Feedstock and method for preparing the feedstock

• US 9,034,210 B2
• Filed: 12/05/2007
• Issued: 05/19/2015
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: TDK Electronics AG (TDK Corporation)
• Original Assignee: Epcos AG (TDK Corporation)
• Inventors: Ihle, Jan, Fischer, Verena, Hajek, Karin, Scheiwe, Gerd, Haferkorn, Thomas, Witzleben, Moritz V.
• Primary Examiner(s): PEETS, MONIQUE R
• Application Number:
  US11/950,744
• Publication Number:
  US 20090146116A1
• Time in Patent Office: 2,722 Days
• Field of Search: 252/500, 252/62.63, 252/519, 252/519.3, 252/519.33, 252/520, 252/520.21
• US Class Current: 252/500
• CPC Class Codes: B28B 1/24 by injection moulding injection moulding of ceramic slips B28B1/265; of tubular articles B28B21/38
• CPC Class Codes: C04B 35/468 based on barium titanates
• CPC Class Codes: C04B 35/634 Polymers C04B35/636 takes precedence
• CPC Class Codes: H05B 2203/02 Heaters using heating elements having a positive temperature coefficient
• CPC Class Codes: H05B 3/141 Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds

Abstract

A feedstock for injection molding includes a ceramic filler that is sinterable to produce a ceramic with a positive temperature coefficient of electrical resistance, a matrix for binding the ceramic filler, the matrix having a melting point lower than a melting point of the ceramic filler, and metallic impurities. A content of the metallic impurities in the feedstock is lower than 10 ppm.

Claims

1. A feedstock for injection molding, comprising:

a ceramic filler that is sinterable to produce a ceramic having a positive temperature coefficient of electrical resistance and a reference temperature in a range from −

30°

C. to 340°

C.;

a matrix for binding the ceramic filler, the matrix having a melting point lower than a melting point of the ceramic filler; and

metallic impurities caused by abrasion;

wherein a content of the metallic impurities in the feedstock is lower than 10 ppm taken either individually or in combination, and wherein the metallic impurities comprise one or more of Fe, Al, Ni, or Cr.

2. The feedstock of claim 1, wherein the ceramic filler comprises a material with a structure:

Ba_1-x-yM_xD_yTi_1-a-bN_aMn_bO₃, wherein

x=0 to 0.5,

y=0 to 0.01;

a=0 to 0.01 and

b=0 to 0.01;

wherein M comprises a cation of the valency two, D comprises a donor of the valency three or four, and N comprises a cation of the valency five or six.

3. The feedstock of claim 1, wherein the ceramic comprises a resistivity of 3 Ω

cm to 30000 Ω

cm at 25°

C.

4. The feedstock of claim 1, wherein a content of the matrix in the feedstock is less than or equal to 20 percent by mass.

5. The feedstock of claim 4, wherein the matrix comprises one or more of wax, resins, thermoplastics, or water soluble polymers.

6. The feedstock of claim 4, wherein the matrix comprises one or more of lubricants, plasticizers, or anti-oxidants.

7. The feedstock of claim 1, wherein the metallic impurities comprise two or more of Fe, Al, Ni, Cr, or W.