A water-based conductive silver paste, a preparation method and application thereof

Abstract

This application relates to the field of functional paste technology, specifically disclosing an aqueous conductive silver paste comprising the following components: 50-60% silver-coated copper powder, 0.5-1% sodium polyacrylate, 1.5-3% sodium carboxymethyl cellulose, 0.5-1.5% polyvinyl alcohol, 0.3-2.0% co-povidone, 0.5-4.0% fumed silica, 0.2-2.0% surfactant, 0.6-1.4% co-solvent, and the balance being 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer; the silver content in the silver-coated copper powder is 25-35%; furthermore, the aqueous conductive silver paste may also contain one or more conductive filler additives, namely carbon nanotubes and silver-plated glass microspheres, at a content of 1-4%. The aqueous conductive silver paste provided by this application has advantages such as low cost, good environmental friendliness, low drying temperature, and stable performance, and has good application prospects.

Description

Technical Field

[0001] This application relates to the field of functional paste technology, specifically to an aqueous conductive silver paste and its preparation method and application. Background Technology

[0002] Conductive silver paste is a functional paste with silver powder as the main conductive component. It forms a conductive path through the contact of silver microparticles and has the characteristics of high conductivity and strong adhesion. It is currently widely used in photovoltaic cells, electronic components, flexible circuits and other fields. It is also a key material for working electrodes and reference electrodes in biosensors such as blood glucose test strips, used to form uniform electrode lines to capture microcurrent signals generated by electrochemical reactions.

[0003] Traditional conductive silver pastes are mostly oil-based systems, which often present the following problems in practical applications: First, oil-based systems generally contain organic solvents such as toluene and isopropanol, which are irritating and flammable. After printing, cleaning agents containing strong organic solvents are required, which is unfriendly to the environment and operators. Second, the silver powder content in these conductive silver pastes is usually as high as 60-80%, while the price of silver, as a precious metal, fluctuates greatly, resulting in low cost-effectiveness of these conductive silver pastes in low-end products. Third, these conductive silver pastes require high drying temperatures, often needing to be dried at 120-150℃ for 15-30 minutes, resulting in high energy consumption. Fourth, under DC electric fields and humid and hot environments, silver ions in the conductive silver paste may migrate through the micropores in the resin or along the interface, leading to poor resistance stability and making it prone to short circuits or resistance changes.

[0004] Therefore, it is of great significance to develop a conductive paste that is low-cost, environmentally friendly, low-temperature curing, and has stable performance. Summary of the Invention

[0005] In order to overcome the problems of high cost and energy consumption, poor environmental performance and high energy consumption of existing conductive silver pastes, this application provides an aqueous conductive silver paste, its preparation method and application.

[0006] In a first aspect, this application provides an aqueous conductive silver paste, which adopts the following technical solution:

[0007] An aqueous conductive silver paste comprises the following components in the following proportions: 50-60% silver-coated copper powder, 0.5-1% sodium polyacrylate, 1.5-3% sodium carboxymethyl cellulose, 0.5-1.5% polyvinyl alcohol, 0.3-2.0% copovidone, 0.5-4.0% fumed silica, 0.2-2.0% surfactant, 0.6-1.4% cosolvent, and the balance being 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution;

[0008] The weight ratio of sodium polyacrylate to sodium carboxymethyl cellulose is 1:(2.5-3.5); the weight ratio of polyvinyl alcohol to copovidone is 1:(0.8-1.3); and the weight ratio of fumed silica to surfactant is 2:(1-1.5).

[0009] The silver content in the silver-coated copper powder is 25-35%.

[0010] This application replaces the silver powder in traditional solutions with silver-coated copper powder. This reduces the amount of silver used, significantly lowering the cost of the conductive paste. Furthermore, the silver in the silver-coated copper powder serves only as a surface coating, providing contact conductivity similar to pure silver powder, ensuring the basic conductivity of the conductive paste. The dense silver coating on the surface of the silver-coated copper powder also effectively isolates the copper powder from the environment, preventing oxidation and extending the lifespan of the conductive silver paste. Sodium polyacrylate and sodium carboxymethyl cellulose, as the main binders and thickeners, provide the paste with bulk viscosity and film strength after drying, and effectively prevent the sedimentation of conductive fillers. Adjusting their ratio ensures that the conductive paste achieves sufficient printing viscosity while maintaining good flowability and dispersion stability, avoiding printing defects caused by uneven viscosity. Polyvinyl alcohol and copovidone improve the adhesion and mechanical properties of the conductive paste after film formation, ensuring the mechanical durability of the product. Fumed silica imparts rheological properties to the conductive silver paste, thinning it during printing to facilitate screen printing and thickening it at rest to prevent sagging. Surfactants reduce the surface tension of the system, improving wettability and dispersibility. Sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution, as the main solvent, is non-toxic and harmless, and the resulting conductive paste can be easily washed with water. In summary, the aqueous conductive paste provided in this application effectively solves the problems of high cost, poor environmental friendliness, and poor resistance stability of traditional conductive pastes, and has excellent application prospects.

