CA2893584C - Method for forming thin film conductors on a substrate - Google Patents
Method for forming thin film conductors on a substrate Download PDFInfo
- Publication number
- CA2893584C CA2893584C CA2893584A CA2893584A CA2893584C CA 2893584 C CA2893584 C CA 2893584C CA 2893584 A CA2893584 A CA 2893584A CA 2893584 A CA2893584 A CA 2893584A CA 2893584 C CA2893584 C CA 2893584C
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- CA
- Canada
- Prior art keywords
- thin film
- precursor material
- substrate
- film precursor
- copper
- Prior art date
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Links
- 239000010409 thin film Substances 0.000 title claims abstract description 159
- 239000000758 substrate Substances 0.000 title claims abstract description 75
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000004020 conductor Substances 0.000 title claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 97
- 239000002243 precursor Substances 0.000 claims abstract description 60
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 54
- 229910052802 copper Inorganic materials 0.000 claims description 54
- 239000010949 copper Substances 0.000 claims description 54
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 22
- 229910052759 nickel Inorganic materials 0.000 claims description 11
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 10
- 238000000151 deposition Methods 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 10
- 229910052709 silver Inorganic materials 0.000 claims description 9
- 239000004332 silver Substances 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 6
- 230000001678 irradiating effect Effects 0.000 claims description 5
- 239000003638 chemical reducing agent Substances 0.000 claims description 4
- 238000005229 chemical vapour deposition Methods 0.000 claims description 4
- 238000003490 calendering Methods 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- 238000007639 printing Methods 0.000 claims description 2
- 229910044991 metal oxide Inorganic materials 0.000 claims 1
- 150000004706 metal oxides Chemical class 0.000 claims 1
- 239000010408 film Substances 0.000 description 23
- 230000006835 compression Effects 0.000 description 18
- 238000007906 compression Methods 0.000 description 18
- 229910052724 xenon Inorganic materials 0.000 description 13
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 13
- 238000000280 densification Methods 0.000 description 10
- 229920000139 polyethylene terephthalate Polymers 0.000 description 10
- 239000005020 polyethylene terephthalate Substances 0.000 description 10
- 230000003746 surface roughness Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 8
- 230000008901 benefit Effects 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 4
- -1 chorides Chemical class 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 150000002736 metal compounds Chemical class 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000005751 Copper oxide Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 229910000431 copper oxide Inorganic materials 0.000 description 2
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 2
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000000643 oven drying Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910021592 Copper(II) chloride Inorganic materials 0.000 description 1
- 239000004128 Copper(II) sulphate Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000004775 Tyvek Substances 0.000 description 1
- 229920000690 Tyvek Polymers 0.000 description 1
- 241000218220 Ulmaceae Species 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 238000004924 electrostatic deposition Methods 0.000 description 1
- 238000004049 embossing Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011067 equilibration Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 101150002826 inf2 gene Proteins 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000307 polymer substrate Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000007764 slot die coating Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000012430 stability testing Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
- H05K3/1283—After-treatment of the printed patterns, e.g. sintering or curing methods
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0386—Paper sheets
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0393—Flexible materials
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/09—Use of materials for the conductive, e.g. metallic pattern
- H05K1/092—Dispersed materials, e.g. conductive pastes or inks
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/01—Dielectrics
- H05K2201/0104—Properties and characteristics in general
- H05K2201/0116—Porous, e.g. foam
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/01—Tools for processing; Objects used during processing
- H05K2203/0104—Tools for processing; Objects used during processing for patterning or coating
- H05K2203/0143—Using a roller; Specific shape thereof; Providing locally adhesive portions thereon
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/02—Details related to mechanical or acoustic processing, e.g. drilling, punching, cutting, using ultrasound
- H05K2203/0278—Flat pressure, e.g. for connecting terminals with anisotropic conductive adhesive
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/15—Position of the PCB during processing
- H05K2203/1545—Continuous processing, i.e. involving rolls moving a band-like or solid carrier along a continuous production path
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/102—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by bonding of conductive powder, i.e. metallic powder
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/14—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using spraying techniques to apply the conductive material, e.g. vapour evaporation
Abstract
A method for forming thin film conductors is disclosed. A thin film precursor material is initially deposited onto a porous substrate. The thin film precursor material is then irradiated with a light pulse in order to transform the thin film precursor material to a thin film such that the thin film is more electrically conductive than the thin film precursor material. Finally, compressive stress is applied to the thin film and the porous substrate to further increase the thin film's electrical conductivity.
Description
FOR FORMING THIN FILM CONDUCTORS ON A SUBSTRATE
2
3 BACKGROUND OF THE INVENTION
4 1. Technical Field 7 The present invention relates to thin films in general, and, in particular, to 8 a method of forming thin film conductors on a substrate.
2. Description of Related Art Photonic curing is the high-temperature thermal processing of a thin film 13 using light pulses from a flashlamp. Photonic curing allows thin films on low-temperature 14 substrates to be processed in much shorter time periods (about 1 millisecond) than with an oven (which takes seconds to minutes).
- -SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, a thin film precursor material is initially deposited onto a porous substrate. The thin film precursor material is then irradiated with a light pulse in order to transform the thin film precursor material to a thin film such that the thin film is more electrically conductive than the thin film precursor material. Finally, compressive stress is applied to the thin film and the porous substrate to further increase the thin film's electrical conductivity.
Certain exemplary embodiments can provide a method for forming a thin film conductor on a substrate, said method comprising: depositing a thin film precursor material onto a porous substrate; irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate by a pair of pinch rollers to further increase said thin film's electrical conductivity, wherein said pinch rollers are driven at co¨v/r, where co is an angular velocity of said pinch rollers, r is a radius of said pinch rollers, and v is a moving speed of said thin film.
Certain exemplary embodiments can provide a method for forming a thin film conductor on a substrate, said method comprising: depositing a thin film precursor material onto a porous substrate; irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate to further increase said thin film's electrical conductivity, wherein said applying of compressive stress oscillates in magnitude with time.
All features and advantages of the present invention will become apparent in the following detailed written description.
3 The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying 6 drawings, wherein:
8 Figure 1 is a high-level process flow diagram of a method for forming thin 9 film conductors on a substrate, in accordance with a preferred embodiment of the present invention;
12 Figure 2 is a diagram of a photonic curing apparatus, in accordance with a 13 preferred embodiment of the present invention; and Figure 3 is a graph showing the height profile of a copper film on a paper 16 substrate before and after being compressed using the method depicted in Figure 1.
3 The relatively short processing time enabled by photonic curing can cause 4 problems. One of the artifacts of photonic curing is that the rapid heating of a thin film can generate gas within the thin film. If the gas generation is violent enough, the thin film 6 will undergo a complete cohesive failure, i.e., it may explode. More commonly, the thin 7 film develops a slight porosity. Often, the porosity is inconsequential, but it can, under 8 certain conditions, cause the thin film to be more mechanically fragile than its denser 9 counterparts. Furtheitnore, if the thin film has any electronic functionality, such as electrical conductivity, its sheet resistance will be higher as a result of the porosity. The 11 increased porosity in the thin film can also exhibit increased surface roughness as well.
