Appeal No. 2002-2080
Application 09/358,484
Accordingly, claims 21 through 25, 28 through 30, 32, 34 and 35 remain for our
consideration on appeal (see Paper No. 26). Claim 1 is illustrative of the claims on appeal:
21. A method for producing aluminum nitride ceramic having a dense smooth surface
layer possessing a surface roughness Ra of lower than 0.3 µm and possessing no defect larger
than 25 µm on its surface, comprising
(i) providing a sintered article of aluminum nitride and then applying at least one layer of
a paste of oxide glass that contains no Na, no K, no Rb, and no Pb for said surface layer directly
onto a surface of said sintered article of aluminum nitride and sintering said paste, or
(ii) providing a preform of aluminum nitride which is not yet sintered and then applying
at least one layer of a paste of oxide glass that contains no Na, no K, no Rb, and no Pb for said
surface layer directly onto a surface of said preform and sintering said paste and said preform,
wherein said paste is applied as a plurality of layers in which the layer adjacent to the
sintered article or preform has a higher softening point than the other layers and wherein the final
surface layer has a thickness between 10 µm and 250 µm after sintering, thereby producing an
aluminum nitride ceramic having a dense smooth surface layer possessing a surface roughness Ra
of lower than 0.3 µm and possessing no defect larger than 25 µm on its surface.
The appealed claims, as represented by claim 1, are drawn to a method for producing
aluminum nitride ceramic having a dense smooth surface layer possessing a surface roughness Ra
of lower than 0.3 µm and possessing no defect larger than 25 µm on its surface, comprising at
least the step of applying at least one layer of a paste of specified oxide glass onto a surface of
either (i) a sintered article of aluminum nitride and sintering the paste, or (ii) a preform of
aluminum nitride and sintering the preform and the paste, wherein the paste is applied as a
plurality of layers in which the layer adjacent to the sintered article or preform has a higher
softening point than the other layers and wherein the final surface layer has a thickness between
10 µm and 250 µm after sintering. In other appealed claims, the separate layers can each be
sintered as applied (claim 24); the sintered aluminum nitride can be limited with respect to
oxygen, carbon and boron content (claim 32); the layer can be a single thick layer (claim 34); and
the process can be specific to the preform of aluminum nitride (claim 35). According to
appellants, the aluminum nitride ceramics so prepared have heat-radiation properties which make
them useful, for example, as a substrate for integrated circuits (specification, e.g., page 1).
The references relied on by the examiner are:
Kondo et al. (Kondo) 5,122,930 Jun. 16, 1992
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