Preparation method of copper conductive adhesive based on modified antioxidant copper powder

Abstract

The application discloses a preparation method of copper conductive glue based on modified antioxidant copper powder and belongs to the technical field of conductive glue. (S1) A diluent and a conductive additive are mixed to obtain a modifier through ultrasonic reaction; (S2) an epoxy resin, a curing agent, a curing promoter, the modifier prepared in the step (S1) and a dispersing agent are mixed to obtain a first mixture through stirring; (S3) antioxidant copper powder is added into the first mixture to obtain a second mixture through stirring; and (S4) the second mixture is deaerated and cured to obtain the copper conductive glue based on the modified antioxidant copper powder. The application further improves the conductive performance and the antioxidant performance of the conductive glue and overcomes the problems of high preparation cost and long manufacturing period of silver conductive glue.

Description

Technical Field

[0001] This invention belongs to the field of conductive adhesive technology and relates to a method for preparing copper conductive adhesive. Background Technology

[0002] Conductive adhesive is a special type of adhesive prepared by adding curing agents, conductive fillers, and other additives to an organic polymer matrix resin. After curing and drying, it exhibits a certain degree of conductivity. Once cured, conductive adhesive can bond different or similar conductive materials together. Because it possesses conductivity similar to that of metals, a conductive circuit can be formed between the bonded materials after curing. The difference between conductive adhesive and other conductive polymers lies in the fact that conductive adhesive requires a certain degree of fluidity under storage conditions and exhibits stable conductivity, a certain bond strength, and excellent anti-aging properties after heat curing.

[0003] In numerous studies on conductive metal adhesives, fillers have been selected from various metal powders, including gold, silver, and copper. However, due to their high cost, the application of gold and silver as fillers in conductive adhesives is relatively limited.

[0004] Copper conductive adhesives have applications in many areas. In its initial form, copper paste can also be used in the clothing industry, such as in heated down jackets and gloves. The application scenarios and fields for copper conductive adhesives are very broad, and the market size is huge. However, copper as a filler has drawbacks such as high volume resistivity, poor conductivity, easy oxidation, decreased electrical properties after oxidation, and poor mechanical properties, which limit its application in conductive adhesives.

[0005] Research on copper conductive adhesives represents a typical closed-loop research system encompassing "materials-process-performance-application." Its research focuses on how to economically and effectively address the oxidation problem of copper. Current research priorities include finding the optimal balance between cost, conductivity, stability, and process feasibility, enabling its overall performance to approach or even surpass that of silver conductive adhesives in some aspects. Further research focuses include exploring mechanisms and verifying performance through three pillars: filler innovation, matrix modification, and process optimization, combined with advanced characterization methods. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing copper conductive adhesive based on modified antioxidant copper powder, which further improves the conductivity and antioxidant properties of the conductive adhesive, and overcomes the problems of high preparation cost and long manufacturing cycle of silver conductive adhesive.

[0007] The technical solution of the present invention is as follows: A method for preparing copper conductive adhesive based on modified antioxidant copper powder, comprising the following steps: (S1) The diluent and conductive additive are mixed and subjected to ultrasonic reaction to obtain the modifier; (S2) Mix epoxy resin, curing agent, curing accelerator, modifier and dispersant prepared in step (S1) in a mass ratio of 100:(80~110):(10~40):(15~45):(5~20) and stir until homogeneous to obtain the first mixture; (S3) Add antioxidant copper powder to the first mixture and stir to obtain the second mixture; (S4) The second mixture is degassed and cured to obtain a copper conductive adhesive based on modified antioxidant copper powder; In step (S1), the conductive additive is adipic acid; In step (S2), the curing agent is selected from one or more of tetraethylenepentamine, diethylenetriamine, polyamide, and methyltetrahydrophthalic anhydride; the curing accelerator is selected from one or more of 2,4,6-tris(dimethylaminomethyl)phenol, anhydride accelerator, benzyl dimethylamine, and quaternary ammonium salt; and the dispersant is selected from one or more of sodium hexametaphosphate, sodium tripolyphosphate, triethanolamine, and sodium polyacrylate. The antioxidant copper powder described in step (S3) is prepared according to the following steps: The solvent and organic monomer are mixed, the pH of the mixture is adjusted to acidic, copper powder is added, and the mixture is stirred to obtain a first mixture. After the first mixture is magnetically stirred, an oxidant is added and reacted. The mixture is then filtered, washed, and vacuum dried to obtain antioxidant copper powder. The organic monomer is selected from one or two of pyrrole and aniline.