12 This can inhibit the attachment of electrical components as well as diminish the cosmetic 13 appearance of the thin film. In addition, the increased porosity can cause enhanced 14 degradation of the thin film over time if the processed thin film is sensitive to elements, such as water or oxygen, commonly found in the environment. Thus, it would be desirable 16 to provide an improved method for forming thin film conductors on a substrate.
18 Referring now to the drawings and in particular to Figure 1, there is depicted 19 a flow diagram of a method for founing thin film conductors on a substrate, in accordance with a preferred embodiment of the present invention. Starting at block 100, a thin film 21 precursor material is initially deposited onto a substrate, as shown in block 110. The 22 material is then thettnally processed with a photonic curing apparatus such that the thin film 23 precursor material becomes a thin film material, as depicted in block 120. The electrical 24 conductivity of the thin film material is higher than that of the thin film precursor material.
Finally, compressive stress is applied to the thin film material located on the substrate to 26 cause the thin film material to densify such that its electrical conductivity of the thin film 27 material can be further increased, as shown in block 130.
1 A. Depositing thin film precursor material 2 The thin film precursor material can be in a particulate form. The thin film precursor material can also be dispersed in a liquid. The thin film precursor material can 4 be deposited onto a substrate by one or combinations of printing methods such as screen printing, inkjet, aerosol jet, flexographic, gravure, laser, pad, dip pen, syringe, or coating 6 methods such as airbrush, painting, roll coating, slot die coating, etc.
Alternatively, the thin film precursor material can be deposited without a 9 liquid including vacuum deposition techniques such as chemical vapor deposition (CVD), PECVD, evaporation, sputtering, etc. Other dry coating techniques in which the thin film 11 precursor material can be deposited include electrostatic deposition, xerography, etc.
13 The thin film precursor material is preferably contains a metal and/or a metal compound such as an oxide, salt, or organometallic. The thin film precursor material can be copper, nickel, cobalt, silver, carbon, aluminum, silicon, gold, tin, iron, zinc, titanium, 16 etc.
Examples of oxides include Cu2O, CuO, Co304, Co203, NiO, etc. Examples of salts include copper (II) nitrate, copper (II) chloride, copper (II) acetate, copper (II) sulphate, as 18 well as nitrates, chorides, acetates, and sulphates of cobalt, nickel, silver, etc.
If the thin 19 film precursor material contains a metal compound, a reducing agent generally accompanies it as well.
22 The substrate, which may be porous, preferably has a maximum working temperature of less than 450 C. Examples include polymers and cellulose.
Examples of 24 porous substrates include fiber based films that are calendered such as cellulose (e.g., paper) or polyethylene (e.g., Tyvek manufactured by DuPont ). Alternatively, the porosity may 26 be induced in the substrate by foaming the substrate material.
28 B. Photonic curing of the thin film precursor material 29 When the thin film precursor material is printed within a liquid, thermal processing of the thin film precursor material evaporates the solvent. If the thin film
2. Description of Related Art Photonic curing is the high-temperature thermal processing of a thin film 13 using light pulses from a flashlamp. Photonic curing allows thin films on low-temperature 14 substrates to be processed in much shorter time periods (about 1 millisecond) than with an oven (which takes seconds to minutes).
- -SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, a thin film precursor material is initially deposited onto a porous substrate. The thin film precursor material is then irradiated with a light pulse in order to transform the thin film precursor material to a thin film such that the thin film is more electrically conductive than the thin film precursor material. Finally, compressive stress is applied to the thin film and the porous substrate to further increase the thin film's electrical conductivity.
Certain exemplary embodiments can provide a method for forming a thin film conductor on a substrate, said method comprising: depositing a thin film precursor material onto a porous substrate; irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate by a pair of pinch rollers to further increase said thin film's electrical conductivity, wherein said pinch rollers are driven at co¨v/r, where co is an angular velocity of said pinch rollers, r is a radius of said pinch rollers, and v is a moving speed of said thin film.
Certain exemplary embodiments can provide a method for forming a thin film conductor on a substrate, said method comprising: depositing a thin film precursor material onto a porous substrate; irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate to further increase said thin film's electrical conductivity, wherein said applying of compressive stress oscillates in magnitude with time.
All features and advantages of the present invention will become apparent in the following detailed written description.
3 The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying 6 drawings, wherein:
8 Figure 1 is a high-level process flow diagram of a method for forming thin 9 film conductors on a substrate, in accordance with a preferred embodiment of the present invention;
12 Figure 2 is a diagram of a photonic curing apparatus, in accordance with a 13 preferred embodiment of the present invention; and Figure 3 is a graph showing the height profile of a copper film on a paper 16 substrate before and after being compressed using the method depicted in Figure 1.
3 The relatively short processing time enabled by photonic curing can cause 4 problems. One of the artifacts of photonic curing is that the rapid heating of a thin film can generate gas within the thin film. If the gas generation is violent enough, the thin film 6 will undergo a complete cohesive failure, i.e., it may explode. More commonly, the thin 7 film develops a slight porosity. Often, the porosity is inconsequential, but it can, under 8 certain conditions, cause the thin film to be more mechanically fragile than its denser 9 counterparts. Furtheitnore, if the thin film has any electronic functionality, such as electrical conductivity, its sheet resistance will be higher as a result of the porosity. The 11 increased porosity in the thin film can also exhibit increased surface roughness as well.
12 This can inhibit the attachment of electrical components as well as diminish the cosmetic 13 appearance of the thin film. In addition, the increased porosity can cause enhanced 14 degradation of the thin film over time if the processed thin film is sensitive to elements, such as water or oxygen, commonly found in the environment. Thus, it would be desirable 16 to provide an improved method for forming thin film conductors on a substrate.
18 Referring now to the drawings and in particular to Figure 1, there is depicted 19 a flow diagram of a method for founing thin film conductors on a substrate, in accordance with a preferred embodiment of the present invention. Starting at block 100, a thin film 21 precursor material is initially deposited onto a substrate, as shown in block 110. The 22 material is then thettnally processed with a photonic curing apparatus such that the thin film 23 precursor material becomes a thin film material, as depicted in block 120. The electrical 24 conductivity of the thin film material is higher than that of the thin film precursor material.
Finally, compressive stress is applied to the thin film material located on the substrate to 26 cause the thin film material to densify such that its electrical conductivity of the thin film 27 material can be further increased, as shown in block 130.
1 A. Depositing thin film precursor material 2 The thin film precursor material can be in a particulate form. The thin film precursor material can also be dispersed in a liquid. The thin film precursor material can 4 be deposited onto a substrate by one or combinations of printing methods such as screen printing, inkjet, aerosol jet, flexographic, gravure, laser, pad, dip pen, syringe, or coating 6 methods such as airbrush, painting, roll coating, slot die coating, etc.
