Liquid metal interconnection wire for flexible electronics and preparation method thereof

Abstract

The invention discloses a liquid metal interconnection wire for flexible electronics and a preparation method of the liquid metal interconnection wire, and belongs to the technical field of flexible electronic interconnection. By means of the integrated design of the Tesla valve and the cylindrical microstructure, passive regulation and control over the flow speed of the liquid metal can be achieved without additional driving components, meanwhile, the contact area is increased through the cylindrical microstructure, and the adhesion stability of the liquid metal and a substrate is remarkably improved; the micro-nano level forming precision of an interconnection line body pattern is ensured by utilizing a collaborative process of laser etching and a light activation catalyst, and the fine interconnection requirement of flexible electronics is met; through the design of a composite mixed substrate, a flexible polymer and a light-activated catalyst are compounded, and the flexibility of the substrate and the process adaptability are both considered. The liquid metal interconnection wire for flexible electronics and the preparation method thereof have the characteristics of controllable flow velocity, high adhesiveness, excellent flexibility and the like, and can realize multi-device collaborative interconnection.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic interconnect technology, and more specifically, to a liquid metal interconnect for flexible electronics and a method for its fabrication. Background Technology

[0002] Flexible electronics, a current research hotspot in the field of electronics, boasts broad application prospects in wearable health monitoring devices, flexible display panels, and smart skin due to its bendable, foldable, and stretchable properties. Interconnects, as the core components for signal and energy transmission in flexible electronic devices, directly determine the stability and reliability of the entire system. Liquid metals, with their excellent conductivity, fluidity, and low-temperature stability, have become ideal materials to replace traditional metal wires and are widely used in flexible electronic interconnection scenarios.

[0003] However, existing liquid metal interconnect technologies still face several key bottlenecks: First, the flow of liquid metal during flexible deformation is difficult to control. Traditional straight-channel designs can easily lead to localized accumulation and breakage of the liquid metal during bending or stretching, causing signal transmission interruptions. Second, the adhesion between liquid metal and the substrate is poor. The contact area between the smooth substrate surface and the liquid metal is limited, making it prone to detachment during repeated deformation, affecting device lifespan. Third, the fabrication process has defects. Existing technologies often adopt a step-by-step approach of "forming the substrate first and then etching," resulting in low pattern forming accuracy and poor mixing uniformity between the photoactivated catalyst and the substrate, leading to unstable laser etching efficiency and low batch yield. Fourth, some substrate materials are redundantly designed, and excessive pursuit of multi-performance integration increases fabrication costs, resulting in resource waste in scenarios where substrate conductivity is not required.

[0004] Therefore, developing a liquid metal interconnect that combines flow rate control, high adhesion, high-precision molding, and stable manufacturing process, with a simple composition suitable for specific scenarios, is of great significance for promoting the industrial application of flexible electronics technology. Summary of the Invention

[0005] Based on the aforementioned problems in the existing technology, the purpose of this application is to provide a liquid metal interconnect for flexible electronics and its preparation method. Through a synergistic strategy of "structural innovation + process optimization + material simplification", focusing on flexibility and process adaptability, the liquid metal interconnect achieves controllable flow rate, high adhesion and high precision preparation, and finally obtains interconnect devices with excellent flexibility, stable performance and cost-effectiveness.

[0006] The technical solution adopted by this application to solve its technical problem is: a liquid metal interconnect for flexible electronics, comprising an interconnect body and a hybrid substrate. The interconnect body is formed on the hybrid substrate by laser etching, and the interconnect body includes a Tesla valve structure and a cylindrical microstructure. The hybrid substrate is composed of a flexible polymer and a photoactivated catalyst. The Tesla valve structure constitutes the main flow channel of the interconnect, which can slow down the flow rate of liquid metal when it flows against the flow direction of the Tesla valve. The cylindrical microstructure is distributed inside the main flow channel of the interconnect and is integrally formed with the hybrid substrate, which can increase the contact area with the fluid and thus enhance the adhesion area of ​​the liquid metal.

[0007] Furthermore, the photoactivated catalyst in the hybrid substrate is activated during laser etching, which assists in the formation of the interconnect body pattern.

[0008] Furthermore, the photoactivated catalyst contains nano-tin antimony oxide, which can improve the response efficiency of laser activation, ensure the accuracy of interconnect body pattern forming, and meet the micro-nano structure requirements of flexible electronics.

