Conductive paste and method for manufacturing solid electrolytic capacitor element

Abstract

A conductive paste comprising a metal powder, a thermoplastic resin, and a solvent, has a shear viscosity of 0.05 to 1 s ‑1 a shear viscosity of 0.4 to 35 Pa-s at a shear rate of 20 to 200 s ‑1 a shear viscosity of 0.2 to 1.5 Pa-s at a shear rate of 0.05 s ‑1 a shear viscosity of 0.2 to 1.5 Pa-s at a shear rate of 0.05 s ‑1 a shear viscosity of 0.2 to 1.5 Pa-s at a shear rate of 0.05 s

Description

Technical Field

[0001] This invention relates to a conductive paste and a method for manufacturing solid electrolytic capacitor elements. Background Technology

[0002] Patent document 1 describes a conductive paste comprising particles with an average particle size of 4–10 μm and a specific surface area of ​​1.5–3.0 m². 2 / g, aspect ratio 40–150, apparent density 0.4–1.0 g / cm³ 3 Silver particle aggregate A, comprising 30–60% by weight, has an average particle size of 2–5 μm and a specific surface area of ​​1.0–1.5 m². 2 / g, aspect ratio less than 50, apparent density 2.0~3.5g / cm³ 3 The conductive paste is made by mixing silver particle aggregate B to form an aggregate of 100% by weight of flake-shaped silver particles, resin, and solvent. The solid content of the conductive paste is 40-55% by weight, the viscosity is 2.0-6.0 dPa·s, and the thixotropic value is 1.5-1.8.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6103404 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Patent document 1 describes the following: In a method of applying conductive paste by impregnation, by having appropriate viscosity and high thixotropy, the paste at the end of the element is difficult to flow, and a conductive coating film with a fixed film thickness at the end and the plane (side) portion, having coating strength, low resistivity, and stable conductivity can be formed.

[0008] However, Patent Document 1 does not disclose a conductive paste suitable for roller transfer printing.

[0009] The present invention was made to solve the above-mentioned problems, and its object is to provide a conductive paste suitable for roller transfer printing and a method for manufacturing a solid electrolytic capacitor element using the conductive paste.

[0010] Methods for solving problems

[0011] The conductive paste of the present invention comprises metal powder, thermoplastic resin, and solvent, and is applied at a shear rate of 0.05 to 1 s. -1 At this point, the shear viscosity is 0.4–35 Pa·s, and the shear rate is 20–200 s⁻¹. -1At this point, the shear viscosity is 0.2–1.5 Pa·s, and the shear rate is 0.05 s⁻¹. -1 Shear viscosity and shear rate 1s -1 The ratio of shear viscosity to thixotropic value is 5 to 20.

[0012] The manufacturing method of the solid electrolytic capacitor element of the present invention includes the following steps: supplying the conductive paste of the present invention to a pair of rollers; transferring an assembly of solid electrolytic capacitor elements having element portions to the pair of rollers on which the conductive paste has been supplied; and transferring the conductive paste on the pair of rollers to the element portions.

[0013] Invention Effects

[0014] According to the present invention, a conductive paste suitable for roller transfer printing and a method for manufacturing a solid electrolytic capacitor element using the conductive paste can be provided. Attached Figure Description

[0015] Figure 1 This is a top view schematically illustrating an example (elongated structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention.

[0016] Figure 2 This is a top view schematically illustrating an example of a process for masking the element portion of an assembly of solid electrolytic capacitor elements.

[0017] Figure 3 This is a top view schematically illustrating an example of a process for performing a polarization masking treatment (polarization treatment) on the element portion of an assembly of solid electrolytic capacitor elements.

[0018] Figure 4 This is a top view schematically illustrating an example of the process of forming a solid electrolyte layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0019] Figure 5 yes Figure 4 The shown component section is a cross-sectional view along line XX.

[0020] Figure 6 It is Figure 5 The enlarged cross-sectional view of the polarization section of the element shown.

[0021] Figure 7 This is a top view schematically illustrating another example (double-opening 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.

[0022] Figure 8This is a top view schematically showing another example (elongated 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.

[0023] Figure 9 This is a top view schematically showing another example (double-opening 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.

[0024] Figure 10 This is a top view schematically illustrating an example of the process of forming a carbon layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0025] Figure 11 This is a top view schematically illustrating an example of the process of forming a conductive layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0026] Figure 12 This is a schematic diagram of an example of a roller transfer device used for roller transfer printing of conductive paste.

[0027] Figure 13 This is a schematic diagram of another example of a roller transfer device used for roller transfer printing of conductive paste.

[0028] 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 conductive paste transferred onto it.

[0029] 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 conductive paste transferred onto it.

[0030] Figure 16 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor element manufactured by the manufacturing method of the solid electrolytic capacitor element according to an embodiment of the present invention, corresponding to... Figure 5 The sectional view shown.

[0031] Figure 17 yes Figure 16 The solid electrolytic capacitor element shown is a cross-sectional view along the YY line.

[0032] Figure 18 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor.

[0033] Figure 19 This is a graph showing the dependence of the shear viscosity of the conductive pastes of Examples 2, 3 and Comparative Example 2 on shear rate. Detailed Implementation

[0034] The following describes the manufacturing method of the conductive paste and solid electrolytic capacitor element of the present invention.

