Node low-temperature welding method for nano-silver

Abstract

The invention relates to the technical field of nano-silver transparent conductive materials, in particular to a nano-silver node low-temperature welding method which comprises the following steps that S1, a nano-silver conductive film is pretreated and used for cleaning the surface of nano-silver; s2, performing tin immersion treatment on the nano-silver conductive thin film, wherein low-melting-point metal is used as a welding agent; s3, low-temperature welding is conducted, specifically, after tin immersion is conducted on the nano-silver, welding is conducted; and S4, cooling treatment after welding is carried out, low-temperature welding at nodes of the nano silver wires is achieved through combination of tin immersion and a nano low-temperature welding technology, the product defects that existing nano silver is large in contact resistance, high in product square resistance and the like are overcome, ultrasonic cleaning is carried out after plasma treatment, the cleaning effect is further improved, and the welding quality is improved. And the high cleanliness of the nano-silver surface is ensured, the clean nano-silver surface is beneficial to forming a firmer welding joint, and the overall welding quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nano silver transparent conductive materials, and specifically to a low-temperature welding method for nano silver nodes. Background Technique

[0002] In touch screen technology, nano silver technology has developed relatively maturely and has become a transparent conductive material that can replace ITO in terms of both price and performance. From the development in recent years, the development of nano silver has mainly focused on its aspect ratio and uniformity. How to effectively solve the problem of the lap resistance of nano silver wires is of great significance to the development of nano silver.

[0003] The preparation method of nano silver transparent conductive materials is relatively simple, and a conductive film with good performance can be obtained by using a coating technique. However, the physical lap method of nano silver wires results in a relatively large contact resistance. The increased contact resistance will reduce the conductive efficiency of the touch screen, affecting its response speed and accuracy; the increase in resistance will cause more heat to be generated during the touch operation, which may affect the long-term stability and reliability of the touch screen; the relatively high contact resistance may also cause instability in signal transmission, resulting in an increase in the recognition error rate of the touch screen. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-temperature welding method for nano silver nodes to solve the problems proposed in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A low-temperature welding method for nano silver nodes, the method comprising the following steps:

[0006] Step S1: Pretreatment of the nano silver conductive film for cleaning the surface of nano silver;

[0007] Step S2: Tin deposition treatment of the nano silver conductive film, using a low-melting-point metal as a welding agent;

[0008] Step S3: Low-temperature welding, after tin deposition on nano silver, then perform welding;

[0009] Step S4: Cooling treatment after welding.

[0010] Preferably, the pretreatment includes plasma treatment, ultrasonic cleaning, and drying of the nano silver conductive film. In the plasma treatment step, the plasma radio frequency is 10 - 30 MHz, the radio frequency power is 100 - 300 w, and at the same time, N2 / CF4 is used as the gas source, where the content of CF4 is 1 - 5%, and the plasma cleaning time is 10 - 100 seconds.

[0011] Preferably, in the ultrasonic cleaning step, the frequency of the ultrasonic cleaner is 20 kHz - 80 kHz, and the cleaning time is 5 - 20 minutes.

[0012] Preferably, in the drying step of the nano - silver conductive film, nitrogen is used as the carrier, the flow rate is 20 - 30 L / min, the drying temperature is 45 - 55 °C, and the drying time is 2 - 5 minutes.

[0013] Preferably, in the tin - immersion treatment step, a tin - immersion solution is used, wherein the tin salt content is 20 - 30 g / L, the thiourea content is 80 - 150 g / L, and the sulfonic acid content is 80 - 120 mL / L.

[0014] Preferably, the tin - immersion temperature is set at 70 - 85 °C, the tin - immersion time is within 1 minute, and the tin - immersion thickness is controlled within 100 nm.

[0015] Preferably, it includes laser pre - heating. The welding area is pre - heated by a laser beam. The laser power is controlled at 0.5 - 2 W, and the pre - heating time is set at 5 - 30 seconds to achieve a uniform pre - heating effect, improve the welding speed and reduce thermal damage. It also includes welding. The welding temperature is controlled at 100 - 120 °C, and the welding time is 1 - 3 minutes.

[0016] Preferably, a nitrogen environment is maintained during the welding process to prevent the oxidation of nano - silver.

[0017] Preferably, after welding, the nano - silver conductive film with welding points is transferred to a cooling box with a double - layer heat - insulation structure; a platinum resistance temperature sensor and a refrigeration system using semiconductor refrigeration technology are assembled inside the cooling box; according to the nano - silver material characteristics and welding process, the initial temperature of the cooling box is set 20 - 30 °C lower than the temperature of the welding points when welding is completed.