[0009] Furthermore, the flow channel width and depth of the Tesla valve structure are adjusted according to the flow rate requirements of the liquid metal, with a flow channel width of 100-500μm and a depth of 50-200μm.

[0010] Furthermore, the diameter and distribution density of the cylindrical microstructures are set according to the adhesion requirements of the liquid metal, with a diameter of 50-150 μm and a distribution density of 5-10 microstructures / mm. 2 .

[0011] Furthermore, the flexible polymer is a composite polymer containing doped carrier components. This composite system can improve the flexibility and mechanical strength of the substrate, making it suitable for the deformation application scenarios of flexible electronics.

[0012] Furthermore, the doping carrier components include polydimethylsiloxane and a curing agent. The combination of the two can balance the flexibility and structural stability of the substrate, and prevent the substrate from cracking during flexible deformation.

[0013] A method for fabricating liquid metal interconnects for flexible electronics includes the following steps: S1. Mix the flexible polymer and the photoactivated catalyst in a certain proportion, stir thoroughly to form a mixed colloid, add the curing agent and continue stirring until uniform; S2. Spin-coating the mixed colloid onto a glass slide and then degassing it under vacuum to form a substrate preform; S3. Using laser etching technology, interconnect body patterns containing Tesla valve structures and cylindrical microstructures are processed on a mixed substrate blank; S4. Prepare the chemical plating solution according to the ratio and stir it thoroughly. Place the laser-treated substrate into the solution, seal it with tin foil, and place it in a constant temperature chamber for chemical plating. S5. The structure after laser etching is cleaned to obtain the interconnect.

[0014] Furthermore, in step S1, the weight ratio of the photoactivated catalyst to the flexible polymer is 2%-5%, and the ratio of the curing agent to the flexible polymer is 1:8-1:12; in step S2, the spin coating speed is 800 rpm for 30 seconds, and the vacuum degassing time is 3 minutes; in step S3, the laser etching frequency is 50-70 kHz, the etching speed is 1500-2500 mm / s, and the etching depth is set to 50-200 μm according to the interconnect channel requirements; in step S4, the temperature of the constant temperature chamber is set to 45℃, the humidity is set to 15%, the chemical plating solution is prepared by water, copper plating solution component A, and copper plating solution component B in a ratio of 15:2:1, and the chemical plating treatment time is 6 hours.

[0015] Furthermore, in step S2, the substrate blank needs to undergo vacuum degassing before curing. The degassing vacuum degree is -0.08 to -0.12 MPa, the curing temperature is 55-65℃, and the curing time is 2-3 hours to ensure that the substrate blank is free of internal air bubbles and has a density ≥1.05 g / cm³. 3 .

[0016] The beneficial effects of this invention are: 1. Process advantages: The integrated preparation process enables a batch pass rate of over 95%, etching accuracy of ±2μm, and copper plating layer thickness uniformity of ±0.5μm; 2. Application advantages: The structural parameters are adjustable, adaptable to different liquid metals and application scenarios, and can realize the collaborative interconnection of multiple devices, making it suitable for wearable devices, flexible displays and other fields. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a liquid metal interconnect for flexible electronics according to this application; Figure 2 This is a schematic diagram of the structure of the interconnect body after it has been formed in this application; Figure 3 This is a schematic diagram of the interconnect structure after electroless copper plating in this application; Figure 4 This is a schematic diagram illustrating the application and testing of interconnects in a flexible electronics scenario in this application. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] In this invention, unless otherwise stated, the directional terms such as "up" and "down" generally refer to the directions shown in the accompanying drawings, or to the vertical, perpendicular, or gravitational direction; similarly, for ease of understanding and description, "left" and "right" generally refer to the left and right shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0021] like Figure 1-4 As shown, this application provides a liquid metal interconnect for flexible electronics, including an interconnect body and a hybrid substrate. The interconnect body is formed on the hybrid substrate by laser etching, and the interconnect body includes a Tesla valve structure and a cylindrical microstructure. The hybrid substrate is composed of a flexible polymer and a photoactivated catalyst. The Tesla valve structure constitutes the main flow channel of the interconnect, which can slow down the flow rate of liquid metal when it flows against the flow direction of the Tesla valve. The cylindrical microstructure is distributed inside the main flow channel of the interconnect and is integrally formed with the hybrid substrate, which can increase the contact area with the fluid and thus enhance the adhesion area of ​​the liquid metal.

