US20080265220A1 - Process for Producing Capacitors - Google Patents
Process for Producing Capacitors Download PDFInfo
- Publication number
- US20080265220A1 US20080265220A1 US12/145,972 US14597208A US2008265220A1 US 20080265220 A1 US20080265220 A1 US 20080265220A1 US 14597208 A US14597208 A US 14597208A US 2008265220 A1 US2008265220 A1 US 2008265220A1
- Authority
- US
- United States
- Prior art keywords
- powder
- niobium
- anode
- nbo
- suboxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000003990 capacitor Substances 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title abstract description 16
- 230000008569 process Effects 0.000 title abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 84
- 239000010955 niobium Substances 0.000 claims abstract description 54
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 48
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 48
- 239000000203 mixture Substances 0.000 claims abstract description 31
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 229910052751 metal Inorganic materials 0.000 claims description 38
- 239000002184 metal Substances 0.000 claims description 38
- 239000002245 particle Substances 0.000 claims description 13
- 239000011164 primary particle Substances 0.000 claims description 13
- 239000007784 solid electrolyte Substances 0.000 claims description 8
- 239000011163 secondary particle Substances 0.000 claims description 4
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 abstract description 14
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 abstract description 13
- 239000012212 insulator Substances 0.000 abstract description 3
- 238000005245 sintering Methods 0.000 description 30
- 238000002156 mixing Methods 0.000 description 14
- 238000005054 agglomeration Methods 0.000 description 13
- 230000002776 aggregation Effects 0.000 description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 11
- 239000001301 oxygen Substances 0.000 description 11
- 229910052760 oxygen Inorganic materials 0.000 description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 10
- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 238000003801 milling Methods 0.000 description 9
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 8
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 8
- 239000012298 atmosphere Substances 0.000 description 6
- HFLAMWCKUFHSAZ-UHFFFAOYSA-N niobium dioxide Inorganic materials O=[Nb]=O HFLAMWCKUFHSAZ-UHFFFAOYSA-N 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000002923 metal particle Substances 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
- 238000012216 screening Methods 0.000 description 4
- 229910052715 tantalum Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000007858 starting material Substances 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- ZYTNDGXGVOZJBT-UHFFFAOYSA-N niobium Chemical compound [Nb].[Nb].[Nb] ZYTNDGXGVOZJBT-UHFFFAOYSA-N 0.000 description 2
- 229910000484 niobium oxide Inorganic materials 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
- 239000011148 porous material 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
- 239000000080 wetting agent Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000013101 initial test Methods 0.000 description 1
- 239000012705 liquid precursor Substances 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 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
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000013528 metallic particle Substances 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- WTKKCYNZRWIVKL-UHFFFAOYSA-N tantalum Chemical compound [Ta+5] WTKKCYNZRWIVKL-UHFFFAOYSA-N 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- H01G9/004—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
- H01G9/004—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
- H01G9/0525—Powder therefor
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
- C22C29/12—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on oxides
-
- 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
Definitions
- the invention relates to a process for producing capacitors based on niobium suboxide with an insulator layer of niobium pentoxide, to a powder mixture suitable for production of capacitors, to pressed bodies produced from the powder mixture and to capacitors having specific properties.
- niobium suboxide is to be understood as meaning compounds of the formula NbO z where z ⁇ 2.2 and preferably 0.5 ⁇ z ⁇ 2.2.
- Solid electrolyte capacitors with a very large active capacitor surface area and therefore a small overall size that is suitable for mobile communications electronics used are predominantly those with a niobium or tantalum pentoxide barrier layer applied to a corresponding conductive support, utilizing the stability of these compounds (“valve metal”), the relatively high dielectric constant and the fact that the insulating pentoxide layer can be produced electrochemically with a very uniform layer thickness.
- Metallic or conductive lower oxidic (suboxide) precursors of the corresponding pentoxides are used as carriers.
- the support which simultaneously forms a capacitor electrode (anode), comprises a highly porous, sponge-like structure which is produced by sintering extremely fine particulate primary structures or secondary structures which are already in sponge-like form.
- the surface of the support structure is electrolytically oxidized (“formed”) to give the pentoxide, with the thickness of the pentoxide layer being determined by the maximum voltage used for the electrolytic oxidation (“forming voltage”).
- the counterelectrode is produced by impregnating the sponge-like structure with manganese nitrate, which is thermally converted into manganese dioxide, or with a liquid precursor of a polymer electrolyte and polymerization.
- the electrical contacts to the electrodes are formed on one side by a tantalum or niobium wire sintered in during production of the support structure and the metallic capacitor casing, which is insulated from the wire.
- the capacitance C of a capacitor is calculated using the following formula:
- NbO x Niobium suboxide
- niobium suboxide as support body for capacitor barrier layers is that a sufficient compressive strength of the sintered anode body and a sufficient wire tensile strength are only achieved by sintering the pressed bodies at a relatively high sintering temperature (in the region of 1450° C. compared to 1150° C. in the case of Nb metal).
- the high sintering temperature leads firstly, as a result of increased surface diffusion, to a decrease in the surface area of the pressed body during transition to the sintered body, and therefore to a lower capacitance, and secondly requires increased levels of energy and increased loading being applied to the materials of the crucibles and sintering furnaces.
- niobium suboxide by comparison with niobium metal with metallic ductility, already has considerable covalent bond levels, which produce in relative terms a ceramic brittleness.
- the compressive strength of the anode bodies prior to sintering leaves something to be desired, since the porous powder agglomerates do not stably “mesh together” during pressing, but rather have an increased tendency to disintegrate or abrade, with the result that not only is the formation of stable sintered bridges impeded, but also agglomerates in a more finely particulate form, even down to isolated primary particles, are formed, causing an adverse change in the pore structure of the sintered anode body.
- niobium oxide powders also have worse flow properties than metal powders, making it more difficult to meter the powders into the press tools.
- Another object of the invention is to provide a powder for the production of capacitor anodes based on niobium suboxides which can be sintered at a relatively low sintering temperature.
- the subject matter of the invention is a process for producing capacitor anodes based on niobium suboxide by pressing suitable starting materials in powder form to form powder preforms and sintering the powder preforms to give porous anode bodies, which is characterized in that the pulverulent starting material used is a powder mixture of niobium suboxide powder and valve metal powder.
- Niobium and/or tantalum metal powder preferably niobium metal powder, can be used as valve metal powder.
