Method for manufacturing solid electrolytic capacitor element

Abstract

A method for manufacturing a solid electrolytic capacitor element 30 comprising: a step for supplying a cathode paste onto a pair of rollers; a step for conveying, to a portion between the pair of rollers to which the cathode paste has been supplied, an aggregate 10 of solid electrolytic capacitor elements each provided with an element part 11 that has a pair of principal surfaces 11a, 11b, a pair of side surfaces 11c, 11d, and an end surface 11e; and a step for transferring the cathode paste on the pair of rollers onto the pair of principal surfaces 11a, 11b, and then connecting, on the pair of side surfaces 11c, 11d and on the end surface 11e, the cathode paste that has been transferred onto the pair of principal surfaces 11a, 11b.

Description

Method for manufacturing a solid electrolytic capacitor element

[0001] The present invention relates to a method for manufacturing a solid electrolytic capacitor element.

[0002] Patent Document 1 describes a method for manufacturing a solid electrolytic capacitor, which includes the steps of providing an anode lead portion and a cathode formation portion of a capacitor element on both sides of a valve action metal foil on which a dielectric oxide film has been formed, and coating the cathode formation portion with an insulating coating while leaving the cathode formation portion in a grid pattern, a step of forming a solid electrolyte layer on the cathode formation portion, a step of drilling through holes in at least part of the outer periphery of the cathode formation portion and then chemically converting the cross section of the cathode formation portion within the through hole, a step of forming a cathode conductive layer on the solid electrolyte and on the cross section of the through hole, and a step of cutting out capacitor elements for each grid to manufacture products, wherein the step of forming the cathode conductive layer is characterized in that the cathode conductive layer is formed by transfer printing a conductive paste.

[0003] Japanese Patent Application Laid-Open No. 2005-268681

[0004] In Patent Document 1, the conductive paste is simultaneously applied to the cathode forming portions on both sides of the capacitor element and to the cross sections of the through holes provided on the outer periphery of the cathode forming portions, so that the cathode conductive layers formed on both sides of the capacitor element can be electrically conductive without creating an interface of the conductive coating film.

[0005] The solid electrolytic capacitor described in Patent Document 1 is a three-terminal solid electrolytic capacitor, which has anode lead portions on both ends of a capacitor element, a cathode forming portion between the two anode lead portions, and through holes provided on the outer periphery of the cathode forming portion are formed only on two side surfaces of the cathode forming portion. However, as shown in Figure 5 of Patent Document 1, in a three-terminal solid electrolytic capacitor, the volume of the capacitance obtaining portion of the capacitor element is small relative to the volume of the solid electrolytic capacitor, making it difficult to increase the capacitance.

[0006] On the other hand, a two-terminal solid electrolytic capacitor has an anode lead portion at one end of the capacitor element and a cathode lead portion at the other end. Compared to a three-terminal solid electrolytic capacitor, the volume of the capacitance acquisition portion of the capacitor element is larger relative to the volume of the solid electrolytic capacitor, allowing for higher capacitance. However, in a two-terminal solid electrolytic capacitor, the cathode-forming portion has two side surfaces and one end surface, making it difficult to apply the manufacturing method for a three-terminal solid electrolytic capacitor described in Patent Document 1. For example, when a through hole is formed as described in Patent Document 1, conductive paste is applied to the two side surfaces of the cathode-forming portion, but no through hole is formed in the area that will become one end surface of the cathode-forming portion, and therefore no conductive paste is applied. Therefore, it becomes necessary to further cut the outer periphery of the cathode-forming portion to form the end surface of the cathode-forming portion, and then separately form a chemical conversion film, a solid electrolyte layer, and a conductive paste layer on that end surface, which complicates the manufacturing process.

[0007] The present invention has been made to solve the above problems, and aims to provide a method for manufacturing a solid electrolytic capacitor element that can form a cathode of a solid electrolytic capacitor element used in a two-terminal solid electrolytic capacitor in a simple process.

[0008] A method for manufacturing a solid electrolytic capacitor element of the present invention includes the steps of supplying a cathode paste onto a pair of rollers; transporting an assembly of solid electrolytic capacitor elements including an element portion having a pair of main surfaces, a pair of side surfaces, and an end surface between the pair of rollers onto which the cathode paste has been supplied; and transferring the cathode paste on the pair of rollers to the pair of main surfaces, and connecting the cathode paste transferred to the pair of main surfaces on the pair of side surfaces and the end surfaces.

[0009] According to the present invention, it is possible to provide a method for manufacturing a solid electrolytic capacitor element that can form the cathode of the solid electrolytic capacitor element used in a two-terminal solid electrolytic capacitor in a simple process.

