US 5,492,653 A · Aqueous silver composition

Abstract

Coating compositions of silver flake suspended in predominantly aqueous vehicle is disclosed for laying down a coating of electrically conductive metal on resistive or dielectric substrates useful in the electronics industry. The coating compositions provide an ideal combination of high silver loading and low viscosity for spray painting desired thickness coatings at high speed in a single pass. The novel compositions include silver flake, water soluble polymer binder, water and a substantially completely water soluble, organic co-solvent. The coating compositions have good green strength after drying and may be used to apply an electrically conductive base to enable electroplating plastic or elastomer parts. Optional sintering adhesives can be added to allow high temperature, permanent bonding of the silver to a ceramic substrate. The coating compositions have excellent storage stability such that settled solids can be redispersed readily with brief and/or mild agitation.

Claims23

Dependent claims

A coating composition consisting essentially of:

(a) about 30 to about 80 wt % silver flake coated with a lubricant comprising at least one straight-chain carboxylic acid or salt of said acid, said lubricant having from 6 to 18 carbon atoms;
(b) about 1.5 to about 4.0 wt % substantially completely water soluble polymer binder;
(c) about 0.5 to about 8.0 wt % substantially completely water soluble co-solvent;
and
(d) a solvent effective amount of water;
wherein said percentages are based on total weight of the coating composition.

3 more elements

A coating composition consisting essentially of

(a) about 60 to about 75 wt % silver flake coated with a lubricant comprising at least one straight-chain carboxylic acid or salt of said acid, said lubricant having from 6 to 18 carbon atoms, wherein said silver flake is in a form of lamellar particles having a long dimension of at most about 15 .mu.m;
(b) about 1.5 to about 4.0 wt % water soluble polymer binder;
(c) about 0.5 to about 8.0 wt % substantially completely water soluble co-solvent;
(d) about 0.3 to about 6.0 wt % of at least one surfactant and defoamer additive;
(e) about 0.1 to about 5.0 wt % anti-settling agent;
(f) about 0.1 to about 2.0 wt % sintering adhesive component;
and
(g) a complementary amount of water to total 100 wt %;
wherein the amounts of (c) and (g) are in proportion such that viscosity of the coating composition is from about 0.3 to about 4.0 Pa.s.

6 more elements

Dependencies are inferred from the claim text.

Aqueous silver composition

Life of this patent

Aqueous silver composition

Life of this patent

Abstract

Claims23