- Both the niobium suboxide powders and the niobium metal powders are used in the form of the agglomerates of primary particles which are customary for capacitor production.
- the primary particles have the standard minimum linear dimensions of 0.4 to 2 ⁇ m.
- the agglomerates have particle sizes with a Mastersizer D 50 value (ASTM B 822) of 30 to 200 ⁇ m, preferably 120 to 180 ⁇ m.
- the niobium suboxide powder used is preferably a powder of formula NbO x where x ⁇ 2.1, particularly preferably where 0.7 ⁇ x ⁇ 2.
- the oxygen content of the starting oxide (“x” in the above formula) and the relative quantities of niobium suboxide and niobium metal are selected as a function of the desired procedure and the desired product (capacitor). It is desirable for niobium oxide that is present in the support structure of the capacitor (the anode) to have the composition NbO y where 0.7 ⁇ y ⁇ 1.3, preferably 0.9 ⁇ y ⁇ 1.15 . particularly preferably 1.0 ⁇ y ⁇ 1.05 .
- the anode may consist entirely of NbO y . However, the anode may also have geometric regions which consist of niobium metal or very slightly oxidized niobium metal.
- a niobium suboxide powder of the preferred composition NbO y is mixed intensively with a niobium metal powder, and the mixture is then introduced into a press mould around a niobium or tantalum contact wire in a manner known per se, pressed to a green density of 2.3 to 3.7 g/cm 3 and then sintered under high vacuum to form anodes.
- the pressed bodies have a high sintering activity, on the one hand on account of the presence of niobium metal, which has a higher sintering activity, but on the other hand also on account of oxygen exchange at the contact locations between metal and oxide (“reaction sintering”).
- reaction sintering sintering temperatures of from 1150 to 1300° C. are sufficient, i.e. the process according to the invention allows sintering temperatures which are lower by 150 to 250° C. to be used.
- Niobium metal powder and niobium suboxide powder can be used in any desired quantitative ratio relative to one another, although the effect of the invention disappears at extreme quantitative ratios.
- a quantitative ratio of from 0.1 to 2 (by weight) is preferred, with from 0.1 to 0.8 being particularly preferred and 0.2 to 0.4 being even more preferred.
- the particle size distribution may (given an approximately equal primary particle size) be selected to be similar.
- metal powder and suboxide powder are preferably used in approximately equal quantitative ratios, for example approximately with a ratio in the range from 40:60 to 60:40.
- the agglomerate particle size of the metal particles is preferably smaller than that of the suboxide particles.
- the D50 value (according to Mastersizer, ASTM B 822, wetting agent Daxad 11) of the metal particles may be between 20 and 40 ⁇ m, whereas the D50 value of the suboxide particles may be between 130 and 190 ⁇ m.
- the metal powder it is preferable for the metal powder to be used in subordinate quantities by comparison with the suboxide powder, preferably with a ratio in the range from 9:91 to 20:80.
- the suboxide and metal powder agglomerate are intensively mixed, if appropriate with milling, preferably together, and are then agglomerated, so that agglomerate powders which include both oxidic and metallic regions are formed.
- the agglomeration preferably takes place at temperatures between 850 and 1200° C. in an inert, preferably argon, atmosphere, so that there is no oxygen exchange between the oxidic and metallic particles apart from at the direct locations of contact through solid-state diffusion.
- Preferred and particularly preferred suboxide powders are selected according to the same rules as in the first embodiment of the invention.
- a starting suboxide NbO x where x is slightly above 1 is particularly preferred.
- the powders After the milling, preferably together, the powders have a preferred particle size distribution which is characterized by a D50 value of from 20 to 50 ⁇ m.
- the D90 value should preferably be less than 90 ⁇ m.
- the powders After the agglomeration, which may if appropriate be repeated a number of times, the powders should have a preferred particle size distribution which is characterized by a D10 value of from 50 to 90 ⁇ m, a D50 value of from 150 to 190 ⁇ m and a D90 value of from 250 to 290 ⁇ m.
- the relative quantitative ratios of suboxide and metal particles may preferably be selected on the basis of same criteria as in the first embodiment of the invention. It is preferable first of all to produce a mixture of suboxide powder and some of the metal powder, to agglomerate this mixture, then to admit a further part of the metal powder, followed by milling of this mixture then a further agglomeration step.
- the powders are then pressed together with a niobium or tantalum wire to form anode bodies and sintered.
- the sintering may be carried out under high vacuum, producing anode structures which include both oxidic and metallic regions.
- the powder mixture is filled into press moulds, surrounding a contact wire made from niobium or tantalum, pressed to a green density of 2.3 to 3.7 g/cm 3 and sintered to form anode structures.
- the sintering of the anode pressed bodies to form the anode body is carried out in a hydrogen-containing atmosphere, in such a way that oxygen exchange between the suboxide and metal particles also takes place via the gas phase (intermediate formation of water vapour molecules at the oxide surfaces and reduction of these molecules at the metal surfaces) of the agglomerates.
- an atmosphere with a relatively low hydrogen partial pressure to be used during the sintering, in order to ensure that there is no hydrogen embrittlement of the metallic component, in particular of the niobium or tantalum wire. It is preferable for the sintering to be carried out under a gas pressure of from 10 to 50 mbar absolute. If appropriate, post-sintering can be carried out under high vacuum.
- reaction sintering During the sintering with oxygen equalization (“reaction sintering”), the volume of the metallic starting agglomerates increases and the volume of the oxidic starting agglomerates decreases. If a starting oxide of the approximate formula NbO 2 is used, the total volume during oxygen equalization to form NbO remains approximately constant. Competing changes in length and volume during sintering therefore only occur in the near region and are absorbed by the near region shifts which are in any case caused by the sintering process.
- anode bodies are formed with a substantially homogenous oxide composition of formula NbO y with y as defined above.
- agglomerates (tertiary particles) are produced, including both metallic primary particles and/or secondary particles and oxidic primary and/or secondary particles within a particles composite (tertiary agglomerate particle).
- the sintering of the pressed anode structures is carried out in the same way as in the third embodiment of the invention, i.e. in the presence of hydrogen, resulting in an anode structure having a substantially homogenous composition corresponding to the formula NbO y where 0.7 ⁇ y ⁇ 1.3, preferably 0.9 ⁇ y ⁇ 1.15, particularly preferably 1 ⁇ y ⁇ 1.05.