[0008] Preferably, in step (S1), the diluent is selected from one or more of ethanol, isopropanol, and terpineol; the mass ratio of diluent to conductive additive is 10:1.

[0009] Preferably, the organic monomer is aniline.

[0010] Preferably, in step (S2), the curing agent used is diethylenetriamine.

[0011] Preferably, in step (S2), the curing accelerator used is 2,4,6-tris(dimethylaminomethyl)phenol.

[0012] Preferably, in the preparation step of antioxidant copper powder, the oxidant is selected from one or two of silver nitrate and sodium chlorite; the volume-to-mass ratio of organic monomer to copper powder is (3-5) mL: 9 g.

[0013] More preferably, the volume-to-mass ratio of the organic monomer to the copper powder is 4 mL: 9 g.

[0014] Preferably, in the preparation step of antioxidant copper powder, the solvent is selected from alcohols; the volume ratio of the solvent to the organic monomer is 25-100:3-5.

[0015] Preferably, in the preparation step of antioxidant copper powder, before mixing the solvent and organic monomer, hydrochloric acid and anhydrous ethanol are mixed, copper powder is added, and the mixture is magnetically stirred.

[0016] Preferably, in step (S2), the curing agent is diethylenetriamine, and the curing accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention explores the influencing factors of copper-based conductive adhesives using the controlled variable method, and studies and screens the formulation ratios for preparing copper-based conductive adhesives using infrared spectroscopy analysis and orthogonal experiments. A conductive adhesive with advantages such as better appearance, excellent conductivity, low cost, and good environmental performance was successfully prepared.

[0018] In this invention's method for preparing antioxidant copper powder, a polymer is formed on the surface of copper powder using a chemical method. By precisely controlling the reaction conditions, a uniform, dense, and strongly adherent polymer protective layer can be obtained on the copper powder surface. This combines the excellent conductivity of copper powder with the environmental stability and functionality of the polymer, expanding its applications in conductive adhesives, electromagnetic shielding, anti-corrosion coatings, and supercapacitors. The key feature of this method is that organic monomers are uniformly coated on the copper powder surface through polymerization, forming a polymer film. This film can isolate the copper powder from contact with the environment to a certain extent, inhibiting the oxidation of the copper conductive adhesive. The polymer monomers possess a certain degree of conductivity, and the coating layer does not reduce the conductivity of the conductive adhesive to a certain extent.

[0019] In the preparation method, the dispersant (one or more of sodium hexametaphosphate, sodium tripolyphosphate, triethanolamine and sodium polyacrylate) can improve the dispersibility of copper powder in the modified resin matrix, improve the conductivity of the conductive adhesive, and significantly reduce the resistivity of the conductive adhesive.

[0020] In existing copper conductive adhesive preparations, formaldehyde, acetone, and other reducing agents are often used to prevent copper oxidation. These agents are highly hazardous and have poor antioxidant properties. This invention does not use these hazardous raw materials and produces a strong antioxidant effect.

[0021] Using different types of copper powder as experimental raw materials, the raw material price is relatively low, the experiment has low cost and good economic benefits.

[0022] The working principle of the copper conductive adhesive in this invention is mainly based on the contact between conductive copper powder particles. The conductive copper powder particles contact and are uniformly dispersed in the adhesive. When the copper conductive adhesive is coated or applied to the location where conductivity is required, the conductive particles form a conductive network structure. When current passes through, the contact between the conductive particles provides a conductive channel. The resin acts as a connector to bond the fillers together and form a conductive network, making the conductive structure more stable and the conductivity better. Attached Figure Description

[0023] Figure 1 This is used to display infrared comparison images of copper powder before and after processing in some embodiments of the present invention.

