Manufacturing method of solid electrolytic capacitors

Abstract

A method for manufacturing a solid electrolytic capacitor includes: a step of forming a solid electrolyte layer (39) on an anode foil (31) with a dielectric layer (33) in between; a step of forming a solid electrolytic capacitor element (30) by forming a silver layer (43) comprising a thermoplastic resin on the solid electrolyte layer (39); a step of stacking a plurality of solid electrolytic capacitor elements (30) to form a laminate (110); and a step of hot-pressing the laminate (110) to remelt the thermoplastic resin to integrate the plurality of silver layers (43) of the plurality of solid electrolytic capacitor elements (30) into an interface in which no silver layer (43) is formed in the entire region between adjacent solid electrolytic capacitor elements (30).

Description

Technical Field

[0001] This invention relates to a method for manufacturing solid electrolytic capacitors. Background Technology

[0002] Patent Document 1 describes a solid electrolytic capacitor having a structure in which multiple capacitor elements are stacked, at least one of which is configured to be connected to a cathode lead electrode. The solid electrolytic capacitor has a sealing resin that seals the multiple capacitor elements. The solid electrolytic capacitor is characterized in that each capacitor element has a valve-acting metal substrate having a porous layer on its surface, a dielectric layer disposed on the porous layer, a solid electrolyte layer formed on the dielectric layer, and a cathode layer formed on the solid electrolyte layer. Between the stacked capacitor elements, the cathode layers are directly bonded to each other at least a portion of their surfaces. At least a portion of the surface of the cathode layer of the capacitor element configured to be connected to the cathode lead electrode is directly bonded to the cathode lead electrode. An external cathode electrode containing a conductive resin is formed on the surface of the sealing resin. The external cathode electrode is connected to the cathode layer via the cathode lead electrode.

[0003] Patent Document 2 discloses a method for manufacturing a solid electrolytic capacitor, characterized by comprising: a preparation step for preparing an element precursor, the element precursor comprising a valve metal substrate, a dielectric layer formed on the valve metal substrate, a solid electrolyte layer formed on the dielectric layer, and a conductive paste layer formed on the solid electrolyte layer; and a lamination step in which multiple element precursors are laminated together such that the conductive paste layers of adjacent element precursors are connected to each other before the conductive paste of the conductive paste layers constituting them dries, thereby obtaining a laminate.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6776731

[0007] Patent Document 2: Japanese Patent Application Publication No. 2007-194430 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Patent Document 1 describes a method in which the cathode layers are directly bonded to each other on at least a portion of the surface of the cathode layer between stacked capacitor elements.

[0010] Patent document 2 describes a method in which multiple element precursors are stacked before the conductive paste constituting their conductive paste layers are dried, so that the conductive paste layers in adjacent element precursors are integrated with each other through stacking.

[0011] However, in Patent Document 1, the solid electrolyte layer, the carbon layer serving as the cathode layer, and the silver layer are all formed by impregnation with a liquid material such as a polymer solution or paste. As a result, the outer surface of the formed cathode layer is slightly bulging outward. Therefore, it is sometimes impossible to completely and directly bond the cathode layers to each other on the cathode layer surface between stacked capacitor elements.

[0012] Furthermore, in Patent Document 2, the solid electrolyte layer and the carbon layer and silver layer, which are conductive paste layers, are also formed by impregnation with a liquid material, just like in Patent Document 1. Therefore, it is sometimes still impossible to make the conductive paste layers completely integrated with each other on the surface of the conductive paste layer.

[0013] Therefore, in conventional solid electrolytic capacitors, there is room for improvement in terms of more reliably integrating the cathode layers of multiple solid electrolytic capacitor elements with each other over a wide range and more reliably reducing the ESR (equivalent series resistance) in the stack of solid electrolytic capacitor elements.

[0014] This invention was made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a solid electrolytic capacitor that can more reliably reduce ESR.

[0015] Technical solutions for solving the problem

[0016] The method for manufacturing a solid electrolytic capacitor according to the present invention includes: a step of forming a solid electrolyte layer on an anode foil with a dielectric layer in between; a step of forming a solid electrolytic capacitor element by forming a silver layer comprising a thermoplastic resin on the solid electrolyte layer; a step of stacking a plurality of solid electrolytic capacitor elements to form a laminate; and a step of hot-pressing the laminate to remelt the thermoplastic resin to integrate the plurality of silver layers of the plurality of solid electrolytic capacitor elements into an interface in which no silver layer is formed in the entire region between adjacent solid electrolytic capacitor elements.

[0017] Invention Effects

[0018] According to the present invention, a method for manufacturing a solid electrolytic capacitor that can more reliably reduce ESR can be provided. Attached Figure Description

[0019] Figure 1 This is a top view schematically showing an example (elongated structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention.

[0020] Figure 2 This is a top view schematically illustrating an example of a process for masking the formation of an assembly of solid electrolytic capacitor elements.

[0021] Figure 3 This is a top view schematically illustrating an example of a process for performing a mask treatment (polarization treatment) on the element portion of an assembly of solid electrolytic capacitor elements.

[0022] Figure 4 This is a top view schematically illustrating an example of a process for forming a solid electrolyte layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0023] Figure 5 yes Figure 4 The shown component section is a cross-sectional view along line XX.

[0024] Figure 6 It is Figure 5 The polarization section of the component shown is an enlarged cross-sectional view.

[0025] Figure 7 This is a top view schematically illustrating another example (double-opening configuration) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention.

[0026] Figure 8 This is a top view schematically showing another example (strip structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention.

[0027] Figure 9 This is a top view schematically showing another example (double-opening configuration) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention.

[0028] Figure 10 This is a top view schematically illustrating an example of a process for forming a carbon layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0029] Figure 11 This is a top view schematically illustrating an example of a process for forming a silver layer on the element portion of an assembly of solid electrolytic capacitor elements.