[0010] FIG. 1 is a plan view schematically showing an example of an assembly of solid electrolytic capacitor elements (strip structure type) used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing an example of a process of performing a masking treatment for chemical conversion on element portions of an assembly of solid electrolytic capacitor elements. FIG. 3 is a plan view schematically showing an example of a process of performing a masking treatment for polarization (polarization treatment) on element portions of an assembly of solid electrolytic capacitor elements. FIG. 4 is a plan view schematically showing an example of a process of forming a solid electrolyte layer on element portions of an assembly of solid electrolytic capacitor elements. FIG. 5 is a cross-sectional view taken along line X-X of the element portion shown in FIG. 4. FIG. 6 is an enlarged cross-sectional view of the polarized portion of the element portion shown in FIG. 5. FIG. 7 is a plan view schematically showing another example of an assembly of solid electrolytic capacitor elements (double-door structure type) used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 8 is a plan view schematically showing yet another example of an assembly of solid electrolytic capacitor elements (strip structure type) used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 9 is a plan view schematically showing yet another example (double-door structure type) of an assembly of solid electrolytic capacitor elements used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 10 is a plan view schematically showing an example of a process for forming a carbon layer on the element portion of the assembly of solid electrolytic capacitor elements. FIG. 11 is a plan view schematically showing an example of a process for forming a silver layer on the element portion of the assembly of solid electrolytic capacitor elements. FIG. 12 is a schematic diagram of an example of a roller transfer device used for roller transfer of cathode paste. FIG. 13 is a schematic diagram of another example of a roller transfer device used for roller transfer of cathode paste. FIG. 14 is a perspective view schematically showing the appearance of one side of the element portion of the assembly of solid electrolytic capacitor elements to which the cathode paste has been roller-transferred. FIG. 15 is a perspective view schematically showing the appearance of the other side of the element portion of the assembly of solid electrolytic capacitor elements to which the cathode paste has been roller-transferred. FIG. 16 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element produced by the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention, and corresponds to the cross-sectional view shown in FIG. 5. FIG. 17 is a cross-sectional view taken along line YY of the solid electrolytic capacitor element shown in FIG.FIG. 18 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor.

[0011] The following describes a method for manufacturing a solid electrolytic capacitor element. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual desirable configurations described below also falls within the scope of the present invention.

[0012] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0013] In this specification, terms indicating the relationship between elements (e.g., "parallel," "perpendicular," "orthogonal," etc.) and terms indicating the shapes of elements not only mean the literal strict form, but also mean a range that is substantially equivalent, for example, a range that includes a difference of about a few percent.

[0014] A method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention includes the steps of supplying a cathode paste onto a pair of rollers; transporting an assembly of solid electrolytic capacitor elements, each including an element portion having a pair of main surfaces, a pair of side surfaces, and an end surface, between the pair of rollers onto which the cathode paste has been supplied; and transferring the cathode paste on the pair of rollers to the pair of main surfaces, and connecting the cathode paste transferred to the pair of main surfaces on the pair of side surfaces and the end surfaces.

[0015] In this way, a solid electrolytic capacitor element assembly having an element portion having a pair of main surfaces, a pair of side surfaces, and an end surface is prepared, and the assembly is transported between a pair of rollers to which cathode paste is supplied. The cathode paste on the pair of rollers is transferred to the pair of main surfaces of the element portion, and the cathode paste transferred to the pair of main surfaces is connected on the pair of side surfaces and end surfaces of the element portion. This allows the cathode of a solid electrolytic capacitor element used in a two-terminal solid electrolytic capacitor to be formed in a simple process. Furthermore, the cathode paste layer can be integrally formed on both main surfaces, both side surfaces, and one end surface of the element portion in the cathode forming portion. That is, the cathode paste layers supplied on each surface can be seamlessly formed without creating an interface between them. As a result, the ESR (equivalent series resistance) of the solid electrolytic capacitor element can be reduced. Furthermore, since the cathode forming portion of the solid electrolytic capacitor element is sealed without interruption by the cathode, the moisture resistance reliability of the solid electrolytic capacitor element is improved.

[0016] Hereinafter, the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention will be described in more detail with reference to the drawings.

[0017] FIG. 1 is a plan view schematically showing an example of an assembly of solid electrolytic capacitor elements (strip structure type) used in a manufacturing method of a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing an example of a process of performing a masking treatment for chemical conversion on element portions of an assembly of solid electrolytic capacitor elements. FIG. 3 is a plan view schematically showing an example of a process of performing a masking treatment for polarization (polarization treatment) on element portions of an assembly of solid electrolytic capacitor elements. FIG. 4 is a plan view schematically showing an example of a process of forming a solid electrolyte layer on element portions of an assembly of solid electrolytic capacitor elements. FIG. 5 is a cross-sectional view taken along line X-X of the element portion shown in FIG. 4. FIG. 6 is an enlarged cross-sectional view of the polarization portion of the element portion shown in FIG. 5.

