Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/0029—Processes of manufacture
  • H01G9/0032—Processes of manufacture formation of the dielectric layer
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/0029—Processes of manufacture
  • H01G9/0036—Formation of the solid electrolyte layer
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/004—Details
  • H01G9/04—Electrodes or formation of dielectric layers thereon
  • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/15—Solid electrolytic capacitors

Definitions

• the invention relates to a method for the production of electrolytic capacitors with low equivalent series resistance and low leakage current, produced by this process E lektrolytkondensatoren and the use of such electrolytic capacitors.
• a commercially available solid electrolytic capacitor is usually composed of a porous metal electrode, an oxide layer on the metal surface, an electrically conductive solid introduced into the porous structure, an external electrode (contacting), such as an electrode. a silver layer, as well as other electrical contacts and an encapsulation.
• solid electrolytic capacitors are tantalum, aluminum, niobium and niobium oxide capacitors with charge transfer complexes, brownstone or polymer solid electrolytes.
• porous bodies has the advantage that, due to the large surface area, a very high capacity density, i. high electrical capacity in a small space.
• ⁇ -conjugated polymers are particularly suitable as solid electrolytes.
• ⁇ -conjugated polymers are also referred to as conductive polymers or as synthetic metals. They are increasingly gaining economic importance because polymers have advantages over metals in terms of processability, weight, and targeted chemical properties modification.
• Examples of known ⁇ -conjugated polymers are polypyrroles, polythiophenes, polyanilines, polyacetylenes, polyphenylenes and poly (p-phenylene-vinylenes), where a particularly important and industrially used polythiophene is the poly-3,4- (ethylene-1,2-ethylene) -dioxy) thiophene, often referred to as poly (3,4-ethylenedioxythiophene), because it has a very high conductivity in its oxidized form.
• ESR equivalent series resistances
• European Patent EP-A-340 512 describes the preparation of a solid electrolyte from 3,4-ethylene-1,2-dioxythiophene and the use of its cationic polymer produced by oxidative polymerization as a solid electrolyte in electrolytic capacitors.
• Poly (3,4-ethylenedioxythiophene) as a substitute for manganese dioxide or charge-transfer complexes in solid electrolytic capacitors lowers due to the higher electrical Conductivity the equivalent series resistance of the capacitor and improves the frequency response.
• a disadvantage of this and similar methods is that the conductive polymer is generated by polymerization in situ in the electrolytic capacitor.
• the monomer e.g. 3,4-ethylene-l, 2-dioxythiophene, and oxidizing agent in the presence of solvents together or sequentially introduced into the porous metal body and then polymerized.
• such a chemical reaction is undesirable in the manufacture of electronic components, since it is very difficult to always run the chemical reaction identically in millions of small porous components to produce capacitors of the same specification.
• oxidizing agents can damage the dielectric (oxide layer) on the metal electrode.
• transition metal salts e.g. Fe (i ⁇ ) salts
• reaction products of the polymerization not only the electrically conductive polymer but also the reduced metal salts, e.g. Fe (II) salts in the electrode body back.
• reduced metal salts e.g. Fe (II) salts in the electrode body back.
• this is expensive and does not succeed completely, i. residues of the metal salts always remain in the electrode body.
• transition metals can damage the dielectric, so that the resulting increased residual currents significantly reduce the life of the capacitors or even make it impossible to use the capacitors under harsh conditions, such as high temperatures and / or high air humidity.
• a further disadvantage of chemical in situ processes for the production of solid electrolytic capacitors is that, as a rule, anions of the oxidizing agent or optionally other monomeric anions serve as counterions for the conductive polymer. Due to their small size, however, they are not sufficiently stable bound to the polymer. As a result, in particular at elevated operating temperatures of the capacitor, the diffusion of the counterions and thus an increase in the equivalent series resistance (ESR) of the capacitor can occur.
• ESR equivalent series resistance
• the alternative use of high molecular weight polymeric counterions in the chemical in situ Polymerization does not lead to adequate conductive films and therefore not to low ESR values.
• Polymerization of monomers can also be carried out electrochemically in the absence of oxidizing agents.
• the electrochemical polymerization requires that first a conductive film is deposited on the insulating oxide layer of the metal electrode. This in turn requires an in-situ polymerization with all the disadvantages listed above. Finally, this layer then has to be electrically contacted for each individual metal electrode. This contacting is very expensive in mass production and can damage the oxide layer.
• the electrodeposition in the pores of the porous metal electrode is very difficult because the deposition due to the electrical potential course takes place primarily on the outside of the electrode body.
• the object was therefore to provide such a method and the capacitors thus improved.
• a further disadvantage of chemical in situ processes for the preparation of the solid electrolyte is that it can not be used to produce solid electrolytic capacitors based on an electrode material of niobium or niobium oxide, which are characterized by a low residual current.
• a further object was, therefore, to provide such a method for producing such solid polymer electrolyte capacitors whose electrode materials are based on niobium or niobium oxide, and the corresponding capacitors.
• capacitors whose solid electrolyte is produced with dispersions containing particles of an electrically conductive polymer having an average diameter of 1-100 nm and a conductivity greater than 10 S / cm fulfill these requirements.
• the subject of the present invention is therefore a process for producing an electrolytic capacitor, at least comprising
• the particles B) of the conductive polymer in the dispersion A) have a mean diameter of 1-100 nm and films made of particles B) have a specific conductivity of greater than 10 S / cm.
• the specific conductivity of the films produced from particles B) is the specific conductivity of the films in the dried state.
