Method for reducing the optical reflectivity of a copper and copper alloy circuitry and touch screen device
View Patent ↗The present invention relates to a method for reducing the optical reflectivity of a copper and copper alloy circuitry wherein a thin palladium or palladium alloy layer is deposited by immersion-type plating onto said copper or copper alloy. Thereby, a dull greyish or greyish black or black layer is obtained and the optical reflectivity of said copper or copper alloy circuitry is reduced. The method according to the present invention is particularly suitable in the manufacture of image display devices, touch screen devices and related electronic components.
1. A method for reducing the optical reflectivity of a copper or copper alloy circuitry by depositing thereon a metal layer of palladium or palladium alloy comprising, in this order, the steps of
(i) providing a dielectric substrate,
(ii) depositing copper or a copper alloy onto said dielectric substrate with the proviso that said dielectric substrate comprises a plating base when copper or a copper alloy is deposited by electroless (autocatalytic) plating or electroplating, and
(iii) depositing a palladium or palladium alloy layer onto said copper or copper alloy by immersion-type plating and thereby reducing the optical reflectivity of said copper or copper alloy,
wherein the palladium or palladium alloy is deposited in step (iii) from an aqueous plating bath comprising a source for palladium ions, an acid and at least one phosphonate compound, and
wherein by the immersion-type plating the palladium ions are reduced by metallic copper of the deposited copper or copper alloy,
and wherein the copper or copper alloy deposited in step (ii) is structured to form a circuitry either before step (iii) or after step (iii).
2. The method according to claim 1 wherein the copper or copper alloy deposited in step (ii) is structured to form a circuitry before step (iii).
3. The method according to claim 1 wherein the copper or copper alloy deposited in step (ii) is structured to form a circuitry after step (iii).
4. The method according to claim 1 wherein the palladium or palladium alloy layer formed in step (iii) is the outermost metal layer.
5. The method according to claim 1 wherein the dielectric substrate is selected from the group consisting of glass materials and plastic materials.
6. The method according to claim 1 wherein the copper or copper alloy is deposited by electroless (autocatalytic) plating from a plating bath comprising a source for copper ions, a reducing agent, at least one complexing agent and at least one stabilizer additive.
7. The method according to claim 1 wherein the plating base comprises a catalytically active metal which initiates electroless (autocatalytic) plating of copper or a copper alloy thereon or an electrically conductive material which initiates electroplating of copper or a copper alloy thereon.
8. The method according to claim 1 wherein the at least one phosphonate compound is selected from compounds according to formula (1)
wherein
R1 is selected from the group consisting of
hydrogen, methyl, ethyl, propyl and butyl;
R2 is selected from the group consisting of
hydrogen, methyl, ethyl, propyl and butyl;
R3 is selected from the group consisting of
hydrogen, methyl, ethyl, propyl and butyl;
R4 is selected from the group consisting of
hydrogen, methyl, ethyl, propyl and butyl;
n is an integer and ranges from 1 to 6; m is an integer and ranges from 1 to 6; o is an integer and ranges from 1 to 6; p is an integer and ranges from 1 to 6 and
X is selected from the group consisting of hydrogen, lithium, sodium, potassium and ammonium.
9. The method according to claim 1 wherein the concentration of the at least one phosphonate compound ranges from 0.15 to 20 mmol/l.
10. The method according to claim 1 wherein the pH value of the plating bath used in step (iii) ranges from 0.5 to 4.0.
11. The method according to claim 1 wherein the palladium alloy deposited in step (iii) is a palladium-copper alloy.
12. The method according to claim 1 wherein the optical reflectivity is reduced by 30 to 80% of the initial optical reflectivity of the copper or copper alloy circuitry.
13. The method according to claim 8 wherein the concentration of the at least one phosphonate compound ranges from 0.15 to 20 mmol/l.
14. The method according to claim 8 wherein the pH value of the plating bath used in step (iii) ranges from 0.5 to 4.0.
15. The method according to claim 1 wherein in the aqueous plating bath no reducing agent for palladium ions and/or external electrical current is utilized in step (iii).
16. The method according to claim 1 wherein following step (iii), no further metal or metal alloy layer is deposited onto the palladium or palladium alloy layer obtained in step (iii).