[0011] Optionally, the silver content in the silver-coated copper powder is 30%.

[0012] In one specific implementation, the silver content in the silver-coated copper powder can be 25%, 30%, or 35%.

[0013] Optionally, the aqueous conductive silver paste may further contain one or more conductive filler additives, namely carbon nanotubes and silver-plated glass microspheres, in a content of 1-4%.

[0014] Optionally, the aqueous conductive silver paste further comprises silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:(0.5-0.8).

[0015] In one specific implementation, the weight ratio of the silver-plated glass microspheres to carbon nanotubes is 1:0.3, 1:0.5, 1:0.8, or 1:1.

[0016] Optionally, the surfactant is octylphenol polyoxyethylene ether OP-10, and the cosolvent is butanediol.

[0017] Optionally, the pH of the 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution is 6.0-7.0.

[0018] Optionally, the viscosity of the aqueous conductive silver paste is 18000-22000 mPa·s.

[0019] Secondly, this application provides a method for preparing an aqueous conductive silver paste, comprising the following steps:

[0020] Sodium polyacrylate and sodium carboxymethyl cellulose were added to sodium dihydrogen phosphate / disodium hydrogen phosphate buffer and stirred until the cellulose was completely dissolved and the solution became viscous. Then, polyvinyl alcohol, copovidone, surfactant and cosolvent were added in sequence and stirred evenly. Finally, fumed silica was added and stirred evenly to obtain cellulose slurry.

[0021] The cellulose slurry is mixed with silver-coated copper powder and stirred homogenously for 20-30 minutes. An appropriate amount of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer is added to adjust the viscosity. The mixture is allowed to stand to defoam and obtain an aqueous conductive silver paste.

[0022] Thirdly, this application provides an application of an aqueous conductive silver paste in the preparation of electrode materials, electronic components, circuit boards, and biosensors.

[0023] Optionally, the water-based conductive silver paste is dried at a temperature of 65-80°C after printing.

[0024] In one specific implementation, the drying temperature of the aqueous conductive silver paste after printing can be 65°C or 80°C.

[0025] In summary, this application has the following beneficial effects:

[0026] 1. This application uses silver-coated copper powder to replace expensive silver powder, and adjusts the silver content in the silver-coated copper powder to 25-35%, which can greatly reduce the raw material cost of conductive silver paste while ensuring the basic conductivity of conductive silver paste.

[0027] 2. The water-based conductive silver paste provided in this application uses phosphate buffer solution as a solvent, which does not contain toxic or flammable pollutants, is environmentally friendly, and the screen can be directly washed with water after printing.

[0028] 3. The water-based conductive silver paste provided in this application can be cured at 65-80℃, which will not affect the conductive filler in the conductive silver paste, and can ensure complete drying, so as to obtain a water-based conductive silver paste with good conductivity and excellent resistance stability.

[0029] 4. This application adds one or more conductive filler materials, namely carbon nanotubes and silver-plated glass microspheres, to conductive silver paste, and further selects silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:(0.5-0.8) as conductive filler materials, which can significantly improve the conductivity and resistance stability of conductive silver paste. The resistance of the resulting conductive paste is only 0.99Ω, and the resistance stability RSD value after 6 months of accelerated aging test is as low as 1.82-1.97% (<2%). Attached Figure Description

[0030] Figure 1 This is a printing effect diagram of the water-based conductive silver paste electrode obtained in Example 2 of this application after printing;

[0031] Figure 2 This is a schematic diagram of a resistance value detection method. Detailed Implementation

[0032] This application provides an aqueous conductive silver paste comprising the following components: 50-60% silver-coated copper powder, 0.5-1% sodium polyacrylate, 1.5-3% sodium carboxymethyl cellulose, 0.5-1.5% polyvinyl alcohol, 0.3-2.0% co-povidone, 0.5-4.0% fumed silica, 0.2-2.0% surfactant, 0.6-1.4% co-solvent, and the balance being 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer; the silver content in the silver-coated copper powder is 25-35%. Further, the aqueous conductive silver paste also contains one or more conductive filler additives selected from carbon nanotubes and silver-plated glass microspheres, with a content of 1-4%.

