provided at a position facing the cathode7, in this case, the cathode lead-out layer7cin the length direction L, but it may not be provided at a position facing the cathode7in the length direction L. For example, each of the plurality of protrusions16may be provided at a position facing a region between the cathodes7in the length direction L.

InFIG.5, each of the plurality of protrusions16is provided at a position facing the inner plating layer13cin the length direction L, but it may not be provided at a position facing the inner plating layer13cin the length direction L. For example, each of the plurality of protrusions16may be provided at a position facing the region between the inner plating layers13cin the length direction L.

Although not shown, when viewing the cross section along the length direction L and the width direction W, it is preferable that the cross-sectional shape of each of the plurality of protrusions16is a tapered shape in which the length thereof in the width direction W decreases from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b. In this case, the ridgeline of each of the plurality of protrusions16may be a curved line or a straight line.

When viewing the cross section along the length direction L and the width direction W, the cross-sectional shape of each of the plurality of protrusions16may be a shape in which the length thereof in the width direction W is constant from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b.

Likewise, when viewing the cross section along the length direction L and the width direction W, it is preferable that the cross-sectional shape of each of the plurality of protrusions16A is a tapered shape in which the length thereof in the width direction W decreases from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b. In this case, the ridgeline of each of the plurality of protrusions16A may be a curved line or a straight line.

When viewing the cross section along the length direction L and the width direction W, the cross-sectional shape of each of the plurality of protrusions16A may be a shape in which the length thereof in the width direction W is constant from the second end surface9bside of the resin molding9to the opposite side to the second end surface9b.

When viewing the cross section along the length direction L and the width direction W, it is preferable that the surface of the second portion13A of the resin electrode layer13ahas an arithmetic mean roughness Ra defined in JIS B 0601:2013 of 20 μm to 100 μm.

The arithmetic mean roughness Ra of the surface of the second portion13A of the resin electrode layer13amay be the same or different between when viewing the cross section along the length direction L and the thickness direction T and when viewing a cross section along the length direction L and the width direction W.

When viewing the cross section along the length direction L and the width direction W, similarly to when viewing the cross section along the length direction L and the thickness direction T, it is preferable that the bottom surfaces located in respective gaps between the plurality of protrusions16and the top surfaces of the plurality of protrusions16are present on the surface of the second portion13A of the resin electrode layer13a.

The length in the width direction W of the bottom surface is preferably 50 μm to 200 μm.

The length in the width direction W of the bottom surface may be the same as or different from the length Tab in the thickness direction T of the bottom surface13Aa.

The shortest distance in the width direction W between the top surfaces of two adjacent protrusions16out of the plurality of protrusions16is preferably 50 μm to 100 μm.

The shortest distance in the width direction W between the top surfaces is preferably larger than the length in the width direction W of the bottom surface.

The shortest distance in the width direction W between the top surfaces may be the same as the length in the width direction W of the bottom surface, or may be smaller than the length in the width direction W of the bottom surface.

The shortest distance in the width direction W between the top surfaces may be the same as or different from the shortest distance Tpb in the thickness direction T between the top surfaces13Ab.

The length in the width direction W of the top surface is preferably 10 μm to 100 μm.

The length in the width direction W of the top surface may be the same as or different from the length Tbb in the thickness direction T of the top surface13Ab.

The length in the width direction W of the bottom surface is preferably larger than the length in the width direction W of the top surface.

The length in the width direction W of the bottom surface may be the same as the length in the width direction W of the top surface, or may be smaller than the length in the width direction W of the top surface.

In the second external electrode13, a cross section along the length direction L and the thickness direction T, a cross section along the length direction L and the width direction W, and a cross section along the thickness direction T and the width direction W are observed with a scanning electron microscope. Various parameters of the resin electrode layer13asuch as the above-described arithmetic mean roughness Ra of the surface of the second portion13A of the resin electrode layer13aare measured from cross-sectional images captured by the scanning electron microscope.

The method of producing an electronic component of the present invention includes: forming a base body which includes a first end surface and a second end surface opposite to each other in a length direction, a first main surface and a second main surface opposite to each other in a thickness direction perpendicular to the length direction, and a first side surface and a second side surface opposite to each other in a width direction perpendicular to the length direction and the thickness direction, a first internal electrode exposed at the first end surface, and a second internal electrode exposed at the second end surface; forming, on the first end surface of the base body, a first external electrode so as to be connected to the first internal electrode by applying a conductive paste containing a conductive component and a resin component by screen printing to form a first resin electrode layer including a first portion facing a whole surface of the first end surface of the base body so that a first plurality of protrusions are arranged periodically side by side on a surface of the first portion, the surface of the first portion being opposite to the first end surface of the base body; and forming, on the second end surface of the base body, a second external electrode so as to be connected to the second internal electrode. As an example of the method of producing an electronic component of the present invention, a method of producing the electronic component of Embodiment 1 of the present invention, that is, a method of producing the electrolytic capacitor1shown inFIGS.1,2and the like, is described.

