A copper powder coated with iron, cobalt and nickel, its preparation method and application

Abstract

The present invention provides an iron-cobalt-nickel coated copper powder, a preparation method thereof and an application; the iron-cobalt-nickel coated copper powder is obtained by the following method: (1) Pretreatment of copper powder: Take copper powder, add it to water, ultrasonically disperse it, then add a weak acid, mix well to make the pH value of the solution 3-5; then add ammonia water or APTES, mix well to obtain a mixed solution; (2) Add a negatively charged complex of iron, a negatively charged complex of cobalt and a negatively charged complex of nickel to the mixed solution, mix well, and then add a reducing agent for a reduction reaction; (3) Add a negatively charged complex of iron, a negatively charged complex of cobalt and a negatively charged complex of nickel to the reaction product of step (2), and stir in the same direction under the condition of an externally applied annular magnetic field; (4) Collect the product, wash and purify it. The iron-cobalt-nickel coated copper powder of the present invention adopts in-situ coating, which can effectively improve the particle magnetism, realize contact connection, reduce the contact resistance of the conductive paste, and improve the conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive pastes, and particularly relates to an iron-cobalt-nickel-coated copper powder, a preparation method thereof, and an application thereof. Background Art

[0002] Heterojunction solar cells are a new type of high-efficiency solar cells. Due to their series of advantages such as high conversion efficiency, low temperature coefficient, and the ability to achieve thin-filmization, they have become a new technological trend in the solar energy industry. However, heterojunction solar cells face problems such as huge initial equipment investment and high costs of target materials and pastes. Reducing the cost of low-temperature pastes for heterojunction solar cells has become an urgent problem to be solved in the industry. Among them, copper powder is cheap (0.01 times that of silver) and has conductivity similar to silver, so it is widely favored. However, copper is prone to oxidation, especially when it is in the micro-nano scale. Therefore, using coated copper powder to replace pure silver powder to prepare low-temperature pastes for heterojunction solar cells has become a research hotspot in the industry in recent years.

[0003] Currently, there is a lack of low-temperature pastes with low contact resistance and good conductivity during low-temperature curing on the market. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an iron-cobalt-nickel-coated copper powder, a preparation method thereof, and an application thereof. The iron-cobalt-nickel-coated copper powder can achieve good contact connection even during low-temperature curing by using the magnetic attraction between particles, thereby reducing the contact resistance and further improving the conductivity of the paste.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions.

[0006] A preparation method of an iron-cobalt-nickel-coated copper powder includes the following steps: (1) Pretreatment of copper powder: Take copper powder, add it to water, ultrasonically disperse it, then add a weak acid, mix well to make the pH value of the solution 3-5; then add ammonia water or APTES, mix well to obtain a mixed solution; (2) Add a negatively charged complex of iron, a negatively charged complex of cobalt, and a negatively charged complex of nickel to the mixed solution, mix well, and then add a reducing agent for a reduction reaction; (3) Add a negatively charged complex of iron, a negatively charged complex of cobalt, and a negatively charged complex of nickel to the reaction product of step (2), and stir in the same direction under the condition of an externally applied circular magnetic field; (4) Collect the product, wash and purify it to obtain the iron-cobalt-nickel-coated copper powder.

[0007] In some embodiments, the concentration of copper powder in step (1) is 10 g / L - 40 g / L.

[0008] In some embodiments, the mass of the ammonia water or APTES accounts for 0.1% - 0.5% of the total mass of the solution in step (1); and / or, stir for 10 min - 30 min after adding the ammonia water or APTES.

[0009] In some embodiments, the concentration of the negatively charged iron complex in step (2) is 1 g / L to 100 g / L; the concentration of the negatively charged cobalt complex is 1 g / L to 100 g / L; and the concentration of the negatively charged nickel complex is 1 g / L to 100 g / L.

[0010] In some embodiments, the mass ratio of the negatively charged iron complex in step (2) to that in step (3) is 1:1.5-5.

[0011] In some embodiments, the mass ratio of the negatively charged cobalt complex in step (2) to that in step (3) is 1:1.5-5.

