Nano-copper conductive ink as well as preparation method and application thereof

Abstract

The invention relates to nano-copper conductive ink as well as a preparation method and application thereof. The nano-copper conductive ink comprises nano-copper particles, repairing particles, a dispersing agent, an antioxidant and a solvent, the boiling point of the dispersing agent is T1, the melting point of the repairing particles is T2, T1 < T2 < 250 DEG C, and the repairing particles comprise Sn. According to the scheme, the Sn-containing repairing particles are introduced into the nano-copper conductive ink, and the dispersing agent with the boiling point lower than the melting point of the repairing particles is used, so that the conductivity of the conductive film can be prevented from being reduced, the mechanical strength of the conductive film is improved, and the conductive film is prevented from cracking during bending or stretching.

Description

Technical Field

[0001] The present invention relates to the field of nano copper conductive ink, and in particular to a nano copper conductive ink and a preparation method and application thereof. Background Art

[0002] The traditional etching method for printing circuits not only wastes a lot of materials, but also has a complicated preparation process and serious environmental pollution. Printed electronics technology is an advanced circuit printing method, and its core lies in the application of conductive ink. Nanosilver conductive ink has been widely used, but silver, as a precious metal, leads to the high cost of nanosilver conductive ink, which limits its application scenarios. Copper has excellent conductivity and low cost. Using copper instead of silver to prepare conductive ink has a great cost reduction advantage, but nanocopper conductive ink still has some problems that need to be solved. Dispersants need to be added to nanocopper conductive ink to prevent nanocopper from agglomerating, but these dispersants attached to the surface of nanocopper will prevent the formation of conductive paths between particles. Therefore, the conductive film printed by nanocopper conductive ink needs to be sintered to remove the dispersant. A large number of bubbles will be generated during the evaporation of the dispersant. The rupture of the bubbles will cause a large gap between the nanocopper particles, resulting in a decrease in the conductivity of the circuit formed by the accumulation of nanocopper; at the same time, the circuit with this defect is prone to cracking when subjected to stretching and bending, resulting in an open circuit. By reducing the content of the dispersant, the generation of bubbles can be reduced, but this will increase the probability of nanocopper agglomeration. CN106366769A discloses an anti-oxidation nano-copper conductive ink, a preparation method and printing application thereof, which reduces the problem of reduced conductivity caused by defects by continuously printing 50 layers, but this increases manufacturing costs and time.

[0003] Therefore, it is necessary to propose a nano copper conductive ink and a preparation method and application thereof. Summary of the invention

[0004] Based on this, it is necessary to propose a nano copper conductive ink and a preparation method and application thereof.

[0005] The first aspect of the present invention provides a nano-copper conductive ink, comprising: nano-copper particles, repair particles, a dispersant, an antioxidant and a solvent, wherein the boiling point of the dispersant is T1, the melting point of the repair particles is T2, T1<T2<250°C, and the repair particles contain Sn.

[0006] In this solution, by introducing repair particles containing Sn into the nano-copper conductive ink and using a dispersant with a boiling point lower than the melting point of the repair particles, when the ink is printed on a substrate to form a conductive film and the conductive film is sintered, when the temperature of the conductive film reaches between T1 - T2, the dispersant evaporates, thereby forming larger pores between the nano-copper particles. As the temperature of the conductive film further rises to T2 - 250 °C, the repair particles are transformed into a molten state, and can be filled into the pores formed by the evaporation of the dispersant through capillary action and react with the surface of the exposed nano-copper particles to form intermetallic compounds, thereby connecting multiple non-contact nano-copper particles, thus avoiding the reduction of the conductivity of the conductive film and also improving the mechanical strength of the conductive film to prevent it from cracking during bending or stretching.

[0007] Furthermore, the repair particles are Sn-Ag-Cu alloy. The melting point of Sn-Ag-Cu alloy is between 210 - 220 °C. For example, the melting point of Sn-Ag-Cu alloy with 96.5% Sn content, 3% silver content, and 0.5% copper content is 217 °C. This alloy has a low surface tension in the molten state, can efficiently fill pores through capillary action, and can form intermetallic compounds with nano-copper at the same time, enhancing the interfacial bonding force to avoid open circuits during the bending process of the conductive film.

[0008] Furthermore, the particle size of the repair particles is smaller than that of the nano-copper particles. Small particle size repair particles can better embed into the stacking gaps of nano-copper particles and better play the repair role.

[0009] Furthermore, the ratio of the particle size of the repair particles to that of the nano-copper particles is 1:(2 - 5). The above ratio can achieve a better repair effect, so that the conductive film has better electrical conductivity.

