CN116406076A - Low-temperature-cured copper-based conductive paste for screen printing and preparation method thereof - Google Patents
Low-temperature-cured copper-based conductive paste for screen printing and preparation method thereof Download PDFInfo
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 135
- 239000010949 copper Substances 0.000 title claims abstract description 88
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 87
- 238000007650 screen-printing Methods 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title abstract description 7
- 239000000843 powder Substances 0.000 claims abstract description 89
- 239000000956 alloy Substances 0.000 claims abstract description 81
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 81
- 238000013035 low temperature curing Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 6
- 238000007711 solidification Methods 0.000 claims abstract description 5
- 230000008023 solidification Effects 0.000 claims abstract description 5
- 230000008569 process Effects 0.000 claims abstract description 4
- 238000001723 curing Methods 0.000 claims description 24
- 239000003795 chemical substances by application Substances 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 12
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical group OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 10
- 239000011259 mixed solution Substances 0.000 claims description 10
- 239000001856 Ethyl cellulose Substances 0.000 claims description 9
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical group CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 claims description 9
- 229920001249 ethyl cellulose Polymers 0.000 claims description 9
- 235000019325 ethyl cellulose Nutrition 0.000 claims description 9
- 239000011230 binding agent Substances 0.000 claims description 8
- 239000003638 chemical reducing agent Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 7
- 239000002562 thickening agent Substances 0.000 claims description 7
- 239000002518 antifoaming agent Substances 0.000 claims description 6
- 239000007822 coupling agent Substances 0.000 claims description 6
- 239000003822 epoxy resin Substances 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 229920000647 polyepoxide Polymers 0.000 claims description 6
- 229920005989 resin Polymers 0.000 claims description 6
- 239000011347 resin Substances 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 239000013008 thixotropic agent Substances 0.000 claims description 6
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical group OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 239000012752 auxiliary agent Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 2
- 229920002433 Vinyl chloride-vinyl acetate copolymer Polymers 0.000 claims description 2
- 229960004543 anhydrous citric acid Drugs 0.000 claims description 2
- 235000010323 ascorbic acid Nutrition 0.000 claims description 2
- 229960005070 ascorbic acid Drugs 0.000 claims description 2
- 239000011668 ascorbic acid Substances 0.000 claims description 2
- 235000019253 formic acid Nutrition 0.000 claims description 2
- 238000005303 weighing Methods 0.000 claims description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 claims 1
- 230000003014 reinforcing effect Effects 0.000 abstract description 10
- 230000001988 toxicity Effects 0.000 abstract 1
- 231100000419 toxicity Toxicity 0.000 abstract 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 8
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 8
- 239000011521 glass Substances 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 229910052709 silver Inorganic materials 0.000 description 8
- 239000004332 silver Substances 0.000 description 8
- 239000004593 Epoxy Substances 0.000 description 6
- 238000007639 printing Methods 0.000 description 5
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical group CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 description 4
- ULKLGIFJWFIQFF-UHFFFAOYSA-N 5K8XI641G3 Chemical group CCC1=NC=C(C)N1 ULKLGIFJWFIQFF-UHFFFAOYSA-N 0.000 description 4
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000523 sample Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- STCOOQWBFONSKY-UHFFFAOYSA-N tributyl phosphate Chemical group CCCCOP(=O)(OCCCC)OCCCC STCOOQWBFONSKY-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000002482 conductive additive Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000004513 sizing Methods 0.000 description 2
- DOVZUKKPYKRVIK-UHFFFAOYSA-N 1-methoxypropan-2-yl propanoate Chemical compound CCC(=O)OC(C)COC DOVZUKKPYKRVIK-UHFFFAOYSA-N 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000005215 alkyl ethers Chemical class 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
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 125000003055 glycidyl group Chemical group C(C1CO1)* 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
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Classifications
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- 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
- 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
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
-
- 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
- H05K3/1216—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 by screen printing or stencil printing
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Conductive Materials (AREA)
Abstract
The invention discloses a low-temperature curing copper-based conductive paste for screen printing and a preparation method thereof, wherein the paste comprises a conductive phase, a bonding phase and an organic carrier, and the conductive phase comprises a mixture of copper powder and Sn42Bi58 low-melting-point alloy powder; the Sn42Bi58 low-melting-point alloy powder is melted and filled in gaps of copper powder in the solidification process of the copper-based conductive paste and coated on the surface of the copper powder to form a three-dimensional conductive path; the copper powder accounts for 45-75% of the total weight of the copper-based conductive paste in percentage by weight; the Sn42Bi58 low-melting-point alloy powder accounts for 10-40% of the total weight of the copper-based conductive paste in percentage by weight. The Sn42Bi58 low-melting-point alloy powder is used as the reinforcing phase, and the paste has excellent conductive performance and mechanical property at the low-temperature curing temperature of 150-190 ℃, is lead-free and halogen-free, is environment-friendly and low in toxicity, has good wettability and leveling property, is uniformly printed, and has wide application prospect.
