MINI flexible light-emitting conductive film and SMT preparation technology of weldable silver paste of MINI flexible light-emitting conductive film

Abstract

The MINI flexible light-emitting conductive film comprises a substrate, a composite metal net and a light-emitting layer, the composite metal net comprises a first metal net and a second metal net, the metal wire width of the first metal net is larger than that of the second metal net, the light-emitting layer is made of organic light-emitting molecular materials, and the metal wire width of the second metal net is larger than that of the organic light-emitting molecular materials. The method comprises the following steps: firstly, preparing a substrate and silver paste, preparing a polyester film, cleaning the surface of the film to form the substrate, preparing silver powder, acetone and a thickening agent, mixing to prepare silver paste, preparing conductive ink, coating the surface of the prepared polyester film with the conductive ink, and curing by a drying oven; the circuit of the flexible film can be comprehensively connected through the SMT technology due to the weldable characteristic of the silver paste, the conductive performance between electronic elements is effectively improved, efficient current transmission is ensured, performance degradation caused by oxidation can be effectively avoided through the silver paste, and the silver paste can be accurately welded to the flexible film through the SMT technology.

Description

Technical Field

[0001] This invention relates to the field of conductive film technology, and in particular to a MINI flexible light-emitting conductive film and its SMT preparation process for solderable silver paste. Background Technology

[0002] Flexible conductive films are thin films with conductive properties, widely used in various fields such as solar cells, displays, and optoelectronics. With the widespread adoption of smartphones, tablets, wearable devices, and other consumer electronics, the market demand for thinner, more flexible electronic components and display technologies has surged. Traditional rigid displays and circuit boards cannot meet this demand, leading to the emergence of flexible electronics technology. Flexible electronics technology is characterized by its bendability, foldability, and stretchability, providing greater operability and comfort for products. In display technology, LED and OLED have become two major light-emitting technologies. They can not only transmit current through conductive films but also display images and information through light-emitting films.

[0003] In Chinese patent CN113284646B, only the conductivity of ordinary transparent conductive film can be improved, but it cannot be used to prepare light-emitting conductive film, especially the preparation process of solderable silver paste. Therefore, this invention proposes a MINI flexible light-emitting conductive film and its SMT preparation process of solderable silver paste to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a mini flexible light-emitting conductive film and its SMT fabrication process using solderable silver paste. The solderability of the silver paste allows for comprehensive connection of the flexible film's circuitry via SMT, effectively improving the conductivity between electronic components and ensuring efficient current transmission. The silver paste effectively avoids performance degradation caused by oxidation. Through SMT technology, the silver paste can be precisely soldered onto the flexible film, enabling fine circuit fabrication. This invention is suitable for mini-sized flexible light-emitting conductive films.

[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a MINI flexible light-emitting conductive film and its SMT fabrication process for solderable silver paste, comprising a substrate, a composite metal mesh, and a light-emitting layer, wherein the composite metal mesh comprises a first metal mesh and a second metal, the metal linewidth of the first metal mesh being greater than the metal linewidth of the second metal mesh, and the light-emitting layer being composed of organic light-emitting molecular materials.

[0006] Further improvements include the following steps;

[0007] Step 1: Substrate preparation and silver paste preparation. Prepare a polyester film, clean the film surface to form a substrate, and mix silver powder, acetone and thickener to prepare silver paste.

[0008] Step 2: Apply conductive ink to the surface of the prepared polyester film, and then cure it in an oven;

[0009] Step 3: Silver paste coating. The prepared silver paste is coated onto the surface of the polyester film and then dried and cured in an oven to form a solder layer that adheres to the substrate surface.

[0010] Step 4: SMT assembly. Prepare solder paste and use a screen printer to print the solder paste onto the silver soldering layer. Align the printed position of the solder paste with the solder joints in the circuit.

[0011] Step 5: Reflow soldering. Use a reflow soldering oven to solder the components at the solder joints.

[0012] Step Six: After soldering, perform functional tests on the circuit and use a multimeter to perform electrical tests on each solder joint.

