JP7806474B2 - Capacitor and manufacturing method thereof - Google Patents

Description

The present disclosure relates to a capacitor having a cathode foil including a carbon layer and a method for manufacturing the same.

A capacitor includes an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil, and is capable of storing electricity. Among such capacitors, a basic capacitor including a cathode foil made solely of aluminum foil is known. Recently, a capacitor including a cathode foil including a carbon layer has also been known (see, for example, Patent Document 1). The carbon layer has the effect of increasing the capacitance of the cathode foil, for example.

Japanese Patent Application Laid-Open No. 2006-80111

Electrode foils such as anode foils and cathode foils are connected to the lead terminals by connection means such as stitch connections or cold welding. The connection means used to connect the lead terminals is selected taking into consideration connection requirements such as connection cost, size of the lead terminal, or required connection strength. The connection means used to connect the lead terminals may be determined without any choice based on specifications prepared by the customer.

In the cold pressure welding process to form a cold pressure weld, for example, a connection mold is pressed against electrode foil placed on a drawer terminal, applying pressure to the electrode foil and drawer terminal. The pressure-receiving portion of the electrode foil that receives pressure from the connection mold basically moves toward the drawer terminal in the direction of the pressure, and the pressure-receiving portion of the electrode foil and the drawer terminal are pressure-welded, thereby connecting the electrode foil to the drawer terminal.

When pressure is applied to the electrode foil and lead terminal during cold welding, a portion of the pressure-receiving portion moves along the surface of the connecting mold from the pressure-applied area to the outside of the pressure-applied area. Furthermore, the carbon layer is formed by applying a slurry composed primarily of carbon particles and a binder that binds the carbon particles together to the surface of the aluminum foil. In cathode foils that include a carbon layer, the binder contained in the carbon layer makes it easier for a portion of the pressure-receiving portion to move from the pressure-applied area to the outside of the pressure-applied area. Because the carbon layer moves from the pressure-applied area to the outside of the pressure-applied area, the pressing force of the cathode foil against the lead terminal is relatively dispersed in the direction of movement of the carbon layer, reducing the pressing force of the cathode foil against the lead terminal. Therefore, when a cathode foil that includes a carbon layer is connected to a lead terminal using a cold welding process similar to that used for cathode foils consisting solely of metal foil, there is a risk of insufficient connection.

Furthermore, if the pressure applied by the connection mold is increased to increase the pressing force of the cathode foil against the lead terminal, the pressure applied to the cathode foil will increase, which may have an adverse effect on the cathode foil.

Patent Document 1 does not disclose or suggest such issues, and the configuration disclosed in Patent Document 1 cannot solve such issues.

The first objective of this disclosure is to provide a cold-welded structure that has electrical and physical connection strength between a cathode foil containing a carbon layer and a lead terminal, for example.

A second object of the present disclosure is to improve connectivity to cathode foils that include, for example, a carbon layer.

To achieve the above object, according to a first aspect of the present disclosure, a capacitor includes a cathode foil including a carbon layer disposed on a surface of a base foil, and a lead terminal connected to the cathode foil by a pressure-contact portion. The pressure-contact portion includes a first connection portion group disposed at a charge inlet/outlet portion of the lead terminal and a second connection portion group disposed at a terminal end of the lead terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group. The first connection portion group includes a plurality of first connection portions, the number of the first connection portions is three or more, and the distance between the first connection portion group is equal to or less than half the overlap distance between the lead terminal and the cathode foil, and the second connection portion group includes a smaller number of second connection portions than the first connection portions, the number of the second connection portions is two or more, and the distance between the second connection portion group is equal to or less than one-fourth the overlap distance .

According to a second aspect of the present disclosure, a capacitor includes a cathode foil including a carbon layer disposed on a surface of a base foil, and a lead terminal connected to the cathode foil by a pressure-contact portion. The pressure-contact portion includes a first connection portion group disposed at a charge inlet/outlet portion of the lead terminal and a second connection portion group disposed at a terminal end portion of the lead terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group. The first connection portion group includes a plurality of first connection portions, and the second connection portion group includes a smaller number of second connection portions than the first connection portions, and the spacing between the second connection portions is the same as or approximately the same as the spacing between the first connection portions.

In the above capacitor, the distance between the non-pressure-welded portions may be greater than the distance between the second connection portions.

In the above capacitor, the width of the first connection portion and the second connection portion in the width direction of the draw-out terminal may be 0.5 times or more and 0.8 times or less the width of the draw-out terminal.

In the above capacitor, the concave angle formed by the hypotenuse of the first connection portion or the second connection portion in one cross section may be greater than or equal to 100 degrees and less than or equal to 160 degrees.