Description
Technical Field
The invention relates to a conductive paste and a preparation method thereof, in particular to a low-temperature curing copper-based conductive paste for screen printing and a preparation method thereof.
Background
With the rapid development of the electronic information industry and the photovoltaic industry, the low-temperature curing slurry can greatly reduce the curing temperature, and is widely applied to the fields of photovoltaic cells, integrated circuits, flexible membrane switches, touch screens, electrode leads and the like. Among common metal elements such as gold, silver, copper, iron, aluminum and the like, silver has the advantages of lowest resistivity, highest heat conductivity, high oxidation resistance and the like, so that low-temperature curing silver paste is the mainstream applied to the market. However, along with the continuous increase of international silver price and the easy generation of electron migration of silver under the action of an electric field, the development of novel low-cost conductive paste has become a new hot spot.
Copper is low in price, the resistivity and the heat conductivity are only inferior to those of silver, the resistivity of silver is 1.586 mu omega-cm, the heat conductivity is 429W/m-K, the resistivity of copper is 1.678 mu omega-cm, the heat conductivity is 401W/m-K, and the copper is not easy to generate electromigration phenomenon, so that the copper is one of the most promising materials for replacing silver or other noble metal slurry in electronic device application.
The invention patent with publication number of CN110428926B discloses a copper-based composite conductive paste, a preparation method and application thereof, wherein the copper conductive paste comprises the following components in percentage by weight: 65-85% of conductive phase, 6-12% of bonding phase and 3-8% of organic carrier, wherein the conductive phase comprises 63-90% of spherical Cu powder and the balance of SnAgCu alloy powder by mass. However, the scheme has the defect of overhigh solidifying temperature, and because the melting point of the SnAgCu alloy powder is 217 ℃, the solidifying temperature of the copper-based conductive paste prepared by the scheme is more than 217 ℃, and at the moment, the used binding phase epoxy resin can slowly decompose pungent and harmful substances, and can also cause bubbles to be generated in the solidifying process of the copper paste, so that the conductivity and mechanical properties of the copper paste are affected.
Disclosure of Invention
The invention aims to: the invention aims to provide low-temperature cured copper-based conductive paste for screen printing, which has excellent conductive performance and mechanical property;
a second object of the present invention is to provide a method for preparing the above-mentioned low-temperature-curable copper-based conductive paste for screen printing.
The technical scheme is as follows: the low-temperature curing copper-based conductive paste for screen printing comprises a conductive phase, a bonding phase and an organic carrier, wherein the conductive phase material comprises a mixture of copper powder and Sn42Bi58 low-melting-point alloy powder; the Sn42Bi58 low-melting-point alloy powder is filled in gaps of copper powder in a melting mode in the solidification process of the copper-based conductive paste and is coated on the surface of the copper powder to form a three-dimensional conductive path; the copper powder accounts for 45-75% of the total weight of the copper-based conductive paste in percentage by weight; the Sn42Bi58 low-melting-point alloy powder accounts for 10-40% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the curing temperature of the copper-based conductive paste is 150-190 ℃.