[0012] In some embodiments, the mass ratio of the negatively charged nickel complex in step (2) to that in step (3) is 1:1.5-5.

[0013] In some embodiments, the final concentration of the reducing agent in step (2) is 10 g / L to 200 g / L.

[0014] In step (3), the stirring speed is 30 r / min to 300 r / min, and the stirring time is 30 min to 60 min; and / or, the magnetic field strength in step (3) is 0.1 T to 1.5 T.

[0015] In some embodiments, the negatively charged iron complex is selected from one or more of an iron chloride coordination complex, an iron cyanide coordination complex, and an iron thiocyanate coordination complex.

[0016] In some embodiments, the negatively charged cobalt complex is selected from one or more of a chloro coordination complex of cobalt, a cyano coordination complex of cobalt, and a thiocyanate coordination complex of cobalt.

[0017] In some embodiments, the negatively charged nickel complex is selected from one or more of a nickel chloride coordination complex, a nickel cyanide coordination complex, and a nickel thiocyanate coordination complex.

[0018] In some embodiments, the negatively charged complex of iron is selected from FeCl4 - ,Fe(CN)6 3- ,Fe(SCN)6 3- , FeCl6 3- One or more of .

[0019] In some embodiments, the negatively charged cobalt complex is selected from CoCl4 2- , Co2(CN) 10 6- ,Co(SCN)4 2- One or more of .

[0020] In some embodiments, the negatively charged complex of nickel is selected from one or more of NiCl4 2- , Ni(CN)4 2- , Ni(SCN)4 2- and the like.

[0021] In some embodiments, the weak acid is selected from one or more of dilute hydrochloric acid, dilute nitric acid, and dilute sulfuric acid.

[0022] In some embodiments, the reducing agent is selected from one or more of ascorbic acid, glucose, hydrazine hydrate, and sodium borohydride.

[0023] The present invention also provides iron-cobalt-nickel-coated copper powder obtained by the method described above.

[0024] The present invention also provides the use of the iron-cobalt-nickel-coated copper powder obtained by the method described above in the preparation of conductive paste.

[0025] The present invention also provides a conductive paste, characterized in that the conductive paste contains the iron-cobalt-nickel-coated copper powder obtained by the method described above.

[0026] The present invention provides an iron-cobalt-nickel-coated copper powder. Through the optimization of the preparation method, in-situ coating on the copper surface can be achieved. The pretreated copper powder is first subjected to in-situ replacement with the complex of the precursor, maintaining weak reducibility, and then the corresponding negatively charged complex is added to ensure in-situ coating and slow deposition of the coating, thereby improving the bonding degree and crystallinity, making the obtained grain size small, capable of forming deformation texture and recrystallization texture, and having strong magnetism. When the iron-cobalt-nickel-coated copper powder is used in the preparation of conductive paste, by utilizing the magnetism between particles, in addition to the shrinkage of the polymer pulling the particles closer during curing, the particles further attract each other, increasing the possibility of contact bridging, and good contact bridging can also be achieved during low-temperature curing, thereby reducing the contact resistance and further improving the conductive performance of the paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 SEM and TEM images of the coated copper powder in Example 1.

[0028] Figure 2 SEM and TEM images of the coated copper powder in Example 2.

[0029] Figure 3 SEM and TEM images of the coated copper powder in Example 3.

[0030] Figure 4 SEM and TEM images of the coated copper powder in Example 4.

[0031] Figure 5SEM and TEM images of the copper powder coated in Comparative Example 1.

[0032] Figure 6 SEM and TEM images of the copper powder coated in Comparative Example 2.

[0033] Figure 7 SEM and TEM images of the copper powder coated in Comparative Example 3. Detailed implementation manners

[0034] In the following examples of the present invention, the experimental methods without specifying specific conditions are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. All common chemical reagents used in the examples are commercially available products.

[0035] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] The terms "comprising" and "having" and any variations thereof in the present invention are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps is not limited to the listed steps or modules, but may optionally further include steps not listed, or may optionally further include other steps inherent to these processes, methods, products or equipment.

