A method for preparing silver-coated copper, silver-coated copper and electronic paste

Abstract

The application provides a preparation method of silver-coated copper, and the preparation method comprises the following steps: (1) taking copper powder, adding dilute sulfuric acid, performing ultrasonic treatment, and cleaning; (2) adding the copper powder obtained in the step (1) into water and stirring, adding a reducing agent, adjusting the pH value of the solution to 11±0.5, and then continuously stirring under the condition of 70℃±5℃; (3) adding an ammonia solution of silver salt into the solution obtained in the step (2) dropwise, and then reacting under the condition of 70℃±5℃ to obtain the silver-coated copper. The method has simple reaction steps, simple operation, and easy control of reaction conditions, and the prepared silver layer has good compactness and uniformity, and the oxidation resistance of the silver-coated copper can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of electronic paste technology, specifically relating to a method for preparing silver-coated copper, silver-coated copper, and electronic paste. Background Technology

[0002] Electronic paste is a basic material for manufacturing thick-film components. It is a paste-like substance made by uniformly mixing solid powder and organic solvent through three-roll milling. Electronic paste is widely used in aerospace, chemical, printing and construction fields.

[0003] The conductive phase commonly used in traditional electronic pastes is pure silver powder, but it is expensive and prone to electrochemical migration. Metallic copper and metallic silver have similar electrical conductivity, but copper has poor oxidation resistance and conductivity. The introduction of silver-coated copper can not only reduce the cost of the conductive phase in the paste, but also has good oxidation resistance, conductivity and resistance to electrochemical migration, which has important application value.

[0004] Traditional methods for preparing silver-coated copper include melt atomization, mechanical ball milling, displacement deposition, and chemical reduction. The first two methods require an inert atmosphere and complex equipment. Displacement deposition involves a displacement reaction between silver ions and copper, and the reaction rate is difficult to control. Reduction methods typically involve adding reducing agents such as ammonia, ascorbic acid, formaldehyde, glucose, or hydrazine hydrate. Silver particles are generated by the reaction of silver coordinating ions with the reducing agent and are coated on the copper surface. However, the reduction rate of silver is relatively fast, making it difficult to obtain a uniformly distributed silver layer. Furthermore, the coating process is complex and has problems such as poor coating properties. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a method for preparing silver-coated copper, which is simple to operate, easy to control the reaction conditions, and produces a dense and uniform silver layer, which can effectively improve the oxidation resistance of silver-coated copper.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A method for preparing silver-coated copper, the method comprising the following steps: (1) taking copper powder, adding dilute sulfuric acid, ultrasonic treatment, and cleaning; (2) adding the copper powder obtained in step (1) to water and stirring, adding a reducing agent, adjusting the pH value of the solution to 11±0.5, and then continuing to stir at 70℃±5℃; (3) adding an ammonia solution of silver salt to the solution obtained in step (2), and then reacting at 70℃±5℃ to obtain the silver-coated copper.

[0008] In some embodiments, the molar ratio of silver to copper powder in the silver salt is (0.15-1.1):1; preferably, the molar ratio of silver to copper powder in the silver salt is (0.50-1):1.

[0009] In some embodiments, the molar ratio of silver to reducing agent in the silver salt is (0.25-1.78):1; and / or, the molar ratio of silver to reducing agent in the silver salt is (0.45-1):1.

[0010] In some embodiments, the mass concentration of the dilute sulfuric acid in step (1) is 5% to 10%.

[0011] In some embodiments, the ultrasonic treatment time in step (1) is 1 min to 30 min.

[0012] In some embodiments, the reducing agent is selected from at least one of ascorbic acid and glucose; and / or, the silver salt is selected from at least one of silver nitrate and silver sulfate.

[0013] In some embodiments, the reaction time in step (3) is 10 min to 30 min.

[0014] The present invention also provides silver-coated copper prepared by the preparation method described above.

[0015] The present invention also provides the application of silver-coated copper prepared by the preparation method described above in the preparation of electronic pastes.

[0016] The present invention also provides an electronic paste, wherein the raw materials for preparing the electronic paste include silver-coated copper prepared by the preparation method described above.

[0017] This invention provides an optimized one-step chemical synthesis method for silver-coated copper. First, copper powder and a reducing agent are stirred under specific temperature (too high a temperature results in a faster reduction rate of silver ions and the formation of more free silver particles; too low a temperature results in a slower reaction rate and only some silver coating on the copper surface) and pH conditions. Then, an ammonia solution of silver salt is added to carry out the reaction. This method can effectively solve the problems of poor coating and uneven silver layer distribution in the existing reduction method for preparing silver-coated copper.

