Ngk Spark Plug Company, Limited

Sumihito Tominaga

Yukihiro Kimura

Rokuro Kanbe

Nobuhiko Miyawaki

A method of producing a sintered body by molding a mixture of a ceramic base powder, a sintering assistant powder and an organic binder and sintering the molded body in a non-oxidizing atmosphere is disclosed in which the ceramic base powder has such a particle size distribution that the amount of powder particles not greater than 1.0 .mu.m in size is not more than 15% by weight and the average particle diameter is not greater than 5 .mu.m. According to the method, therefore, sufficient passage of gas is secured in a degreasing step, resulting in an enhanced degreasing efficiency and exellent sintering properties. Where the sintering assistant powder has such a particle size distribution that the amount of powder particles not greater than 10 .mu.m in size is not more than 5% by weight, the amount of coarse powder is extremely small and, therefore, large voids are not formed. It is thus possible to produce easily a high-quality sintered body by controlling the respective particle size distributions of the powders.

Method of producing sintered ceramic body

A multilayer ceramic wiring board including a ceramic board having a plurality of through-holes and formed by laminating three or more green sheets of a ceramic material and burning a laminate of the green sheets, and a plurality of conductors provided in the through-holes. Each of the conductors is formed of a ceramic material and a conductive material in combination. The ceramic board is composed of a pair of upper and lower layer portions each having at least an outermost surface layer and an inner layer portion disposed between the upper and lower portions. The conductors are composed of an outer conductor portion formed in the upper and lower layer portions and an inner conductor portion formed in the inner layer portion. The outer conductor portion has a content ratio of the ceramic material higher than that of the inner conductor portion. Accordingly, the generation of cracks in the outer conductor portion disposed at the upper and lower layer portions of the ceramic board can be prevented, and an electric resistance can be reduced.

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Nagoya, Japan

Sumihito Tominaga