[0033] The method for preparing the aqueous conductive silver paste provided in this application includes the following steps:

[0034] Sodium polyacrylate and sodium carboxymethyl cellulose were added to sodium dihydrogen phosphate / disodium hydrogen phosphate buffer and stirred until the cellulose was completely dissolved and the solution became viscous. Then, polyvinyl alcohol, copovidone, surfactant and cosolvent were added in sequence and stirred evenly. Finally, fumed silica was added and stirred evenly to obtain cellulose slurry.

[0035] The cellulose slurry is mixed with silver-coated copper powder and stirred homogenously for 20-30 minutes. An appropriate amount of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer is added to adjust the viscosity. The mixture is allowed to stand to defoam and obtain an aqueous conductive silver paste.

[0036] In the embodiments of this application, the silver content in the silver-coated copper powder can be 25%, 30%, or 35%; the raw materials, reagents, solvents, etc. used in this application can all be obtained commercially.

[0037] The following describes this application in further detail with reference to preparation examples, embodiments, and performance testing.

[0038] Preparation Example 1

[0039] Preparation Example 1 provides a cellulose slurry.

[0040] The preparation method of the above-mentioned cellulose slurry is as follows: Weigh 100g of 0.1M, pH 6.5 sodium dihydrogen phosphate / disodium hydrogen phosphate buffer, add 2.0g of sodium polyacrylate and 6.0g of sodium carboxymethyl cellulose, stir until the cellulose is completely dissolved and the solution is viscous, then add 2.5g of polyvinyl alcohol, 2.5g of copovidone, 3.0g of octylphenol polyoxyethylene ether, and 3.0g of butanediol in sequence and stir evenly, then add 6.0g of fumed silica and stir evenly to obtain the cellulose slurry. Example 1

[0041] Example 1 provides an aqueous conductive silver paste.

[0042] The above-mentioned water-based conductive silver paste is prepared by mixing 50g of the cellulose slurry obtained in Preparation Example 1 with 51.1g of silver-coated copper powder (silver content is 30%), stirring homogenously for 30min, adding 1.1g of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer to adjust the viscosity to 20000mPa.s, allowing it to stand to defoam, and obtaining water-based conductive silver paste with a silver-coated copper powder content of 50%. Example 2

[0043] Example 2 provides an aqueous conductive silver paste.

[0044] The difference between the above embodiment and Embodiment 1 is that the amount of silver-coated copper powder added is 64.2g, and 2.5g of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer is added to adjust the viscosity, so that the silver-coated copper powder content in the resulting aqueous conductive silver paste is 55%. Example 3

[0045] Example 3 provides an aqueous conductive silver paste.

[0046] The difference between the above embodiment and Embodiment 1 is that the amount of silver-coated copper powder added is 83.0g, and 5.3g of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer is added to adjust the viscosity, so that the silver-coated copper powder content in the resulting aqueous conductive silver paste is 60%. Example 4

[0047] Example 4 provides an aqueous conductive silver paste.

[0048] The difference between the above embodiment and Embodiment 2 is that the silver content in the silver-coated copper powder is 25%. Example 5

[0049] Example 5 provides an aqueous conductive silver paste.

[0050] The difference between the above embodiment and Embodiment 2 is that the silver content in the silver-coated copper powder is 35%. Example 6

[0051] Example 6 provides an aqueous conductive silver paste.

[0052] The difference between the above embodiment and Embodiment 2 is that 4.2g of silver-coated copper powder is replaced with 4.2g of carbon nanotubes. Example 7

[0053] Example 7 provides an aqueous conductive silver paste.

[0054] The difference between the above embodiment and embodiment 2 is that 4.2g of silver-coated copper powder is replaced with 4.2g of silver-plated glass microspheres. Example 8

[0055] Example 8 provides an aqueous conductive silver paste.