[0018] 1 to 4, an assembly 10 of solid electrolytic capacitor elements is prepared, which includes a plurality of element portions 11. Each element portion 11 has a pair of main surfaces 11a and 11b, a pair of side surfaces 11c and 11d, and one end surface 11e.

[0019] 5 and 6 , each element unit 11 has a rectangular flat plate shape in a plan view, and includes an anode foil 31 having a porous surface made of a valve action metal substrate, a dielectric layer 33 (see FIG. 6 , not shown in FIG. 5 ) provided on the surface of the anode foil 31, two insulating mask materials 35 and 37 that are annular (extending in a strip-like shape) insulating members provided around the anode foil 31 with the dielectric layer 33 interposed therebetween, and a solid electrolyte layer 39 provided on the anode foil 31 with the dielectric layer 33 interposed therebetween, on the end face 11 e side of the insulating mask material 37. In each element unit 11, the solid electrolyte layer 39 faces the anode foil 31 with the dielectric layer 33 interposed therebetween.

[0020] As shown in FIG. 4, the solid electrolytic capacitor element assembly 10 includes a belt-shaped holding portion 13 in which a plurality of element portions 11 are connected at regular intervals.

[0021] Each step shown in FIGS. 1 to 4 will be described below.

[0022] First, as shown in FIG. 1 , an anode foil 31 is cut into the shape of a solid electrolytic capacitor element (preferably rectangular) by laser processing, punching, or the like, and then welded to a conveying substrate 15 serving as a holding portion 13, for example, to produce an assembly 10 of solid electrolytic capacitor elements.

[0023] As described above, the assembly 10 of solid electrolytic capacitor elements includes a conveying substrate 15 made of a metal or resin material that is provided parallel to the conveying direction in which the assembly 10 is conveyed in the cathode paste transfer process described below, and the element portion 11 is provided on only one side of the conveying substrate 15. The side surfaces 11c and 11d of the element portion 11 extend in a direction perpendicular to the conveying direction (holding portion 13), and the end surface 11e of the element portion 11 extends parallel to the conveying direction (holding portion 13).

[0024] A valve metal substrate having a porous portion on its surface is used as the anode foil 31 constituting the element portion 11. As shown in Fig. 6, the anode foil 31 is a thin film (foil) having a rectangular shape in a plan view, and including a metal substrate portion 31a and a porous portion 31b on the metal substrate portion 31a. A dielectric layer 33 is provided on the surface of the porous portion 31b.

[0025] In this specification, the term "plan view" means a view from the normal direction of the main surface of the anode foil.

[0026] The valve metal substrate is made of a valve metal such as an elemental metal such as aluminum, tantalum, niobium, titanium, or zirconium, or an alloy containing these metals.

[0027] The valve metal substrate may be formed of a core and a porous portion provided on at least one of the main surfaces of the core, and may be formed from a metal foil having an etched surface, a metal foil having a porous sintered powder body formed on the surface, or the like.

[0028] FIG. 7 is a plan view schematically showing another example (double-door structure type) of an assembly of solid electrolytic capacitor elements used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention.

[0029] The solid electrolytic capacitor element assembly 10 is not particularly limited to the strip structure type shown in Fig. 1, but may also have a double-open structure (fishbone structure) type as shown in Fig. 7. In this case, the element portions 11 are provided on both sides of the conveying substrate 15.

[0030] Examples of the metal material for the transport substrate 15 include aluminum and stainless steel. Examples of the resin material for the transport substrate 15 include fluororesin, phenolic resin, and glass-epoxy resin composites.

[0031] In any case, unlike the anode foil 31, the transport base material 15 is a highly rigid member, and can prevent the solid electrolytic capacitor element assembly 10 from flapping even in the cathode paste transfer step described below.

[0032] Fig. 8 is a plan view schematically showing yet another example (strip structure type) of an assembly of solid electrolytic capacitor elements used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention. Fig. 9 is a plan view schematically showing yet another example (double-door structure type) of an assembly of solid electrolytic capacitor elements used in the method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention.

