Conductive composite material and preparation method thereof, and interconnection head

Abstract

This application relates to the field of conductive new materials technology, and particularly to a conductive composite material, its preparation method, and an interconnect connector. The preparation method includes the following steps: hydrophobically modifying metal particles to obtain modified metal particles; dispersing the modified metal particles in an elastic polymer solution, evaporating the solvent to obtain a self-assembled material; and annealing the self-assembled material to obtain the conductive composite material. The hydrophobic modification treatment helps reduce agglomeration and sedimentation, promotes uniform dispersion of metal particles, and the evaporation process allows for self-assembly to form conductive pathways within the polymer matrix. Finally, the annealing treatment significantly improves conductivity. The resulting conductive composite material can be used to connect flexible and rigid devices, exhibiting high tensile strength, bonding strength, connection stability and reliability, conductivity, and conductive stability.

Description

Technical Field

[0001] This application relates to the field of conductive new materials technology, and in particular to a conductive composite material and its preparation method, and an interconnect connector. Background Technology

[0002] In the consumer electronics field, such as flexible smartwatches and foldable displays, and in the medical electronics field, such as brain-computer interfaces and implantable medical devices, flexible electronics technology has achieved rapid development. Flexible electronics technology includes various flexible and rigid devices. Flexible devices include various flexible sensors, while rigid devices include chips, capacitors, resistors, and other electronic components. These devices are integrated into flexible electronic systems. However, a major challenge in the application of flexible electronics technology is how to achieve a stable and reliable connection between flexible and rigid devices. This is because the interconnection between flexible and rigid devices faces the significant challenge of interface mismatch between heterogeneous materials. At the contact interface, the main problems include stress concentration due to interface structure mismatch, insufficient bonding strength, significantly reduced stretchability, decreased conductivity, conductivity greatly affected by stretching, and insufficient precision.

[0003] The connection points of rigid devices primarily consist of their rigid conductors. To address the aforementioned interconnection issues, existing technologies use liquid conductors to connect flexible devices and rigid conductors, such as silver-containing inks. However, this interconnection method exhibits low bonding strength and is prone to short circuits. Other existing technologies employ soldering to connect flexible devices and rigid conductors, but this requires high-temperature processing, which can easily damage the circuitry and substrate of the flexible device. Therefore, existing interconnection technologies demonstrate significant limitations in addressing these challenges. Summary of the Invention

[0004] The purpose of this application is to provide a conductive composite material and its preparation method, as well as an interconnect connector, in order to solve the problems of poor interconnection effect between flexible devices and rigid wires in the prior art, such as insufficient bonding strength, insufficient stretchability, insufficient conductivity, and insufficient conductivity stability.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a method for preparing a conductive composite material, comprising the following steps:

[0007] Modified metal particles are obtained by hydrophobic modification of metal particles.

[0008] Modified metal particles are dispersed in an elastic polymer solution, and the solvent is evaporated to obtain a self-assembled material.

[0009] The self-assembled material is annealed to obtain a conductive composite material.

[0010] The preparation method of this application first prepares hydrophobically modified metal particles. When subsequently dispersed in an elastic polymer solution, the modified metal particles exhibit repulsive forces, making them less prone to aggregation and sedimentation, thus promoting uniform dispersion. During solvent evaporation, the repulsive forces between the particles gradually decrease, eventually leading to self-assembly into dense conductive pathways. This step represents a liquid-to-solid phase transition, with the elastic polymer gradually dissolving to form a substrate. The modified metal particles are dispersed within this substrate, resulting in a self-assembled material. Finally, annealing the self-assembled material significantly improves the conductivity of the conductive composite material, resulting in an order-of-magnitude increase in conductivity. The preparation method of this application is process-controllable, and the resulting conductive composite material exhibits stable structure and physicochemical properties. It can be used to connect flexible and rigid devices, possessing high stretchability, bonding strength, connection stability and reliability, conductivity, and conductivity stability.

[0011] Secondly, this application provides a conductive composite material prepared by the preparation method described in the above application.

[0012] The conductive composite material of this application is prepared by the above-mentioned preparation method. The material includes an elastic polymer substrate and modified metal particles uniformly dispersed therein. These particles self-assemble to form a conductive path. Finally, an annealing treatment is performed to further improve the conductivity. The resulting conductive composite material has good stretchability, strong adhesion, good connection stability, high conductivity, and good conductive stability, and can be used for interconnection between flexible devices and rigid devices.

[0013] Thirdly, this application provides an interconnect connector, the material of which includes the conductive composite material prepared by the preparation method described above.

[0014] Because the conductive composite material prepared above possesses good stretchability, conductivity, and conductivity stability, it can be used for interconnect connectors. Interconnect connectors are used to connect flexible devices and rigid wires, exhibiting good connection stability and withstanding stretching, bending, and other changes in the dynamic usage scenarios of flexible devices without easily detaching. Furthermore, they exhibit good conductivity and conductivity stability; even when the interconnect connector deforms, its conductivity remains relatively stable with minimal fluctuations, ensuring stable current signal transmission and high reliability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1This is a schematic diagram of the interconnecting connector in Embodiment 1 of this application, which connects a flexible sensor and a rigid wire respectively.