Wherein, the particle shape of the Sn42Bi58 low-melting-point alloy powder is flaky, and the average size is 5-15 mu m; or the particle shape of the Sn42Bi58 low-melting-point alloy powder is spherical, and the diameter is 15-30 mu m; the thickness of the Sn42Bi58 low-melting-point alloy powder is preferably 300-600nm.
Wherein the particle shape of the copper powder is flaky, and the average size is 1-5 mu m; the thickness is 50-100nm, more preferably 80-100nm.
Wherein the bonding phase is one or two of bisphenol A type epoxy resin E51, F51 and vinyl chloride-vinyl acetate copolymer; the content of the copper-based conductive paste is 4-10% of the total weight of the copper-based conductive paste by weight percentage.
Wherein the organic carrier comprises a solvent, a curing agent, an accelerator, a thickener, a thixotropic agent, a leveling agent, a defoaming agent, a conductive auxiliary agent, a coupling agent and a reducing agent.
Wherein the solvent is one or more of cyclohexanone, propylene glycol methyl ether propionate, glycidyl 12-14 alkyl ether and diethyl carbonate, and the content of the solvent is 8-20% of the total weight of the copper-based conductive paste, preferably 11-15% by weight.
Wherein the curing agent is triethanolamine, and the content of the curing agent is 0.6-1.3% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the accelerator is 2-ethyl-4-methylimidazole, and the content of the accelerator is 0.05-0.09% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the thickener is ethyl cellulose, and the content of the thickener is 0.6-1.3% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the thixotropic agent is BYK-410, and the content of the thixotropic agent is 0.2-0.5% of the total weight of the copper-based conductive paste by weight percent
Wherein the leveling agent is BYK-333, and the content of the leveling agent is 0.1-0.2% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the defoaming agent is tributyl phosphate, and the content of the defoaming agent is 0.3-0.6% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the conductive additive is BYK ES-80, and the content of the conductive additive is 0.2-0.5% of the total weight of the copper-based conductive paste by weight percentage.
Wherein the coupling agent is 3-triethoxysilyl-1-propylamine, and the content of the coupling agent is 0.35-0.75% of the total weight of the copper-based conductive paste in percentage by weight.
Wherein the reducing agent is anhydrous oxalic acid, ascorbic acid or anhydrous citric acid, and the content of the reducing agent is 0.25-0.45% of the total weight of the copper-based conductive paste in percentage by weight.
The preparation method of the low-temperature curing copper-based conductive paste for screen printing comprises the following steps:
(1) Weighing binder phase resin and solvent with corresponding mass until the binder phase resin is completely dissolved;
(2) Sequentially adding a thickening agent, a curing agent, an accelerator, a thixotropic agent, a leveling agent, a conductive auxiliary agent, a defoaming agent, a coupling agent and a reducing agent into the solution obtained in the step (1), and fully stirring and mixing to obtain a mixed solution;
(3) Uniformly mixing copper powder and Sn42Bi58 alloy powder to obtain a conductive phase;
(4) Adding the conductive phase obtained in the step (3) into the mixed solution obtained in the step (2), and grinding to obtain the low-temperature cured copper-based conductive paste for screen printing;
wherein, the copper powder in the step (3) is washed with dilute sulfuric acid or formic acid absolute ethanol solution before being mixed with Sn42Bi58 alloy powder, dispersed with absolute ethanol and dried.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable effects: (1) Compared with spherical low-melting-point alloy powder, the flaky Sn42Bi58 low-melting-point alloy powder has larger specific surface area, so that the flaky Sn42Bi58 low-melting-point alloy powder is easier to coat flaky copper powder after being heated and melted, a three-dimensional net-shaped three-dimensional structure is formed in the conductive paste, the conductive path of the three-dimensional net-shaped three-dimensional structure is increased, and the conductivity and mechanical property of the copper paste are further enhanced. (2) The invention uses Sn42Bi58 low-melting-point alloy powder as a reinforcing phase, the melting point is 138 ℃, bisphenol A type epoxy resin E51 is used as a bonding phase, and the prepared conductive paste can be solidified at a low temperature of 150-190 ℃. (3) According to the invention, the rheological properties of the sizing agent are regulated and controlled by using organic aids such as ethyl cellulose, BYK-410 and BYK-333, and after the sizing agent is printed on a glass slide by a screen printing method, the printed image has less burrs and uniform morphology, and has an excellent printing effect.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a low temperature cured copper-based conductive paste according to the present invention;
FIG. 2 is a golden phase diagram of the sample of example 1 after curing;
FIG. 3 is a surface scan and elemental surface profile of the cured conductive copper paste of examples 1, 4, 5, and 6;
FIG. 4 is a cross-sectional scan of the cured conductive copper paste of examples 1, 4, 5, and 6;
fig. 5 is a scan of Sn42Bi58 alloy powders of examples 1, 4, 5, and 6.