To achieve the above object, according to a third aspect of the present disclosure, a method for manufacturing a capacitor includes the steps of: preparing a cathode foil including a carbon layer disposed on a surface of a base foil; and press-welding the overlapped cathode foil and a lead terminal together to connect the cathode foil and the lead terminal at a press-welded portion. The press-welded portion includes a first connection portion group disposed at a charge inlet/outlet portion of the lead terminal and a second connection portion group disposed at a terminal end of the lead terminal, and a non-press-welded portion is formed between the first connection portion group and the second connection portion group. The first connection portion group includes a plurality of first connection portions, the number of the first connection portions is three or more and the distance between the first connection portion group is equal to or less than half the overlapping distance between the lead terminal and the cathode foil , and the second connection portion group includes a smaller number of second connection portions than the first connection portions, the number of the second connection portions is two or more and the distance between the second connection portion group is equal to or less than one-fourth the overlapping distance .
According to a fourth aspect of the present disclosure, a method for manufacturing a capacitor includes the steps of: preparing a cathode foil including a carbon layer disposed on a surface of a base foil; and press-welding the stacked cathode foil and a lead terminal together to connect the cathode foil and the lead terminal at a pressure-welded portion. The pressure-welded portion includes a first group of connection portions disposed at a charge inlet/outlet portion of the lead terminal and a second group of connection portions disposed at a terminal end of the lead terminal, and a non-pressure-welded portion is formed between the first group of connection portions and the second group of connection portions. The first group of connection portions includes a plurality of first connection portions, and the second group of connection portions includes a smaller number of second connection portions than the first connection portions, and the spacing between the second connection portions is the same as or approximately the same as the spacing between the first connection portions.

The present invention can achieve, for example, any of the following effects:

(1) By forming the non-pressure-welded portion, the pressure applied during the cold pressure welding process can be concentrated on the first and second connection groups of the pressure-welded portion. Therefore, the pressure required for cold pressure welding can be ensured at the first and second connection groups, while the total pressure applied to the cathode foil and lead terminal can be reduced.

(2) Cathode foil damage can be reduced.

(3) The first group of connections is located at the charge inlet/outlet area. Since the connections are concentrated in areas where electricity flows preferentially, good capacitor characteristics are obtained.

(4) The second connection group is disposed at the end of the lead terminal. When an external force is applied to the lead terminal, for example, rotation of the lead terminal about the first connection group as a fulcrum can be suppressed, and stress concentration in the first connection group can be suppressed.

4A and 4B are diagrams illustrating an example of a terminal connection portion between a cathode foil and a lead terminal of a capacitor according to an embodiment. FIG. 2 is a diagram showing an example of an end surface of a cathode foil. 1A and 1B are diagrams illustrating an example of cold pressure welding processing. 10A and 10B are diagrams showing an example of a state in which pressure is applied to a cathode foil and a lead terminal. FIG. 10 is a diagram illustrating an example of a pressing member.

Figure 1 shows an example of a terminal connection between a cathode foil and a lead terminal of a capacitor according to an embodiment. Figure 2 shows an example of an end surface of a cathode foil. The configurations shown in Figures 1 and 2 are merely examples, and the technology of this disclosure is not limited to such configurations. Note that in this embodiment, the terminal connection includes the portion where the cathode foil 6 is cold-pressed to the lead terminal 4 and the surrounding area.

Capacitor 2 is an example of an electronic component, such as an electrolytic capacitor. Capacitor 2 includes, for example, a capacitor element (not shown), lead terminal 4, an electrolyte, a sealing member, and an outer case (not shown).

The capacitor element includes a cathode foil 6, an anode foil, and a separator. The cathode foil 6, the anode foil, and the separator are stacked and wound together to form a wound element, with the separator positioned between the cathode foil 6 and the anode foil. This wound element forms the capacitor element.

The cathode foil 6 constitutes the cathode electrode of the capacitor 2. The cathode foil 6 is, for example, a strip-shaped foil and includes a substrate foil 12 and a carbon layer 14. The substrate foil 12 is, for example, a valve metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil. As shown in FIG. 2, the surface of the substrate foil 12 has irregularities 16 formed, for example, by etching, that is, depressions 16-1 and protrusions 16-2, thereby increasing the surface area of the substrate foil 12. The surface of the substrate foil 12 may also include, for example, tunnel-shaped or spongy etching pits, which may form the depressions 16-1 and protrusions 16-2.

The carbon layer 14 is disposed, for example, on both sides of the substrate foil 12. The carbon layer 14 may also be disposed on only one side of the substrate foil 12. As shown in FIG. 2, the carbon layer 14 partially penetrates into the depressions 16-1 of the asperities 16, and therefore adheres closely to and engages with the asperities 16 of the substrate foil 12. In other words, the carbon layer 14 has a surface shape that engages with the asperities 16. The carbon layer 14 is disposed on the outside of the substrate foil 12, and the cathode foil 6 has a two-layer structure consisting of the substrate foil 12 and the carbon layer 14, or a three-layer structure in which the carbon layer 14 is disposed on both sides of the substrate foil 12. The carbon layer 14 contains a carbon material as the main material, and further contains a binder and a dispersant as additives.