[0017] Figure 2 This is a partial structural diagram of the interconnecting connector in Embodiment 1 of this application, which connects a flexible sensor and a rigid wire respectively;

[0018] Figure 3 This is a schematic diagram of the components of the interconnect connector in Embodiment 1 of this application when connecting rigid wires;

[0019] Figure 4 This is a schematic diagram of the preparation steps of the conductive composite material and interconnect connector in Embodiment 1 of this application;

[0020] Figure 5 This is a side cross-sectional SEM image of the interconnect thin film of Embodiment 1 of this application;

[0021] Figure 6 This is a surface SEM image of the interconnect film in Embodiment 1 of this application;

[0022] Figure 7 These are test diagrams of the conductivity properties of the interconnect thin films in Examples 1 to 4 of this application;

[0023] Figure 8 These are conductivity test diagrams of the interconnect films of Examples 1-4 of this application subjected to stretching cycles.

[0024] Figure 9 These are comparative graphs showing the conductivity tests of the interconnect thin films in Embodiments 1 and 5 of this application;

[0025] Figure 10 This is a comparison diagram showing the effect of surface treatment of metal particles on the conductivity of the interconnect film in Embodiment 1 and Comparative Example 1 of this application.

[0026] Figure 11 This is a comparison diagram showing the effect of annealing treatment on the conductivity of the interconnect film in Embodiment 1 and Comparative Example 2 of this application;

[0027] Figure 12 These are test diagrams of the conductivity of the interconnecting connectors in Embodiments 1 to 4 of this application;

[0028] Figure 13 These are electrical conductivity test diagrams of the interconnecting connectors in Embodiments 1-4 of this application subjected to tensile cycles.

[0029] Figure 14 This is a comparison diagram of the bonding force between the interconnect connector of Example 1 and the commercial interconnect materials of Comparative Examples 3-6 used for connecting flexible sensors and rigid wires;

[0030] Figure 15 This is a side optical photograph of the interconnect connector connecting rigid wires in Example 1;

[0031] Figure 16 This is a physical diagram of how the interconnecting connector in Example 1 connects the flexible sensor and the rigid wire. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items.

[0035] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0036] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0037] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0038] Some terms explained: Conductivity stability: The property of a conductive material to maintain stable resistance when subjected to deformations such as stretching and bending. Ideally, interconnect materials should have good conductivity stability, ensuring stable resistance in the dynamic application scenarios of flexible electronics and preventing impact on signal transmission stability, accuracy, and reliability. However, in existing technologies, the conductivity of most conductive materials decreases significantly after stretching, resulting in decreased conductivity and increased resistance. Therefore, if such materials are used for interconnecting flexible and rigid devices in flexible electronics, the resistance of the interconnect material will change with the variations in the flexible application scenario, leading to unsatisfactory signal stability, signal strength, reliability, and accuracy.

[0039] The first aspect of this application provides a method for preparing a conductive composite material, comprising the following steps:

[0040] S10: Hydrophobic modification treatment is performed on metal particles to obtain modified metal particles;

[0041] S20: Modified metal particles are dispersed in an elastic polymer solution, and the solvent is evaporated to obtain a self-assembled material;

[0042] S30: Anneal the self-assembled material to obtain a conductive composite material.

[0043] The preparation method of this application first prepares hydrophobically modified metal particles. When subsequently dispersed in an elastic polymer solution, the modified metal particles exhibit repulsive forces, making them less prone to aggregation and sedimentation, thus promoting uniform dispersion. During solvent evaporation, the repulsive forces between the particles gradually decrease, eventually leading to self-assembly into dense conductive pathways. This step represents a liquid-to-solid phase transition, with the elastic polymer gradually dissolving to form a substrate. The modified metal particles are dispersed within this substrate, resulting in a self-assembled material. Finally, annealing the self-assembled material significantly improves the conductivity of the conductive composite material, resulting in an order-of-magnitude increase in conductivity. The preparation method of this application is process-controllable, and the resulting conductive composite material exhibits stable structure and physicochemical properties. It can be used to connect flexible and rigid devices, possessing high stretchability, bonding strength, connection stability and reliability, conductivity, and conductivity stability.

[0044] Step S10 is a hydrophobic modification treatment step. In the embodiments, the metal particles may include at least one of silver, gold, and copper, and may be elemental metals or alloys, all of which have good electrical conductivity. Furthermore, according to the preparation method of this application, the particle size of the metal particles has a wide range of selection; both small and large particle preparation methods can achieve similar high performance, demonstrating the strong applicability of the preparation method. In the embodiments, the Dv50 particle size of the metal particles can be 0.01–1 μm, and in exemplary examples, it may include, but is not limited to, any value or any two of 0.01 μm, 0.08 μm, 0.2 μm, 0.4 μm, 0.6 μm, and 1 μm. In the embodiments, the metal particles can be prepared by chemical reduction or by using existing finished metal particles.

[0045] The hydrophobic modification treatment is mainly to ensure that when the modified metal particles are dispersed in the elastic polymer solution in the subsequent step S20, there is a repulsive force between them, making them less prone to agglomeration and sedimentation. This promotes uniform dispersion, resulting in a more uniform component distribution in the final conductive composite material, improving connection stability, conductivity stability, and signal reliability during interconnection. If the metal particles agglomerate or settle, localized agglomeration areas will exist in the final conductive composite material. While these localized agglomeration areas have good conductivity, their elasticity is low, and they are incompatible with the mechanical and electrical properties of other areas in the composite material. Ultimately, this leads to low connection strength and poor connection stability between the conductive composite material and rigid and flexible devices, large fluctuations in interconnect resistance, unstable current, and affects signal accuracy, resulting in an unsatisfactory interconnection effect.