Forming Resin Molding

Forming the resin molding9corresponds to forming a base body in the method of producing an electronic component of the present invention.

First, a valve-action metal substrate3aincluding a porous portion at a surface thereof, that is, an anode3is prepared. Then, the surface of the porous portion is subjected to an anodization treatment to form a dielectric layer5on the surface of the porous portion.

Next, a solid electrolyte layer7ais formed on a surface of the dielectric layer5by screen printing or the like. Then, a conductive layer7bis formed on a surface of the solid electrolyte layer7aby screen printing or the like. Furthermore, a cathode lead-out layer7cis formed on a surface of the conductive layer7bby a method of laminating a metal foil, screen printing, or the like. As a result, a cathode7including the solid electrolyte layer7a, the conductive layer7b, and the cathode lead-out layer7cis formed.

As a result, an electrolytic capacitor element20including the anode3, the dielectric layer5provided on the surface of the anode3, and the cathode7which faces the anode3via the dielectric layer5and includes the solid electrolyte layer7ais produced.

Next, a plurality of electrolytic capacitor elements20are laminated to produce a stack30. Then, the periphery of the stack30is sealed with a sealing resin8by compression molding or the like to form a resin molding9.

The resin molding9has a substantially rectangular parallelepiped shape, and includes a first end surface9aand a second end surface9bopposite to each other in the length direction L, a first main surface9cand a second main surface9dopposite to each other in the thickness direction T, and a first side surface9eand a second side surface9fopposite to each other in the width direction W.

In the resin molding9, the anode3is exposed at the first end surface9a, and the cathode7, in this case, the cathode lead-out layer7cis exposed at the second end surface9b.

Forming First External Electrode

First, the first end face9aof the resin molding9is subjected to a plating treatment to form an inner plating layer11cconnected to the anode3. More specifically, as the inner plating layer11c, a first inner plating layer11caand a second inner plating layer11cbare formed in order from the anode3side.

When forming the first inner plating layer11ca, it is preferable that the first end surface9aof the resin molding9is subjected to a zincate treatment, and then subjected to a displacement plating treatment using electroless nickel plating to form a nickel plating layer.

For example, when the valve-action metal substrate3ais an aluminum foil, the surface of the valve-action metal substrate3aexposed at the first end face9aof the resin molding9is first etched with an acid containing nitric acid as a main component, and then a zinc coating is formed on the surface, thereby performing the zincate treatment. It is preferable to perform both single zincate (pickling) and double zincate (exfoliation) as the zincate treatment. Further, a nickel plating layer is formed as the first inner plating layer11caby performing the displacement plating treatment using electroless nickel plating.

When forming the second inner plating layer11cb, it is preferable that immediately after the formation of the first inner plating layer11ca, electrolytic silver plating is performed so that the first inner plating layer11cadoes not come into contact with air, thereby forming a silver plating layer.

Next, a conductive paste containing a conductive component and a resin component is applied to the first end surface9aof the resin molding9by screen printing to form a resin electrode layer11aso as to include a first portion11A facing the whole surface of the first end surface9aof the resin molding9, whereby the first portion11A of the resin electrode layer11ais formed so as to cover the inner plating layer11c. When forming the resin electrode layer11a, mesh traces during screen printing are caused to appear on a surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9. As a result, a plurality of protrusions15arranged periodically side by side can be formed on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9.

For example, the following method may be adopted as a method for causing the mesh traces during screen printing to appear on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9.

When forming the resin electrode layer11a, the applied conductive paste is thermally cured. If a drying time (including a resting time) before the thermal curing is shortened or a drying temperature is increased, the mesh traces are likely to appear on a surface of the first portion11A of the electrode layer11awhich is opposite to the first end surface9aof the resin molding9.

When forming the resin electrode layer11a, if a conductive paste having high thixotropy is applied by screen printing, the applied conductive paste is difficult to be leveled, so that the mesh traces are likely to appear on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9. From this point of view, the conductive paste for forming the resin electrode layer11apreferably has a thixotropic index of 1.5 to 10.0, more preferably 1.5 to 7.0, and still more preferably 2.0 to 7.0, particularly preferably 3.0 to 7.0.

The thixotropic index of the conductive paste is determined as follows. First, the viscosity V1 of the conductive paste when a spindle of No. 14 is rotated at 10 rpm at 25° C. is measured with an HB viscometer produced by Brookfield company. Next, the viscosity V2 of the conductive paste when the spindle of No. 14 is rotated at 100 rpm at 25° C. is measured with the same viscometer. The ratio V1/V2 between the viscosity V1 and the viscosity V2 is calculated, and a thus-obtained calculation value is defined as the thixotropic index of the conductive paste.

When forming the resin electrode layer11a, if a highly viscous conductive paste is applied by screen printing, the applied conductive paste is difficult to be leveled. Therefore, mesh traces are likely to appear on the surface of the first portion11A of the resin electrode layer11awhich is opposite to the first end surface9aof the resin molding9. From this point of view, the conductive paste for forming the resin electrode layer11apreferably has a viscosity of 25 Pa·s to 400 Pa·s, more preferably 30 Pa·s to 400 Pa·s, still more preferably 50 Pa·s. to 400 Pa·s, particularly preferably 100 Pa·s to 400 Pa·s.

