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 onto the flexible substrate, the precursor composition comprising metallic particles;
(b) confining the printed precursor composition to a region of the substrate with a physical barrier; and
(c) heating the precursor composition to form the conductive feature on the flexible substrate, the conductive feature having a minimum feature size of not greater than 100 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 physical barrier comprises trenches.
6 . The process of claim 5 , wherein the trenches are formed by chemical etching or photochemical means.
7 . The process of claim 5 , wherein the trenches are formed with a laser.
8 . The process of claim 5 , wherein the process further comprises the steps of:
(d) forming a layer on the flexible substrate; and
(e) forming the trenches in the layer.
9 . The process of claim 8 , wherein the layer comprises a photoresist layer.
10 . The process of claim 9 , wherein the trenches are formed in the photoresist layer with a laser.
11 . The process of claim 9 , wherein the trenches are formed in the photoresist layer through photolithography.
12 . The process of claim 4 , wherein the physical barrier comprises a feature having a porosity that retains the precursor composition by capillary forces.
13 . The process of claim 4 , wherein the physical barrier comprises retaining barriers.
14 . The process of claim 13 , wherein the retaining barriers are formed through a direct write printing process.
15 . The process of claim 13 , wherein the retaining barriers are formed through an ink jet printing process.
16 . The process of claim 15 , wherein the retaining barriers comprise two parallel lines with narrow parallel spacing, and wherein the precursor composition is direct printed between the two polymer lines to confine the precursor composition.
17 . The process of claim 4 , wherein the direct printing comprises directing droplets of the precursor composition toward a surface of the substrate, the droplets having an average droplet size not greater than about 10 μm.
18 . The process of claim 17 , wherein the average droplet size is not greater than about 5 μm.
19 . The process of claim 4 , wherein the direct printing comprises depositing droplets onto the substrate at a rate of 1000 drops per second or higher.
20 . The process of claim 19 , wherein each droplet comprise from about 25 to 100 picoliters of the precursor composition.
21 . The process of claim 4 , wherein the minimum feature size is not greater than 75 μm.
22 . The process of claim 4 , wherein the minimum feature size is not greater than 50 μm.
23 . The process of claim 4 , wherein the minimum feature size is not greater than 25 μm.
24 . The process of claim 4 , wherein the process further comprises surface modifying a surface of the substrate prior to the direct printing.
25 . The process of claim 24 , wherein the surface modifying comprises laser patterning.
26 . The process of claim 24 , wherein the surface modifying comprises forming trenches in the surface by chemical etching or photochemical means.
27 . The process of claim 4 , wherein the conductive feature has a thickness greater than 1 μm.
28 . The process of claim 4 , wherein the conductive feature has a thickness greater than 5 μm.
29 . The process of claim 4 , wherein the heating sinters adjacent metallic particles to one another.
30 . The process of claim 4 , wherein the metallic particles comprise a metal selected from the group consisting of silver, palladium, copper, gold, platinum and nickel.
31 . The process of claim 4 , wherein the metallic particles have a volume median particle size of not greater than 100 nanometers.
32 . The process of claim 4 , wherein the metallic particles comprise a metal and have a volume median particle size of not greater than 0.3 μm.
33 . The process of claim 32 , wherein the metallic particles comprise a cap or coating thereon.
34 . The process of claim 33 , wherein the cap or coating comprises an organic cap or coating.
35 . The process of claim 33 , wherein the cap or coating comprises a polymer.
36 . The process of claim 33 , 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.
37 . The process of claim 33 , wherein the cap or coating comprises PVP.
38 . The process of claim 32 , wherein at least 80 volume percent of the metallic nanoparticles are not larger than twice the average particle size.
39 . The process of claim 32 , wherein the conductive feature has a conductivity that is no less than 10 percent the conductivity of the equivalent pure metal.
40 . The process of claim 32 , wherein the conductive feature has a resistivity that is not greater than 4 times the resistivity of the equivalent pure metal.
41 . The process of claim 32 , wherein the conductive feature has a resistivity that is not greater than 2 times the resistivity of the equivalent pure metal.
42 . 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.
43 . 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.
44 . 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.
45 . The process of claim 4; wherein the flexible substrate has a softening point of not greater than about 225° C.
46 . The process of claim 4 , wherein the flexible substrate has a softening point of not greater than about 185° C.
47 . The process of claim 4 , wherein the flexible substrate has a softening point of not greater than about 150° C.
48 . The process of claim 4 , wherein the flexible substrate comprises a polyimide.
49 . The process of claim 4 , wherein the flexible substrate comprises a polymer.
50 . 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.
51 . The process of claim 4 , wherein the conductive feature comprises an electrode in a solar cell.
52 . The process of claim 4 , wherein the conductive feature is employed in a flat panel display.
53 . The process of claim 4 , wherein the conductive feature comprises a transparent conductive feature.
54 . The process of claim 4 , wherein the conductive feature comprises indium-tin oxide or antimony-tin oxide.
