Hoechst Ceramtec Aktiengesellschaft

Hoechst Aktiengesellschaft

Dieter Grote

Hans D Hermann

Karl Waldmann

Carl Hoffmann

Heinz Pavlicek

Fritz Muller

To produce Al.sub.2 O.sub.3 -containing ceramic film casting mixtures for thin-film circuits, unground, calcined alumina with low primary particle size and high reactivity is ground, optionally together with a solvent mixture, then the binder or a mixture of a plurality of different binders and the plasticizer or a mixture of a plurality of different plasticizers are added and the mixture is ground again until the alumina reaches a particle size of 2-10 .mu.m. The alumina, optionally together with a sintering aid, may first be ground alone in the solvent or the solvent mixture for 24 to 72 hours. The sintering aid or sintering aids may also be first ground in the solvent or the solvent mixture and the alumina added to the suspension obtained.

Process for producing ceramic film casting mixtures for thin-film

The firing shrinkage of ceramic film casting mixtures can be increased by adding a high molecular weight mixed ester or a mixture of various high molecular weight mixed esters to them. The ceramic material of the ceramic film casting mixtures is composed preferably of lead titanate, silicon carbide, silicon nitride, beryllium oxide or aluminum oxide. Preferably, the mixed esters are derived from at least one C.sub.2 -C.sub.10 -dicarboxylic acid and at least one C.sub.8 -C.sub.24 -monocarboxylic acid. The proportion of high molecular weight mixed ester in the film casting mixture amounts to up to 5% by weight, based on the proportion of solids in the casting mixture, including sintering aids. The process makes it possible to alter the composition of a slip and still use the old tools which require an unaltered firing shrinkage.

Process for increasing the firing shrinkage of ceramic film casting

Ceramic green films having advantageous isotropic distribution of the inorganic pigment can be obtained by casting and drying a slip containing finely divided inorganic pigment, organic solvents, polyvinylbutyral, plasticizer and dispersing agent if compounds which contain in their molecules at least one structural unit of the formula Z ##STR1## in which A and B, which must be different, stand for either the oxyalkylene unit --C.sub.3-4 H.sub.6-8 O-- or the oxyalkylene unit --C.sub.2 H.sub.4 O-- and x and y, which can be identical or different, each denote a number from 1 to 200, are used as dispersing agents. Ceramic green films produced according to the invention can be converted to isotropic ceramic substrates by subsequent heat treatment and sintering.

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Marktredwitz, Germany

Dieter Grote