[0018] The method of this invention has simple reaction steps, is easy to operate, and the reaction conditions are easy to control. The silver layer obtained has good density and uniformity, which can effectively improve the oxidation resistance of silver-coated copper. Attached Figure Description

[0019] Figure 1 The images shown are electron microscope images of copper and silver-coated copper in Embodiment 1 of the present invention.

[0020] Figure 2 This is an electron microscope image of silver-coated copper in Embodiment 2 of the present invention.

[0021] Figure 3 This is an electron microscope image of the silver-coated copper in Embodiment 3 of the present invention.

[0022] Figure 4This is an electron microscope image of the silver-coated copper in Comparative Example 1.

[0023] Figure 5 The TGA images show the silver-coated copper and copper samples prepared in the embodiments and comparative examples of this invention. Detailed Implementation

[0024] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0025] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0026] The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or device that includes a series of steps is not limited to the steps or modules listed, but may optionally include steps not listed, or may optionally include other steps inherent to such process, method, product, or device.

[0027] In this invention, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] The following description is based on specific embodiments.

[0029] Example 1

[0030] This embodiment provides a method for preparing silver-plated copper, the method comprising the following steps:

[0031] 1. Removal of oxide layer on copper powder surface: Weigh 1g of copper powder, add 50mL of 10wt% dilute sulfuric acid, ultrasonically stir for 10min, wash the oxide on the surface with deionized water until neutral;

[0032] 2. Preparation of copper powder suspension: Place the pretreated copper powder in a beaker, add 50 mL of water and stir magnetically for 10 min at a stirring speed of 200 r / min. At the same time, add 50 mL of ascorbic acid solution (containing 1.76 g of ascorbic acid), adjust the pH of the solution to 11 with 1 M sodium hydroxide, and stir at 70 °C for 10 min.

[0033] 3. Coating reaction: Add 20 mL of ammonia solution of silver nitrate (silver nitrate content is 1.70 g) to the above solution, with a dropping rate of 2 mL / min, a reaction temperature of 70℃, and a reaction time of 20 min to obtain silver-coated copper powder;

[0034] 4. Cleaning of silver-coated copper powder: Wash the silver-coated copper 6 times with a mixed solution of ethanol and water, with a volume ratio of ethanol to water of 1:4.

[0035] 5. Drying: The cleaned silver-coated copper was dried at 60℃ for 3 hours to obtain an average particle size of 0.54μm.

[0036] Figure 1 These are electron microscope images of copper and silver-coated copper in Embodiment 1 of the present invention. Figure 2 As shown in the figure, TGA shows that the oxidation temperature of copper is 128℃, and the oxidation temperature of silver-coated copper is 168℃, indicating that the oxidation resistance of the prepared silver-coated copper is improved.

[0037] The structure of the silver-coated copper prepared in this embodiment is as follows: Figure 1 As shown.

[0038] Example 2

[0039] This embodiment provides a method for preparing silver-plated copper, the method comprising the following steps:

[0040] 1. Removal of oxide layer from copper powder surface: Weigh 1.28g of copper powder, add 50mL of 10wt% dilute sulfuric acid, ultrasonically stir for 20min, wash the surface oxide with deionized water until neutral;

[0041] 2. Preparation of copper powder suspension: Place the pretreated copper powder in a beaker, add 50 mL of water and stir magnetically for 10 min at a stirring speed of 200 r / min. At the same time, add 50 mL of ascorbic acid solution (containing 2.2 g of ascorbic acid), adjust the pH of the solution to 11.5 with 1 M sodium hydroxide, and stir at 75℃ for 10 min.

[0042] 3. Coating reaction: Add 20 mL of ammonia solution of silver nitrate (silver nitrate content is 1.70 g) to the above solution, with a dropping rate of 2 mL / min, a reaction temperature of 75℃, and a reaction time of 25 min to obtain silver-coated copper powder;

[0043] 4. Cleaning of silver-coated copper powder: Wash the silver-coated copper 6 times with a mixed solution of ethanol and water, with a volume ratio of ethanol to water of 1:4.

[0044] 5. Drying: Dry the cleaned silver-coated copper at 60℃ for 3 hours to obtain silver-coated copper.