[0035] However, the present invention is not limited to the following structures, and can be applied with appropriate modifications without changing the spirit of the invention. Furthermore, structures obtained by combining two or more of the preferred structures described below are also part of the present invention.

[0036] The following diagram is a schematic diagram, and its dimensions, aspect ratio, and scale may sometimes differ from the actual product.

[0037] In this specification, terms indicating the correlation between elements (e.g., "parallel", "perpendicular", "orthogonal", etc.) and terms indicating the shape of elements refer not only to the form in a strictly literal sense, but also to substantially equivalent ranges, such as ranges including a few percent of differences.

[0038] In this specification, the numerical range represented by the lower limit and the upper limit, i.e., "lower limit to upper limit", includes both the lower limit and the upper limit. For example, the range represented by "1 to 2" refers to 1 and above and 2 and below, including 1 and 2. In this specification, the upper and lower limits can also be set as any combination of ranges.

[0039] (Conductive paste)

[0040] The conductive paste involved in the embodiments of the present invention includes metal powder, thermoplastic resin, and solvent, and is applied at a shear rate of 0.05 to 1 s. -1 At this point, the shear viscosity is 0.4–35 Pa·s, and the shear rate is 20–200 s⁻¹. -1 At this point, the shear viscosity is 0.2–1.5 Pa·s, and the shear rate is 0.05 s⁻¹. -1 Shear viscosity and shear rate 1s -1 The ratio of shear viscosity to thixotropic value is 5 to 20.

[0041] The metal powder used as the conductive paste of the present invention can be a metal powder comprising silver, copper, nickel, or an alloy of at least two of these metals, or a silver-coated powder on which silver is coated by electroless silver plating or the like. Among these, silver powder is preferred.

[0042] The conductive paste described in this embodiment is suitable for roller transfer printing. In roller transfer printing, the shear stress generated by the shear speed of the roller is applied to the conductive paste, resulting in a low viscosity (shear viscosity), which is quite different from the impregnation method. Furthermore, after roller transfer printing, the shear stress almost disappears, thus increasing the viscosity (shear viscosity) of the conductive paste.

[0043] Therefore, regarding the rheology of the conductive paste required for roller transfer printing, it is preferable to have a high viscosity paste at low shear rates before and after roller transfer printing, and a low viscosity paste at high shear rates during roller transfer printing. If the viscosity is high at low shear rates, the coating properties on the roller before transfer and the coverage of the sides and ends of the solid electrolytic capacitor element after transfer become good (the conductive paste on the sides and ends of the solid electrolytic capacitor element has good shape retention when the viscosity recovers rapidly). On the other hand, if the viscosity is low at high shear rates, the uniformity (ease of leveling) and coating properties (ease of thin-layer formation) on the main surface of the solid electrolytic capacitor element are good.

[0044] Furthermore, the conductive paste described in this embodiment exhibits good performance at low shear rates (0.05–1 s). -1 At high shear rates (20–200 s), the viscosity is 0.4–35 Pa·s, which is high. Therefore, in the case of roller transfer printing, the coating properties on the circumferential surface of the roller before transfer are good. On the other hand, at high shear rates (20–200 s), the viscosity is also high. -1 At this temperature, the shear viscosity is 0.2–1.5 Pa·s, which is low. Therefore, in the case of roller transfer printing, it exhibits high uniformity and easy leveling on the main surface of solid electrolytic capacitor elements, and also provides good coating properties and facilitates thin-layer formation. Furthermore, the low shear rate (0.05–1 s) -1 With a thixotropic value of 5 to 20, it exhibits high thixotropy. Therefore, when roller transfer is performed, it returns to a high viscosity after roller transfer. As a result, the conductive paste transferred to the sides and ends of the solid electrolytic capacitor element remains unchanged, and the coverage of the sides and ends of the solid electrolytic capacitor element is improved.

[0045] Furthermore, if the shearing rate is between 0.05 and 1 s... -1 If the shear viscosity is less than 0.4 Pa·s, the paste will not return to a high viscosity after roller transfer, making it difficult to maintain the conductive paste transferred to the sides and ends of the solid electrolytic capacitor element. If the shear speed is between 0.05 and 1 s... -1 If the shear viscosity exceeds 35 Pa·s, it will become excessively high viscosity after roller transfer, and the film thickness on the main surface of the solid electrolytic capacitor element will become too thick, making it difficult to achieve thinner layers.

[0046] Additionally, if the shearing rate is 20–200 s -1 If the shear viscosity is less than 0.2 Pa·s, then during roller transfer printing, the viscosity becomes too low, resulting in poor coating properties on the roller's circumferential surface. If the shear speed is between 20 and 200 s... -1 If the shear viscosity exceeds 1.5 Pa·s, it will become excessively high in the case of roller transfer printing, resulting in undesirable conditions such as film thickness deviation caused by fiber drawing.

[0047] Furthermore, if the thixotropic value is less than 5, it will not return to a high viscosity after roller transfer, making it difficult to maintain the conductive paste transferred to the sides and ends of the solid electrolytic capacitor element. If the thixotropic value exceeds 20, it will become excessively viscous after roller transfer, making it difficult to level the main surface of the solid electrolytic capacitor element and increasing the film thickness deviation on the main surface.