[0046] In some embodiments, hydrophobic modification can be achieved by modifying the metal particles with a modifier, which may include at least one of thiols and silanes. The metal particles can be dispersed in an ethanol solvent, and then the modifier can be added and stirred thoroughly, for example, at a stirring speed of 500 r / min for 2 to 4 hours, until the modifier has fully interacted with the surface of the metal particles to complete the modification. Then, the ethanol is removed by centrifugation and washing to obtain the modified metal particles. In an exemplary example, when the modifier is a thiol, the thiol may include at least one of propanethiol, octylthiol, and dodecylthiol, with propanethiol being a preferred choice. The sulfur atoms in the thiol have a strong binding effect with the metal atoms, which can form stable metal-sulfur bonds, such as Ag-S bonds, forming a hydrophobic coating layer, which greatly improves the dispersibility of the modified metal particles. In addition, thiol modification can not only be a hydrophobic modification, but also help improve the compatibility of the modified metal particles with elastic polymers. In some embodiments, the mass ratio of the modifier to the metal particles can be (2 to 3):1 to achieve a higher hydrophobic modification effect.

[0047] Step S20 is the self-assembly process of the metal particles. An elastic polymer solution can be prepared first. The elastic polymer may include at least one of styrene-ethylene-butene-styrene block copolymer (SEBS), polydimethylsiloxane (PDMS), and polyimide (PU), possessing good stretchability. The solvent can be a volatile solvent, including at least one of toluene, ethanol, and n-hexane, with toluene being optional. During preparation, the elastic polymer particles can be added to the solvent and heated and stirred at 80–100°C to dissolve them. The concentration of the elastic polymer solution can be 15 wt%.

[0048] The modified metal particles are then dispersed in an elastic polymer solution. This dispersion can be achieved either by directly adding the modified metal particles to the elastic polymer solution, or by using the following steps:

[0049] S21: The modified metal particles are dispersed in a dispersion to obtain a slurry;

[0050] S22: Mix the slurry and the elastic polymer solution.

[0051] Because the modified metal particles have undergone hydrophobic modification, step S21 first disperses the modified metal particles in a dispersion liquid. This reduces agglomeration and sedimentation of the modified particles in the slurry, improving dispersibility and facilitating the uniform dispersion of the modified metal particles in the elastic polymer solution in step S22. The dispersion liquid can be a volatile dispersion liquid, including at least one of toluene, ethanol, and n-hexane, and can be a mixed dispersion of toluene, ethanol, and n-hexane. In the embodiment, the modified metal particles can be added to the dispersion liquid and subjected to ultrasonic dispersion treatment to uniformly disperse the modified metal particles into a slurry. Then, step S22 further mixes the slurry and the elastic polymer solution, which is more conducive to uniform mixing and uniform dispersion of the modified metal particles.

[0052] In some embodiments, the mass ratio of the elastic polymer to the modified metal particles in step S20 is (2-3):(7-8), which may include, but is not limited to, any ratio of 2:8, 3:7 or any two of these ratios. The modified metal particles and elastic polymer in the final conductive composite material obtained by these mass ratios can maintain the corresponding ratio, so that the conductive composite material takes into account the stretchability, connection stability, conductivity, and conductivity stability.

[0053] In step S20, the evaporation process causes the solvent to gradually evaporate, and the elastic polymer gradually dissolves to form the substrate. As the solvent evaporates, the repulsive forces between the modified metal particles, which were initially mutually repelling in the solvent, gradually decrease. During the transition from liquid to solid phase, the modified metal particles gradually approach each other and spontaneously self-assemble, forming efficient conductive pathways and dispersing within the substrate. Furthermore, because the modified metal particles underwent hydrophobic modification in step S10, they are less prone to sedimentation and agglomeration during this evaporation process. In this embodiment, the evaporation process can include any one of natural evaporation, reduced pressure evaporation, or heated evaporation. The solvent can be a volatile solvent that evaporates at room temperature and pressure, or a solvent that can evaporate under reduced pressure or heating conditions. Natural evaporation can be achieved by allowing the container to stand in a ventilated area for a period of time, such as one day. Reduced pressure evaporation can be achieved by gradually reducing the pressure in a container to accelerate evaporation and remove vapors, potentially reaching a vacuum. Heated evaporation can accelerate the evaporation rate, but the temperature needs to be appropriate; if bubbles are generated or the solvent churns, it will hinder the dispersion and self-assembly of the modified metal particles. Evaporation can be performed by placing the mixture in a mold, and after evaporation, a conductive composite material of the desired shape is obtained.

[0054] Step S30 is the annealing process. The self-assembled material obtained in step S20, if used to connect flexible and rigid devices, already possesses a certain bonding strength and stretchability, but its conductivity still falls short of requirements. Even increasing the content of modified metal particles only results in limited improvement in conductivity. The applicant's research shows that annealing the self-assembled material can significantly improve the conductivity of the resulting conductive composite material. In some embodiments, the annealing process also causes color changes in the self-assembled material, increasing its conductivity by 7-9 orders of magnitude. That is, the conductivity of the conductive composite material obtained after annealing is 10 times that of the self-assembled material before annealing. 7 ~10 9 The conductivity is doubled, fully meeting the conductivity requirements of interconnect materials. In some embodiments, the annealing temperature can be 100℃ to 200℃, including but not limited to any value or any two of 100℃, 130℃, 170℃, and 200℃, and the annealing time can be 20 to 60 minutes. The annealing can be performed on a heating table.