[0018] Preferably, the cooling treatment includes two stages. In the first stage, it is cooled at a cooling rate of 5 - 10 °C / min to reduce the temperature of the welding points to 50 - 60 °C lower than that when welding is completed; in the second stage, the cooling rate is adjusted to 10 - 15 °C / min and continues to cool down to 10 - 15 °C higher than the room temperature.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] By combining the tin - immersion and nano - low - temperature welding technologies, low - temperature welding at the nano - silver wire nodes is achieved, solving the product defects such as large contact resistance and high sheet resistance of existing nano - silver. A low - temperature welding method for nano - silver nodes provided by the present invention provides a feasible solution for reducing the nano - silver contact resistance and improving product performance, creating new opportunities for the development of transparent conductive materials.

[0021] First, perform plasma treatment and then ultrasonic cleaning, which further improves the cleaning effect and ensures a high cleanliness of the silver nanowire surface. The clean silver nanowire surface helps to form a stronger solder joint and is beneficial to improving the overall soldering quality. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the welding principle of the silver nanowire nodes of the present invention. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Please refer to Figure 1 , the present invention provides a technical solution: a low-temperature welding method for silver nanowire nodes. Step S1: Pretreatment of the silver nanowire conductive film, which is used to clean the surface of the silver nanowire.

[0025] Step S2: Tin deposition treatment of the silver nanowire conductive film, using a low-melting-point metal as a soldering agent.

[0026] Step S3: Low-temperature welding. After tin deposition on the silver nanowire, welding is performed.

[0027] Step S4: Cooling treatment after welding.

[0028] The pretreatment includes plasma treatment, ultrasonic cleaning, and drying of the silver nanowire conductive film. In the plasma treatment step, the plasma radio frequency is 10 - 30 MHz, the radio frequency power is 100 - 300 w, and N2 / CF4 is used as the gas source, where the CF4 content is 1 - 5%. The plasma cleaning time is 10 - 100 seconds.

[0029] In the ultrasonic cleaning step, the frequency of the ultrasonic cleaner is 20 kHz - 80 kHz, and the cleaning time is 5 - 20 minutes. In the drying step of the silver nanowire conductive film, nitrogen is used as the carrier, the flow rate is 20 - 30 L / min, the drying temperature is 45 - 55 °C, and the drying time is 2 - 5 minutes. Performing ultrasonic cleaning can further remove residual pollutants, including those particles or organic substances that may not be completely removed by plasma treatment, further improving the cleaning effect and ensuring a high cleanliness of the silver nanowire surface. The clean and highly active silver nanowire surface helps to form a stronger solder joint and is beneficial to improving the overall soldering quality.

[0030] In the stannate treatment step, a stannate solution is used, in which the tin salt content is 20 - 30 g / L, the thiourea content is 80 - 150 g / L, the sulfonic acid content is 80 - 120 mL / L, the stannate temperature is set at 70 - 85 °C, the stannate time is within 1 minute, and the stannate thickness is controlled within 100 nm. The low-temperature welding step includes laser preheating, where the welding area is preheated by a laser beam. The laser power is controlled at 0.5 - 2 W, and the preheating time is set at 5 - 30 seconds to achieve a uniform preheating effect, improve the welding speed, and reduce thermal damage. In the low-temperature welding step, a laser beam is used to preheat the welding area. A continuous fiber laser with a wavelength of 1064 nm is selected, the laser power is controlled at 1 W, the spot diameter is 0.5 mm, and the preheating time is set at 15 seconds. These laser parameters can ensure effective preheating of the welding area without damaging the thin film, bringing significant beneficial effects. Laser preheating achieves a uniform and rapid heating process by precisely controlling the heating area and temperature. This not only significantly improves the welding speed and shortens the welding cycle but also effectively reduces stress concentration and thermal deformation caused by temperature differences, thereby reducing the risk of thermal damage during welding. It also includes welding, where the welding temperature is controlled at 100 - 120 °C, the welding time is 1 - 3 minutes, and a nitrogen environment is maintained during welding to prevent the oxidation of nano silver;

[0031] After welding is completed, the nano silver conductive film with welding points is transferred to a cooling box with a double-layer heat insulation structure. Inside the cooling box, a platinum resistance temperature sensor and a refrigeration system using semiconductor refrigeration technology are installed. The deviation between the temperature value measured by the platinum resistance temperature sensor and the actual temperature value is less than 0.1 °C. According to the nano silver material characteristics and welding process, the initial temperature of the cooling box is set 20 - 30 °C lower than the temperature of the welding points at the end of welding. The cooling treatment includes two stages. In the first stage, the temperature is cooled at a rate of 5 - 10 °C / min, so that the temperature of the welding points drops 50 - 60 °C lower than that at the end of welding. In the second stage, the cooling rate is adjusted to 10 - 15 °C / min, and the temperature continues to drop to 10 - 15 °C higher than room temperature.