[0048] At a shearing rate of 0.05–1 s -1 The preferred shear viscosity is 1 to 30 Pa·s, more preferably 2 to 30 Pa·s.

[0049] Shearing speed 20–200 s -1 The preferred shear viscosity is 0.2 to 0.8 Pa·s, more preferably 0.2 to 0.4 Pa·s.

[0050] The thixotropic value is preferably 5 to 15, more preferably 5 to 10.

[0051] In this specification, the shear viscosity at a certain shear rate can be measured at 25°C using an Anton Paar MCR302 modular compact rheometer. Furthermore, with this apparatus, rheological profiles can be continuously measured within the aforementioned shear rate range.

[0052] Additionally, in this specification, the shearing rate is 0.05 s. -1 Shear viscosity and shear rate 1s -1 The ratio of shear viscosity to thixotropic value is calculated as follows: Shear rates are measured at 0.05 s⁻¹. -1 and shear viscosity and shear rate (1s) at 25°C -1 And the shear viscosity at 25°C, and substitute it into the following formula 1.

[0053] Thixotropic value = shear rate 0.05s -1 Shear viscosity (Pa·s) / shear rate 1s -1 Shear viscosity (Pa·s) at the specified depth (Equation 1)

[0054] There are no particular limitations on the metal powder; for example, metal powders obtained by methods such as atomization, electrolysis, and chemical reduction can be used.

[0055] There are no particular limitations on the shape of the metal powder; for example, it can be spherical, flat, or flake-shaped. Different shapes of metal powder can also be mixed. For example, spherical metal powder (e.g., spherical silver powder) and flat metal powder (e.g., flat silver powder) can be used together.

[0056] The average particle size of the metal powder is not particularly limited, but it is preferably 1 to 10 μm, more preferably 1 to 5 μm.

[0057] The average particle size of the metal powder is defined as the median particle size of the equivalent circle diameter obtained from image resolution of the metal powder observed by a scanning electron microscope. The median particle size of the equivalent circle diameter refers to the particle size at which the cumulative percentage (D50) becomes 50% in the cumulative percentage distribution curve of particle size.

[0058] Furthermore, in the conductive paste according to this embodiment, the conductive powder is preferably a metal powder, and preferably does not contain any substances other than the metal powder.

[0059] Thermoplastic resins function as adhesive resins, but specific examples are not particularly limited; fluorinated resins, acrylic resins, polyester resins, etc., can be used. For example, TFE-propylene copolymers can be used as fluorinated resins. Similarly, saturated copolyester resins can be used as polyester resins. These thermoplastic resins can be used alone or in combination of two or more.

[0060] Solvents are used to dissolve thermoplastic resins and adjust shear viscosity and thixotropic value. They can be inorganic solvents, but organic solvents are preferred.

[0061] As organic solvents, for example, butyl carbitol acetate (BCA), carbitol acetate (CA), isoamyl acetate, butyl carbitol, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol), etc., can be used. These organic solvents can also be used alone or in combination of two or more.

[0062] The proportion of solid components in the total amount of conductive paste involved in this embodiment is not particularly limited, but is preferably 50 to 70% by weight, more preferably 55 to 65% by weight.

[0063] The proportion of metal powder in the solid content is not particularly limited, but it is preferably 60 to 95% by weight, more preferably 70 to 90% by weight.

[0064] The specific gravity of the conductive paste involved in this embodiment is not particularly limited, but it is preferably 1 to 4, and more preferably 1 to 2.

[0065] In this specification, the specific gravity of the conductive paste can be measured using a hydrometer.

[0066] As described above, the conductive paste according to this embodiment is suitable for manufacturing solid electrolytic capacitor elements, and is preferably a conductive paste for forming conductive layers of solid electrolytic capacitor elements by roller transfer printing. This improves the coatability when supplying the conductive paste to the circumferential surfaces of each roller used for roller transfer printing. Furthermore, leveling of the conductive paste is easier on the main surface of the solid electrolytic capacitor element, and thinning of the conductive paste layer is also easier. Moreover, the coverage of the conductive paste on the side and end faces of the solid electrolytic capacitor element is improved, thus enabling a lower ESR (equivalent series resistance) in the solid electrolytic capacitor incorporating this solid electrolytic capacitor element. Here, the conductive layer is preferably a silver layer, the conductive paste is preferably a silver paste, and the conductive paste layer is preferably a silver paste layer.

[0067] (Manufacturing method of solid electrolytic capacitor element)

[0068] Next, a method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention will be described.

[0069] The manufacturing method of the solid electrolytic capacitor element according to the embodiments of the present invention includes the following steps: supplying the conductive paste according to the present embodiment to a pair of rollers; transferring an assembly of solid electrolytic capacitor elements having element portions to the pair of rollers on which the conductive paste has been supplied; and transferring the conductive paste on the pair of rollers to the element portions.

[0070] According to the manufacturing method of the solid electrolytic capacitor element according to this embodiment, since the conductive paste according to this embodiment is used, the coating properties are good when the conductive paste is supplied to the peripheral surface of each roller. Furthermore, the conductive paste is easy to level on the main surface of the element portion, and the conductive paste layer is easy to thin. Moreover, the coverage of the conductive paste on the side and end faces of the element portion is improved, thus enabling the solid electrolytic capacitor having this element portion to achieve low ESR. In the manufacturing method of the solid electrolytic capacitor element according to this embodiment, the conductive paste is preferably silver paste, and the conductive paste layer is preferably a silver paste layer.

