Process for making self-patterning substrates and the product thereof

• US 20090297802A1
• Filed: 08/22/2008
• Published: 12/03/2009
• Est. Priority Date: 05/29/2008
• Status: Active Grant

• Current Assignee: Chidella Krishna Sastry, Chidella Venkata Krishna Mohan Sharma, Srinivas Tangirala
• Original Assignee: Chidella Krishna Sastry, Chidella Venkata Krishna Mohan Sharma, Srinivas Tangirala
• Inventors: Sharma, Chidella Venkata Krishna Mohan, Sastry, Chidella Krishna, Tangirala, Srinivas
• Granted Patent: US 8,747,599 B2
• Time in Patent Office: Days
• US Class Current: 428/209
• CPC Class Codes: C23C 18/08 characterised by the deposition of metallic material
• CPC Class Codes: C23C 18/1608 from pretreatment step, i.e. selective pre-treatment
• CPC Class Codes: C23C 18/165 Multilayered product layered product B32B
• CPC Class Codes: C23C 26/00 Coating not provided for in groups C23C2/00 - C23C24/00
• CPC Class Codes: H05K 1/092 Dispersed materials, e.g. conductive pastes or inks
• CPC Class Codes: H05K 2203/0796 Oxidant in aqueous solution, e.g. permanganate
• CPC Class Codes: H05K 2203/107 Using laser light shaping a substrate by laser ablation H05K3/0026
• CPC Class Codes: H05K 2203/1105 Heating or thermal processing not related to soldering, firing, curing or laminating, e.g. for shaping the substrate or during finish plating
• CPC Class Codes: H05K 2203/1142 Conversion of conductive material into insulating material or into dissolvable compound
• CPC Class Codes: H05K 2203/1157 Using means for chemical reduction
• CPC Class Codes: H05K 2203/1163 Chemical reaction, e.g. heating solder by exothermic reaction oxidising metal H05K2203/0315
• CPC Class Codes: H05K 2203/121 Metallo-organic compounds
• CPC Class Codes: H05K 3/02 in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
• CPC Class Codes: H05K 3/105 by conversion of non-conductive material on or in the support into conductive material, e.g. by using an energy beam
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

The present invention relates to a process for making self-patterning substrates comprising the steps of providing electrically conductive traces on a substrate; pre-coating the substrate with at least a layer of complementary reactant electrically resistant reactant formulations; altering the conductivity of complementary reactant formulation selectively upon application of external source of energy and a self-patterning substrate using the said process.

Claims

1. A process for making self-patterning substrates comprising the steps of:

providing electrically conductive traces on a substrate;

pre-coating the substrate with at least a layer of complementary reactant electrically resistant reactant formulations;

altering the conductivity of complementary reactant formulation selectively upon application of external source of energy.

2. A process for making self-patterning substrates as claimed in claim 1, wherein the substrate is precoated with at least a layer of complementary reactant/electrically resistant reactant formulations in part and/or in full.

3. A process for making self-patterning substrates as claimed in claim 1, wherein the electrical resistance of reactant coating is higher than that of conductive trace being formed for a given surface area.

4. A process for making self-patterning substrates as claimed in claim 1, wherein the substrate is pre coated with a plurality of layers of complementary reactant/electrically resistant reactant formulations.

5. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive trace forming layers generates three-dimensional conductive patterns in response to variable localized heat sources.

6. A process for making self-patterning substrates as claimed in claim 4, wherein the pre-coated formulations layers exists in solid state and/or semi-solid state and/or liquid state at ambient conditions.

7. A process for making self-patterning substrates as claimed in claim 4, wherein the pre-coated formulation layer(s) with high electrical resistance comprise fine particles of inorganics such as metals, metal oxides/sulfides, metal alloys, metal salts, organometals, coordination complexes, precursors of metals, reducing agents, precursors of reducing agents or their combinations.

8. A process for making self-patterning substrates as claimed in claim 1, wherein single or multiple layers of complementary reactant formulations with high electrical resistance undergo chemical transformation upon exposure to localized heat source, light, resistive heating, inductive heating, hot gases, exothermic chemical heating, spark, laser, photochemical reaction, mechano-chemical reaction, microwave, optical or pressure induced reactions to yield conductive patterns of desired resistance and resolution.

9. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive traces includes pure metals, mixed metals, metal alloys, metal oxides, mixed metal oxides or combination of conductive and or semi conductive elements.

10. A process for making self-patterning substrates as claimed in claim 1, wherein the reactant formulations comprises of conductive precursors that undergo chemical reaction as a function of temperature to form conductive traces.

11. A process for making self-patterning substrates as claimed in claim 1, wherein the reactant formulation comprises precursors of metals and oxidizers/reducers and/or the precursors of oxidizers/reducers that coexist together under ambient conditions and the external energy source triggers a spontaneous redox reaction leading the formation of conductive patterns.

12. A process for making self-patterning substrates as claimed in claim 11, wherein the conductive pattern includes semi-conductive, resistive and conductive coatings.

13. A process for making self-patterning substrates as claimed in claim 1, wherein the reactant formulation comprises sequestering materials such as surface overcoats, layered compounds, clays, polymers, porous solids that release a conductive trace-forming agent.

14. A process for making self-patterning substrates as claimed in claim 1, wherein the energy/heating source is generated by resistive heating, inductive heating, hot gases, exothermic chemical heating, optical heating, laser/light or spark sources.

15. A process for making self-patterning substrates as claimed in claim 8, wherein the substrate is rapidly heated and cooled in order to promote the formation of pure metallic conductive traces with high resolutions and prevent the formation of unwanted metal oxides, especially when the conductive metals are air sensitive.

16. A process for making self-patterning substrates as claimed in claim 1, wherein the heating source changes the pH of the pre-coated layer(s) locally as a function of temperature and thereby generates resistive, conductive and/or semiconductive traces.

17. A process for making self-patterning substrates as claimed in claim 1, wherein the localized source of heat converts a resistive layer into conductive layer and/or a conductive layer is selectively turned into a resistive layer upon exposure.

18. A process for making self-patterning substrates as claimed in claim 1, wherein the pre-coated formulation layer(s) with high electrical resistance comprises of metal salts or metal oxides, organo metals, precursors of metals and reducing agents or precursors of reducing agents.

19. A process for making self-patterning substrates as claimed in claim 18, wherein the coating formulation includes fine conductive particles or surface modified conductive particles and/or metal precursors such as oxides, hydrides, hydroxides, sulfides, organometals, metal-organics, coordination complexes involving copper, cobalt, nickel, cadmium, iron, titanium, gallium, germanium, tin, indium, platinum, palladium, aluminum, chromium, manganese, silver, zinc, and gold.

20. A process for making self-patterning substrates as claimed in claim 18, wherein the preferred metal precursors of coating formulation are metal complexes with the formula:

[(L)_xM(A)_y(S)_z]^c;

Where L is the ligand or chelate or combination of ligands containing organic moieties, “

A”

is any organic or inorganic anion or combination of anions and the solvent molecule(s), “

S”

is an aqueous (water) or non-aqueous solvent which coordinates to the metal center, M, and/or is a part of the complex or supramolecular structure through non-covalent interactions, the values of x and y are such that the neutrality of the metal center M is maintained and that the net charge “

c”

is zero.

21. A process for making self-patterning substrates as claimed in claim 20, wherein the organic moieties are amines, ammonia, phosphanes, boranates, phosphates, isocyanide, alkene, alkyne, carboxylate, alkoxide and diketones or combinations thereof.

22. A process for making self-patterning substrates as claimed in claim 20, wherein “

A”

is any organic or inorganic anion like formate, carboxylates, halides, imines, sulfates, oxides, etc.

23. A process for making self-patterning substrates as claimed in claim 20, wherein “

S”

is an aqueous (water) or non-aqueous solvent which includes alcohols, acids, esters, alkanes, aromatics, amines, amides, ethers, silanes, phosphates, nitrites, phosphates, thiols, terpenes, sulfoxides and their combinations.

24. A process for making self-patterning substrates as claimed in claim 20, wherein the typical values of x, and y is selected between 0 to 10 and preferably between 1 to 4.

25. A process for making self-patterning substrates as claimed in claim 20, wherein, the coordination complexes have negative or positive charge “

c”

in the range of −

10 to +10, but preferably between −

4 and +4 depending on the nature of ligand “

L” and

anion “

A”

, and the values of x and y.

26. A process for making self-patterning substrates as claimed in claim 25, wherein, under condition that “

c”

is negative, then the complex is stabilized by cations NH₄+, Na+ and the like.

