Copper ink and conductive solderable copper traces produced therefrom
An ink contains an admixture of a copper nanoparticle, a copper precursor molecule (e.g. a copper-aminediol complex), and a polymeric binder, the polymeric binder containing a polyester, polyimide, polyether imide or any mixture thereof having surface 5 functional groups that render the polymeric binder compatible with and/or soluble in a diol. The ink may be deposited on a substrate providing a trace that is conductive and directly solderable and has better mechanical strength than copper inks containing other types of polymeric binders.
1. An ink comprising an admixture of:
(a) a copper nanoparticle;
(b) a copper precursor molecule; and,
(c) a polymeric binder comprising a hydroxyl- and/or carboxyl-terminated polyester.
2. The ink according to claim 1 , wherein the copper precursor molecule comprises a copper-aminediol complex.
3. The ink according to claim 2 , wherein the copper-aminediol complex comprises a compound of Formula (I):
where R 1 , R 2 , R 3 and R 4 are the same or different and are NR 5 R 6 (R′(OH) 2 ) or —O—(CO)—R″, and at least one of R 1 , R 2 , R 3 or R 4 is NR 5 R 6 (R′(OH) 2 ), wherein: R 5 and R 6 are independently H, C 1-8 straight chain, branched chain or cyclic alkyl, C 2-8 straight chain, branched chain or cyclic alkenyl, or C 2-8 straight chain, branched chain or cyclic alkynyl; R′ is C 2-8 straight chain, branched chain or cyclic alkyl;
and, R″ is H or C 1-8 straight chain, branched chain or cyclic alkyl.
4. The ink according to claim 3 , wherein two of R 1 , R 2 , R 3 or R 4 are NR 5 R 6 (R′(OH) 2 ).
5. The ink according to claim 3 , wherein R 5 and R 6 are independently H or C 1-4 straight chain alkyl and R″ is H or C 1-4 straight chain alkyl.
6. The ink according to claim 3 , wherein R″ is H.
7. The ink according to claim 3 , wherein the OH groups on a given R′ substituent are not bonded to the same carbon atom.
8. The ink according to claim 1 , wherein the copper precursor molecule comprises copper(II) formate anhydrate:3-dimethylamino-1,2-propanediol (CuF:DMAPD), copper(II) formate anhydrate:3-diethylamino-1,2-propanediol (CuF:DEAPD), copper(II) formate anhydrate:3-methylamino-1,2-propanediol (CuF:MAPD), copper(II) formate anhydrate:3-amino-1,2-propanediol (CuF:APD), Cu(OH) 2 :ethanolamine, Cu(OH) 2 :diethanolamine or Cu(OH) 2 :triethanolamine.
9. The ink according to claim 1 , wherein the copper nanoparticles are present is in a range of about 0.25-5 wt %, based on total weight of the ink.
10. The ink according to claim 1 , wherein the polymeric binder is present in a range of about 0.25-1 wt %, based on total weight of the ink.
11. The ink according to claim 1 , wherein the copper precursor compound is present in a range of about 84 wt % or more, based on total weight of the ink.
12. A process for producing a conductive solderable copper trace on a substrate, the process comprising depositing an ink as defined in claim 1 on a substrate and sintering the ink on the substrate to produce a conductive solderable copper trace on the substrate.
13. The process according to claim 12 , wherein the depositing comprises screen printing the ink on the substrate.
14. An electronic device comprising a substrate comprising a conductive solderable copper trace produced by a process as defined in claim 12 .
15. The electronic device according to claim 14 , wherein the substrate comprises polyethylene terephthalate (PET), polyolefin, polydimethylsiloxane (PDMS), polystyrene, polycarbonate, polyimide, a silicone membrane, a textile, a thermoplastic polyurethane, paper, glass, metal or a dielectric coating.
16. The electronic device according to claim 14 , wherein the substrate comprises polyethylene terephthalate or polyimide.
17. The electronic device according to claim 14 comprising an electrical circuit, a conductive bus bar, a sensor, an antenna, a thin film transistor, a diode or smart packaging.