• the particles B) must be smaller than 100 nm in order to penetrate into porous electrode bodies whose pore diameter is greater than 500 nm and thus 5 times larger than the particles B). Furthermore, it is surprising that such small particles B) form a sufficiently conductive film in the electrode body, since the resistance of the contact resistances between the particles is dominated and usually increases with decreasing size of the particles.
• the determination of the diameter of the particles B) takes place via an ultracentrifuge measurement. The general procedure is in Colloid Polym. Be. 267, 1113-1116 (1989). For particles B) swelling in the dispersion, the particle size is determined in the swollen state.
• a diameter distribution of the particles B) refers to a mass distribution of the particles in the dispersion as a function of the particle diameter.
• the particles B) of the conductive polymer in the dispersion A) in the process preferably have an average diameter of 1 to 80 nm, more preferably of 1 to 50 nm, most preferably of 5 to 40 nm.
• the particles B) of the conductive polymer in the dispersion A) preferably have a d 90 value of the diameter distribution of less than 150 nm, particularly preferably less than 100 nm, very particularly preferably less than 80 nm and more preferably less than 50 nm.
• the particles B) of the conductive polymer in the dispersion A) in the process preferably have a di 0 value of the diameter distribution greater than 1 nm, particularly preferably greater than 3 nm, very particularly preferably greater than 5 nm.
• the di 0 value of the diameter distribution indicates that 10% of the total mass of all particles B) of the conductive polymer in the dispersion A) can be assigned to those particles B) which have a diameter less than or equal to the dio value.
• the d 90 value of the diameter distribution states that 90% of the total mass of all particles B) of the conductive polymer in the dispersion A) can be assigned to particles B) having a diameter smaller than or equal to the d 9 o value.
• Dispersions A) are preferably used whose films in the dried state have a specific conductivity of greater than 10 S / cm, particularly preferably greater than 20 S / cm, very particularly preferably greater than 50 S / cm, very preferably greater than 100 S / cm and in one particular preferred embodiment greater than 200 S / cm have.
• the dispersion A) in the process preferably has a metal cation content of less than 5000 mg / kg, more preferably less than 1000 mg / kg, most preferably less than 200 mg / kg.
• the dispersion A) in the process preferably has a content of transition metals of less than 1000 mg / kg, more preferably less than 100 mg / kg, most preferably less than 20 mg / kg.
• the dispersion A) in the process preferably has an iron content of less than 1000 mg / kg, more preferably less than 100 mg / kg, most preferably less than 20 mg / kg.
• the low concentrations of metals in the dispersions have the great advantage that the dielectric is not damaged in the formation of the solid electrolyte and in later operation of the capacitor.
• the electrode material forms in the electrolytic capacitor produced by the method according to the invention a porous body with a high surface area, and is e.g. in the form of a porous sintered body or a roughened film.
• this porous body will also be referred to for short as the electrode body.
• the electrode body covered with a dielectric is also referred to below as the oxidized electrode body.
• the term "oxidized electrode body” also includes those electrode bodies that are covered with a dielectric that was not produced by oxidation of the electrode body.
• the electrode body covered with a dielectric as well as completely or partially with a solid electrolyte is also referred to below for short as the capacitor body.
• the outer surface of the capacitor body is understood to mean the outer surfaces of the capacitor body.
• polymers encompasses all compounds having more than one identical or different repeat unit.
• conductive polymers in particular the class of compounds of the ⁇ -conjugated polymers, which have an electrical conductivity after oxidation or reduction.
• Such ⁇ -conjugated polymers are preferably understood to be conductive polymers which, after oxidation, have an electrical conductivity of the order of at least l ⁇ S cm -1 .
• the particles B) of the electrically conductive polymer in the dispersion A) preferably contain at least one polythiophene, polypyrrole or polyaniline, which are optionally substituted.
• the particles B) of the electrically conductive polymer contain at least one polythiophene having repeating units of the general formula (I) or the general formula (II) or recurring units of the general formulas (I) and (II)
• A represents an optionally substituted C 1 -C 5 -alkylene radical
• R is a linear or branched, optionally substituted C r Cig-alkyl radical, an optionally substituted C 5 -C 2 cycloalkyl group, an optionally substituted C 6 -C 4 aryl, an optionally substituted C 7 -C 8 - aralkyl, is an optionally substituted C 1 -C 4 -hydroxyalkyl radical or a hydroxyl radical,
• x stands for an integer from 0 to 8.
• radicals R are attached to A, they may be the same or different.
• polythiophenes having repeating units of the general formula (I) or (U) or recurring units of the general formula (I) and (II) in which A is an optionally substituted C 2 -C 3 -alkylene radical and x is 0 or 1 stands.
• a conductive polymer of the solid electrolyte is poly (3,4-ethylenedioxythiophene), which is optionally substituted.
• poly is understood to mean that more than one identical or different recurring unit is contained in the polymer or polythiophene.
• the polythiophenes contain a total of n repeating units of the general formula (I) or the general formula (II) or the general formulas (I) and (II), wherein n is an integer from 2 to 2000, preferably 2 to 100, is.
• the repeating units of the general formula (I) and / or (U) may each be the same or different within a polythiophene. Preference is given to polythiophenes having in each case the same recurring units of the general formula (I) or (II) or (I) and (II).
• the polythiophenes preferably carry H.
• C 1 -C 5 -alkylene radicals A are preferably methylene, ethylene, n-propylene, n-butylene or n-pentylene.