[0055] After obtaining the conductive composite material, it can be further molded and processed. The conductive composite material has excellent processing performance and can be processed by cutting and other processes. The cut edges are neat, without burrs or cracks, which further ensures the stability and reliability of interconnection. It can achieve high-resolution patterning, meet the interconnection requirements at the micron level, and can be used for the interconnection of high-density, miniaturized electronic devices.

[0056] The second aspect of this application provides a conductive composite material prepared by the preparation method described in the above application.

[0057] The conductive composite material of this application embodiment is prepared by the above preparation method. The material includes an elastic polymer substrate and modified metal particles uniformly dispersed therein. These particles self-assemble to form a conductive path. Finally, an annealing treatment is performed to further improve the conductivity. The resulting conductive composite material has good stretchability, strong adhesion, good connection stability, high conductivity, and good conductive stability, and can be used for interconnection between flexible devices and rigid devices.

[0058] In the embodiments, the mass percentage of modified metal particles in the conductive composite material can be 70% to 80%, including but not limited to any value or any two of 70%, 73%, 75%, 77%, and 80%. At this mass percentage, the conductive composite material can achieve a balance between stretchability, adhesion, connection stability, conductivity, and conductive stability. In particular, at this mass percentage, its conductive stability is very ideal; even under long-term cyclic stretching and dynamic working environments, the resistance hardly changes. The resistance is also very low, which helps reduce energy loss during current transmission, significantly improves the transmission efficiency of the device, and also enhances the stability and integrity of signal transmission, reduces signal delay and distortion, and facilitates high-quality connections between flexible and rigid devices, thereby improving the high performance and stable operation of flexible electronic systems.

[0059] In the embodiments, the conductive composite material can be in the form of a thin film, which facilitates the connection between flexible devices and rigid devices.

[0060] A third aspect of this application provides an interconnect connector, the material of which includes the conductive composite material prepared by the preparation method of the above-described application embodiments.

[0061] Because the conductive composite material prepared above possesses good stretchability, conductivity, and conductivity stability, it can be used for interconnect connectors. Interconnect connectors are used to connect flexible devices and rigid wires, exhibiting good connection stability and withstanding stretching, bending, and other changes in the dynamic usage scenarios of flexible devices without easily detaching. Furthermore, they exhibit good conductivity and conductivity stability; even when the interconnect connector deforms, its conductivity remains relatively stable with minimal fluctuations, ensuring stable current signal transmission and high reliability.

[0062] The shape of the interconnect can be, but is not limited to, block, columnar, spherical, strip, or layered. In some embodiments, the interconnect may include a first conductive film and a second conductive film stacked together, and the materials of the first and second conductive films include conductive composite materials. The aforementioned conductive composite material can be formed into a film to create a conductive film, and then the two conductive films are stacked together. This allows rigid wires to be bonded between the two conductive films, further improving the bonding stability between the interconnect and the rigid wires. In particular, when the elastic polymer includes at least one of SEBS, PDMS, and PU, the bonding force between the two conductive films is stronger.

[0063] In some embodiments, the interconnect connector can be strip-shaped, with one end connected to a rigid wire and the other end connected to a flexible device. The connection method between the rigid wire and the interconnect connector may include the following steps: inserting one end of the rigid wire between a first conductive film and a second conductive film, and performing a hot-pressing process. The hot-pressing temperature can be 200–400°C, the time can be 0.5–6 min, and the pressure can be 100–300 kPa. This hot-pressing process tightly bonds the two conductive films together without the need for adhesives or other components. The rigid wire is hot-pressed between the two conductive films, and the opposing surfaces of the conductive films are also compressed into a concave shape by the rigid wire. Therefore, the contact between the wire and the conductive film changes from line contact to surface contact and three-dimensional contact, which is beneficial to improving connection stability and conductivity. Such an interconnect connector combined with a rigid wire not only has excellent bonding strength but also exhibits outstanding environmental stability, able to withstand harsh conditions such as acid and alkali corrosion and temperature changes, demonstrating extremely high reliability.

[0064] Rigid conductors can be common copper conductors. In this embodiment, surface treatment of the conductors can further improve the reliability, stability, and durability of the connection between the conductors and interconnects. Surface cleaning followed by surface modification can be performed first. Specifically, one end of the conductor can be stripped, cleaned with solutions such as deionized water, ethanol, and acetone, then immersed in a silane coupling agent for 10-30 minutes, removed, immersed in ethanol for 1 minute, and then air-dried. The molecular structure of the silane coupling agent contains organic functional groups (such as amino, epoxy, and vinyl groups) and hydrolyzable inorganic groups (such as methoxy and ethoxy groups). After binding to the metal surface of the conductor, it forms chemical bridges with the elastic polymer in the interconnect, thereby increasing the bonding force between the conductor and the interconnect. In this embodiment, the morphology of the rigid conductor can also be optimized. 3D printing technology can be used to design one end of the conductor as a paddle-shaped structure. When this structure is hot-pressed into the middle of the conductive film, it further enhances the mechanical strength, reliability, and durability of the connection with the interconnect.