By using the HB viscometer produced by Brookfield company, the viscosity of the conductive paste is measured as a viscosity when the spindle of No. 14 is rotated at 10 rpm at 25° C.

When forming the resin electrode layer11a, by adjusting the mesh pitch, wire diameter, aperture, etc. of the screen printing plate, it is possible to control various parameters of the resin electrode layer11asuch as the arithmetic mean roughness Ra of the surface of the first portion11A of the resin electrode layer11aas described above.

When forming the resin electrode layer11a, in addition to the first portion11A, a third portion11B is formed which extends from the first portion11A so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9. The conductive paste applied so as to face the whole surface of the first end surface9aof the resin molding9drips so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9, whereby the third portion11B of the resin electrode layer11ais formed. The plurality of protrusions15are not formed on a surface of the thus-formed third portion11B of the resin electrode layer11awhich is opposite to the resin molding9.

When the conductive paste is applied by screen printing, by moving the squeegee along the thickness direction T, in the third portion11B of the resin electrode layer11ato be formed, the length in the length direction L of portions which face the first main surface9cand the second main surface9dof the resin molding9are likely to be larger than the length in the length direction L of portions which face the first side surface9eand the second side surface9fof the resin molding9. Further, by moving the squeegee along the width direction W, in the third portion11B of the resin electrode layer11ato be formed, the length in the length direction L of portions which face the first side surface9eand the second side surface9fof the resin molding9are likely to be larger than the length in the length direction L of portions which face the first main surface9cand the second main surface9dof the resin molding9.

Preferably, the conductive component of the conductive paste for forming the resin electrode layer11amainly contains, an element metal such as silver, copper, nickel, or tin or an alloy containing at least one of these metals, for example.

Preferably, the resin component of the conductive paste for forming the resin electrode layer11amainly contains an epoxy resin, a phenolic resin, or the like.

The conductive paste for forming the resin electrode layer11apreferably contains the conductive component of 80% by weight to 97% by weight, and the resin component of 3% by weight to 20% by weight. The conductive paste for forming the resin electrode layer11amore preferably contains the conductive component of 85% by weight to 95% by weight, and the resin component of 5% by weight to 15% by weight. The conductive paste for forming the resin electrode layer11astill more preferably contains the conductive component of 90% by weight to 95% by weight, and the resin component of 5% by weight to 10% by weight. The conductive paste for forming the resin electrode layer11aparticularly preferably contains the conductive component of 92% by weight to 95% by weight, and the resin component of 5% by weight to 8% by weight.

The conductive paste for forming the resin electrode layer11amay contain an organic solvent. Glycol ether organic solvents are preferably used as the organic solvent. Examples of the glycol ether organic solvents include diethylene glycol monobutyl ether and diethylene glycol monophenyl ether.

The conductive paste for forming the resin electrode layer11amay contain an additive of less than 5% by weight. The additive is useful for adjusting the rheology, especially the thixotropy of the conductive paste.

When forming the resin electrode layer11a, the first portion11A facing the whole surface of the first end surface9aof the resin molding9may be formed by applying a conductive paste by sponge transfer printing.

Next, a plating treatment is performed on the resin electrode layer11a, whereby the outer plating layer11bis formed so as to be along the surfaces of the plurality of protrusions15of the first portion11A of the resin electrode layer11a. More specifically, as the outer plating layer11b, a first outer plating layer11baand a second outer plating layer11bbare formed in order from the resin electrode layer11aside.

When forming the first outer plating layer11ba, it is preferable to form a nickel plating layer by performing electrolytic nickel plating on the resin electrode layer11a.

When forming the second outer plating layer11bb, it is preferable that immediately after forming the first outer plating layer11ba, electrolytic tin plating is performed so that the first outer plating layer11badoes not come into contact with air, thereby forming a tin plating layer.

As a result, the first external electrode11connected to the anode3exposed at the first end surface9ais formed on the first end surface9aof the resin molding9. More specifically, the first external electrode11including the inner plating layer11c, the resin electrode layer11a, and the outer plating layer11bin the stated order from the anode3side is formed.

Forming Second External Electrode

First, a plating treatment is performed on the second end surface9bof the resin molding9to form an inner plating layer13cconnected to the cathode7, in this case, the cathode lead-out layer7c. More specifically, as the inner plating layer13c, a first inner plating layer13caand a second inner plating layer13cbare formed in order from the cathode7side.

When forming the first inner plating layer13ca, it is preferable that a nickel plating layer is formed on the second end surface9bof the resin molding9by the same method as the first inner plating layer11ca, but the zincate treatment may not be performed. However, when the cathode lead-out layer7ccontains aluminum as a main component, it is preferable to perform the zincate treatment.

When forming the second inner plating layer13cb, it is preferable that immediately after forming the first inner plating layer13ca, electrolytic silver plating is performed so that the first inner plating layer13cadoes not come into contact with air, thereby forming a silver plating layer.