[0071] Hereinafter, the manufacturing method of the solid electrolytic capacitor element according to this embodiment will be described in more detail with the help of the accompanying drawings.

[0072] Figure 1 This is a top view schematically illustrating an example (elongated structure type) of an assembly of solid electrolytic capacitor elements used in a method for manufacturing a solid electrolytic capacitor element 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 element portion of an assembly of solid electrolytic capacitor elements. Figure 3This is a top view schematically illustrating an example of a process for performing a polarization masking 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 the process of 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 5 The enlarged cross-sectional view of the polarization section of the element shown.

[0073] go through Figures 1-4 The process shown prepares an assembly 10 of solid electrolytic capacitor elements having multiple element sections 11. Each element section 11 has a pair of main surfaces 11a and 11b, a pair of side surfaces 11c and 11d, and an end surface 11e.

[0074] Each component section 11 is a rectangular flat plate when viewed from above, such as... Figure 5 and Figure 6 As shown, it comprises: an anode foil 31 with a surface composed of a porous valve-acting metal substrate; 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 figure); two annular (extending in a strip shape) insulating members, namely insulating mask materials 35 and 37, are disposed around the anode foil 31 through the dielectric layer 33; and a solid electrolyte layer 39 is disposed on the anode foil 31 through the dielectric layer 33 at a position closer to the end face 11e of the insulating mask material 37. In each element part 11, the solid electrolyte layer 39 is opposite to the anode foil 31 through the dielectric layer 33.

[0075] 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.

[0076] The following is about Figures 1-4 Each process shown is explained.

[0077] 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 to the conveying substrate 15, which serves as the holding part 13, to produce an assembly 10 of solid electrolytic capacitor elements.

[0078] Thus, the assembly 10 of solid electrolytic capacitor elements includes a transfer substrate 15, which is made of metal or resin material, and is disposed parallel to the transfer direction of the assembly 10 being transferred in the conductive paste transfer process described later. The element portion 11 is disposed only on one side of the transfer substrate 15. The side surfaces 11c and 11d of the element portion 11 extend in a direction orthogonal to the transfer direction (holding portion 13), and the end face 11e of the element portion 11 extends parallel to the transfer direction (holding portion 13).

[0079] 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 rectangular thin film (foil) 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.

[0080] Furthermore, in this specification, "top view" refers to observation from the normal direction of the main surface of the anode foil.

[0081] The valve-acting metal matrix is ​​composed of valve-acting metals such as aluminum, tantalum, niobium, titanium, zirconium, etc., or alloys containing these metals.

[0082] Furthermore, the valve-acting metal substrate can be composed of a core and a porous part provided on at least one main surface of the core, and can be appropriately constructed by etching the surface of the metal foil, or by forming a porous micro-powder sintered body on the surface of the metal foil.

[0083] Figure 7 This is a top view schematically illustrating another example (double-opening 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.

[0084] The assembly 10 of solid electrolytic capacitor elements is not particularly limited to Figure 1 The elongated structure type shown can also be as follows: Figure 7 As shown, this is a double-opening structure (fishbone structure) type. In this case, the element part 11 is provided on both sides of the conveying substrate 15.

[0085] 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.

[0086] In either case, the conveying substrate 15 is different from the anode foil 31 and is a highly rigid component, which can prevent the assembly 10 of solid electrolytic capacitor elements from pulsating even in the conductive paste transfer process described later.

[0087] Figure 8 This is a top view schematically showing another example (elongated 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 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.

[0088] The assembly 10 of solid electrolytic capacitor elements may also be absent. Figure 1 and Figure 7 The conveying substrate 15 shown can also be used as follows: Figure 8 and Figure 9 As shown, a retaining portion 13 includes a bone portion 17 arranged parallel to the transport direction of the assembly 10 transported in the transfer process of the conductive paste described later. In this case, the element portion 11 contains the same material as the bone portion 17. Specifically, both are made of the same valve-acting metal substrate and are formed by cutting the same anode foil. The element portion 11 can be as follows: Figure 8 As shown, it can be set only on one side of bone 17 (elongated structure type), or as... Figure 9 As shown, it is set on both sides of the bone 17 (double-open structure (fishbone structure) type).

[0089] Next, as Figure 2 As shown, the component part 11 is coated with insulating mask material 35 for masking treatment for chemical formation.

[0090] For example, an insulating mask material 35 is formed 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 polyphenylene sulfone (PPS), polyether sulfone (PES), cyanate ester resins, fluoropolymers (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, etc.), compositions including soluble polyimide siloxanes and epoxy resins, polyimide resins, polyamide-imide resins, and their derivatives or precursors.

[0091] Furthermore, if the bone portion 17 is used instead of the conveying substrate 15, the masking treatment for this chemical formation is not required.

[0092] Next, the assembly 10 of solid electrolytic capacitor elements undergoes a formation process (anodization). 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 after it has been cut by laser processing or punching.

[0093] Alternatively, a chemically formed foil with aluminum oxide already deposited can be used as the valve action metal substrate. In this case, by chemically forming 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.

[0094] Next, as Figure 3 As shown, insulating mask material 37 is applied to the element part 11 to perform a masking treatment (polarization treatment) for polarization of the anode and cathode parts.