Carbon materials include activated carbon, carbon black, carbon nanohorns, amorphous carbon, natural graphite, artificial graphite, graphitized ketjen black, mesoporous carbon, and fibrous carbon. Activated carbon is produced from raw materials such as natural plant tissues like coconut husks, synthetic resins like phenol, and fossil fuels like coal, coke, and pitch. Carbon black includes ketjen black, acetylene black, channel black, and thermal black. Fibrous carbon includes carbon nanotubes and carbon nanofibers. Carbon nanotubes may be single-walled carbon nanotubes, which have a single graphene sheet, or multi-walled carbon nanotubes (MWCNTs), which have two or more graphene sheets rolled coaxially to form multiple tube walls.

The carbon material is preferably carbon black, which is spherical carbon. Using spherical carbon black with an average primary particle diameter of 100 nm or less makes the carbon layer 14 denser and allows the carbon layer 14 to adhere more easily to the surface-expanding layer, thereby reducing interfacial resistance. A mixture containing spherical carbon and graphite is also preferred as the carbon material. Graphite can be, for example, natural graphite, artificial graphite, or graphitized ketjen black, and can be in a variety of shapes, including flakes, scales, chunks, clay, spheres, and flakes. The graphite is preferably flake-shaped or flake-shaped, and the aspect ratio of the minor axis to the major axis of the graphite is preferably in the range of 1:5 to 1:100. With flake-shaped or flake-shaped graphite having the above-mentioned aspect ratio, the spherical carbon can be pressed into the depressions 16-1 of the irregularities 16, such as etching pits, so that part of the carbon layer 14 extends into the etching pits. Therefore, the anchor effect allows the carbon layer 14 to adhere firmly to the substrate foil 12.

When the average particle size of the graphite is between 6 μm and 10 μm, it is possible to achieve effects such as suppressing the decrease in capacitance due to high-temperature environmental load. Furthermore, when the average particle size of the graphite is 6 μm or less, it is possible to increase the capacitance of the capacitor 2 while suppressing the decrease in capacitance due to high-temperature environmental load. Furthermore, when the average particle size of the graphite is 6 μm or less, it becomes easier to retain the graphite within the carbon layer 14, allowing the amount of binder added to be reduced. Reducing the amount of binder added increases the proportion of carbon material. This reduces the electrical resistance of the cathode foil 6 and the equivalent series resistance (ESR) of the capacitor 2. The aforementioned average particle size values are based on the median diameter, or so-called D50.

When the carbon material is a mixture of graphite and spherical carbon, in order to obtain the combined effect of graphite and spherical carbon, the mass ratio of graphite to the mixture of graphite and spherical carbon [mass of graphite / (mass of graphite + mass of spherical carbon)] is, for example, in the range of 0% to 90%. The mass ratio of graphite may be 0%. In other words, graphite does not need to be added to the carbon layer 14.

The binder is a resin-based binder such as styrene butadiene rubber, polyvinylidene fluoride, or polytetrafluoroethylene, which binds the carbon material. The dispersant is, for example, sodium carboxymethyl cellulose. The carbon layer 14 is made from, for example, an aqueous solution in which spherical carbon is dispersed. The dispersant can disperse the carbon material in the aqueous solution.

The maximum static friction coefficient of the surface of the carbon layer 14 may be adjusted to, for example, 0.6 or greater. If the maximum static friction coefficient of the surface of the carbon layer 14 is 0.6 or greater, slippage of the carbon layer 14 against a pressing member 42 (Figure 5), such as a mold, used in the cold welding process is suppressed, improving the cold welding connection between the cathode foil 6 and the lead terminal 4. The maximum static friction coefficient of the surface of the carbon layer 14 can be adjusted, for example, by adjusting the content of graphite, which has high sliding properties. If the mass ratio of graphite is, for example, in the range of 0% or greater and 18% or less, the maximum static friction coefficient of the surface of the carbon layer 14 will be, for example, 0.6 or greater.

The anode foil constitutes the anode electrode of the capacitor 2. The anode foil is, for example, a valve metal foil such as tantalum foil or aluminum foil, and is, for example, a strip-shaped foil. The surface of the anode foil has irregularities formed, for example, by etching, and includes a dielectric oxide film formed, for example, by chemical conversion treatment. The irregularities formed by etching have, for example, a porous structure.

The separator is placed between the anode foil and the cathode foil 6 to prevent short circuits between the anode foil and the cathode foil 6. The separator is an insulating material, including kraft, and may also include other separator materials such as manila hemp, esparto, hemp, rayon, cellulose, and mixtures thereof.