[0024] Figure 1 In the text, "before treatment" corresponds to Comparative Example 1; "polypyrrole treatment" corresponds to Example 1; and "polyaniline treatment" corresponds to Example 5. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] This invention is not limited to the following specific embodiments. Those skilled in the art can implement this invention using other specific embodiments based on the content disclosed herein. Any simple changes or modifications made to the design structure and concept of this invention fall within the protection scope of this invention.

[0027] Example 1 This embodiment provides a method for preparing a first type of antioxidant copper powder, the specific steps of which are as follows: (A1) Mix hydrochloric acid and anhydrous ethanol at a volume ratio of 1:1, add spherical copper powder with a particle size of 200 mesh, and stir magnetically for 20 min to remove copper oxide, cuprous oxide, etc. from the surface of the copper powder. Note: Spherical copper powder can be replaced by flake copper powder or dendritic copper powder. Since the three types of copper powder have basically similar functions, this invention only uses spherical copper powder as an example.

[0028] (A2) Mix 100 mL of ethanol with 3 mL of pyrrole as an organic monomer, and adjust the mixture to acidic conditions with hydrochloric acid; add 9 g of spherical copper powder treated in step (A1), mix well, and obtain the first mixture; (A3) After magnetically stirring the first mixture obtained in (A2) for 1 h, 4 mL of sodium chlorite solution (0.1 mol / L) as oxidant was measured and reacted for 2 h. After filtration, washing with ethanol, and vacuum drying at 60 °C for 1 h, antioxidant copper powder with a particle size of 75 μm was obtained.

[0029] Example 2 This embodiment provides a method for preparing a first type of antioxidant copper conductive adhesive, the specific steps of which are as follows: (S1) The diluent terpineol and the conductive additive adipic acid were mixed at a mass ratio of 10:1 and reacted under ultrasound for 40 min to obtain the modifier; (S2) Mix 1.5 g epoxy resin, 1.44 g curing agent methyltetrahydrophthalic anhydride, 0.3 g curing accelerator 2,4,6-tris(dimethylaminomethyl)phenol, 0.45 g modifier prepared in step (S1) and 0.2 g dispersant sodium tripolyphosphate, and stir evenly at room temperature to obtain the first mixture; (S3) Add 9 g of the antioxidant copper powder prepared in Example 1 to the first mixture prepared in step (S2), and stir at 800 rpm for 20 min (temperature controlled below 30 °C) to obtain the second mixture; (S4) The second mixture is placed in a centrifugal degassing machine and stirred to degas, to obtain a conductive copper paste. The paste is cured at 200 °C for 20 min to obtain the first antioxidant copper conductive adhesive.

[0030] Example 3 This embodiment provides a second method for preparing antioxidant copper conductive adhesive. The only difference between this method and Example 2 is that an equal amount of terpineol is used instead of the dispersant.

[0031] Example 4 This embodiment provides a third method for preparing antioxidant copper conductive adhesive. The only difference between this method and Example 2 is that no modifier is prepared, and an equal amount of terpineol is used instead of the modifier.

[0032] Example 5 This embodiment provides a second method for preparing antioxidant copper powder. The difference between this embodiment and Example 1 is that the organic monomer is aniline, and the amount used is 4 mL.

[0033] Example 6 This embodiment provides a fourth method for preparing antioxidant copper conductive adhesive. Compared with Example 2, the difference is that the antioxidant copper powder used is prepared in Example 5.

[0034] Example 7 This embodiment provides a third method for preparing antioxidant copper powder. The difference between this embodiment and Example 5 is that the amount of organic monomer used is 5 mL.

[0035] Example 8 This embodiment provides a fifth method for preparing antioxidant copper conductive adhesive. Compared with Example 2, the difference is that the antioxidant copper powder used is prepared in Example 7.