Next, a conductive paste containing a conductive component and a resin component is applied to the second end surface9bof the resin molding9by screen printing so that a resin electrode layer13ais formed so as to include a second portion13A facing the whole surface of the second end surface9bof the resin molding9. As a result, the second portion13A of the resin electrode layer13ais formed so as to cover the inner plating layer13c. When forming the resin electrode layer13a, the mesh traces during screen printing are caused to appear on a surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9. As a result, a plurality of protrusions16arranged periodically side by side can be formed on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9.

Examples of a method for causing the mesh traces during screen printing to appear on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9include the following method.

When forming the resin electrode layer13a, the applied conductive paste is thermally cured. If the drying time (including a resting time) before thermal curing is shortened or a drying temperature is increased, the mesh traces are likely to appear on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9.

When forming the resin electrode layer13a, if a conductive paste having high thixotropy is applied by screen printing, the applied conductive paste is difficult to be leveled, so that mesh traces are likely to appear on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9. From this point of view, the conductive paste for forming the resin electrode layer13apreferably has a thixotropic index of 1.5 to 10.0, more preferably 1.5 to 7.0, and still more preferably 2.0 to 7.0, particularly preferably 3.0 to 7.0.

When forming the resin electrode layer13a, if a conductive paste having high viscosity is applied by screen printing, the applied conductive paste is difficult to be leveled, so that the mesh traces are likely to appear on the surface of the second portion13A of the resin electrode layer13awhich is opposite to the second end surface9bof the resin molding9. From this point of view, the conductive paste for forming the resin electrode layer13apreferably has a viscosity of 25 Pa·s to 400 Pa·s, more preferably 30 Pa·s to 400 Pa·s, still more preferably 50 Pa·s to 400 Pa·s, particularly preferably 100 Pa·s to 400 Pa·s.

When forming the resin electrode layer13a, by adjusting the mesh pitch, wire diameter, aperture, etc. of the screen printing plate, it is possible to control various parameters of the resin electrode layer13asuch as the arithmetic mean roughness Ra of the surface of the second portion13A of the resin electrode layer13aas described above.

When forming the resin electrode layer13a, in addition to the second portion13A, a fourth portion13B is formed which extends from the second portion13A so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9. The conductive paste applied so as to face the whole surface of the second end surface9bof the resin molding9drips so as to face respective parts of all the surfaces of the first main surface9c, the second main surface9d, the first side surface9e, and the second side surface9fof the resin molding9, whereby the fourth portion13B of the resin electrode layer13ais formed. The plurality of protrusions16are not formed on a surface of the thus-formed fourth portion13B of the resin electrode layer13awhich is opposite to the resin molding9.

When the conductive paste is applied by screen printing, by moving the squeegee along the thickness direction T, in the fourth portion13B of the resin electrode layer13ato be formed, the lengths in the length direction L of portions which face the first main surface9cand the second main surface9dof the resin molding9are likely to be larger than the lengths in the length direction L of portions which face the first side surface9eand the second side surface9fof the resin molding9. Further, by moving the squeegee along the width direction W, in the fourth portion13B of the resin electrode layer13ato be formed, the lengths in the length direction L of portions which face the first side surface9eand the second side surface9fof the resin molding9are likely to be larger than the lengths in the length direction L of portions which face the first main surface9cand the second main surface9dof the resin molding9.

Preferably, the conductive component of the conductive paste for forming the resin electrode layer13amainly contains, an element metal such as silver, copper, nickel, or tin or an alloy containing at least one of these metals, for example.

Preferably, the resin component of the conductive paste for forming the resin electrode layer13amainly contains an epoxy resin, a phenolic resin, or the like.

The conductive paste for forming the resin electrode layer13apreferably contains the conductive component of 80% by weight to 97% by weight, and the resin component of 3% by weight to 20% by weight. The conductive paste for forming the resin electrode layer13amore preferably contains the conductive component of 85% by weight to 95% by weight, and the resin component of 5% by weight to 15% by weight. The conductive paste for forming the resin electrode layer13astill more preferably contains the conductive component of 90% by weight to 95% by weight, and the resin component of 5% by weight to 10% by weight. The conductive paste for forming the resin electrode layer13aparticularly preferably contains the conductive component of 92% by weight to 95% by weight, and the resin component of 5% by weight to 8% by weight.

The conductive paste for forming the resin electrode layer13amay contain an organic solvent. Glycol ether organic solvent are preferably used as the organic solvent. Examples of the glycol ether organic solvents include diethylene glycol monobutyl ether and diethylene glycol monophenyl ether.

The conductive paste for forming the resin electrode layer13amay contain an additive of less than 5% by weight.

When forming the resin electrode layer13a, the second portion13A facing the whole surface of the second end surface9bof the resin molding9may be formed by applying a conductive paste by sponge transfer printing.

Next, a plating treatment is performed on the resin electrode layer13a, whereby the outer plating layer13bis formed so as to be along the surfaces of the plurality of protrusions16of the second portion13A of the resin electrode layer13a. More specifically, as the outer plating layer13b, a first outer plating layer13baand a second outer plating layer13bbare formed in order from the resin electrode layer13aside.