Detailed Description
The present invention is described in further detail below.
Example 1
(1) 7.48g of epoxy E51 and 14.97g of cyclohexanone are mixed, heated in a water bath at 50 ℃ for 20min and magnetically stirred until the epoxy E51 is fully dissolved, and then 1.13g of ethylcellulose powder is added and magnetically stirred for 30min.
(2) After the ethylcellulose powder was sufficiently dissolved, 1.13g of triethanolamine, 0.07g of 2-ethyl-4-methylimidazole, 0.19g of BYK-410,0.09g of BYK-333,0.19g of BYK ES-80,0.47g of tributyl phosphate, 0.60g of 3-triethoxysilyl-1-propylamine, and 0.38g of anhydrous oxalic acid were sequentially added to the solution, and the mixture was stirred at constant temperature of 50℃for 30 minutes to obtain a mixed solution of the binder phase and the organic carrier.
(3) Uniformly stirring 52.5g of flake copper powder and 17.5g of flake Sn42Bi58 alloy powder to obtain a conductive phase; wherein the average grain diameter of the Sn42Bi58 alloy powder is 5 mu m, and the thickness is 300nm; the average size of the copper powder was 1 μm and the thickness was 100nm.
(4) Adding the conductive phase into the mixed solution, stirring by using a glass rod, and then putting into a three-roller grinder for grinding for 3-5 passes to obtain the low-temperature cured copper-based conductive paste for screen printing.
(5) Printing the prepared conductive paste on a glass carrier in a screen printing mode, carrying out vacuum curing for 20min at different curing temperatures, and measuring the resistivity of the cured conductive paste by using an RTS-9 four-probe tester, wherein the result shows that the lowest resistivity is 0.78 omega/≡when the curing temperature is 180 ℃.
Example 2
(1) 7.48g of epoxy E51 and 14.97g of cyclohexanone are mixed, heated in a water bath at 50 ℃ for 20min and magnetically stirred until the epoxy E51 is fully dissolved, and then 1.13g of ethylcellulose powder is added and magnetically stirred for 30min.
(2) After the ethylcellulose powder was sufficiently dissolved, 1.13g of triethanolamine, 0.07g of 2-ethyl-4-methylimidazole, 0.19g of BYK-410,0.09g of BYK-333,0.19g of BYK ES-80,0.47g of tributyl phosphate, 0.60g of 3-triethoxysilyl-1-propylamine, and 0.38g of anhydrous oxalic acid were sequentially added to the solution, and the mixture was stirred at constant temperature of 50℃for 30 minutes to obtain a mixed solution of the binder phase and the organic carrier.
(3) 55g of flake copper powder and 18.3g of flake Sn 42 Bi 58 The alloy powder is stirred uniformly to obtain a conductive phase; wherein the average grain diameter of the Sn42Bi58 alloy powder is 5 mu m, and the thickness is 300nm; the average size of the copper powder was 5 μm and the thickness was 80nm.
(4) And adding the conductive phase into the mixed solution, stirring by using a glass rod, and then putting into a three-roller grinder for grinding for 5 passes to obtain the low-temperature cured copper-based conductive paste for screen printing.