[0037] As used in the present invention, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0038] The following is described in conjunction with specific embodiments. In the following embodiments, the negatively charged complexes of iron, cobalt, and nickel can be prepared by conventional methods in the art.

[0039] Example 1

[0040] This example provides an iron-cobalt-nickel coated copper powder, which is prepared by the following method (500 mL reaction system):

[0041] (1) Pretreatment of copper powder: Take 10 g of copper powder, add it to water, ultrasonically disperse it, then add dilute hydrochloric acid, mix well to make the pH value of the solution 3; then add 0.2% ammonia water based on the total weight of the solution, and stir for 30 min to obtain a mixed solution;

[0042] (2) Add negatively charged complexes of iron (final concentration: 10 g / L), cobalt (final concentration: 10 g / L), and nickel (final concentration: 10 g / L) to the said mixed solution, mix well, and then add 20 g of ascorbic acid for a reduction reaction for 20 min;

[0043] (3) Add negatively charged complexes of iron (final concentration: 20 g / L), cobalt (final concentration: 20 g / L), and nickel (final concentration: 20 g / L) to the reaction product of step (2), and stir in the same direction under the condition of an externally applied circular magnetic field (intensity: 1.0 T) (rotation speed: 100 r / min, time: 40 min);

[0044] (4) Collect the product, wash, purify, and dry it to obtain the said iron-cobalt-nickel-coated copper powder.

[0045] Example 2

[0046] This example provides an iron-cobalt-nickel-coated copper powder, which is prepared by the following method (500 mL reaction system):

[0047] (1) Pretreatment of copper powder: Take 10 g of copper powder, add it to water, ultrasonically disperse it, then add dilute nitric acid, mix well to make the pH value of the solution 4.5; then add 0.15% of ammonia water based on the total weight of the solution, and stir for 20 min to obtain a mixed solution;

[0048] (2) Add negatively charged complexes of iron (final concentration: 50 g / L), cobalt (final concentration: 50 g / L), and nickel (final concentration: 50 g / L) to the said mixed solution, mix well, and then add 30 g of hydrazine hydrate for a reduction reaction for 20 min;

[0049] (3) Add negatively charged complexes of iron (final concentration: 100 g / L), cobalt (final concentration: 100 g / L), and nickel (final concentration: 100 g / L) to the reaction product of step (2), and stir in the same direction under the condition of an externally applied circular magnetic field (intensity: 1.4 T) (rotation speed: 100 r / min, time: 40 min);

[0050] (4) Collect the product, wash, purify, and dry it to obtain the said iron-cobalt-nickel-coated copper powder.

[0051] Example 3

[0052] This example provides an iron-cobalt-nickel-coated copper powder, which is prepared by the following method (500 mL reaction system):

[0053] (1) Copper powder pretreatment: 10 g of copper powder was added to water, ultrasonically dispersed, and diluted hydrochloric acid was added and mixed until the pH value of the solution was 5; then 0.45% of the total weight of the solution was added with ammonia water and stirred for 15 min to obtain a mixed solution;

[0054] (2) adding a negatively charged iron complex (final concentration of 5 g / L), a negatively charged cobalt complex (final concentration of 5 g / L), and a negatively charged nickel complex (final concentration of 5 g / L) to the mixed solution, mixing them evenly, and then adding 5 g of sodium borohydride to carry out a reduction reaction for 20 minutes;

[0055] (3) adding a negatively charged iron complex (final concentration of 15 g / L), a negatively charged cobalt complex (final concentration of 15 g / L), and a negatively charged nickel complex (final concentration of 15 g / L) to the reaction product of step (2), and stirring in the same direction (rotating speed of 100 r / min, time for 40 min) under the condition of an external toroidal magnetic field (intensity of 0.8 T);

[0056] (4) collecting the product, washing and purifying it, and drying it to obtain the iron-cobalt-nickel coated copper powder.

