Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Metal and nonmetal in final product
Reexamination Certificate
2000-03-09
2002-01-15
Mai, Ngoclan (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Metal and nonmetal in final product
C419S030000, C419S031000, C419S036000, C148S206000, C148S513000
Reexamination Certificate
active
06338816
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to nitrided niobium powders and electrolytic capacitors using the nitrided niobium powders as well as methods of making the powders and electrolytic capacitors.
For many years, it has been the goal of various researchers to develop niobium electrolytic capacitors because of the high di-electric constant of its oxide and the relatively low cost of niobium compared to a variety of other metals. Initially, researchers in this field considered the possibility of using niobium as a substitute for tantalum capacitors. Accordingly, many studies were conducted to determine the suitability of replacing tantalum with niobium.
In some of these studies, however, it was concluded that niobium has serious fundamental deficiencies that needed to be resolved, thus inferring that niobium was not an acceptable substitute for tantalum. (See J. Electrochem. Soc. p. 408 C. December 1977). In another study, one conclusion reached was that the use of niobium in solid electrolytic capacitors seems very unlikely due to various physical and mechanical problems, such as field crystallization. (Electrocomponent Science and Technology, Vol. 1, pp. 27-37 (1974)). Further, in another study, the researchers concluded that anodically formed passive films on niobium were different from electrical properties accomplished with tantalum and that the use of niobium led to complexities which were not present with tantalum. (See Elecrochimica Act., Vol. 40, no. 16, pp. 2623-26 (1995)). Thus, while there was initial hope that niobium might be a suitable replacement for tantalum, the evidence showed that niobium was not capable of replacing tantalum in the electrolytic capacitor market.
Besides tantalum electrolytic capacitors, there is a market for aluminum electrolytic capacitors. However, the aluminum electrolytic capacitors have dramatically different performance characteristics from tantalum electrolytic capacitors.
A driving force in electronic circuitry today is the increasing move toward tower Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL). As IC performance increases with submicron geometry, there is a need for lower power supply voltage and noise margin. At the same time, increasing IC speeds require higher power needs. These conflicting requirements create a demand for better power management. This is being accomplished through distributed power supplies which need larger currents for decoupling noise. Increasing IC speeds also mean lower switching times and higher current transients. The electrical circuit must, therefore, also be designed to reduce the transient load response. This broad range of requirements can be met if the circuit has large enough capacitance but low ESR and ESL.
Aluminum capacitors typically provide the largest capacitance of all capacitor types. ESR decreases with increase in capacitance. Therefore, currently a large bank of high capacitance aluminum capacitors are used to meet the above requirements. However, aluminum capacitors do not really satisfy the designers requirements of low ESR and ESL. Their mechanical construction with liquid electrolyte inherently produce ESR in the 100s of milliobm along with high impedance.
SUMMARY OF THE INVENTION
A feature of the present invention is to provide nitrided niobium powders.
A further feature of the present invention is to provide nitrided niobium powders, preferably having high surface areas and physical characteristics which permit the nitrided niobium powders to be formed into a capacitor having high capacitance.
Another feature of the present invention is to provide nitrided niobium powders which, when formed into capacitors, have a low DC leakage.
An additional feature of the present invention is to provide a method of reducing the DC leakage in a capacitor formed from nitrided niobium powder.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.
The present invention relates to a nitrided niobium powder. Another aspect of the present invention relates to any nitrided niobium powder having a BET surface area of at least about 0.15 m
2
/g.
The present invention also relates to a nitrided niobium powder, which when formed into an electrolytic capacitor anode, the anode has a capacitance of 30,000 CV/g a to about 61,000 CV/g.