[0095] For example, an insulating mask material 37 is formed 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 polyphenylene sulfone (PPS), polyether sulfone (PES), cyanate ester resins, fluoropolymers (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, etc.), compositions including soluble polyimide siloxanes and epoxy resins, polyimide resins, polyamide-imide resins, and their derivatives or precursors.

[0096] 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 immersing the processing solution in the porous portion of the valve-acting metal substrate. After immersion for a predetermined time, the element portion 11 is pulled out of the processing solution and dried at a predetermined temperature and for a predetermined time. By repeating the immersion, pulling out, and drying process in the processing solution a predetermined number of times, the solid electrolyte layer 39 is formed. Alternatively, the solid electrolyte layer 39 can be formed by repeating the following operation a predetermined number of times: immersing in a processing solution containing a precursor of the solid electrolyte (a monomer that has been oxidatively polymerized into a solid electrolyte), and further immersing in a processing solution containing an oxidant that oxidatively polymerizes the precursor of the solid electrolyte.

[0097] Furthermore, the method for forming the solid electrolyte layer 39 (the coating method of the treatment solution containing the solid electrolyte or the coating method of the treatment solution containing the precursor of the solid electrolyte) is not particularly limited to the above-mentioned impregnation method. For example, it may also be coating using a dispenser or roller transfer printing. In addition, these methods may be combined.

[0098] The solid electrolyte layer 39 is formed integrally on the element portion 11 at a position 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.

[0099] A solid electrolyte layer 39 is disposed on the dielectric layer 33. For example... Figure 6As shown, the solid electrolyte layer 39 is preferably configured to fill the multiple pores (recesses) of the porous portion 31b of the anode foil 31. However, it is also possible for the solid electrolyte layer 39 to cover a portion of the outer surface of the dielectric layer 33, or for the pores (recesses) of the porous portion 31b of the anode foil 31 not to be filled by the solid electrolyte layer 39.

[0100] As the processing liquid containing a solid electrolyte, dispersions of conductive polymers such as polypyrrole, polythiophene, and polyaniline are used. Among these, polythiophene is 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 the processing liquid containing a solid electrolyte precursor, a liquid containing polymerizable monomers, such as 3,4-ethylenedioxythiophene, may also be used. Dopants such as polystyrene sulfonic acid may also be included in the polymerizable monomer. Additionally, an oxidizing agent may be included in the processing liquid containing the solid electrolyte precursor. 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.

[0101] Figure 10 This is a top view schematically illustrating an example of the process of forming a carbon layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0102] Next, carbon paste is used as cathode paste and transferred via roller transfer to each element portion 11 of the assembly 10 of solid electrolytic capacitor elements, such as... Figure 10 As shown, a carbon layer 41 is formed in each component part 11.

[0103] The carbon layer 41 is formed on the entire element portion 11 at a position closer to the end face 11e than the insulating mask material 37. The carbon layer 41 can be formed such that a portion of the insulating mask material 37 side of the solid electrolyte layer 39 is exposed on the outer surface of the element portion 11, or it can be formed as follows: Figure 10 As shown, it completely covers the solid electrolyte layer 39 and can also be connected to the insulating mask material 37.

[0104] Furthermore, the method for forming the carbon layer 41 (the method for applying carbon paste) is not particularly limited to roller transfer printing; for example, it can also be immersion printing, but roller transfer printing is preferred. In addition, the application of carbon paste itself can also be omitted.

[0105] Figure 11 This is a top view schematically illustrating an example of the process of forming a conductive layer in the element portion of an assembly of solid electrolytic capacitor elements.

[0106] Next, the conductive paste described in this embodiment is used as a cathode paste and transferred to each element portion 11 of the assembly 10 of solid electrolytic capacitor elements by roller transfer printing, such as... Figure 11 As shown, a conductive layer 43 is formed in each component portion 11. The conductive layer 43 is preferably a silver layer.

[0107] The conductive layer 43 is formed on the component portion 11 at a position closer to the end face 11e than the insulating mask material 37.

[0108] Furthermore, the conductive layer 43 is formed such that a portion of the insulating mask material 37 side of the solid electrolyte layer 39 and the carbon layer 41 is exposed on the outer surface of the element portion 11, but it can also be as follows: Figure 11 As shown, the carbon layer 41 can be completely covered, and it can also be bonded to the insulating mask material 37. In the absence of a carbon layer 41, it is preferable that the conductive layer 43 completely covers the solid electrolyte layer 39. This further improves the moisture resistance reliability of the solid electrolytic capacitor element. Furthermore, it is preferable that the conductive layer 43 is bonded to the insulating mask material 37.

[0109] Here, using Figure 12 This further explains the roller transfer device used for roller transfer printing of conductive paste and the roller transfer printing process of conductive paste.

[0110] Figure 12 This is a schematic diagram of an example of a roller transfer apparatus used for roller transfer of conductive paste. Furthermore, this roller transfer apparatus can also be used for applying carbon paste.

[0111] 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. The assembly 10 of solid electrolytic capacitor elements, unwound from the unwinding section 210, is conveyed in the order of the roller transfer printing section 220A, the temporary drying section 230, and the drying section 240, and then wound up by the winding section 250. The assembly 10 is conveyed in each section at a predetermined conveying speed.