When forming the first outer plating layer13ba, it is preferable to form a nickel plating layer by performing electrolytic nickel plating on the resin electrode layer13a.

When forming the second outer plating layer13bb, it is preferable that immediately after forming the first outer plating layer13ba, electrolytic tin plating is performed so that the first outer plating layer13badoes not come into contact with air, thereby forming a tin plating layer.

As a result, the second external electrode13connected to the cathode7exposed at the second end face9bis formed on the second end surface9bof the resin molding9. More specifically, the second external electrode13including the inner plating layer13c, the resin electrode layer13a, and the outer plating layer13bin the stated order from the cathode7side is formed.

Forming the first external electrode and forming the second external electrode may be performed separately or simultaneously. When these steps are performed separately, the order is not limited.

Thus, the electrolytic capacitor1shown inFIGS.1,2, etc. is produced.

In the electrolytic capacitor1, the first external electrode11is connected to the anode3, and the second external electrode13is connected to the cathode7. As a modification, the first external electrode11may be connected to the cathode7, and the second external electrode13may be connected to the anode3. In this case, it is only required that the anode3is exposed at the second end surface9bof the resin molding9and the cathode7is exposed at the first end surface9aof the resin molding9.

Embodiment 2

In an electronic component of the present invention, the base body may be formed of a stack including at least one ceramic layer selected from the group consisting of a dielectric ceramic layer, a magnetic ceramic layer, a piezoelectric ceramic layer, and a semiconductor ceramic layer, the first internal electrode layer and the second internal electrode layer. Such an electronic component corresponds to a multilayer ceramic electronic component such as a multilayer ceramic capacitor, a multilayer coil, a multilayer thermistor, a multilayer varistor, a multilayer LC filter, or a multilayer piezoelectric filter. In the following description, the multilayer ceramic capacitor out of the examples of the multilayer ceramic electronic component will be described as an electronic component of Embodiment 2 of the present invention. The electronic component of Embodiment 2 of the present invention is the same as the electronic component of Embodiment 1 of the present invention except that the configurations of the base body and the internal electrode are different.

FIG.6is a schematic cross-sectional view showing the electronic component of Embodiment 2 of the present invention.

As shown inFIG.6, a multilayer ceramic capacitor101includes a stack109, a first external electrode111, and a second external electrode113.

The stack109corresponds to the base body in the electronic component of the present invention.

The stack109has a substantially rectangular parallelepiped shape, and includes a first end surface109aand a second end surface109bopposite to each other in a length direction L, a first main surface109cand a second main surface109dopposite to each other in a thickness direction T, and a first side surface and a second side surface (not shown) opposite to each other in a width direction W.

The first end surface109aand the second end surface109bof the stack109are not required to be strictly perpendicular to the length direction L. Moreover, the first main surface109cand the second main surface109dof the stack109are not required to be strictly perpendicular to the thickness direction T. Furthermore, the first side surface and the second side surface of the stack109are not required to be strictly perpendicular to the width direction W.

The stack109includes a stack of a first internal electrode layer103, a second internal electrode layer107, and a dielectric ceramic layer108.

The first internal electrode layer103and the second internal electrode layer107correspond to the first internal electrode and the second internal electrode in the electronic component of the present invention, respectively.

Each of the first internal electrode layer103and the second internal electrode layer107is preferably a nickel electrode layer containing nickel as a main component of a conductive component.

Each of the first internal electrode layer103and the second internal electrode layer107may be a silver electrode layer containing silver as the main component of the conductive component, a copper electrode layer containing copper as the main component of the conductive component, or a palladium electrode layer containing palladium as the main component of the conductive component.

Each of the first internal electrode layer103and the second internal electrode layer107is formed, for example, by applying a conductive paste including a conductive component containing nickel, silver, copper, palladium or the like as a main component by screen printing or the like.

The first internal electrode layer103is exposed at the first end surface109aof the stack109and connected to the first external electrode111.

The second internal electrode layer107is exposed at the second end surface109bof the stack109and connected to the second external electrode113.

The dielectric ceramic layer108contains, for example, dielectric ceramic such as barium titanate.

The dielectric ceramic layer108is formed, for example, by performing sheet-molding using dielectric slurry containing a dielectric ceramic and an organic solvent.

The first external electrode111is provided on the first end surface109aof the stack109. The first external electrode111may extend from the first end surface109aof the stack109to a part of each surface in at least one surface selected from the group consisting of the first main surface109c, the second main surface109d, the first side surface, and the second side surface.

The first external electrode111is connected to the first internal electrode layer103exposed at the first end surface109aof the stack109.

The first external electrode111has the same configuration as the first external electrode11except that it does not include the inner plating layer11c. The form of the first external electrode111, particularly the form of the resin electrode layer11ais also the same as described above.

