Conductive material and method for producing a conductive material

Abstract

The present application relates to a kind of conductive material and the preparation method of conductive material, and the conductive material includes conductive foam and the conductive layer being arranged in the foam two sides, the conductive material also includes two pieces of conductive adhesive layer, one piece of the conductive adhesive layer is bonded between the side of the conductive foam and one piece of the conductive layer, another piece of the conductive adhesive layer is bonded between the other side of the conductive foam and another piece of the conductive layer.The present application uses conductive foam to replace the foam in the related art, forms continuous conductive path between two pieces of conductive layer, and can reduce vertical resistance.In addition, by the conductive adhesive layer bonding conductive foam and conductive layer, reduce the risk of relative slip between conductive layer and conductive foam, ensure the support effect of conductive foam to conductive layer, so as to ensure the long-term stability and reliability of conductive path, and ensure good electromagnetic shielding performance.

Description

Technical Field

[0001] This invention relates to the field of conductive materials technology, and in particular to a conductive material and a method for preparing the conductive material. Background Technology

[0002] With the rapid development of 5G communication, mobile terminals, wearable devices, and aerospace electronic systems towards higher frequencies, greater integration, and miniaturization, electromagnetic interference problems are becoming increasingly serious. Conductive foam, as a conductive material, combines elasticity, conductivity, and electromagnetic shielding performance. As an important type of composite functional material, it is widely used in structural gaps of electronic devices, around connectors, and in grounding areas of shielding covers to achieve electromagnetic sealing and reliable grounding.

[0003] Conductive materials in related technologies typically consist of a conductive layer coated on the surface of foam, which then conducts electricity between two external devices, forming a conductive path. However, such conductive materials have a relatively high vertical resistance, leaving room for improvement. Summary of the Invention

[0004] In view of the above problems, embodiments of the present invention provide a conductive material and a method for preparing the conductive material, which overcomes or at least partially solves the above problems.

[0005] According to one aspect of the present invention, a conductive material is provided, comprising: a conductive foam and conductive layers disposed on both sides of the foam, the conductive material further comprising two conductive adhesive layers, wherein one of the conductive adhesive layers is bonded between one side of the conductive foam and one of the conductive layers, and wherein the other conductive adhesive layer is bonded between the other side of the conductive foam and the other conductive layer.

[0006] In one alternative embodiment, the conductive foam comprises an open-cell foam and silver nanowires disposed within the open-cell foam.

[0007] In one alternative embodiment, the conductive adhesive layer comprises: 30 wt% to 35 wt% epoxy resin; 60 wt% to 65 wt% silver powder; 2 wt% coupling agent; and 3 wt% curing agent diethylenetriamine.

[0008] In one alternative embodiment, the conductive layer is a nickel-plated conductive cloth.

[0009] In an alternative embodiment, the conductive material further includes an adhesive layer bonded to one side of the conductive layer facing away from the conductive foam.

[0010] According to one aspect of the present invention, a method for preparing a conductive material is provided, comprising: preparing conductive foam, including: preparing a dispersion of silver nanowires; immersing a cleaned and dried open-pore foam in the dispersion of silver nanowires; drying the open-pore foam immersed in the dispersion of silver nanowires to obtain conductive foam; preparing conductive adhesive; distributing the conductive adhesive on one side of two conductive layers to form conductive adhesive layers on the conductive layers; bonding the conductive adhesive layers to both sides of the conductive foam and then heating and curing to form conductive material on both sides of the conductive foam bonded to the conductive layers through the conductive adhesive layers.

[0011] In one alternative embodiment, the method for preparing the conductive adhesive comprises: mixing 30 wt% to 35 wt% of epoxy resin, 60 wt% to 65 wt% of silver powder, 2 wt% of coupling agent and 3 wt% of curing agent diethylenetriamine to obtain the conductive adhesive.