Alternatively, the thin film precursor material can be deposited without a 9 liquid including vacuum deposition techniques such as chemical vapor deposition (CVD), PECVD, evaporation, sputtering, etc. Other dry coating techniques in which the thin film 11 precursor material can be deposited include electrostatic deposition, xerography, etc.
13 The thin film precursor material is preferably contains a metal and/or a metal compound such as an oxide, salt, or organometallic. The thin film precursor material can be copper, nickel, cobalt, silver, carbon, aluminum, silicon, gold, tin, iron, zinc, titanium, 16 etc.
Examples of oxides include Cu2O, CuO, Co304, Co203, NiO, etc. Examples of salts include copper (II) nitrate, copper (II) chloride, copper (II) acetate, copper (II) sulphate, as 18 well as nitrates, chorides, acetates, and sulphates of cobalt, nickel, silver, etc.
If the thin 19 film precursor material contains a metal compound, a reducing agent generally accompanies it as well.
22 The substrate, which may be porous, preferably has a maximum working temperature of less than 450 C. Examples include polymers and cellulose.
Examples of 24 porous substrates include fiber based films that are calendered such as cellulose (e.g., paper) or polyethylene (e.g., Tyvek manufactured by DuPont ). Alternatively, the porosity may 26 be induced in the substrate by foaming the substrate material.
28 B. Photonic curing of the thin film precursor material 29 When the thin film precursor material is printed within a liquid, thermal processing of the thin film precursor material evaporates the solvent. If the thin film
- 5.
6 PCT/US2012/067607 precursor material is the particulate form of the final thin film, the photonic curing additionally sinters the thin film precursor material. If the thin film precursor material is composed of multiple species designed to chemically react with each other (such as a metal compound and a reducing agent), then the theinial processing additionally reacts the precursor thin film material to form the final thin film which is generally a metal.
7 Thin film precursor material can be processed thermally using a photonic
8 curing apparatus. With reference now to Figure 2, there is illustrated a diagram of a
9 photonic curing apparatus, in accordance with a preferred embodiment of the present invention. As shown, a photonic curing apparatus 200 includes a conveyor system 210, a 11 strobe head 220, a relay rack 230, and a reel-to-reel feeding system 240. Photonic curing apparatus 200 is capable of irradiating a thin film precursor material 202 deposited on a substrate 203 situated on a web being conveyed past strobe head 220 at a relatively high 14 speed.
16 Strobe head 220 includes a high-intensity xenon flashlamp 221 for curing 17 thin film precursor material 202 located on substrate 203. Xenon flashlamp 221 can provide pulses of different intensity, pulse length, and pulse repetition frequency. For example, xenon flashlamp 221 can provide 10 ,as to 10 ms pulses with a 3" by 6" wide footprint at a pulse repetition rate of up to 1 kHz. The spectral content of the emissions 21 from xenon flashlamp 221 ranges from 200 nm to 2,500 nm. The spectrum can be adjusted 22 by replacing the quartz lamp with a ceria doped quartz lamp to remove most of the emission below 350 nm. The quartz lamp can also be replaced with a sapphire lamp to 24 extend the emission from approximately 140 nm to approximately 4,500 nm. Xenon flashlamp 221 can also be a water wall flash lamp that is sometimes referred to as a 26 Directed Plasma Arc (DPA) lamp.
28 Relay rack 230 includes an adjustable power supply, a conveyance control module, and a strobe control module. The adjustable power supply can produce pulses with energy of up to 4 kJ per pulse. Adjustable power supply is connected to xenon flashlamp 1 221, and the intensity of the emission from xenon flashlamp 221 can be varied by 2 controlling the amount of current passing through xenon flashlamp 221.
4 The adjustable power supply controls the emission intensity of xenon flashlamp 221. The power, pulse duration, and pulse repetition frequency of the emission 6 from xenon flashlamp 221 are electronically adjusted in real time and synchronized to the 7 web speed to allow optimum curing of thin film precursor material 202 without damaging 8 substrate 203, depending on the optical, thermal, and geometric properties of thin film 9 precursor material 202 and substrate 203. Preferably, the time duration of irradiation of each light pulse is less than the time to thermal equilibration time of the stack comprising 11 thin film precursor material 202 on substrate 203.
13 During the irradiation with light pulses, substrate 203 as well as thin film 14 precursor material 202 is being moved by conveyor system 210. Conveyor system 210 moves thin film precursor material 202 under strobe head 220 where thin film precursor 16 material 202 is cured by rapid light pulses from xenon flashlamp 221.
The power, 17 duration, and repetition rate of the emissions from xenon flashlamp 221 are controlled by 18 the strobe control module, and the speed at which substrate 203 is being moved past strobe 19 head 220 is determined by the conveyor control module.
21 When xenon flashlamp 221 is emitting light pulses, thin film precursor 22 material 202 is momentarily heated to provide the energy for curing thin film precursor 23 material 202. When a rapid pulse train is synchronized to moving substrate 203, a uniform 24 cure can be attained over an arbitrarily large area as each section of thin film precursor material 202 may be exposed to multiple light pulses, which approximates a continuous 26 curing system such as an oven.
28 C. Compressing processed material 29 After thin film precursor material 202 located on substrate 203 has been photonically cured with flashlamp 221 to form a thin film material 202', compressive stress 1 is applied to thin film material 202' and substrate 203 in order to densify thin film material 2 202 and substrate 203. Thin film material 202' on substrate 203 can be compressed by one 3 or combinations of existing technologies such as stamping, forging, rolling, calendering, 4 pressing, embossing, laminating, etc.
6 Rolling is preferably used in a reel-to-reel manufacturing setting by a set of 7 pinch rollers 260. Pinch rollers 260 are loaded, in compression, such that the peak pressure 8 applied to thin film material 202' and substrate 203 exceeds 25% of the ultimate tensile 9 strength (UTS) of the bulk thin film material after photonic curing at standard conditions.
For a relatively soft and ductile metal like copper, the preferred compression pressure range ii is between 7,500 and 30,000 psi (i.e., 25% to 100% of its ultimate tensile strength at 12 standard conditions).
14 Because substrate 203 is porous, it is compressible and responds to compression by reducing in thickness while keeping the same width, such as a fiber based 16 substrate like paper. This single dimensional change ensures that thin film material 202' 17 is not damaged by lateral deformation of substrate 203. The peak pressure capable of being 18 applied by pinch rollers 260 to polymer substrates that are non-porous, such as PET, may 19 be limited because PET is a low-temperature polymer that tends to be relatively soft. PET
will deform laterally at a lower pressure threshold than other substrates, which can cause 21 damage to thin film material 202' and substrate 203.
23 Pinch rollers 260 are driven at angular velocity co = v/r, where a) is the 24 angular velocity of pinch rollers 260 and r is the radius of pinch rollers 260, adjusted, and synchronized to the web speed, v, to allow optimum densification of thin film material 202' 26 without damaging substrate 203, depending on the mechanical and geometric properties of 27 thin film material 202' and substrate 203.