[0010] Furthermore, the dispersant is polyvinylpyrrolidone. As a macromolecular dispersant, polyvinylpyrrolidone can better disperse nano-copper particles.

[0011] Furthermore, the solvent contains at least one of ethanol, ethylene glycol, and water.

[0012] Furthermore, the antioxidant contains ascorbic acid. Ascorbic acid can reduce Cu2+ and prevent the formation of an oxide layer on the surface of nano-copper.

[0013] Furthermore, by weight, it contains 35 - 45 parts of nano-copper particles, 0.5 - 1 part of repair particles, 1 - 3 parts of dispersant, and 5 - 10 parts of antioxidant. If the proportion of repair particles is too low, the repair effect is not obvious; if the proportion of repair particles is too high, it will lead to an increase in the resistance of the conductive film.

[0014] The second aspect of the present application provides a method for preparing the above-mentioned nano-copper conductive ink, which includes the following steps: adding the nano-copper particles and a dispersant to the solvent, stirring evenly, then adding the repair particles, performing ultrasonic treatment for 10-20 minutes, adding the antioxidant, continuing to stir evenly, and obtaining the nano-copper conductive ink after standing.

[0015] First, disperse the nano-copper, and then ultrasonically add the repair particles to avoid agglomeration of small particles; finally, add ascorbic acid to prevent premature consumption of the reducing agent, thereby improving the process stability.

[0016] The third aspect of the present application provides an application of the above-mentioned nano-copper conductive ink, which includes the following steps: printing the nano-copper conductive ink onto a substrate to form a conductive film, sintering at T1-T2 for 5-10 minutes in an inert atmosphere, and then continuing to sinter at 20-40 °C above T2 for 10-20 minutes.

[0017] The above application method is carried out in two stages of sintering. In the first stage (T1-T2), the dispersant can be volatilized smoothly to reduce the generation of large pores; in the second stage (at 20-40 °C above T2), the molten alloy can fully fill the pores to reduce the resistance of the conductive film. Detailed Embodiments

[0018] To facilitate the understanding of the present application, the present application will be described more comprehensively below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0019] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the description of the present application in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0021] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0022] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0023] In this application, for the percentage content involved, unless otherwise specified, for solid-liquid mixtures and solid-solid mixtures, it refers to the mass percentage, and for liquid-liquid mixtures, it refers to the volume percentage.

[0024] In this application, for the percentage concentration involved, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding the component.

[0025] For the temperature parameters in this application, unless otherwise specified, it allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0026] The "particles" mentioned in this application, or substances with a defined particle size distribution, do not necessarily have a spherical shape, and may also be irregular. They can be primary particles or secondary particles. The particle size of irregular particles is calculated as the average of the maximum diameter and the minimum diameter.

[0027] Example 1: This example provides a nano-copper conductive ink, its preparation method and application.

[0028] Ink formula: 40 parts of nano-copper particles (average particle size 80 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm, melting point 217 °C), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0029] Preparation method: Add the nano-copper particles and the dispersant to the solvent, and stir magnetically (600 rpm, 30 min); then add the repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally, add the antioxidant and continue to stir (300 rpm, 10 min). After standing to defoam, the nano-copper conductive ink is obtained.

[0030] Application: The above ink is screen-printed on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. The substrate is sintered in an inert atmosphere, first sintered at 200 °C for 8 min, and then sintered at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0031] Example 2: This example provides a nano-copper conductive ink, its preparation method and application.

[0032] Ink formula: 40 parts of nano-copper particles (average particle size 80 nm), 0.5 part of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0033] Preparation method: Add nano-copper particles and dispersant to the solvent, stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add antioxidant and continue stirring (300 rpm, 10 min). After standing to defoam, nano-copper conductive ink is obtained.

[0034] Application: The above ink is screen-printed on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. The substrate is sintered in an inert atmosphere, first sintered at 200 °C for 8 min, and then sintered at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0035] Example 3: This example provides a nano-copper conductive ink, its preparation method and application.

[0036] Ink formula: 40 parts of nano-copper particles (average particle size 80 nm), 1 part of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0037] Preparation method: Add nano-copper particles and dispersant to the solvent, stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add antioxidant and continue stirring (300 rpm, 10 min). After standing to defoam, nano-copper conductive ink is obtained.

[0038] Application: The above ink is screen-printed on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. The substrate is sintered in an inert atmosphere, first sintered at 200 °C for 8 min, and then sintered at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0039] Example 4: This example provides a nano - copper conductive ink, its preparation method and application.