[0022] The photoactivated catalyst in the hybrid substrate is activated during laser etching, which helps to form the interconnect body pattern.

[0023] The photoactivated catalyst contains nano-tin antimony oxide, which can improve the response efficiency of laser activation, ensure the precision of interconnect body pattern forming, and meet the micro-nano structure requirements of flexible electronics.

[0024] The width and depth of the flow channel in the Tesla valve structure are adjusted according to the flow rate requirements of the liquid metal, with a flow channel width of 100-500μm and a depth of 50-200μm.

[0025] The diameter and distribution density of the cylindrical microstructures are set according to the adhesion requirements of the liquid metal, with a diameter of 50-150 μm and a distribution density of 5-10 per mm. 2 .

[0026] Flexible polymers are composite polymers containing doped carrier components. This composite system can improve the flexibility and mechanical strength of the substrate, making it suitable for the deformation application scenarios of flexible electronics.

[0027] The doping carrier components include polydimethylsiloxane and curing agent. The combination of the two can balance the flexibility and structural stability of the substrate and prevent the substrate from cracking during flexible deformation.

[0028] Example 1 A method for fabricating liquid metal interconnects for flexible electronics includes the following steps: S1: Preparation of mixed colloids Weigh PDMS and ATO at a mass ratio of 100:3, add them to a high-speed mixing tank, and stir at 400 rpm for 10 min; then add the curing agent (mass ratio of PDMS 1:10) and continue stirring for 5 min to form a uniform mixed colloid at an ambient temperature of 25℃.

[0029] S2: Base blank forming Select a 50mm×50mm×1mm glass slide, ultrasonically clean it with 75% ethanol for 10 minutes, dry it, and then spray it with 1% silane coupling agent. Pour the mixed colloid into the center of the glass slide and spin coat it at 800r / min for 30s to form a 500μm thick colloidal film. Degas it under -0.1MPa vacuum for 3 minutes and cure it in a constant temperature oven at 60℃ for 2 hours to obtain the substrate preform.

[0030] S3: Laser Etching An ultraviolet laser etching machine was used, with the following parameters set: frequency 60kHz, etching speed 2000mm / s, power 6W, and fill interval 0.02mm; according to the designed pattern (Tesla valve channel width 300μm, depth 100μm, cylindrical microstructure diameter 100μm, density 8 per mm). 2 Etching; after etching, ultrasonic cleaning with 75% ethanol for 5 minutes, then drying.

[0031] S4: Chemical copper plating treatment Prepare the chemical plating solution: 150 mL of deionized water, 20 mL of copper plating solution component A, and 10 mL of copper plating solution component B. Adjust the pH to 12. Place the etched substrate into the solution, seal it with tin foil, and treat it in a constant temperature oven at 45°C and 15% humidity for 6 hours.

[0032] S5: Post-processing molding Rinse three times with deionized water and heat-treat in a 120℃ oven for 1 hour to obtain the finished interconnect.

[0033] Comparative Example 1 The flow channel direction is opposite to that of Example 1, and the preparation parameters are the same as those of Example 1. Comparative liquid metal interconnects are prepared.

[0034] like Figure 4 As shown in the figure, the left side represents the time when 5 μL of liquid metal was added and drained in Example 1; the right side represents the time when 5 μL of liquid metal was added and drained in Comparative Example 1.

[0035] The performance test results of Example 1 and Comparative Example 1 are as follows: 1. Flow rate control performance: In Example 1, the gallium indium alloy took 86s to flow out, while in Comparative Example 1, the gallium indium alloy took 72s to flow out, which is slightly lower than the flow rate in Comparative Example 1.

[0036] 2. Adhesion area: In Example 1, there is a cylindrical microstructure in the flow channel, and the adhesion area is 200% of that in Comparative Example 1.

[0037] The test results above show that the present invention significantly improves the core performance of flow rate regulation and adhesion stability, and is more suitable for flexible electronic scenarios that do not require substrate conductivity.

[0038] The core mechanism of this invention is: 1. Structural synergy mechanism: The Tesla valve structure utilizes the eddy current effect of fluid mechanics to achieve passive regulation of the liquid metal flow rate; the cylindrical microstructure array and the copper plating layer work together to increase the contact area and improve adhesion, forming an integrated structure of "flow rate regulation-adhesion enhancement"; 2. Process adaptation mechanism: The photoactivated catalyst ATO is rapidly activated under laser irradiation, which on the one hand assists in the precise formation of the etching pattern, and on the other hand provides active sites for chemical plating, realizing the connection between the "etching-copper plating" process. 3. Material simplification mechanism: The combination of PDMS and curing agent ensures flexibility, focuses on core performance requirements, and improves material uniformity and ease of preparation.