[0065] The other end of the interconnect is connected to a flexible device. The flexible substrate of the flexible device can be an elastic polymer (such as SEBS). The connecting wires or electrodes can be gold wires (or silver wires, etc.) placed on the elastic polymer. Then, the other end of the interconnect is directly attached to the gold wire and subjected to hot pressing. The hot pressing parameters for rigid wires described above can be used, and only 30 seconds of hot pressing is required. In this way, the flexible sensor can be adhered and bonded to the other end of the interconnect through the biphasic nano-dispersed interface (BIND) formed by the gold (or silver) nanomaterial and the elastic polymer.

[0066] This interconnect can be used in flexible electronics. In one embodiment, it can be used in flexible displays, such as smartphones, tablets, and foldable devices, for connecting flexible displays to rigid circuit boards. This improves connection stability, signal transmission reliability, and device durability. In another embodiment, it can also be used in wearable devices: smartwatches, smart bracelets, and other wearable devices typically include flexible components (such as wristbands) and rigid components (such as chips and sensors). This interconnect material effectively connects these components, improving the stability of the device under complex environments such as bending and stretching.

[0067] This interconnect can also be used in medical wearable detectors. In the medical field, wearable devices are used to monitor patients' physiological signals (such as heart rate, blood pressure, body temperature, etc.) in real time. These devices typically require connecting flexible sensors to rigid data processing and display systems. The interconnect in this application embodiment is designed to facilitate efficient signal transmission while maintaining the comfort and durability of the device.

[0068] This interconnect connector can also be used in implantable medical devices. Some implantable medical devices (such as pacemakers, neurostimulators, etc.) require connecting flexible electrodes to rigid electronic components. The interconnect connector of this application provides a stable electrical connection while adapting to the complex environment inside the human body.

[0069] The following description is based on specific embodiments.

[0070] Example 1

[0071] This embodiment provides a conductive composite material, its preparation method, and an interconnect connector. The preparation method is as follows: Figure 4 As shown, it includes the following steps:

[0072] S1: Preparation of Ag metal nanoparticles: Silver nanoparticles were prepared by reducing silver nitrate with ethylene glycol at 180℃ using polyvinylpyrrolidone (PVP) as a surfactant. After the reaction, ethanol was used as a washing agent, and the nanoparticles were centrifuged four times at 13000 r / min to remove residual ethylene glycol, PVP, and other reactants, ultimately obtaining pure silver nanoparticles with a Dv50 particle size of 80 nm. The residual ethanol on the surface can reduce the oxidation of silver.

[0073] S2: Surface modification and dispersion of Ag metal nanoparticles: 0.15 g of metal nanoparticles were dispersed in 30 mL of ethanol, followed by the addition of 400 μL of propanethiol. The mixture was stirred at 500 r / min for 3 hours to complete the surface modification. After the modification was completed, the nanoparticles were washed four times by centrifugation with ethanol to remove the residual reactants and obtain the modified silver nanoparticles.

[0074] After the modified silver nanoparticles were transferred to a beaker and dried, 1 mL of toluene, 1 mL of ethanol, and 1 mL of n-hexane were added as a dispersion solution. The mixture was then ultrasonically dispersed in an ultrasonic cleaner for 10 minutes to ensure uniform dispersion of the modified silver nanoparticles and obtain a dispersion solution.

[0075] S3: Preparation of polymer solution and mixing with metal nanoparticles: Using toluene as solvent, an appropriate amount of SEBS polymer particles were added, and the mixture was heated and stirred overnight at 80-100℃ to prepare a polymer solution with a mass fraction of 15 wt%.

[0076] The modified silver nanoparticle dispersion obtained in step S2 was stirred at a speed of 250 r / min, and then the above-mentioned 15% wt polymer solution was slowly added dropwise. First, about 2 mL was added, and then the amount of both was adjusted so that the mass ratio of modified silver nanoparticles to polymer SEBS in the final mixed dispersion was 8:2. After the addition was completed, the cup was sealed and heated and stirred at 60°C for 15 minutes to ensure uniform mixing.

[0077] S4: Formation of solid interconnect film: After cleaning the mold with solutions such as deionized water, ethanol, and acetone, pour the above mixed dispersion into the mold and place it in a fume hood for natural evaporation for 1 day to perform solvent self-evaporation treatment, forming a black self-assembled material.

[0078] S5: Annealing and Separation: The mold is placed on a heating table and heated at 165°C for 10 minutes. The black self-assembled material gradually turns yellow, yielding a conductive composite material. The conductive composite material includes a SEBS polymer matrix and metal nanoparticles dispersed therein, with the modified metal nanoparticles comprising 80% by mass. Figure 3As shown, the conductive composite material is in the form of a thin film. It is removed from the mold by mechanical peeling and is called an interconnect film (or interconnect material). Then it is cut to obtain a first interconnect film (first interconnect material) and a second interconnect film (second interconnect material). Both have a thickness of 160 μm, one is about 10 mm long and the other is about 5 mm long. They have the same width and are both larger than the diameter of the rigid wire.