[0033] The solid electrolytic capacitor element assembly 10 does not necessarily have to include the conveying substrate 15 shown in FIGS. 1 and 7 , but may instead include, as shown in FIGS. 8 and 9 , bones 17 as holding portions 13, which are arranged parallel to the conveying direction in which the assembly 10 is conveyed in the cathode paste transfer step described below. In this case, the element portions 11 contain the same material as the bone portions 17. Specifically, both are made of the same valve metal substrate and are formed by cutting the same anode foil. The element portions 11 may be provided on only one side of the bone portion 17 (strip structure type) as shown in FIG. 8 , or may be provided on both sides of the bone portion 17 (double-open structure (fishbone structure) type) as shown in FIG. 9 .

[0034] Next, as shown in FIG. 2, an insulating mask material 35 is applied to the element portion 11, and a masking process for chemical conversion is carried out.

[0035] The insulating mask material 35 is formed by applying a mask material such as a composition containing an insulating resin by screen printing, roller transfer, dispenser, inkjet printing, etc. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, etc.), a composition consisting of soluble polyimidesiloxane and epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

[0036] When the bone portion 17 is used instead of the transport substrate 15, the entire bone portion 17 is subjected to chemical conversion treatment, and the polarization of the anode and cathode is carried out separately, so that the masking treatment for chemical conversion is not required.

[0037] Next, the solid electrolytic capacitor element assembly 10 is subjected to a chemical conversion treatment (anodic oxidation treatment). This forms an oxide film that serves as a dielectric layer on the surface of the valve metal substrate. For example, the dielectric layer is made of aluminum oxide. At this time, an oxide film is also formed on the pair of side faces 11c and 11d and one end face 11e of the element portion 11 that has been cut by laser processing, punching, or the like.

[0038] Alternatively, a chemically-formed foil on which aluminum oxide has already been formed may be used as the valve metal substrate. In this case, too, a chemical conversion treatment is performed on the valve metal substrate after cutting, thereby forming an oxide film on the pair of side faces 11c and 11d and one end face 11e of the cut element portion 11.

[0039] Next, as shown in FIG. 3, an insulating mask material 37 is applied to the element portion 11, and a masking process (polarization process) for polarization of the anode portion and the cathode portion is performed.

[0040] The insulating mask material 37 is formed by applying a mask material such as a composition containing an insulating resin by screen printing, roller transfer, dispenser, inkjet printing, etc. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, etc.), a composition consisting of soluble polyimidesiloxane and epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

[0041] Next, as shown in FIG. 4 , a solid electrolyte layer 39 is formed on the dielectric layer of the element portion 11. Specifically, the element portion 11 is immersed in a treatment liquid containing a solid electrolyte, thereby impregnating the porous portion of the valve metal substrate with the treatment liquid. After immersion for a predetermined time, the element portion 11 is removed from the treatment liquid and dried at a predetermined temperature for a predetermined time. The solid electrolyte layer 39 is formed by repeating the immersion in the treatment liquid, removal, and drying process a predetermined number of times. The solid electrolyte layer 39 may also be formed by repeating a predetermined number of times of immersion in a treatment liquid containing a solid electrolyte precursor (a monomer that becomes a solid electrolyte by oxidative polymerization) and further immersion in a treatment liquid containing an oxidizing agent that oxidatively polymerizes the solid electrolyte precursor.

[0042] The method for forming the solid electrolyte layer 39 (the method for applying the treatment liquid containing the solid electrolyte or the treatment liquid containing the precursor of the solid electrolyte) is not particularly limited to the immersion method described above, and may be, for example, application using a dispenser or roller transfer. Furthermore, these methods may be combined.

[0043] The solid electrolyte layer 39 is formed over the entire device portion 11 on the end face 11e side of the insulating mask material 37. The solid electrolyte layer 39 may be in contact with the insulating mask material 37, as shown in FIGS.

[0044] The solid electrolyte layer 39 is provided on the dielectric layer 33. As shown in Fig. 6 , the solid electrolyte layer 39 is preferably provided so as to fill a plurality of pores (recesses) in the porous portion 31b of the anode foil 31. However, it is sufficient that the solid electrolyte layer 39 covers part of the outer surface of the dielectric layer 33, and there may be pores (recesses) in the porous portion 31b of the anode foil 31 that are not filled with the solid electrolyte layer 39.

[0045] As a treatment liquid containing a solid electrolyte, for example, a dispersion of a conductive polymer such as polypyrroles, polythiophenes, or polyanilines is used. Among these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene), also known as PEDOT, is particularly preferred. Furthermore, the conductive polymer may contain a dopant such as polystyrene sulfonic acid (PSS). A conductive polymer film can be formed by applying a dispersion of a conductive polymer to the outer surface of the dielectric layer and drying it. Alternatively, a liquid containing a polymerizable monomer, such as 3,4-ethylenedioxythiophene, may be used as a treatment liquid containing a solid electrolyte precursor. The polymerizable monomer may contain a dopant, such as polystyrene sulfonic acid. Furthermore, the treatment liquid containing a solid electrolyte precursor may contain an oxidizing agent. This treatment liquid can be applied to the outer surface of the dielectric layer to form a conductive polymer film by oxidative polymerization (chemical polymerization). This conductive polymer film becomes the solid electrolyte layer 39.