[0012] In one alternative embodiment, the method for preparing the silver nanowire dispersion comprises: dispersing silver nanowires in isopropanol, adding 0.5 wt.% sodium carboxymethyl cellulose as a dispersant, and preparing the silver nanowire dispersion with a concentration of 2 mg / mL to 4 mg / mL, wherein the length of the silver nanowires is between 20±5 μm and 30±5 μm, and the diameter of the silver nanowires is between 20±5 nm and 30±5 nm.

[0013] In one optional method, the method of immersing the cleaned and dried open-pore foam in the silver nanowire dispersion and drying the open-pore foam immersed in the silver nanowire dispersion to obtain conductive foam includes: immersing the cleaned and dried open-pore foam in the silver nanowire dispersion to obtain a first substance; placing the first substance in a vacuum drying oven, evacuating it to a preset value, maintaining it for a preset time, and removing the open-pore foam immersed in the silver nanowire dispersion to obtain a second substance; Remove excess liquid from the second substance and dry it to obtain the conductive foam.

[0014] According to one aspect of the present invention, a conductive material is provided, which is prepared using the method for preparing the conductive material.

[0015] The beneficial effects of this invention include providing a conductive material comprising: conductive foam and conductive layers disposed on both sides of the foam; the conductive material further comprising two conductive adhesive layers, wherein one conductive adhesive layer is bonded between one side of the conductive foam and one of the conductive layers, and the other conductive adhesive layer is bonded between the other side of the conductive foam and the other conductive layer. This invention uses conductive foam instead of the foam in related technologies, forming a continuous conductive path between the two conductive layers, which can reduce vertical resistance. Furthermore, by bonding the conductive foam and conductive layers with conductive adhesive layers, the risk of relative slippage between the conductive layers and the conductive foam is reduced, ensuring the supporting effect of the conductive foam on the conductive layers, thereby ensuring the long-term stability and reliability of the conductive path, and ensuring good electromagnetic shielding performance.

[0016] Furthermore, additional aspects and advantages of the invention will be described, shown, or illustrated in part by way of practice in the following description. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a schematic diagram of the conductive material provided in an embodiment of the present invention.

[0019] Figure 2 This is an exploded view of the conductive material provided in an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of a process for preparing conductive materials according to an embodiment of the present invention.

[0021] illustrate: 10. Conductive materials; 1. Conductive foam; 2. Conductive layer; 3. Conductive adhesive layer; 4. Adhesive layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] In the process of implementing the embodiments of this invention, the applicant discovered that the conductive material 10 in related technologies is usually a conductive layer 2 wrapped around the surface of foam, relying on the conductive layer 2 to conduct two external devices and form a conductive path. This structure has the following problems: ① High internal resistance: The foam in related technologies is an insulator, and conductivity depends entirely on the surface conductive layer 2, resulting in the inability to form an effective conductive network inside the foam. When the foam is compressed, the foam does not participate in conductivity, and the current only flows along the surface of the conductive layer 2. The path is long and the resistance is high, especially in the vertical direction (perpendicular to the contact surface between the conductive layer 2 and the external device). Due to the lack of internal conductive support, the vertical resistance remains high, making it difficult to meet the requirements of low grounding resistance (<10mΩ), thus limiting its application in high-precision and high-reliability conductive scenarios. ② Unstable conductive path: The conductive layer 2 only wraps around the outside of the open-cell foam. After repeated compression or shearing, the conductive layer 2 and the foam are prone to relative slippage. The supporting effect of the foam on the conductive layer 2 is weakened, resulting in increased contact resistance and decreased electromagnetic shielding performance.

