WO2008007126A1 - Improvements in the production of electrolytic capacitor - Google Patents
Improvements in the production of electrolytic capacitor Download PDFInfo
- Publication number
- WO2008007126A1 WO2008007126A1 PCT/GB2007/002660 GB2007002660W WO2008007126A1 WO 2008007126 A1 WO2008007126 A1 WO 2008007126A1 GB 2007002660 W GB2007002660 W GB 2007002660W WO 2008007126 A1 WO2008007126 A1 WO 2008007126A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- anode
- electro
- deoxidation
- metal
- dielectric layer
- Prior art date
Links
- 239000003990 capacitor Substances 0.000 title claims abstract description 39
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 65
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000001301 oxygen Substances 0.000 claims abstract description 51
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 51
- 239000003792 electrolyte Substances 0.000 claims abstract description 33
- 229910052751 metal Inorganic materials 0.000 claims abstract description 30
- 239000002184 metal Substances 0.000 claims abstract description 30
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 22
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000002243 precursor Substances 0.000 claims abstract description 18
- 150000003839 salts Chemical class 0.000 claims abstract description 17
- 229910052715 tantalum Inorganic materials 0.000 claims abstract description 17
- 229910001092 metal group alloy Inorganic materials 0.000 claims abstract description 14
- 239000007787 solid Substances 0.000 claims abstract description 10
- 238000000151 deposition Methods 0.000 claims abstract description 9
- 238000005406 washing Methods 0.000 claims abstract description 5
- 230000008569 process Effects 0.000 claims description 26
- 238000012545 processing Methods 0.000 claims description 14
- 238000002048 anodisation reaction Methods 0.000 claims description 10
- 238000005245 sintering Methods 0.000 claims description 7
- 239000004411 aluminium Substances 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 238000004806 packaging method and process Methods 0.000 claims description 5
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 238000004663 powder metallurgy Methods 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- 238000010923 batch production Methods 0.000 claims 4
- 230000008021 deposition Effects 0.000 claims 2
- 238000007743 anodising Methods 0.000 claims 1
- 238000011065 in-situ storage Methods 0.000 claims 1
- 239000010410 layer Substances 0.000 description 35
- 230000008901 benefit Effects 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 7
- 150000002739 metals Chemical class 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 6
- 238000009792 diffusion process Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 238000011109 contamination Methods 0.000 description 3
- 238000002161 passivation Methods 0.000 description 3
- 238000009700 powder processing Methods 0.000 description 3
- 239000007858 starting material Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical class [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical class [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910001362 Ta alloys Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000001668 ameliorated effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000010407 anodic oxide Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical class [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical class [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Chemical class 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 1
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical class [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 230000003685 thermal hair damage Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052727 yttrium Chemical class 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical class [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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
- H01G9/004—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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/10—Obtaining titanium, zirconium or hafnium
- C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
- C22B34/129—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds by dissociation, e.g. thermic dissociation of titanium tetraiodide, or by electrolysis or with the use of an electric arc
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/20—Obtaining niobium, tantalum or vanadium
- C22B34/24—Obtaining niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/20—Automatic control or regulation of cells
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
- C25D17/10—Electrodes, e.g. composition, counter electrode
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/66—Electroplating: Baths therefor from melts
-
- 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
- H01G9/07—Dielectric layers
Definitions
- the present invention relates to an improved method for the production of electrolytic capacitors, especially solid electrolytic capacitors, and to the products of such methods.
- the invention relates, in particular, to the production of tantalum capacitors with improved performance characteristics.
- an electrolytic capacitor In the initial manufacture of an electrolytic capacitor, a very thin film of oxide is deposited onto the surface of a suitable anode metal, for example aluminium, tantalum or niobium, by passage of an electric current, so as to produce an insulating or dielectric layer. After the dielectric layer has been formed, a conducting layer, cathode layer and packaging layer are added, in turn, to the precursor anode body, to form the end capacitor product.
- a commonly used conducting layer in solid electrolytic capacitors is manganese dioxide.
- a liquid conducting layer is used.
- the cathode typically comprises deposited graphite and silver layers.