[0030] Figure 12 This is a schematic diagram of an example of a roller transfer printing device for printing cathode paste.

[0031] Figure 13This is a schematic diagram of another example of a roller transfer printing device used for printing cathode paste.

[0032] Figure 14 This is a perspective view schematically showing the appearance of one side of the component portion of an assembly of solid electrolytic capacitor components with cathode paste transferred onto it.

[0033] Figure 15 This is a perspective view schematically showing the appearance of the other side of the component portion of an assembly of solid electrolytic capacitor components with cathode paste transferred by roller.

[0034] Figure 16 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor element manufactured by a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention, corresponding to... Figure 5 The sectional view shown.

[0035] Figure 17 This is a cross-sectional view schematically illustrating an example of a process of stacking multiple solid electrolytic capacitor elements to form a laminate.

[0036] Figure 18 This is a cross-sectional view schematically showing an example of a laminate in which multiple silver layers are integrated.

[0037] Figure 19 This is a side view schematically showing an example of a stack in which multiple silver layers are integrated.

[0038] Figure 20 This is an end view of one side of an example of a stack in which multiple silver layers are integrated.

[0039] Figure 21 This is an end view of another example of a stack in which multiple silver layers are integrated.

[0040] Figure 22 This is a front view schematically showing an example of a stack in which multiple silver layers are integrated.

[0041] Figure 23 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor. Detailed Implementation

[0042] The manufacturing method of solid electrolytic capacitors will be described below.

[0043] However, the present invention is not limited to the following structures, and can be appropriately modified and applied without changing the spirit of the invention. Furthermore, combining two or more of the preferred structures described below also constitutes the present invention.

[0044] The attached diagrams are schematic diagrams, and their dimensions, aspect ratios, and scales may sometimes differ from the actual product.

[0045] In this specification, terms indicating relationships between elements (e.g., “parallel,” “perpendicular,” “orthogonal,” etc.) and terms indicating the shape of elements do not necessarily imply a strict manner as described in the text, but also imply a range of substantially equivalent terms, such as a range that includes a degree of difference of a few percent.

[0046] The method for manufacturing a solid electrolytic capacitor according to embodiments of the present invention includes: a step of forming a solid electrolyte layer on an anode foil with a dielectric layer in between; a step of forming a solid electrolytic capacitor element by forming a silver layer comprising a thermoplastic resin on the solid electrolyte layer; a step of stacking a plurality of solid electrolytic capacitor elements to form a laminate; and a step of hot-pressing the laminate to remelt the thermoplastic resin to integrate the plurality of silver layers of the plurality of solid electrolytic capacitor elements into an interface in which no silver layer is formed in the entire region between adjacent solid electrolytic capacitor elements.

[0047] In this manner, a silver layer comprising a thermoplastic resin is formed on a solid electrolyte layer. Multiple solid electrolytic capacitor elements, each possessing such a silver layer, are stacked to form a laminate. The laminate is then hot-pressed to remelt the thermoplastic resin. This allows for more reliable integration of the multiple silver layers into an interface where no silver layer forms in the entire region between adjacent solid electrolytic capacitor elements. Therefore, the laminate, as a solid electrolytic capacitor element, can more reliably achieve low ESR. Furthermore, the moisture resistance reliability of the laminate can be improved.

[0048] Hereinafter, the manufacturing method of the solid electrolytic capacitor according to embodiments of the present invention will be described in more detail with the aid of the accompanying drawings.

[0049] Figure 1 This is a top view schematically showing an example (elongated structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention. Figure 2 This is a top view schematically illustrating an example of a process for masking the formation of an assembly of solid electrolytic capacitor elements. Figure 3 This is a top view schematically illustrating an example of a process for performing a mask treatment (polarization treatment) on the element portion of an assembly of solid electrolytic capacitor elements. Figure 4 This is a top view schematically illustrating an example of a process for forming a solid electrolyte layer in the element portion of an assembly of solid electrolytic capacitor elements. Figure 5 yes Figure 4 The shown component section is a cross-sectional view along line XX. Figure 6 It is Figure 5The polarization section of the component shown is an enlarged cross-sectional view.

[0050] go through Figures 1-4 The process shown is as follows: Figure 5 as well as Figure 6 As shown, a solid electrolyte layer 39 is formed on the anode foil 31 through the dielectric layer 33.

[0051] In addition, in this embodiment, such as Figure 4 As shown, an example of manufacturing a solid electrolytic capacitor using an assembly 10 of solid electrolytic capacitor elements having multiple element sections 11 will be described. However, the solid electrolytic capacitor of the present invention can also be manufactured using individual solid electrolytic capacitor elements.

[0052] Each component 11 has a pair of main surfaces 11a and 11b, a pair of side surfaces 11c and 11d, and an end surface 11e.

[0053] Furthermore, each component part 11 is a flat plate that appears rectangular when viewed from above, such as... Figure 5 as well as Figure 6 As shown, it includes an anode foil 31 with a porous valve-acting metal substrate on its surface, and a dielectric layer 33 disposed on the surface of the anode foil 31 (see reference). Figure 6 ,exist Figure 5 (Not shown in the diagram) Two insulating mask materials 35 and 37, which are annular (extending in a strip-like) insulating members disposed around the anode foil 31 with a dielectric layer 33 between them, and a solid electrolyte layer 39 disposed on the anode foil 31 with a dielectric layer 33 between it and the end face 11e of the insulating mask material 37. In each element section 11, the solid electrolyte layer 39 is opposite to the anode foil 31 with a dielectric layer 33 between it and the element section 11.

[0054] In addition, such as Figure 4 As shown, the assembly 10 of solid electrolytic capacitor elements includes a strip-shaped holding portion 13 that connects multiple element portions 11 at fixed intervals.

[0055] The following is about Figures 1-4 The process shown is explained below.