[0013] A further improvement is made in the following steps: In step one, a polyester film material is selected, specifically a PET film. The film surface is cleaned with acetone to form a substrate. High-purity nano-silver powder is used, and a solvent, namely acetone, is added. A thickener is added and the mixture is stirred. The weight ratio of silver powder, acetone, and thickener is 7:2:1 to prepare a silver paste. The thickness of the silver paste layer is 10-50 μm.

[0014] A further improvement is made in step two, in which the conductive ink is prepared by dispersing graphene in a first solvent, heating and ultrasonically stirring it at a temperature of 90-110°C for at least 30 minutes, adding a second solvent to the first solution, centrifuging all solutions, and ultrasonically stirring them to obtain the graphene conductive ink, which is then coated.

[0015] A further improvement is made in step three, where silver paste is evenly coated onto the surface of the film using a screen printing mold. After coating, the silver paste is allowed to settle naturally for 10-30 minutes. The coated silver paste film is then placed in an oven for drying and curing at a temperature of 180-200°C for 30 minutes. After curing, the film is removed and placed at room temperature to cool and solidify.

[0016] A further improvement is made in step four: a screen template and solder paste are prepared, the openings on the template correspond to the soldering points in the circuit, the solder paste is evenly placed on the screen template, and the solder paste is evenly pushed across the template by the squeegee of the screen printing machine, so that the solder paste passes through the openings and is deposited on the silver paste soldering layer of the substrate. The circuit board with the printed solder paste is then transferred to the SMT placement machine, and the electronic components are placed on the solder paste to complete the entire SMT placement.

[0017] A further improvement is made in step five, where the prepared circuit board is introduced into the reflow soldering oven. The circuit board enters the preheating zone, where the temperature is 150°C-180°C. After entering the soldering zone, the temperature rises to 220°C-250°C. The solder in the solder paste melts and forms a liquid state. The solder joints and component leads are connected by the liquid solder, forming a strong solder joint, thus completing the reflow soldering.

[0018] A further improvement is made in step six, where the voltage, current, and power consumption of each node in the electrical measurement circuit are measured by grounding the black probe of a multimeter and contacting each solder point on the circuit board with the red probe, recording the voltage of each node. When measuring the current, the multimeter is connected in series with the circuit to record the current value flowing through the circuit. The power consumption is calculated by multiplying the voltage and current, using the formula P=V×I.

[0019] A further improvement is made in step two, where the first solvent is dimethylformyl, the second solvent is ethanol, and the volume ratio of the first solvent to the second solvent is 1:1.

[0020] A further improvement is that the width of the metal wires in the first metal mesh is 40μm-100μm and the length is 1cm-5cm, while the width of the metal wires in the second metal mesh is 1μm-5μm and the length is 5μm-20μm.

[0021] The beneficial effects of this invention are as follows: The silver paste used in this invention is a material with good conductivity, which can significantly improve the electrical performance of the flexible light-emitting conductive film. The solderability of the silver paste allows the circuit of the flexible film to be fully connected through the SMT process, effectively improving the conductivity between electronic components and ensuring efficient current transmission. The silver paste can effectively avoid performance degradation caused by oxidation. Through SMT technology, the silver paste can be precisely soldered onto the flexible film, and the SMT process can realize fine circuit fabrication. It is suitable for MINI-sized flexible light-emitting conductive films, improves the bonding strength between conductive filler and flexible substrate, and improves the flexibility and conductivity durability of the conductive film. The combination of silver paste and SMT process is suitable for high-frequency signal transmission and can be applied in scenarios that require high frequency and high precision, such as wireless communication and automotive electronics, to better integrate multiple functions such as light emission, sensing, and display. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of the steps of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] In document CN113284646B, a transparent substrate is formed by coating a metal particle coating liquid onto it. The transparent substrate is obtained by pre-selecting an epoxy resin adhesive and coating it onto the surface of a polyimide film. Because this substrate contains the transparent base material of the polyimide film and effectively bonds the epoxy resin, the resulting substrate not only has good light transmittance but also possesses hydroxyl and amino groups in the epoxy resin molecular chain. These groups can better bond with metal particles, thereby improving the film-forming and conductive properties of the metal particle coating liquid on the substrate, enhancing the film-forming properties of the epoxy resin on the polyimide film, and improving the obtained transparent substrate. The hydrophilic and interfacial bonding properties of the silver paste are used to further improve the film formation and conductivity of metal particles on a transparent substrate, thereby overcoming the defects of high resistance and easy detachment of traditional metal conductive films. However, this method can only be used to prepare transparent conductive films and cannot be applied to light-emitting conductive films. In this application, the combination of flexible light-emitting conductive film and silver paste can not only realize the light-emitting display function, but also integrate integrated circuits and sensors, supporting higher integration and multi-functionality. Moreover, the silver paste material itself is relatively environmentally friendly. Compared with traditional soldering materials, circuit boards prepared with silver paste can reduce the use of harmful substances and the generation of waste, and can maintain good performance for a longer period of time.