[0032] Step S1: Pretreatment of the nano silver conductive film. The pretreatment mainly removes the organic substances on the surface of nano silver. On the one hand, it helps to reduce the contact resistance between nano silver particles, and on the other hand, it prepares for stannate treatment. The pretreatment process can be completed using plasma and an ultrasonic cleaner. The plasma radio frequency frequency is 10 - 30 MHz, the radio frequency power is 100 - 300 w. To remove organic substances more thoroughly, N2 / CF4 is used as the gas source, where the CF4 content is 1 - 5%, the plasma cleaning time is 10 s - 100 s, and then ultrasonic cleaning is used to further remove the residual substances on the surface of nano silver. Finally, the nano silver conductive film is dried in a nitrogen environment to prevent oxidation.

[0033] Step S2: Tin deposition treatment of the nano-silver conductive film. Since the substrate of the transparent conductive film is generally not resistant to high temperatures, in order to achieve node soldering at a lower temperature, a metal with a lower melting point is introduced as a soldering agent. Tin soldering can be completed at 120 °C. Tin deposition treatment is carried out using a commercial tin deposition solution, where the tin salt content is 20 - 30 g / L, the thiourea content is 80 - 150 g / L, the sulfonic acid content is 80 - 120 mL / L, the tin deposition temperature is set at 70 - 85 °C, the tin deposition time is within 1 min, and the tin deposition thickness is controlled within 100 nm.

[0034] Step S3: Low-temperature soldering. After tin deposition on the nano-silver, in order to further enhance the bonding force of the nano-silver at the node and the adhesion of the tin layer, soldering is carried out. Since the tin layer is controlled at the nanoscale, the soldering temperature is lower than that of conventional tin soldering. The welding area is preheated by a laser beam, the laser power is controlled at 0.5 - 2 W, and the preheating time is set at 5 - 30 seconds to achieve a uniform preheating effect, improve the soldering speed and reduce thermal damage. The soldering temperature is controlled at 100 - 120 °C, and the soldering time is 1 - 3 min.

[0035] Step S4: Cooling treatment after soldering. The nano-silver conductive film with soldering points is transferred to a cooling box with a double-layer heat insulation structure. The cooling box with a double-layer heat insulation structure has a double-layer structure. The main purpose of this structure is to provide good heat insulation to reduce the influence of the external environmental temperature on the temperature inside the box, thereby maintaining the stability of the temperature inside the box; a platinum resistance temperature sensor and a refrigeration system using semiconductor refrigeration technology are assembled inside the cooling box; according to the nano-silver material characteristics and soldering process, the initial temperature of the cooling box is set 20 - 30 °C lower than the temperature of the soldering point at the end of soldering; the cooling treatment includes two stages. In the first stage, the temperature is cooled at a rate of 5 - 10 °C / min, so that the temperature of the soldering point drops to 50 - 60 °C lower than that at the end of soldering; in the second stage, the cooling rate is adjusted to 10 - 15 °C / min, and the temperature continues to drop to 10 - 15 °C higher than the room temperature. In the first stage, through a slower cooling rate, the thermal stress generated by the rapid cooling of the soldering point is reduced, avoiding the cracking of the soldering point; in the second stage, through a faster cooling rate, the temperature of the soldering point is quickly dropped to near room temperature, but a certain temperature difference is maintained to further reduce the thermal stress and ensure the stability and reliability of the soldering point.

[0036] Through the combination of tin deposition and nano low-temperature soldering technology, low-temperature soldering at the nodes of nano-silver wires is achieved, solving product defects such as large contact resistance and high sheet resistance of existing nano-silver. A low-temperature soldering method for nano-silver nodes provided by the present invention provides a feasible solution for reducing the nano-silver contact resistance and improving product performance, creating new opportunities for the development of transparent conductive materials.

[0037] The following provides an example:

[0038] The pretreatment includes plasma treatment, ultrasonic cleaning, and drying of the silver nanowire conductive film. In the plasma treatment step, the plasma radio frequency is 15 MHz, the radio frequency power is 200 w, and N2 / CF4 is used as the gas source, with the CF4 content being 3%. The plasma cleaning time is 50 seconds.

[0039] In the ultrasonic cleaning step, the frequency of the ultrasonic cleaner is 50 kHz, and the cleaning time is 10 minutes.

[0040] In the drying step of the silver nanowire conductive film, nitrogen is used as the carrier, the flow rate is 25 L / min, the drying temperature is 50 °C, and the drying time is 3 minutes.

[0041] In the stannate treatment step, a stannate solution is used, with the stannate content being 25 g / L, the thiourea content being 120 g / L, and the sulfonic acid content being 100 mL / L.

[0042] The stannate temperature is set at 75 °C, the stannate time is 50 seconds, and the thickness of the tin layer is approximately 85 nm.