[0040] Ink formula: 40 parts of nano - copper particles (average particle size 80 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 40 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0041] Preparation method: Add nano - copper particles and dispersant into the solvent, stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add antioxidant and continue stirring (300 rpm, 10 min), and obtain nano - copper conductive ink after standing for defoaming.

[0042] Application: Screen - print the above - mentioned ink on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering, first sinter at 200 °C for 8 min, then sinter at 240 °C for 15 min, and complete the preparation of the conductive film after cooling.

[0043] Example 5: This example provides a nano - copper conductive ink, its preparation method and application.

[0044] Ink formula: 40 parts of nano - copper particles (average particle size 100 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0045] Preparation method: Add nano - copper particles and dispersant into the solvent, stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add antioxidant and continue stirring (300 rpm, 10 min), and obtain nano - copper conductive ink after standing for defoaming.

[0046] Application: Screen - print the above - mentioned ink on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering, first sinter at 200 °C for 8 min, then sinter at 240 °C for 15 min, and complete the preparation of the conductive film after cooling.

[0047] Example 6: This example provides a nano - copper conductive ink, its preparation method and application.

[0048] Ink formulation: 40 parts of nano-copper particles (average particle size 80 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0049] Preparation method: Add the nano-copper particles and the dispersant into the solvent, and stir magnetically (600 rpm, 30 min); then add the repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add the antioxidant and continue stirring (300 rpm, 10 min). After standing to defoam, the nano-copper conductive ink is obtained.

[0050] Application: Print the above ink onto a polyimide substrate by screen printing to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering. First, sinter at 200 °C for 8 min, then sinter at 260 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0051] Example 7: This example provides a nano-copper conductive ink, its preparation method and application.

[0052] Ink formulation: 45 parts of nano-copper particles (average particle size 80 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 1 part of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0053] Preparation method: Add the nano-copper particles and the dispersant into the solvent, and stir magnetically (600 rpm, 30 min); then add the repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally add the antioxidant and continue stirring (300 rpm, 10 min). After standing to defoam, the nano-copper conductive ink is obtained.

[0054] Application: Print the above ink onto a polyimide substrate by screen printing to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering. First, sinter at 200 °C for 8 min, then sinter at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0055] Example 8: This example provides a nano-copper conductive ink, its preparation method and application.

[0056] Ink formulation: 40 parts of nano-copper particles (average particle size 80 nm), 0.8 parts of repair particles (Sn96.5Ag3Cu0.5 alloy, average particle size 20 nm), 2 parts of dispersant polyvinylpyrrolidone, 5 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0057] Preparation method: Add nano copper particles and dispersant into the solvent, and stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally, add antioxidant and continue to stir (300 rpm, 10 min). After standing to defoam, nano copper conductive ink is obtained.

[0058] Application: Print the above ink on a polyimide substrate by screen printing to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering. First, sinter at 200 °C for 8 min, then sinter at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0059] Comparative Example 1: This example provides a nano copper conductive ink, its preparation method and application.

[0060] Ink formula: 40 parts of nano copper particles (average particle size 80 nm), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0061] Preparation method: Add nano copper particles and dispersant into the solvent, and stir magnetically (600 rpm, 30 min); then perform ultrasonic treatment (40 kHz, 15 min); finally, add antioxidant and continue to stir (300 rpm, 10 min). After standing to defoam, nano copper conductive ink is obtained.

[0062] Application: Print the above ink on a polyimide substrate by screen printing to form a conductive film with a thickness of 50 μm and a line width of 100 μm. Place the substrate in an inert atmosphere for sintering. First, sinter at 200 °C for 8 min, then sinter at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0063] Comparative Example 2: This example provides a nano copper conductive ink, its preparation method and application.

[0064] Ink formula: 40 parts of nano copper particles (average particle size 80 nm), 0.8 part of repair particles (Sn-58Bi eutectic alloy, average particle size 20 nm, melting point 138 °C), 2 parts of dispersant polyvinylpyrrolidone, 8 parts of antioxidant ascorbic acid, 50 parts of solvent (ethanol: water = 3:1, volume ratio).

[0065] Preparation method: Add nano copper particles and dispersant into the solvent, and stir magnetically (600 rpm, 30 min); then add repair particles and perform ultrasonic treatment (40 kHz, 15 min); finally, add antioxidant and continue to stir (300 rpm, 10 min). After standing to defoam, nano copper conductive ink is obtained.

[0066] Application: The above ink is screen-printed on a polyimide substrate to form a conductive film with a thickness of 50 μm and a line width of 100 μm. The substrate is sintered in an inert atmosphere. First, it is sintered at 200 °C for 8 min, and then at 240 °C for 15 min. After cooling, the preparation of the conductive film is completed.