The drawer terminal 4 is formed of a conductive metal such as aluminum. The drawer terminal 4 may be, for example, a lead terminal or a tab terminal. The lead terminal is composed of, for example, an aluminum wire and a metal wire, which are connected by arc welding or the like. The aluminum wire has a roughly cylindrical round bar portion and a flat portion 20 formed by pressing the round bar portion or the like. The round bar portion has a sloped portion on the flat portion 20 side, whose thickness linearly decreases to the thickness of the flat portion 20. In the case of a lead terminal, a terminal connection portion is formed on the flat portion 20. A tab terminal is, for example, made of a strip-shaped thin metal foil, one end of which is connected to an external terminal attached to the sealing material, and the other end of which is formed with a terminal connection portion. In the case of a tab terminal, the other side of the strip-shaped thin metal foil forms the flat portion 20. In the capacitor 2 according to this embodiment, the flat portion 20 included in the drawer terminal 4 is, for example, a thin metal plate or metal tab, has a strip shape, and includes a charge inlet/outlet portion 22, a terminal end portion 24, and a middle portion 26. The charge entrance/exit section 22 partially protrudes from a width edge 28 of the cathode foil 6 to allow electrical connection to other components such as an external terminal. The terminal end section 24 overlaps the cathode foil 6 at a position away from the opposite width edge of the cathode foil 6. The middle section 26 is located between the charge entrance/exit section 22 and the terminal end section 24 and overlaps the cathode foil 6.

The flat portion 20 of the drawer terminal 4 (hereinafter simply referred to as the "drawer terminal 4") is connected to the cathode foil 6 by a pressure-welding portion 30. The pressure-welding portion 30 is formed by cold pressure welding and includes a first connection portion group 32 and a second connection portion group 34.

The first connection portion group 32 is disposed at the charge inlet/outlet portion 22 of the lead terminal 4. The first connection portion group 32 connects the lead terminal 4 to the cathode foil 6 near the width edge 28 of the cathode foil 6, thereby shortening the charge path between the cathode foil 6 and the outside. The first connection portion group 32 includes a plurality of first connection portions 36 (e.g., seven first connection portions 36) densely arranged in a row at equal intervals, for example, a spacing S. The spacing S is defined as the distance between the centers of two adjacent first connection portions 36. The spacing S is, for example, greater than or equal to the length CL of one first connection portion 36 and less than twice the length CL, e.g., 2.5 millimeters, as shown in the following equation (1):
CL≦S≦2×CL (1)

The number of first connection portions 36 may be two. Preferably, the number of first connection portions 36 is three or more, and preferably such that the distance L1 of the first connection portion group 32 is one-half or less of the overlap distance L of the overlapping region between the lead terminal 4 and the cathode foil 6. When the number of first connection portions 36 is three or more, the first connection portions 36 can provide all or most of the necessary mechanical connection strength and electrical connection area. When the number of first connection portions 36 is such that the distance L1 of the first connection portion group 32 is one-half or less of the overlap distance L, the dispersion of pressure during cold pressure welding due to an increase in the number of first connection portions 36 is suppressed, i.e., the pressure can be concentrated. Since the first connection portion group 32 is arranged in the charge inlet/outlet portion 22 and the number of first connection portion groups 32 is adjusted, the mechanical connection strength and the necessary electrical connection area can be secured while concentrating the pressure during cold pressure welding. The first connection group 32 is placed in an electrically efficient position, i.e., in a part where the charge path is relatively short and electricity flows preferentially, improving the characteristics of the capacitor 2.

The second connection portion group 34 is arranged at the end portion 24 of the draw-out terminal 4. The second connection portion group 34 includes a plurality of second connection portions 38 (e.g., three second connection portions 38) arranged in a row, closely spaced, with an equal spacing of, for example, S. The spacing S and length CL of the second connection portion group 34 are the same as those of the first connection portion group 32, and the spacing S of the second connection portions 38, similar to the first connection portion 36, satisfies, for example, the above-described formula (1) relative to the length CL of the second connection portion 38. The spacing S and length CL of the second connection portions 38 may be different from those of the first connection portion 36. The number of second connection portions 38 may be one. Preferably, the number of second connection portions 38 is two or more, and preferably the number is such that the distance L2 of the second connection portion group 34 is one-fourth or less of the overlap distance L. If the number of second connection portions 38 is two or more, the mechanical connection strength required to suppress movement of the lead terminal 4 along the foil surface relative to the cathode foil 6 can be obtained. If the number of second connection portions 38 is such that the distance L2 of the second connection portion group 34 is one-fourth or less of the overlap distance L, dispersion of pressure during cold pressure welding due to an increase in the number of second connection portions 38 can be suppressed, i.e., the pressure can be concentrated. The second connection portion group 34 can concentrate the pressure during cold pressure welding while ensuring mechanical connection strength at a location away from the first connection portion group 32. Therefore, for example, when an external force is applied to the lead terminal 4, rotation of the lead terminal 4 about the first connection portion group 32 as a fulcrum can be suppressed, suppressing stress concentration in the first connection portion group 32.