• Ci-Cig-alkyl R are preferably linear or branched Ci-Cig alkyl radicals such as methyl, ethyl, n- or iso-propyl, n-, iso-, sec- or tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1, 2-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n- Nonyl, n-decyl, n-undecyl, n-dodecyl, n-do
• substituents of the radicals A and / or the radicals R in the context of the invention are numerous organic groups in question, for example alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halogen, ether, thioether, disulfide , Sulfoxide, sulfone, sulfonate, amino, aldehyde, keto, carboxylic acid ester, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane and alkoxysilane groups, and carboxylamide groups.
• Suitable substituents for polyaniline or polypyrrole are, for example, the abovementioned radicals A and R and / or the further substituents of the radicals A and R in question. Preference is given to unsubstituted polyanilines.
• the polythiophenes used as solid electrolyte in the preferred process may be neutral or cationic. In preferred embodiments, they are cationic, "cationic" referring only to the charges located on the polythiophene backbone Depending on the substituent on the R radicals, the polythiophenes can carry positive and negative charges in the structural unit, with the polythiophenes bearing charge positive charges on the polythiophene backbone and the negative If appropriate, charges are present on the radicals R substituted by sulfonate or carboxylate groups. In this case, the positive charges of the polythiophene main chain can be partially or completely saturated by the optionally present anionic groups on the radicals R.
• the polythiophenes in these cases can be cationic, neutral or even anionic. Nevertheless, they are all considered as cationic polythiophenes in the context of the invention, since the positive charges on the polythiophene main chain are relevant.
• the positive charges are not shown in the formulas because their exact number and position can not be determined properly. However, the number of positive charges is at least 1 and at most n, where n is the total number of all repeating units (equal or different) within the polythiophene.
• the cationic polythiophenes require anions as counterions.
• Counterions may be monomeric or polymeric anions, the latter also referred to below as polyanions.
• Polymeric anions are preferred over monomeric anions because they contribute to film formation and due to their size lead to thermally more stable electrically conductive films.
• Polymeric anions may here be, for example, anions of polymeric carboxylic acids, such as polyacrylic acids, polymethacrylic acid or polymaleic acids, or polymeric sulfonic acids, such as polystyrenesulfonic acids and polyvinylsulfonic acids. These polycarboxylic and sulfonic acids may also be copolymers of vinyl carboxylic and vinyl sulfonic acids with other polymerizable monomers such as acrylic acid esters and styrene.
• polymeric carboxylic acids such as polyacrylic acids, polymethacrylic acid or polymaleic acids
• polymeric sulfonic acids such as polystyrenesulfonic acids and polyvinylsulfonic acids.
• These polycarboxylic and sulfonic acids may also be copolymers of vinyl carboxylic and vinyl sulfonic acids with other polymerizable monomers such as acrylic acid esters and styrene.
• an anion of a polymeric carboxylic acid or sulfonic acid is preferred as the polymeric anion.
• polystyrene sulfonic acid PSS
• the molecular weight of the polyanionic polyacids is preferably from 1 000 to 2 000 000, more preferably from 2 000 to 500 000.
• the polyacids or their alkali metal salts are commercially available, for example polystyrenesulfonic acids and polyacrylic acids, or else can be prepared by known processes (see, for example, Houben Weyl , Methods of Organic Chemistry, Vol. E 20 Macromolecular Substances, Part 2, (1987), p. 1141).
• Polymer (s) anion (s) and electrically conductive polymers may in dispersion A) in particular in a weight ratio of 0.5: 1 to 50: 1, preferably from 1: 1 to 30: 1, more preferably 2: 1 to 20 : 1 be included.
• the weight of the electrically conductive polymers corresponds to the initial weight of the monomers used, assuming that complete conversion takes place during the polymerization.
• Examples of monomeric anions are those of C 1 -C 20 -alkanesulfonic acids, such as methane, ethane, propane, butane or higher sulfonic acids, such as dodecanesulfonic acid, of aliphatic perfluorosulfonic acids, such as trifluoromethanesulfonic acid, perfluorobutanesulfonic acid or perfluorooctanesulfonic acid, of aliphatic C 1 -C 20 -carboxylic acids such as 2-ethylhexylcarboxylic acid, aliphatic perfluorocarboxylic acids such as trifluoroacetic acid or perfluorooctanoic acid, and aromatic, optionally substituted by Ci-C2 ( ) alkyl sulfonic acids such as benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid or the dode
• Preferred as monomeric anions are the anions of p-toluenesulfonic acid, methanesulfonic acid or camphorsulfonic acid.
• Cationic polythiophenes which contain anions as counterions for charge compensation are also often referred to in the art as polythiophene / (poly) anion complexes.
• the dispersions A) may contain one or more dispersants D).
• dispersants D which may be mentioned are the following solvents: aliphatic alcohols, such as methanol, ethanol, isopropanol and butanol; aliphatic ketones such as acetone and methyl ethyl ketone; aliphatic carboxylic acid esters such as ethyl acetate and butyl acetate; aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane, heptane and cyclohexane; Chlorinated hydrocarbons such as dichloromethane and dichloroethane; aliphatic nitriles such as acetonitrile, aliphatic sulfoxides and sulfones such as dimethylsulfoxide and sulfolane; aliphatic carboxylic acid amides such as methylacetamide, dimethylacetamide and
• Preferred dispersants D) are water or other protic solvents such as alcohols, for example methanol, ethanol, i-propanol and butanol, and mixtures of water with these alcohols, particularly preferred solvent is water.