- electrolytic capacitors over other capacitor designs is their high capacitance rating, resulting from the thinness of the dielectric layer and its large surface area, coupled with the anodic oxide having a reasonably high dielectric constant.
- the dielectric properties of tantalum pentoxide are particularly suitable for use in electrolytic capacitors. Components based on tantalum have significant benefits for circuit design, due to their volumetric efficiency and reliability, and are widely used in the electronics industry in products such as mobile phones, pagers and laptops.
- the performance of electrolytic capacitors can be degraded by impurities present in the metal anode body.
- high levels of oxygen can cause defects in the dielectric layer during oxide growth, leading to an undesirably high leakage current in the end capacitor product.
- This leads to a reduction in the capacitance and/or voltage rating of the end capacitor product, and, as a consequence, worse volumetric efficiency.
- JP 11111575 A for example, a porous anode body of tantalum is sintered in the presence of carbon and magnesium and then subjected to acid-cleaning, to attain a low-oxygen-concentration anode for use in a solid electrolytic capacitor.
- methods proposed to date suffer various problems, notably inherent disadvantages associated with the deoxidation step. Examples of said disadvantages are: residues from leaching processes which affect the dielectric coating, softening of the support wire, and poor anode surface properties.
- a method for the production of a precursor anode for an electrolytic capacitor comprising the steps of:
- anode body from a suitable anode metal or metal alloy
- the present invention provides a convenient way of removing undesired surface and/or bulk oxygen from metallic anode bodies, which process is especially suitable for industrial-scale batch processing.
- the method is applicable to all anode metals or metal alloys that form oxide layers with suitable dielectric properties. Only a few metals form dense, stable, tightly adhering, electrically insulative oxides, which metals include aluminium, titanium, zirconium, niobium, tantalum and hafnium (the so-called "valve metals"). Tantalum, in particular, has been found to withstand the present processing conditions without undue damage or contamination.
- a benefit of the process of the present invention is that the volumetric efficiency of the end capacitor product is increased, therefore it is possible that the invention may render viable the use of more expensive metals or metal alloys that are currently uneconomic. Another benefit of increased volumetric efficiency is that smaller capacitors may be produced, leading to a higher packing density of components.
- metals and metal alloys containing dissolved oxygen can be deoxidised by electrolysis in a fused salt electrolyte.
- a metal or metal alloy containing dissolved, interstitial oxygen is made into the cathode of an electrolysis cell, or otherwise put in contact with a cathode.
- the cell contains a fused-salt electrolyte and the cathode and an anode contact the electrolyte.
- a cell voltage is applied between the cathode and the anode, the voltage being such that the cathode potential is sufficient to remove oxygen from the cathode.
- the applied cell voltage is such that the cathode potential is sufficient to remove oxygen from the cathode but is not sufficient to cause cations in the electrolyte to deposit as metal at the cathode.
- the applied cell voltage may also be controlled so as to avoid decomposition of the fused salt electrolyte.
- This method may be used to remove oxygen from solid metals or alloys, or to remove oxygen from solid metal compounds or semi-metal compounds.
- the latter aspect is described for example in WO 99/64638 of Fray et al. Both aspects may be applicable to the deoxidation of anode bodies, for example to remove oxygen dissolved in the metal of an anode body or to remove oxygen from a surface passivation layer of metal oxide.
- the present process can be applied to anode bodies made by any of the usual routes, for example, by metal foil, etched foil, sputtered film or powder processing routes.
- the latter route involving powder compaction, followed by sintering, leads to the formation of porous anode bodies with high surface areas.
- tantalum powder is first mixed with a resin binder and mechanically pressed into pellets of a controlled density. Each pellet is then pressed onto a fine tantalum or tantalum alloy wire to form an anode preform or 'slug'.
- the anode preforms are piled into trays and heated under vacuum, in order to burn out the resin binder.
- the 'green' anodes are sintered at high temperature to impart full strength, whilst retaining a porosity of, typically, 50%.
- the electro-deoxidation step can be used to deoxidise the anode body at any stage in its manufacturing process prior to anodisation.
- the electro-deoxidation step is advantageously carried out as the last step prior to forming the dielectric layer.