29 In certain situations, it may be advantageous to apply dynamic compressive stress (oscillating magnitude over time) with pinch rollers 260, driven at a certain - s -1 frequency, to thin film material 202' on substrate 203 to achieve high peak pressures with 2 a lower average force on pinch rollers 260 to extend tool lifetime and/or increase maximum 3 web speeds.
Heating pinch rollers 260 to a temperature between standard temperature and 6 the maximum working temperature of substrate 203 can decrease the required pressure to 7 achieve a similar result with standard temperature pinch rollers 260 due to the softening of 8 thin film material 202' during compression.
Compressive stress applied to thin film material 202' deposited on substrate 11 203 can increase the density of thin film material 202'. A particle or solution-based 12 deposited material has a density lower than the bulk precursor material due to a residual 13 pore structure within the deposited layer. Additionally, the photonic curing process may 14 introduce additional porosity in thin film material 202'. The volume of pore space relative to layer volume (volume fraction) will vary depending on material, process, and particle 16 size. Reducing the pore space volume fraction densifies the material improving its 17 performance in teaus of increased electrical conductivity if it is conductive, improved 18 mechanical stability and hardness, alters the surface properties like reducing surface 19 roughness and improving solder-ability, and improved chemical resistance if the material is prone to corrosion by reducing the surface area to volume ratio.
Compressing thin film 21 material 202' increases it density, which brings deposited thin film material 202' closer to 22 the properties of the bulk thin film material.
24 The following examples illustrate various methods of applying compressive stress to thin film materials located on a substrate. The results of compressive stress are 26 densification of thin film material on the substrate such that conductivity, mechanical 27 stability, and chemical resistance of the thin film material are improved.
Example 1: Compressive stress applied to thin films of mesoporous copper on paper 2 substrates screen printable version of a copper oxide reduction ink (part no. ICI-021 available from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index paper with a 230 mesh flat screen. The print was then dried in a 140 C oven for 5 minutes 6 to remove excess solvents. Initially, the ink had a sheet resistance that was ¨1 GQ/111.
7 That is, the resistance as measured by an ordinary multimeter was an open circuit.
9 The ink was converted to a conductive mesoporous copper thin film using a photonic curing apparatus (such as PulseForge 3300 X2 photonic curing system manufactured by NovaCentrix in Austin, Texas). The settings on the machine used for 12 curing were 430 V, 1,600 ms, overlap factor of 5, and at a web speed of 16 feet per 13 minute. The sheet resistance after photonic curing was 17.2 mK2/111.
The mesoporous copper thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 17 of 2,875 lbf to the foamed copper thin film on paper as it was drawn through the rollers.
18 The cross sectional area of compression was 0.074 in', yielding an average 38,850 psi applied to the printed conductors. Densification, via compression, of the mesoporous copper reduced the sheet resistance to 9.3 mf2/ EL Thus, compressing the mesoporous 21 copper decreased its resistivity by 46%.
Additional benefits to the overall perfoimance of the compressed copper 24 film, besides improved electrical conductivity, became apparent during surface mounted device (SMD) attachment evaluation, mechanical stability testing, and environmental 26 testing.
Compressed copper has demonstrated a significantly improved success rate 29 of attaching SMD components over as-converted mesoporous copper. The failure rate was 50% for thermode bonded SIVID silicon chips to the mesoporous copper.
Compressed -io-1 copper demonstrated a much higher success rate of 90% due to its low surface roughness.
Additionally, the reduced surface roughness alters the optical properties of the converted 3 copper from matte to nearly specular reflectivity at high pressures.
Referring now to Figure 3, there is illustrated a graph showing a height profile of foamed copper on paper before and after compression. Both the total height and 7 the surface roughness are reduced indicating increased density and reduced surface roughness of the copper film. Specifically, the surface roughness was reduced from 25 9 micron to 5 microns. The entire thin film stack was reduced in thickness by about 50 microns.
12 For copper on paper, there is a saturation point for what pressures improve 13 the electrical conductivity below the UTS of pure copper. As-converted mesoporous copper measured about 30 mn/111 in sheet resistance. Mesoporous copper film compressed at 8,300 psi (27% UTS of pure copper) measured 22 m52/111 in sheet resistance. At a pressure 16 of 12,000 psi (40% UTS of pure copper) the sheet resistance reached a minimum value of mS2/ El (saturation point). Further increasing the applied pressure to 25,000 psi (83%
18 UTS of pure copper) saw no improvement on the sheet resistance of the copper films.
However, when tracking the conductivity over time it was observed that copper films compressed at 12,000 psi gained in sheet resistance by 20% over 40 days in air. The 21 copper films compressed at 25,000 psi only gained in sheet resistance by 5% over 40 days 22 in air. Therefore, pressures beyond 40% UTS of pure copper (12,000 psi) are required for 23 corrosion resistance and stability over time for the copper thin film.
Even though increasing the applied stress by 2x did not improve the electrical conductivity of the films, the stability was greatly improved. This means that the 27 pore space volume fraction was reduced with the increased pressure (25,000 psi) and/or the 28 copper material was completely yielded and did not "spring back" like the films compressed 29 at half the pressure. The spring back effect is commonly seen in traditional sheet metal forming. In a manufacturing environment, in order to reduce a piece of sheet metal in 1 gauge, the material must be compressed or rolled through multiple stages. A single stage 2 gauge reduction is not useful due to the metal's tendency to expand in thickness after being reduced because of the elastic deformation component of the process. In this case, the 4 foamed copper compressed at 80% UTS yields completely and prevents residual elastic stress from degrading overall performance and stability of the compressed film.
7 After photonic curing, the converted mesoporous copper has a high surface 8 area to volume ratio contributing to its poor native corrosion resistance.
Compressing the mesoporous copper greatly reduces the surface area to volume ratio of the copper and improves the material's corrosion resistance. Environmental testing was perfolmed on bare 11 as-converted and compressed copper films on paper substrate. Compressed copper demonstrates a significantly improved corrosion resistance when tested in an environment 13 at 85 C/100% relative humidity for 24 hours. Uncoated mesoporous copper on paper does 14 not survive such an environmental test, but compressed copper survives un-coated and without a detectable change in conductivity. Uncoated compressed copper films passed an industry standard (1,000 hours at 85 C/85% relative humidity) with only an increase in resistivity by 20%. Additional cost benefits pertaining to production become apparent as required volumes of materials for encapsulating the compressed copper films are decreased 19 relative to as-converted copper.
21 When it is desirable to only reduce the surface roughness of the thin film, significantly lower pressure may be used. As-cured films of mesoporous copper on paper substrate exhibiting average surface roughness of 5 microns were compressed at 2,600 psi 24 (9%
UTS of pure copper) reducing the average surface roughness to 2 microns. At this pressure, the electrical conductivity of the mesoporous copper films was unchanged.