27. A process for making self-patterning substrates as claimed in claim 25, wherein, under condition that “

c”

is positive, then the complex is stabilized by anions, carboxylates, formate, halides and the like.

28. A process for making self-patterning substrates as claimed in claim 20, wherein, the preferred metals “

M”

are copper, silver, tin, zinc, cobalt, nickel, aluminum, gold, platinum and palladium.

29. A process for making self-patterning substrates as claimed in claim 1, further including the step of:

depositing of conductive metals for controlling the resolution and resistance of conductive traces either using similar or dissimilar metals using electroless or electroplating based processes.

30. A process for making self-patterning substrates as claimed in claim 1, wherein, under condition that one of the multi-layer coatings on the surface of the substrate is conductive then the coating formulation on top of conductive coating includes oxidizing agents, precursors of oxidizing agents, coordination or molecular complexing or chelating agents that selectively react with metal layer and form electrically resistant salts, metal oxides, complexes or combinations thereof.

31. A process for making self-patterning substrates as claimed in claim 30, wherein the coordinating or chelating agent are crystallization inhibitors, dispersants, surfactants, humectants, defoamers, and the like to control the formulation stability, coating properties, and the uniform conductive trace formation with required resistance and resolution.

32. A process for making self-patterning substrates as claimed in claim 30, wherein, coordinating or chelating agent includes molecular or polymeric ligands containing atoms, N, O and S such as primary, secondary and tertiary amines, alcohols, acids, esters, sulfonates, phosphonates, ethers and thiols and thioethers.

33. A process for making self-patterning substrates as claimed in claim 1, wherein the substrate is made of material which includes metals, non-metals, conductors, insulators, porous/non-porous materials, flexible and inflexible materials like plastic, polymers, resin, ceramic, glass, metal, metal oxides, organic-inorganic composites or any combination thereof.

34. A process for making self-patterning substrates as claimed in claim 33, wherein the substrate is made of some preferred materials which includes ceramics, composites, glass, fiberglass, laminated boards, or epoxy/phenolic materials impregnated with fibers or fibrous materials, carbon, silicon, silica, alumina, boria, titania, plastic, thermally stable polymers such as amides, imides, Kapton, carbonates, esters, metal foils coated with thin inorganic/electrically resistant inorganic layers (silica, alumina, zirconia), textiles, etc.

35. A process for making self-patterning substrates as claimed in claim 33, wherein the surface of the substrates are modified or patterned to control the binding properties of coating formulations and the subsequent conductive trace formation.

36. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive materials or their precursors are co-formulated with complementary chemical reagents such as reducing or oxidizing agents, chelating or coordinating agents, binders, passive or protective layers as required.

37. A process for making self-patterning substrates as claimed in claim 1, wherein the coatings over the substrate are formulated in such a way that they do not undergo any significant chemical reaction, under ambient or operational conditions, unless they are exposed to an external energy source leading to change in electrical resistance.

38. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive and semi-conductive traces comprises of semi-conducting elements (such as silicon, selenium, tellurium) metals (such as copper, silver, aluminum nickel, gold), metal alloys, metal oxides, and mixed metal oxides.

39. A process for making self-patterning substrates as claimed in claim 1, wherein the generation of different conductive patterns is applied by complementary reaction chemistries imbedded into two or more stacked layers and the external energy induce reactivity or fusion between two layers.

40. A process for making self-patterning substrates as claimed in claim 1, wherein the complementary reactants include complementary reducing and oxidizing agents and/or metal precursors.

41. A process for making self-patterning substrates as claimed in claim 40, wherein the complementary reducing agents reacts with metal precursors to form conductive traces include hydrogen, carbon monoxide, carbon dioxide, metal hydrides, sodium hypophosphite, formaldehyde, formic acid, dimethylamine borane, hydrazine, pyrazoline, ammonia, hydroxylamine, glycerol, dihydrobenzofuran, 9BBN, silanes, metals, metalloorganic decomposition materials, negatively charged ionic reducing gas and several other organic/inorganic reducing agents.