[0079] S6: Surface cleaning and surface modification of commercial wires: After removing the insulation from one end of the commercial rigid wire, clean it with solutions such as deionized water, ethanol, and acetone. Then soak the wire in silane coupling agent for 20 minutes, remove it, soak it in ethanol for 1 minute, and air dry it for later use.

[0080] S7: Addition of the interconnect film, wires, and encapsulation layer by hot pressing: One end of the surface-treated rigid wire is sandwiched between two interconnect films (i.e., the first and second interconnect materials in step S5), and hot-pressed at 400°C for 4 minutes to achieve the connection between the interconnect film and the rigid wire. Figure 3 and Figure 2 As shown, two interconnecting films form an interconnect connector. The two interconnecting films at the end connecting the rigid wire are flush, while the longer interconnecting film at the other end exceeds 5 mm in length and is used to connect the gold wire (gold conductor) of the flexible sensor. Figure 1 , Figure 2 As shown, the flexible sensor includes a polymer substrate (SEBS flexible substrate), as well as electrode points and gold wires bonded to the polymer substrate. The part of the interconnect film extending beyond the other end of the interconnect connector is attached to the gold wires and hot-pressed at 400°C for 30 seconds. The other end of the interconnect connector is then tightly bonded to the gold wires of the flexible sensor.

[0081] like Figure 1 As shown, this achieves the interconnection between flexible and rigid devices. The flexible device includes a polymer substrate, electrode points, and gold wires, while the rigid device includes a rigid chip and rigid wires. Interconnectors (interconnect materials) connect the two. Finally, a layer of ordinary polymer film is encapsulated in the area of ​​the interconnector using a simple thermoforming method as a protective layer to enhance the reliability and durability of the interconnector. A large piece of epoxy resin can also be encapsulated further for enhanced protection, such as... Figure 16 As shown.

[0082] Example 2

[0083] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that in step S3, the mass ratio of modified silver nanoparticles to polymer SEBS is changed to 7.5:2.5. In the final conductive composite material, the mass percentage of modified metal nanoparticles is 75%, and all other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0084] Example 3

[0085] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that in step S3, the mass ratio of modified silver nanoparticles to polymer SEBS is changed to 7:3. In the final conductive composite material, the mass percentage of modified metal nanoparticles is 70%, and all other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0086] Example 4

[0087] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that in step S3, the mass ratio of modified silver nanoparticles to polymer SEBS is changed to 6.5:3.5. In the final conductive composite material, the mass percentage of modified metal nanoparticles is 65%, and all other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0088] Example 5

[0089] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that in step S1, the reduction temperature is changed to 220℃, and the particle size of the obtained silver nanoparticles Dv50 becomes 0.2 μm. All other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0090] Example 6

[0091] The embodiments provide conductive composite materials and their preparation methods, as well as interconnecting connectors. The only difference from Embodiment 1 is that in step S3, SEBS is replaced with PDMS polymer particles. All other aspects are the same. The differences from Embodiment 1 are described in Table 1 below.

[0092] Example 7

[0093] The embodiments provide conductive composite materials and their preparation methods, as well as interconnecting connectors. The only difference from Embodiment 1 is that in step S3, SEBS is replaced with PU polymer particles. All other aspects are the same. The differences from Embodiment 1 are recorded in Table 1 below.

[0094] Example 8

[0095] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that step S1 is changed to the preparation of gold nanoparticles, and the silver nitrate raw material is replaced with chloroauric acid. All other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0096] Example 9

[0097] This embodiment provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that step S1 is changed to the preparation of copper nanoparticles, and the silver nitrate raw material is replaced with copper acetate. All other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0098] Comparative Example 1

[0099] This comparative example provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that step S2 does not involve thiol modification, but instead directly disperses metallic silver particles into a slurry for use in subsequent step S3. All other aspects are the same. The differences from Example 1 are described in Table 1 below.

[0100] Comparative Example 2

[0101] This comparative example provides a conductive composite material and its preparation method, as well as an interconnect connector. The only difference from Example 1 is that step S5 does not involve annealing, but instead uses the black interconnect material directly as the final interconnect material for subsequent steps. All other aspects are the same. The differences from Example 1 are recorded in Table 1 below.

[0102] Comparative Example 3

[0103] This comparative example provides interconnect material, which is anisotropic conductive adhesive, specifically 3M's 7303 model.

[0104] Comparative Example 4

[0105] This comparative example provides interconnect material as zebra paper, specifically the 3610*50 mm model from Chuangli Silicone Rubber Co., Ltd.

[0106] Comparative Example 5

[0107] This comparative example provides interconnect material in the form of silver ink, specifically the Ausbond 3813 model.

[0108] Comparative Example 6

[0109] This comparative example provides interconnect material, which is carbon tape, specifically Nisshin Corporation's 731 model.

[0110] The differences between the above embodiments and comparative examples are shown in Table 1:

[0111]

[0112] Relevant performance tests and results analysis

[0113] 1. Relevant testing of conductive composite materials (interconnect materials, one interconnect film)

[0114] 1.1 SEM Testing

[0115] The cross-section and surface of the interconnected thin film were observed using scanning electron microscopy (SEM) to analyze the distribution of metal nanoparticles in the polymer matrix. Figure 5 Cross-sectional view of interconnect thin film and Figure 6 The surface diagram shows that the metal nanoparticles are uniformly distributed in the polymer matrix, forming a complete and dense conductive pathway, thereby achieving high conductivity and stretchability of the film.