[0045] The structure of the silver-coated copper prepared in this embodiment is as follows: Figure 2 As shown.

[0046] Example 3

[0047] This embodiment provides a method for preparing silver-plated copper, the method comprising the following steps:

[0048] 1. Removal of oxide layer from copper powder surface: Weigh 0.73g of copper powder, add 50mL of 10wt% dilute sulfuric acid, ultrasonically stir for 30min, wash the surface oxide with deionized water until neutral;

[0049] 2. Preparation of copper powder suspension: Place the pretreated copper powder in a beaker, add 50 mL of water and stir magnetically for 10 min at a stirring speed of 200 r / min. At the same time, add 50 mL of ascorbic acid solution (containing 3.91 g of ascorbic acid), adjust the pH of the solution to 10.5 with 1 M sodium hydroxide, and stir at 72℃ for 15 min.

[0050] 3. Coating reaction: Add 20 mL of ammonia solution of silver nitrate (silver nitrate content is 1.70 g) to the above solution, with a dropping rate of 2 mL / min, a reaction temperature of 72℃, and a reaction time of 30 min to obtain silver-coated copper powder;

[0051] 4. Cleaning of silver-coated copper powder: Wash the silver-coated copper 6 times with a mixed solution of ethanol and water, with a volume ratio of ethanol to water of 1:4.

[0052] 5. Drying: Dry the cleaned silver-coated copper at 60℃ for 3 hours to obtain silver-coated copper.

[0053] The structure of the silver-coated copper prepared in this embodiment is as follows: Figure 3 As shown.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing silver-plated copper, the method comprising the following steps:

[0056] 1. Weigh 3.52g of ascorbic acid, add 150mL of water, stir to dissolve, and then adjust the pH of the solution to 11 with 1M sodium hydroxide;

[0057] 2. Add 15 mL of copper ammonia solution (containing 2.49 g of copper sulfate pentahydrate) to the above solution at a rate of 2 mL / min, stir at 70 °C for 20 min, then add 20 mL of silver nitrate ammonia solution (silver nitrate content is 1.70 g) at the same rate, and react for 30 min to obtain silver-coated copper powder;

[0058] 3. Cleaning of silver-coated copper powder: Wash the silver-coated copper 6 times with a mixed solution of ethanol and water, with a volume ratio of ethanol to water of 1:4.

[0059] 4. Drying: Dry the cleaned silver-coated copper at 60℃ for 3 hours to obtain silver-coated copper.

[0060] The structure of the silver-coated copper obtained in this comparative example is as follows: Figure 4 As shown.

[0061] The density, dispersibility, and oxidation temperature of the silver coating in the silver-coated copper prepared in the above examples and comparative examples were tested using the following methods:

[0062] (1) Silver coating density: SEM.

[0063] (2) Dispersion: SEM.

[0064] (3) Oxidation temperature: TGA.

[0065] The test results are shown in Table 1:

[0066] Table 1

[0067]

[0068] The above results show that the silver coating obtained by the preparation method of the present invention (Examples 1-3) has better density and uniformity than that of Comparative Example 1, and the oxidation resistance of silver-coated copper is also improved accordingly.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for producing silver-coated copper, characterized by, The preparation method comprises the following steps: (1) taking copper powder, adding dilute sulfuric acid, ultrasonic treatment, and cleaning; (2) stirring the copper powder obtained in step (1) in water, adding a reducing agent, adjusting the pH value of the solution to 11±0.5, and then continuously stirring at 70℃±5℃; (3) adding an ammonia solution of a silver salt to the solution obtained in step (2) dropwise, and then reacting at 70℃±5℃ to obtain the silver-coated copper; The molar ratio of silver to copper powder in the silver salt is (0.50-1):1; the molar ratio of silver to the reducing agent in the silver salt is (0.45-1):1; The mass concentration of the dilute sulfuric acid in step (1) is 5%-10%, and the ultrasonic treatment time is 1 min-30 min; the reducing agent in step (2) is at least one selected from ascorbic acid and glucose; the silver salt in step (3) is at least one selected from silver nitrate and silver sulfate, and the reaction time is 10 min-30 min.

2. The silver-coated copper obtained by the preparation method of claim 1.

3. The application of the silver-coated copper obtained by the preparation method of claim 1 in the preparation of electronic paste.

4. An electronic paste characterized by, The raw material for preparing the electronic paste comprises the silver-coated copper obtained by the preparation method of claim 1.

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