[0027] according to Figure 1 As shown, this embodiment provides a MINI flexible light-emitting conductive film and its SMT fabrication process for solderable silver paste, including a substrate, a composite metal mesh and a light-emitting layer. The composite metal mesh includes a first metal mesh and a second metal. The metal linewidth of the first metal mesh is greater than that of the second metal mesh. The light-emitting layer is composed of organic light-emitting molecular materials, namely aluminum triacetylacetone and tetraazine.

[0028] Includes the following steps;

[0029] Step 1: Substrate preparation and silver paste preparation. Prepare a polyester film, clean the film surface to form a substrate, and mix silver powder, acetone and thickener to prepare silver paste.

[0030] Step 2: Coating the conductive film. Prepare conductive ink by coating it onto the surface of the prepared polyester film, and then cure it in an oven.

[0031] Step 3: Silver paste coating. The prepared silver paste is coated onto the surface of the polyester film and then dried and cured in an oven to form a solder layer that adheres to the substrate surface.

[0032] Step 4: SMT assembly. Prepare solder paste and use a screen printer to print the solder paste onto the silver soldering layer. Align the printed position of the solder paste with the solder joints in the circuit.

[0033] Step 5: Reflow soldering. Use a reflow soldering oven to solder the components at the solder joints.

[0034] Step Six: After soldering, perform functional tests on the circuit and use a multimeter to perform electrical tests on each solder joint.

[0035] In step one, a polyester film material is selected, specifically a PET film. The film surface is cleaned with acetone to form a substrate. High-purity nano-silver powder is used, and a solvent, namely acetone, is added. A thickener is added and mixed and stirred. The weight ratio of silver powder, acetone, and thickener is 7:2:1 to prepare a silver paste. The thickness of the silver paste layer is 10-50μm. The specific steps are as follows: A acetone or other solvent is added to a stirring container, and the silver powder is slowly added to the solvent while stirring until the silver powder is completely dispersed. According to the required viscosity, an appropriate amount of thickener is added and stirring is continued to ensure that the silver powder particles are evenly distributed and stirring is continued to prepare the silver paste.

[0036] In step two, conductive ink is prepared by dispersing graphene in a first solvent, heating and ultrasonically stirring it at a temperature of 90-110°C for at least 30 minutes. Then, a second solvent is added to the first solution, and all solutions are centrifuged and ultrasonically stirred to obtain graphene conductive ink. The conductive ink is then heated and cured at a temperature not exceeding 80°C for at least 15 minutes.

[0037] In step three, the silver paste is evenly coated onto the film surface using a screen printing mold. After coating, the silver paste is allowed to settle naturally for 10-30 minutes. Then, the coated silver paste film is placed in an oven for drying and curing at a temperature of 180-200°C for 30 minutes. After curing, the film is removed and placed at room temperature to cool and solidify. After cooling, the silver paste layer is checked to ensure it adheres evenly to the film surface without cracks, bubbles, or peeling. During the drying and curing process, the solvent or volatiles in the silver paste are removed by heating, causing the silver powder in the silver paste to aggregate into a uniform layer, forming a conductive layer. The high temperature during drying and curing accelerates the bonding of silver powder particles, enhancing the adhesion between the silver paste layer and the polyester film surface, preventing the silver paste layer from peeling or falling off. The weld layer formed by the cured silver paste has good conductivity.