[0046] FIG. 10 is a plan view schematically showing an example of a process for forming a carbon layer on the element portion of an assembly of solid electrolytic capacitor elements.

[0047] Next, a carbon paste is transferred as a cathode paste to each element portion 11 of the solid electrolytic capacitor element assembly 10 by roller transfer, forming a carbon layer 41 on each element portion 11 as shown in FIG.

[0048] The carbon layer 41 is formed over the entire element portion 11 on the end face 11e side of the insulating mask material 37. The carbon layer 41 may completely cover the solid electrolyte layer 39, or may be in contact with the insulating mask material 37, as shown in FIG.

[0049] The method for forming the carbon layer 41 (the method for applying the carbon paste) is not particularly limited to roller transfer, and may be, for example, immersion, but roller transfer is preferable. Also, the application of the carbon paste itself may be omitted.

[0050] FIG. 11 is a plan view schematically showing an example of a process for forming a silver layer on the element portion of an assembly of solid electrolytic capacitor elements.

[0051] Subsequently, silver paste is transferred as cathode paste to each element portion 11 of the solid electrolytic capacitor element assembly 10 by roller transfer, forming a silver layer 43 on each element portion 11 as shown in FIG.

[0052] The silver layer 43 is formed over the entire element portion 11 on the side of the end face 11 e closer to the insulating mask material 37 .

[0053] Furthermore, it is preferable that the silver layer 43 be formed so that the solid electrolyte layer 39 and the carbon layer 41 are not exposed on the outer surface of the element portion 11. That is, it is preferable that the silver layer 43 completely covers the carbon layer 41, as shown in FIG. 11 . If the carbon layer 41 is not formed, it is preferable that the silver layer 43 completely covers the solid electrolyte layer 39. This can further improve the moisture resistance reliability of the solid electrolytic capacitor element. It is also preferable that the silver layer 43 be in contact with the insulating mask material 37.

[0054] Here, the roller transfer device used for roller transfer of the cathode paste and the roller transfer step of the cathode paste will be further described with reference to FIG. 12 .

[0055] FIG. 12 is a schematic diagram of an example of a roller transfer device used for roller transfer of cathode paste.

[0056] 12 includes an unwinding section 210, a vertical conveying type roller transfer section 220A, a preliminary drying section 230, a drying section 240, and a winding section 250, and the assembly 10 of solid electrolytic capacitor elements unwound from the unwinding section 210 is transported through the roller transfer section 220A, the preliminary drying section 230, and the drying section 240 in this order, and then wound up by the winding section 250. The assembly 10 is transported through each section at a predetermined transport speed.

[0057] Unwinding unit 210 unwinds assembly 10 of solid electrolytic capacitor elements wound in a roll around a winding reel. Roller transfer unit 220A transfers cathode paste to element portions 11 of assembly 10 while transporting assembly 10 supplied from unwinding unit 210. Pre-drying unit 230 pre-dries the transferred cathode paste by transporting assembly 10 to which element portions 11 have been transferred. Drying unit 240 heats and dries the pre-dried cathode paste while transporting assembly 10. Winding unit 250 winds assembly 10, on which the cathode paste has been dried, into a roll around a winding reel.

[0058] The roller transfer unit 220A has a plurality of transport rollers 221 that transport the assembly 10 of solid electrolytic capacitor elements on a transport path formed by the assembly 10, a pair of rollers (transfer rollers) 222 between which the element parts 11 of the assembly 10 are transported, and a dispenser 223 and a squeegee 224 provided on each roller 222.

[0059] The pair of rollers 222 are provided on both sides of the assembly 10 of solid electrolytic capacitor elements transported by the transport roller 221. Each roller 222 has a circumferential surface made of metal or rubber, and a groove into which the cathode paste is supplied is formed on the circumferential surface. The depth of the groove can be set appropriately taking into account the desired coating thickness of the cathode paste. Note that the circumferential surface of each roller 222 does not need to have a groove formed thereon, and may have a smooth circumferential surface. The circumferential surfaces of the pair of rollers 222 are configured to press against both main surfaces 11a and 11b of the element portion 11 of the assembly 10, respectively. This pressing contact causes the cathode paste on the circumferential surfaces of the pair of rollers 222 to be transferred onto both main surfaces 11a and 11b of the element portion 11 of the assembly 10.

