Nanopastes as patterning compositions for electronic parts
View Patent ↗The present invention provides methods of making an electronic part in which a nanopaste composed of inorganic nanoparticles and a carrier is applied onto a surface of a substrate. The composition is then processed to form an electrically conductive pattern area that adheres to the surface of the substrate. Optionally, the conductivity of the pattern area may be improved by heating.
1. A method of making an electronic part comprising:
providing a substrate;
applying onto a surface of the substrate a thermally sensitive composition comprising i) a nanopaste, which comprises inorganic nanoparticles and a carrier, and ii) a radiation absorber;
treating the nanopaste to form a layer on the substrate;
patternwise exposing the layer to thermal radiation to affect the solubility of exposed portions of the layer relative to unexposed portions of the layer; and
developing the layer to remove the exposed or unexposed portions of the layer to form an electrically conductive pattern area.
2. The method of claim 1 wherein the substrate comprises a polymer or a polymer laminate.
3. The method of claim 1 wherein the substrate comprises an epoxy laminate.
4. The method of claim 1 wherein the surface of the substrate is electrically non-conductive.
5. The method of claim 1 wherein the inorganic nanoparticles comprise metallic nanoparticles.
6. The method of claim 5 wherein the nanoparticles comprise silver, palladium or a mixture of silver and palladium.
7. The method of claim 5 wherein the nanoparticles comprise copper, gold, platinum, nickel or combinations thereof.
8. The method of claim 1 wherein the inorganic nanoparticles have an average diameter of loss than about 50 nm.
9. The method of claim 1 wherein the inorganic nanoparticles have an average diameter of less than about 25 nm.
10. The method of claim 1 wherein the inorganic nanoparticles have an average diameter of less than about 15 nm.
11. The method of claim 1 wherein the inorganic nanoparticles have an average diameter of less than about 10 nm.
12. The method of claim 1 wherein the nanopaste comprises a binder.
13. The method of claim 12 wherein the binder is soluble in substantially organic carriers.
14. The method of claim 12 wherein the binder is soluble in substantially aqueous carriers.
15. The method of claim 12 wherein the binder comprises epoxy resin, modified epoxy resin, polyester resin, novolak resin, cellulose resin, copolymers of vinylidene chloride and acrylonitrile, acrylic resin, polyvinyl resin, silicone resin, polyamide resin, vinyl alcohol resin, resol resin, acetal resin, polyacrylonitrile resin, formaldehyde resin, polycarbonate resin, polyimide resin, or copolymers or derivatives thereof.
16. The method of claim 12 wherein the binder comprises polyvinylpyrrolidone, polyvinyl alcohol, polyvinylimidazole, acrylic acid polymers, polyethyleneimine, poly(ethyloxazoline), gelatin, starches, dextrin, amylogen, gum arabic, agar, algin, carrageenan, fucoidan, laminaran, corn hull gum, gum ghatti, karaya gum, locust bean gum, pectin, guar gum, hydroxypropylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose or carboxymethylcellulose.
17. The method of claim 1 wherein the nanopaste is free of binders.
18. The method claim 1 wherein the nanopaste comprises a dispersing agent.
19. The method of claim 18 wherein the nanopaste comprises between about 0.05 to 15.0 w/w % dispersing agent.
20. The method of claim 18 wherein the nanopaste comprises between about 0.1 to about 5.0 w/w % dispersing agent.
21. The method of claim 2 wherein the dispersing agent comprises a surfactant.
22. The method of claim 1 wherein the surfactant is a cationic, anionic or amphoteric surfactant.
23. The method of claim 21 wherein the surfactant is a non-ionic surfactant.
24. The method of claim 21 wherein the surfactant comprises a perfluoroalkyl, alkylphenyl, or polysiloxane surfactant.
25. The method of claim 21 wherein the surfactant comprises a polysiloxane polyether, polysiloxane copolymer, alkyl-aryl modified methyl-polysiloxane or acylated polysiloxane.
26. The method of claim 21 wherein the surfactant comprises sorbitan tristearate, sorbitan monopalmitate, sorbitan triolate, monoglyceride stearate or polyoxyethylene nonylphenyl ether.
27. The method of claim 21 wherein the surfactant comprises alkyl di (aminoethyl) glycine, alkyl polyaminoethylglycine hydrochloride, 2-alkyl-n-carboxyethyl-N-hydroxyethyl imidazolinium betaine, or N-tetradecyl-N, N-substituted betaine.
28. The method of claim 21 wherein the surfactant comprises an alkylated surfactant, a fluorosurfactant, a siliconated surfactant or combinations thereof.
29. The method of claim 1 wherein the nanopaste further comprises a humectant, biocide, viscosity builder, colorant, pH adjuster, drying agent, defoamer or a combination thereof.
30. The method of claim 1 wherein the carrier is a substantially organic carrier.
31. The method claim 1 wherein the carrier is a substantially aqueous carrier.
32. The method of claim 1 wherein the nanopaste comprises between about 0.5 and about 75 w/w % inorganic nanoparticles.
33. The method of claim 32 wherein the nanopaste comprises between about 0.5 and about 25 w/w % inorganic nanoparticles.
34. The method of claim 33 wherein the nanopaste comprises between about 0.5 and about 10 w/w % inorganic nanoparticles.
35. The method of claim 1 wherein the thermally sensitive composition comprises between about 0.25 to about 25 w/w % radiation absorber.
36. The method of claim 1 wherein the radiation absorber is a dye.
37. The method of claim 36 wherein thermally sensitive composition comprises between about 0.25 to about 15 w/w % dye.
38. The method of claim 1 wherein the radiation absorber is a pigment.
39. The method of claim 38 wherein thermally sensitive composition comprises between about 5 to about 25 w/w % pigment.
40. The method of claim 1 wherein the radiation absorber comprises the structure:
41. The method of claim 1 wherein the treating step comprises drying the layer.
42. The method of claim 1 wherein the treating step comprises air or oven drying the layer.
43. The method of claim 1 further comprising heating the layer to between about 100 and 200° C.
44. The method of claim 1 further comprising heating the layer to between about 100 and 160° C.
45. The method of claim 1 wherein the electrically conductive pattern area has an electrical resistance of less than 100 kilo ohms/1000 feet at 20° C.
46. The method of claim 1 wherein the electrically conductive pattern area has an electrical resistance of less than 1 kilo ohm/1000 feet at 20° C.
47. The method of claim 1 wherein the electrically conductive pattern area has an electrical resistance of less than 500 ohms/1000 feet at 20° C.
48. The method of claim 1 wherein the electrically conductive pattern area has an electrical resistance of between 300 and 500 ohms/1000 feet at 20° C.
49. The method of claim 1 further comprising heating the electrically conductive pattern area to increase the conductivity of the electrically conductive pattern area.
50. The method of claim 1 wherein the patternwise exposing step comprises patternwise exposing the composition to IR radiation.
51. The method of claim 1 wherein the developing step comprises developing the layer in an aqueous alkaline solution.