[0116] 1.2 Conductivity Test

[0117] Five samples of each of the interconnect films from Examples 1 to 4 were taken and tested using a KEITHLEY DMM6500 digital multimeter. The testing method involved coating both sides of a 5 mm x 5 mm interconnect film with liquid metal to eliminate contact resistance. A copper wire from the multimeter, used for resistance measurement, was connected to the liquid metal. First, the total resistance of the copper wire and the film was measured. Then, two copper wires were placed on the same liquid metal surface, and their resistances were measured. The difference between the two measurements yielded the sheet resistance of the film. The measured sheet resistances were plotted as follows: Figure 7 As shown, Figure 7 The vertical axis represents resistance (Ω), which is equivalent to sheet resistance (Ω / sq). It can be seen that as the content of metal nanoparticles gradually increases, the resistance gradually decreases, and the resistance stability of the samples in each embodiment improves. The sheet resistance of the conductive film in Example 1 can reach 0.01 Ω / sq.

[0118] 1.3 Test of the effect of tensile cycling on electrical conductivity

[0119] The interconnect films from Examples 1 to 4 were subjected to cyclic stretching and recovery, with a uniform stretching deformation rate of 30%. A stretching and recovery cycle was performed every 15 seconds, and the sheet resistance of the interconnect films was continuously observed. The results are as follows: Figure 8 As shown, Figure 8 The vertical axis represents resistance (Ω), which is equivalent to sheet resistance (Ω / sq). It can be seen that in each stretching recovery cycle, the resistance of Example 4 changes the most, while the resistance of Example 1 remains very stable. With cyclic stretching, the resistance of Example 4 gradually increases, and Example 3 also increases slightly, while Examples 1 and 2 remain very stable. The inventors also tested samples with a metal particle mass percentage of 85%. Although the conductivity was further improved, the overall stretchability decreased due to the low content of elastic polymer. Cycles with 30% stretch deformation could still be tested, but those with 60% stretch deformation were prone to breakage.

[0120] Therefore, increasing the mass percentage of metal nanoparticles within a certain range is beneficial for reducing resistance, improving conductivity, reducing energy loss during current transmission, significantly improving device transmission efficiency, and maintaining tensile properties. It also improves conductivity stability; even with 30% deformation and stretching, conductivity changes very little, enhancing signal transmission stability and integrity, reducing signal delay and distortion, making it suitable for dynamic operating environments in flexible electronics. Furthermore, conductivity changes very little even after prolonged stretching, extending lifespan.

[0121] 1.4 Effect of metal particle size on electrical conductivity

[0122] Several samples of the interconnect films from Examples 1 and 5 were taken to test the sheet resistance, and the statistical results are as follows: Figure 9 As shown, Figure 9 The vertical axis represents resistance (Ω), which is equivalent to sheet resistance (Ω / sq). It can be seen that the resistances of both embodiments are very small and very close. This demonstrates that as long as the above preparation method is followed, even with differences in the particle size of the metal particles, the final conductive composite material (interconnect film) exhibits high and very similar conductivity, indicating the wide applicability of the preparation method.

[0123] 1.5 Effect of surface treatment modification of metal particles on electrical conductivity

[0124] After cutting the interconnect films of Example 1 and Comparative Example 1, several samples were taken from each sample to test the sheet resistance. The statistical results are as follows: Figure 10 As shown, Figure 10 The vertical axis represents resistance (Ω), which is equivalent to sheet resistance (Ω / sq). It can be seen that in Comparative Example 1, no surface treatment was applied to the metal particles. Even samples cut from the same interconnect film exhibit highly uneven resistance distributions, with some as low as 0.01 Ω / sq and others as high as 3.4 Ω / sq. Such interconnect films, when used for interconnecting flexible and rigid devices, suffer from uneven internal resistance distribution, which significantly impacts the stability and fidelity of signal transmission, easily leading to distortion. In contrast, samples cut from the same interconnect film in Example 1 show very low and closely spaced resistances, demonstrating excellent resistance uniformity.

[0125] 1.6 Effect of Annealing on Electrical Conductivity

[0126] Three samples each of the interconnect film after annealing in Example 1 and the interconnect film before annealing (self-assembled material, i.e., Comparative Example 2) were taken to test the sheet resistance. The statistical results are as follows: Figure 11 As shown, Figure 11 The vertical axis represents resistance (Ω), which is the sheet resistance (Ω / sq). As can be seen from the figure, annealing has a significant impact on the conductivity of the interconnect film; after annealing, the conductivity can reach 10 times that before annealing. 7 Annealing can significantly improve the conductivity of interconnect films.

[0127] 2. Relevant tests for interconnecting connectors (hot-pressed two conductive films)

[0128] 2.1 Conductivity Test

[0129] Since the interconnect connectors are already connected to rigid wires, unlike the method used to test the sheet resistance of the interconnect films described above, this test directly measures the overall resistance of the interconnect connector with the rigid wires, rather than the sheet resistance, to better suit practical applications. Specifically, two test electrodes are connected to both ends of the interconnect connector. One electrode is connected to the area where the longer interconnect film extends beyond the connector's length, and the other electrode is connected to the rigid wire extending from the interconnect connector. The resistance between these two points is then measured. Five samples of each of the interconnect connectors from Examples 1 to 4 are taken, and their respective resistances are measured. The statistical graph is shown below. Figure 12 As shown, it can be seen that as the content of metal nanoparticles gradually increases, the resistance of the interconnect gradually decreases, and the resistance stability of the samples in each embodiment improves. The resistance of the interconnect in Example 1 can reach 0.1 Ω.