[0060] Each dispenser 223 supplies an appropriate amount of cathode paste to the corresponding roller 222, and the cathode paste does not drip from the circumferential surface of the roller 222. This makes it possible to minimize the amount of cathode paste consumed.

[0061] Each squeegee 224 is disposed a predetermined distance from the circumferential surface of the corresponding roller 222, and adjusts the amount of cathode paste to an appropriate amount by scraping off the cathode paste adhering to the circumferential surface of the corresponding roller 222. Note that if the cathode paste has a low viscosity, for example, scraping by squeegee 224 may not be necessary.

[0062] Using the roller transfer device 200 shown in FIG. 12, first, carbon paste is transferred to the solid electrolyte layer 39 of the element portion 11 of the assembly 10 shown in FIG. 4, and then the carbon paste is dried to form a carbon layer 41 (see FIG. 10).

[0063] Similarly, using the roller transfer device 200 shown in Figure 12, silver paste is transferred to the carbon layer 41 of the element portion 11 of the assembly 10 shown in Figure 10, and then the silver paste is dried to form a silver layer 43 (see Figure 11).

[0064] More specifically, first, cathode paste is supplied onto a pair of rollers 222 of roller transfer device 200. At this time, while each roller 222 is rotated along the transport direction of assembly 10 of solid electrolytic capacitor elements, cathode paste is supplied onto each roller 222 from each dispenser 223, and the amount of cathode paste is adjusted by each squeegee 224.

[0065] The carbon paste is a conductive paste containing carbon particles as a conductive component and a resin component such as an epoxy resin or a phenolic resin.

[0066] The viscosity and thixotropy of the carbon paste are set taking into consideration the shear rate of roller transfer, etc. Furthermore, since it is used in roller transfer, it is preferable to use a high-boiling point solvent as the organic solvent. By using a high-boiling point solvent, it is possible to impart slow drying properties and prevent drying on the circumferential surface of the roller.

[0067] The silver paste is a conductive paste containing silver particles as a conductive component and a resin component such as an epoxy resin, a phenolic resin, etc. The silver paste may also contain a thermoplastic resin as a resin component.

[0068] The viscosity and thixotropy of the silver paste are set taking into consideration the shear rate of roller transfer, etc. A silver paste that has a low viscosity at high shear rates (20 to 250 (1 / s)) and a high viscosity at low shear rates (0.01 to 0.5 (1 / s)) is preferred. Furthermore, as with the carbon paste, since it is used in roller transfer, it is preferred to use a high-boiling-point solvent as the organic solvent. By using a high-boiling-point solvent, it is possible to impart slow drying properties and prevent drying on the circumferential surface of the roller.

[0069] Next, the assembly 10 of solid electrolytic capacitor elements including the element portions 11 on which the solid electrolyte layer 39 is formed is conveyed between a pair of rollers 222 to which the cathode paste is supplied. At this time, the assembly 10 is conveyed in the extension direction of the holding portion 13 so that only the element portions 11 are sandwiched between the pair of rollers 222, thereby printing the cathode paste continuously on the plurality of element portions 11. Only the region of the element portion 11 on the side of the end face 11e from the insulating mask material 37, on which the carbon layer 41 (or the solid electrolyte layer 39 if no carbon layer 41 is formed) is conveyed between the pair of rollers 222.

[0070] The conveying speed of the assembly 10 is, for example, 20 to 150 mm / s. The rotation speed (rpm) of each roller 222 is calculated from the conveying speed and the roller diameter. The gap (mm) between the pair of rollers 222 is set in consideration of the thickness of the element portion 11 (thickness after the solid electrolyte layer is formed), but is set to be at least larger than the thickness of the anode foil.

[0071] The thickness of the anode foil may be 100 μm or more and 150 μm or less, but is preferably 110 μm or more and 130 μm or less.

[0072] The thickness of the element portion 11 (thickness after the solid electrolyte layer is formed) may be 110 μm or more and 180 μm or less, but is preferably 120 μm or more and 160 μm or less.

[0073] 12, the solid electrolytic capacitor element assembly 10 may be transported between a pair of rollers 222 while being transported in a direction perpendicular to the horizontal direction. This makes it easier to uniform the thickness of the cathode paste on both main surfaces 11a and 11b of the element portion 11. This is because it makes it easier to uniform the amount of cathode paste supplied to the pair of rollers 222.

[0074] FIG. 13 is a schematic diagram of another example of a roller transfer device used for roller transfer of cathode paste.