- the green anodes are formed by a powder processing route, because the sintering step results in oxygen diffusion from the outer protective passivation layer into the bulk tantalum. This results in an increase in the bulk oxygen level, and, in a typical situation, bulk oxygen can increase from around 2800ppm to around 6000ppm.
- the anode body is preferably deoxidised after the sintering step so that the bulk oxygen level can be reduced.
- the process of the present invention is effective in significantly reducing dissolved, interstitial oxygen from the bulk metal or metal alloy, unlike some prior art surface deoxidation methods. This improves the quality of the subsequently formed dielectric layer, leading to a lower risk of short circuits and improved end capacitor performance.
- Ta metal containing interstitial oxygen retains its mechanical integrity after electro-deoxidation, permitting further processing of the anode bodies. This not only allows the manufacturer to take advantage of the increased mechanical strength imparted by the sintering process, but enables the bulk oxygen level to be reduced prior to anodisation.
- a further advantage of the present invention is that it enables a less hazardous, higher bulk oxygen Ta (or other metal or alloy) powder to be used as a starting material, because electro-deoxidation allows such interstitial oxygen to be removed without damaging the integrity of the anode body.
- Ta powder with an oxygen level in excess of 6000ppm or IOOOOppm or 14000ppm may be used as a starting material.
- formation of the dielectric layer, by anodisation is carried out on batches of anode bodies.
- sintered anode bodies are welded, in batches, to aluminium strips at a tightly controlled pitch and length so that the bottom of all anodes are at the same distance from the aluminium strip.
- One or more strips are then loaded into a supporting frame, which frame is then transferred to an anodisation vessel for formation of the dielectric layer.
- the anodisation process is carefully controlled to give a uniform and complete oxide thickness over the external and internal surfaces of the anode. The temperatures used at this stage are below those required for secondary bulk diffusion of oxygen.
- the present invention takes advantage of existing processing methods and a plurality of anode bodies is deoxidised as a batch.
- the plurality of anode bodies is fixed to an electrically-conducting support prior to electro-deoxidation, such as a metal strip.
- the support should be suitable for use in the electro-deoxidation cell.
- the metal strip comprises a corrosion resistant metal or alloy with a melting point greater than the temperature of the electrolysis cell, for example steel.
- a plurality of supports are mounted into a racking system; by processing the anode bodies in supporting racks or frames, handling is made easier.
- the conducting support is made the cathode of the electrolysis cell, for example by bringing an electrical brush connector into contact with the support or racking system.
- the frames and/or metal strips are suitable for later use in the anodisation vessel.
- the anode body is fully covered with electrolyte, but the contact wire is only partially immersed.
- components required for later processing such as a polymeric insulator for cathode isolation, to be loaded onto the contact wire prior to fixing the anodes to the support, without necessarily introducing those components into the electrolyte.
- possible softening of the contact wire upon electro- deoxidation may be ameliorated.
- a batch of anode bodies is held in a basket during electro-deoxidation and the basket is made the cathode of the electrolysis cell. More preferably, the anode bodies are agitated during electrolysis, in order to make sure that all anode bodies are brought into electrical contact with the cathode.
- the anode bodies are made the cathode of the electrolysis cell, or held in electrical contact with a cathode, and the cell voltage is set at a suitable level for an electro-deoxidation process to take place. This level is sufficient that oxygen is removed from the cathode, but is preferably also below the voltage at which chlorine is evolved from the electrolyte.
- the anode of the electrolysis cell comprises carbon.
- the temperature of the electrolysis cell should be maintained at 500-1200 0 C, or preferably 700-1000 0 C, throughout the electrolysis, thereby aiding diffusion processes. However, localised cooling or heating of certain regions of the cell, for example the racking system, may be required.
- the cell voltage for a small-scale cell may lie in the range 1.4V to 3.2V. In larger cells higher cell voltages may be required to overcome losses such as IR losses and maintain the cathode potential at a desired level.
- the electrolyte should comprise a fused salt, or mixture of salts, which is more stable than the equivalent salt of the metal or metal alloy that is being deoxidised.
- the salt, or mixture of salts preferably has a wide difference between its melting and boiling point and a high temperature of operation to improve the diffusion of oxygen and other species in the capacitor anode body and elsewhere.