The second external electrode113is provided on the second end surface109bof the stack109. The second external electrode113may extend from the second end surface109bof the stack109to a part of each surface in at least one surface selected from the group consisting of the first main surface109c, the second main surface109d, the first side surface, and the second side surface.

The second external electrode113is connected to the second internal electrode layer107exposed at the second end surface109bof the stack109.

The second external electrode113has the same configuration as the second external electrode13except that it does not include the inner plating layer13c. The form of the second external electrode113, particularly the form of the resin electrode layer13ais also the same as described above.

A method of producing an electronic component of Embodiment 2 of the present invention, that is, a method of producing the multilayer ceramic capacitor101shown inFIG.6is the same as the method of producing the electronic component of Embodiment 1 of the present invention except that the stack109is formed instead of the resin molding9, the inner plating layer11cis not formed in forming the first external electrode and the inner plating layer13cis not formed in forming the second external electrode.

A method known in the field of multilayer ceramic capacitors can be used in forming the stack109.

In the multilayer ceramic capacitor101, the first external electrode111is connected to the first internal electrode layer103, and the second external electrode113is connected to the second internal electrode layer107. As a modification, the first external electrode111may be connected to the second internal electrode layer107, and the second external electrode113may be connected to the first internal electrode layer103. In this case, it is only required that the first internal electrode layer103is exposed at the second end surface109bof the stack109, and the second internal electrode layer107is exposed at the first end surface109aof the stack109.

Embodiment 3

When the electronic component of the present invention is a multilayer ceramic electronic component, the first external electrode may further include a baked electrode layer provided between the base body and the resin electrode layer. The second external electrode may further include a baked electrode layer provided between the base body and the resin electrode layer. In the following description, a multilayer ceramic capacitor out of such examples of the multilayer ceramic electronic component will be described as an electronic component of Embodiment 3 of the present invention. The electronic component of Embodiment 3 of the present invention is the same as the electronic component of Embodiment 2 of the present invention except that it includes a baked electrode layer.

FIG.7is a schematic cross-sectional view showing an electronic component of Embodiment 3 of the present invention.

As shown inFIG.7, a multilayer ceramic capacitor201includes a stack109, a first external electrode211, and a second external electrode213.

The first external electrode211is provided on a first end surface109aof the stack109. The first external electrode211may extend from the first end surface109aof the stack109to a part of each surface in at least one surface selected from the group consisting of a first main surface109c, a second main surface109d, a first side surface, and a second side surface.

The first external electrode211is connected to a first internal electrode layer103exposed at the first end surface109aof the stack109.

The first external electrode211further includes a baked electrode layer11dprovided between the stack109and a resin electrode layer11a.

The baked electrode layer11dmay be provided not only between the stack109and a first portion11A of the resin electrode layer11a, but also between the stack109and a third portion11B of the resin electrode layer11a.

The second external electrode213is provided on a second end surface109bof the stack109. The second external electrode213may extend from the second end surface109bof the stack109to a part of each surface in at least one surface selected from the group consisting of the first main surface109c, the second main surface109d, the first side surface, and the second side surface.

The second external electrode213is connected to a second internal electrode layer107exposed at the second end surface109bof the stack109.

The second external electrode213further includes a baked electrode layer13dprovided between the stack109and the resin electrode layer13a.

The baked electrode layer13dmay be provided not only between the stack109and a second portion13A of the resin electrode layer13a, but also between the stack109and a fourth portion13B of the resin electrode layer13a.

Each of the baked electrode layer11dand the baked electrode layer13dis preferably a baked copper electrode layer containing copper as a main component of a conductive component.

Each of the baked electrode layer11dand the baked electrode layer13dmay be a baked silver electrode layer containing silver as the main component of the conductive component, or may be a baked nickel electrode layer containing nickel as the main component of the conductive component.

Each of the baked electrode layer11dand the baked electrode layer13dmay contain glass.

Each of the baked electrode layer11dand the baked electrode layer13dis formed, for example, by applying a conductive paste including a conductive component containing copper, silver, nickel or the like as a main component by screen printing or the like, and then baking the applied conductive paste.

A method of producing an electronic component of Embodiment 3 of the present invention, that is, a method of producing a multilayer ceramic capacitor201shown inFIG.7is the same as the method of producing the electronic component of Embodiment 2 of the present invention except that the baked electrode layer11dis formed in forming the first external electrode and the baked electrode layer13dis formed in forming the second external electrode.

In forming the first external electrode, before forming the resin electrode layer11a, the conductive paste is applied to the first end surface109aof the stack109by screen printing or the like, and then baked to form the baked electrode layer11d.

When forming the baked electrode layer11d, the baking temperature is preferably set to 700° C. to 900° C. Further, it is preferable to perform the baking in a non-oxidizing atmosphere.

The conductive component of the conductive paste for forming the baked electrode layer11dpreferably contains copper as a main component. The conductive component of the conductive paste for forming the baked electrode layer11dmay contain silver, nickel, or the like as a main component.

In forming the second external electrode, before forming the resin electrode layer13a, the conductive paste is applied to the second end surface109bof the stack109by screen printing or the like and then baked to form the baked electrode layer13d.

