Flexible printed circuit, ink and method for obtaining flexible printed circuit thereof
A method for obtaining a flexible circuit with an solid-state electric or electronic component, the method comprising: arranging an electric circuit with a conductive flexible polymer-based ink over a polymeric substrate in the solid state, wherein one or both polymers in the ink and the substrate are reversible solid-gel phase transition polymers; placing the component over the substrate and over the electric circuit; applying an external stimulus that results in a solid to gel transition of the polymeric substrate and ink, such that the component penetrates into the softened substrate, establishing an electrical contact of the component with the circuit. Also disclosed is a method for obtaining the flexible circuit itself, the flexible circuit obtained by the method, and an ink for the method for obtaining a flexible circuit.
1 . A method for obtaining a flexible circuit with a solid-state electric or electronic component, the method comprising:
arranging an electric circuit with a conductive flexible polymer-based ink over a polymeric substrate in the solid state, wherein one or both polymers in the ink and the substrate are reversible solid-gel phase transition polymers;
placing the solid-state electric or electronic component over the substrate and over the electric circuit;
applying an external stimulus that results in a solid to gel transition of the polymeric substrate, or polymer-based ink, or both polymeric substrate and polymer-based ink, to soften same, such that the solid-state electric or electronic component penetrates the softened polymer-based ink or polymeric substrate, establishing an electrical contact of the solid-state electric or electronic component with the circuit.
2 . The method according to claim 1 subsequently comprising the step of removing the external stimulus that results in a gel to solid transition of the polymeric substrate and ink, such that the ink and the component are lodged in the substrate.
3 . The method according to claim 1 further comprising the steps of:
dissolving or softening the circuit with a solvent;
recovering the circuit component or components; and
optionally processing the dissolved solution to recover metal or metals present in order to recover at least one component of the circuit.
4 . The method according to claim 1 , further comprising dissolving the circuit with a solvent and processing a solution resulting from the dissolved circuit to recover ink ingredients.
5 . The method according to claim 1 , wherein the polymer is selected to have adhesive properties during its gel state.
6 . The method according to claim 1 , for repairing said circuit when the circuit has been subjected to an interruption, comprising the step of repeating the application of the external stimulus that results in a solid-gel transition of the polymeric substrate and polymer-based ink, such that the polymer-based ink electrically reconnects said interruption.
7 . The method according to claim 1 wherein the flexible circuit is stretchable.
8 . The method according to claim 1 , wherein the substrate and the ink are selected such that solid-gel transition is reversible for at least a predetermined number of transitions.
9 . The method according claim 8 , wherein the polymer of the ink, the substrate, or both is a styrenic block copolymers (SBC) selected from the group consisting of: styrene-isoprene block copolymers (SIS), Styrene-Ethylene-Butadiene-Styrene (SEBS), Styrene-Ethylene-Propylene-Styrene—SEPS, or the polymer is selected from the group of polyurethanes, Thermoplastic polyurethane (TPU), Fluorine rubbers, silicones, polycarbonates, Poly (ethylene terephthalate)-foil s (PET), Poly (ethylene naphthalate)-(PEN), Polyimine, and Poly (imide)-foil (PI).
10 . The method according to claim 1 , wherein the external stimulus for the solid-gel transition is exposure to vapour or airborne droplets of a material that causes the solid-gel transition in the substrate and the ink, or the external stimulus is selected from the group consisting of: heat, Ph, light, and a magnetic field, or the external stimulus for the solid-gel transition is exposure to solvent vapour or airborne droplets, and the solvent is a polymer-acceptable solvent, or the external stimulus for the solid-gel transition is exposure to toluene.
11 . The method according to claim 1 , wherein the ink comprises particles of a metal, a liquid metal and a polymer, in which the liquid metal is a metal that is liquid at the room temperature, defined as temperature above 20° C.
12 . The method according to claim 11 , wherein the liquid metal is Gallium, Indium, or mixtures thereof and the ink comprises Ag flakes in a SIS elastomer, as well as Gallium-Indium, forming an Ag—In—Ga—SIS composite, and the Gallium-Indium is eutectic Gallium-Indium (EGaIn), forming a SIS—Ag-EGaIn ink.
13 . The method according to claim 1 , further comprising causing the ink to penetrate into the softened substrate such that the ink in the obtained circuit is non-smearing to the touch.
14 . A circuit according to claim 1 , wherein the circuit is comprised by a gelatine-like non-smearing structure formed by the electric circuit and the polymeric substrate.
15 . A method for obtaining a flexible circuit, the method comprising:
arranging an electric circuit with a conductive flexible polymer-based ink over a polymeric substrate in the solid state, wherein both polymers in the ink and the substrate are reversible solid-gel phase transition polymers; and
applying an external stimulus that results in a solid to gel transition of the polymeric substrate and polymer-based ink to soften same, such that the polymer-based ink penetrates into the softened polymeric substrate for obtaining the flexible circuit.
16 . The method according to claim 15 , wherein the solid to gel transition of the substrate comprises softening the substrate and the ink for a period of time, such that the gel substrate climbs over the electronic component and surrounds said component, due to capillary action.
17 . The method according to claim 15 , wherein the ink has a higher density than the substrate such that the ink, when penetrating the substrate, descends into the substrate under the effect of gravity and is encapsulated within the substrate.
18 . The method according to claim 15 , further comprising:
placing the ink and the electronic component in relation to the substrate such that the ink and the electronic component penetrate into the softened substrate under the effect of gravity, or
applying a mechanical force over the electronic component such that the ink and the electronic component penetrate into the softened substrate.
19 . A process for producing a flexible circuit using a conductive polymer-based ink over a polymeric substrate, comprising:
printing, depositing or patterning the conductive polymer-based ink over the polymeric substrate in the solid state, wherein one or both polymers in the ink and the substrate comprise:
a reversible solid-gel phase transition polymer;
particles of a conductive material; and
a liquid metal,
thereafter applying an external stimulus for causing a polymer-gel transition, whereby either the electrical conductivity or mechanical deformability or both are improved.
20 . The process according to claim 19 , wherein the liquid metal comprises Gallium, Indium, or mixtures thereof, and wherein the polymer comprises an elastomer.
21 . The process according to the claim 19 , wherein the particles of a conductive material are metal particles or metal-coated particles.
22 . The process according to claim 21 , wherein the ink contains an intermetallic combination of the liquid metal with the metal or metal-coated particles.
23 . The process according to claim 19 , wherein the ink comprises a solvent suitable to prevent polymerisation of the ink before ink deposition or before solvent evaporation caused by ink deposition.
24 . The process according to claim 19 , wherein the particles of a conductive material are carbon-based particles.
25 . The process according to claim 19 , wherein the ink comprises Ag flakes in a SIS elastomer, as well as Gallium-Indium, forming an Ag—In—Ga—SIS composite.
26 . The process according to claim 19 , wherein the ink comprises Nickel or Ferrite or Copper or Zinc particles, or silver coated particles, in a SIS elastomer, as well as Gallium-Indium, forming a particle-In—Ga—SIS composite.
27 . The process according to claim 19 , wherein the improvement in conductivity is at least two times or wherein the improvement in mechanical deformability is sufficient to heal micro-cracks in the polymer substrate.