Also, the present invention relates to a method to reduce DC leakage in a niobium anode made from nitrided niobium powder which comprises the step of introducing into the niobium powder a sufficient amount of nitrogen to reduce the DC leakage in a capacitor anode that is formed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
REFERENCES:
patent: 3427132 (1969-02-01), Goon
patent: 3496076 (1970-02-01), Cheseldine
patent: 3630718 (1971-12-01), Neuenschwander
patent: 3635693 (1972-01-01), Friedrich et al.
patent: 3647420 (1972-03-01), Restelli
patent: 3825802 (1974-07-01), Kumagai et al.
patent: 3847658 (1974-11-01), Kumagai
patent: 4017302 (1977-04-01), Bates et al.
patent: 4084965 (1978-04-01), Fry
patent: 4141720 (1979-02-01), Vartanian
patent: 4231790 (1980-11-01), Hähn et al.
patent: 4347084 (1982-08-01), Hähn et al.
patent: 4441927 (1984-04-01), Getz et al.
patent: 4483819 (1984-11-01), Albrecht et al.
patent: 4512805 (1985-04-01), Albrecht et al.
patent: 4537641 (1985-08-01), Albrecht et al.
patent: 4548672 (1985-10-01), Albrecht et al.
patent: 4569693 (1986-02-01), Albrecht et al.
patent: 4684399 (1987-08-01), Bergman et al.
patent: 4722756 (1988-02-01), Hard
patent: 4740238 (1988-04-01), Schiele
patent: 4940490 (1990-07-01), Fife et al.
patent: 4954169 (1990-09-01), Behrens
patent: 5211741 (1993-05-01), Fife
patent: 5234491 (1993-08-01), Chang
patent: 5242481 (1993-09-01), Kumar
patent: 5245514 (1993-09-01), Fife et al.
patent: 5284531 (1994-02-01), Fife
patent: 5412533 (1995-05-01), Murayama et al.
patent: 5448447 (1995-09-01), Chang
patent: 87 1 07675 (1988-05-01), None
patent: 1079333 (1993-12-01), None
patent: 0 953 847 (1999-11-01), None
patent: 1123015 (1965-08-01), None
patent: 80027601 (1980-07-01), None
patent: 58154221 (1983-09-01), None
patent: 1057995 (1983-11-01), None
patent: 1556420 (1994-02-01), None
Peabody, “Investigation of Columbium as an Electrolytic Capacitor Anode, Part II,”U.S Army Signal Research and Development Laboratory,DK Task Nr. 3A99-15-003-04, pp. 1-11 (No date available).
Palatnik, “Heat Field Stability and Crystallization Peculiarities of Amorphous Nb2O5, Films”Fizika I Khimiya Obrabotki Materialov,5:87-94 (Feb. 7, 1980).
Eckert, “Niobium Compounds and Alloys,”Int. J. Refractory Metals and Hard Materials,12:335-340 (1993-1994).
Bord et al., “Quality of Niobium Oxide Semiconductor Capacitors as a Function of Chemical Composition of the Niobium Powder,” No. 1(46):11-15 (1982).
Schwartz et al., “Niobium Solid Electrolytic Capacitors,”J. Electrochemical Society,108(8):750-757 (1961).
Al-Kharafi et al., “Phosphoric Acid Passivated Niobium and Tantalum EIS-Comparative Study,”Electrochimica Acta,40(16):2623-2626 (1995).
Jackson et al., “The Use of Niobium as an Anode Material in Liquid Filled Electrolytic Capacitors,”Electrocomponent Science and Technology,1:27-37 (1974).
J. Electrochemical Society:Reviews and News,24(12):408C-409C (Dec. 1977).
Orlov et al., “Study of Oxygen Solubility in Niobium,” Izvestiya Akademii Nauk SSSR. Metally, 5:202-205 (1985).
Krehl et al., “The Influence of Gas Atmospheres on the First-Stage Sintering of High-Purity Niobium Powders,”Metallurgical Transactions A,15A:1111-1116 (Jun. 1984).
Mifune et al., “Niobium Solid Electrolytic Capacitors,”National Technical Report9:147 (1963).
Levinskiy et al., “Change in Porous Structure and Leakage Currents of Niobium Capacitor Anodes During Electrolytic Oxidation,”Poroshk
Cabot Corporation
Mai Ngoclan
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