• the dispersion A) may also comprise further components such as surface-active substances, for example ionic and nonionic surfactants or adhesion promoters, such as organofunctional silanes or their silylates, for example 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3 Metacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane, crosslinkers such as melamine compounds, capped isocyanates, functional silanes - eg tetraethoxysilane, alkoxysilane hydrolysates, eg based on
• the dispersions A) contain further additives which increase the conductivity, e.g. ether group-containing compounds, e.g. Tetrahydrofuran, compounds containing lactone groups, such as ⁇ -butyrolactone, ⁇ -valerolactone, compounds containing amide or lactam groups, such as caprolactam, N-methylcaprolactam, N, N-dimethylacetamide, N-methylacetamide, N, N-dimethylformamide (DMF), N-methylformamide, N-methylformanilide, N-methylpyrrolidone (NMP), N-octylpyrrolidone, pyrrolidone, sulfones and sulfoxides, such as Sulfolane (tetramethylene sulfone), dimethyl sulfoxide (DMSO), sugars or sugar derivatives, such as e.g.
• ether group-containing compounds e.g. Tetrahydrofuran
• lactone groups such as
• Sucrose glucose, fructose, lactose, sugar alcohols, e.g. Sorbitol, mannitol, furan derivatives, e.g. 2-furancarboxylic acid, 3-furancarboxylic acid, and / or di- or polyalcohols, e.g. Ethylene glycol, glycerol, di- or triethylene glycol ,.
• conductivity-increasing additives tetrahydrofuran, N-methylformamide, N-methylpyrrolidone, ethylene glycol, dimethyl sulfoxide or sorbitol.
• the dispersions A) may also contain one or more organic solvents soluble organic binders such as polyvinyl acetate, polycarbonate, polyvinyl butyral, polyacrylic acid esters, polymethacrylic acid esters, polystyrene, polyacrylonitrile, polyvinyl chloride, polybutadiene, polyisoprene, polyethers, polyesters, silicones, styrene / acrylic ester, vinyl acetate / acrylic acid ester - And ethylene / vinyl acetate copolymers or water-soluble binders such as polyvinyl alcohols.
• organic solvents soluble organic binders such as polyvinyl acetate, polycarbonate, polyvinyl butyral, polyacrylic acid esters, polymethacrylic acid esters, polystyrene, polyacrylonitrile, polyvinyl chloride, polybutadiene, polyisoprene, polyethers, polyesters, silicones, styrene
• the dispersions A) may have a pH of 1 to 14, preferably a pH of 1 to 8.
• a pH of 1 to 8 For corrosion-sensitive dielectrics, such as, for example, aluminum oxides or niobium oxides, dispersions having a pH of from 4 to 8, are preferred Dielectric should not be damaged.
• bases or acids can be added to the dispersions.
• bases or acids Preference is given to those additives which do not impair the film formation of the dispersions and at higher temperatures, eg soldering temperatures, are not volatile, but remain under these conditions in the solid electrolyte, such as the bases 2-dimethylaminoethanol, 2,2'-iminodiethanol or 2,2 ', 2 "-Nitrilotriethanol and the acid polystyrene sulfonic acid.
• the viscosity of the dispersion A) can be s' 1), depending on the type of application between 0.1 and 500 mPa ⁇ s (measured at 20 0 C and a shear rate of 100th
• the viscosity is preferably from 1 to 200 mPa.s, more preferably from 1 to 100 mPa.s, most preferably from 3 to 50 mPa.s.
• Fig. 1 describes a schematic representation of the structure of a solid electrolytic capacitor using the example of a tantalum capacitor with
• FIG. 2 describes the enlarged image detail 10 from FIG. 1 of the schematic layer construction of the tantalum capacitor
• solid electrolyte (cathode) 5 optionally existing conductive outer layer
• such an electrolytic capacitor according to the invention can be manufactured as follows. pressed a valve metal powder having a high surface area and sintered into a porous electrode body.
• an electrical contact wire is preferably made of a valve metal such.
• metal foils may be etched to obtain a porous foil.
• the electrode body is then coated, for example by electrochemical oxidation, with a dielectric, ie an oxide layer.
• the oxidized electrode body is shown
• a dispersion A) containing at least particles B) of an electrically conductive polymer and a dispersing agent D) is then applied, and the dispersion medium D) is at least partially removed and / or cured to form the solid electrolyte.
• further layers in FIG. 1 and FIG. 2 with a conductive outer layer (5)) are applied to the outer surface of the capacitor body.
• a coating of highly conductive layers, such as graphite and silver, or a metallic cathode body serves as an electrode to dissipate the current.
• the capacitor is contacted and encapsulated.
• the electrode material is a valve metal or a connection with a valve metal comparable electrical properties.
• metal metals are understood to be metals whose oxide layers do not allow current flow in both directions equally: With anodically applied voltage, the oxide layers of the valve metals block the flow of current, while with cathodically applied voltage large currents occur which destroy the oxide layer can.
• the valve metals include Be, Mg, Al, Ge, Si, Sn, Sb, Bi, Ti, Zr, Hf, V, Nb, Ta and W, and an alloy or compound of at least one of these metals with other elements.
• the best known representatives of the valve metals are Al, Ta, and Nb.
• Compounds of valve metal comparable electrical properties are those with metallic conductivity, which are oxi- dierbar and whose oxide layers have the properties described above.
• NbO has metallic conductivity but is generally not considered a valve metal.
• layers of oxidized NbO have the typical properties of valve metal oxide layers such that NbO or an alloy or compound of NbO with other elements are typical examples of such compounds having valve metal comparable electrical properties.