[0075] 13, the roller transfer device 200 may include a horizontally conveying roller transfer unit 220B instead of the vertically conveying roller transfer unit 220A. Similar to the vertically conveying roller transfer unit 220A, the horizontally conveying roller transfer unit 220B includes, on a conveyance path formed by the aggregate 10 of solid electrolytic capacitor elements, a plurality of conveyance rollers 221 for conveying the aggregate 10, a pair of rollers (transfer rollers) 222 between which the element portions 11 of the aggregate 10 are conveyed, and a dispenser 223 and a squeegee 224 provided on each roller 222.

[0076] However, in the horizontal conveyance type roller transfer unit 220B, the assembly 10 of solid electrolytic capacitor elements is conveyed between a pair of rollers 222 while being conveyed in the horizontal direction. This mode is suitable when a conveyance substrate 15 is used as the holding unit 13. This is because the conveyance substrate 15 is hard and therefore difficult to bend in the vertical direction in the conveyance direction. Furthermore, in the case of horizontal conveyance, if the rigidity of the holding unit 13 is low, the assembly 10 may flutter, but if the conveyance substrate 15 has high rigidity, the assembly 10 can be prevented from fluttering even when conveyed horizontally.

[0077] 14 and 15 are perspective views schematically illustrating the appearance of one side of an element portion of an assembly of solid electrolytic capacitor elements to which a cathode paste has been roller-transferred, respectively.

[0078] The cathode paste on the pair of rollers 222 is then transferred to the pair of main surfaces 11a and 11b of the element portion 11, and the cathode paste transferred to the pair of main surfaces 11a and 11b is connected to the pair of side surfaces 11c and 11d and to one end surface 11e. More specifically, the cathode paste that spills out between each roller 222 and each main surface 11a and 11b wraps around and contacts the side surfaces 11c and 11d and end surface 11e from both main surfaces 11a and 11b, thereby connecting the cathode paste to the side surfaces 11c and 11d and end surface 11e. Therefore, as shown in FIGS. 14 and 15 , the cathode paste layers 50 on both main surfaces 11a and 11b, both side surfaces 11c and 11d, and end surface 11e are seamlessly connected without generating interfaces at their boundaries.

[0079] Fig. 16 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element produced by a method for producing a solid electrolytic capacitor element according to an embodiment of the present invention, and corresponds to the cross-sectional view shown in Fig. 5. Fig. 17 is a cross-sectional view taken along line YY of the solid electrolytic capacitor element shown in Fig. 16.

[0080] As a result of the above, as shown in Figures 16 and 17, a solid electrolytic capacitor element 30 is formed in each element portion 11. Furthermore, the silver layers 43 on each surface of the solid electrolytic capacitor element 30 are connected seamlessly (without interruption) without creating an interface at the boundary between them.

[0081] In each element portion 11, the solid electrolyte layer 39, the carbon layer 41, and the silver layer 43 (or the solid electrolyte layer 39 and the silver layer 43 if the carbon layer 41 is not formed) located closer to the end face 11e than the insulating mask material 37 function as a cathode, and the anode foil 31 on the opposite side functions as an anode. Therefore, a two-terminal solid electrolytic capacitor can be fabricated using each element portion 11.

[0082] For example, a plurality of element portions 11 are stacked, and the anode and cathode are connected to lead frames to form a stacked body.

[0083] Adjacent stacked element units 11 may be bonded to each other with a conductive adhesive, but it is preferable to integrate them by remelting the resin component contained in the silver layer 43 of each element unit 11. In the latter case, it is preferable to use a thermoplastic resin as the resin component contained in the silver layer 43.

[0084] The laminate is then sealed, and the lead frames are formed and cut to form external terminals, thereby completing the manufacture of a two-terminal solid electrolytic capacitor.

[0085] FIG. 18 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor.

[0086] The solid electrolytic capacitor 100 shown in FIG. 18 is a two-terminal solid electrolytic capacitor, and has a structure in which a lead frame 101 is located at the bottom and solid electrolytic capacitor elements 30 are stacked in order on the lead frame 101 .

[0087] Note that FIG. 18 shows only the characteristic parts of the configuration of the solid electrolytic capacitor, and omits details such as the joining of the anode to the outside and resin sealing, but these can be configured in the same way as in a normal solid electrolytic capacitor.

[0088] Furthermore, the lead frame 101 does not have to be arranged in the bottom layer, and may be sandwiched between the cathodes of two solid electrolytic capacitor elements 30. Therefore, the cathodes of a plurality of solid electrolytic capacitor elements 30 may be stacked to form a laminate of a plurality of solid electrolytic capacitor elements 30, the lead frame 101 may be placed on the laminate, and the cathode of another solid electrolytic capacitor element 30 may be stacked on the lead frame 101 to form another laminate of a plurality of solid electrolytic capacitor elements 30, and a laminate in which the lead frame 101 is sandwiched between the cathode portions may be produced, and then heated and pressed.