[0024] This invention provides a conductive material 10, comprising a conductive foam 1 and conductive layers 2 disposed on both sides of the foam. The conductive material 10 also includes two conductive adhesive layers 3, one of which is bonded between one side of the conductive foam 1 and one of the conductive layers 2, and the other is bonded between the other side of the conductive foam 1 and the other conductive layer 2. This invention uses conductive foam 1 instead of the foam in related technologies, forming a continuous conductive path between the two conductive layers 2, which reduces vertical resistance (the resistance encountered when current flows perpendicular to the surface of the conductive layer 2 (i.e., the thickness direction of the conductive material 10)). Furthermore, by bonding the conductive foam 1 and the conductive layers 2 with the conductive adhesive layers 3, the risk of relative slippage between the conductive layers 2 and the conductive foam 1 is reduced, ensuring the supporting effect of the conductive foam 1 on the conductive layer 2, thereby ensuring the long-term stability and reliability of the conductive path and ensuring good electromagnetic shielding performance.

[0025] It is worth noting that, in some embodiments, the conductive foam 1 includes open-cell foam and silver nanowires disposed within the open-cell foam. The silver nanowires can be uniformly distributed in a three-dimensional network structure inside the open-cell foam to achieve the conductive function of the conductive foam 1.

[0026] In some embodiments, the length of the silver nanowire is between 20±5 μm and 30±5 μm, and the diameter of the silver nanowire is between 20±5 nm and 30±5 nm.

[0027] In some implementations, the pore size of the open-cell foam is between 80±10 μm and 120±10 μm, the thickness of the open-cell foam can be 2.0±0.1 mm, and the density of the open-cell foam can be 25±2 kg / m³.

[0028] In some implementations, the perforated foam is made of polyurethane, while in others it can be made of silicone.

[0029] It is worth noting that, in some embodiments, the conductive adhesive layer 3 comprises 30 wt% to 35 wt% epoxy resin; The conductive adhesive layer 3 possesses both excellent adhesion and conductivity properties, consisting of 60 wt% to 65 wt% silver powder, 2 wt% coupling agent, and 3 wt% curing agent diethylenetriamine.

[0030] The epoxy resin can be E-51 type epoxy resin with an epoxy value of 0.48 to 0.54 mol / 100g, or other types, such as E-44 type with an epoxy value of 0.41 to 0.47 mol / 100g.

[0031] The silver powder can be in flake form, with a particle size between 5±0.5 μm and 8±0.5 μm.

[0032] The coupling agent can be KH-560 type silane coupling agent, or it can be KH-550 type silane coupling agent or KH-570 type silane coupling agent to enhance the interfacial bonding strength between silver powder and epoxy resin.

[0033] In some embodiments, at room temperature (23±2℃), the volume resistivity of the conductive adhesive layer 3 is less than 5×10⁻⁶. -4 The volume resistivity of conductive adhesive layer 3 can be measured using a four-probe resistance meter (Ω·cm).

[0034] It is worth noting that in some embodiments, the conductive layer 2 is a nickel-plated conductive cloth. Alternatively, the conductive layer 2 can also be a copper-plated conductive cloth, a tin-plated conductive cloth, or a conductive coated fabric.

[0035] In some embodiments, the surface resistivity of the conductive layer 2 is less than or equal to 0.05 Ω / sq.

[0036] In some implementations, the thickness of the conductive layer 2 can be 0.12 ± 0.02 mm.

[0037] It is worth noting that in some embodiments, the conductive material 10 further includes an adhesive layer 4, which is bonded to one side of the conductive layer 2 facing away from the conductive foam 1. The adhesive layer 4 facilitates the fixation of the conductive material 10 to the external device. It is understood that the adhesive layer 4 does not affect the conductivity between the conductive material 10 and the external device through the conductive layer 2. The adhesive layer 4 may be conductive itself, for example, using acrylic conductive adhesive or silicone-based voltage-sensitive adhesive; or, the area of ​​the bonding surface between the adhesive layer 4 and the conductive layer 2 may be smaller than the area of ​​the conductive layer 2, thereby ensuring that the conductive layer 2 is partially exposed, allowing the conductive layer 2 to contact and conduct with the external device through its exposed portion.