[0056] First, such as Figure 1 As shown, the anode foil 31 is cut into the shape of a solid electrolytic capacitor element (preferably rectangular) by laser processing or punching, and then welded, for example, to a conveying substrate 15 that serves as a holding part 13 to form an assembly 10 of solid electrolytic capacitor elements.

[0057] In this manner, the assembly 10 of solid electrolytic capacitor elements includes a transport substrate 15 containing a metal or resin material, which is disposed parallel to the transport direction of the assembly 10 during the transfer process of the cathode paste described later. The element portion 11 is disposed only on one side of the transport substrate 15. The side surfaces 11c and 11d of the element portion 11 extend in a direction orthogonal to the transport direction (holding portion 13), and the end face 11e of the element portion 11 extends parallel to the transport direction (holding portion 13).

[0058] The anode foil 31, which forms the component part 11, is made of a valve-acting metal substrate with a porous surface. For example... Figure 6 As shown, the anode foil 31 is a thin film (foil) with a rectangular shape in plan view, having 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.

[0059] In addition, in this specification, "top view" means viewing from the normal direction of the main surface of the anode foil.

[0060] The valve-acting metal matrix is ​​composed of elemental metals such as aluminum, tantalum, niobium, titanium, zirconium, or alloys containing these metals.

[0061] In addition, regarding the valve-acting metal substrate, it is sufficient to consist of a core and a porous part provided on at least one main surface of the core. Valve-acting metal substrates with the surface of the metal foil etched or valve-acting metal substrates with porous micro-powder sintered bodies formed on the surface of the metal foil can be appropriately used.

[0062] Figure 7 This is a top view schematically illustrating another example (double-opening configuration) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention.

[0063] The assembly 10 of solid electrolytic capacitor elements is not particularly limited to Figure 1 The elongated structural type shown is as follows: Figure 7 As shown, it can also be a double-opening structure (fishbone structure). In this case, the element part 11 is provided on both sides of the conveying substrate 15.

[0064] For example, aluminum or stainless steel can be used as the metal material for the conveying substrate 15. For example, fluoropolymer resin, phenolic resin, or glass-epoxy resin composite material can be used as the resin material for the conveying substrate 15.

[0065] In summary, unlike the anode foil 31, the conveying substrate 15 is a highly rigid component, which can also prevent the assembly 10 of solid electrolytic capacitor elements from shaking during the cathode paste transfer process described later.

[0066] Figure 8 This is a top view schematically showing another example (strip structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention. Figure 9 This is a top view schematically showing another example (double-opening configuration) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing solid electrolytic capacitor elements according to an embodiment of the present invention.

[0067] The assembly 10 of solid electrolytic capacitor elements may also be absent. Figure 1 as well as Figure 7 The conveying substrate 15 shown is as follows: Figure 8 as well as Figure 9 As shown, a frame portion 17, arranged parallel to the conveying direction of the conveying assembly 10 in the cathode paste transfer process described later, can also be provided as a holding portion 13. In this case, the element portion 11 contains the same material as the frame portion 17. Specifically, both are made of the same valve-operated metal substrate and are formed by cutting the same anode foil. The element portion 11 can be as follows: Figure 8 As shown, it is only set on one side of the skeleton part 17 (elongated structure type), or it can be like... Figure 9 As shown, it is set on both sides of the skeleton part 17 (double-opening structure (fishbone structure) type).

[0068] Next, as Figure 2 As shown, an insulating mask material 35 is applied to the component section 11 for masking treatment for formation.

[0069] Regarding the insulating mask material 35, it can be formed, for example, by applying a mask material containing an insulating resin composition through methods such as screen printing, roller transfer printing, dispensing, or inkjet printing. Examples of insulating resins include, for instance, polyphenylene sulfone (PPS), polyether sulfone (PES), cyanate ester resins, fluoropolymers (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, etc.), compositions composed of soluble polyimide siloxanes and epoxy resins, polyimide resins, polyamide-imide resins, and their derivatives or precursors.

[0070] In addition, when using the skeleton part 17 instead of the substrate 15, the skeleton part 17 is formed as a whole, and the anode and cathode are polarized separately, so the mask treatment for the formation is not required.

[0071] Next, the assembly 10 of solid electrolytic capacitor elements undergoes a formation process (anodizing). This forms an oxide film, which becomes the dielectric layer, on the surface of the valve-acting metal substrate. For example, the dielectric layer is composed of aluminum oxide. At this time, an oxide film is also formed on a pair of side surfaces 11c and 11d and an end face 11e of the element portion 11, which has been cut by laser processing or punching.

[0072] Alternatively, a chemically formed foil with an aluminum oxide already formed can be used as the valve action metal substrate. In this case, by performing a chemical forming process on the cut valve action metal substrate, an oxide film is also formed on a pair of side surfaces 11c and 11d and an end face 11e of the cut element portion 11.

[0073] Next, as Figure 3 As shown, insulating mask material 37 is applied to the element part 11 to perform a mask treatment (polarization treatment) for polarization of the anode and cathode parts.

[0074] Regarding the insulating mask material 37, it can be formed, for example, by applying a mask material containing an insulating resin composition through methods such as screen printing, roller printing, dispensing, or inkjet printing. Examples of insulating resins include, for instance, polyphenylene sulfone (PPS), polyether sulfone (PES), cyanate ester resins, fluoropolymers (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, etc.), compositions composed of soluble polyimide siloxanes and epoxy resins, polyimide resins, polyamide-imide resins, and their derivatives or precursors.

[0075] Next, as Figure 4 As shown, 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 processing solution containing a solid electrolyte, thereby allowing the processing solution to penetrate into the porous portion of the valve-acting metal substrate. After a given immersion time, the element portion 11 is removed from the processing solution and dried at a given temperature and for a given time. The solid electrolyte layer 39 is formed by repeating the immersion, removal, and drying process a given number of times. Alternatively, the formation of the solid electrolyte layer 39 can also be performed by repeating the following operation a given number of times: immersing the element portion 11 in a processing solution containing a precursor of the solid electrolyte (a monomer that becomes a solid electrolyte through oxidative polymerization), and then immersing it in a processing solution containing an oxidant that causes the precursor of the solid electrolyte to undergo oxidative polymerization.