• electrode materials of tantalum, aluminum and such electrode materials based on niobium or niobium oxide Preference is given to electrode materials of tantalum, aluminum and such electrode materials based on niobium or niobium oxide.
• Electrode materials based on niobium or niobium oxide are understood to mean those materials in which niobium or niobium oxide represent the component with the greatest molar fraction.
• the electrode material based on niobium or niobium oxide is preferably niobium, NbO, a niobium oxide NbO x , where x can assume values of 0.8 to 1.2, niobium nitride, nitro boxynitride or mixtures of these materials or in order an alloy or compound of at least one of these materials with other elements.
• Preferred alloys are alloys with at least one valve metal, such as Be, Mg, Al, Ge, Si, Sn, Sb, Bi, Ti, Zr, Hf, V, Nb, Ta or W.
• oxidizable metal means not only metals, but also an alloy or compound of a metal with other elements as long as they have metallic conductivity and are oxidizable.
• the oxidizable metals are sintered into a porous electrode body in powder form, or a porous structure is impressed on a metallic body.
• the latter can e.g. by etching a foil.
• the porous electrode bodies are used, for example, in a suitable electrolyte, e.g. Phosphoric acid, oxidized by applying a voltage.
• a suitable electrolyte e.g. Phosphoric acid
• the height of this forming voltage depends on the oxide layer thickness to be achieved or the subsequent application voltage of the capacitor.
• Preferred forming voltages are 1 to 300 V, more preferably 1 to 80 V.
• Specific charge (capacity * anodization voltage) / weight of the oxidized electrode body.
• the capacity results from the capacity of the oxidized electrode body measured at 120 Hz in an aqueous electrolyte.
• the electrical conductivity of the electrolyte is sufficiently large, so that it does not come at 120 Hz to a capacity drop due to the electrical resistance of the electrolyte.
• 18% strength aqueous sulfuric acid electrolytes are used for the measurement.
• the electrode bodies used have a porosity of 10 to 90%, preferably from 30 to 80%, particularly preferably from 50 to 80%.
• the porous electrode bodies have an average pore diameter of 10 to 10,000 nm, preferably 50 to 5,000 nm, particularly preferably 100 to 3,000 nm.
• the subject of the present invention is accordingly a process for the production of electrolytic capacitors, characterized in that, in the case of the valve or a compound of comparable electrical properties to tantalum, niobium, aluminum, titanium, zirconium, hafnium, vanadium, an alloy or combination of at least one of these metals with other elements, NbO or an alloy or compound of NbO with other elements.
• the dielectric preferably consists of an oxide of the electrode material. It optionally contains further elements and / or compounds.
• the capacity of the oxidized electrode body depends not only on the type of dielectric but also on the surface and the thickness of the dielectric.
• the specific charge is a measure of how much charge per unit weight the oxidized electrode body can accommodate. The specific charge is calculated as follows:
• Specific charge (capacity * rated voltage) / weight of the oxidized electrode body.
• the capacitance results from the capacitance of the finished capacitor measured at 120 Hz and the nominal voltage is the specified threshold voltage of the capacitor (rated voltage).
• the weight of the oxidized electrode body refers to the net weight of the dielectric-coated porous electrode material without polymer, contacts, and encapsulations.
• the electrolytic capacitors produced by the novel process preferably have a specific charge of 500 to 500,000 ⁇ C / g, particularly preferably with a specific charge of 2,000 to 150,000 ⁇ C / g, very particularly preferably with a specific charge of 2,000 to 100,000 ⁇ C / g preferably with a specific charge of 5000 to 50000 ⁇ C / g.
• Suitable precursors for the preparation of conductive polymers of the particles B) in the dispersion are corresponding monomers or derivatives thereof. It is also possible to use mixtures of different precursors.
• Suitable monomeric precursors are, for example, optionally substituted thiophenes, pyrroles or anilines, preferably optionally substituted thiophenes, particularly preferably optionally substituted 3,4-alkylenedioxythiophenes.
• substituted 3,4-alkylenedioxythiophenes are the compounds of the general formula (EI) or (TV) or a mixture of thiophenes of the general formulas (JH) and (IV) 5
• A represents an optionally substituted C 1 -C 5 -alkylene radical, preferably an optionally substituted C 2 -C 3 -alkylene radical,
• R is a linear or branched, optionally substituted CpCig-alkyl radical, preferably linear or branched, optionally C-substituted
• x is an integer from 0 to 8, preferably from 0 to 6, particularly preferably 0 or 1 and
• radicals R are attached to A, they may be the same or different,
• Very particularly preferred monomeric precursors are optionally substituted 3,4-ethylenedioxythiophenes.
• R and x have the meaning given for the general formulas (III) and (FV).
• derivatives of these monomeric precursors are, for example, dimers or trimers of these monomeric precursors. They are also higher molecular weight derivatives, i. Tetramers, pentamers, etc. of the monomeric precursors as derivatives possible.
• n is an integer from 2 to 20, preferably 2 to 6, particularly preferably 2 or 3,
• R and x have the meaning given for the general formulas (IH) and (TV).
• the derivatives can be constructed from the same or different monomer units and can be used in pure form and mixed with one another and / or with the monomer precursors. Oxidized or reduced forms of these precursors are also encompassed within the meaning of the invention by the term "precursors", provided that the same conductive polymers are formed during their polymerization as in the precursors listed above.