- All four embodiments of the invention exploit the increased sintering activity of the anode pressed bodies through reaction sintering. This allows a considerable reduction in the sintering temperature and/or the sintering time. Both the anode pressed bodies and the sintered anode structures have an increased compressive strength. The anchoring of the contact wire to the anode sintered body is also improved. The anodes have an increased wire detachment strength under tension.
- niobium pentoxide which is commercially available with a high purity and to mix it with high-purity niobium metal, both in powder form corresponding to the stoichiometry, and to treat the mixture for several hours at a temperature of 800 to 1600° C. under an argon atmosphere which preferably contains up to 10% by volume of hydrogen. It is preferable for both the pentoxide and the metal to have primary particle sizes which, after the oxygen equalization, corresponds to the desired primary particle size of less than or slightly greater than 1 ⁇ m (smallest) cross-sectional dimension.
- the niobium metal required for oxygen exchange with niobium pentoxide is preferably produced by reducing high-purity niobium pentoxide to the metal. This can be effected aluminothermically by igniting an Nb 2 O 5 /Al mixture and washing out the aluminum oxide formed and then purifying the niobium metal ingot by means of electron beams.
- the niobium metal ingot obtained after reduction and electron beam melting can be embrittled using hydrogen in a known way and milled, producing plateletlike powders.
- the preferred process for producing the niobium metal follows the disclosure of WO 00/67936 A1.
- the high-purity niobium pentoxide powder is firstly reduced by means of hydrogen at 1000 to 1600° C., preferably at 1450° C., to form the niobium dioxide of approximate formula NbO 2 , and then the latter is reduced using magnesium vapour at 750 to 1100° C. to form the metal.
- Magnesium oxide which is formed in the process is washed out by means of acids.
- the preferred process for producing the niobium suboxide of formula NbO x where 1.3 ⁇ x ⁇ 2.1, preferably 1.8 ⁇ x ⁇ 2.1, particularly preferably 1.9 ⁇ x ⁇ 2, is carried out in accordance with the first stage of the process disclosed in WO 00167936 A1, i.e. by reducing the niobium pentoxide by means of hydrogen at 1000 to 1600° C.
- Powder 0 The niobium pentoxide powder is reduced to NbO 2 at 1250° C. under flowing hydrogen.
- Powder A The niobium pentoxide powder is reduced to form NbO2 at 1480° C. under flowing hydrogen, milled and rubbed through a screen with a mesh width of 300 ⁇ m.
- Powder B Powder 0 is reduced to the niobium metal by means of magnesium vapour at a temperature of 980° C., milled, agglomerated in vacuo at 1150° C., cooled, passivated by gradual admission of oxygen and rubbed through a screen with a mesh width of 300 ⁇ m.
- Powder C Powder A and powder B are mixed in a molar ratio of 1:1, gently milled, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen and rubbed through a screen with a mesh width of 300 ⁇ m.
- Powder D Powder A and powder B are mixed in a molar ratio of 1:0.8, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen, and then rubbed through a screen with a mesh width of 300 ⁇ m.
- Powder E Powder A and powder B are mixed in a molar ratio of 1:0.7, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen and then rubbed through a screen with a mesh width of 300 ⁇ m.
- Table 1 gives the properties (mean values) for the powders obtained.
- powder preforms were produced from the powders by introducing them into suitable press tools, into which a contact wire made from tantalum had been placed, and pressing to a green density of 2.8 g/cm 3 , and these powder preforms, standing freely in a furnace, were sintered at the temperature indicated either under a pressure of 10 ⁇ 5 bar (vacuum) or at standard pressure in the atmosphere indicated.
- the anode structures were then formed in 0.1% by weight strength phosphoric acid up to a forming voltage of 30 V at a current intensity limited to 150 mA/g, with the voltage being maintained for over 2 h after the current intensity had dropped to 0.
- the cathode used was an 18% by weight strength sulphuric acid solution, and the measurement was carried out at a bias voltage of 10 V and an AC voltage with a frequency of 120 Hz.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Powder Metallurgy (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
The invention relates to a process for producing capacitors based on niobium suboxide, and having an insulator layer of niobium pentoxide. Also described is a powder mixture suitable for production of capacitors. Pressed bodies produced from the powder mixture, and capacitors having specific properties are also disclosed.
Description
- The present patent application claims the right of priority under 35 U.S.C. § 119 (a)-(d) of German Patent Application No. 103 33 155.7, filed Jul. 22, 2003.
- 1. Field of the Invention
- The invention relates to a process for producing capacitors based on niobium suboxide with an insulator layer of niobium pentoxide, to a powder mixture suitable for production of capacitors, to pressed bodies produced from the powder mixture and to capacitors having specific properties.
- 2. Background of the Invention
- In the context of the present invention, the term niobium suboxide is to be understood as meaning compounds of the formula NbOz where z<2.2 and preferably 0.5<z<2.2.
- Solid electrolyte capacitors with a very large active capacitor surface area and therefore a small overall size that is suitable for mobile communications electronics used are predominantly those with a niobium or tantalum pentoxide barrier layer applied to a corresponding conductive support, utilizing the stability of these compounds (“valve metal”), the relatively high dielectric constant and the fact that the insulating pentoxide layer can be produced electrochemically with a very uniform layer thickness. Metallic or conductive lower oxidic (suboxide) precursors of the corresponding pentoxides are used as carriers. The support, which simultaneously forms a capacitor electrode (anode), comprises a highly porous, sponge-like structure which is produced by sintering extremely fine particulate primary structures or secondary structures which are already in sponge-like form. The surface of the support structure is electrolytically oxidized (“formed”) to give the pentoxide, with the thickness of the pentoxide layer being determined by the maximum voltage used for the electrolytic oxidation (“forming voltage”). The counterelectrode is produced by impregnating the sponge-like structure with manganese nitrate, which is thermally converted into manganese dioxide, or with a liquid precursor of a polymer electrolyte and polymerization. The electrical contacts to the electrodes are formed on one side by a tantalum or niobium wire sintered in during production of the support structure and the metallic capacitor casing, which is insulated from the wire.