Since the first connection group 32 has the necessary mechanical connection strength and electrical connection area, the second connection group 34 only needs to suppress movement of the lead terminal 4 along the foil surface relative to the cathode foil 6. The number of second connection portions 38 can be fewer than the number of first connection portions 36.

The second connection group 34 is separated from the first connection group 32 by a distance equal to or greater than the distance L2 of the second connection group 34, and a non-insulation-welded portion 40 is formed between the first connection group 32 and the second connection group 34. The formation of the non-insulation-welded portion 40 allows the pressure applied during the cold welding process to be concentrated on the first connection group 32 and the second connection group 34, allowing the insulation-welded portion 30 to be formed with reduced pressure, thereby suppressing stress generated within the lead terminal 4 and the cathode foil 6 during the cold welding process. The distance L3 of the non-insulation-welded portion 40 is, for example, equal to or greater than the distance L2 of the second connection group 34 to ensure a sufficient non-insulation-welded portion 40. The maximum value of the distance L3 of the non-insulation-welded portion 40 is naturally determined by subtracting the minimum necessary distances L1 and L2 from the overlap distance L, and further subtracting the terminal distances L4 and L5. End distance L4 is the distance from width edge 28 of cathode foil 6 to first connection group 32, and end distance L5 is the distance from end 41 of lead terminal 4 to second connection group 34. End distances L4 and L5 are preferably, for example, 0.2 to 1 times the length CL of first connection portion 36 or second connection portion 38. When end distances L4 and L5 are 0.2 times or more the length CL, for example, it is possible to prevent the pressure from cold welding from affecting width edge 28 of cathode foil 6 and end 41 of lead terminal 4. When end distances L4 and L5 are 1 time or less the length CL, for example, it is possible to position first connection group 32 and second connection group 34 closer to the ends of the overlapping region of lead terminal 4 and cathode foil 6, i.e., width edge 28 and end 41, respectively.

In the width direction of the drawer terminal 4, the width CW of the first connection portion 36 and the second connection portion 38 (hereinafter referred to as "connection portions 36, 38") is preferably 0.5 to 0.8 times the width W of the drawer terminal 4. If the width CW is 0.5 times or more the width W, more than half of the overlapping area in the width W direction can be used for cold welding, thereby increasing the mechanical connection strength or electrical connection area. If the width CW is 0.8 times or less the width W, the effects of pressure from the cold welding process on the side edges of the drawer terminal 4 can be suppressed.

The anode foil is connected to another lead terminal (not shown) (hereinafter referred to as "lead terminal 4" for convenience) by cold welding or other connection means.

The electrolyte contains at least an electrolytic solution, which fills the voids within the capacitor element and the separator.

The sealing material may be, for example, a phenolic laminate plate with an external terminal attached. The external terminal attached to the phenolic laminate plate is connected to a flat portion 20 protruding from the width edge 28. The sealing material may also be formed from, for example, insulating rubber. In this case, a lead terminal 4, such as the lead terminal described above, protrudes from one end surface of the capacitor element. The sealing material has an insertion hole at a position corresponding to the lead terminal 4, and the round bar portion and metal wire of the lead terminal 4 pass through the insertion hole in the sealing material and are exposed to the outside of the capacitor 2.

The outer case is, for example, a cylindrical aluminum case with a bottom. The capacitor element and a portion of the lead terminal 4 are inserted into the outer case together with the electrolyte. A sealing member is installed in the opening of the outer case to seal the interior of the outer case. In other words, the capacitor element and a portion of the lead terminal 4 are sealed inside the outer case.

[Capacitor manufacturing process]

The manufacturing process for capacitor 2 is an example of a capacitor manufacturing method of the present disclosure, and includes, for example, the steps of preparing an anode foil, preparing a cathode foil 6, preparing a separator, connecting a lead terminal 4 to the electrode foil, preparing a capacitor element, and sealing the capacitor element. Figure 3 shows an example of cold pressure welding performed in the step of connecting a lead terminal 4 to an electrode foil. Figure 4A shows an example of the state of pressure being applied to the cathode foil 6 and lead terminal 4, and Figure 4B shows an enlarged view of portion IVB enclosed by a dashed line in Figure 4A. Figure 5 shows an example of a pressing member 42. Details of the cold pressure welding device that secures the pressing member 42 are omitted in Figure 4A. The configurations and procedures shown in Figures 3 to 5 are merely examples, and the technology of the present disclosure is not limited to such configurations or procedures.

In the anode foil production process, the surface of a valve metal foil such as tantalum foil or aluminum foil is etched to form irregularities on the surface of the valve metal foil. The etched valve metal foil is then chemically treated to form a dielectric oxide film on the surface of the valve metal foil. The valve metal foil is etched by applying a current to the foil while it is immersed in an aqueous chloride solution such as hydrochloric acid or salt. The applied current may be either direct or alternating current. In the chemical treatment of valve metal foil, a voltage is applied to the valve metal foil while it is immersed in an electrolyte containing a solution of ammonium borate, ammonium borate, ammonium phosphate, ammonium adipate, or the like. The chemically treated valve metal foil is then cut to produce anode foil.