When forming the baked electrode layer13d, the baking temperature is preferably set to 700° C. to 900° C. Further, it is preferable to perform the baking in a non-oxidizing atmosphere.

The conductive component of the conductive paste for forming the baked electrode layer13dpreferably contains copper as a main component. The conductive component of the conductive paste for forming the baked electrode layer13dmay contain silver, nickel, or the like as a main component.

In the multilayer ceramic capacitor201, the first external electrode211is connected to the first internal electrode layer103, and the second external electrode213is connected to the second internal electrode layer107. As a modification, the first external electrode211may be connected to the second internal electrode layer107, and the second external electrode213may be connected to the first internal electrode layer103. In this case, it is only required that the first internal electrode layer103is exposed at the second end surface109bof the stack109, and the second internal electrode layer107is exposed at the first end surface109aof the stack109.

EXAMPLES

Examples that more specifically disclose the electronic component of the present invention are described below. In the following examples, an electrolytic capacitor is described as the electronic component of the present invention. The present invention is not limited to these examples.

Example 1

An electrolytic capacitor of Example 1 was produced by the following method.

Forming Resin Molding

A resin molding having the structure shown inFIG.2was formed by sealing the periphery of a stack of an electrolytic capacitor element with a sealing resin.

Forming First External Electrode

First, a zincate treatment was performed by etching a surface of a valve-action metal substrate exposed at a first end surface of a resin molding with an acid containing nitric acid as a main component, and then forming a zinc coating on the surface of the valve-action metal substrate. Thereafter, electroless nickel plating and electrolytic silver plating were sequentially performed on the first end surface of the resin molding to form an inner plating layer having a two-layer structure of a nickel plating layer and a silver plating layer.

Next, after applying a silver paste by screen printing, the applied silver paste was thermally cured at a heat treatment temperature (for example, 150° C. to 200° C.) suitable for the silver paste, whereby a resin electrode layer was formed so as to include a first portion facing the whole surface of the first end surface of the resin molding while covering the inner plating layer. A plurality of protrusions were arranged periodically side by side due to mesh traces caused during screen printing on a surface of the first portion of the resin electrode layer which was opposite to the first end surface of the resin molding.

The silver paste for forming the resin electrode layer had a thixotropic index of 1.5 and a viscosity of 31 Pa·s.

Next, the resin electrode layer was subjected to electrolytic nickel plating and electrolytic tin plating in the stated order, whereby an outer plating layer having a two-layer structure of a nickel plating layer and a tin plating layer was formed along the surfaces of the plurality of protrusions of the first portion of the resin electrode layer.

In this way, the first external electrode including the inner plating layer, the resin electrode layer, and the outer plating layer in the stated order from the anode side was formed.

Forming Second External Electrode

First, a zincate treatment was performed by etching a surface of a cathode lead-out layer exposed at a second end surface of a resin molding with an acid containing nitric acid as a main component, and then forming a zinc coating on the surface of the cathode lead-out layer. Thereafter, electroless nickel plating and electrolytic silver plating were sequentially performed on the second end surface of the resin molding to form an inner plating layer having a two-layer structure of a nickel plating layer and a silver plating layer.

Next, after applying a silver paste by screen printing, the applied silver paste was thermally cured at a heat treatment temperature (for example, 150° C. to 200° C.) suitable for the silver paste, whereby a resin electrode layer was formed so as to include a first portion facing the whole surface of the second end surface of the resin molding while covering the inner plating layer. A plurality of protrusions were arranged periodically side by side due to mesh traces caused during screen printing on a surface of the first portion of the resin electrode layer which was opposite to the second end surface of the resin molding.

The silver paste for forming the resin electrode layer had a thixotropic index of 1.5 and a viscosity of 31 Pa·s.

Next, the resin electrode layer was subjected to electrolytic nickel plating and electrolytic tin plating in the stated order, whereby an outer plating layer having a two-layer structure of a nickel plating layer and a tin plating layer was formed along the surfaces of the plurality of protrusions of the first portion of the resin electrode layer.

In this way, the second external electrode including the inner plating layer, the resin electrode layer, and the outer plating layer in the stated order from the cathode side was formed.

Thus, the electrolytic capacitor of Example 1 was produced.

Examples 2 to 13

Electrolytic capacitors of Examples 2 to 13 were produced in the same manner as used for the electrolytic capacitor of Example 1 except that the thixotropic index and viscosity of the silver paste for forming the resin electrode layer used in forming the first external electrode and forming the second external electrode were changed as shown in Table 1.

Comparative Example 1

An electrolytic capacitor of Comparative Example 1 was produced in the same manner as used for the electrolytic capacitor of Example 2 except that the resin electrode layer was formed by applying a silver paste by immersion coating in forming the first external electrode and forming the second external electrode.

Evaluation

The electrolytic capacitors of Examples 1 to 13 and Comparative Example 1 were evaluated as follows. Table 1 shows the results.

Appearance

For the electrolytic capacitor of each Example, the appearances of the first external electrode and the second external electrode were visually confirmed. Evaluation criteria were as follows.