[0130] 2.2 Test of the effect of tensile cycling on electrical conductivity

[0131] The interconnects from Examples 1 to 4 were subjected to cyclic tensile recovery, with a uniform tensile deformation rate of 30%. The tensile direction was parallel to the bonding surface of the two layers. A tensile recovery cycle was performed every 15 seconds, and the resistance of the interconnects was continuously observed. The results are as follows: Figure 13 As shown, it can be seen that the resistance of Example 4 changes the most during each stretching recovery cycle, while the resistance of Example 1 remains very stable. With repeated stretching, the resistance of Example 4 gradually increases, the resistance of Example 3 also increases slightly, while the resistances of Examples 1 and 2 remain very stable.

[0132] Therefore, increasing the mass percentage of metal nanoparticles within a certain range is beneficial for reducing the resistance of the final interconnect, improving conductivity, reducing energy loss during current transmission, and significantly improving device transmission efficiency. It also improves conductivity stability; even with 30% stretching, the conductivity changes very little, enhancing signal transmission stability and integrity, reducing signal delay and distortion, making it suitable for dynamic operating environments in flexible electronics. Furthermore, the conductivity remains minimal even after 600 stretching cycles, indicating a long service life.

[0133] 2.3 Comparison of bonding strength between interconnect connectors and commercial interconnect materials

[0134] Several samples of the interconnect connectors from Example 1 and the commercial interconnect materials from Comparative Examples 3-6 were taken for bonding force testing between the flexible sensor and the rigid wire. The specific steps were as follows: The flexible sensor and the rigid wire were connected using various commercial interconnect materials, such as anisotropic conductive adhesive. First, the anisotropic conductive adhesive was applied to the flexible substrate of the flexible sensor, and then the wire was pressed onto it. A universal mechanical strength tester was used for tensile testing, with one end clamped to the flexible sensor and the other end clamped to the rigid wire. The maximum bonding strength was measured, and the statistical results were recorded. Figure 14 middle, Figure 14 As can be seen from the embodiments of this application, the interconnect connectors obtained are significantly superior to existing commercial interconnect materials, with a bonding force that can reach six times or more. This can improve the stability and reliability of the connection between flexible devices and rigid devices, and they are not easy to fall off after long-term use.

[0135] 2.4 Physical diagram of the interconnecting connector

[0136] Figure 15 This is a side optical photograph of the interconnect connector connecting the rigid wire in Example 1. It can be seen that after hot pressing, the two interconnect films are tightly bonded together, and the rigid wire is pressed between the two layers, forming a tight bond.

[0137] Figure 16 This is a physical image showing how interconnecting connectors connect flexible sensors and rigid wires, demonstrating how the connectors firmly bond the two together.

[0138] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An interconnect connector, characterized in that: It includes a first conductive film and a second conductive film stacked together, wherein the materials of the first conductive film and the second conductive film include conductive composite materials; The interconnect connector is strip-shaped, with one end connected to a rigid wire and the other end connected to a flexible device. The connection method between the rigid wire and the interconnect connector includes the following steps: One end of the rigid wire is connected between the first conductive film and the second conductive film, and then subjected to hot pressing. The method for preparing the conductive composite material includes the following steps: Modified metal particles are obtained by hydrophobic modification of metal particles. The modified metal particles were dispersed in an elastic polymer solution, and the solvent was evaporated to obtain a self-assembled material. The self-assembled material is annealed to obtain a conductive composite material. The hydrophobic modification agent includes thiols; the elastic polymer includes at least one of styrene-ethylene-butene-styrene block copolymer, polydimethylsiloxane, and polyimide; the evaporation treatment includes any one of natural evaporation, vacuum evaporation, and heated evaporation. The annealing temperature is 100℃~200℃.

2. The interconnecting connector according to claim 1, characterized in that: The metal particles include at least one of silver, gold, and copper; And / or, the Dv50 particle size of the metal particles is 0.01 to 1 μm.

3. The interconnecting connector according to claim 2, characterized in that: The thiols include at least one of propanethiol, octanethiol, and dodecylthiol; And / or, the mass ratio of the modifier to the metal particles is (2-3):

1.

4. The interconnecting connector according to any one of claims 1 to 3, characterized in that: The mass ratio of the elastic polymer to the modified metal particles is (2-3):(7-8); And / or, the solvent includes at least one of toluene, ethanol, and n-hexane; And / or, dispersing the modified metal particles in an elastic polymer solution includes the following steps: The modified metal particles are dispersed in a dispersion to obtain a slurry; The slurry and the elastic polymer solution are mixed.

5. The interconnecting connector according to any one of claims 1 to 3, characterized in that: The annealing process takes 20 to 60 minutes.

6. The interconnecting connector according to claim 1, characterized in that: The temperature of the hot pressing treatment is 200–400°C; And / or, the hot pressing treatment time is 0.5 to 6 minutes; And / or, the pressure of the hot pressing treatment is 100 to 300 kPa.

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