In the cathode foil 6 production process, the surface of a valve metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil is etched to form irregularities 16 on the surface of the valve metal foil, thereby producing the base foil 12. The etching on the cathode foil 6 side may be the same as or different from the etching on the anode foil side. A carbon layer 14 is formed on the etched valve metal foil, i.e., the base foil 12, and the valve metal foil with the carbon layer 14 formed is then cut to produce the cathode foil 6.

The carbon layer 14 is produced as follows: The carbon material, binder, and dispersant described above are added to a diluent and mixed using a dispersion process such as a mixer, jet mixing (jet collision), ultracentrifugation, or ultrasonic treatment to form a slurry. The binder is added, for example, in an amount necessary to bind the carbon material, and the dispersant is added, for example, in an amount necessary to disperse the carbon material. Therefore, the amounts of binder and dispersant added are much smaller than the amount of carbon material added. When graphite is used as the carbon material, the graphite may be pulverized using a pulverizer such as a bead mill or ball mill to adjust the average particle size of the graphite before adding it to the diluent.

Diluents include, for example, alcohols, hydrocarbon solvents, aromatic solvents, amide solvents, water, and mixtures thereof. Alcohols include, for example, methanol, ethanol, or 2-propanol. Amide solvents include, for example, N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF).

The slurry is applied to the etched valve metal foil, i.e., the substrate foil 12. Because the substrate foil 12 has an asperity 16, the carbon material penetrates into the asperity 16, improving adhesion. The slurry is dried to volatilize the solvent, forming a carbon layer 14, which is then pressed. Adding a pressing process to the formation of the asperity 16 allows the carbon material to be forced into the pores of the asperity 16 and to deform along the asperity 16, further improving adhesion and fixation between the carbon layer 14 and the substrate foil 12. If the carbon material contains graphite, the pressing aligns the graphite and deforms it to conform to the asperity 16 of the substrate foil 12. Furthermore, when the graphite is pressed against the asperity 16, the spherical carbon is pressed into the recesses 16-1, such as the pores, of the substrate foil 12. This allows the slurry to adhere to the substrate foil 12, resulting in a carbon layer 14 that adheres to the substrate foil 12.

In the separator manufacturing process, the separator material described above is cut to produce the separator.

In the process of connecting the lead terminals 4 to the electrode foils, the lead terminals 4 are connected to the cathode foil 6 and the anode foil, respectively.

As shown in Figure 3A, the cathode foil 6 is placed on the lead-out terminal 4. The cathode foil 6 and lead-out terminal 4, which are placed on top of each other, are placed between the pressing member 42 and the pressure-receiving plate 44 so that the cathode foil 6 is positioned on the pressing member 42 side.

The lead terminal 4 is cold-pressurized to the cathode foil 6 by a cold welding process. During the cold welding process, the distance between the pressing member 42 and the pressure plate 44 is narrowed in an unheated state, and the pressing member 42 applies pressure to the cathode foil 6 and lead terminal 4, for example, from the cathode foil 6 side, as shown in FIG. 3B and FIG. 4A. This causes the lead terminal 4 to be cold-pressurized to the cathode foil 6. As shown in FIG. 5, the pressing member 42 has multiple protrusions 48 on one surface 46. Each protrusion 48 has a tip 50 on a straight line parallel to the one surface 46, two first inclined surfaces 52, and two second inclined surfaces 54. The angle between the tip 50 and each first inclined surface 52 is, for example, 165 degrees. In other words, the first protrusion angle formed by the two first inclined surfaces 52 is, for example, 150 degrees. The second protrusion angle formed by the two second inclined surfaces 54 is, for example, 150 degrees.

The pressing member 42 has, for example, holes or protrusions for mounting (not shown), and is attached to the cold pressure welding equipment by bolts or fitting. The pressing member 42 is fixed to the cold pressure welding equipment on multiple surfaces (e.g., three surfaces) excluding the surface 46 on which the protrusions 48 are formed, thereby suppressing variations in the pressure applied from the multiple protrusions 48 to the cathode foil 6 and the lead terminal 4.

