Ceramic dielectrics

Claim 2

In a process for forming ceramic substrates, the steps comprising A. formulating a ceramic slurry composition by blending a ceramic particulate with a solvent soluble thermoplastic binder resin dissolved in a a. volatile organic solvent mixture forming a complete solvent for said resin and comprising a volatile first solvent fraction and a volatile second solvent fraction with i. said first solvent fraction constituting a complete solvent for said resin, ii. said second solvent fraction providing a maximum solubility of 5% for said resin therein, iii. the ratio of the evaporation rate of said first solvent fraction to said second solvent fraction being at least 2, and iv. the ratio, in parts by weight in said mixture of said first solvent fraction to said second solvent fraction being less than said evaporation rate ratio; and b. wherein said particulate comprises from about 80 to about 95 weight percent of the combined weight of said particulate and said binder resin; and c. wherein said solvent mixture is present in an amount to form a Brookfield viscosity for said slurry composition in the range of about 500 to about 2,000 cps. B. forming a ceramic slip by coating a layer of said composition on a removable flexible support; and C. forming a ceramic green sheet by a. removing a sufficient portion of said first solvent to precipitate and solidify said resin in a self-supporting structure having a portion of said second solvent fraction uniformly trapped therein; and b. removing said second solvent fraction from said resin structure to form a uniform distribution of micropores therein.

Claim 3

The process of claim 1 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 4

The process of claim 1 wherein said solvent mixture is a binary solvent.

Claim 5

The process of claim 1 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 6

The process of claim 1 wherein said first solvent fraction comprises an aliphatic alcohol containing from 1 to about 6 carbon atoms, and said second solvent fraction comprises an aliphatic ketone containing from about 4 to about 10 carbon atoms.

Claim 7

The process of claim 5 wherein said particulate is alumina.

Claim 8

The process of claim 5 wherein said alcohol is methanol and said ketone is methyl isobutyl ketone.

Claim 9

The process of claim 7 wherein said particulate is alumina.

Claim 10

In the process of claim 1 the inclusion of, the step firing a support-free said green sheet to drive off said binder resin and sinter said sheet into a rigid ceramic.

Claim 11

The process of claim 9 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 12

The process of claim 9 wherein said solvent mixture is a binary solvent.

Claim 13

The process of claim 11 wherein said evaporation rate ratio for said first solvent fraction to said second solvent fraction is at least 3.

Claim 14

The process of claim 9 wherein said first solvent fraction comprises an aliphatic alcohol containing from 1 to about 6 carbon atoms, and said second solvent fraction comprises an aliphatic ketone containing from about 4 to about 10 carbon atoms.

Claim 15

The process of claim 13 wherein said particulate is alumina.

Claim 16

The process of claim 13 wherein said alcohol is methanol and said ketone is methyl isobutyl ketone.

Claim 17

The process of claim 15 wherein said particulate is alumina.

Claim 18

In a process for forming ceramic substrates, the steps comprising A. formulating a ceramic slurry composition by blending a ceramic particulate with a solvent soluble thermoplastic binder resin dissolved in a a. volatile organic solvent mixture forming a complete solvent for said resin and comprising a volatile first solvent fraction and a volatile second solvent fraction with i. said first solvent fraction constituting a complete solvent for said resin, ii. said second solvent fraction providing a maximum solubility of 5% for said resin therein, iii. the ratio of the evaporation rate of said first solvent fraction to said second solvent fraction being at least 2, and iv. the ratio, in parts by weight in said mixture of said first solvent fraction to said second solvent fraction being less than said evaporation rate ratio; and b. wherein said particulate comprises from about 80 to about 95 weight percent of the combined weight of said particulate and said binder resin; and c. wherein said solvent mixture is present in an amount to form a Brookfield viscosity for said slurry composition in the preferred range of about 800 to about 1,000 cps. B. forming a ceramic slip by coating a layer of said composition on a removable flexible support; and C. forming a ceramic green sheet by a. removing a sufficient portion of said first solvent to precipitate and solidify said resin in a self-supporting structure having a portion of said second solvent fraction uniformly trapped therein; and b. removing said second solvent fraction from said resin structure to form a uniform distribution of micropores therein.

Claim 19

In a process for forming ceramic substrates, the steps comprising A. formulating a ceramic slurry composition by blending a ceramic particulate with a solvent soluble thermoplastic binder resin dissolved in a a. volatile organic solvent mixture forming a complete solvent for said resin and comprising a volatile first solvent fraction and a volatile second solvent fraction with i. said first solvent fraction constituting a complete solvent for said resin, ii. said second solvent fraction providing a maximum solubility of 5% for said resin therein, iii. the ratio of the evaporation rate of said first solvent fraction to said second solvent fraction being at least 2, and iv. the ratio, in parts by weight in said mixture of said first solvent fraction to said second solvent fraction being less than said evaporation rate ratio; and b. wherein said particulate comprises from about 80 to about 95 weight percent of the combined weight of said particulate and said binder resin; and c. wherein said solvent mixture is present in an amount to form a Brookfield viscosity for said slurry composition in the preferred range of about 800 to about 1,000 cps. B. forming a ceramic slip by coating a layer of said composition on a removable flexible support; and C. forming a ceramic green sheet by a. removing a sufficient portion of said first solvent to precipitate and solidify said resin in a self-supporting structure having a portion of said second solvent fraction uniformly trapped therein; and b. removing said second solvent fraction from said resin structure to form a uniform distribution of micropores therein.

Claim 20

The process of claim 17 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 21

The process of claim 17 wherein said solvent mixture is a binary solvent.

Claim 22

The process of claim 19 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 23

The process of claim 17 wherein said first solvent fraction comprises an aliphatic alcohol containing from 1 to about 6 carbon atoms, and said second solvent fraction comprises an aliphatic ketone containing from about 4 to about 10 carbon atoms.

Claim 24

The process of claim 21 wherein said particulate is alumina.

Claim 25

The process of claim 21 wherein said alcohol is methanol and said ketone is methyl isobutyl ketone.

Claim 26

The process of claim 23 wherein said particulate is alumina.

Claim 27

In the process of claim 17 the inclusion of, the step firing a support-free said green sheet to drive off said binder resin and sinter said sheet into a rigid ceramic.

Claim 28

The process of claim 25 wherein said evaporation rate ratio of said first solvent fraction to said second solvent fraction is at least 3.

Claim 29

The process of claim 25 wherein said solvent mixture is a binary solvent.

Claim 30

The process of claim 27 wherein said evaporation rate ratio for said first solvent fraction to said second solvent fraction is at least 3.

Claim 31

The process of claim 25 wherein said first solvent fraction comprises an aliphatic alcohol containing from 1 to about 6 carbon atoms, and said second solvent fraction comprises an aliphatic ketone containing from about 4 to about 10 carbon atoms.

Claim 32

The process of claim 29 wherein said particulate is alumina.

Claim 33

The process of claim 25 wherein said alcohol is methanol and said ketone is methyl isobutyl ketone.

Claim 34

The process of claim 31 wherein said particulate is alumina.