Excellent: It was possible to very clearly confirm a state in which a plurality of protrusions were arranged periodically side by side.

Good: It was possible to clearly confirm a state in which a plurality of protrusions were arranged periodically side by side.

Acceptable: It was possible to confirm a state in which a plurality of protrusions were arranged periodically side by side.

Poor: It was not possible to confirm existence of a plurality of protrusions or it was not possible to confirm a state in which a plurality of protrusions were arranged periodically side by side although the plurality of protrusions existed.

Bonding Strength

The electrolytic capacitor of each Example was mounted on a wiring board via solder. Then, the bonding strength of the solder to the first external electrode and the second external electrode was measured by using a bond tester “DAGE 4000 Optima” manufactured by Nordson company. With respect to conditions for measuring the bonding strength, a tool speed was set to 100.0 μm/s, a tool movement amount was set to 100 μm, and a test height was set to 500 μm.

TABLE 1SpecificationsSilver paste for formingresin electrode layerEvaluationThixot-Viscos-BondingApplicationropicitystrengthmethodindex(Pa · s)Appearance(N)Example 1Screen1.531Acceptable68printingExample 2Screen1.835Acceptable70printingExample 3Screen2.031Good75printingExample 4Screen2.533Good78printingExample 5Screen2.835Good83printingExample 6Screen3.031Excellent90printingExample 7Screen5.033Excellent93printingExample 8Screen7.035Excellent98printingExample 9Screen1.550Good81printingExample 10Screen1.8100Good85printingExample 11Screen1.8200Good87printingExample 12Screen2.0300Excellent91printingExample 13Screen7.0400Excellent105printingComparativeImmersion1.835Poor55Example 1coating

As shown in Table 1, in the electrolytic capacitors of Examples 1 to 13 in which the silver paste for forming the resin electrode layer was applied by screen printing, a plurality of protrusions caused by mesh traces during screen printing were arranged periodically side by side at the first external electrode and the second external electrode. Therefore, in the electrolytic capacitors of Examples 1 to 13, the bonding strength of the solder to the first external electrode and the second external electrode was high. In other words, with respect to the electrolytic capacitors of Examples 1 to 13, it was found that the adhesion between the first external electrode and the solder and the adhesion between the second external electrode and the solder were enhanced when each electrolytic capacitor was mounted on the wiring board via the solder.

Among the electrolytic capacitors of Examples 1 to 13, focusing on the electrolytic capacitors of Example 2, Example 5, and Example 8 in which the viscosity of the silver paste for forming the resin electrode layer was the same, it was found that mesh traces during screen printing was more likely to appear at the first external electrode and the second external electrode and thus the bonding strength of the solder to the first external electrode and the second external electrode was enhanced as the thixotropic index of the silver paste for forming the resin electrode layer increased.

Among the electrolytic capacitors of Examples 1 to 13, focusing on the electrolytic capacitors of Example 2, Example 10, and Example 11 in which the thixotropic index of the silver paste for forming the resin electrode layer was the same, it was found that mesh traces during screen printing was more likely to appear at the first external electrode and the second external electrode and thus the bonding strength of the solder to the first external electrode and the second external electrode was enhanced when the viscosity of the silver paste for forming the resin electrode layer increased greatly.

On the other hand, in the electrolytic capacitor of Comparative Example 1 in which the silver paste for forming the resin electrode layer was applied by immersion coating, a plurality of protrusions were not present at the first external electrode and the second external electrode. Therefore, in the electrolytic capacitor of Comparative Example 1, the bonding strength of the solder to the first external electrode and the second external electrode was lower than those of the electrolytic capacitors of Examples 1 to 13.

REFERENCE SIGNS LIST

1electrolytic capacitor3anode3avalve-action metal substrate5dielectric layer7cathode7asolid electrolyte layer7bconductive layer7ccathode lead-out layer8sealing resin9resin molding9a,109afirst end surface9b,109bsecond end surface9c,109cfirst main surface9d,109dsecond main surface9efirst side surface9fsecond side surface11,111,211first external electrode11a,13aresin electrode layer11b,13bouter plating layer11ba,13bafirst outer plating layer11bb,13bbsecond outer plating layer11c,13cinner plating layer11ca,13cafirst inner plating layer11cb,13cbsecond inner plating layer11d,13dbaked electrode layer11A first portion13A second portion11Aa,13Aa bottom surface11Ab,13Ab top surface11B third portion13B fourth portion13,113,213second external electrode15,15A,16,16A Protrusion20electrolytic capacitor element30,109stack50wiring board51printing board52,53land electrode54conductive bonding material101,201multilayer ceramic capacitor103first internal electrode layer107second internal electrode layer108dielectric ceramic layerL length directionLa shortest distance in length direction between bottom surface and first end surfaceLb shortest distance in length direction between bottom surface and second end surfaceT thickness directionTaa, Tab length in thickness direction of bottom surfaceTba, Tbb length in thickness direction of top surfaceTpa, Tpb shortest distance in thickness direction between top surfacesW width direction