[0036] Example 9 This embodiment provides a fourth method for preparing antioxidant copper powder. The difference between this embodiment and Example 5 is that the amount of organic monomer used is 3 mL.

[0037] Example 10 This embodiment provides a sixth method for preparing antioxidant copper conductive adhesive. Compared with Example 2, the difference is that the antioxidant copper powder used is prepared in Example 9.

[0038] Comparative Example 1 This comparative example provides a method for processing ordinary copper powder. The specific steps are as follows: hydrochloric acid and anhydrous ethanol are mixed at a volume ratio of 1:1, and spherical copper powder with a particle size of 200 mesh is added. The mixture is magnetically stirred for 20 min to remove copper oxide, cuprous oxide, etc. from the surface of the copper powder, and ordinary copper powder with a particle size of 75 μm is obtained.

[0039] Comparative Example 2 This comparative example provides a method for preparing unmodified copper conductive adhesive, the specific steps of which are as follows: (S1) The diluent terpineol and the conductive additive adipic acid were mixed at a mass ratio of 10:1 and reacted under ultrasound for 40 min to obtain the modifier; (S2) Mix 1.5 g epoxy resin, 1.44 g curing agent methyltetrahydrophthalic anhydride, 0.3 g curing accelerator 2,4,6-tris(dimethylaminomethyl)phenol, 0.45 g modifier prepared in step (S1) and 0.2 g dispersant sodium tripolyphosphate, and stir evenly at room temperature to obtain the first mixture; (S3) Add 9 g of ordinary copper powder obtained from the treatment of Comparative Example 1 to the first mixture prepared in step (S2), and stir at 800 rpm for 20 min (temperature controlled below 30 °C) to obtain the second mixture; (S4) The second mixture was placed in a centrifugal degassing machine and stirred to degas, resulting in a conductive copper paste. The paste was cured at 200 °C for 20 min to obtain an unmodified copper conductive adhesive.

[0040] Comparative Example 3 This comparative example provides a method for preparing a seventh type of antioxidant copper conductive adhesive. The difference from Example 2 is that KH560 [γ-(2,3-epoxypropoxy)propyltrimethoxysilane], used as a silane coupling agent, is used in an equal amount to replace the conductive additive adipic acid.

[0041] Performance testing The copper conductive adhesive was coated and dried for performance testing. The resistivity of the conductive film was measured using an RT-3000 four-point probe resistivity tester. The results are shown in Tables 1 and 2.

[0042] Table 1. Comparison of performance test results for Examples 2, 3, 4, 6, 8, 10 and Comparative Examples 2 and 3

[0043] As shown in Table 1, Example 3, without the addition of a dispersant, exhibited a higher volume resistivity than Example 2, indicating that the dispersant is beneficial in reducing the resistivity of the conductive adhesive. Example 4, without the addition of a modifier, had a higher volume resistivity than Example 2, demonstrating that the modifier is beneficial in reducing the volume resistivity of the conductive adhesive. Table 1 also shows that the modifier has a greater effect on reducing volume resistivity than the dispersant.

[0044] As can be seen from Table 1, Comparative Example 3 used a silane coupling agent, which is currently the most commonly used method for treating copper powder, and the resulting copper has good antioxidant properties. However, compared with Examples 2, 6, 8 and 10 of this invention, the conductive adhesive prepared from copper powder treated with pyrrole / aniline has significantly better conductivity than the conductive adhesive prepared from copper powder treated with silane coupling agent.

[0045] Table 2 Comparison of Performance Test Results for Examples 2, 6, 8, and 10

[0046] As shown in Table 2, compared with Examples 2, 6, 8 and 10, Example 6 (the organic monomer is aniline and the amount is 4 mL) has the lowest volume resistivity of conductive adhesive.