Example 2: Compressive stress applied to porous thin films of nickel on paper substrates screen printable version of a nickel flake ink (part no. 79-89-16 available 29 from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index paper with a 230 mesh flat screen. The prints were dried in a 150 C oven for 5 minutes to remove 2 excess solvents. After oven drying the sheet resistance measured 77 Q/171.
4 The dried ink was photonically cured to form a highly conductive porous nickel thin film using a photonic curing apparatus (such as PulseForge 3300 X2 photonic 6 curing system manufactured by NovaCentrix in Austin, Texas). The settings on the photonic curing apparatus used for curing were 540 V, 1,100 ms, overlap factor of 4, at a 8 web speed of 14 feet per minute. Photonic curing reduced the sheet resistance of the nickel 9 film on the paper substrate to 550 mS2/III.
11 The porous nickel thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 13 of 2,464 lbf to the porous nickel thin films on paper as they were drawn through the rollers. The cross-sectional area of compression was 0.074 in2, yielding an average 33,300 psi applied to the printed conductors. Densification, via compression, of the porous nickel reduced the sheet resistance to 60 m52/111. Compressing the porous nickel decreased its 17 resistivity by 89%.
19 Example 3: Compressive stress applied to thin films of silver on paper substrates A screen printable version of a silver flake ink (part no. HPS-03OLV
available from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index 22 paper with a 230 mesh flat screen. The print was dried in a 170 C oven for 5 minutes to 23 remove excess solvents and cause sintering of the silver flakes. After oven drying the sheet 24 resistance measured 16.9 mf2/111.
26 The 5 micron thick silver trace on paper substrate underwent densification 27 via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force of 1,848 lbf to the silver thin Elms on paper as they were drawn through 29 the rollers. The cross sectional area of compression was 0.074 in2, yielding an average 24,970 psi applied to the printed conductors. Densification, via compression, of the silver reduced the sheet resistance to 14.2 m2'E1. Compressing the silver film decreased the 2 resistivity by 16%.
Example 4: Compressive stress applied to thin films of mesoporous copper on PET
substrates screen printable version of a copper oxide reduction ink (part no. ICI-021 available from NovaCentrix in Austin, Texas) was printed on ST505 polyethylene terephthalate (PET) film with a 230 mesh flat screen. The print was then dried in a 140 C
9 oven for 5 minutes to remove excess solvents. Initially, the ink had a sheet resistance that was ¨IGO/E . That is, the resistance as measured by an ordinary multimeter was an open 11 circuit.
13 The ink was converted to a conductive mesoporous copper thin film using 14 a photonic curing apparatus (PulseForge 3300 X2 photonic curing system manufactured by NovaCentrix in Austin, Texas). The settings on the machine used for curing were 360 16 V, 2,500 ms, overlap factor of 1, and at a web speed of 16 feet per minute. The sheet 17 resistance after photonic curing was 46 inf2/0.
19 The mesoporous copper thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 21 of 1,027 lbf to the foamed copper thin film on paper as it was drawn through the rollers.
22 The cross sectional area of compression was 0.074 in2, yielding an average 13,873 psi applied to the printed conductors. Densification, via compression, of the mesoporous 24 copper reduced the average sheet resistance to 34 mS2/0. Thus, compressing the mesoporous copper decreased its resistivity by 26% and reduced its surface roughness.
27 The pressure applied to the thin films of mesoporous copper on PET was 28 nearly half the pressure used in Example 1. This was done to preserve the copper film due 29 to the tendency of PET to deform laterally at pressures exceeding its yield pressure of 15,000 psi.
1 When compressive stress is applied only to the printed areas of a thin film 2 (i.e., not the entire thin film and substrate), significantly higher pressures (greater than the 3 yield pressure of the substrate such as PET) may be applied to the thin film of mesoporous 4 copper and nonporous PET substrate to increase the density and electrical conductivity of the thin film. The limitation of rolling compression at pressures greater than the yield 6 pressure of the nonporous substrate is removed as lateral deformation local to the thin film 7 conductor does not disrupt the thin film conductor's contiguity, where complete areal 8 compression does. This type of area specific compression of printed circuits may be 9 accomplished through the use of a stamping tool such as an embossed roller. The embossed roller may have a raised pattern matching the printed circuit pattern and would 11 contact and compress only in the printed regions on the substrate, leaving the majority of 12 substrate uncompressed. Generally, this technique is useful for printed depositions covering 13 less than 50% of the substrate. As the percentage of deposition area increases to 100%, the 14 area specific compression tends to behave more like rolling compression where the entire web of substrate is compressed, thus forfeiting the advantage.
17 As has been described, the present invention provides a method for forming 18 thin film conductors on a substrate.
While the invention has been particularly shown and described with reference 21 to a preferred embodiment, it will be understood by those skilled in the art that various 22 changes in form and detail may be made therein without departing from the spirit and scope 23 of the invention.
16 Strobe head 220 includes a high-intensity xenon flashlamp 221 for curing 17 thin film precursor material 202 located on substrate 203. Xenon flashlamp 221 can provide pulses of different intensity, pulse length, and pulse repetition frequency. For example, xenon flashlamp 221 can provide 10 ,as to 10 ms pulses with a 3" by 6" wide footprint at a pulse repetition rate of up to 1 kHz. The spectral content of the emissions 21 from xenon flashlamp 221 ranges from 200 nm to 2,500 nm. The spectrum can be adjusted 22 by replacing the quartz lamp with a ceria doped quartz lamp to remove most of the emission below 350 nm. The quartz lamp can also be replaced with a sapphire lamp to 24 extend the emission from approximately 140 nm to approximately 4,500 nm. Xenon flashlamp 221 can also be a water wall flash lamp that is sometimes referred to as a 26 Directed Plasma Arc (DPA) lamp.
28 Relay rack 230 includes an adjustable power supply, a conveyance control module, and a strobe control module. The adjustable power supply can produce pulses with energy of up to 4 kJ per pulse. Adjustable power supply is connected to xenon flashlamp 1 221, and the intensity of the emission from xenon flashlamp 221 can be varied by 2 controlling the amount of current passing through xenon flashlamp 221.
4 The adjustable power supply controls the emission intensity of xenon flashlamp 221. The power, pulse duration, and pulse repetition frequency of the emission 6 from xenon flashlamp 221 are electronically adjusted in real time and synchronized to the 7 web speed to allow optimum curing of thin film precursor material 202 without damaging 8 substrate 203, depending on the optical, thermal, and geometric properties of thin film 9 precursor material 202 and substrate 203. Preferably, the time duration of irradiation of each light pulse is less than the time to thermal equilibration time of the stack comprising 11 thin film precursor material 202 on substrate 203.
13 During the irradiation with light pulses, substrate 203 as well as thin film 14 precursor material 202 is being moved by conveyor system 210. Conveyor system 210 moves thin film precursor material 202 under strobe head 220 where thin film precursor 16 material 202 is cured by rapid light pulses from xenon flashlamp 221.