[0112] The unwinding section 210 releases the assembly 10 of solid electrolytic capacitor elements wound into a roll on the unwinding reel. The roller transfer section 220A transfers conductive 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 conductive paste transferred to the element portion 11 of the assembly 10 by conveying the conductive paste. The drying section 240 heat-dries the temporarily dried conductive paste while conveying the assembly 10. The winding section 250 winds the dried conductive paste assembly 10 into a roll on a winding reel.

[0113] The roller transfer section 220A has a plurality of transfer rollers 221 for transporting the assembly 10 of solid electrolytic capacitor elements, a pair of rollers (transfer rollers) 222 for transporting the element parts 11 of the assembly 10 between them, and a distributor 223 and a scraper 224 provided on each roller 222.

[0114] A pair of rollers 222 are positioned on either side of the assembly 10 of solid electrolytic capacitor elements conveyed by the transfer rollers 221. Each roller 222 has a circumferential surface made of metal or rubber, on which grooves for supplying conductive paste are formed. The depth of the grooves can be appropriately set considering the desired coating thickness of the conductive paste. Alternatively, grooves may not be formed on the circumferential surface of each roller 222, or the circumferential surface may be smooth. Furthermore, the circumferential surface may be roughened by sandblasting or other surface treatments. Moreover, each circumferential surface of the pair of rollers 222 has a predetermined interval relative to the two main surfaces 11a and 11b of the element portion 11 of the assembly 10, and the conductive paste contacts the element portion 11, transferring the conductive paste on the circumferential surfaces of the pair of rollers 222 onto the two main surfaces 11a and 11b of the element portion 11 of the electronic component 40.

[0115] Each distributor 223 supplies an appropriate amount of conductive paste to the corresponding roller 222, ensuring that the conductive paste does not drip from the circumferential surface of the roller 222. Therefore, the consumption of conductive paste is kept to a minimum. Furthermore, the supply of conductive paste to the roller 222 can be continuous or intermittent.

[0116] Each scraper 224 is configured to be separated from the circumferential surface of the corresponding roller 222 by a predetermined distance, and the amount of conductive paste is adjusted to an appropriate level by scraping the conductive paste adhering to the circumferential surface of the corresponding roller 222. In addition, for example, if the conductive paste has a low viscosity, scraping based on the scraper 224 may not be necessary.

[0117] use Figure 12 The roller transfer device 200 shown first transfers the carbon paste to... Figure 4 After the solid electrolyte layer 39 of the element part 11 of the assembly 10 is formed, the carbon paste is dried to form a carbon layer 41 (see reference). Figure 10 ).

[0118] Similarly, using Figure 12 The roller transfer apparatus 200 shown transfers the conductive paste according to this embodiment onto... Figure 10 After the carbon layer 41 of the element part 11 of the assembly 10 shown is formed, the conductive paste is dried to form the conductive layer 43 (see reference). Figure 11 ).

[0119] More specifically, firstly, conductive 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, conductive paste is supplied to each roller 222 from each distributor 223, and the amount of conductive paste is adjusted by each scraper 224.

[0120] The conductive paste involved in this embodiment operates at low shear rates (0.05–1 s). -1 The lower shear viscosity is 0.4 to 35 Pa·s, which is a high viscosity. Therefore, the conductive paste has good coatability when supplied to the circumferential surface of each roller 222.

[0121] Carbon paste contains carbon particles as conductive components, as well as resin components such as epoxy resin and phenolic resin, thus exhibiting conductivity.

[0122] The viscosity and thixotropic properties of the carbon paste are set with consideration of the shearing 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, slow drying is achieved, thereby preventing drying on the circumferential surface of the roller.

[0123] The viscosity and thixotropic properties of the conductive paste involved in this embodiment are as described above. Furthermore, since it is used in roller transfer printing, a high-boiling-point solvent is preferably used as the organic solvent. By using a high-boiling-point solvent, slow drying is achieved, thereby preventing drying on the circumferential surface of the roller.

[0124] 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 to which the conductive paste according to this embodiment is supplied. At this time, the assembly 10 is conveyed along the extending direction of the holding portion 13, such that only the element portions 11 pass between the adjacent pair of rollers 222, thereby continuously transferring conductive paste to multiple element portions 11. Between the pair of 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 a solid electrolyte layer 39 if no carbon layer 41 is formed) is conveyed.

[0125] The conveying speed of the assembly 10 is, for example, 20 to 150 mm / s. The rotational speed (rpm) of each roller 222 is calculated based on the conveying speed and 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) and the thickness of the conductive paste, but is set to be at least larger than the thickness of the anode foil.

[0126] In addition, the thickness of the anode foil can be 100-150 μm, but is preferably 110-130 μm.

[0127] In addition, the thickness of the element portion 11 (the thickness after the solid electrolyte layer is formed) can also be 110 to 180 μm, but is preferably 120 to 160 μm.

[0128] The assembly 10 of solid electrolytic capacitor elements can also be as follows Figure 12 As shown, the material is conveyed between a pair of rollers 222 while being conveyed in a direction orthogonal to the horizontal direction. This makes it easy to ensure that the thickness of the conductive paste on the two main surfaces 11a and 11b of the component section 11 is uniform. This is because it is easy to ensure that the amount of conductive paste supplied to the pair of rollers 222 is uniform.

