Low viscosity precursor compositions and methods for the deposition of conductive electronic features
A precursor composition for the deposition and formation of an electrical feature such as a conductive feature. The precursor composition advantageously has a low viscosity enabling deposition using direct-write tools. The precursor composition also has a low conversion temperature, enabling the deposition and conversion to an electrical feature on low temperature substrates. A particularly preferred precursor composition includes silver metal for the formation of highly conductive silver features.
1 . A process for forming a conductive feature on a flexible substrate, comprising:
(a) direct printing a precursor composition in multiple passes onto the flexible substrate, the precursor composition comprising metallic nanoparticles; and
(b) heating the precursor composition to form the conductive feature on the flexible substrate, the conductive feature having a thickness greater than 1 μm.
2 . The process of claim 1 , wherein the direct printing comprises syringe printing.
3 . The process of claim 1 , wherein the direct printing comprises aerosol jet deposition.
4 . The process of claim 1 , wherein the direct printing comprises ink jet printing.
5 . The process of claim 4 , wherein the conductive feature has a thickness greater than 5 μm.
6 . The process of claim 4 , wherein the heating occurs between the multiple passes.
7 . The process of claim 4 , wherein the heating occurs after the multiple passes.
8 . The process of claim 4 , wherein the conductivity of the conductive feature is no less than 10 percent the conductivity of the equivalent pure metal.
9 . The process of claim 4 , wherein the conductive feature has a resistivity that is not greater than 4 times the resistivity of the equivalent pure metal.
10 . The process of claim 4 , wherein the conductive feature has a resistivity that is not greater than 2 times the resistivity of the equivalent pure metal.
11 . The process of claim 4 , wherein the metal is selected from the group consisting of silver, palladium, copper, gold, platinum and nickel.
12 . The process of claim 4 , wherein the metallic nanoparticles have a volume median particle size of not greater than 100 nm.
13 . The process of claim 12 , wherein the silver nanoparticles comprise a cap or coating thereon.
14 . The process of claim 13 , wherein the cap or coating comprises an organic cap or coating.
15 . The process of claim 13 , wherein the cap or coating comprises a polymer.
16 . The process of claim 13 , wherein the cap or coating comprises an intrinsically conductive polymer, a sulfonated perfluorohydrocarbon polymer, polystyrene, polystyrene/methacrylate, sodium bis(2-ethylhexyl) sulfosuccinate, tetra-n-octyl-ammonium bromide or an alkane thiolate.
17 . The process of claim 13 , wherein the cap or coating comprises PVP.
18 . The process of claim 12 , wherein at least 80 volume percent of the metallic nanoparticles are not larger than twice the average particle size.
19 . The process of claim 4 , wherein the conductive feature has a width less than 200 μm.
20 . The process of claim 4 , wherein the conductive feature has a width less than 100 μm.
21 . The process of claim 4 , wherein the heating sinters adjacent nanoparticles to one another.
22 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 300° C. to form the conductive feature on the substrate.
23 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 225° C. to form the conductive feature on the substrate.
24 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 185° C. to form the conductive feature on the substrate.
25 . The process of claim 4 , wherein the flexible substrate has a softening point of not greater than about 225° C.
26 . The process of claim 4 , wherein the flexible substrate has a softening point of not greater than about 185° C.
27 . The process of claim 4 , wherein the flexible substrate has a softening point of not greater than about 150° C.
28 . The process of claim 4 , wherein the flexible substrate comprises a polyimide.
29 . The process of claim 4 , wherein the flexible substrate comprises a polymer.
30 . The process of claim 4 , wherein the flexible substrate is selected from the group consisting of polyfluoronated compounds, polyimides, epoxies, polycarbonates, paper, acetate, polyester, polyethylene, polypropylene, polyvinyl chloride, acrylonitrile, butadiene, flexible fiber board, non-woven polymeric fabric, cloth, metallic foil and thin glass.
31 . The process of claim 4 , wherein the conductive feature comprises an electrode in a solar cell.
32 . The process of claim 4 , wherein the conductive feature is employed in a flat panel display.
33 . The process of claim 4 , wherein the conductive feature comprises a transparent conductive feature.
34 . The process of claim 4 , wherein the conductive feature comprises indium-tin oxide or antimony-tin oxide.
35 . The process of claim 4 , wherein the process further comprises surface modifying the substrate with a laser.
36 . The process of claim 35 , wherein the laser increases or decreases the hydrophilicity of the substrate.