42. A process for making self-patterning substrates as claimed in claim 40, wherein the complementary oxidizing agent turns conductors into non-conductors includes organic or inorganic salts, oxygen, chlorates, perchlorates, permanganate, chromate, polyoxides, alkali metals or alkaline earth metals, transition or lanthanide metals, transition metal oxides, coordination complexes, inorganic acids such as HCl, HBr, H₂SO₄, HNO₃, phosphoric acids, molecular or polymeric organic acids such as carboxylic acids, sulfonic acids, phosphoric acids, quinines, etc.

43. A process for making self-patterning substrates as claimed in claim 1, wherein the pre-coated formulation layer(s) with high electrical resistance comprise fine particles of inorganics such as metals, metal oxides/sulfides, metal alloys, metal salts, organometals, and coordination complexes.

44. A process for making self-patterning substrates as claimed in claim 1, wherein the complementary reactant formulations on substrates are further coated with binders, crystallization inhibitors, dispersants, surfactants, humectants, defoamers, and the like.

45. A process for making self-patterning substrates as claimed in claim 44, wherein the binders are resistant to high temperatures and can actively or passively influence the conductive trace formation and its resolution.

46. A process for making self-patterning substrates as claimed in claim 44, wherein the binders are used to coat the complementary reactant formulations on substrates and provides strong adhesive and cohesive binding and facilitates the reaction chemistry that transforms the resistive layers into conductive patterns with high resolution.

47. A process for making self-patterning substrates as claimed in claim 46, wherein the binder includes clays (synthetic and natural), phosphates, alkoxides, inorganic polyanions/polycations, diatomaceous earth, sol-gels, aluminates, borates, silicates, titanates, zirconates, ceria, polymers, thermoset resins, thermoplastic resins and/or their combinations thereof.

48. A process for making self-patterning substrates as claimed in claim 1, wherein the electrically resistant formulations are deposited using a printing process selected from the group consisting of:

dip coating, inkjet printing, flexography, offset printing, gravure printing, rotary press, screen printing, pad printing, transfer printing, thermal printing, aerosol jet printing, tip dispensing, gap/blade coating, Meyer Bar coating, electrophotographic printing, and lithography.

49. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive trace forming layers generate 3D conductive patterns in response to variable localized heat sources.

50. A process for making self-patterning substrates as claimed in claim 1, wherein the conductive trace is formed under ambient, reducing, inert or vacuum conditions.

54. A process for making self-patterning substrates as claimed in claim 1, wherein the resolution of the conductive trace is defined by localization of the heat source/heat profile and the chemical kinetics of the conductive trace formation.

55. A process for making self-patterning substrates as claimed in claim 54, wherein to accomplish instant high temperatures ranging from 100 to 1000°

C. for short periods of time the substrates are provided with an overcoat of electrically resistant layers with appropriate exothermic reactants (e.g., thermite or inter-metallic).

56. A process for making self-patterning substrates as claimed in claim 1, wherein the typical temperatures required to initiate the chemical reaction to generate conductive patterns vary anywhere from 75°

C. to 800°

C. depending on the high temperature resistance of substrates and the nature of complementary reactant coating formulation.

57. A process for making self-patterning substrates as claimed in claim 1, wherein the self-patterning substrates offer rapid and cost effective way of prototyping and manufacturing conductive or semi-conductive traces or transistors for a wide variety of electric circuit related applications such as printed circuit boards, antennas (RFID), flex circuits, customized electronics, digital displays, photovoltaic cells, medical diagnostics and drug delivery.

58. A process for making self-patterning substrates as claimed in claim 1, wherein, the above process is used for forming conductive traces on planar and non-planar substrates.

59. A self-patterning substrate using the process as claimed in claim 1.

51. A process for making self-patterning substrates comprising the steps of:

providing electrically conductive traces on a substrate;

pre-coating the substrate with at least a layer of complementary reactant electrically resistant reactant formulations;

altering the conductivity of complementary reactant formulation selectively upon application of external source of energy;

providing a protective layer on top of conductive trace;

wherein the protective layer provides excellent shelf life to printed circuit boards, withstands high temperatures and does not undergo go any chemical transformation that affects the performance of conductive traces.

52. A process for making self-patterning substrates as claimed in claim 51, wherein the substrate is precoated with at least a layer of complementary reactant/electrically resistant reactant formulations in part and/or in full.

53. A process for making self-patterning substrates as claimed in claim 51, wherein the protective layer provides good shelf life, chemical and physical stability and temperature stability to the conductive traces formed.