[0129] Figure 13 This is a schematic diagram of another example of a roller transfer device used for roller transfer of conductive paste. Furthermore, this roller transfer device can also be used for applying carbon paste.

[0130] The roller transfer printing device 200 can also be like Figure 13 Instead of the vertical conveying roller transfer section 220A, the horizontal conveying roller transfer section 220B is provided. 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 parts 11 of the assembly 10 between them, and a distributor 223 and a scraper 224 provided on each roller 222.

[0131] However, in the horizontal conveying roller transfer section 220B, the assembly 10 of solid electrolytic capacitor elements is conveyed horizontally while being conveyed between a pair of rollers 222. This solution is suitable for cases where the conveying substrate 15 is used as the holding part 13. This is because the conveying substrate 15 is relatively hard, making it difficult to bend in the vertical direction during conveying. In addition, in the case of horizontal conveying, if the rigidity of the holding part 13 is low, the assembly 10 may pulsate, but if the conveying substrate 15 is highly rigid, pulsation of the assembly 10 can be prevented even during horizontal conveying.

[0132] 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 conductive 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 conductive paste transferred onto it.

[0133] Then, conductive paste from a pair of rollers 222 is transferred onto a pair of main surfaces 11a and 11b of the component section 11, such that the conductive paste transferred to the main surfaces 11a and 11b connects to a pair of side surfaces 11c and 11d and an end surface 11e. More specifically, conductive paste overflowing from between each roller 222 and each main surface 11a, 11b wraps around and contacts the side surfaces 11c and 11d and the end surface 11e from the two main surfaces 11a and 11b, thereby connecting the conductive paste to the side surfaces 11c and 11d and the end surface 11e. Therefore, as Figure 14 and Figure 15 As shown, the conductive paste layers 50 on the two main surfaces 11a and 11b, the two side surfaces 11c and 11d, and the end face 11e do not create interfaces at their boundaries, but are seamlessly (uninterruptedly) connected.

[0134] The conductive paste used here is suitable for high shear rates (20–200 s). -1 The low shear viscosity (0.2–1.5 Pa·s) is therefore low, making it easy to level the conductive paste on the main surface of the component section 11 when transferring it onto the component section 11 using a pair of rollers 222. Furthermore, the low shear velocity (0.05–1 s) of the conductive paste facilitates thinning of the paste layer. -1 The thixotropic value is 5 to 20, which is high thixotropic. Therefore, the coating of conductive paste on the two sides 11c and 11d and the end face 11e of the element part 11 is improved.

[0135] Figure 16 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor element manufactured by the manufacturing method of the solid electrolytic capacitor element according to an embodiment of the present invention, corresponding to... Figure 5 The sectional view shown. Figure 17 yes Figure 16 The solid electrolytic capacitor element shown is a cross-sectional view along the YY line.

[0136] As a result of the above, Figure 16 and Figure 17 As shown, solid electrolytic capacitor elements 30 are formed in each element section 11. Furthermore, the conductive layers 43 on each surface of the solid electrolytic capacitor element 30 do not form interfaces at their boundaries, but are seamlessly (uninterruptedly) connected.

[0137] Furthermore, in each element section 11, the solid electrolyte layer 39, carbon layer 41, and conductive layer 43 (solid electrolyte layer 39 and conductive 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, and the anode foil 31 on the opposite side functions as an anode. Therefore, by using each element section 11, a two-terminal type solid electrolytic capacitor can be manufactured.

[0138] For example, multiple component sections 11 are stacked, and the anode and cathode are respectively connected to the lead frame to form a stack.

[0139] The stacked and adjacent element portions 11 can also be bonded to each other using a conductive adhesive, but it is preferable to remelt the thermoplastic resin contained in the conductive layer 43 of each element portion 11 to achieve integration.

[0140] The laminate is then sealed, and the lead frame is shaped and cut to form the external terminals. The result is a low-ESR, two-terminal solid electrolytic capacitor.

[0141] Figure 18 This is a schematic cross-sectional view illustrating an example of a solid electrolytic capacitor.

[0142] Figure 18 The solid electrolytic capacitor 100 shown is a two-terminal solid electrolytic capacitor with a lead frame 101 located at the bottom and solid electrolytic capacitor elements 30 stacked sequentially on the lead frame 101.

[0143] In addition, Figure 18 The diagram only shows the characteristic parts of the solid electrolytic capacitor structure, omitting details such as the connection between the anode and the outside, and the resin seal. However, these details can be addressed using the methods typically used in solid electrolytic capacitors.

[0144] Alternatively, the lead frame 101 may not be positioned at the bottom layer, or it may be sandwiched between the cathodes of two solid electrolytic capacitor elements 30. Therefore, multiple solid electrolytic capacitor elements 30 can be stacked by overlapping their cathodes to create a multi-layer solid electrolytic capacitor element 30. The lead frame 101 is then placed on top of the multi-layer solid electrolytic capacitor element 30, and other cathodes of solid electrolytic capacitor elements 30 are further overlapped on the lead frame 101 to create a multi-layer solid electrolytic capacitor element 30 with the cathode portion sandwiched between them. This multi-layer solid electrolytic capacitor element 30 is then heated and pressurized.

[0145] The following examples illustrate more specifically embodiments of the conductive paste and the method for manufacturing the solid electrolytic capacitor element of the present invention. However, the present invention is not limited to these embodiments.