- The capacitance C of a capacitor is calculated using the following formula:
-
C=(F·ε)/(d·VF) - where F is the capacitor surface area, s is the dielectric constant, d is the thickness of the insulator layer per V of forming voltage and VF is the forming voltage. Since the dielectric constant ε is 27.6 for tantalum pentoxide and 41 for niobium pentoxide, but the growth in layer thickness per volt of forming voltage d is 16.6 and 25 Å/V respectively, both pentoxides have virtually the same quotient ε/d=1.64 and 1.69 respectively. Capacitors based on both pentoxides, with the same geometry of the anode structures, therefore have the same capacitance. Differences encountered in details of specific weight-related capacitances are trivial, resulting from the different densities of Nb, NbOx and Ta. Therefore, anode structures made from Nb and NbOx have the advantage of saving weight when used, for example, in mobile telephones, which strive for every single gram of weight saved. For cost reasons, NbOx (Niobium suboxide) is more favourable than Nb, since part of the volume of the anode structure is formed by oxygen.
- One drawback of niobium suboxide as support body for capacitor barrier layers is that a sufficient compressive strength of the sintered anode body and a sufficient wire tensile strength are only achieved by sintering the pressed bodies at a relatively high sintering temperature (in the region of 1450° C. compared to 1150° C. in the case of Nb metal). The high sintering temperature leads firstly, as a result of increased surface diffusion, to a decrease in the surface area of the pressed body during transition to the sintered body, and therefore to a lower capacitance, and secondly requires increased levels of energy and increased loading being applied to the materials of the crucibles and sintering furnaces.
- The reason is that niobium suboxide, by comparison with niobium metal with metallic ductility, already has considerable covalent bond levels, which produce in relative terms a ceramic brittleness.
- Furthermore, the compressive strength of the anode bodies prior to sintering leaves something to be desired, since the porous powder agglomerates do not stably “mesh together” during pressing, but rather have an increased tendency to disintegrate or abrade, with the result that not only is the formation of stable sintered bridges impeded, but also agglomerates in a more finely particulate form, even down to isolated primary particles, are formed, causing an adverse change in the pore structure of the sintered anode body. Furthermore, there is increased wear to the press tools be comparison with metal powders. By no means least, niobium oxide powders also have worse flow properties than metal powders, making it more difficult to meter the powders into the press tools.
- According to WO 01/71738 A2, therefore, it is attempted to relieve the magnitude of these drawbacks by on the one hand adding lubricants and binders during pressing of the powders, which are intended to compensate for the drawback of insufficient compressive strength of the pressed bodies, and on the other hand by using more finely particulate agglomerates of primary particles, which are less likely to fracture, but this is to the detriment of the pore structure.
- It is an object of the present invention to avoid the drawbacks in capacitor production which are caused by the brittleness of niobium suboxide.
- Accordingly, it is an object of the invention to improve the flow properties of the powders during production of niobium suboxide anodes.
- Furthermore, it is an object of the invention to provide a powder for producing capacitor. anodes based on niobium suboxides which can be pressed to form pressed bodies with a high compressive strength.
- Another object of the invention is to provide a powder for the production of capacitor anodes based on niobium suboxides which can be sintered at a relatively low sintering temperature.
- Furthermore, it is an object of the invention to provide anodes for capacitors based on niobium suboxide with an increased compressive strength of the sintered body.
- Not least, it is a further object of the invention to reduce the number of steps required to produce capacitors based on niobium suboxide and thereby on the one hand to contribute to reducing costs and on the other hand to reduce the risk of contamination with impurities which have an adverse effect on the capacitor properties, in particular with regard to the residual current.
- It has been discovered that these and further objects can be achieved by virtue of powder mixtures of niobium suboxide and niobium metal and/or tantalum metal being used as starting material for the production of the pressed and sintered bodies.
- Accordingly, the subject matter of the invention is a process for producing capacitor anodes based on niobium suboxide by pressing suitable starting materials in powder form to form powder preforms and sintering the powder preforms to give porous anode bodies, which is characterized in that the pulverulent starting material used is a powder mixture of niobium suboxide powder and valve metal powder.
- Niobium and/or tantalum metal powder, preferably niobium metal powder, can be used as valve metal powder.
- Both the niobium suboxide powders and the niobium metal powders are used in the form of the agglomerates of primary particles which are customary for capacitor production. The primary particles have the standard minimum linear dimensions of 0.4 to 2 μm. The agglomerates have particle sizes with a Mastersizer D50 value (ASTM B 822) of 30 to 200 μm, preferably 120 to 180 μm.
- The niobium suboxide powder used is preferably a powder of formula NbOx where x<2.1, particularly preferably where 0.7<x<2.
- The oxygen content of the starting oxide (“x” in the above formula) and the relative quantities of niobium suboxide and niobium metal are selected as a function of the desired procedure and the desired product (capacitor). It is desirable for niobium oxide that is present in the support structure of the capacitor (the anode) to have the composition NbOy where 0.7<y<1.3, preferably 0.9<y<1.15 . particularly preferably 1.0<y<1.05 . The anode may consist entirely of NbOy. However, the anode may also have geometric regions which consist of niobium metal or very slightly oxidized niobium metal.
- According to a first embodiment of the invention, a niobium suboxide powder of the preferred composition NbOy, with y as defined above, is mixed intensively with a niobium metal powder, and the mixture is then introduced into a press mould around a niobium or tantalum contact wire in a manner known per se, pressed to a green density of 2.3 to 3.7 g/cm3 and then sintered under high vacuum to form anodes.
- The pressed bodies have a high sintering activity, on the one hand on account of the presence of niobium metal, which has a higher sintering activity, but on the other hand also on account of oxygen exchange at the contact locations between metal and oxide (“reaction sintering”). According to the invention, therefore, sintering temperatures of from 1150 to 1300° C. are sufficient, i.e. the process according to the invention allows sintering temperatures which are lower by 150 to 250° C. to be used.
- Niobium metal powder and niobium suboxide powder can be used in any desired quantitative ratio relative to one another, although the effect of the invention disappears at extreme quantitative ratios. A quantitative ratio of from 0.1 to 2 (by weight) is preferred, with from 0.1 to 0.8 being particularly preferred and 0.2 to 0.4 being even more preferred.
- The particle size distribution may (given an approximately equal primary particle size) be selected to be similar. In this case, metal powder and suboxide powder are preferably used in approximately equal quantitative ratios, for example approximately with a ratio in the range from 40:60 to 60:40.