[0038] According to another aspect of the present invention, a method for preparing a conductive material is provided; please refer to [link to relevant documentation]. Figure 3 ,include: Step S10, preparing conductive foam, includes preparing a silver nanowire dispersion, immersing the cleaned and dried open-pore foam in the silver nanowire dispersion, and drying the open-pore foam immersed in the silver nanowire dispersion to obtain conductive foam.

[0039] In some embodiments, the concentration of the silver nanowire dispersion is from 2 mg / mL to 4 mg / mL.

[0040] In some embodiments, a method for preparing a silver nanowire dispersion includes: dispersing silver nanowires in isopropanol, adding 0.5 wt.% sodium carboxymethyl cellulose as a dispersant, and preparing the silver nanowire dispersion with a concentration of 2 mg / mL to 4 mg / mL, wherein the length of the silver nanowires is between 20±5 μm and 30±5 μm, and the diameter of the silver nanowires is between 20±5 nm and 30±5 nm.

[0041] In some implementations, the silver nanowires are dispersed in isopropanol, and 0.5 wt.% sodium carboxymethyl cellulose is added as a dispersant to prepare a silver nanowire dispersion with a concentration of 2 mg / mL to 4 mg / mL. Specifically, the silver nanowires are ultrasonically dispersed in isopropanol (anhydrous grade, purity ≥99.7%), and 0.5 wt.% sodium carboxymethyl cellulose is added as a dispersant to obtain the silver nanowire dispersion. The ultrasonic dispersion can be performed using a probe-type ultrasonic instrument with an amplitude of 30%, a pulse on / off time of 2 seconds, and a total effective ultrasonic dispersion time of 20 min.

[0042] In some embodiments, the method of immersing the cleaned and dried open-pore foam in the silver nanowire dispersion and drying the immersed open-pore foam to obtain conductive foam includes: immersing the cleaned and dried open-pore foam in the silver nanowire dispersion to obtain a first substance; placing the first substance in a vacuum drying oven, evacuating it to a preset value (e.g., -0.09 MPa), and maintaining it for a preset time (e.g., 30 min) to ensure that the open-pore foam is completely immersed in the silver nanowire dispersion and that the silver nanowires fully penetrate the internal pore walls of the open-pore foam; removing the immersed open-pore foam to obtain a second substance; removing excess liquid from the second substance and drying it to obtain the conductive foam.

[0043] One method for cleaning and drying open-pore foam is to sequentially use deionized water and anhydrous ethanol for ultrasonic cleaning (for example, using an ultrasonic cleaner with a frequency of 40 kHz, a power of 150 W, and a room temperature of 23±5℃)) for 15 min, and then dry it in a vacuum drying oven at 60 ℃ for 2 h to obtain cleaned and dried open-pore foam.

[0044] In some implementations, the pore size of the open-cell foam is between 80±10 μm and 120±10 μm, the thickness of the open-cell foam can be 2.0±0.1 mm, and the density of the open-cell foam can be 25±2 kg / m³.

[0045] In some embodiments, the excess liquid in the second substance is removed and dried to obtain the conductive foam by: using a rubber roller to squeeze out the excess liquid (silver nanowire dispersion), and drying in a 60 ℃ forced-air drying oven for 2 h to obtain the conductive foam.

[0046] In some embodiments, after removing excess liquid from the second substance and drying it, a third substance is obtained. The third substance is then repeatedly impregnated in the silver nanowire dispersion, and the third substance impregnated in the silver nanowire dispersion is dried to finally obtain conductive foam.

[0047] Step S20: Prepare conductive adhesive.

[0048] In some embodiments, the method for preparing the conductive adhesive includes: mixing 30 wt% to 35 wt% of epoxy resin, 60 wt% to 65 wt% of silver powder, 2 wt% of coupling agent, and 3 wt% of curing agent diethylenetriamine to obtain the conductive adhesive. The prepared conductive adhesive possesses both excellent adhesion and conductivity properties.