[0056] The difference between the above embodiment and embodiment 2 is that 4.2g of silver-coated copper powder is replaced with a mixture of silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:1. Example 9

[0057] Example 9 provides an aqueous conductive silver paste.

[0058] The difference between the above embodiment and embodiment 2 is that 4.2g of silver-coated copper powder is replaced with a mixture of silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:0.8. Example 10

[0059] Example 10 provides an aqueous conductive silver paste.

[0060] The difference between the above embodiment and embodiment 2 is that 4.2g of silver-coated copper powder is replaced with a mixture of silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:0.5. Example 11

[0061] Example 11 provides an aqueous conductive silver paste.

[0062] The difference between the above embodiment and embodiment 2 is that 4.2g of silver-coated copper powder is replaced with a mixture of silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:0.3. Comparative Example 1

[0063] Comparative Example 1 provides an aqueous conductive silver paste.

[0064] The difference between the above embodiment and embodiment 2 is that the amount of silver-coated copper powder added is 35g, and the content of silver-coated copper powder in the resulting water-based conductive silver paste is 40%. Comparative Example 2

[0065] Comparative Example 2 provides an aqueous conductive silver paste.

[0066] The difference between the above embodiment and Embodiment 2 is that the silver content in the silver-coated copper powder is 20%. Comparative Example 3

[0067] Comparative Example 3 provides an aqueous conductive silver paste.

[0068] The difference between the above embodiment and Embodiment 2 is that 64.2g of silver-coated copper powder is replaced with a mixture of 19.26g of silver powder and 44.94g of copper powder. Comparative Example 4

[0069] Comparative Example 4 provides an aqueous conductive silver paste.

[0070] The difference between the above embodiment and embodiment 2 is that 64.2g of silver-coated copper powder is replaced with 64.2g of silver powder.

[0071] Application Example 1-11

[0072] In Application Examples 1-11, the water-based conductive silver paste provided in Examples 1-14 was printed onto the electrodes using a 150-mesh screen. Each pattern was 3.7 × 1.6 mm in size and the wet film thickness was 24 μm. After printing, the electrodes were dried at 80°C for 16 min.

[0073] The printing effect of application example 2 is as follows Figure 1 As shown.

[0074] Application Example 12

[0075] The difference between Application Example 12 and Application Example 2 is that the drying temperature after printing in Application Example 12 is 65°C.

[0076] Compare and contrast examples 1-4

[0077] The difference between Comparative Application Examples 1-4 and Application Example 2 is that the water-based conductive silver paste used in Comparative Application Examples 1-4 is derived from Comparative Examples 1-4.

[0078] Compare and contrast examples 5-6

[0079] The difference between Comparative Application Example 5-6 and Application Example 2 is that the drying temperatures after printing in Comparative Application Example 5-6 are 50℃ and 100℃, respectively.

[0080] Performance testing

[0081] The electrodes printed in Application Examples 1-12 and Comparative Application Examples 1-6 were placed in an aging chamber at 37°C and 60% humidity for accelerated aging. The resistance value was measured every month for a total of 6 months, and the average value and RSD value of the 7 test data for each electrode were calculated. The results are shown in Table 1 below.

[0082] The method for measuring resistance is as follows: Set the digital multimeter to the 200Ω range; then connect one probe of the multimeter to measurement point 1 and the other probe to measurement point 2, as shown in the diagram. Figure 2 As shown, the resistance value is measured, and the average value is taken after 5 consecutive measurements.

[0083] Table 1. Test results of resistance and accelerated aging resistance stability of water-based conductive paste.

[0084]

[0085] According to the test results in Table 1, after printing electrodes with the aqueous conductive silver paste provided in Examples 1-11, the average resistance of Application Examples 1-11 after 6 months of accelerated aging was 0.99-2.30Ω, and the RSD value was 1.82-5.93%. In contrast, after printing electrodes with the aqueous conductive silver paste provided in Comparative Examples 1-3, the average resistance of Application Examples 1-3 after 6 months of accelerated aging was as high as 4.22-5.23Ω, and the RSD value was 4.20-10.51%. Therefore, it can be seen that the aqueous conductive silver paste prepared by silver-coated copper powder in this application can effectively reduce the raw material cost, and the conductivity and resistance stability of the obtained conductive silver paste can reach a basically equivalent level to the conductivity and resistance stability of the aqueous conductive silver paste prepared by pure silver powder (Comparative Example 4).