- It is preferably for the agglomerate particle size of the metal particles to be smaller than that of the suboxide particles. By way of example, the D50 value (according to Mastersizer, ASTM B 822, wetting agent Daxad 11) of the metal particles may be between 20 and 40 μm, whereas the D50 value of the suboxide particles may be between 130 and 190 μm. In this case, it is preferable for the metal powder to be used in subordinate quantities by comparison with the suboxide powder, preferably with a ratio in the range from 9:91 to 20:80.
- According to a second embodiment of the invention, the suboxide and metal powder agglomerate are intensively mixed, if appropriate with milling, preferably together, and are then agglomerated, so that agglomerate powders which include both oxidic and metallic regions are formed. The agglomeration preferably takes place at temperatures between 850 and 1200° C. in an inert, preferably argon, atmosphere, so that there is no oxygen exchange between the oxidic and metallic particles apart from at the direct locations of contact through solid-state diffusion. Preferred and particularly preferred suboxide powders are selected according to the same rules as in the first embodiment of the invention. A starting suboxide NbOx where x is slightly above 1 is particularly preferred.
- After the milling, preferably together, the powders have a preferred particle size distribution which is characterized by a D50 value of from 20 to 50 μm. The D90 value should preferably be less than 90 μm. After the agglomeration, which may if appropriate be repeated a number of times, the powders should have a preferred particle size distribution which is characterized by a D10 value of from 50 to 90 μm, a D50 value of from 150 to 190 μm and a D90 value of from 250 to 290 μm.
- It has been found that in particular if the agglomeration treatment is repeated at least twice, with a milling operation in between, the desired formation of sintering bridges between suboxide and metal powder particles is promoted, since the intermediate milling preferentially breaks up oxide-oxide sintered bridges which have just formed during the preceding agglomeration step.
- The relative quantitative ratios of suboxide and metal particles may preferably be selected on the basis of same criteria as in the first embodiment of the invention. It is preferable first of all to produce a mixture of suboxide powder and some of the metal powder, to agglomerate this mixture, then to admit a further part of the metal powder, followed by milling of this mixture then a further agglomeration step.
- The powders are then pressed together with a niobium or tantalum wire to form anode bodies and sintered. The sintering may be carried out under high vacuum, producing anode structures which include both oxidic and metallic regions.
- According to a third embodiment of the invention, a suboxide powder of composition NbOx where 1.3<x<2.1, preferably 1.8<x<2.1, particularly preferably 1.9<x<2, is mixed with a quantity of a metal powder which is such that a mean composition of the mixture which corresponds to the formula NbOy where 0.7<y<1.3, preferably 0.9<y<1.15, particularly preferably 1<y<1.05, results.
- The powder mixture is filled into press moulds, surrounding a contact wire made from niobium or tantalum, pressed to a green density of 2.3 to 3.7 g/cm3 and sintered to form anode structures.
- According to this third embodiment of the invention, however, the sintering of the anode pressed bodies to form the anode body is carried out in a hydrogen-containing atmosphere, in such a way that oxygen exchange between the suboxide and metal particles also takes place via the gas phase (intermediate formation of water vapour molecules at the oxide surfaces and reduction of these molecules at the metal surfaces) of the agglomerates.
- In this third embodiment of the invention, it is preferable for an atmosphere with a relatively low hydrogen partial pressure to be used during the sintering, in order to ensure that there is no hydrogen embrittlement of the metallic component, in particular of the niobium or tantalum wire. It is preferable for the sintering to be carried out under a gas pressure of from 10 to 50 mbar absolute. If appropriate, post-sintering can be carried out under high vacuum.
- During the sintering with oxygen equalization (“reaction sintering”), the volume of the metallic starting agglomerates increases and the volume of the oxidic starting agglomerates decreases. If a starting oxide of the approximate formula NbO2 is used, the total volume during oxygen equalization to form NbO remains approximately constant. Competing changes in length and volume during sintering therefore only occur in the near region and are absorbed by the near region shifts which are in any case caused by the sintering process.
- According to this third embodiment of the invention, anode bodies are formed with a substantially homogenous oxide composition of formula NbOy with y as defined above.
- According to a fourth embodiment of the invention, firstly, as in the second embodiment of the invention, agglomerates (tertiary particles) are produced, including both metallic primary particles and/or secondary particles and oxidic primary and/or secondary particles within a particles composite (tertiary agglomerate particle).
- According to this fourth embodiment of the invention, a suboxide powder of composition NbOx where 1 .3<x<2.1, preferably 1 .8<x<2.1, particularly preferably 1.9<x<2, is mixed with a quantity of a metal powder which is such that a mean composition of the mixture which corresponds to the formula NbOy where 0.7<y<1.3, preferably 0.9<y<1.15, particularly preferably 1<y<1.05, results.
- According to this fourth embodiment of the invention, the sintering of the pressed anode structures is carried out in the same way as in the third embodiment of the invention, i.e. in the presence of hydrogen, resulting in an anode structure having a substantially homogenous composition corresponding to the formula NbOy where 0.7<y<1.3, preferably 0.9<y<1.15, particularly preferably 1<y<1.05.
- All four embodiments of the invention exploit the increased sintering activity of the anode pressed bodies through reaction sintering. This allows a considerable reduction in the sintering temperature and/or the sintering time. Both the anode pressed bodies and the sintered anode structures have an increased compressive strength. The anchoring of the contact wire to the anode sintered body is also improved. The anodes have an increased wire detachment strength under tension.
- Production of the suboxide powders that can be used in accordance with the invention does not present any particular difficulty for the person skilled in the art. It is preferable to use the standard metallurgical reaction and alloying process, according to which, as in the present case, a mean oxide content is produced by exposing a highly oxidized precursor and an unoxidized precursor, in a non-oxidizing, preferably reducing atmosphere, to a temperature at which oxygen concentration equalization takes place. Although processes other than this solid-state diffusion process are conceivable, they require control and monitoring functions which can scarcely be achieved in technical terms at acceptable levels of outlay. Therefore, according to the invention it is preferable to use a niobium pentoxide which is commercially available with a high purity and to mix it with high-purity niobium metal, both in powder form corresponding to the stoichiometry, and to treat the mixture for several hours at a temperature of 800 to 1600° C. under an argon atmosphere which preferably contains up to 10% by volume of hydrogen. It is preferable for both the pentoxide and the metal to have primary particle sizes which, after the oxygen equalization, corresponds to the desired primary particle size of less than or slightly greater than 1 μm (smallest) cross-sectional dimension.
