Galvanic process for making printed conductive metal markings for chipless RFID applications

Abstract

A process for printing a metal wire pattern on a substrate, including: printing a first salt solution including a metal ion that will undergo a reduction half-reaction; printing a second salt solution containing an oxidizing agent that will undergo an oxidation half-reaction in contact with the first salt solution, resulting in the reduction of the metal ions of the first salt solution; and allowing the first and second salt solutions to react by a galvanic reaction, causing reduced metal ions of the first salt solution to precipitate as a solid, on the substrate.

Claims

1. A system for printing a metal wire pattern on a substrate, the system comprising: an inkjet printer for printing on the substrate; a first ink supply reservoir containing a homogeneous first salt solution comprising a first solvent and a first metal ion, the first metal ion being selected from the group consisting of copper, aluminum, magnesium, manganese, zinc, chromium, lead, cadmium, cobalt, nickel, gold, silver, platinum, tin, iron, and mixtures thereof; and a second ink supply reservoir containing a homogeneous second salt solution comprising a second solvent and a second metal ion, the second metal ion being selected from the group consisting of iron (II), lead (II), chromium (II), mercury (II), platinum (IV), palladium (IV), nickel (III), and cobalt (III), wherein the system is configured to supply the first salt solution to the substrate separately from the second salt solution and to print the first salt solution and second salt solution so as to be in contact with one another on the substrate, the first salt solution and the second salt solution being chosen to react by a galvanic reaction to reduce metal ions of the first salt solution so as to precipitate a solid on the substrate and thereby form a metal wire.

2. The system according to claim 1, wherein the first metal ion is copper (II), and the second metal ion is chromium (III).

3. The system according to claim 1, wherein the printer comprises a heated printer head.

4. The system according to claim 1, wherein the second metal ion in the homogeneous second salt solution is provided in the form of a metal salt selected from the group consisting of metal sulfates, metal halides, metal acetates, metal oxides, metal carbonates, metal hydroxides, metal oxalates, metal pyrazolyl borates, metal azides, metal fluoroborates, metal carboxylates, metal halogencarboxylates, metal hydroxycarboxylates, metal aminocarboxylates, metal aromatics, which may optionally be nitro and/or fluoro substituted aromatic carboxylates, metal beta diketonates, and metal sulfonates.

5. The system according to claim 1, wherein at least one of the first solvent and the second solvent has a melting point of at least 30° C. and less than or equal to 100° C.

Description

EXAMPLES

Example 1

(1) Preparation of Salt Solution for Reduction Half-Reaction

(2) In a 10 mL volumetric flask, 25 mg of CuSO.sub.4.5H.sub.2O was dissolved in deionized water and made up into a 10 mL solution, with a final Cu.sup.2+ salt concentration of 10 mM. Similarly, a 10 mM solution of CuNO.sub.3 was also prepared by dissolving 23 mg of CuNO.sub.3 in 10 mL deionized water. Both solutions were pale blue in color.

(3) 2. Preparation of Salt Solution for Oxidation Half-Reaction

(4) In a 10 mL volumetric flask, 7.8 mg of [Cr(OAc).sub.2,H.sub.2,H.sub.2O].sub.2 was dissolved in deionized water and made up into a 10 mL solution, with a final Cr.sup.2+ salt concentration of 10 mM. Similarly, a 10 mM solution of CrCl.sub.2 was also prepared by dissolving 12.3 mg of CrCl.sub.2 in 10 mL deionized water. Both solutions were deep violet in color.

(5) 3. Formation and Deposit of Copper Wires on Substrate via Galvanic process

(6) A Dimatix printer cartridge was loaded with a Cu.sup.2+ salt solution (whose preparation is described above), and lines were printed on glossy coated paper. This cartridge was removed, and a second Dimatix printer cartridge was loaded with a Cr.sup.2+ salt solution (whose preparation is described above), and inserted into the printer. The initial printer Cu.sup.2+ lines were overprinted with the Cr.sup.2+ salt solution. The overprinted lines turned brown/orange in color, indicative of the plating out of pure copper films. The solvent residue was allowed to evaporate off, resulting in dried line features made of copper.

(7) It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.