55 . A process for forming a conductive feature on a flexible substrate, the process comprising heating an ink jet printed precursor composition to form the conductive feature on the flexible substrate, wherein the precursor composition comprises metallic particles and is confined on the flexible substrate by a physical barrier, and wherein the conductive feature has a width of not greater than 100 μm.
56 . The process of claim 55 , wherein the physical barrier comprises trenches.
57 . The process of claim 56 , wherein the trenches are formed by chemical etching or photochemical means.
58 . The process of claim 56 , wherein the trenches are formed with a laser.
59 . The process of claim 56 , wherein the process further comprises the steps of:
(d) forming a layer on the flexible substrate; and
(e) forming the trenches in the layer.
60 . The process of claim 59 , wherein the layer comprises a photoresist layer.
61 . The process of claim 60 , wherein the trenches are formed in the photoresist layer with a laser.
62 . The process of claim 60 , wherein the trenches are formed in the photoresist layer through photolithography.
63 . The process of claim 55 , wherein the physical barrier comprises a feature having a porosity that retains the precursor composition by capillary forces.
64 . The process of claim 55 , wherein the physical barrier comprises retaining barriers.
65 . The process of claim 64 , wherein the retaining barriers are formed through a direct write printing process.
66 . The process of claim 64 , wherein the retaining barriers are formed through an ink jet printing press.
67 . The process of claim 66 , wherein the retaining barriers comprise two parallel lines with narrow parallel spacing, and wherein the precursor composition is direct printed between the two polymer lines to confine the precursor composition.
68 . The process of claim 55 , wherein the direct printing comprises directing droplets of the precursor composition toward a surface of the substrate, the droplets having an average droplet size not greater than about 10 μm.
69 . The process of claim 68 , wherein the average droplet size is not greater than about 5 μm.
70 . The process of claim 55 , wherein the direct printing comprises depositing droplets onto the substrate at a rate of 1000 drops per second or higher.
71 . The process of claim 70 , wherein each droplet comprise from about 25 to 100 picoliters of the precursor composition.
72 . The process of claim 55 , wherein the minimum feature size is not greater than 75 μm.
73 . The process of claim 55 , wherein the minimum feature size is not greater than 50 μm.
74 . The process of claim 55 , wherein the minimum feature size is not greater than 25 μm.
75 . The process of claim 55 , wherein the conductive feature has a thickness greater than 1 μm.
76 . The process of claim 55 , wherein the conductive feature has a thickness greater than 5 μm.
77 . The process of claim 55 , wherein the heating sinters adjacent metallic particles to one another.
78 . The process of claim 55 , wherein the metallic particles comprise a metal selected from the group consisting of silver, palladium, copper, gold, platinum and nickel.
79 . The process of claim 55 , wherein the metallic particles have a volume median particle size of not greater than 100 nanometers.
80 . The process of claim 55 , wherein the metallic particles comprise a metal and have a volume median particle size of not greater than 0.3 μm.
81 . The process of claim 80 , wherein the metallic particles comprise a cap or coating thereon.
82 . The process of claim 81 , wherein the cap or coating comprises an organic cap or coating.
83 . The process of claim 81 , wherein the cap or coating comprises a polymer.
84 . The process of claim 81 , 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.
85 . The process of claim 81 , wherein the cap or coating comprises PVP.
86 . The process of claim 80 , wherein at least 80 volume percent of the metallic nanoparticles are not larger than twice the average particle size.
87 . The process of claim 80 , wherein the conductive feature has a conductivity that is no less than 10 percent the conductivity of the equivalent pure metal.
88 . The process of claim 80 , wherein the conductive feature has a resistivity that is not greater than 4 times the resistivity of the equivalent pure metal.
89 . The process of claim 80 , wherein the conductive feature has a resistivity that is not greater than 2 times the resistivity of the equivalent pure metal.
90 . The process of claim 55 , wherein the heating comprises heating the precursor composition to a temperature not greater than 300° C. to form the conductive feature on the substrate.
91 . The process of claim 55 , wherein the heating comprises heating the precursor composition to a temperature not greater than 225° C. to form the conductive feature on the substrate.
92 . The process of claim 55 , wherein the heating comprises heating the precursor composition to a temperature not greater than 185° C. to form the conductive feature on the substrate.
93 . The process of claim 55 , wherein the flexible substrate has a softening point of not greater than about 225° C.
94 . The process of claim 55 , wherein the flexible substrate has a softening point of not greater than about 185° C.
95 . The process of claim 55 , wherein the flexible substrate has a softening point of not greater than about 150° C.
96 . The process of claim 55 , wherein the flexible substrate comprises a polyimide.
97 . The process of claim 55 , wherein the flexible substrate comprises a polymer.
98 . The process of claim 55 , 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.
99 . The process of claim 55 , wherein the conductive feature comprises an electrode in a solar cell.
100 . The process of claim 55 , wherein the conductive feature is employed in a flat panel display.
101 . The process of claim 55 , wherein the conductive feature comprises a transparent conductive feature.
102 . The process of claim 55 , wherein the conductive feature comprises indium-tin oxide or antimony-tin oxide.