[0043] In the low-temperature welding step, the welding area is preheated by a laser beam. The laser power is controlled at 1 W, and the preheating time is set at 15 seconds to achieve a uniform preheating effect, improve the welding speed, and reduce thermal damage. Welding is also included. The welding temperature is controlled at 110 °C, and the welding time is 2 minutes.

[0044] During the welding process, a nitrogen environment is maintained to prevent the oxidation of silver nanowires. After welding, the silver nanowire conductive film with welding points is transferred to a cooling box with a double-layer heat insulation structure.

[0045] The cooling box is internally equipped with a platinum resistance temperature sensor and a refrigeration system using semiconductor refrigeration technology. According to the characteristics of the silver nanowire material and the welding process, the initial temperature of the cooling box is set 25 °C lower than the temperature of the welding points at the end of welding. In the first stage, the cooling rate is 7 °C / min to cool the temperature of the welding points to 55 °C lower than that at the end of welding. In the second stage, the cooling rate is adjusted to 12 °C / min and the cooling continues until the temperature is 12 °C higher than room temperature. In the first stage, the slower cooling rate reduces the thermal stress generated by the rapid cooling of the welding points and avoids the rupture of the welding points. In the second stage, the faster cooling rate quickly reduces the temperature of the welding points to near room temperature while maintaining a certain temperature difference to further reduce the thermal stress and ensure the stability and reliability of the welding points.

[0046] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nano silver node low temperature welding method, characterized in that The method comprises the following steps: Step S1: pre-treatment of the nanosilver conductive film, for cleaning the surface of the nanosilver; Step S2: Tinning treatment of the nano silver conductive film, using a low melting point metal as a soldering agent; Step S3: low temperature soldering, after tin is deposited on the nano silver, soldering is performed; Step S4: Cooling treatment after welding.

2. The method for low-temperature welding of nanosilver nodes according to claim 1, characterized in that: The pretreatment includes plasma treatment, ultrasonic cleaning and drying of the nano silver conductive film. In the plasma treatment step, the plasma radio frequency is 10-30MHz, the radio frequency power is 100-300w, and N2 / CF4 is used as the gas source, wherein the CF4 content is 1-5%, and the plasma cleaning time is 10-100 seconds.

3. The method for low-temperature welding of nanosilver nodes according to claim 2, characterized in that: In the ultrasonic cleaning step, the frequency of the ultrasonic cleaner is 20kHz-80kHz, and the cleaning time is 5-20 minutes.

4. The method for low-temperature welding of nanosilver nodes according to claim 3, characterized in that: In the drying step of the nanosilver conductive film, nitrogen is used as a carrier, the flow rate is 20-30 L / min, the drying temperature is 45-55 degrees Celsius, and the drying time is 2-5 minutes.

5. The method for low-temperature welding of nanosilver nodes according to claim 4, characterized in that: In the tin precipitation treatment step, a tin precipitation solution is used, wherein the tin salt content is 20-30 g / L, the thiourea content is 80-150 g / L, and the sulfonic acid content is 80-120 mL / L.

6. The method for low-temperature welding of nanosilver nodes according to claim 5, characterized in that: The tinning temperature is set to 70-85°C, the tinning time is within 1 minute, and the tinning thickness is controlled within 100nm.

7. The method for low-temperature welding of nanosilver nodes according to claim 6, characterized in that: The low temperature welding step includes laser preheating, in which the welding area is preheated by a laser beam, the laser power is controlled at 0.5-2W, and the preheating time is set to 5-30 seconds, which is used to achieve a uniform preheating effect, increase the welding speed and reduce thermal damage. It also includes welding, and the welding temperature is controlled at 100-120°C, wherein the welding time is 1-3 minutes.

8. The method for low-temperature welding of nanosilver nodes according to claim 7, characterized in that: A nitrogen atmosphere was maintained during the soldering process to prevent oxidation of the nanosilver.

9. The method for low-temperature welding of nanosilver nodes according to claim 1, characterized in that: After welding is completed, the nanosilver conductive film with welding points is transferred to a cooling box with a double-layer heat insulation structure; The cooling box is equipped with a platinum resistance temperature sensor and a refrigeration system using semiconductor refrigeration technology; according to the characteristics of the nano-silver material and the welding process, the initial temperature of the cooling box is set to be 20-30°C lower than the welding point temperature when welding is completed.

10. A nano silver node low temperature welding method according to claim 9, characterized in that: The cooling process includes two stages. In the first stage, the temperature is cooled at a cooling rate of 5-10°C / min to reduce the temperature of the welding point to 50-60°C lower than when the welding is completed. In the second stage, the cooling rate is adjusted to 10-15°C / min and the temperature is continued to be reduced to 10-15°C higher than the room temperature.

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