[0076] The solid electrolyte layer 39 is formed integrally on the element portion 11 on the side closer to the end face 11e than the insulating mask material 37. For example... Figures 4-6 As shown, the solid electrolyte layer 39 can also be connected to the insulating mask material 37.

[0077] A solid electrolyte layer 39 is disposed on the dielectric layer 33. For example... Figure 6 As shown, the solid electrolyte layer 39 is preferably configured to fill a plurality of pores (recesses) in the porous portion 31b of the anode foil 31. However, as long as a portion of the outer surface of the dielectric layer 33 is covered by the solid electrolyte layer 39, there may also be pores (recesses) in the porous portion 31b of the anode foil 31 that are not filled by the solid electrolyte layer 39.

[0078] As a processing liquid containing a solid electrolyte, dispersions of conductive polymers such as polypyrroles, polythiophenes, and polyanilines can be used. Among these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene) known as PEDOT is particularly preferred. Furthermore, the aforementioned conductive polymers may also contain dopants such as polystyrene sulfonic acid (PSS). By attaching the dispersion of the conductive polymer to the outer surface of the dielectric layer and drying it, a conductive polymer film can be formed. Alternatively, as a processing liquid containing a precursor of a solid electrolyte, a liquid containing polymeric monomers such as 3,4-ethylenedioxythiophene can also be used. Dopants such as polystyrene sulfonic acid may also be included in the polymeric monomer. Furthermore, an oxidizing agent may be included in the processing liquid containing the precursor of the solid electrolyte. This processing liquid can be attached to the outer surface of the dielectric layer and a conductive polymer film can be formed by oxidative polymerization (chemical polymerization). This conductive polymer film becomes the solid electrolyte layer 39.

[0079] Figure 10 This is a top view schematically illustrating an example of a process for forming a carbon layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0080] Next, carbon paste, used as cathode paste, is transferred to each element section 11 of the assembly 10 of solid electrolytic capacitor elements using a roller transfer printing method, such as... Figure 10 As shown, a carbon layer 41 is formed in each component part 11.

[0081] The carbon layer 41 is formed integrally on the element portion 11 on the side closer to the end face 11e than the insulating mask material 37. For example... Figure 10 As shown, the carbon layer 41 can completely cover the solid electrolyte layer 39, or it can be connected to the insulating mask material 37.

[0082] Furthermore, the method for forming the carbon layer 41 (the method for applying the carbon paste) is not particularly limited to roller transfer printing; for example, it can also be dip-coating, but roller transfer printing or screen printing is preferred. This allows for a more easier and more reliable formation of a silver layer 43 with a flat outer surface on the carbon layer 41. Additionally, the application of the carbon paste itself can be omitted.

[0083] Figure 11 This is a top view schematically illustrating an example of a process for forming a silver layer on the element portion of an assembly of solid electrolytic capacitor elements.

[0084] Next, a silver layer 43 comprising thermoplastic resin is formed on the solid electrolyte layer 39, and solid electrolytic capacitor elements 30 are formed on each element portion 11. More specifically, silver paste, as cathode paste, is transferred to each element portion 11 of the solid electrolytic capacitor element assembly 10 by roller transfer printing, as shown below. Figure 11 As shown, a silver layer 43 is formed in each element portion 11. The outer surface of the silver layer 43 can be flat, thereby enabling more reliable integration of multiple silver layers into an interface where no silver layer is formed in the entire region between adjacent solid electrolytic capacitor elements.

[0085] In this specification, the term "silver layer with a flat outer surface" means that the entire area of ​​a pair of main faces of the silver layer opposite each other in the stacking direction of the solid electrolytic capacitor element is flat and parallel to each other. More specifically, if the thickness of the cathode portion of the solid electrolytic capacitor element is measured at multiple locations, and its standard deviation is 30 μm or less, preferably 20 μm or less, the outer surface of the silver layer can also be described as flat. Here, "multiple locations" can refer to the five locations on the top, middle, bottom, left, and right sides of the cathode portion of the solid electrolytic capacitor element.

[0086] Furthermore, in this invention, a "silver layer with a flat outer surface" means that at least its outer surface is in a dry state. That is, a silver layer with a flat outer surface is typically a state where the silver paste supplied to the solid electrolyte layer has been dried or temporarily dried. Therefore, in this embodiment, the assembly 10 of solid electrolytic capacitor elements and the solid electrolytic capacitor element 30 can be easily processed in subsequent processes.

[0087] The silver layer 43 is formed on the component portion 11 on the side closer to the end face 11e than the insulating mask material 37.

[0088] Furthermore, the silver layer 43 is preferably formed such that the solid electrolyte layer 39 and the carbon layer 41 are not exposed on the outer surface of the solid electrolytic capacitor element 30. That is, as Figure 11 As shown, the silver layer 43 preferably completely covers the carbon layer 41. In the absence of a carbon layer 41, the silver layer 43 preferably completely covers the solid electrolyte layer 39. This further improves the moisture resistance reliability of the laminate of the solid electrolytic capacitor element 30. Furthermore, the silver layer 43 is preferably in contact with the insulating mask material 37.

[0089] Furthermore, the method for forming the silver layer 43 (the method for applying the silver paste) is not particularly limited to roller printing, but roller printing or screen printing is preferred. These methods are suitable for forming a silver layer 43 with a flat outer surface.

[0090] Here, use Figure 12 The roller transfer printing device for cathode paste and the roller transfer printing process for cathode paste are further explained.

[0091] Figure 12This is a schematic diagram of an example of a roller transfer printing device for printing cathode paste.