[0057] Example 4

[0058] This embodiment provides an iron-cobalt-nickel coated copper powder, which is prepared by the following method (500 mL reaction system):

[0059] (1) Copper powder pretreatment: 10 g of copper powder was added to water, ultrasonically dispersed, and then diluted sulfuric acid was added and mixed until the pH value of the solution was 3.5; then 0.15% of the total weight of the solution was added with APTES, and stirred for 30 min to obtain a mixed solution;

[0060] (2) adding a negatively charged iron complex (final concentration of 20 g / L), a negatively charged cobalt complex (final concentration of 20 g / L), and a negatively charged nickel complex (final concentration of 20 g / L) to the mixed solution, mixing them evenly, and then adding 50 g of ascorbic acid to carry out a reduction reaction for 20 minutes;

[0061] (3) adding a negatively charged iron complex (final concentration of 50 g / L), a negatively charged cobalt complex (final concentration of 50 g / L), and a negatively charged nickel complex (final concentration of 50 g / L) to the reaction product of step (2), and stirring in the same direction (rotating speed of 100 r / min, time for 40 min) under the condition of an external toroidal magnetic field (intensity of 1.2 T);

[0062] (4) collecting the product, washing and purifying it, and drying it to obtain the iron-cobalt-nickel coated copper powder.

[0063] Comparative Example 1

[0064] This comparative example provides an iron-cobalt-nickel coated copper powder. The preparation method (500 mL reaction system) is different from that of Example 1 in that a negatively charged complex is added all at once, specifically as follows:

[0065] (1) Copper powder pretreatment: Take 10 g of copper powder, add it to water, ultrasonically disperse it, then add dilute hydrochloric acid and mix well to make the pH value of the solution 3; then add 0.2% of the total solution weight of ammonia water and stir for 30 min to obtain a mixed solution;

[0066] (2) Add an iron negatively charged complex (final concentration of 20 g / L), a cobalt negatively charged complex (final concentration of 20 g / L), and a nickel negatively charged complex (final concentration of 20 g / L) to the mixed solution, mix well, and then add 20 g of ascorbic acid for a reduction reaction for 20 min;

[0067] (3) Stir in the same direction (rotation speed of 100 r / min, time of 40 min) under the condition of an externally applied circular magnetic field (intensity of 1.0 T);

[0068] (4) Collect the product, wash, purify, and dry it to obtain the iron-cobalt-nickel coated copper powder.

[0069] Comparative Example 2

[0070] This comparative example provides an iron-cobalt-nickel coated copper powder. The preparation method (500 mL reaction system) is different from that of Example 1 in that an excessive amount of reducing agent is added, specifically as follows:

[0071] (1) Copper powder pretreatment: Take 10 g of copper powder, add it to water, ultrasonically disperse it, then add dilute hydrochloric acid and mix well to make the pH value of the solution 3; then add 0.2% of the total solution weight of ammonia water and stir for 30 min to obtain a mixed solution;

[0072] (2) Add an iron negatively charged complex (final concentration of 10 g / L), a cobalt negatively charged complex (final concentration of 10 g / L), and a nickel negatively charged complex (final concentration of 10 g / L) to the mixed solution, mix well, and then add 120 g of ascorbic acid for a reduction reaction for 20 min;

[0073] (3) Add an iron negatively charged complex (final concentration of 20 g / L), a cobalt negatively charged complex (final concentration of 20 g / L), and a nickel negatively charged complex (final concentration of 20 g / L) to the reaction product of step (2), and stir in the same direction (rotation speed of 100 r / min, time of 40 min) under the condition of an externally applied circular magnetic field (intensity of 1.0 T);

[0074] (4) Collect the product, wash, purify, and dry it to obtain the iron-cobalt-nickel coated copper powder.

[0075] Comparative Example 3

[0076] The coated copper powder in this comparative example is commercially available nickel-coated copper powder.

[0077] Performance Testing

[0078] The following properties of the coated copper powders in the above examples and comparative examples were tested, and the results are shown in Table 1:

[0079] Coating thickness: measured by transmission electron microscopy.

[0080] Tap density: GB / 5162-2006

[0081] 1. Weigh the sample to be tested using a balance.