The power, 17 duration, and repetition rate of the emissions from xenon flashlamp 221 are controlled by 18 the strobe control module, and the speed at which substrate 203 is being moved past strobe 19 head 220 is determined by the conveyor control module.
21 When xenon flashlamp 221 is emitting light pulses, thin film precursor 22 material 202 is momentarily heated to provide the energy for curing thin film precursor 23 material 202. When a rapid pulse train is synchronized to moving substrate 203, a uniform 24 cure can be attained over an arbitrarily large area as each section of thin film precursor material 202 may be exposed to multiple light pulses, which approximates a continuous 26 curing system such as an oven.
28 C. Compressing processed material 29 After thin film precursor material 202 located on substrate 203 has been photonically cured with flashlamp 221 to form a thin film material 202', compressive stress 1 is applied to thin film material 202' and substrate 203 in order to densify thin film material 2 202 and substrate 203. Thin film material 202' on substrate 203 can be compressed by one 3 or combinations of existing technologies such as stamping, forging, rolling, calendering, 4 pressing, embossing, laminating, etc.
6 Rolling is preferably used in a reel-to-reel manufacturing setting by a set of 7 pinch rollers 260. Pinch rollers 260 are loaded, in compression, such that the peak pressure 8 applied to thin film material 202' and substrate 203 exceeds 25% of the ultimate tensile 9 strength (UTS) of the bulk thin film material after photonic curing at standard conditions.
For a relatively soft and ductile metal like copper, the preferred compression pressure range ii is between 7,500 and 30,000 psi (i.e., 25% to 100% of its ultimate tensile strength at 12 standard conditions).
14 Because substrate 203 is porous, it is compressible and responds to compression by reducing in thickness while keeping the same width, such as a fiber based 16 substrate like paper. This single dimensional change ensures that thin film material 202' 17 is not damaged by lateral deformation of substrate 203. The peak pressure capable of being 18 applied by pinch rollers 260 to polymer substrates that are non-porous, such as PET, may 19 be limited because PET is a low-temperature polymer that tends to be relatively soft. PET
will deform laterally at a lower pressure threshold than other substrates, which can cause 21 damage to thin film material 202' and substrate 203.
23 Pinch rollers 260 are driven at angular velocity co = v/r, where a) is the 24 angular velocity of pinch rollers 260 and r is the radius of pinch rollers 260, adjusted, and synchronized to the web speed, v, to allow optimum densification of thin film material 202' 26 without damaging substrate 203, depending on the mechanical and geometric properties of 27 thin film material 202' and substrate 203.
29 In certain situations, it may be advantageous to apply dynamic compressive stress (oscillating magnitude over time) with pinch rollers 260, driven at a certain - s -1 frequency, to thin film material 202' on substrate 203 to achieve high peak pressures with 2 a lower average force on pinch rollers 260 to extend tool lifetime and/or increase maximum 3 web speeds.
Heating pinch rollers 260 to a temperature between standard temperature and 6 the maximum working temperature of substrate 203 can decrease the required pressure to 7 achieve a similar result with standard temperature pinch rollers 260 due to the softening of 8 thin film material 202' during compression.
Compressive stress applied to thin film material 202' deposited on substrate 11 203 can increase the density of thin film material 202'. A particle or solution-based 12 deposited material has a density lower than the bulk precursor material due to a residual 13 pore structure within the deposited layer. Additionally, the photonic curing process may 14 introduce additional porosity in thin film material 202'. The volume of pore space relative to layer volume (volume fraction) will vary depending on material, process, and particle 16 size. Reducing the pore space volume fraction densifies the material improving its 17 performance in teaus of increased electrical conductivity if it is conductive, improved 18 mechanical stability and hardness, alters the surface properties like reducing surface 19 roughness and improving solder-ability, and improved chemical resistance if the material is prone to corrosion by reducing the surface area to volume ratio.
Compressing thin film 21 material 202' increases it density, which brings deposited thin film material 202' closer to 22 the properties of the bulk thin film material.
24 The following examples illustrate various methods of applying compressive stress to thin film materials located on a substrate. The results of compressive stress are 26 densification of thin film material on the substrate such that conductivity, mechanical 27 stability, and chemical resistance of the thin film material are improved.
Example 1: Compressive stress applied to thin films of mesoporous copper on paper 2 substrates screen printable version of a copper oxide reduction ink (part no. ICI-021 available from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index paper with a 230 mesh flat screen. The print was then dried in a 140 C oven for 5 minutes 6 to remove excess solvents. Initially, the ink had a sheet resistance that was ¨1 GQ/111.
7 That is, the resistance as measured by an ordinary multimeter was an open circuit.
9 The ink was converted to a conductive mesoporous copper thin film using a photonic curing apparatus (such as PulseForge 3300 X2 photonic curing system manufactured by NovaCentrix in Austin, Texas). The settings on the machine used for 12 curing were 430 V, 1,600 ms, overlap factor of 5, and at a web speed of 16 feet per 13 minute. The sheet resistance after photonic curing was 17.2 mK2/111.
The mesoporous copper thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 17 of 2,875 lbf to the foamed copper thin film on paper as it was drawn through the rollers.
18 The cross sectional area of compression was 0.074 in', yielding an average 38,850 psi applied to the printed conductors. Densification, via compression, of the mesoporous copper reduced the sheet resistance to 9.3 mf2/ EL Thus, compressing the mesoporous 21 copper decreased its resistivity by 46%.
Additional benefits to the overall perfoimance of the compressed copper 24 film, besides improved electrical conductivity, became apparent during surface mounted device (SMD) attachment evaluation, mechanical stability testing, and environmental 26 testing.
Compressed copper has demonstrated a significantly improved success rate 29 of attaching SMD components over as-converted mesoporous copper. The failure rate was 50% for thermode bonded SIVID silicon chips to the mesoporous copper.
Compressed -io-1 copper demonstrated a much higher success rate of 90% due to its low surface roughness.
Additionally, the reduced surface roughness alters the optical properties of the converted 3 copper from matte to nearly specular reflectivity at high pressures.
Referring now to Figure 3, there is illustrated a graph showing a height profile of foamed copper on paper before and after compression. Both the total height and 7 the surface roughness are reduced indicating increased density and reduced surface roughness of the copper film. Specifically, the surface roughness was reduced from 25 9 micron to 5 microns. The entire thin film stack was reduced in thickness by about 50 microns.
12 For copper on paper, there is a saturation point for what pressures improve 13 the electrical conductivity below the UTS of pure copper. As-converted mesoporous copper measured about 30 mn/111 in sheet resistance. Mesoporous copper film compressed at 8,300 psi (27% UTS of pure copper) measured 22 m52/111 in sheet resistance. At a pressure 16 of 12,000 psi (40% UTS of pure copper) the sheet resistance reached a minimum value of mS2/ El (saturation point). Further increasing the applied pressure to 25,000 psi (83%
18 UTS of pure copper) saw no improvement on the sheet resistance of the copper films.
However, when tracking the conductivity over time it was observed that copper films compressed at 12,000 psi gained in sheet resistance by 20% over 40 days in air. The 21 copper films compressed at 25,000 psi only gained in sheet resistance by 5% over 40 days 22 in air. Therefore, pressures beyond 40% UTS of pure copper (12,000 psi) are required for 23 corrosion resistance and stability over time for the copper thin film.