[0092] Figure 12 The roller transfer printing apparatus 200 shown includes an unwinding section 210, a vertically conveying roller transfer printing section 220A, a temporary drying section 230, a drying section 240, and a winding section 250. An assembly 10 of solid electrolytic capacitor elements, unwound from the unwinding section 210, is conveyed in the order of roller transfer printing section 220A, temporary drying section 230, and drying section 240, and then wound in the winding section 250. The assembly 10 is conveyed in each section at a given conveying speed.

[0093] The unwinding section 210 unwinds the assembly 10 of solid electrolytic capacitor elements, which is wound in a cylindrical shape on the unwinding reel. The roller transfer section 220A transfers cathode paste onto the element portion 11 of the assembly 10 while conveying the assembly 10 supplied from the unwinding section 210. The temporary drying section 230 temporarily dries the transferred cathode paste by conveying the assembly 10 with the cathode paste transferred to the element portion 11. The drying section 240 heats and dries the temporarily dried cathode paste while conveying the assembly 10. The winding section 250 winds the dried cathode paste assembly 10 into a cylindrical shape onto a winding reel.

[0094] The roller transfer section 220A has multiple conveying rollers 221 for conveying the assembly 10 of the solid electrolytic capacitor elements, a pair of rollers (transfer rollers) 222 for conveying the element parts 11 of the assembly 10 therebetween, and a distributor 223 and a scraper 224 provided on each roller 222.

[0095] A pair of rollers 222 are disposed on both sides of the assembly 10 of solid electrolytic capacitor elements conveyed by the conveying rollers 221. Each roller 222 has a circumferential surface made of metal or rubber, on which grooves for supplying cathode paste are formed. The depth of the grooves can be appropriately set considering the desired coating thickness of the cathode paste. Alternatively, grooves may not be formed on the circumferential surface of each roller 222, or the circumferential surface may be smooth. Furthermore, each circumferential surface of the pair of rollers 222 comes into contact with the two main surfaces 11a and 11b of the element portion 11 within the assembly 10. Through this contact, the cathode paste on the circumferential surfaces of the pair of rollers 222 is transferred onto the two main surfaces 11a and 11b of the element portion 11 of the assembly 10.

[0096] Each distributor 223 supplies an appropriate amount of cathode paste to the corresponding roller 222, preventing the cathode paste from dripping off the circumferential surface of the roller 222. Therefore, the consumption of cathode paste can be set to the required minimum.

[0097] Each scraper 224 is positioned a given distance apart from the circumferential surface of its corresponding roller 222, and the amount of cathode paste adhering to the circumferential surface of the corresponding roller 222 is adjusted to an appropriate level by scraping it off. Alternatively, for example, if the cathode paste has a low viscosity, scraping based on the scraper 224 may not be necessary.

[0098] use Figure 12 The roller transfer device 200 shown first... Figure 4 The solid electrolyte layer 39 of the component section 11 of the assembly 10 shown is transferred with carbon paste, and then the carbon paste is dried to form a carbon layer 41 (see reference). Figure 10 ).

[0099] Similarly, using Figure 12 The roller transfer device 200 shown is directed to... Figure 10 The carbon layer 41 of the component part 11 of the assembly 10 shown is transferred with silver paste, and then the silver paste is dried to form a silver layer 43 (see reference). Figure 11 ).

[0100] In this way, the process of forming the silver layer 43 preferably includes a process of drying the silver paste. Here, "drying the silver paste" means drying the silver paste to a state where at least the outer surface of the silver layer 43 is dry, as described above, including the case of temporarily drying the silver paste.

[0101] Furthermore, the drying temperature t of the silver paste can be set appropriately, but it is preferably 130°C or higher and 180°C or lower, more preferably 140°C or higher and 160°C or lower. In addition, the drying time of the silver paste can also be set appropriately, but it is preferably 20 minutes or higher and 90 minutes or lower, more preferably 30 minutes or higher and 60 minutes or lower.

[0102] More specifically, firstly, cathode paste is supplied to a pair of rollers 222 of the roller transfer device 200. At this time, while rotating each roller 222 along the conveying direction of the assembly 10 of solid electrolytic capacitor elements, cathode paste is supplied to each roller 222 from each distributor 223, and the amount of cathode paste is adjusted by each scraper 224.

[0103] Carbon paste is a conductive paste containing carbon particles as conductive components and resin components such as epoxy resin and phenolic resin.

[0104] The viscosity and thixotropic properties of the carbon paste are set considering factors such as the shear speed of roller transfer printing. Furthermore, since it is used in roller transfer printing, a high-boiling-point solvent is preferred as the organic solvent. By using a high-boiling-point solvent, it is possible to achieve delayed drying and prevent drying at the circumferential surface of the roller.

[0105] Silver paste is a conductive paste containing silver particles as conductive components and resin components.

[0106] Furthermore, the silver paste contains at least a thermoplastic resin as a resin component. This allows for the formation of a silver layer comprising a thermoplastic resin.

[0107] Saturated copolyester resins are preferred as the thermoplastic resin. Furthermore, regarding this thermoplastic resin, it is preferable that the glass transition temperature is below 0°C, and the weight loss rate when heated from 25°C to 200°C by simultaneous thermogravimetry-differential thermal analysis (TG-DTA) is below 0.1%. Such a thermoplastic resin is suitable for integrating multiple silver layers of multiple solid electrolytic capacitor elements.

[0108] The glass transition temperature of the above-mentioned thermoplastic resin is preferably below 25°C, and more preferably below 0°C.

[0109] In addition, the aforementioned thermoplastic resins can also be amorphous without a glass transition point.

[0110] The weight loss rate of the above-mentioned thermoplastic resin when heated from 25°C to 200°C by TG-DTA is preferably 0.1% or less, more preferably 0.05% or less.

[0111] The content of thermoplastic resin in the total amount of silver paste can be set to, for example, 5% by mass or more and 25% by mass or less.