(5) Printing the prepared conductive paste on a glass carrier by a screen printing mode, carrying out vacuum curing for 20min at different curing temperatures, and measuring the resistivity of the conductive paste by an RTS-9 four-probe tester, wherein the result shows that the lowest resistivity is 0.12 omega/≡when the curing temperature is 180 ℃.
Example 3
(1) 7.48g of epoxy E51 and 14.97g of cyclohexanone are mixed, heated in a water bath at 50 ℃ for 20min and magnetically stirred until the epoxy E51 is fully dissolved, and then 1.13g of ethylcellulose powder is added and magnetically stirred for 30min.
(2) After the ethylcellulose powder was sufficiently dissolved, 1.13g of triethanolamine, 0.07g of 2-ethyl-4-methylimidazole, 0.19g of BYK-410,0.09g of BYK-333,0.19g of BYK ES-80,0.47g of tributyl phosphate, 0.60g of 3-triethoxysilyl-1-propylamine, and 0.38g of anhydrous oxalic acid were sequentially added to the solution, and the mixture was stirred at constant temperature of 50℃for 30 minutes to obtain a mixed solution of the binder phase and the organic carrier.
(3) 60g of flake copper powder and 20g of flake Sn 42 Bi 58 The alloy powder is stirred uniformly to obtain a conductive phase; wherein the average grain diameter of the Sn42Bi58 alloy powder is 5 mu m, and the thickness is 300nm; the average size of the copper powder was 1 μm and the thickness was 50nm.
(4) Adding the conductive phase into the mixed solution, stirring by using a glass rod, and then putting into a three-roller grinder for grinding for 3 passes to obtain the low-temperature cured copper-based conductive paste for screen printing.
(5) Printing the prepared conductive paste on a glass carrier by a screen printing mode, carrying out vacuum curing for 20min at different curing temperatures, and measuring the resistivity of the conductive paste by an RTS-9 four-probe tester, wherein the result shows that the lowest resistivity is 0.08 omega/≡when the curing temperature is 180 ℃.
Example 4
On the basis of example 1, unlike example 1, in step (3), the average particle diameter of the Sn42Bi58 alloy powder was 15 μm and the thickness was 600nm.
Example 5
On the basis of example 4, unlike example 4, in step (3), the Sn42Bi58 alloy powder had a spherical shape and a diameter of 15. Mu.m.
Example 6
On the basis of example 5, unlike example 5, in step (3), the diameter of the Sn42Bi58 alloy powder was 30. Mu.m.
The results of the sheet resistance measurements after curing of the slurries of examples 1, 4, 5, 6 are shown in Table 1 below.
TABLE 1 sheet resistance of different Sn42Bi58 alloy powders
| Numbering device | Morphology of alloy powder | Average particle diameter (mu m) of alloy powder | Square resistance (omega/sq/mil) |
| F1 | Sheet-like shape | 5 | 0.12 |
| F2 | Sheet-like shape | 15 | 0.23 |
| F3 | Spherical shape | 15 | 0.68 |
| F4 | Spherical shape | 30 | 5.79 |
FIG. 1 is a schematic diagram of the overall structure of a low temperature cured copper-based conductive paste according to the present invention; wherein 1 is copper powder, 2 is Sn42Bi58 alloy powder, and 3 is a resin matrix; as can be seen from fig. 1, the copper powder was uniformly dispersed in the resin matrix, and the Sn42Bi58 alloy powder filled in the gaps of the copper powder.
As can be seen from fig. 2, the copper paste is printed on the glass slide through screen printing, and the surface of the cured copper paste is smooth and flat, so that the cured copper paste has good printing effect and curing effect.