• radicals mentioned for the abovementioned precursors in particular for the thiophenes, preferably for the 3,4-alkylenedioxythiophenes, the radicals mentioned for the general formulas (Ol) and (FV) for R are suitable.
• Suitable substituents for pyrroles and anilines are, for example, the abovementioned radicals A and R and / or the further substituents of the radicals A and R in question.
• radicals A and / or the radicals R are the organic groups mentioned in connection with the general formulas (I) and (II).
• the 3,4-alkylene-oxythiathiophenes of the formula (III) required for the preparation of the polythiophenes to be used are known to the person skilled in the art or can be prepared by known processes (for example according to P. Blanchard, A. Cappon, E. Levillain, Y. Nicolas, P Frere and J. Roneali, Org. Lett., 4 (4), 2002, pp. 607-609).
• the dispersions are prepared from the precursors described above, for example analogously to the conditions mentioned in EP-A 440 957 (US Pat. No. 5,300,575).
• An improved variant for the preparation of the dispersions is the use of ion exchangers for removing the inorganic salt content or a part thereof. Such a variant is described, for example, in DE-A 19627071 (US Pat. No. 6,376,105).
• the ion exchanger can for example be stirred with the product or the product is conveyed through a column filled with ion exchange column. By using the ion exchanger, for example, the low metal contents described above can be achieved.
• the particle size of the particles B) in the dispersion A) can be reduced after desalting, for example by means of a high-pressure homogenizer. This process can also be repeated to increase the effect. Particularly high pressures between 100 and 2000 bar have proved to be advantageous in order to greatly reduce the particle size.
• a preparation of the polyaniline / polyanion or polythiophene / polyanion complex and subsequent dispersion or redispersion in one or more solvents is also possible.
• the solids content of the particles B) of the electrically conductive polymer in the dispersion A) is 0.1-90% by weight, preferably 0.5-30% by weight and very particularly preferably 0.5-10% by weight.
• the particles B) of the conductive polymer preferably form a stable dispersion.
• unstable dispersions in that they are stirred, rolled or shaken, for example, before use in order to ensure a uniform distribution of the particles B).
• the dispersions A) are applied to the dielectric of the electrode body by known methods, for example by spin coating, impregnation, pouring, dripping, spraying, spraying, knife coating, brushing or printing, for example ink-jet, screen or pad printing. - -
• the penetration of the dispersion into the porous electrode body can be facilitated for example by over or under pressure, vibration, ultrasound or heat.
• the application may be directly or using a coupling agent, for example a silane, e.g. organofunctional silanes or their hydrolysates, e.g. 3-Glycidoxy- propyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-MercaptopropyltrimethoxysiIan, 3-methacrylic oxypropyltrimethoxysilane, vinyltri-methoxysilane or octyltriethoxysilane, and / or one or more other functional layers carried on the dielectric of the electrode body.
• a silane e.g. organofunctional silanes or their hydrolysates, e.g. 3-Glycidoxy- propyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-MercaptopropyltrimethoxysiIan, 3-methacrylic oxypropyltrimethoxysilane, vinyltri-methoxy
• the dispersant D) is preferably removed so that the solid electrolyte can be formed from the particles B) and optionally further additives in the dispersion.
• the dispersant D) it is also possible for at least part of the dispersant D) to remain in the solid electrolyte. Depending on the nature of the dispersion medium D), it can also be cured completely as well as only the part remaining after partial removal.
• Removal of the dispersant D) after application of the dispersion can be carried out by simple evaporation at room temperature. To achieve higher processing speeds, however, it is more advantageous to remove the dispersants D) at elevated temperatures, for example at temperatures of 20 to 300 ° C., preferably 40 to 250 ° C.
• a thermal aftertreatment can be connected directly with the removal of the solvent or else at a time interval from the completion of the coating.
• the duration of the heat treatment is 5 seconds to several hours, depending on the type of dispersion used for the coating.
• For the thermal treatment and temperature profiles with different temperatures and Ve ⁇ veil profession can be used.
• the heat treatment may e.g. be carried out in such a way that one moves the coated oxidized electrode body at such a speed through a heat chamber at the desired temperature, that the desired residence time is reached at the selected temperature, or with a desired temperature at the desired heating plate for the desired residence time brings in contact.
• the heat treatment can be carried out, for example, in one or more heating furnaces, each with different temperatures.
• metal oxide dielectrics such as the oxides of the valve metals
• reforming immersed in the capacitor body in an electrolyte and applies a positive voltage to the electrode body.
• the flowing stream replenishes the oxide at defective points in the oxide film or destroys conductive polymer at defects over which a high current flows.
• oxidized electrode body it may be advantageous to impregnate the oxidized electrode body a further number of times with the dispersions in order to achieve thicker polymer layers and / or greater coverage of the dielectric surface.
• the application of the dispersion A) and the at least partial removal and / or curing of the dispersant D) takes place several times.
• a portion of the dispersion can be removed again from the oxidized electrode body, carried out a further impregnation with the same or a different dispersion, a rinse with the same or other solvents containing optionally additives or carried out storage.
• the particles B) of the conductive polymer which are located on the outer surface of the electrode body are at least partially, particularly preferably as far as possible removed.
• This can e.g. by rinsing, blotting, blowing, spin or the like.
• the use of, for example, ultrasound, heat or radiation to remove the outer polymer film is possible.
• Preference is given to rinsing with solvent, preferably with the solvent used as dispersing agent.
• the particles B) of the conductive polymer can also be removed from the outer surface of the electrode body after the at least partial removal and / or hardening of the dispersion medium D), for example by ultrasound, laser radiation, solvents or mechanical detachment.