[0039] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0043] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A liquid metal interconnect for flexible electronics, characterized by: The interconnect line body is formed on the hybrid substrate by a laser etching process, and the interconnect line body comprises a Tesla valve structure and a cylindrical microstructure; the hybrid substrate is composed of a flexible polymer and a photo-activated catalyst; the Tesla valve structure constitutes the main flow channel of the interconnect line, and can slow down the flow rate of the liquid metal when the liquid metal flows against the Tesla valve; the cylindrical microstructure is distributed inside the main flow channel of the interconnect line and is integrally formed with the hybrid substrate, which can increase the contact area with the fluid and further increase the adhesion area of the liquid metal.

2. The liquid metal interconnect for flexible electronics of claim 1, wherein: The photo-activated catalyst in the hybrid substrate is activated during the laser etching process to assist the formation of the interconnect line body pattern.

3. The liquid metal interconnect for flexible electronics of claim 1, wherein: The photo-activated catalyst comprises nano-tin oxide antimony, which can improve the response efficiency of laser activation and ensure the accuracy of the interconnect line body pattern formation, adapting to the micro-nano structure requirements of flexible electronics.

4. The liquid metal interconnect for flexible electronics of claim 1, wherein: The flow channel width and depth of the Tesla valve structure are regulated according to the flow rate requirements of the liquid metal, with a flow channel width of 100-500 μm and a depth of 50-200 μm.

5. The liquid metal interconnect for flexible electronics of claim 1, wherein: The diameter and distribution density of the cylindrical microstructure are set according to the attachment requirement of the liquid metal, the diameter is 50-150 μm, and the distribution density is 5-10 pieces / mm 2 .

6. The liquid metal interconnect for flexible electronics of claim 1, wherein: The flexible polymer is a composite polymer containing a doped supporting component, which can improve the flexibility and mechanical strength of the substrate and adapt to the deformation application scenarios of flexible electronics.

7. The liquid metal interconnect for flexible electronics of claim 6, wherein: The doped supporting component includes polydimethylsiloxane and a curing agent, which can balance the flexibility and structural stability of the substrate to prevent cracking during flexible deformation.

8. A method for preparing a liquid metal interconnect for flexible electronics, comprising a liquid metal interconnect for flexible electronics as claimed in claims 1-7, characterized in that: The method comprises the following steps: S1, mix the flexible polymer and the photo-activated catalyst in a certain proportion, stir thoroughly to form a mixed colloid, and continue to stir uniformly after adding the curing agent; S2, spin coat the mixed colloid on a glass sheet to form a substrate blank after vacuum degassing; S3, use a laser etching process to process the interconnect line body pattern comprising a Tesla valve structure and a cylindrical microstructure on the hybrid substrate blank; S4, prepare the solution required for electroless plating in a certain proportion and stir thoroughly, place the laser-processed substrate in the solution, seal with tin paper, and then place it in a constant temperature box for electroless plating treatment; S5, clean the laser-etched structure to obtain the interconnect line.

9. The method of claim 8, wherein: In step S1, the weight ratio of the photo-activated catalyst to the flexible polymer is 2%-5%, and the ratio of the curing agent to the flexible polymer is 1:8-1:12; in step S2, the spin coating speed is 800 revolutions per minute for 30 seconds, and the vacuum degassing time is 3 minutes; in step S3, the laser etching frequency is 50-70 kHz, the etching speed is 1500-2500 mm / s, and the etching depth is set to 50-200 μm according to the flow channel requirements of the interconnect line; In step S4, the temperature of the constant temperature box is set to 45°C, the humidity is set to 15%, the electroless plating solution is prepared by mixing water, copper plating liquid component A and copper plating liquid component B in a ratio of 15:2:1, and the electroless plating treatment time is 6 hours.

10. The liquid metal interconnect for flexible electronics of claim 8, wherein: The base blank in step S2 needs to be vacuum degassed before curing, the vacuum degree of degassing is -0.08 to -0.12 MPa, the curing temperature is 55-65℃, the curing time is 2-3h, which ensures that the base blank has no internal bubbles and the density is ≥1.05g / cm 3 .

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