Forming conductive metal patterns using thiosulfate copolymers
View Patent ↗A conductive pattern can be formed using a polymeric layer that contains a reactive composition that comprises a reactive polymer that is metal ion-complexing, water-soluble, and crosslinkable. This reactive polymer comprises pendant thiosulfate groups as well as metal ion-complexing and water solubilizing groups. The reactive composition can be patternwise exposed to suitable radiation to induce crosslinking within the reactive polymer. The reactive composition and reactive polymer in the non-exposed regions can be removed due to their aqueous solubility, but the exposed regions of the polymeric layer are contacted with electroless seed metal ions, which are then reduced. The resulting electroless seed metal nuclei are electrolessly plated with a suitable metal to form the desired conductive pattern. Various articles can be prepared during this process, and the product article can be incorporated into various electronic devices.
1. A method of forming a pattern in a polymeric layer, the method comprising:
providing a polymeric layer on a substrate, which polymeric layer comprises a reactive composition comprising a non-crosslinked thiosulfate copolymer comprising, in any order: (a) recurring units comprising pendant thiosulfate groups, and (b) recurring units comprising pendant carboxy, carboxylate, phospho, phosphonate, phosphate, sulfo, sulfonate, or sulfite groups, wherein the (a) recurring units are present in an amount of at least 1 mol % and up to and including 30 mol %, and the (b) recurring units are present in an amount of at least 70 mol % and up to and including 99 mol %, both based on total recurring units in the non-crosslinked thiosulfate copolymer,
patternwise exposing the polymeric layer to radiation having a λ max of at least 150 nm that is sufficient to induce crosslinking within the non-crosslinked thiosulfate copolymer, to provide a polymeric layer comprising non-exposed regions and exposed regions comprising a crosslinked polymer derived from the non-crosslinked thiosulfate copolymer,
optionally heating the polymeric layer simultaneously with or after patternwise exposing the polymeric layer but before removing the reactive composition comprising the non-crosslinked thiosulfate copolymer in the non-exposed regions, at a temperature sufficient to further crosslink the crosslinked polymer in the exposed regions of the polymeric layer,
removing the reactive composition comprising the non-crosslinked thiosulfate copolymer in the non-exposed regions,
contacting the exposed regions of the polymeric layer comprising crosslinked polymer with electroless seed metal ions to form a pattern of electroless seed metal ions in the exposed regions of the polymeric layer,
reducing the pattern of electroless seed metal ions with a reducing agent for the electroless seed metal ions to provide a pattern of corresponding electroless seed metal nuclei in the exposed regions of the polymeric layer, and
electrolessly plating the corresponding electroless seed metal nuclei in the exposed regions of the polymeric layer with a metal that is the same as or different from the corresponding electroless seed metal nuclei.
2. The method of claim 1 , wherein the reactive composition further comprises a photosensitizer in an amount of at least 1 weight %, which photosensitizer provides sensitization at a λ max of at least 150 nm and up to and including 700 nm.
3. The method of claim 1 , wherein the non-crosslinked thiosulfate copolymer comprises the (a) recurring units in an amount of at least 5 mol % and up to and including 20 mol %, and the (b) recurring units in an amount of at least 70 mol % and up to and including 95 mol %, all based on the total recurring units in the non-crosslinked thiosulfate copolymer.
4. The method of claim 1 , wherein the (b) recurring units comprise pendant carboxylic acid, carboxylate, sulfonic acid, or sulfonate groups.
5. The method of claim 1 , wherein the non-crosslinked thiosulfate copolymer further comprises one or more additional (c) recurring units that are different from all of the (a) and (b) recurring units, the one or more additional (c) recurring units being present in an amount of up to and including 30 mol %, based on the total recurring units in the non-crosslinked thiosulfate copolymer.
6. The method of claim 1 , wherein:
the heating of the polymeric layer is required and is carried out after patternwise exposing the polymeric layer but before removing the non-crosslinked thiosulfate copolymer in the non-exposed regions, at a temperature sufficient to further crosslink the crosslinked polymer in the exposed regions of the polymeric layer.
7. The method of claim 1 , wherein the electroless seed metal ions are selected from the group consisting of silver ions, platinum ions, palladium ions, gold ions, rhodium ions, nickel ions, iridium ions, tin ions, and copper ions.
8. The method of claim 1 , wherein the metal for the electrolessly plating is selected from the group consisting of copper(II), silver(I), gold(IV), palladium(II), platinum(II), nickel(II), chromium(II), and combinations thereof.
9. The method of claim 1 , wherein the patternwise exposing of the polymeric layer is carried out at to radiation having a λ max of at least 150 nm and up to and including 450 nm.
10. The method of claim 1 , wherein the reducing agent for the electroless seed metal ions in the exposed regions of the polymeric layer is a borane, aldehyde, hydroquinone, or sugar reducing agent.