Dielectric composition

Claim 2

A castable dielectric composition comprising a dispersion of finely divided solids comprising: a. 50-75% wt. noncrystallizable glass of which the deformation temperature (T d ) is 580-625°C and the softening point (T s ) is 630-700°C, and (T s -T d ) is 50-75°C : b. 50-25% wt. refractory which is substantially insoluble in the glass at temperatures of 825-900°C, both dispersed in a solution of c. an organic polymeric binder in d. volatile nonaqueous organic solvent.

Claim 3

Composition of claim 1 in which the refractory solid consists essentially of 25-50% wt., basis total solids, of a material selected from the group consisting of A1 2 0 3 , mullite, cordierite SiO 2 , CaZrO 3 , forsterite, ZrO 2 and mixtures thereof.

Claim 4

A castable dielectric composition comprising the admixture of claim 1 dispersed in a solution of an organic polymeric binder in volatile nonaqueous solvent.

Claim 5

The composition of claim 3 in which the polymeric binder is a mixture of compatible polymers of 0-100% wt. C 1-8 alkyl methacrylate, 100-0% wt. C 1-8 alkyl acrylate and 0-5% ethylenically unsaturated carboxylic acid or amine, the multipolymer being further characterized as having a number average molecular weight (M n ) of 50,000-100,000, a weight average molecular weight (M w ) of 150,000-350,000, the ratio of M w to M n being no greater than 5.5, the total amount of unsaturated carboxylic acid or amine in the multipolymer mixture is 0.2-2.0% wt. and the glass transition temperature of the polymer and plasticizer therein if any is -30 to +45°C.

Claim 6

The composition of claim 4 in which the alkyl methacrylate is ethyl methacrylate and the alkyl acrylate is methyl acrylate.

Claim 7

The composition of claim 4 in which the ethylenically unsaturated carboxylic acid is a monocarboxylic acid selected from the group consisting of acrylic acid, methacrylic acid and mixtures thereof.

Claim 8

The composition of claim 3 in which the solvent is comprised on a weight basis of 70-83.5% by wt. 1,1,1-trichloroethane, 7-3% methylene chloride, 9-4% methyl ethyl ketone, 6-3% isopropanol and 9.3-6.5% fluorocarbons.

Claim 9

A method of forming a green tape by casting a thin layer of the dispersion of claim 3 onto a flexible substrate and heating the cast layer to remove the volatile organic solvent therefrom.

Claim 10

A method for forming a multilayer interconnection comprising the steps of: a. forming a patterned array of vias in a plurality of layers of green tape made by the process of claim 8; b. filling the vias in the green tape layer(s) of step a. with thick film conductor composition; c. printing at least one patterned thick film functional layer over a surface of each of the via-filled green tape layers of step b.: d. laminating the printed green tape layers of step c. to form an assemblage comprising a plurality of interconnected functional layers separated by unfired green tape: and e. cofiring the assemblage of step d.