[0082] 2. Place the sample into the graduated cylinder, making sure the surface of the powder is level. Place the cylinder on a vibrating device and vibrate until the volume of the powder no longer decreases.

[0083] 3. If the top surface of the powder is horizontal after compaction, read the value directly. If the top surface of the powder is not horizontal after compaction, read the highest and lowest values and calculate their average value to get the compacted volume. When reading, use 100cm 3 Graduated cylinder, accurate to 0.5 cm 3 ; Use 25cm 3 Graduated cylinder, accurate to 0.1 cm 3 .

[0084] 4. Tap density is calculated by dividing mass by volume.

[0085] Bulk density: GB / 1479.2-2011

[0086] 1. Use a stopper to plug the outlet of the funnel. Put the dust sample into the sample cylinder, scrape it flat with a scraper, and pour it into the funnel.

[0087] 2. Pull out the stopper rod to allow the dust to fall freely into the lower measuring cylinder. After all the dust in the funnel flows out, use a scraper to scrape off the dust accumulated on the upper part of the measuring cylinder.

[0088] 3. Place the measuring cylinder containing dust on the balance and weigh it.

[0089] 4. Bulk density is calculated by dividing mass by volume.

[0090] Conductive pastes were prepared using the coated copper powders in the above examples and comparative examples, respectively, as follows: 0.05 g of ferrocene tetrafluoroborate and 0.75 g of diethylene glycol monobutyl ether were weighed and thoroughly mixed. The mixture was then stirred evenly with 1 g of an aliphatic epoxy resin monomer at 25° C. 18.2 g of the dried coated copper powder was added, followed by dispersion on a three-roll disperser to obtain a conductive paste. The following properties were tested, and the results are shown in Table 1:

[0091] Viscosity: At a certain temperature, when a liquid flows in an upright capillary tube, completely wetting the tube wall, its kinematic viscosity is proportional to the flow time. During measurement, a liquid of known kinematic viscosity is used as a standard. The time it takes for the liquid to flow out of a capillary viscometer is measured. The time it takes for the sample to flow out of the same viscometer is then measured to calculate the sample's viscosity.

[0092] density:

[0093] 1. Use a balance to weigh the sample to be tested.

[0094] 2. Measure the volume using the displacement method.

[0095] 3. Density is mass divided by volume.

[0096] Volume resistivity: After the screen-printed slurry is cured, its resistance is measured with a multimeter. The reciprocal of the resistance is the resistivity.

[0097] Table 1

[0098]

[0099] The SEM and TEM images of the coated copper powders of Examples 1 to 4 of the present invention are shown as follows: Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, the SEM and TEM images of the coated copper powders of Comparative Examples 1 to 3 are shown as follows: Figure 5 、 Figure 6 and Figure 7 As shown in the comparison of Examples 1-4, it can be seen that the coating thickness increases with the increase of the magnetic field and the amount of coating material. After the particles are fully coated, the size is relatively uniform, and there are no free elemental particles of the coating metal; while in Comparative Examples 1-3, there are free elemental particles that are not coated.

[0100] The above results show that the coated copper powder of the present invention has a large coating thickness and good coating uniformity, high tap density and loose density, and excellent performance. The low-temperature curing slurry prepared by using it has low viscosity and high density, can achieve good contact overlap, low contact resistance, and further improved conductive performance.

[0101] Compared with Example 1, in Comparative Example 1, the negatively charged complex was added at one time during the preparation of the coated copper powder, resulting in the presence of free uncoated particles and a decrease in the overall coating thickness.

[0102] Compared with Example 1, the addition of excessive reducing agent in Comparative Example 2 cannot ensure weak reducing properties, which also leads to the existence of free uncoated particles and a decrease in the overall coating thickness.

[0103] From the test results of Comparative Example 3, it can be seen that compared with the existing nickel-coated copper powder, the coating layer thickness of the coated copper powder of the present invention is controllable and denser; the tapped and loose bulk density is higher, which is more conducive to slurry preparation, the viscosity is smaller, the processing performance is better, and the slurry density is larger.

