The invention relates a tantalum powder free of alkali and fluorine, which for a relatively small primary particle size has comparatively large secondary particles and is suitable for producing capacitors with a specific charge of between 100,000 and 180,000 μFV/g at specific residual currents of less than 2nA/μFV.

Tantalum powder, method for producing same powder and sintered anodes obtained from it

A method to agglomerate metal particles such as tantalum and niobium powders is described which includes combining a volatilizable or vaporizable liquid with the particles to form wet particles; compacting the wet particles; drying the compacted wet particles to form a cake; and heat treating the cake to form the agglomerated particles. Also described are agglomerated particles obtained by this method and further, particles, preferably tantalum or niobium powder, having a flow rate of at least about 65 mg/sec and/or an improved pore size distribution, and/or a higher Scott Density. Capacitors made from tantalum powder and niobium powder are also described.

Method to agglomerate metal particles and metal particles having improved properties

The tantalum powder for capacitors of the present invention has a specific surface area S B as determined by the BET method of 1.3 m 2 /g or more, and an S B /S F ratio between the specific surface area S B as determined by the BET method and the specific surface area S F determined by the FSS method of 4 to 10. This tantalum powder not only has a large specific surface area S B , but also has suitable cohesive strength and uniform porosity. Consequently, a solid state electrolytic capacitor having high capacitance and low ESR can be obtained by providing with a capacitor anode formed from a sintered body of this tantalum powder. In addition, whether or not this tantalum powder is suitable for the production of a tantalum capacitor having high capacitance and low ESR can be determined easily and reliably by evaluating the tantalum powder using the specific surface area S B as determined by the BET method and the S B /S F ratio between S B and the specific surface area S F determined by the FSS method.

Tantalum powder for capacitors

A method for spherically granulating and agglomerating metal particles such as tantalum and/or niobium powders is described in the present invention, which includes the steps of: a). comminuting the metal particles to form fine particles having D50 less than 50 µm: b). granulating the comminuted metal particles comprising volatile liquid, for example, tantalum and/or niobium particles comprising volatile liquid, to form wet spherical particles; c). still drying the wet spherical particles and removing volatile liquid to form flowable pre-agglomerated particles with increased bulk density; d). heat treating the pre-agglomerated particles; e). screening the heat treated powder to obtain the flowable agglomerated particles. The present invention provides a flowable spherical agglomerated metal particles, and especially tantalum and/or niobium particles having improved properties. The present agglomerated tantalum powder have a flow rate of at least about 2.0 g/sec, a BET surface area of from about 0.2 to about 6.0 m2/g, a FSSS of at least 1.0 µm, a Scott bulk density of from about 1.2 g/cm3 to about 5.5 g/cm3. The present agglomerated niobium powder have a flow rate of at least about 1.0 g/sec, a BET surface area of from about 0.5 to about 8.0 m2/g, a FSSS of at least 1.0 µm, a Scott bulk density of from about 0.7 g/cm3 to about 3.5 g/cm3. Said tantalum and/or niobium metal particles have improved pore size distribution of the sintered anodes and increased pellet crush strength. The present invention further provides an electrolytic capacitor anodes made from the tantalum and/or niobium particles according to the present invention having a capacitance of from about 5,000µFV/g to about 300,000µFV/g.

Methods for spherically granulating and agglomerating metal particles and the metal particles prepared thereby, anodes made from the metal particles

A pressed anode formed from an electrically conductive powder that contains a plurality of coarse agglomerates and fine agglomerates is provided. The fine agglomerates have an average size smaller than that of the coarse agglomerates so that the resulting powder contains two or more distinct particle sizes, i.e., a “bimodal” distribution. In this manner, the fine agglomerates can effectively occupy the pores defined between adjacent coarse agglomerates (“inter-agglomerate pores”). Through the occupation of the empty pores, the fine agglomerates can increase the apparent density of the resulting powder, which improves volumetric efficiency.

Capacitor Anode Formed From a Powder Containing Coarse Agglomerates and Fine Agglomerates

A capacitor having a central electrode body having sintered metal anode with an electrode lead, the anode having a sintered product produced from a tantalum powder having deagglomerated particles such that the product of the volume mean diameter in microns multiplied by the specific surface area measured in m 2 /g is a number in the range of below about 25. Capacitors having a central electrode with the anode produced from a sintered product produced from a heat treated and oxidized tantalum powder wherein the oxidized particle size is greater than about 0.7 m 2 /g. Capacitors are defined in terms of anodes produced from powders having specified ratios of Scott Bulk Density to surface area or ratio of die fill rate to surface area.

Tantalum metal power with controlled size distribution and products made therefrom

Verfahren zur herstellung von tantalpulver mit kontrollierter grössenverteilung sowie damit hergestellte formkörper

The present invention relates to a tantalum powder having substantially unimodal and narrow agglomerate size distribution, wherein the diameter of 10 percent of the agglomerate particles is less than 45 microns and the diameter of 90 percent of the agglomerate particles is less than 350 microns and the particles are defined by the following relationship 90 is less than or equal to [(MV) x (BET)] that is less than or equal to 250, wherein MV represents a Volume Mean Diameter (in microns as measured by light scattering techniques) and BET denotes specific surface area of the powder in me2/g. The specific surface area BET of the particles is greater than 0.7 me2/g. The invention also relates to a process for preparing the above-described tantalum powder as well as its use for producing capacitor anodes.

Fife James Allen

Papers

Tantalum metal power with controlled size distribution and products made therefrom

Verfahren zur herstellung von tantalpulver mit kontrollierter grössenverteilung sowie damit hergestellte formkörper

Tantalum powder, process for its preparation and use