[0038] In step four, prepare the screen printing stencil and solder paste. The openings on the stencil correspond to the solder joints in the circuit. Place the solder paste evenly on the screen printing stencil and use the squeegee of the screen printer to push the solder paste evenly across the stencil, allowing it to pass through the openings and deposit onto the silver paste soldering layer of the substrate. Transfer the printed circuit board to the SMT placement machine, where electronic components are mounted onto the solder paste, completing the entire SMT placement process. For the printed substrate, remove excess solder paste. The SMT placement machine places the components onto the solder joints coated with solder paste, ensuring that the component leads are correctly positioned in the soldering area to avoid poor soldering or short circuits due to misalignment.

[0039] In step five, the prepared circuit board is introduced into the reflow soldering oven. The circuit board enters the preheating zone, where the temperature is 150°C-180°C. After entering the soldering zone, the temperature rises to 220°C-250°C. The solder in the solder paste begins to melt and become liquid. The solder joints and component leads are connected by the liquid solder, forming strong solder joints, thus completing the reflow soldering. The purpose of preheating is to heat the circuit board and solder paste to a certain temperature. Through heating, the solvent and volatiles in the solder paste are removed. The circuit board gradually cools after soldering, allowing the molten solder to solidify quickly and form stable solder joints. The main function of reflow soldering is to firmly solder the electronic components that have been mounted on the circuit board to the solder joints on the circuit board. Through the melting and solidification process, the solder ensures a stable electrical connection between the component leads and the circuit board.

[0040] In step six, the voltage, current, and power consumption of each node in the electrical measurement circuit are measured. The black probe of a multimeter is grounded, and the red probe is used to contact each solder joint on the circuit board. The voltage at each node is recorded. When measuring the current, the multimeter is connected in series with the circuit, and the current value flowing through the circuit is recorded. Power consumption is calculated by multiplying the voltage and current using the formula P = V × I; where P is power, V is voltage, and I is current. Excessive or insufficient current indicates short circuits and overloads in the circuit. Electrical function testing ensures that each solder joint is secure and conductive, without any cold solder joints or other soldering defects. If soldering is poor, electrical testing can help quickly identify and repair the problem, preventing it from affecting the normal operation of the entire circuit board.

[0041] In step two, the first solvent is dimethylformyl, the second solvent is ethanol, and the volume ratio of the first solvent to the second solvent is 1:1.

[0042] The first metal mesh has a wire width of 40μm-100μm and a length of 1cm-5cm, while the second metal mesh has a wire width of 1μm-5μm and a length of 5μm-20μm.

[0043] The SMT fabrication process for this MINI flexible luminescent conductive film and its solderable silver paste involves several steps. First, ensuring the film surface is free of contaminants or grease, the substrate surface is wiped with isopropanol to remove impurities. Then, a screen template is used to evenly coat the silver paste onto the substrate, ensuring the accuracy and integrity of the pattern. The coated silver paste undergoes preliminary drying in an oven. To improve conductivity and solderability, the silver paste is subjected to high-temperature treatment, baking at 200-250℃ for 10-30 minutes to ensure the silver particles sinter into a continuous conductive network. After baking, an appropriate amount of flux is applied to ensure good soldering of electronic components to the conductive film surface. The flexible film coated with silver paste and flux, along with the components, is then placed in a reflow oven. During reflow soldering, the temperature gradually increases, reaching a peak temperature of approximately 250℃, causing the solder to melt and firmly adhere to the surfaces of the components and conductive film, thus completing the soldering process.

[0044] The process is usually divided into three stages: preheating, heating, and cooling. Preheating stage: gradually increase the temperature to remove moisture from the flux. Heating stage: reach the welding temperature of 250℃ to ensure that the solder is fully melted. Cooling stage: cool rapidly to solidify the solder and ensure the stability of the solder joint. Finally, a comprehensive electrical test is performed to ensure the luminous and conductive properties.