- The niobium metal required for oxygen exchange with niobium pentoxide is preferably produced by reducing high-purity niobium pentoxide to the metal. This can be effected aluminothermically by igniting an Nb2O5/Al mixture and washing out the aluminum oxide formed and then purifying the niobium metal ingot by means of electron beams. The niobium metal ingot obtained after reduction and electron beam melting can be embrittled using hydrogen in a known way and milled, producing plateletlike powders.
- The preferred process for producing the niobium metal follows the disclosure of WO 00/67936 A1. According to this preferred 2-stage process, the high-purity niobium pentoxide powder is firstly reduced by means of hydrogen at 1000 to 1600° C., preferably at 1450° C., to form the niobium dioxide of approximate formula NbO2, and then the latter is reduced using magnesium vapour at 750 to 1100° C. to form the metal. Magnesium oxide which is formed in the process is washed out by means of acids.
- The preferred process for producing the niobium suboxide of formula NbOx where 1.3<x<2.1, preferably 1.8<x<2.1, particularly preferably 1.9<x<2, is carried out in accordance with the first stage of the process disclosed in WO 00167936 A1, i.e. by reducing the niobium pentoxide by means of hydrogen at 1000 to 1600° C.
- Various powders are produced using the process described in WO 00/67936 A1 from a partially agglomerated, finely particulate niobium pentoxide which has been screened through a screen with a mesh width of 300 μm and which comprises spherical primary particles with a diameter of approximately 0.4 μm, for the following experiments:
- Powder 0: The niobium pentoxide powder is reduced to NbO2 at 1250° C. under flowing hydrogen.
- Powder A: The niobium pentoxide powder is reduced to form NbO2 at 1480° C. under flowing hydrogen, milled and rubbed through a screen with a mesh width of 300 μm.
- Powder B: Powder 0 is reduced to the niobium metal by means of magnesium vapour at a temperature of 980° C., milled, agglomerated in vacuo at 1150° C., cooled, passivated by gradual admission of oxygen and rubbed through a screen with a mesh width of 300 μm.
- Powder C: Powder A and powder B are mixed in a molar ratio of 1:1, gently milled, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen and rubbed through a screen with a mesh width of 300 μm.
- Powder D: Powder A and powder B are mixed in a molar ratio of 1:0.8, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen, and then rubbed through a screen with a mesh width of 300 μm.
- Powder E: Powder A and powder B are mixed in a molar ratio of 1:0.7, heated to 1400° C. under an atmosphere comprising 80% by volume of argon and 20% by volume of hydrogen and then rubbed through a screen with a mesh width of 300 μm.
- Table 1 gives the properties (mean values) for the powders obtained.
- Mixtures were produced from the powders A, B, C, D and B, and these mixtures were used to produce anodes. The conditions are given in Table 2:
-
TABLE 1 Powder Powder Powder Powder Powder A B C D E NbO1.97 Nb NbO0.98 NbO1.21 NbO1.32 Primary particle μm 0.87 0.75 0.96 1.1 1.1 size1) Agglomerate D10, 43 37 58 67 56 size2) μm D50, 128 117 145 151 164 μm D90, 254 248 272 281 293 μm BET surface m2/g 1.6 1.05 1.1 1.1 1.1 area3) Flow properties4) s 30 28 59 60 58 1)determined visually from REM images. 2)laser diffraction (Malvern Mastersizer), ASTM B 822, wetting agent Daxad 11 3)ASTM D 3663 4)in accordance with Hall, ASTM B 213, duration of flow for 25 g of powder - First of all “powder preforms” were produced from the powders by introducing them into suitable press tools, into which a contact wire made from tantalum had been placed, and pressing to a green density of 2.8 g/cm3, and these powder preforms, standing freely in a furnace, were sintered at the temperature indicated either under a pressure of 10−5 bar (vacuum) or at standard pressure in the atmosphere indicated.
- To determine the compressive strength of the pressed and sintered bodies, cylindrical pressed bodies with a green density of 2.8 g/cm3 were produced with dimensions 3.6 =m diameter and 3.6 mm length with a weight of 106 mg without fitted contact wire and sintered where appropriate.
-
TABLE 2 Mixing ratio of the powders Pretreatment of the Exam- (parts by powders prior to ple weight) production of the Sintering No A:B:C:D:E pressed bodies conditions 1 0:0:100:0:0 ./. Vacuum, 1450° C. (Comp.) 2 0:10:90:0:0 Mixing Vacuum, 1350° C. 3 0:20:80:0:0 Mixing Vacuum, 1300° C. 4 0:30:70:0:0 Mixing Vacuum, 1270° C. 5 0:40:60:0:0 Mixing Vacuum, 1240° C. 6 0:20:80:0:0 Mixing, agglomeration5), Vacuum, 1350° C. 1250° C., argon; Milling, agglomeration, screening6) 7 0:30:70:0:0 Mixing, agglomeration, Vacuum, 1270° C. 1250° C., argon, milling, agglomeration, screening 8 57:43:0:0:0 Mixing 90 Ar + 10 H2 1300° C. 9 57:43:0:0:0 Mixing 90 Ar + 10 H2 1250° C. 10 57:43:0:0:0 Mixing 90 Ar + 10 H2 1200° C. 11 57:43:0:0:0 Mixing, agglomeration, 90 Ar + 10 H2 1150° C., argon, 1260° C. milling, screening 12 57:43:0:0:0 Mixing, agglomeration, 90 Ar + 10 H2 1150° C., argon, 1260° C. milling, agglomeration, screening 13 0:20:0:80:0 Mixing 95 Ar + 5 H2, 1270° C. 14 0:30:0:0:70 Mixing 95 Ar + 5 H2, 1245° C. 5)“Agglomeration” means that the powders were heated at the temperature indicated in the atmosphere indicated to form sintered bridges over a period of 20 minutes. 6)Rubbing through a screen with a mesh width of 300 μm. -
TABLE 3 Powder properties after pretreatment Anode/capacitor properties Compressive Compressive Wire detach- Flow strength of strength ment spec. prop- the of the strength capac- Ex. erties powder sintered under itance No. s preform7) kg body8) kg tension9) kg μFV/g 1 59 0.5 5.2 1.5 77,131 (Comp.) 2 49 1.5 10.8 2.4 75,837 3 41 2.1 13.7 2.8 77,792 4 35 2.5 15.1 3.1 76,232 5 30 2.8 16.4 3.3 74,566 6 40 2.3 15.1 3.0 77,924 7 37 2.7 16.9 2.9 78,411 8 37 2.5 17.3 3.0 68,442 9 37 2.5 17.3 3.0 73,978 10 37 2.5 17.3 3.0 78,112 11 41 2.4 18.9 2.7 75,336 12 40 2.8 19.1 2.9 73,592 13 42 2.0 12.9 2.6 78,618 14 37 2.3 14.7 2.8 79,915 7)the pressed body without contact wire was clamped between the jaws of a compressive-force measurement apparatus and the jaws were pressed together until the pressed body disintegrated. 8)as under 7), but measured after sintering. 9)the anode body was clamped at the periphery in a threaded clamp, the contact wire was connected to a tension device and tensile load was applied until the wire became detached under tension. - Cylindrical anode bodies with a tantalum wire inserted axially in the centre, with a diameter of 3.6 mm and a length of 3.6 mm and an initial weight of powder of 103 mg, were produced in order to determine the capacitor properties and the wire detachment strength under tension.