[0089] The present specification discloses the following:

[0090] <1> A method for manufacturing a solid electrolytic capacitor element, comprising: a step of supplying a cathode paste onto a pair of rollers; a step of transporting an assembly of solid electrolytic capacitor elements, the assembly including an element portion having a pair of main surfaces, a pair of side surfaces, and an end surface, between the pair of rollers onto which the cathode paste has been supplied; and a step of transferring the cathode paste on the pair of rollers to the pair of main surfaces, and connecting the cathode paste transferred to the pair of main surfaces at the pair of side surfaces and the end surfaces.

[0091] <2> The method for manufacturing a solid electrolytic capacitor element according to <1>, wherein the cathode paste is at least one of a treatment liquid containing a solid electrolyte, a treatment liquid containing a precursor of a solid electrolyte, a carbon paste, and a silver paste.

[0092] <3> The method for manufacturing a solid electrolytic capacitor element according to <1> or <2>, wherein the assembly of solid electrolytic capacitor elements includes a conveying substrate made of a metal material or a resin material and arranged parallel to a conveying direction, and the element portion is arranged on one side or both sides of the conveying substrate.

[0093] <4> The method for manufacturing a solid electrolytic capacitor element according to <1> or <2>, wherein the assembly of solid electrolytic capacitor elements includes a bone portion arranged parallel to a conveying direction, and the element portion includes the same material as the bone portion and is arranged on one side or both sides of the bone portion.

[0094] <5> The method for manufacturing a solid electrolytic capacitor element according to any one of <1> to <4>, wherein the aggregate of solid electrolytic capacitor elements is fed between the pair of rollers while being transported in a horizontal direction.

[0095] <6> The method for manufacturing a solid electrolytic capacitor element according to any one of <1> to <4>, wherein the aggregate of solid electrolytic capacitor elements is fed between the pair of rollers while being conveyed in a direction perpendicular to a horizontal direction.

[0096] DESCRIPTION OF SYMBOLS 10 Assembly of solid electrolytic capacitor elements 11 Element portion 11a, 11b Main surface of element portion 11c, 11d Side surface of element portion 11e End surface of element portion 13 Holding portion 15 Transport substrate 17 Rib portion 30 Solid electrolytic capacitor element 31 Anode foil 31a Metal base portion 31b Porous portion 33 Dielectric layer 35, 37 Insulating mask material 39 Solid electrolyte layer 41 Carbon layer 43 Silver layer 50 Cathode paste layer 100 Solid electrolytic capacitor 101 Lead frame 200 Roller transfer device 210 Unwinding portion 220A Vertical conveying type roller transfer portion 220B Horizontal conveying type roller transfer portion 221 Conveying roller 222 Roller (transfer roller) 223 Dispenser 224 Squeegee 230 Pre-drying portion 240 Drying section 250 Winding section

Claims

1. A step of supplying a cathode paste onto a pair of rollers; a step of conveying an assembly of solid electrolytic capacitor elements having an element portion with a pair of main surfaces, a pair of side surfaces, and end surfaces between the pair of rollers onto which the cathode paste has been supplied; and a step of transferring the cathode paste on the pair of rollers onto the pair of main surfaces and connecting the cathode paste transferred onto the pair of main surfaces onto the pair of side surfaces and the end surfaces. A method for manufacturing a solid electrolytic capacitor element comprising these steps.

2. The method for manufacturing a solid electrolytic capacitor element according to claim 1, wherein the cathode paste is at least one of a treatment liquid containing a solid electrolyte, a treatment liquid containing a precursor of a solid electrolyte, a carbon paste, and a silver paste.

3. The assembly of solid electrolytic capacitor elements includes a conveyance base material made of a metal material or a resin material provided parallel to the conveyance direction, and the element portion is provided on one or both sides of the conveyance base material. The method for manufacturing a solid electrolytic capacitor element according to claim 1 or 2.

4. The assembly of solid electrolytic capacitor elements includes a bone portion provided parallel to the conveyance direction, and the element portion contains the same material as the bone portion and is provided on one or both sides of the bone portion. The method for manufacturing a solid electrolytic capacitor element according to claim 1 or 2.

5. The method for manufacturing a solid electrolytic capacitor element according to any one of claims 1 to 4, wherein the assembly of solid electrolytic capacitor elements is supplied between the pair of rollers while being conveyed in the horizontal direction.

6. The method for manufacturing a solid electrolytic capacitor element according to any one of claims 1 to 4, wherein the assembly of solid electrolytic capacitor elements is supplied between the pair of rollers while being conveyed in a direction orthogonal to the horizontal direction.

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