[0045] Ordinary conductive films focus on conductivity, while light-emitting conductive films, in addition to conductivity, also need to focus on good luminous efficiency, color purity and light stability. The table below shows the test results of light-emitting conductive films and ordinary conductive films.

[0046]

[0047] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A mini flexible light-emitting conductive film, characterized in that, It includes a substrate, a composite metal mesh, and a light-emitting layer. The composite metal mesh includes a first metal mesh and a second metal mesh, wherein the metal linewidth of the first metal mesh is greater than the metal linewidth of the second metal mesh.

2. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film as described in claim 1, characterized in that: Includes the following steps; Step 1: Substrate preparation and silver paste preparation. Prepare a polyester film, clean the film surface to form a substrate, and then prepare silver powder, acetone and thickener and mix them to make silver paste. Step 2: Apply conductive ink to the surface of the prepared polyester film, and then cure it in an oven; Step 3: Silver paste coating. The prepared silver paste is coated onto the surface of the polyester film and then dried and cured in an oven to form a solder layer that adheres to the substrate surface. Step 4: SMT assembly. Prepare solder paste and use a screen printer to print the solder paste onto the silver soldering layer. Align the printed position of the solder paste with the solder joints in the circuit. Step 5: Reflow soldering, using a reflow soldering oven to solder the components at the solder joints; Step Six: After soldering, perform functional tests on the circuit and use a multimeter to perform electrical tests on each solder joint.

3. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step one, a polyester film material is selected, specifically a PET film. The film surface is cleaned with acetone to form a substrate. High-purity nano silver powder is used, along with a solvent and a thickener, and the mixture is stirred. The weight ratio of silver powder, acetone, and thickener is 7:2:1 to prepare a silver paste.

4. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step two, conductive ink is prepared by dispersing graphene in a first solvent, heating and ultrasonically stirring it at a temperature of 90-110°C for at least 30 minutes, adding a second solvent to the first solution, centrifuging all solutions, and ultrasonically stirring to obtain graphene conductive ink, which is then coated.

5. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step three, the silver paste is evenly coated onto the surface of the film using a screen printing mold. After coating, the silver paste is allowed to deposit naturally for 10-30 minutes. Then, the coated silver paste film is placed in an oven for drying and curing. The oven temperature is 180-200°C and the curing time is 30 minutes. After curing, the film is removed and placed at room temperature to cool and solidify. The thickness of the silver paste layer is 10-50 μm.

6. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step four, a screen printing stencil and solder paste are prepared. The openings on the stencil correspond to the solder joints in the circuit. The solder paste is evenly placed on the screen printing stencil, and the solder paste is evenly pushed across the stencil by the squeegee of the screen printing machine, so that the solder paste passes through the openings and is deposited onto the silver paste soldering layer of the substrate. The circuit board with the printed solder paste is then transferred to the SMT placement machine, and the electronic components are placed onto the solder paste to complete the entire SMT placement process.

7. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step five, the prepared circuit board is introduced into the reflow soldering oven. The circuit board enters the preheating zone, where the temperature is 150°C-180°C. After entering the soldering zone, the temperature rises to 220°C-250°C. The solder in the solder paste melts and forms a liquid state. The solder joints and component leads are connected by the liquid solder to form a strong solder joint, thus completing the reflow soldering.

8. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 2, characterized in that: In step six, the voltage, current, and power consumption of each node in the electrical testing circuit are measured by grounding the black probe of a multimeter and contacting each solder point on the circuit board with the red probe. The voltage of each node is recorded. When measuring the current, the multimeter is connected in series with the circuit to record the current value flowing through the circuit. The power consumption is calculated by multiplying the voltage and current using the formula P=V×I.

9. The SMT fabrication process of solderable silver paste for a MINI flexible light-emitting conductive film according to claim 4, characterized in that: In step two, the first solvent is dimethylformyl, the second solvent is ethanol, and the volume ratio of the first solvent to the second solvent is 1:

1.

10. A MINI flexible light-emitting conductive film according to claim 1, characterized in that: The first metal mesh has a wire width of 40μm-100μm and a length of 1cm-5cm, while the second metal mesh has a wire width of 1μm-5μm and a length of 5μm-20μm.

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