During the cold welding process, one surface 46 of the pressing member 42 is maintained parallel to the surface of the cathode foil 6. Therefore, the connection portions 36, 38 have, for example, trapezoidal pressure marks in the cross sections shown in FIGS. 3B and 3C, and have, for example, triangular pressure marks in cross sections perpendicular to the cross sections shown in FIGS. 3B and 3C, for example, as shown in FIGS. 4A and 4B. The first recess angle α formed by the hypotenuse 66 of the connection portions 36, 38 having trapezoidal pressure marks coincides with or nearly coincides with the first protrusion angle. The second recess angle β formed by the hypotenuse 68 of the connection portions 36, 38 having triangular pressure marks coincides with or nearly coincides with the second protrusion angle. Because the first and second protrusion angles of the protrusions 48 are, for example, 100 degrees or greater, shear stresses generated in the connection portions 36, 38 are reduced. In other words, fracture of the cathode foil 6 is suppressed at the boundary between the connection portions 36, 38 and their outer surfaces, ensuring good connection between the cathode foil 6 and the lead terminal 4. Furthermore, because the first and second protrusion angles of the protrusions 48 are, for example, 100 degrees or more, the area of the connection portions 36, 38 is increased, further improving the connectivity between the cathode foil 6 and the lead terminal 4. Note that, in order to form the protrusions 48, it is preferable that the first and second protrusion angles be, for example, 160 degrees or less.

The process for connecting the lead terminal 4 to the anode foil may be the same as or different from the process for connecting the lead terminal 4 to the cathode foil 6.

In the capacitor element manufacturing process, a first separator is placed between the anode foil and cathode foil 6, and a second separator is placed on the outside of the anode foil or cathode foil 6. The anode foil, cathode foil 6, and first and second separators are wound together to manufacture the capacitor element.

In the capacitor element encapsulation process, the capacitor element, impregnated with an electrolyte such as an electrolytic solution, is inserted into the exterior case, and then a sealing material is attached to the opening of the exterior case to create capacitor 2.

The above embodiment provides the following advantages, for example:

(1) The cathode foil 6 including the carbon layer 14 has a higher surface fracture strength than a basic cathode foil that does not include the carbon layer 14. In other words, the cathode foil 6 is more easily stretched than a basic cathode foil. Therefore, in the capacitor 2, the non-pressure-welded portion 40 is disposed between the first connection group 32 and the second connection group 34. The number of connection portions 36, 38 is reduced, thereby reducing the area of the press-welded portion 30. The pressure applied by the pressing member 42 is concentrated on the first connection group 32 and the second connection group 34 of the reduced press-welded portion 30, thereby improving the connection between the first connection group 32 and the second connection group 34. Furthermore, because the number of connection portions 36, 38 is limited, the pressure required for cold welding can be secured at each connection portion 36, 38, while the total pressure applied to the cathode foil 6 and the lead-out terminal 4 can be reduced. This reduces the occurrence of damage to the cathode foil 6.

(2) The first connection group 32 is arranged in the charge inlet/outlet section 22. By concentrating the connection parts in areas where electricity flows preferentially, good capacitor characteristics can be obtained.

(3) The second connection group 34 is disposed at the end 24 of the draw-out terminal 4. When an external force is applied to the draw-out terminal 4, for example, rotation of the draw-out terminal 4 around the first connection group 32 as a fulcrum can be suppressed, thereby suppressing stress concentration in the first connection group 32.

(4) The first recess angle α of the oblique side 66 and the second recess angle β of the oblique side 68 are, for example, 150 degrees, and preferably 100 degrees or more and 160 degrees or less. Therefore, fracture of the cathode foil 6 is suppressed at the boundary between the connection portions 36, 38 and the outside of the connection portions 36, 38, and good connection between the cathode foil 6 and the lead-out terminal 4 can be achieved. Furthermore, because the first recess angle α and the second recess angle β are close to 180 degrees, the area of the connection portions 36, 38 is increased, further improving the connectivity between the cathode foil 6 and the lead-out terminal 4.

The following are some of the features and variations of the embodiment described above.

(1) In the above embodiment, the capacitor element is a wound element. However, the capacitor element may also be a laminated element, for example, in which multiple flat anode foils, cathode foils 6, and separators are stacked.

(2) The materials for the anode foil, cathode foil 6, separator, outer case, sealing material, and electrolyte are not limited to those described in the above embodiment. These materials may also be other materials used in aluminum electrolytic capacitors or similar capacitors.

(3) The material of the carbon layer 14 is not limited to that described in the above embodiment. The material forming the carbon layer 14 may be any conductive material containing carbon. Furthermore, the state of adhesion or engagement of the carbon layer 14 with the base foil 12 is not limited to that described in the above embodiment.

(4) In the above embodiment, the connecting portions 36, 38 have a rectangular shape as shown in FIG. 1. However, the connecting portions 36, 38 may have a shape other than a rectangular shape, such as a curved or serpentine shape.

(5) In the cold pressure welding process of the above embodiment, the pressing member 42 applies pressure to the cathode foil 6 and the lead terminal 4 from the cathode foil 6 side. However, the pressing member 42 may also apply pressure from the lead terminal 4 side.

(6) In the above embodiment, the pressing member 42 has holes, protrusions, etc., and is attached to the cold pressure welding device by bolts or fitting. The pressing member 42 is also fixed to or supported on the cold pressure welding device by three surfaces. However, the attachment of the pressing member 42 to the cold pressure welding device is not limited to the attachment described in the above embodiment. It is sufficient that the pressing member 42 forms the pressure welding portion 30.

