Conductive Formulations For Use In Electrical, Electronic And RF Applications

Abstract

Metal flakes, an organic metal precursor, an organic solvent and either no binder, or a volatile or a thermally decomposable binder are combined to form a paste. The paste is deposited in a circuit pattern on a substrate and the circuit pattern is cured. While curing, the organic metal precursor decomposes to leave an electrically conductive path, and the printed circuit is thus formed. A precursor to an electrically conductive circuit material includes an organic metal precursor, metal microparticles, and an organic solvent. The method can be employed to form printed circuits, for a variety of electrical, electronic and sensing application, such as crack detection in ceramic, plastics, concrete, wood, fabric, leather, rubber or paper and composite materials.

What is claimed is: 
     
         1 . A printed circuit formed by a method comprising the steps of:
 a) combining metal flakes, an organic metal precursor, an organic solvent and a thermally decomposable binder consisting of a carbamate gel of N, N, N′-trimethyl ethylene diamine or ethylene diamine to form a paste;   b) depositing the paste in a circuit pattern on a substrate; and   c) curing the circuit pattern on the substrate, whereby the organic metal precursor decomposes to leave an electrically conductive path, thereby forming the printed circuit.   
     
     
         2 . The printed circuit of  claim 1 , wherein the circuit pattern consists of inductors, capacitors, or combinations thereof. 
     
     
         3 . The printed circuit of  claim 1 , wherein the circuit pattern is a crack sensor. 
     
     
         4 . The printed circuit of  claim 1 , wherein the paste is deposited into the substrate by screen printing. 
     
     
         5 . The printed circuit of  claim 1 , wherein the metal flakes have a major dimension in a range of less than about 10 micrometers. 
     
     
         6 . The printed circuit of  claim 5 , wherein the metal flakes have a major dimension of less than about 5 micrometers. 
     
     
         7 . The printed circuit of  claim 6 , wherein the metal flakes are in the form of nanoparticles having a diameter between about 20 and about 500 nanometers. 
     
     
         8 . The printed circuit of  claim 5 , wherein the paste includes the metal flakes in an amount in a range of between about 60% and about 90% by weight. 
     
     
         9 . The printed circuit of  claim 8 , wherein the paste includes the metal flakes in an amount in a range of between about 75% and about 85% by weight. 
     
     
         10 . The printed circuit of  claim 5 , wherein the organic metal precursor is at least one member selected from the group consisting of silver acrylate, silver 2,4 pentanedionate, silver neodecanoate and silver 2-ethylhexanoate. 
     
     
         11 . The printed circuit of  claim 5 , wherein the organic solvent is at least one member selected from the group consisting of ethyl lactate, butyl acetate, propylene glycol monomethyl ether acetate, 2-butoxyethyl acetate or 2-butoxyethanol. 
     
     
         12 . The printed circuit of  claim 5 , wherein the organic solvent includes at least one member selected from the group consisting of alpha terpineol, butylcarbitol acetate and carbamate. 
     
     
         13 . The printed circuit of  claim 1 , wherein the circuit pattern is cured at a temperature less than about 350° C. 
     
     
         14 . The printed circuit of  claim 13 , wherein the circuit pattern is cured at a temperatures less than about 250° C. 
     
     
         15 . The printed circuit of  claim 14 , wherein the circuit pattern is cured at a temperatures less than about 200° C. 
     
     
         16 . The printed circuit of  claim 15 , wherein the circuit pattern is cured at a temperatures less than about 150° C.