[0104] In summary, the present invention obtains an iron-cobalt-nickel coated copper powder through optimization. It uses in-situ coating, has a large and uniform coating thickness, can effectively improve the particle magnetism, achieve contact bridging, reduce the contact resistance of the conductive paste, and improve the conductivity.

[0105] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0106] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A preparation method of iron-cobalt-nickel coated copper powder, characterized in that, It includes the following steps: (1) Pretreatment of copper powder: Take copper powder, add it into water, ultrasonically disperse it, then add weak acid, mix well to make the pH value of the solution be 3 - 5; then add ammonia water or APTES, mix well to obtain a mixed solution; (2) Add negatively charged complexes of iron, cobalt, and nickel to the said mixed solution, mix well, and then add a reducing agent to carry out a reduction reaction; (3) Add negatively charged complexes of iron, cobalt, and nickel to the reaction product of step (2), and stir in the same direction under the condition of an externally applied circular magnetic field; (4) Collect the product, wash and purify it to obtain the iron-cobalt-nickel-coated copper powder.

2. The preparation method of the iron-cobalt-nickel-coated copper powder according to claim 1, characterized in that, In step (1), the concentration of the copper powder is 10 g / L - 40 g / L; and / or, The mass of the said ammonia water or APTES accounts for 0.1% - 0.5% of the total mass of the solution in step (1); and / or, After adding ammonia water or APTES, stir for 10 min - 30 min.

3. The preparation method of the iron-cobalt-nickel-coated copper powder according to claim 1, wherein, In step (2), the concentration of the negatively charged complex of iron is 1 g / L - 100 g / L; the concentration of the negatively charged complex of cobalt is 1 g / L - 100 g / L; the concentration of the negatively charged complex of nickel is 1 g / L - 100 g / L.

4. The preparation method of the iron-cobalt-nickel-coated copper powder according to claim 1, characterized in that, In steps (2) and (3), the mass ratio of the negatively charged complex of iron is 1:1.5 - 5; the mass ratio of the negatively charged complex of cobalt is 1:1.5 - 5; the mass ratio of the negatively charged complex of nickel is 1:1.5 - 5; and / or, In step (2), the final concentration of the reducing agent is 10 g / L - 200 g / L.

5. The preparation method of the iron-cobalt-nickel-coated copper powder according to claim 1, wherein In step (3), the stirring speed is 30 r / min - 300 r / min, and the stirring time is 30 min - 60 min; and / or, In step (3), the magnetic field strength is 0.1 T - 1.5 T.

6. The preparation method of the iron-cobalt-nickel coated copper powder according to claim 1, characterized in that, The negatively charged complex of iron is selected from one or more of iron chloro-coordination complex, iron cyano-coordination complex, and iron thiocyanate-coordination complex; the negatively charged complex of cobalt is selected from one or more of cobalt chloro-coordination complex, cobalt cyano-coordination complex, and cobalt thiocyanate-coordination complex; the negatively charged complex of nickel is selected from one or more of nickel chloro-coordination complex, nickel cyano-coordination complex, and nickel thiocyanate-coordination complex.

7. The preparation method of the iron-cobalt-nickel-coated copper powder according to claim 6, characterized in that, The negatively charged iron complex is selected from one or more of FeCl4 - , Fe(CN)6 3- , Fe(SCN)6 3- , FeCl6 3- ; the negatively charged cobalt complex is selected from one or more of CoCl4 2- , Co2(CN) 10 6- , Co(SCN)4 2- ; the negatively charged nickel complex is selected from one or more of NiCl4 2- , Ni(CN)4 2- , Ni(SCN)4 2- .

8. The iron-cobalt-nickel-coated copper powder prepared by the method according to any one of claims 1 - 7.

9. The application of the iron-cobalt-nickel-coated copper powder prepared by the method according to any one of claims 1 - 7 in the preparation of conductive paste.

10. A conductive paste, characterized in that, The conductive paste contains the iron-cobalt-nickel-coated copper powder prepared by the method according to any one of claims 1 - 7.

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