[0112] The viscosity and thixotropic properties of the silver paste are set considering factors such as the shear speed of roller transfer printing. A silver paste that exhibits lower viscosity at high shear speeds (20–250 lm / s) and higher viscosity at low shear speeds (0.01–0.5 lm / s) is preferred. Furthermore, similar to carbon paste, since it is used in roller transfer printing, a high-boiling-point solvent is preferred as the organic solvent. By using a high-boiling-point solvent, it can be made to have delayed drying properties, thus preventing drying at the circumferential surface of the roller.

[0113] Next, an assembly 10 of solid electrolytic capacitor elements, including element portions 11 with a solid electrolyte layer 39, is conveyed between a pair of rollers 222 on which cathode paste has been supplied. At this time, the assembly 10 is conveyed in the extending direction of the holding portion 13 such that only the element portions 11 are sandwiched between the rollers 222, thereby continuously printing cathode paste onto multiple element portions 11. Between the rollers 222, only the region of the element portion 11 on the side closer to the end face 11e than the insulating mask material 37, where a carbon layer 41 (or solid electrolyte layer 39 if no carbon layer 41 is formed) is conveyed.

[0114] The conveying speed of the assembly 10 is, for example, 20 to 150 mm / s. The rotational speed (rpm) of each roller 222 can be calculated based on the conveying speed and the roller diameter. The gap (mm) between a pair of rollers 222 is set taking into account the thickness of the element part 11 (the thickness after the solid electrolyte layer is formed), but it is set to be at least larger than the thickness of the anode foil.

[0115] In addition, the thickness of the anode foil can be 100 μm or more and 150 μm or less, but preferably 110 μm or more and 130 μm or less.

[0116] Furthermore, the thickness of the element portion 11 (the thickness after the solid electrolyte layer is formed) may be 110 μm or more and 180 μm or less, but it is preferably 120 μm or more and 160 μm or less.

[0117] The assembly 10 of solid electrolytic capacitor elements can also be as follows Figure 12 As shown, the conveying is carried out in a direction orthogonal to the horizontal direction and between a pair of rollers 222.

[0118] Figure 13 This is a schematic diagram of another example of a roller transfer printing device used for printing cathode paste.

[0119] like Figure 13 As shown, the roller transfer device 200 can also replace the vertical conveying roller transfer section 220A with a horizontal conveying roller transfer section 220B. Like the vertical conveying roller transfer section 220A, the horizontal conveying roller transfer section 220B has multiple conveying rollers 221 for conveying the assembly 10, a pair of rollers (transfer rollers) 222 for conveying the element portions 11 of the assembly 10, and distributors 223 and scrapers 224 provided on each roller 222 along the conveying path formed by the assembly 10 of solid electrolytic capacitor elements.

[0120] However, in the horizontal conveying roller transfer section 220B, the assembly 10 of solid electrolytic capacitor elements is conveyed in the horizontal direction and between a pair of rollers 222.

[0121] Figure 14 This is a perspective view schematically showing the appearance of one side of the component portion of an assembly of solid electrolytic capacitor components with cathode paste transferred onto it. Figure 15 This is a perspective view schematically showing the appearance of the other side of the component portion of an assembly of solid electrolytic capacitor components with cathode paste transferred by roller.

[0122] Then, the cathode paste on a pair of rollers 222 is transferred to a pair of main surfaces 11a and 11b of the element section 11, and the cathode paste transferred to the pair of main surfaces 11a and 11b is connected to a pair of side surfaces 11c and 11d and an end surface 11e. More specifically, the cathode paste overflowing from between each roller 222 and each main surface 11a, 11b wraps around the two main surfaces 11a and 11b to the side surfaces 11c and 11d and the end surface 11e and contacts them, thereby connecting the cathode paste to the side surfaces 11c and 11d and the end surface 11e. Therefore, as Figure 14 as well as Figure 15 As shown, the cathode paste layer 50 on the two main surfaces 11a and 11b, the two side surfaces 11c and 11d, and the end face 11e becomes seamlessly (uninterruptedly) connected without creating an interface at their boundaries.

[0123] Figure 16 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor element manufactured by a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention, corresponding to... Figure 5 The sectional view shown.

[0124] The above results are as follows: Figure 16 As shown, solid electrolytic capacitor elements 30 are formed in each element section 11. Furthermore, the silver layers 43 in each surface of the solid electrolytic capacitor element 30 are seamlessly (uninterruptedly) connected without creating interfaces at their boundaries.

[0125] Furthermore, in each element section 11, the solid electrolyte layer 39, carbon layer 41, and silver layer 43 (solid electrolyte layer 39 and silver layer 43 if carbon layer 41 is not formed) on the side closer to the end face 11e of the insulating mask material 37 function as cathodes, while the anode foil 31 on the opposite side functions as an anode. Therefore, a two-terminal solid electrolytic capacitor can be manufactured simply by using each element section 11.

[0126] Figure 17 This is a cross-sectional view schematically illustrating an example of a process of stacking multiple solid electrolytic capacitor elements to form a laminate.

[0127] Then, by stacking multiple aggregates 10, thus as Figure 17 As shown, a plurality of solid electrolytic capacitor elements 30 (element portions 11) are stacked to form a laminate 110. In this stage, the plurality of solid electrolytic capacitor elements 30 simply overlap each other, and an interface 43a exists between their silver layers 43 throughout the entire area. At this time, it is not necessary to provide a conductive adhesive between adjacent solid electrolytic capacitor elements 30.

[0128] Figure 18This is a cross-sectional view schematically showing an example of a laminate in which multiple silver layers are integrated.