[0067] Performance tests were carried out on the above-mentioned examples and comparative examples: The resistance of the sintered conductive film was measured by the four-probe method; a dynamic bending test machine was used to test the flexible substrate. The 100 mm * 10 mm substrate was tested with a bending radius of 3 mm, and the resistance value was measured in real time. When the change rate of the resistance value > 10% or it suddenly changed to an open circuit, the test was stopped and the number of bending failures was recorded. The experiment was repeated 10 times and the average value was recorded.

[0068] Table 1 Results of the resistance and number of bending failures of the examples and comparative examples.

[0069] Project <![CDATA[Resistivity (×10 -5 Ω·cm)]]> Number of bending failures Example 1 2.45 ＞10000 Example 2 4.21 ＞10000 Example 3 3.86 ＞10000 Example 4 4.56 ＞10000 Example 5 3.52 ＞10000 Example 6 2.78 ＞10000 Example 7 4.24 ＞10000 Example 8 3.96 ＞10000 Comparative Example 1 6.54 854 Comparative Example 2 7.31 795

[0070] According to the data in Table 1, the results of Examples 1-8 are better than those of Comparative Examples 1-2. It can be seen that in this solution, by introducing Sn-containing repair particles into the nano-copper conductive ink and using a dispersant with a boiling point lower than the melting point of the repair particles, when the ink is printed on the substrate to form a conductive film and the conductive film is sintered, when the temperature of the conductive film reaches between T1 - T2, the dispersant evaporates, thus forming larger pores between the nano-copper particles. As the temperature of the conductive film further rises to T2 - 250 °C, the repair particles are transformed into a molten state, and can be filled into the pores formed by the evaporation of the dispersant through capillary action and react with the surface of the exposed nano-copper particles to form intermetallic compounds, thereby connecting multiple non-contact nano-copper particles, thus avoiding the reduction of the conductivity of the conductive film and also improving the mechanical strength of the conductive film to prevent it from cracking during bending or stretching. In Comparative Example 1, no repair particles were added, and the repair effect on the pores could not be achieved; in Comparative Example 2, a metal with a lower melting point was used as the repair particle, and the repair particles had been transformed into a liquid state and carried away by the gas when the dispersant evaporated, so the repair effect could not be exerted, and even some conductive films showed short circuits. In Example 4, larger-sized repair particles were used, and it was difficult for the repair particles to penetrate into the gaps between the copper particles after melting. In Example 7, there was less dispersant, and the dispersion effect of nano-copper was poor, which also affected the resistivity.

[0071] The technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-mentioned 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.

[0072] The above-described embodiments merely 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 invention patent. 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 fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A nano - copper conductive ink, characterized in that It contains: nano copper particles, repair particles, a dispersant, an antioxidant and a solvent. The boiling point of the dispersant is T1, and the melting point of the repair particles is T2, where T1 < T2 < 250 °C. The repair particles contain Sn.

2. The nano-copper conductive ink according to claim 1, characterized in that, The repair particles are Sn-Ag-Cu alloy.

3. The nano-copper conductive ink according to claim 1, characterized in that, The particle size of the repair particles is smaller than that of the nano copper particles.

4. The nano-copper conductive ink according to claim 1, characterized in that, The ratio of the particle size of the repair particles to that of the nano copper particles is 1:(2 - 5).

5. The nano copper conductive ink according to claim 1, characterized in that, The dispersant is polyvinylpyrrolidone.

6. The nano-copper conductive ink according to claim 1, characterized in that The solvent contains at least one of ethanol, ethylene glycol and water.

7. The nano-copper conductive ink according to claim 1, wherein The antioxidant contains ascorbic acid.

8. The nano-copper conductive ink according to claim 1, wherein By weight, it contains 35 - 45 parts of nano copper particles, 0.5 - 1 part of repair particles, 1 - 3 parts of dispersant and 5 - 10 parts of antioxidant.

9. The preparation method of the nano-copper conductive ink according to any one of claims 1-8, characterized in that, It includes the following steps: adding the nano copper particles and the dispersant into the solvent, stirring evenly, then adding the repair particles, ultrasonic treating for 10 - 20 minutes, adding the antioxidant, continuing to stir evenly, and obtaining the nano copper conductive ink after standing.

10. The application of the nano-copper conductive ink according to any one of claims 1-8, characterized in that, It includes the following steps: printing the nano copper conductive ink onto a substrate to form a conductive film, sintering in an inert atmosphere at T1 - T2 for 5 - 10 min, and then continuing to sinter at 20 - 40 °C above T2 for 10 - 20 min.