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High capacitance tantalum flakes and methods of producing the same

Inactive Publication Date: 2006-04-06
CABOT CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] To achieve these and other advantages, and in accordance with the purposes of the present invention as embodied and broadly described herein, the present invention relates to a tantalum flake powder having maximized capacitance capabilities.

Problems solved by technology

Metallic and non-metallic contamination tends to degrade the dielectric oxide film in tantalum capacitors.
While high sintering temperatures serve to remove some volatile contaminants, high temperatures also tend to shrink the porous body reducing its net specific surface area and thus the capacitance of the resulting capacitor.
There is, however, a general lack of guidance in the art as to what thickness of tantalum flake should be used to ensure a particular capacitance at a particular formation voltage.

Method used

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  • High capacitance tantalum flakes and methods of producing the same
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  • High capacitance tantalum flakes and methods of producing the same

Examples

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example 1

[0056] In order to obtain a tighter flake thickness distribution as well as a lower average flake thickness, various samples were produced using a standard starting material, Kdel tantalum powder, which was a sodium reduced and acid leached basic lot powder used to make C275 Ta flake from Cabot Corporation. 5 lbs of the Kdel tantalum was slowly added into a 1S Attritor mill containing 50 lbs of 3 / 16″ stainless steel media and 2700 ml of ethyl alcohol. The powder was discharged from the mill after being milled at 250 rpm for 2 hrs. After replacing the 3 / 16″ media with ⅛″ stainless steel media, the mill was loaded with 2700 ml of fresh ethyl alcohol and 2.5 lbs of the 3 / 16″ milled powder. After being milled at 250 rpm and 6 hrs, the flake powder was then discharged and rinsed with DI water. The flakes were then acid leached to remove surface contaminants accumulated during the milling process. Flake samples were analyzed for Scott density and chemical composition.

[0057] Each sample w...

example 2

[0060] A C275 tantalum flaked powder which is commercially available from Cabot Corporation was compared to tantalum flakes prepared by multi-stage milling. In the example, the flakes of the present invention were prepared using a 2 stage milling process. 5 lbs of Kdel tantalum basic lot powder, a standard starting material for C 275 Cabot flake products, was milled in a IS Attritor mill at 250 rpm for 2 hrs. using 3 / 16 inch media (1st stage). 2.5 lbs of the milled material was then milled in the same mill using ⅛ inch media for additional 6 hours (2nd stage). The 2 stage milled flake sample was then acid leached and dried. The flake sample was then hydrided to reach a 4000 ppm of hydrogen level and milled in a Vortec mill in order to raise its Scott density from about 4-5 g / inch3 to about 20-25 g / inch3. The sample was then processed using standard C275 processes with adjusted heat treatment temperatures of 1200° C. and 1300° C. for 1st and 2nd heat treatment, respectively. After th...

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Abstract

Methods of maximizing a tantalum capacitor's capacitance are disclosed, as well as tantalum flake powder and anodes. A two step milling process can be used to mill tantalum particles into tantalum flake powder having flakes of the desired thickness. This flake powder can then be pressed and sintered thereby forming an anode. Other flake capacitance methods and products are also described.

Description

[0001] This application claims priority under 35 U.S.C. §119(e) of prior U.S. Provisional Patent Application No. 60 / 583,498 filed Jun. 28, 2004, which is incorporated in its entirety by reference herein.BACKGROUND OF THE INVENTION [0002] The present invention relates to high capacitance tantalum flakes and a method of producing the same. The present invention also relates to capacitors and anodes. [0003] With the ever increasing demand for capacitor materials, such as tantalum, it has become highly desirable to ensure the maximum amount of capacitance per unit of capacitor material. Tantalum capacitors typically are manufactured by compressing tantalum powder to form a pellet, sintering the pellet to form a porous tantalum body (electrode), and then subjecting the porous body to anodization in a suitable electrolyte to form a continuous dielectric oxide film on the sintered body. [0004] The amount of electricity that can be stored in a capacitor (CV, hereinafter) is a measure of the...

Claims

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Application Information

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IPC IPC(8): B22F9/04C22C27/02B22F1/052B22F1/068
CPCB22F1/0014B22F1/0055B22F2998/00B22F2998/10C22C1/045C22C27/02H01G9/042H01G9/0525B22F9/20B22F9/04B22F1/052B22F1/068
Inventor QIU, YONGJIAN
Owner CABOT CORP
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