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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/045—Alloys based on refractory metals
  • C22C1/0458—Alloys based on titanium, zirconium or hafnium
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/10—Other heavy metals
  • C23G1/106—Other heavy metals refractory metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/26—Anodisation of refractory metals or alloys based thereon
• • 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
  • H01G9/004—Details
  • H01G9/04—Electrodes or formation of dielectric layers thereon
  • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
  • H01G9/0425—Electrodes or formation of dielectric layers thereon characterised by the material specially adapted for cathode
• • 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
  • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
  • H01G9/052—Sintered electrodes
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/43—Electric condenser making
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/43—Electric condenser making
  • Y10T29/435—Solid dielectric type

Definitions

• the present invention relates to a method of producing a solid electrolytic capacitor.
• capacitors of this kind comprise a sintered body consisting of the metals tantalum or niobium serving as the anode. On a dielectric layer of this metal there is provided a semiconducting layer consisting of manganese dioxide serving to act as a solid electrolyte for carrying the metallic cathode layer.
• Capacitors with a sintered body of titanium have not yet been manufactured in this form.
• the reason for this is presumably to be seen in the fact that the metal of titanium cannot be produced with the necessary purity and, on the other hand, in the fact that the titanium oxides TiO or Ti O respectively, are conductive and, therefore, disturb the construction of a suitable blocking layer (barrier layer) when employing the conventional forming methods.
• a suitable blocking layer barrier layer
• the phesent invention provides a Way of producing a solid electrolytic titanium capacitor.
• the invention itself is based on the application of a suitable temperature treatment, forming and contacting process in order to build up the necessary stacking structure on a sintered body of titanium powder.
• titanium powder having a purity degree of only 99.4%, although an increased purity degree will also improve the electrical properties.
• the sintering of the titanium powder is appropriately carried out in a high vacuum, at a temperature ranging between 1200 and 1400 C.
• the titanium powder shall have a grain size of -100
• a very suitable sintering temperature is considered to be at 1300 C., with a sintering period of about 30 to 60 minutes.
• the values of both the capacitances and the residual current may be changed by varying the sintering time.
• the lead-in wire extending to the sintered body As a material for the lead-in wire extending to the sintered body, it is proposed to use titanium of a purity as high as possible. It has proved favorable to sinter the titanium wire into the body when producing the sintered body, so that the freely projecting end can be used as the lead-in wire.
• the superficial oxide film which would otherwise have a disturbing effect during the further process.
• This can be accomplished by etching the sintered body, e.g., with the aid of a diluted solution of hydrofluoric acid.
• the removal of the.oxide film can be regarded as being completed as soonas there appears a strong formation of gas bubbles indicating that now the titanium metal itself is being attacked.
• the etching of ice the titanium not only causes an enlargement of the capacitance of the sintered body, but also cleans or purifies the surface thereof.
• the success of the etching process can be proved in particular when comparing the residual current measurements of etched and unetched sintered bodies.
• the sintered body must be carefully washed, in order to remove all traces of fluor.
• the use or employment of an ultrasonic cleansing has proved to be very useful in this respect.
• a good result, however, is also obtainable when subjecting the sintered body to a repeated boiling in purest water. In no case is the wash-water allowed to have a milky opacity.
• the etched and washed sintered bodies are dried and put for sometime, at least for several hours, into an aqueous oxidizing solution at room temperature.
• a mixture of e.g. one part concentrated nitric acid and one part of a 30% hydrogen peroxide has proved to be favorable.
• the oxidizing treatment serves the purpose of converting conductive foreign metal particles in the sintered body, such as particles of iron or silicon, into non-conducting oxides. This leads to a reduction of the residual current of the future capacitor.
• an oxidizing temperature treatment at a temperature of about 400-500 C., which in air must last for several hours.
• pure oxygen if the time of treatment is to be reduced to about 15-30 minutes, and if there is to be avoided the formation of conductive titanium nitrides.
• the sintered body which hitherto had a metallically grey appearance is provided with a tarnish decolorization quite depending on the kind and duration of treatment.
• the sintered body will have a yellow appearance, at a higher temperature a brown appearance, and thereafter a bluish-violet appearance, then grey, and finally a white appearance.
• the bluish-violet color is to be preferred.
• the thus pre-treated sintered bodies are now subjected to various forming processes under electric voltages.
• a forming in the solution of an aqueous electrolyte having a good conductivity e.g., an acid solution, atabout 20 C., to about 20 volts or higher.
• the second forming process in a mixture of several salts at a temperature of about 350 C.
• a salt melt consisting of sodium, potassium, and lithium salts.
• the following composition was used:
• the sintered body is ready for a layer of semiconducting material to be deposited on the thus produced dielectric layer.
• the sintered body in vacuo, is saturated, eg, with a mixture consisting of -a manganese nitrate solution and manganese hydroxide.
• a mixture consisting of -a manganese nitrate solution and manganese hydroxide.
• Such a mixture will be obtained when adding or mixing an aqueous acid manganese-nitrate solution -to or with a solution of ammonia until a sufficient amount of manganese hydroxide exists in the solution.
• a temperature of 200 C. has proved to be most favorable.
• MnO cracks are easily caused to appear in the oxide layer, which have to be healed. According to the invention this may be accomplished by the action of an alkaline reacting aqueous electrolyte.
• the semiconducting layer consequently the MnO -layer, is preferably produced in partial layers, and each time between the formation of two such layers there is carried out a heating of the defects by subjecting them to a forming process in the above-mentioned electrolyte.
• the secured capacitance of la cylindric sintered body such as described above with a diameter of 3.2 millimeters and a length of 11 millimeters containing 0.2 gram of titanium is 30 microfarads after forming treatment at 40 volts.
• the maximum working voltage is 35 volts.
• the electrode system produced in this way is now provided with a graphite coating serving as the base or support for a solderable metal coating to which a lead-in wire may be soldered.
• a process for manntacturing a capacitor having a titanium body as one electrode comprising the steps of:
• a process according to claim 1 further comprising the step of converting any foreign metal particles present on the surfiace of said body into non-conducting oxides before performing said heating step.
• lithium nitnate in the relative proportions of approxim-ately 138:10lzl0l by weight.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacturing & Machinery (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Treatment Of Metals (AREA)
• Fixed Capacitors And Capacitor Manufacturing Machines (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (9)

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Citations (5)

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• 0
  • GB GB1054613D patent/GB1054613A/en not_active Expired
• 1963
  • 1963-05-31 DE DEST20672A patent/DE1220937B/de active Pending
• 1964
  • 1964-05-26 US US370330A patent/US3279030A/en not_active Expired - Lifetime
  • 1964-05-28 CH CH695864A patent/CH447384A/de unknown
  • 1964-05-29 NL NL6406035A patent/NL6406035A/xx unknown
  • 1964-06-01 BE BE648663D patent/BE648663A/xx unknown

Patent Citations (5)

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