• the coverage of the dielectric with the solid electrolyte can be determined as follows: The capacitance of the capacitor is measured in the dry and wet state at 120 Hz. The degree of coverage is the ratio of the capacity in the dry state to the capacity in the wet state expressed as a percentage. Dry state means that the condenser was dried for several hours at elevated temperature (80-120 0 C) before being measured. Wet condition means that the condenser is exposed to saturated air humidity at elevated pressure over several hours, for example in a steam pressure vessel. The moisture penetrates into pores that are not covered by the solid electrolyte, where it acts as a liquid electrolyte.
• the coverage of the dielectric by the solid electrolyte is preferably greater than 50%, more preferably greater than 70%, most preferably greater than 80%.
• a conductive outer layer After preparation of the solid electrolyte, further conductive layers, e.g. a conductive outer layer can be applied.
• a polymeric outer layer is preferably applied, for example as described in European Patent Application EP-A 1 524 678 (US Pat. No. 6,987,663).
• Other well-conductive layers such as graphite and / or silver layers serve as a current collector.
• the capacitor is contacted and encapsulated.
• the inventive method thus enables the production of solid electrolytic capacitors with low equivalent series resistance (ESR) and low residual current, where no in-situ polymerization is required, the dielectric is not damaged by metal ions and a thermally stable solid electrolyte is formed than in known methods.
• the inventive method also allows the production of polymer solid electrolytic capacitors whose electrode materials are based on niobium or niobium oxide and which have a low residual current and low ESR whose production by in-situ polymerization of the solid electrolyte was previously not possible.
• the electrolytic capacitors produced according to the invention are outstandingly suitable for use as components in electronic circuits, for example as a filter capacitor or decoupling capacitor.
• electronic circuits such as those in computers (desktop, laptop, server), in computer peripherals (eg PC cards), in portable electronic devices, such as mobile phones, digital cameras or consumer electronics, in consumer electronics devices, such as in CD / DVD players and computer game consoles, in navigation systems, in telecom- communication devices, in household appliances, in power supplies or in automotive electronics.
• the dispersion A) -I prepared in this way had the following particle size distribution:
• the diameter of the particles B) of the conductive polymer refers to a mass distribution of the particles B) in the dispersion as a function of the particle diameter. The determination was made by an ultracentrifuge measurement. The particle size was determined in the swollen state of the particles.
• the viscosity of the dispersion was 26 mPa * s at a shear rate of 100 Hz, and 2O 0 C.
• An ICP analysis of the metal content of the dispersion A) -I gave the following values:
• dispersion A) -I 100 g of the dispersion A) -I from Example 1 were added to 5 g of dimethylsulfoxide (DMSO) and stirred to give a dispersion A) -2.
• Tantalum powder having a specific capacity of 50,000 ⁇ FV / g was pressed into pellets including a tantalum wire 7 and sintered to form one having dimensions of 4.2 mm * 3 mm * 1 mm.
• the porous electrode bodies (2) had an average pore diameter of 580 nm and were anodized to 30 V to form a dielectric in a phosphoric acid electrolyte.
• dispersion A) -I 100 g of the dispersion A) -I from Example 1, 4 g of dimethylsulfoxide (DMSO) and 0.5 g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, OSi Specialties) were intensively mixed in a beaker with a stirrer to give a dispersion A) -3 mixed.
• DMSO dimethylsulfoxide
• Silquest A-187 3-glycidoxypropyltrimethoxysilane
• the PEDT / toluene sulphonate powder was filtered out on a porcelain suction filter, washed with 3 1 of demineralized water and getrock- net last 6 hours at 100 0 C. 89 g of a blue-black PEDT toluene sulphonate powder were obtained.
• This dispersion A) -5 obtained had a solids content of 4.7%.
• the condenser body from 3.2 were soaked in this dispersion A) -5 and then dried at 120 0 C for 10 min.
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A).
• the residual current was determined three minutes after applying a 10V voltage with a Keithley 199 multimeter.
• a dispersion was prepared analogously to Example 1, but without subsequent homogenization.
• the dispersion A) -6 prepared in this way had the following particle size distribution:
• dispersion A) -6 100 g of dispersion A) -6, 4 g of dimethyl sulfoxide (DMSO) and 0.5 g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, OSi Specialties) were mixed intensively in a beaker with stirrer to form a dispersion A) -7.
• DMSO dimethyl sulfoxide
• Silquest A-187 3-glycidoxypropyltrimethoxysilane
• the 9 manufactured capacitors had on average the following electrical values:
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A). The residual current was determined three minutes after applying a 10V voltage with a Keithley 199 multimeter. The capacitance of these capacitors is only about 3% of the capacitance in Example 3. It can be concluded that the conductive particles from the dispersion A) -7 in the comparative example do not penetrate sufficiently into the pores of the electrode body, although the average particle diameter (147 nm ) is significantly smaller than the mean pore diameter (580 nm) of the electrode body.
• Electrode bodies were prepared analogously to Example 3.1. These electrode bodies were provided with a solid electrolyte by means of a chemical in situ polymerization.
• the solution was used to impregnate the 18 anodized electrode body 2.
• the E- lektroden stresses 2 were steeped in this solution and subsequently dried for 30 min at room temperature (20 0 C). They were then is 30 min at 50 0 C in a drying cabinet ebenbe-.
• the electrode bodies were washed in a 2 wt% aqueous solution of p-toluenesulfonic acid for 60 minutes.
