A multilayered ceramic wiring circuit board and the method of producing the same

Claim 1

A multilayered ceramic wiring circuit board including a plurality of ceramic insulating substrate layers (1) laminated integrally, conductor layers (2) with predetermined patterns supported on the respective ceramic insulating substrate layers and via hole conductors (8) provided at predetermined positions of the respective ceramic insulating substrate layers for interconnecting the respective conductor layers with predetermined patterns to form a predetermined wirng circuit,, the conductor layers and the via hole conductors being made of either tungsten or molybdenum characterized in that: said ceramic insulating substrate layer essentially consists of, crystals of mullite and an oxide complex of aluminum oxide and silicon dioxide in molar ratio of 1 : 0.7- non-crystalline silicon dioxide occupying interstices between the crystals; and at least one selected from the group consisting of alkali metal oxide and alkaline earth metal oxide dissolved substantially in the crystals in solid solution.

Claim 7

A method of producing a multilayered ceramic wiring circuit board including a plurality of ceramic insulating substrate layers (1) laminated integrally, conductor layers (2) with predetermined patterns supported on the respective ceramic insulating layers and via hole conductors (8) provided at predetermined positions of the respective ceramic insulating substrate layers for interconnecting the respective conductor layers with predetermined patterns to form a predetermined wiring circuit, the conductor layers and the via hole conductors being made of either tungsten or molybdenum characterized in that the steps comprise: mixing more than 70 wt% of mullite powder having an average particle size 5pm or less; 10-30 wt% of silicon dioxide powder having an average particle size below 2µm; less than 15 wt% of aluminum oxide powder having an average particle size below 1µm and less than 1 wt% of metal oxide powder of at least one selected from the group consisting ,of alkali metal oxide and alkaline earth metal oxide; pressing and forming the mixture; firing the pressed and formed mixture at a temperature above where the firing shrinkage ratio thereof becomes constant simultaneously with said conductor layers and said via hole conductors, whereby said ceramic insulating substrate layer thus produced essentially consists of crystals of mullite, sillimanite, andalusite and kyanite; non-crystalline silicon dioxide occupying the interstices between the crystals and at least one selected from the group consisting of alkali metal oxide and alkaline earth metal oxide dissolved substratially in the crystals in solid solution and has a thermal expansion coefficient of 40 - 60 x 10 -7 /°C and a dielectric constant below 6.7.

Claim 8

A method of producing a multilayered ceramic wiring circuit board including a plurality of ceramic insulating substrate layers (1) laminated integrally, conductor layers (2) with predetermined patterns supported on the respective ceramic insulating layers and via hole conductors (8) provided at predetermined positions of the respective ceramic insulating substrate layers for interconnecting the respective conductor layers with predetermined patterns to form a predetermined wiring circuit, the conductor layers and the via hole conductors being made of either tungsten or molybdenum characterized in that the steps comprise: mixing more than 70 wt% of mullite powder having an average particle size 5pm or less; 10-30 wt% of silicon dioxide powder having an average particle size below 2µm; less than 15 wt% of aluminum oxide powder having an average particle size below 1µm and less than 1 wt% of metal oxide powder of at least one selected from the group consisting ,of alkali metal oxide and alkaline earth metal oxide; pressing and forming the mixture; firing the pressed and formed mixture at a temperature above where the firing shrinkage ratio thereof becomes constant simultaneously with said conductor layers and said via hole conductors, whereby said ceramic insulating substrate layer thus produced essentially consists of crystals of mullite, sillimanite, andalusite and kyanite; non-crystalline silicon dioxide occupying the interstices between the crystals and at least one selected from the group consisting of alkali metal oxide and alkaline earth metal oxide dissolved substratially in the crystals in solid solution and has a thermal expansion coefficient of 40 - 60 x 10 -7 /°C and a dielectric constant below 6.7.