- Suitable electrolytes include the chlorides or other salts of barium, calcium, caesium, lithium, strontium and yttrium. CaCI 2 is particularly suitable as an electrolyte. In order to optimise the deoxidation process, a suitable concentration of oxide ions in the electrolyte is also desirable, to ensure continuous oxygen transport from the cathode to the anode.
- the electro-deoxidation process is applied until the desired oxygen level has been reached. Typically, this will be after 24 to 48 hours, but depends on the batch size.
- electrolysis is conducted until the oxygen level is below 14000ppm, IOOOOppm or 6000ppm, or is below 3000ppm, more preferably below 2000ppm and even more preferably below lOOOppm.
- An anode body manufactured by a powder metallurgy route is particularly suitable for use in an electro-deoxidation process, due to its high porosity.
- the electrolyte must be fully washed from the deoxidised anode bodies, using a suitable solvent such as water, in order to remove any contamination prior to forming the dielectric.
- a suitable solvent such as water
- methods comprising pressure leaching or agitation may be used to improve the penetration of porous anode bodies with the solvent.
- the electrolyte may be distilled from the anode bodies, or a combined washing and distillation method may be used.
- electro-deoxidation steps are preferably taken to ensure that atmospheric oxygen is not picked up by the anode bodies, particularly while the bodies are at a high temperature.
- One method of doing this is to control the atmosphere, for example by processing in an inert atmosphere such as argon, or by processing the anodes under vacuum.
- the final step in the production of the precursor anodes is to anodise the deoxidised anode bodies to form the dielectric layer.
- anodisation is by means of electrolysis in a weak acid.
- the dielectric layer may advantageously be formed on the anode body surface without exposing the anode body to oxygen after the electro-deoxidation process.
- This step has the advantage that the electro-deoxidation process may reduce the bulk oxygen concentration in the anode body to a low level, and the low level of oxygen may then be retained in the precursor anode after formation of the dielectric layer and in the final capacitor product, and may lead to improved capacitor performance.
- this step may be achieved by operating the electro-decomposition cell until the bulk oxygen content in the anode body, at the cathode of the cell, is less than a predetermined level, such as 14000ppm, lOOOOppm, ⁇ OOOppm or even 2000ppm, IOOOppm or 750ppm.
- a predetermined level such as 14000ppm, lOOOOppm, ⁇ OOOppm or even 2000ppm, IOOOppm or 750ppm.
- the polarity of the cell is reversed so that the anode body is connected as the anode of the cell. This has the effect of oxidising the anode body under controlled conditions, through control of the anode potential, in order to form the oxide dielectric layer on the anode body surface.
- the dielectric layer can be formed directly on the low-bulk oxygen-content anode body, for example eliminating any need to wash the electro- decomposition cell electrolyte out of the anode body before the dielectric layer is formed in a separate process.
- the low bulk oxygen content may be retained.
- Controlling the anode potential and the length of time of application of the reverse polarity in the electro-decomposition cell may advantageously allow precise control of the dielectric layer thickness, and may improve not only the capacitance of the end capacitor product but also leakage currents.
- the temperature of the cell may be changed from a preferred electro- deoxidation temperature to a preferred dielectric formation temperature.
- the electro-decomposition potential at the cathode should be maintained while, for example, the cell temperature is varied, in order to maintain the low bulk oxygen content of the anode body.
- the precursor anode may be removed from the electrolyte and washed, as described above, before further processing. Since the dielectric layer has been formed, the anode body is then protected from further oxidation, for example due to exposure to the atmosphere.
- the end capacitor product is produced by adding, in succession, a conducting layer, a cathode layer and a packaging layer.
- the conducting layer is typically formed by dipping the precursor anodes into manganese nitrate solution, which may then be thermally decomposed to manganese Oxides' until complete coverage of the dielectric is achieved.
- the outside layer of the manganesed anode may be coated with graphite and then a silver-loaded resin, which forms the cathodic connection to the manganese and an external electrical contact.
- the anode may be attached to a contact frame and encapsulated in resin before test.
- test stages There may be a number of test stages in between each of the above steps and also some processes to repair thermal damage to the dielectric.
- Another aspect of the invention provides a precursor anode produced by the process described above.
