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Production of high-purity tantalum flake powder

a technology of high-purity tantalum flake and powder, which is applied in the direction of metal-working apparatus, transportation and packaging, etc., can solve the problem of reducing the performance of capacitors at a given formation voltage, and achieve the effect of thin, easy-to-size metal flak

Inactive Publication Date: 2008-09-25
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Benefits of technology

[0011]In accordance with an embodiment of the present invention, tantalum flake is produced by sizing ultra-thin tantalum foil via the hydride-dehydride (HDH) process. Tantalum is an extremely malleable metal and can be cold worked into extremely thin sheets less than 1 micron thick. Once hydrided, this foi...

Problems solved by technology

This variation in flake thickness reduces the performance of the capacitor at a given formation voltage.

Method used

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  • Production of high-purity tantalum flake powder
  • Production of high-purity tantalum flake powder
  • Production of high-purity tantalum flake powder

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[0021]Several sheets of Ta foil at various thicknesses and foil dimensions (150*500 mm, 50*50 mm and 25*25 mm) were tested, as shown in Table 1, below.

TABLE 1SampleFoil Thickness (μm)Foil Dimensions (mm)125150 × 50022.550 × 5030.525 × 25

[0022]Foil samples 1 and 2 were hydrided in a large HDH vessel at 600° C. Sample number 3 was hydrided in a small HDH vessel at 600° C. after being annealed under vacuum at 900° C. for 24 hours. After hydriding, each sample was broken apart using a mortar and pestle. Images were taken on an ISI SR-50 Scanning Electron Microscope with secondary electron detector. Samples 2 and 3 were then dehydrided in a furnace at 700° C. and 600° C. respectively.

[0023]SEM images of the mechanical flake process are shown in FIGS. 1 and 2. These images show the flakes prior to hydriding, and final sizing. The finished flakes will be much smaller in size. Edges of the flakes appear sharp, and less than 1 micron thick. FIGS. 3 and 4 show dehydride tantalum flake from th...

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Abstract

The present invention relates to a high-purity tantalum flake powder, produced by a hydride-dehydride process including: (a) cold working tantalum metal into a thin sheet; (b) hydriding the thin sheet, forming a brittle tantalum body, e.g., a foil or ribbon with an aspect ratio of greater than 5 to 1; (c) adjusting the tantalum body to a desired particle size; and (d) removing hydrogen from the tantalum body by vacuum sintering, forming a tantalum flake powder. In accordance with an embodiment of the present invention, tantalum flake is produced by sizing ultra-thin tantalum foil via the hydride-dehydride process. Tantalum is an extremely malleable metal and can be cold worked into extremely thin sheets less than 1 micron thick. Once hydrided, this foil is brittle, and can be easily sized by suitable milling processes. The hydrogen is removed by vacuum sintering, resulting in an extremely thin Ta metal flake.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. application Ser. No. 11 / 690,523, filed Mar. 23, 2007.FIELD OF THE INVENTION[0002]The present invention relates generally to methods of manufacturing tantalum flake for high CV / g / high voltage capacitors, using a process of mechanically flattening a nodular powder. Such an alternative method results in the production of tantalum flake with the potential for higher capacitance.BACKGROUND OF THE INVENTION[0003]Tantalum electrolytic capacitors date back to the late 1940s. Since that time, many improvements have been made to the manufacturing process, allowing for smaller, more reliable, and better performing components. Today, high CV / g / high voltage tantalum capacitors are dominated by flake technology. The particular flake morphology allows for high voltage applications, as the contacts between particles are line, rather than point with traditional powder metallurgy. As the dielectric is grow...

Claims

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Application Information

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IPC IPC(8): C22C27/02B22F9/16B22F1/068
CPCB22F1/0055C22C27/02B22F9/023B22F1/068
Inventor MCCRACKEN, COLIN G.HAWKINS, SCOTT M.
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