(7) In the above embodiment, the pressure contact portion 30 is formed by one pressing member 42, but the pressure contact portion 30 may also be formed by a combination of multiple pressing members. For example, the first connection group 32 may be formed by a first pressing member, and then the second connection group 34 may be formed by a second pressing member, thereby forming the pressure contact portion 30 as a whole.

As explained above, the most preferred embodiment of the present disclosure has been described, but the present disclosure is not limited to the above description, and it goes without saying that various modifications and changes are possible for those skilled in the art based on the gist of the invention as described in the claims or disclosed in the specification, and such modifications and changes are naturally included in the scope of the present disclosure.

The technology of the present disclosure is useful for connecting a cathode foil including a carbon layer to a lead terminal and for use in a capacitor including these.

2 Capacitor 4 Lead terminal 6 Cathode foil 12 Base foil 14 Carbon layer 16 Concave/convex 16-1 Depression 16-2 Protrusion 20 Flat portion 22 Charge inlet/outlet portion 24 End portion 26 Middle portion 28 Width end 30 Pressure-contact portion 32 First connection portion group 34 Second connection portion group 36 First connection portion 38 Second connection portion 40 Non-pressure-contact portion 41 End 42 Pressing member 44 Pressure-receiving plate 66, 68 Hypotenuse

Claims (7)

a cathode foil including a carbon layer disposed on a surface of a base foil;
a lead terminal connected to the cathode foil by a pressure-welding portion;
Equipped with
the pressure-contact portion includes a first connection portion group arranged at an electric charge inlet/outlet portion of the lead-out terminal and a second connection portion group arranged at an end portion of the lead-out terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group;
the first connection portion group includes a plurality of first connection portions, the number of the first connection portions is three or more, and the distance between the first connection portions in the first connection portion group is equal to or less than half of the overlap distance between the lead terminal and the cathode foil,
A capacitor characterized in that the second connection portion group includes a smaller number of second connection portions than the first connection portions, the number of second connection portions arranged is two or more, and the distance between the second connection portions of the second connection portion group is one-fourth or less of the overlap distance . a cathode foil including a carbon layer disposed on a surface of a base foil;
a lead terminal connected to the cathode foil by a pressure-welding portion;
Equipped with
the pressure-contact portion includes a first connection portion group arranged at an electric charge inlet/outlet portion of the lead-out terminal and a second connection portion group arranged at an end portion of the lead-out terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group;
the first connection portion group includes a plurality of first connection portions,
the second connection portion group includes a smaller number of second connection portions than the first connection portions,
A capacitor characterized in that the spacing between the second connection portions is the same as or approximately the same as the spacing between the first connection portions. 3. The capacitor according to claim 1, wherein the distance between the non-pressure-contact portions is greater than the distance between the second connection portions. 4. A capacitor according to claim 1 , wherein the width of the first connection portion and the second connection portion in the width direction of the lead-out terminal is 0.5 times or more and 0.8 times or less the width of the lead-out terminal. 5. The capacitor according to claim 1 , wherein a concave angle formed by the oblique sides of the first connection portion or the second connection portion in one cross section is 100 degrees or more and 160 degrees or less. preparing a cathode foil including a carbon layer disposed on a surface of a substrate foil;
a step of press-welding the overlapped cathode foil and the lead terminal to connect the cathode foil and the lead terminal at a press-welded portion;
Equipped with
the pressure-contact portion includes a first connection portion group arranged at an electric charge inlet/outlet portion of the lead-out terminal and a second connection portion group arranged at an end portion of the lead-out terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group;
the first connection portion group includes a plurality of first connection portions, the number of the first connection portions is three or more, and the distance between the first connection portions in the first connection portion group is equal to or less than half of the overlap distance between the lead terminal and the cathode foil,
A method for manufacturing a capacitor, characterized in that the second connection portion group includes a smaller number of second connection portions than the first connection portions, the number of second connection portions arranged is two or more, and the distance between the second connection portions of the second connection portion group is less than one-fourth of the overlap distance . preparing a cathode foil including a carbon layer disposed on a surface of a substrate foil;
a step of press-welding the overlapped cathode foil and the lead terminal to connect the cathode foil and the lead terminal at a press-welded portion;
Equipped with
the pressure-contact portion includes a first connection portion group arranged at an electric charge inlet/outlet portion of the lead-out terminal and a second connection portion group arranged at an end portion of the lead-out terminal, and a non-pressure-contact portion is formed between the first connection portion group and the second connection portion group;
the first connection portion group includes a plurality of first connection portions,
the second connection portion group includes a smaller number of second connection portions than the first connection portions,
The method for manufacturing a capacitor, wherein the spacing between the second connection portions is the same as or approximately the same as the spacing between the first connection portions.