Fig. 3 is a surface SEM image of the conductive copper paste F1 to F4 after curing, and fig. 4 is a cross-sectional SEM image of the conductive copper paste F1 to F4 after curing. Fig. 3 (a) is an SEM image of copper paste with a reinforcing phase of 5 μm flake alloy powder and a corresponding EDS element scan surface profile; (b) SEM images of copper paste of 15 μm flake alloy powder for reinforcement phase and corresponding EDS element scanning surface distribution patterns; (c) SEM images of copper paste of 15 μm spherical alloy powder for reinforcement phase and corresponding EDS element scanning surface distribution patterns; (d) SEM image of copper slurry with 30 μm spherical alloy powder as reinforcing phase and corresponding EDS element scan surface profile. The reinforcing phase (a) in FIG. 4 is 5 μm flake alloy powder; (b) the reinforcing phase is 15 μm flake alloy powder; (c) the reinforcing phase is 15 μm spherical alloy powder; (d) the reinforcing phase is 30 μm spherical alloy powder.
Fig. 3 (a) is a surface SEM image of the solidified conductive copper paste F1, the reinforcing phase of which is sheet-like alloy powder of 5 μm, and when the paste is solidified, the alloy powder of low melting point near the surface is melted, and as can be seen from the EDS element scanning surface distribution diagram, the melted alloy powder fills in the gaps of the sheet-like copper powder, increasing the conductive path; as can be seen from fig. 4 (a), when the copper paste F1 is solidified, the internal low-melting-point alloy powder not only fills the gap between the flake copper powder and the flake copper powder, but also coats the flake copper powder, thereby significantly increasing the conductive path inside the copper film. The particle size of the flaky alloy powder is increased compared with F1, so that the surface of the alloy powder is agglomerated in the melting process, a compact film layer is formed at the agglomerated part, but holes are formed around the agglomerated part, as shown in (b) of fig. 3; as is clear from fig. 4 (b), when the conductive copper paste F2 is solidified, the alloy powder is melted and coated on the flake copper powder, so that more conductive paths are formed between the copper powders, but the particle size is too large, the distribution is uneven, and continuous paths cannot be formed between the alloy powders in the melted paste, so that more gaps exist, and the conductivity is affected.
Fig. 3 (c) is a surface SEM image of the conductive copper paste F3 after solidification, the reinforcing phase of which is spherical alloy powder of 15 μm, and when the paste is solidified, the alloy powder melts and fills the gaps of the flaky copper powder on the surface of the sphere, and large holes appear between the flaky copper powder in the vicinity, resulting in an increase in sheet resistance thereof; as is clear from fig. 4 (c), the spherical low-melting-point alloy powder does not flow sufficiently after melting, and only the flake copper powder attached to the surface of the spherical alloy powder is covered, but the flake copper powder in the vicinity is still connected by the epoxy resin. The conductive copper paste F4 has a larger particle diameter of the spherical low-melting-point alloy powder than F3, and the spherical alloy powder is uniformly distributed in the copper paste, and at the time of solidification, the alloy powder is not sufficiently melted and flowed due to the obstruction of components such as epoxy resin, flake copper powder, and the like, so that the spherical alloy powder is independently present in the conductive film, and a continuous conductive path is not formed with the nearby alloy powder, as shown in fig. 3 (d) and fig. 4 (d).
FIG. 5 is a scan of Sn42Bi58 alloy powder of examples 1, 4, 5, and 6; wherein, (a) 5 μm flake Sn42Bi58 alloy powder in FIG. 5; (b) 10 μm flake Sn42Bi58 alloy powder; (c) 15 μm spherical Sn42Bi58 alloy powder; (d) 30 μm flake Sn42Bi58 alloy powder.
In terms of the morphology of the alloy powder, when the conductive copper paste is not solidified, the contact between the flake Sn42Bi58 alloy powder and the flake copper powder is surface contact or line contact, and the contact between the spherical Sn42Bi58 alloy powder and the flake copper powder is point contact. When the copper paste is solidified, the contact area between the flake Sn42Bi58 alloy powder and the flake copper powder is large, the melted alloy powder can better coat the surrounding copper powder, and the copper powder is tightly connected through the Sn42Bi58 alloy powder to form more conductive paths; the contact area between the spherical Sn42Bi58 alloy powder and the flake copper powder is small, the flake copper powder is adhered to the surface of the spherical alloy powder, and the melted alloy powder cannot flow sufficiently and is dispersed in the copper film in an ellipsoidal shape or a spherical shape. In terms of the particle size of the alloy powder, the alloy powder with small particle size has larger specific surface area, and when the copper paste is solidified, the alloy powder can be contacted with more copper powder, so that pores among the copper powder are more easily filled, and the flaky copper powder is tightly connected.