• the electrode bodies were reformed for 30 minutes in a 0.25% by weight aqueous solution of p-toluenesulfonic acid, then rinsed in distilled water and dried.
• the described impregnation, drying, temperature treatment and reforming was carried out with the same electrode bodies two more times.
• the capacitor bodies were provided analogously to Example 3.3 with a polymeric outer layer. Finally, the electrode bodies were coated with a graphite and silver layer.
• the 18 manufactured capacitors had on average the following electrical values:
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A).
• the residual current was determined three minutes after applying a 10V voltage with a Keithley 199 multimeter.
• the process according to the invention (Example 3) achieves equal capacities and ESR values.
• the erf ⁇ ndungshiele process for the formation of the solid electrolyte takes only 2h, requires no chemical reaction and is based on aqueous dispersions.
• the chemical in situ process lasts approx. 9 h and explosive solutions must be handled.
• not all iron salts can be removed in the ih-situ process. In contrast to the virtually metal-free process according to the invention, this leads to a significantly higher residual current in the comparative example.
• Tantalum powder having a specific capacity of 150,000 ⁇ FV / g was pressed into pellets including a tantalum wire 7 and sintered to form one having dimensions of 1.7 mm ⁇ 1.1 mm ⁇ 1.1 mm.
• the porous electrode bodies 2 had an average pore diameter of 190 nm and were anodized to 12 V to form a dielectric in a phosphoric acid electrolyte.
• dispersion A) -I from Example 1 100 g of the dispersion A) -I from Example 1, 4 g of dimethyl sulfoxide (DMSO) and 0.5 g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, OSi Specialties) were intensively mixed in a beaker with a stirrer to give a dispersion A). 8 mixed.
• DMSO dimethyl sulfoxide
• Silquest A-187 3-glycidoxypropyltrimethoxysilane
• the oxidized electrode bodies were soaked in this dispersion A) -8 for 1 min. Subsequently, the soaked electrode bodies were rinsed under running water to remove the dispersion A) -8 on the outside of the electrode body. This was followed by drying at 12O 0 C for 10 min. Soaking, rinsing and drying were carried out nine more times.
• a 2 l three-necked flask with stirrer and internal thermometer is charged with 868 g of deionized water, 330 g of an aqueous polystyrenesulphonic acid solution having an average molecular weight of 70,000 and a solids content of 3.8% by weight.
• the reaction temperature was maintained between 20 and 25 0 C.
• the condenser bodies were soaked in this dispersion A) -9 and then dried at 120 ° C. for 10 minutes. Soaking and drying was repeated once more.
• the electrode bodies were coated with a graphite and silver layer.
• the 9 manufactured capacitors had on average the following electrical values:
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A).
• the residual current was determined three minutes after applying a 4V voltage with a Keithley 199 Multimeter.
• anodized porous aluminum foils of size 4 mm * 4 mm were soaked in this dispersion for 1 min. Subsequently, the soaked electrode bodies were rinsed under running water to remove the dispersion on the outside of the electrode body. This was followed by drying at 120 0 C for 10 min. Soaking, rinsing and drying were carried out nine more times.
• the 9 manufactured capacitors had on average the following electrical values:
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A).
• the residual current was determined three minutes after applying a 6.3V voltage with a Keithley 199 multimeter.
• Niobium oxide powder having a specific capacity of 80,000 ⁇ FV / g was pressed into pellets including tantalum wire 7 and sintered to form one having dimensions of 5 mm * 3.5 mm * 1 mm.
• the porous electrode bodies 2 were anodized to 30 V to form a dielectric in a phosphoric acid electrolyte.
• the oxidized electrode bodies were soaked in dispersion A) -3 from Example 3.2 for 1 min. Subsequently, the soaked electrode bodies were rinsed under running water to remove the dispersion A) -3 on the outside of the electrode body. This was followed by drying at 120 0 C for 10 min. Soaking, rinsing and drying were carried out nine more times.
• the condenser body from 3.2 were soaked in this dispersion A) -5 from Example 3.3 and then dried at 12O 0 C for 10 min. Impregnation and drying were carried out a second time.
• the electrode bodies were coated with a graphite and silver layer and aged at a voltage of 15 V for 1 h.
• the 18 manufactured capacitors had on average the following electrical values:
• the capacitance was determined at 120 Hz and the equivalent series resistance (ESR) at 100 kHz by means of an LCR meter (Agilent 4284A) at a bias voltage of 10V.
• the residual current was determined three minutes after applying a 10 V voltage with a Keithley 199 multimeter.
• Electrode bodies were prepared analogously to Example 6.1. These electrode bodies were provided with a solid electrolyte by means of a chemical in situ polymerization.
• the solution was used to impregnate the anodized electrode bodies 2.
• the electrode body 2 were soaked in this solution and then dried for 30 min at room temperature (20 0 C). Thereafter, they were heat-treated at 50 ° C. for 30 minutes in a drying oven. Subsequently, the electrode bodies were washed in a 2 wt% aqueous solution of p-toluic acid for 60 minutes. The electrode bodies were reformed for 30 minutes in a 0.25% by weight aqueous solution of p-toluenesulfonic acid, then rinsed in distilled water and dried. The described impregnation, drying, temperature treatment and reforming was carried out with the same electrode bodies two more times.
• the capacitor bodies were provided analogously to Example 6.3 with a polymeric outer layer.
• the electrode bodies were coated with a graphite and silver layer and aged at a voltage of 15 V for 1 h.

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