- a further aspect of the invention provides a final capacitor product comprising an anode obtained by the process described above.
- Yet another aspect of the invention provides a dielectric capacitor comprising an anode, a dielectric layer, a conducting medium, a cathode and packaging, wherein the oxygen level in the anode is below 3000ppm, preferably below 2000ppm and more preferably below lOOOppm.
- a batch of sixteen sintered, tantalum anode bodies were welded to a stainless steel strip and electrically connected to the cathode of an electro-deoxidation cell.
- the tantalum anode bodies were electrolysed at a cell temperature of 950 0 C for 24 hours at 3.0V, using a calcium chloride electrolyte, a carbon anode and an inert atmosphere.
- the anode batch was removed from the cell, it was found that the anode bodies had held together mechanically and thus, were capable of further processing to form capacitors.
- a sintered, tantalum anode body was processed under the conditions described in Example 1 by electrolysis in the electro-deoxidation cell. After the electro-deoxidation process, however, before removal of the anode body from the electrolyte, the cell polarity was reversed. During this process the anode body was electrolysed for 20 minutes at 3.0V to form a dielectric oxide layer on its surface. The anode body/anode precursor was then removed from the cell and washed, before further processing to form a capacitor. In a modification of this Example, the temperature of the electro-decomposition electrolyte may be reduced from 95O 0 C for the anodisation step.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Electrochemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Electrolytic Production Of Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
MX2009000488A MX2009000488A (en) | 2006-07-13 | 2007-07-13 | Improvements in the production of electrolytic capacitor. |
JP2009518969A JP2009543369A (en) | 2006-07-13 | 2007-07-13 | Improvements in the production of electrolytic capacitors |
EP07766232A EP2052395A1 (en) | 2006-07-13 | 2007-07-13 | Improvements in the production of electrolytic capacitor |
IL196457A IL196457A0 (en) | 2006-07-13 | 2009-01-12 | Improvements in the production of electrolytic capacitor |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0613984.4 | 2006-07-13 | ||
GBGB0613984.4A GB0613984D0 (en) | 2006-07-13 | 2006-07-13 | Improvements in the production of electrolytic capacitors |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2008007126A1 true WO2008007126A1 (en) | 2008-01-17 |
Family
ID=36955636
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2007/002660 WO2008007126A1 (en) | 2006-07-13 | 2007-07-13 | Improvements in the production of electrolytic capacitor |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP2052395A1 (en) |
JP (1) | JP2009543369A (en) |
KR (1) | KR20090031462A (en) |
CN (1) | CN101501798A (en) |
GB (1) | GB0613984D0 (en) |
IL (1) | IL196457A0 (en) |
MX (1) | MX2009000488A (en) |
RU (1) | RU2009101296A (en) |
WO (1) | WO2008007126A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010146369A1 (en) * | 2009-06-18 | 2010-12-23 | Metalysis Limited | Feedstock |
US9926636B2 (en) | 2012-12-24 | 2018-03-27 | Metalysis Limited | Method and apparatus for producing metal by electrolytic reduction |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006027612A2 (en) * | 2004-09-09 | 2006-03-16 | Cambridge Enterprise Limited | Improved electro-deoxidation method, apparatus and product |
WO2006057455A1 (en) * | 2004-11-29 | 2006-06-01 | Showa Denko K.K. | Porous anode body for solid electrolytic capacitor, production mehtod thereof and solid electrolytic capacitor |
-
2006
- 2006-07-13 GB GBGB0613984.4A patent/GB0613984D0/en not_active Ceased
-
2007
- 2007-07-13 KR KR1020097002991A patent/KR20090031462A/en not_active Application Discontinuation
- 2007-07-13 RU RU2009101296/07A patent/RU2009101296A/en not_active Application Discontinuation
- 2007-07-13 JP JP2009518969A patent/JP2009543369A/en not_active Withdrawn
- 2007-07-13 MX MX2009000488A patent/MX2009000488A/en unknown
- 2007-07-13 WO PCT/GB2007/002660 patent/WO2008007126A1/en active Application Filing
- 2007-07-13 EP EP07766232A patent/EP2052395A1/en not_active Withdrawn