- The anode structures were then formed in 0.1% by weight strength phosphoric acid up to a forming voltage of 30 V at a current intensity limited to 150 mA/g, with the voltage being maintained for over 2 h after the current intensity had dropped to 0. To measure the specific capacitance, the cathode used was an 18% by weight strength sulphuric acid solution, and the measurement was carried out at a bias voltage of 10 V and an AC voltage with a frequency of 120 Hz.
- Although the examples given above cannot yet be considered to have been optimized with regard to the process parameters selected, the advantages are clearly apparent and are very promising, even if the specific residual currents in some cases (with a high statistical scatter) reached 2 nA/μFV and were on average approximately 1 nA/μFV. Initial tests reveal the likelihood that the positive effects will be even greater with more finely particulate powders, i.e. powders which are suitable for capacitors with a higher capacitance, e.g. of over 120,000 μFV/g.
- Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
Claims (11)
1-14. (canceled)
15. A powder for the production of anode structures for solid electrolyte capacitors, comprising tertiary agglomerate particles, the tertiary particles being agglomerates of:
(i) a first member selected from the group consisting of primary particles of niobium suboxide, secondary particles of niobium suboxide and combinations thereof; and
(ii) a second member selected from the group consisting of primary particles of niobium metal, secondary particles of niobium metal and combinations thereof
16. A powder mixture, optionally comprising powder agglomerates, having a mean composition of the following formula,
NbOx
NbOx
wherein 0.7<x<1.3, which after being pressed to a green density of 2.8 g/cm3 has a compressive strength of over 2 kg.
17. A pressed body comprising the powder mixture of claim 15 that has been pressed to a density of from 2.3 to 3.7 g/ cm3.
18. A pressed body comprising the powder mixture of claim 16 that has been pressed to a density of from 2.3 to 3.7 g/ cm3.
19. A solid electrolyte capacitor anode comprising a sponge-like sintered structure, the sintered structure having regions which comprise niobium metal, and having regions which comprise niobium suboxide represented by the following formula,
NbOx
NbOx
wherein 0.7<x<1.3.
20. A solid electrolyte capacitor anode having a mean composition of formula
NbOx
NbOx
wherein 0.7<x<1.3, and having a wire detachment strength under tension of over 2.0 kg.
21. A solid electrolyte capacitor anode having a mean composition of formula NbOx, wherein 0.7<x<1.3, and having a compressive strength of over 10 kg.
22. A solid electrolyte capacitor comprising the anode of claim 19 .
23. A solid electrolyte capacitor comprising the anode of claim 20 .
24. A solid electrolyte capacitor comprising the anode of claim 21 .
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Publication number | Priority date | Publication date | Assignee | Title |
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Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
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DE10333156A1 (en) * | 2003-07-22 | 2005-02-24 | H.C. Starck Gmbh | Process for the preparation of niobium suboxide |
DE10347702B4 (en) * | 2003-10-14 | 2007-03-29 | H.C. Starck Gmbh | Sintered body based on niobium suboxide |
US7693954B1 (en) * | 2004-12-21 | 2010-04-06 | Storage Technology Corporation | System and method for direct to archive data storage |
RU2424982C2 (en) * | 2005-06-03 | 2011-07-27 | Х.К. Штарк Гмбх | Niobium suboxide |
JP4804235B2 (en) * | 2005-08-29 | 2011-11-02 | 三洋電機株式会社 | Solid electrolytic capacitor element, manufacturing method thereof and solid electrolytic capacitor |
US7283350B2 (en) * | 2005-12-02 | 2007-10-16 | Vishay Sprague, Inc. | Surface mount chip capacitor |
GB0622463D0 (en) * | 2006-11-10 | 2006-12-20 | Avx Ltd | Powder modification in the manufacture of solid state capacitor anodes |
DE102008048614A1 (en) | 2008-09-23 | 2010-04-01 | H.C. Starck Gmbh | Valve metal and valve metal oxide agglomerate powder and process for their preparation |
DE102008063853B4 (en) * | 2008-12-19 | 2012-08-30 | H.C. Starck Gmbh | capacitor anode |
US20110042803A1 (en) * | 2009-08-24 | 2011-02-24 | Chen-Fu Chu | Method For Fabricating A Through Interconnect On A Semiconductor Substrate |
WO2017026316A1 (en) * | 2015-08-12 | 2017-02-16 | 株式会社村田製作所 | Capacitor and method for manufacturing same |
RU2610646C1 (en) * | 2015-12-21 | 2017-02-14 | Сергей Алексеевич Костин | Method for producing axially symmetrical parts of copper-based heat-resistant alloys |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4520430A (en) * | 1983-01-28 | 1985-05-28 | Union Carbide Corporation | Lead attachment for tantalum anode bodies |
US4722756A (en) * | 1987-02-27 | 1988-02-02 | Cabot Corp | Method for deoxidizing tantalum material |
US20010036056A1 (en) * | 1998-09-16 | 2001-11-01 | Kimmel Jonathon L. | Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides |
US6322912B1 (en) * | 1998-09-16 | 2001-11-27 | Cabot Corporation | Electrolytic capacitor anode of valve metal oxide |
US6373585B1 (en) * | 1998-08-26 | 2002-04-16 | International Business Machines Corporation | Load balancing for processing a queue of print jobs |