[0047] Combination Figure 1 The infrared absorption spectrum comparison diagram shown shows copper powder treated with polypyrrole, 3321 cm⁻¹. -1 The absorption peak corresponding to the stretching vibration of the CN bond in polypyrrole is 1124 cm⁻¹. -1 The absorption peak corresponds to the bending vibration of the CH bond in polypyrrole; while 2047 cm⁻¹ is the peak for absorption. -1 The absorption peak corresponds to the free water adsorbed in the sample. (From...) Figure 1 It can be seen that the copper powder treated with polypyrrole has the characteristic peaks of polypyrrole, indicating that the copper powder and polypyrrole were successfully coated.

[0048] In addition, in the infrared spectrum of copper powder treated with polyaniline, 3451 cm⁻¹ -1 The absorption peak corresponding to the stretching vibration of the CN bond in polyaniline is 1628 cm⁻¹. -1 The corresponding absorption peaks for the aniline ring skeleton and C=C stretching vibrations, 1101 cm⁻¹ -1 The corresponding absorption peak for the in-plane bending vibration of the double bond CH4, at 608 cm⁻¹ -1 The corresponding intrinsic vibrational absorption peaks of polyaniline. (From...) Figure 1 It can be seen that the copper powder treated with polyaniline has the characteristic peaks of polyaniline, indicating that the copper powder and polyaniline were successfully coated.

Claims

1. A method for preparing copper conductive adhesive based on modified antioxidant copper powder, characterized in that... Prepare according to the following steps: (S1) The diluent and conductive additive are mixed and subjected to ultrasonic reaction to obtain the modifier; (S2) Mix epoxy resin, curing agent, curing accelerator, modifier and dispersant prepared in step (S1) in a mass ratio of 100:(80~110):(10~40):(15~45):(5~20) and stir until homogeneous to obtain the first mixture; (S3) Add antioxidant copper powder to the first mixture and stir to obtain the second mixture; (S4) The second mixture is degassed and cured to obtain a copper conductive adhesive based on modified antioxidant copper powder; In step (S1), the conductive additive is adipic acid; In step (S2), the curing agent is selected from one or more of tetraethylenepentamine, diethylenetriamine, polyamide, and methyltetrahydrophthalic anhydride; the curing accelerator is selected from one or more of 2,4,6-tris(dimethylaminomethyl)phenol, anhydride accelerator, benzyl dimethylamine, and quaternary ammonium salt; and the dispersant is selected from one or more of sodium hexametaphosphate, sodium tripolyphosphate, triethanolamine, and sodium polyacrylate. The antioxidant copper powder described in step (S3) is prepared according to the following steps: The solvent and organic monomer are mixed, the pH of the mixture is adjusted to acidic, copper powder is added, and the mixture is stirred to obtain a first mixture. After the first mixture is magnetically stirred, an oxidant is added and reacted. The mixture is then filtered, washed, and vacuum dried to obtain antioxidant copper powder. The organic monomer is selected from one or two of pyrrole and aniline.

2. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In step (S1), the diluent is selected from one or more of ethanol, isopropanol, and terpineol; the mass ratio of diluent to conductive additive is 10:

1.

3. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: The organic monomer is aniline.

4. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In step (S2), the curing agent used is diethylenetriamine.

5. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In step (S2), the curing accelerator used is 2,4,6-tris(dimethylaminomethyl)phenol.

6. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In the preparation steps of antioxidant copper powder, the oxidant is selected from one or two of silver nitrate and sodium chlorite; the volume-to-mass ratio of organic monomer to copper powder is (3-5) mL: 9 g.

7. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 6, characterized in that: The volume-to-mass ratio of organic monomers to copper powder is 4 mL: 9 g.

8. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In the preparation steps of antioxidant copper powder, the solvent is selected from alcohols; the volume ratio of the solvent to the organic monomer is 25-100:3-5.

9. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In the preparation of antioxidant copper powder, before mixing the solvent and organic monomers, hydrochloric acid and anhydrous ethanol are mixed, copper powder is added, and the mixture is magnetically stirred.

10. The method for preparing copper conductive adhesive based on modified antioxidant copper powder according to claim 1, characterized in that: In step (S2), the curing agent is diethylenetriamine, and the curing accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

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