- 2007-07-13 CN CNA2007800301416A patent/CN101501798A/en active Pending
-
2009
- 2009-01-12 IL IL196457A patent/IL196457A0/en unknown
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006027612A2 (en) * | 2004-09-09 | 2006-03-16 | Cambridge Enterprise Limited | Improved electro-deoxidation method, apparatus and product |
WO2006057455A1 (en) * | 2004-11-29 | 2006-06-01 | Showa Denko K.K. | Porous anode body for solid electrolytic capacitor, production mehtod thereof and solid electrolytic capacitor |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010146369A1 (en) * | 2009-06-18 | 2010-12-23 | Metalysis Limited | Feedstock |
CN102459710A (en) * | 2009-06-18 | 2012-05-16 | 金属电解有限公司 | Feedstock |
CN102459710B (en) * | 2009-06-18 | 2016-07-20 | 金属电解有限公司 | Raw material |
EA023858B1 (en) * | 2009-06-18 | 2016-07-29 | Металисиз Лимитед | Feedstock |
US9926636B2 (en) | 2012-12-24 | 2018-03-27 | Metalysis Limited | Method and apparatus for producing metal by electrolytic reduction |
Also Published As
Publication number | Publication date |
---|---|
RU2009101296A (en) | 2010-08-20 |
IL196457A0 (en) | 2009-09-22 |
JP2009543369A (en) | 2009-12-03 |
EP2052395A1 (en) | 2009-04-29 |
KR20090031462A (en) | 2009-03-25 |
GB0613984D0 (en) | 2006-08-23 |
CN101501798A (en) | 2009-08-05 |
MX2009000488A (en) | 2009-05-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8349030B1 (en) | Method for making anodes for high voltage electrolytic capacitors with high volumetric efficiency and stable D.C. leakage | |
EP2935656B1 (en) | Method and apparatus for producing metal by electrolytic reduction | |
EP1527834B1 (en) | Niobium andniobium nitride powder mixtures for electrolytic capacitors substrates | |
Vishnu et al. | A study of the reaction pathways during electrochemical reduction of dense Nb2O5 pellets in molten CaCl2 medium | |
WO2000075943A1 (en) | Electrode material for capacitor and capacitor using the same | |
WO2001029291A1 (en) | Method of anodizing tantalum powder | |
WO2010092358A1 (en) | A method for producing metal powders | |
WO2002049965A1 (en) | Method of forming titanium oxide film and titanium electrolytic capacitor | |
WO2008007126A1 (en) | Improvements in the production of electrolytic capacitor | |
SU1057995A1 (en) | Process for manufacturing body-porous anode of electrolytic capacitor | |
GB2534332A (en) | Method and apparatus for producing metallic tantalum by electrolytic reduction of a feedstock | |
US9607770B2 (en) | Method for producing capacitor | |
JP3958343B2 (en) | Method for forming oxide dielectric layer and capacitor layer forming material having oxide dielectric layer obtained by the method | |
TWI470660B (en) | Method for manufacturing electrode structure body, electrode structure body and capacitor | |
JP2006328531A5 (en) | ||
WO2011013375A1 (en) | Manufacturing method for solid electrolytic capacitor | |
US3239436A (en) | Method of making titanium electrolytic capacitors | |
KR20160065277A (en) | Electrolytic reduction apparatus for metal oxide using conductive oxide ceramic anode and method thereof | |
JP2007305780A (en) | Metallic porous-foil anode body and its manufacturing method | |
JPH028446B2 (en) | ||
WO2008041007A1 (en) | A method and apparatus for producing metal powders | |
KR102255478B1 (en) | Method of controlling impurity of indium metal by electrolytic refining of molten salt | |
US20080105084A1 (en) | Method of production of tantalum powder with low impurity level | |
RU2516525C1 (en) | Method for production of cathode lining for solid-electrolyte capacitor | |
KR101723919B1 (en) | Electrolytic reduction apparatus for metal oxide using conductive oxide ceramic anode and method thereof |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 200780030141.6 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 07766232 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2009518969 Country of ref document: JP Ref document number: MX/A/2009/000488 Country of ref document: MX |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2007766232 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 2009101296 Country of ref document: RU Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 1020097002991 Country of ref document: KR |