US20020114722A1 (en) * | 2000-03-23 | 2002-08-22 | Kimmel Jonathan L. | Oxygen reduced niobium oxides |
US20020135973A1 (en) * | 1998-09-16 | 2002-09-26 | Kimmel Jonathon L. | Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides |
US6558447B1 (en) * | 1999-05-05 | 2003-05-06 | H.C. Starck, Inc. | Metal powders produced by the reduction of the oxides with gaseous magnesium |
US20030218857A1 (en) * | 2001-05-15 | 2003-11-27 | Kazuhiro Omori | Niobium powder, niobium sintered body and capacitor using the sintered body |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3426243A1 (en) | 1984-07-17 | 1986-01-30 | Günter J. 8510 Fürth Bauer | Process for improving the residual current behaviour of high-capacitance valve metal powders |
WO2001071738A2 (en) * | 2000-03-23 | 2001-09-27 | Cabot Corporation | Oxygen reduced niobium oxides |
JP4828016B2 (en) | 2000-08-09 | 2011-11-30 | キャボットスーパーメタル株式会社 | Tantalum powder manufacturing method, tantalum powder and tantalum electrolytic capacitor |
JP4683512B2 (en) * | 2000-11-30 | 2011-05-18 | 昭和電工株式会社 | Capacitor powder, sintered body using the same, and capacitor using the same |
CN1549286A (en) * | 2003-05-08 | 2004-11-24 | 中南大学 | Niobium oxide electrolytic capacitor cathode and producing method thereof |
-
2004
- 2004-07-12 PT PT04016319T patent/PT1505611E/en unknown
- 2004-07-12 EP EP04016319A patent/EP1505611B9/en not_active Not-in-force
- 2004-07-15 KR KR1020040054985A patent/KR101115820B1/en not_active IP Right Cessation
- 2004-07-19 IL IL163089A patent/IL163089A/en not_active IP Right Cessation
- 2004-07-19 US US10/894,256 patent/US7410609B2/en not_active Expired - Fee Related
- 2004-07-19 IL IL195357A patent/IL195357A0/en unknown
- 2004-07-20 JP JP2004211980A patent/JP4217667B2/en not_active Expired - Fee Related
- 2004-07-21 MX MXPA04007050A patent/MXPA04007050A/en active IP Right Grant
- 2004-07-21 TW TW093121674A patent/TW200515445A/en unknown
- 2004-07-21 RU RU2004122054/09A patent/RU2368027C2/en not_active IP Right Cessation
- 2004-07-21 BR BR0402874-0A patent/BRPI0402874A/en not_active IP Right Cessation
- 2004-07-22 ZA ZA2004/05850A patent/ZA200405850B/en unknown
- 2004-07-22 AU AU2004203302A patent/AU2004203302C1/en not_active Ceased
- 2004-07-22 CN CN2004100545194A patent/CN1577659B/en not_active Expired - Fee Related
-
2008
- 2008-06-25 US US12/145,972 patent/US20080265220A1/en not_active Abandoned
-
2010
- 2010-04-08 AU AU2010201394A patent/AU2010201394B2/en not_active Ceased
Patent Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4520430A (en) * | 1983-01-28 | 1985-05-28 | Union Carbide Corporation | Lead attachment for tantalum anode bodies |
US4722756A (en) * | 1987-02-27 | 1988-02-02 | Cabot Corp | Method for deoxidizing tantalum material |
US6373585B1 (en) * | 1998-08-26 | 2002-04-16 | International Business Machines Corporation | Load balancing for processing a queue of print jobs |
US20010036056A1 (en) * | 1998-09-16 | 2001-11-01 | Kimmel Jonathon L. | Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides |
US6322912B1 (en) * | 1998-09-16 | 2001-11-27 | Cabot Corporation | Electrolytic capacitor anode of valve metal oxide |
US20020135973A1 (en) * | 1998-09-16 | 2002-09-26 | Kimmel Jonathon L. | Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides |
US6462934B2 (en) * | 1998-09-16 | 2002-10-08 | Cabot Corporation | Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides |
US6558447B1 (en) * | 1999-05-05 | 2003-05-06 | H.C. Starck, Inc. | Metal powders produced by the reduction of the oxides with gaseous magnesium |
US20020114722A1 (en) * | 2000-03-23 | 2002-08-22 | Kimmel Jonathan L. | Oxygen reduced niobium oxides |
US6576099B2 (en) * | 2000-03-23 | 2003-06-10 | Cabot Corporation | Oxygen reduced niobium oxides |
US20030218857A1 (en) * | 2001-05-15 | 2003-11-27 | Kazuhiro Omori | Niobium powder, niobium sintered body and capacitor using the sintered body |
US6934146B2 (en) * | 2001-05-15 | 2005-08-23 | Showa Denko K.K. | Niobium powder, niobium sintered body and capacitor using the sintered body |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10290429B2 (en) | 2017-01-17 | 2019-05-14 | Kemet Electronics Corporation | Wire to anode connection |
Also Published As
Publication number | Publication date |
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MXPA04007050A (en) | 2005-01-26 |
IL163089A (en) | 2010-06-30 |
AU2004203302B2 (en) | 2010-04-29 |
AU2004203302C1 (en) | 2010-09-16 |
ZA200405850B (en) | 2005-09-28 |
PT1505611E (en) | 2012-01-12 |
AU2010201394B2 (en) | 2012-11-22 |
CN1577659B (en) | 2011-08-17 |
BRPI0402874A (en) | 2005-05-24 |
EP1505611A2 (en) | 2005-02-09 |
RU2004122054A (en) | 2006-01-20 |
KR101115820B1 (en) | 2012-03-09 |
EP1505611B1 (en) | 2011-11-16 |
EP1505611B9 (en) | 2012-12-05 |
KR20050011691A (en) | 2005-01-29 |
RU2368027C2 (en) | 2009-09-20 |
AU2010201394A1 (en) | 2010-04-29 |
US20050018384A1 (en) | 2005-01-27 |
EP1505611A3 (en) | 2006-10-25 |
TW200515445A (en) | 2005-05-01 |
CN1577659A (en) | 2005-02-09 |
US7410609B2 (en) | 2008-08-12 |
AU2004203302A1 (en) | 2005-02-10 |
IL195357A0 (en) | 2009-08-03 |
JP4217667B2 (en) | 2009-02-04 |
JP2005045252A (en) | 2005-02-17 |
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