Claims (10)
1. The low-temperature curing copper-based conductive paste for screen printing comprises a conductive phase, a bonding phase and an organic carrier, and is characterized in that the conductive phase material comprises a mixture of copper powder and Sn42Bi58 low-melting-point alloy powder; the Sn42Bi58 low-melting-point alloy powder is filled in gaps of copper powder in a melting mode in the solidification process of the copper-based conductive paste and is coated on the surface of the copper powder to form a three-dimensional conductive path; the copper powder accounts for 45-75% of the total weight of the copper-based conductive paste in percentage by weight; the Sn42Bi58 low-melting-point alloy powder accounts for 10-40% of the total weight of the copper-based conductive paste in percentage by weight.
2. The low-temperature-curable copper-based conductive paste for screen printing according to claim 1, wherein the curing temperature of the copper-based conductive paste is 150 to 190 ℃.
3. The low-temperature-curable copper-based conductive paste for screen printing according to claim 1, wherein the Sn 42 Bi 58 The particle shape of the low-melting-point alloy powder is flaky or spherical; when the shape is a sheet, the average size is 5-15 μm; when spherical in shape, the diameter is 15-30 μm.
4. The low-temperature-curable copper-based conductive paste for screen printing according to claim 1, wherein the particle shape of the copper powder is in the form of a flake, and the average size is 1 to 5 μm.
5. The low-temperature-curable copper-based conductive paste for screen printing according to claim 1, wherein the binder phase is one or two of bisphenol a type epoxy resins E51, F51, and vinyl chloride-vinyl acetate copolymer; the content of the copper-based conductive paste is 4-10% of the total weight of the copper-based conductive paste by weight percentage.
6. The low-temperature-curable copper-based conductive paste for screen printing according to claim 1, wherein the organic vehicle comprises a solvent, a curing agent, an accelerator, a thickener, a thixotropic agent, a leveling agent, an antifoaming agent, a conductive aid, a coupling agent, and a reducing agent.
7. The low-temperature-curable copper-based conductive paste for screen printing according to claim 6, wherein the curing agent is triethanolamine, and the content thereof is 0.6 to 1.3% by weight of the total weight of the copper-based conductive paste.
8. The low-temperature-curable copper-based conductive paste for screen printing according to claim 6, wherein the thickener is ethylcellulose, and the content thereof is 0.6-1.3% by weight of the total weight of the copper-based conductive paste; the reducing agent is anhydrous oxalic acid, ascorbic acid or anhydrous citric acid, and the content of the reducing agent is 0.25-0.45% of the total weight of the copper-based conductive paste in percentage by weight.
9. A method for preparing the low-temperature-curable copper-based conductive paste for screen printing according to claim 1, comprising the steps of:
(1) Weighing binder phase resin and solvent with corresponding mass until the binder phase resin is completely dissolved;
(2) Sequentially adding a thickening agent, a curing agent, an accelerator, a thixotropic agent, a leveling agent, a conductive auxiliary agent, a defoaming agent, a coupling agent and a reducing agent into the solution obtained in the step (1), and fully stirring and mixing to obtain a mixed solution;
(3) Uniformly mixing copper powder and Sn42Bi58 alloy powder to obtain a conductive phase;
(4) And (3) adding the conductive phase obtained in the step (3) into the mixed solution obtained in the step (2), and grinding to obtain the low-temperature-cured copper-based conductive paste for screen printing.
10. The method for preparing a low-temperature-curable copper-based conductive paste for screen printing according to claim 9, wherein the copper powder of step (3) is acid-washed with a dilute sulfuric acid or formic acid absolute ethanol solution before being mixed with the Sn42Bi58 alloy powder, dispersed with absolute ethanol, and dried.
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