Even though increasing the applied stress by 2x did not improve the electrical conductivity of the films, the stability was greatly improved. This means that the 27 pore space volume fraction was reduced with the increased pressure (25,000 psi) and/or the 28 copper material was completely yielded and did not "spring back" like the films compressed 29 at half the pressure. The spring back effect is commonly seen in traditional sheet metal forming. In a manufacturing environment, in order to reduce a piece of sheet metal in 1 gauge, the material must be compressed or rolled through multiple stages. A single stage 2 gauge reduction is not useful due to the metal's tendency to expand in thickness after being reduced because of the elastic deformation component of the process. In this case, the 4 foamed copper compressed at 80% UTS yields completely and prevents residual elastic stress from degrading overall performance and stability of the compressed film.
7 After photonic curing, the converted mesoporous copper has a high surface 8 area to volume ratio contributing to its poor native corrosion resistance.
Compressing the mesoporous copper greatly reduces the surface area to volume ratio of the copper and improves the material's corrosion resistance. Environmental testing was perfolmed on bare 11 as-converted and compressed copper films on paper substrate. Compressed copper demonstrates a significantly improved corrosion resistance when tested in an environment 13 at 85 C/100% relative humidity for 24 hours. Uncoated mesoporous copper on paper does 14 not survive such an environmental test, but compressed copper survives un-coated and without a detectable change in conductivity. Uncoated compressed copper films passed an industry standard (1,000 hours at 85 C/85% relative humidity) with only an increase in resistivity by 20%. Additional cost benefits pertaining to production become apparent as required volumes of materials for encapsulating the compressed copper films are decreased 19 relative to as-converted copper.
21 When it is desirable to only reduce the surface roughness of the thin film, significantly lower pressure may be used. As-cured films of mesoporous copper on paper substrate exhibiting average surface roughness of 5 microns were compressed at 2,600 psi 24 (9%
UTS of pure copper) reducing the average surface roughness to 2 microns. At this pressure, the electrical conductivity of the mesoporous copper films was unchanged.
Example 2: Compressive stress applied to porous thin films of nickel on paper substrates screen printable version of a nickel flake ink (part no. 79-89-16 available 29 from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index paper with a 230 mesh flat screen. The prints were dried in a 150 C oven for 5 minutes to remove 2 excess solvents. After oven drying the sheet resistance measured 77 Q/171.
4 The dried ink was photonically cured to form a highly conductive porous nickel thin film using a photonic curing apparatus (such as PulseForge 3300 X2 photonic 6 curing system manufactured by NovaCentrix in Austin, Texas). The settings on the photonic curing apparatus used for curing were 540 V, 1,100 ms, overlap factor of 4, at a 8 web speed of 14 feet per minute. Photonic curing reduced the sheet resistance of the nickel 9 film on the paper substrate to 550 mS2/III.
11 The porous nickel thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 13 of 2,464 lbf to the porous nickel thin films on paper as they were drawn through the rollers. The cross-sectional area of compression was 0.074 in2, yielding an average 33,300 psi applied to the printed conductors. Densification, via compression, of the porous nickel reduced the sheet resistance to 60 m52/111. Compressing the porous nickel decreased its 17 resistivity by 89%.
19 Example 3: Compressive stress applied to thin films of silver on paper substrates A screen printable version of a silver flake ink (part no. HPS-03OLV
available from NovaCentrix in Austin, Texas) was printed on Wausau 110 lb exact index 22 paper with a 230 mesh flat screen. The print was dried in a 170 C oven for 5 minutes to 23 remove excess solvents and cause sintering of the silver flakes. After oven drying the sheet 24 resistance measured 16.9 mf2/111.
26 The 5 micron thick silver trace on paper substrate underwent densification 27 via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force of 1,848 lbf to the silver thin Elms on paper as they were drawn through 29 the rollers. The cross sectional area of compression was 0.074 in2, yielding an average 24,970 psi applied to the printed conductors. Densification, via compression, of the silver reduced the sheet resistance to 14.2 m2'E1. Compressing the silver film decreased the 2 resistivity by 16%.
Example 4: Compressive stress applied to thin films of mesoporous copper on PET
substrates screen printable version of a copper oxide reduction ink (part no. ICI-021 available from NovaCentrix in Austin, Texas) was printed on ST505 polyethylene terephthalate (PET) film with a 230 mesh flat screen. The print was then dried in a 140 C
9 oven for 5 minutes to remove excess solvents. Initially, the ink had a sheet resistance that was ¨IGO/E . That is, the resistance as measured by an ordinary multimeter was an open 11 circuit.
13 The ink was converted to a conductive mesoporous copper thin film using 14 a photonic curing apparatus (PulseForge 3300 X2 photonic curing system manufactured by NovaCentrix in Austin, Texas). The settings on the machine used for curing were 360 16 V, 2,500 ms, overlap factor of 1, and at a web speed of 16 feet per minute. The sheet 17 resistance after photonic curing was 46 inf2/0.
19 The mesoporous copper thin film underwent densification via the following process: A pair of steel rollers (1.7" diameter x 3.0" length) applied a compressive force 21 of 1,027 lbf to the foamed copper thin film on paper as it was drawn through the rollers.
22 The cross sectional area of compression was 0.074 in2, yielding an average 13,873 psi applied to the printed conductors. Densification, via compression, of the mesoporous 24 copper reduced the average sheet resistance to 34 mS2/0. Thus, compressing the mesoporous copper decreased its resistivity by 26% and reduced its surface roughness.
27 The pressure applied to the thin films of mesoporous copper on PET was 28 nearly half the pressure used in Example 1. This was done to preserve the copper film due 29 to the tendency of PET to deform laterally at pressures exceeding its yield pressure of 15,000 psi.
1 When compressive stress is applied only to the printed areas of a thin film 2 (i.e., not the entire thin film and substrate), significantly higher pressures (greater than the 3 yield pressure of the substrate such as PET) may be applied to the thin film of mesoporous 4 copper and nonporous PET substrate to increase the density and electrical conductivity of the thin film. The limitation of rolling compression at pressures greater than the yield 6 pressure of the nonporous substrate is removed as lateral deformation local to the thin film 7 conductor does not disrupt the thin film conductor's contiguity, where complete areal 8 compression does. This type of area specific compression of printed circuits may be 9 accomplished through the use of a stamping tool such as an embossed roller. The embossed roller may have a raised pattern matching the printed circuit pattern and would 11 contact and compress only in the printed regions on the substrate, leaving the majority of 12 substrate uncompressed. Generally, this technique is useful for printed depositions covering 13 less than 50% of the substrate. As the percentage of deposition area increases to 100%, the 14 area specific compression tends to behave more like rolling compression where the entire web of substrate is compressed, thus forfeiting the advantage.