[0146] Silver powder, thermoplastic resin, and organic solvent were mixed in the proportions specified in Table 1 below to obtain the conductive pastes of the examples and comparative examples.

[0147]

[0148] Spherical silver powder with an average particle size of 2 μm and flat silver powder with an average particle size of 10 μm were used as silver powder. Saturated copolyester resin or tetrafluoroethylene (TFE) propylene copolymer was used as thermoplastic resin. Butyl carbitol acetate (BCA) or isoamyl acetate was used as organic solvent.

[0149] Table 1 also records the percentage (by weight) of solid components in the total amount of each conductive paste.

[0150] (proportion)

[0151] The specific gravity of each conductive paste was determined by a hydrometer.

[0152] (Shear viscosity and thixotropic value)

[0153] Using the modular compact rheometer MCR302 manufactured by Anton Paar, the shear rate was measured from 0.01 to 1000 s⁻¹. -1 The shear viscosity (Pa·s) of each conductive paste was measured at 25°C within the specified range.

[0154] The shear rate was measured at 0.05 s. -1 and shear viscosity (Pa·s) and shear rate (1s) at 25°C. -1 The shear viscosity (Pa·s) at 25°C was used to calculate the thixotropic value of each conductive paste using Equation 1 above.

[0155] Table 2 below and Figure 19 The measurement results are shown. Figure 19 This is a graph showing the dependence of the shear viscosity of the conductive pastes of Examples 2, 3 and Comparative Example 2 on shear rate.

[0156]

[0157] As a result, the conductive paste according to the present invention has good coating properties on the circumferential surface of the roller when roller transfer is performed. When roller transfer is performed, the uniformity on the main surface of the solid electrolytic capacitor element is high and leveling is easy. Furthermore, the coating properties are good and thin-layer formation is easy. The side surfaces and end surfaces of the solid electrolytic capacitor element are well covered.

[0158] The following information is disclosed in this specification.

[0159] <1>

[0160] A conductive paste comprising metal powder, thermoplastic resin, and solvent.

[0161] At a shearing rate of 0.05–1 s -1 Below this, the shear viscosity is 0.4–35 Pa·s.

[0162] Shearing speed 20–200 s -1 At this point, the shear viscosity is 0.2–1.5 Pa·s.

[0163] Shearing speed 0.05s -1 Shear viscosity and shear rate 1s -1 The ratio of shear viscosity to thixotropic value is 5 to 20.

[0164] <2>

[0165] According to the conductive paste described in <1>, among which,

[0166] The conductive paste is a conductive paste used to form a conductive layer of a solid electrolytic capacitor element by roller transfer.

[0167] <3>

[0168] A method for manufacturing a solid electrolytic capacitor element includes the following steps:

[0169] The conductive paste described in <1> or <2> is supplied to a pair of rollers;

[0170] An assembly of solid electrolytic capacitor elements, including the element section, is conveyed between the pair of rollers to which the conductive paste has been supplied; and

[0171] The conductive paste on the pair of rollers is transferred to the element portion.

[0172] Explanation of reference numerals in the attached figures

[0173] 10. An assembly of solid electrolytic capacitor elements;

[0174] 11. Components Section;

[0175] 11a and 11b are the main surfaces of the component sections;

[0176] 11c, 11d Side views of component sections;

[0177] 11e End face of component section;

[0178] 13. Holding section;

[0179] 15. Transport substrate;

[0180] 17. Bones;

[0181] 30. Solid electrolytic capacitor elements;

[0182] 31. Anode foil;

[0183] 31a Metal substrate;

[0184] 31b Porous portion;

[0185] 33. Dielectric layer;

[0186] 35, 37 Insulating mask material;

[0187] 39. Solid electrolyte layer;

[0188] 41. Carbon layer;

[0189] 43. Conductive layer;

[0190] 50. Conductive paste layer;

[0191] 100 Solid electrolytic capacitor;

[0192] 101 Leadframe;

[0193] 200-roller transfer printing device;

[0194] 210 Unwinding section;

[0195] 220A vertical conveyor roller transfer section;

[0196] 220B Horizontal conveyor roller transfer printing section;

[0197] 221 Conveying roller;

[0198] 222 rollers (transfer rollers);

[0199] 223 Distributor;

[0200] 224 Scraper;

[0201] 230 Temporary drying section;

[0202] 240 Drying section;

[0203] 250. Receiving Section.

Claims

1. A conductive paste comprising metal powder, thermoplastic resin, and solvent. At a shearing rate of 0.05–1 s -1 Below this, the shear viscosity is 0.4–35 Pa·s. Shearing speed 20–200 s -1 At this point, the shear viscosity is 0.2–1.5 Pa·s. Shearing speed 0.05s -1 Shear viscosity and shear rate 1s -1 The ratio of shear viscosity to thixotropic value is 5 to 20.

2. The conductive paste according to claim 1, wherein, The conductive paste is a conductive paste used to form a conductive layer of a solid electrolytic capacitor element by roller transfer.

3. A method for manufacturing a solid electrolytic capacitor element, comprising the following steps: The conductive paste according to claim 1 or 2 is supplied to a pair of rollers; An assembly of solid electrolytic capacitor elements, including the element section, is conveyed between the pair of rollers to which the conductive paste has been supplied; and The conductive paste on the pair of rollers is transferred to the element portion.

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