[0086] The test results of Application Examples 2 and 4-11 show that by further adding one or more conductive filler materials, such as carbon nanotubes and silver-plated glass microspheres, to the conductive silver paste, the conductivity and resistance stability of the conductive silver paste can be further improved. In particular, the conductive silver paste obtained in Application Examples 9-10 has a resistance of only 0.99Ω and an RSD value as low as 1.82-1.97% (<2%). This indicates that by further using silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:(0.5-0.8) as conductive filler materials, a continuous conductive network can be formed within the system, thereby significantly improving the conductivity and resistance stability of the conductive silver paste.

[0087] The test results of Application Examples 2 and 12, and comparison with Application Examples 5-6, show that the resistance of the conductive silver paste gradually decreases with increasing drying temperature. When the drying temperature is too low, the conductive silver paste is not completely dried after printing, resulting in a small amount of moisture and thus higher resistance, poor resistance stability, and a higher RSD value. However, when the drying temperature is too high, the cellulose in the conductive silver paste undergoes slight splitting, causing the silver-coated copper powder to continuously oxidize in a humid and hot accelerated aging environment, further increasing the resistance and RSD value. Therefore, considering all factors, this application controls the drying temperature within the range of 65-80℃, which neither affects the conductive filler in the conductive silver paste nor hinders complete drying, ultimately obtaining a water-based conductive silver paste with good conductivity and excellent resistance stability.

[0088] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A water-based conductive silver paste, characterized in that, The components include the following: 50-60% silver-coated copper powder, 0.5-1% sodium polyacrylate, 1.5-3% sodium carboxymethyl cellulose, 0.5-1.5% polyvinyl alcohol, 0.3-2.0% copovidone, 0.5-4.0% fumed silica, 0.2-2.0% surfactant, 0.6-1.4% cosolvent, and the balance being 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution; The weight ratio of sodium polyacrylate to sodium carboxymethyl cellulose is 1:(2.5-3.5); the weight ratio of polyvinyl alcohol to copovidone is 1:(0.8-1.3); and the weight ratio of fumed silica to surfactant is 2:(1-1.5). The silver content in the silver-coated copper powder is 25-35%.

2. The aqueous conductive silver paste according to claim 1, characterized in that, The silver content in the silver-coated copper powder is 30%.

3. The aqueous conductive silver paste according to claim 1, characterized in that, The aqueous conductive silver paste also contains one or more conductive filler additives, namely carbon nanotubes and silver-plated glass microspheres, with a content of 1-4%.

4. The aqueous conductive silver paste according to claim 3, characterized in that, The aqueous conductive silver paste also contains silver-plated glass microspheres and carbon nanotubes in a weight ratio of 1:(0.5-0.8).

5. The aqueous conductive silver paste according to claim 1, characterized in that, The surfactant is octylphenol polyoxyethylene ether OP-10, and the cosolvent is butanediol.

6. The aqueous conductive silver paste according to claim 1, characterized in that, The pH of the 0.08-0.12M sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution is 6.0-7.

0.

7. The aqueous conductive silver paste according to any one of claims 1-6, characterized in that, The viscosity of the aqueous conductive silver paste is 18000-22000 mPa·s.

8. The method for preparing the aqueous conductive silver paste according to any one of claims 1-7, characterized in that, Includes the following steps: Sodium polyacrylate and sodium carboxymethyl cellulose were added to sodium dihydrogen phosphate / disodium hydrogen phosphate buffer and stirred until the cellulose was completely dissolved and the solution became viscous. Then, polyvinyl alcohol, copovidone, surfactant and cosolvent were added in sequence and stirred evenly. Fumed silica was then added and stirred evenly to obtain cellulose slurry. The cellulose slurry is mixed with silver-coated copper powder and stirred homogenously for 20-30 minutes. An appropriate amount of sodium dihydrogen phosphate / disodium hydrogen phosphate buffer is added to adjust the viscosity. The mixture is allowed to stand to defoam and obtain an aqueous conductive silver paste.

9. The application of the aqueous conductive silver paste as described in any one of claims 1-7 in the preparation of electrode materials, electronic components, circuit boards, and biosensors.

10. The application according to claim 9, characterized in that, The water-based conductive silver paste is dried at a temperature of 65-80℃ after printing.

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