[0129] Next, the laminate 110 is hot-pressed together, causing the thermoplastic resin in each silver layer 43 to remelt. The result is, as... Figure 18 As shown, the multiple silver layers 43 of the multiple solid electrolytic capacitor elements 30 are more reliably integrated, and the interface of the silver layers 43 disappears throughout the entire region between adjacent solid electrolytic capacitor elements 30. This allows for a more reliable reduction in the ESR of the laminate 110 and improves the moisture resistance reliability of the laminate 110. Furthermore, since no conductive adhesive is required, costs can be reduced and the thickness (height) of the laminate 110 in the lamination direction can be reduced.

[0130] The temperature T during hot pressing of the laminate 110 can be appropriately set, but it is preferably higher than the drying temperature t of the silver paste described above. Specifically, the difference (Tt) between temperature T and drying temperature t is preferably 50°C or more and 150°C or less, more preferably 80°C or more and 100°C or less.

[0131] The temperature T during hot pressing of the laminate 110 is preferably 150°C or higher and 250°C or lower, more preferably 180°C or higher and 230°C or lower. Furthermore, the hot pressing time of the laminate 110 can be appropriately set, but is preferably 10 seconds or higher and 90 seconds or lower, more preferably 20 seconds or higher and 60 seconds or lower. Moreover, the pressure during hot pressing of the laminate 110 can also be appropriately set, but is preferably 5N or higher and 50N or lower for each laminate, more preferably 10N or higher and 30N or lower.

[0132] Figure 19 This is a side view schematically showing an example of a stack in which multiple silver layers are integrated. Figure 20 This is an end view of one side of an example of a stack in which multiple silver layers are integrated. Figure 21 This is an end view of another example of a stack in which multiple silver layers are integrated. Figure 22 This is a front view schematically showing an example of a stack in which multiple silver layers are integrated.

[0133] like Figures 19-22As shown, the laminated body 110 after heat pressing includes a capacitor forming portion 111 with a cuboid shape. The capacitor forming portion 111 corresponds to the capacitor portion in a solid electrolytic capacitor excluding the external terminals, sealing portion, and electrode lead-out portion. It has a first main surface 111a and a second main surface 111b facing each other in the stacking direction (height direction) T of the solid electrolytic capacitor element 30, a first side surface 111c and a second side surface 111d facing each other in the width direction W, and a first end surface 111e and a second end surface 111f facing each other in the length direction L.

[0134] Moreover, such as Figures 19-22 As shown, the silver layer 43 on all six sides of the preferred capacitor forming portion 111 is integrated. This further improves the moisture resistance reliability of the laminate 110.

[0135] More in detail, such as Figure 19 As shown, in the first side surface 111c and the second side surface 111d, the cathode of the laminate 110 (capacitor forming portion 111) is entirely covered by a silver layer 43, while the solid electrolyte layer 39 and the carbon layer 41 are not exposed. The silver layer 43 has irregularities that can identify each solid electrolytic capacitor element 30, but the silver layer portions between adjacent solid electrolytic capacitor elements 30 are connected by surfaces. The anode foil 31 is exposed on the anode side of the laminate 110, closer to the insulating mask material 37.

[0136] like Figure 20 As shown, in the first end face 111e, the cathode of the laminate 110 (capacitor forming part 111) is entirely covered by the silver layer 43, and the solid electrolyte layer 39 and the carbon layer 41 are not exposed. The silver layer 43 has unevenness that can identify each solid electrolytic capacitor element 30, but the silver layer portion between adjacent solid electrolytic capacitor elements 30 is connected by a surface.

[0137] like Figure 21 As shown, in the second end face 111f, the cathode of the laminate 110 (capacitor forming portion 111) is entirely covered by the silver layer 43, while the solid electrolyte layer 39 and the carbon layer 41 are not exposed. The silver layer 43 has irregularities that can identify each solid electrolytic capacitor element 30, but the silver layer portions between adjacent solid electrolytic capacitor elements 30 are connected by surfaces. On the other hand, the anode foil 31 and the insulating mask material 37 are exposed and not covered by the silver layer 43.

[0138] like Figure 22 As shown, in the first main surface 111a and the second main surface 111b, the cathode of the laminate 110 (capacitor forming part 111) is entirely covered by the silver layer 43, and the solid electrolyte layer 39 and the carbon layer 41 are not exposed. The anode foil 31 is exposed on the anode side of the laminate 110, closer to the insulating mask material 37.

[0139] Then, the anode and cathode of the laminate 110 are connected to the lead frame, respectively.

[0140] Then, the laminate 110 is sealed, and the lead frame is shaped and cut to form the external terminals.

[0141] The above results demonstrate that a solid electrolytic capacitor can be manufactured. This solid electrolytic capacitor is a two-terminal type.

[0142] Figure 23 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor.

[0143] Figure 23 The solid electrolytic capacitor 100 shown is a two-terminal solid electrolytic capacitor with the following structure: the lead frame 101 is located at the bottom, and solid electrolytic capacitor elements 30 are stacked on the lead frame 101 in sequence.

[0144] In addition, Figure 23 Only the characteristic parts of the structure of a solid electrolytic capacitor are shown. Details such as the bonding between the anode and the outside, and the resin sealing are omitted, but these are the methods that can be used in a typical solid electrolytic capacitor.

[0145] Furthermore, the lead frame 101 may not be positioned at the bottom layer and can be sandwiched between the cathodes of two solid electrolytic capacitor elements 30. Therefore, it is also possible to stack multiple solid electrolytic capacitor elements 30 by stacking the cathodes of multiple solid electrolytic capacitor elements 30, place the lead frame 101 on the stack, and then stack other solid electrolytic capacitor elements 30 cathodes on the lead frame 101 to create other stacks of multiple solid electrolytic capacitor elements 30, thereby creating a stack in which the lead frame 101 is sandwiched between the cathodes, and then heating and pressurizing it.

[0146] The following information is disclosed in this specification.