17 As has been described, the present invention provides a method for forming 18 thin film conductors on a substrate.
While the invention has been particularly shown and described with reference 21 to a preferred embodiment, it will be understood by those skilled in the art that various 22 changes in form and detail may be made therein without departing from the spirit and scope 23 of the invention.
Claims (14)
1. A method for forming a thin film conductor on a substrate, said method comprising:
depositing a thin film precursor material onto a porous substrate;
irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate by a pair of pinch rollers to further increase said thin film's electrical conductivity, wherein said pinch rollers are driven at .omega.=v/r, where co is an angular velocity of said pinch rollers, r is a radius of said pinch rollers, and v is a moving speed of said thin film.
depositing a thin film precursor material onto a porous substrate;
irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate by a pair of pinch rollers to further increase said thin film's electrical conductivity, wherein said pinch rollers are driven at .omega.=v/r, where co is an angular velocity of said pinch rollers, r is a radius of said pinch rollers, and v is a moving speed of said thin film.
2. The method of claim 1, wherein said depositing is performed by printing.
3. The method of claim 1, wherein said porous substrate is paper.
4. The method of claim 1, wherein said porous substrate is polymer.
5. The method of claim 1, wherein said applying compressive stress is accomplished by rolling or calendaring.
6. The method of claim 1, wherein said compressive stress exceeds 25% of the ultimate tensile strength of said thin film at standard temperature and pressure.
7. The method of claim 1, wherein said depositing is performing by chemical vapor deposition.
8. The method of claim 1, wherein said thin film precursor material includes a particulate metal.
9. The method of claim 8, wherein said particulate metal is a metal selected from the group consisting of copper, nickel, cobalt, silver and combinations thereof.
10. The method of claim 1, wherein said thin film precursor material includes a particulate metal oxide and a reducing agent.
11. The method of claim 1, wherein said thin film precursor material includes a metal salt and a reducing agent.
12. A method for forming a thin film conductor on a substrate, said method comprising:
depositing a thin film precursor material onto a porous substrate;
irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate to further increase said thin film's electrical conductivity, wherein said applying of compressive stress oscillates in magnitude with time.
depositing a thin film precursor material onto a porous substrate;
irradiating said thin film precursor material with a light pulse to transform said thin film precursor material to a thin film, wherein said thin film is more electrically conductive than said thin film precursor material; and applying compressive stress to said thin film and said porous substrate to further increase said thin film's electrical conductivity, wherein said applying of compressive stress oscillates in magnitude with time.
13. The method of claim 12, wherein said depositing is performing by chemical vapor deposition.
14. The method of claim 12, wherein said applying compressive stress is accomplished by rolling.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2012/067607 WO2014088546A1 (en) | 2012-12-03 | 2012-12-03 | Method for forming thin film conductors on a substrate |
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| CA2893584A1 CA2893584A1 (en) | 2014-06-12 |
| CA2893584C true CA2893584C (en) | 2019-05-21 |
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| CA2893584A Active CA2893584C (en) | 2012-12-03 | 2012-12-03 | Method for forming thin film conductors on a substrate |
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| EP (1) | EP2926367A4 (en) |
| JP (1) | JP6202763B2 (en) |
| CA (1) | CA2893584C (en) |
| WO (1) | WO2014088546A1 (en) |
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| CN107113974B (en) * | 2015-01-06 | 2019-09-06 | 株式会社藤仓 | The manufacturing method and circuit board of conductor layer |
| JP2016171051A (en) * | 2015-03-16 | 2016-09-23 | Ｄｏｗａエレクトロニクス株式会社 | Conductive film and manufacturing method thereof |
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| US5311027A (en) * | 1993-02-26 | 1994-05-10 | Raychem Corporation | Apparatus and method for uniformly irradiating a strand |
| US6257133B1 (en) * | 1999-03-15 | 2001-07-10 | International Paper | Method and apparatus for controlling cross directional nip dynamics |
| JP2001064547A (en) * | 1999-09-01 | 2001-03-13 | Toyo Ink Mfg Co Ltd | Active energy ray-curable electroconductive paste, and conductor circuit and non-contact id using the same |
| US20040185388A1 (en) * | 2003-01-29 | 2004-09-23 | Hiroyuki Hirai | Printed circuit board, method for producing same, and ink therefor |
| JP4858057B2 (en) * | 2006-09-29 | 2012-01-18 | 大日本印刷株式会社 | Method for manufacturing conductive substrate |
| US10231344B2 (en) * | 2007-05-18 | 2019-03-12 | Applied Nanotech Holdings, Inc. | Metallic ink |
| DE102007051930A1 (en) * | 2007-10-29 | 2009-04-30 | Leonhard Kurz Gmbh & Co. Kg | Method for producing a printed conductor structure |
| US9564629B2 (en) * | 2008-01-02 | 2017-02-07 | Nanotek Instruments, Inc. | Hybrid nano-filament anode compositions for lithium ion batteries |
| US7960027B2 (en) * | 2008-01-28 | 2011-06-14 | Honeywell International Inc. | Transparent conductors and methods for fabricating transparent conductors |
| CN101939798A (en) * | 2008-02-13 | 2011-01-05 | 住友金属矿山株式会社 | Flexible transparent conductive film, flexible functional device, and methods for producing these |
| US20100231672A1 (en) * | 2009-03-12 | 2010-09-16 | Margaret Joyce | Method of improving the electrical conductivity of a conductive ink trace pattern and system therefor |
| KR20120018329A (en) * | 2009-04-21 | 2012-03-02 | 몰렉스 인코포레이티드 | Three dimensional antenna |
| US8328987B2 (en) * | 2009-09-01 | 2012-12-11 | Armstrong World Industries, Inc. | Process of making a wet formed cellulosic product and a wet formed cellulosic product |
| CN102648669B (en) * | 2009-10-27 | 2016-04-20 | 松下知识产权经营株式会社 | Conductive pattern forms the formation method of base material and conductive pattern formation base material |
| US8907258B2 (en) * | 2010-04-08 | 2014-12-09 | Ncc Nano, Llc | Apparatus for providing transient thermal profile processing on a moving substrate |
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- 2012-12-03 CA CA2893584A patent/CA2893584C/en active Active
- 2012-12-03 WO PCT/US2012/067607 patent/WO2014088546A1/en active Application Filing
- 2012-12-03 EP EP12889427.6A patent/EP2926367A4/en not_active Withdrawn
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Also Published As
| Publication number | Publication date |
|---|---|
| WO2014088546A1 (en) | 2014-06-12 |
| JP2016501431A (en) | 2016-01-18 |
| JP6202763B2 (en) | 2017-09-27 |
| EP2926367A4 (en) | 2016-07-27 |
| EP2926367A1 (en) | 2015-10-07 |
| CA2893584A1 (en) | 2014-06-12 |
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