[0147] <1>

[0148] A method for manufacturing a solid electrolytic capacitor, comprising:

[0149] The process of forming a solid electrolyte layer on the anode foil through a dielectric layer;

[0150] The process of forming a solid electrolytic capacitor element by forming a silver layer containing thermoplastic resin on the solid electrolyte layer;

[0151] The process of stacking multiple solid electrolytic capacitor elements to form a laminate; and

[0152] The process of hot-pressing the laminate to remelt the thermoplastic resin, thereby integrating the multiple silver layers of the plurality of solid electrolytic capacitor elements into an interface in which no silver layer is formed in the entire region between adjacent solid electrolytic capacitor elements.

[0153] <2>

[0154] According to the manufacturing method of solid electrolytic capacitors described in <1>, wherein,

[0155] It also includes the step of forming a carbon layer between the solid electrolyte layer and the silver layer.

[0156] The silver layer is formed as the solid electrolyte layer, and the carbon layer is not exposed on the outer surface of the solid electrolytic capacitor element.

[0157] <3>

[0158] According to the manufacturing method of solid electrolytic capacitors described in <1> or <2>, wherein,

[0159] The laminate includes a capacitor-forming portion having a cuboid shape.

[0160] The silver layer on all six sides of the capacitor forming part is integrated.

[0161] <4>

[0162] According to any one of <1> to <3>, the method for manufacturing a solid electrolytic capacitor, wherein,

[0163] The thermoplastic resin comprises a saturated copolyester resin.

[0164] <5>

[0165] According to any one of <1> to <4>, the method for manufacturing a solid electrolytic capacitor, wherein,

[0166] Regarding the thermoplastic resin, the glass transition temperature is below 0°C, and the weight loss rate when heated from 25°C to 200°C is below 0.1%, as determined by thermogravimetric differential calorimetry.

[0167] <6>

[0168] According to any one of <1> to <5>, the method for manufacturing a solid electrolytic capacitor, wherein,

[0169] The process of forming the silver layer includes the process of applying a silver paste containing the thermoplastic resin onto the solid electrolyte layer.

[0170] <7>

[0171] According to the manufacturing method of solid electrolytic capacitors described in <6>, in which,

[0172] The process of forming the silver layer includes a process of drying the silver paste.

[0173] The temperature during hot pressing of the laminate is higher than the drying temperature of the silver paste.

[0174] <8>

[0175] According to the manufacturing method of solid electrolytic capacitors described in <6> or <7>, wherein,

[0176] The silver paste is applied to the solid electrolyte layer by roller transfer or screen printing.

[0177] Explanation of reference numerals in the attached figures

[0178] 10: An assembly of solid electrolytic capacitor elements;

[0179] 11: Components Section;

[0180] 11a, 11b: Main surfaces of the component section;

[0181] 11c, 11d: Side views of the component section;

[0182] 11e: End face of the component section;

[0183] 13: Maintaining section;

[0184] 15: Transporting substrate;

[0185] 17: Skeletal part;

[0186] 30: Solid electrolytic capacitor elements;

[0187] 31: Anode foil;

[0188] 31a: Metal matrix portion;

[0189] 31b: Porous portion;

[0190] 33: Dielectric layer;

[0191] 35, 37: Insulating mask material;

[0192] 39: Solid electrolyte layer;

[0193] 41: Carbon layer;

[0194] 43: Silver layer;

[0195] 43a: The interface of the silver layer;

[0196] 50: Cathode paste layer;

[0197] 100: Solid electrolytic capacitor;

[0198] 101: Lead frame;

[0199] 110: Layered body;

[0200] 111: Capacitor forming section;

[0201] 111a: First main face;

[0202] 111b: Second main face;

[0203] 111c: First side view;

[0204] 111d: Second side view;

[0205] 111e: First end face;

[0206] 111f: Second end face;

[0207] 200: Roller transfer printing device;

[0208] 210: Open Book Section;

[0209] 220A: Vertical conveyance roller transfer section;

[0210] 220B: Horizontal conveyor roller transfer printing section;

[0211] 221: Conveying roller;

[0212] 222: Roller (transfer roller);

[0213] 223: Distributor;

[0214] 224: Scraper;

[0215] 230: Temporary drying section;

[0216] 240: Drying section;

[0217] 250: Winding section.

Claims

1. A method for manufacturing a solid electrolytic capacitor, comprising: The process of forming a solid electrolyte layer on the anode foil through a dielectric layer; The process of forming a solid electrolytic capacitor element by forming a silver layer containing thermoplastic resin on the solid electrolyte layer; The process of stacking multiple solid electrolytic capacitor elements to form a laminate; as well as The process of hot-pressing the laminate to remelt the thermoplastic resin, thereby integrating the multiple silver layers of the plurality of solid electrolytic capacitor elements into an interface in which no silver layer is formed in the entire region between adjacent solid electrolytic capacitor elements.

2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein, It also includes the step of forming a carbon layer between the solid electrolyte layer and the silver layer. The silver layer is formed as the solid electrolyte layer, and the carbon layer is not exposed on the outer surface of the solid electrolytic capacitor element.

3. The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, wherein, The laminate includes a capacitor-forming portion having a cuboid shape. The silver layer on all six sides of the capacitor forming part is integrated.

4. A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein, The thermoplastic resin comprises a saturated copolyester resin.

5. A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 4, wherein, Regarding the thermoplastic resin, the glass transition temperature is below 0°C, and the weight loss rate when heated from 25°C to 200°C is below 0.1%, as determined by thermogravimetric differential calorimetry.

6. A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 5, wherein, The process of forming the silver layer includes the process of applying a silver paste containing the thermoplastic resin onto the solid electrolyte layer.

7. The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein, The process of forming the silver layer includes a process of drying the silver paste. The temperature during hot pressing of the laminate is higher than the drying temperature of the silver paste.

8. The method for manufacturing a solid electrolytic capacitor according to claim 6 or 7, wherein, The silver paste is applied to the solid electrolyte layer by roller transfer or screen printing.

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