[0049] In some implementations, the mixture of 30 wt% to 35 wt% epoxy resin, 60 wt% to 65 wt% silver powder, 2 wt% coupling agent and 3 wt% curing agent diethylenetriamine can be achieved by first homogenizing with a homogenizer at a speed of 1500 rpm to 2000 rpm for 10 min to 15 min, and then grinding with a three-roll mill.

[0050] The roller spacing of the three-roll mill can be 50 μm for the first stage (feed) and 20 μm for the second stage (discharge).

[0051] The epoxy resin can be E-51 type epoxy resin with an epoxy value of 0.48 to 0.54 mol / 100g, or other types, such as E-44 type with an epoxy value of 0.41 to 0.47 mol / 100g.

[0052] The silver powder can be in flake form, with a particle size between 5±0.5 μm and 8±0.5 μm.

[0053] The coupling agent can be KH-560 type silane coupling agent, or it can be KH-550 type silane coupling agent or KH-570 type silane coupling agent to enhance the interfacial bonding strength between silver powder and epoxy resin.

[0054] In some embodiments, at room temperature (23±2℃), the volume resistivity of the conductive adhesive is controlled to be less than 5×10⁻⁶. -4 The volume resistivity of the conductive adhesive can be measured using a four-probe resistance meter. The ideal volume resistivity is less than 5 × 10⁻⁶ Ω·cm. -4 The method of Ω·cm can be achieved by adjusting the roller spacing and homogenization time of a three-roll mill to ensure that the silver powder is evenly dispersed and fully wetted in the epoxy resin.

[0055] Step S30: The conductive adhesive is applied to one side of each of the two conductive layers to form a conductive adhesive layer on the conductive layer. The conductive adhesive layer is then bonded to both sides of the conductive foam and heated to cure, so that the conductive foam is bonded to the conductive material of the conductive layer through the conductive adhesive layer on both sides.

[0056] In some embodiments, a specific implementation of step S30 is as follows: Take two conductive layers and coat one side of each conductive layer with the conductive adhesive, for example, by screen printing; attach the side coated with the conductive adhesive to both sides of the conductive foam, and hot-press and cure at 80 ℃ and 0.3 MPa for 2 h. For example, use a flatbed hot press to achieve hot pressing. The upper and lower plates of the flatbed hot press are preheated to 80 ℃, the mold is closed and pressure is applied to 0.3 MPa, and then the timer is started for 2 h, forming conductive materials on both sides of the conductive foam bonded to the conductive layer through the conductive adhesive layer.

[0057] It is worth noting that in some embodiments, when coating the conductive adhesive on the conductive layer, the coating thickness is between 30±5 μm and 50±5 μm.

[0058] It is worth noting that in some embodiments, the conductive layer is a nickel-plated conductive cloth. Alternatively, the conductive layer may also be a copper-plated conductive cloth, a tin-plated conductive cloth, or a conductive coated fabric.

[0059] In some embodiments, the surface resistivity of the conductive layer is less than or equal to 0.05 Ω / sq.

[0060] In some implementations, the thickness of the conductive layer can be 0.12 ± 0.02 mm.

[0061] The conductive material prepared by the above method, due to the conductivity of the conductive foam, can form a continuous conductive path between two conductive layers, reducing vertical resistance (the resistance encountered when current flows perpendicular to the surface of the conductive layer (i.e., the thickness direction of the conductive material)). Furthermore, by bonding the conductive foam and conductive layers with a conductive adhesive layer, the risk of relative slippage between the conductive layers and the conductive foam is reduced, ensuring the supporting effect of the conductive foam on the conductive layer. This ensures the long-term stability and reliability of the conductive path, as well as good electromagnetic shielding performance.

[0062] This invention also provides a conductive material, which is prepared using the method described in the above embodiments. The prepared conductive material can be referred to... Figure 1 The conductive material 10 shown.

[0063] To facilitate readers' understanding of the inventive concept of the embodiments of the present invention, the technical effects of using the embodiments of the present invention are demonstrated below.

[0064] Example 1 <Preparation of Conductive Foam> Preparation of silver nanowire dispersion: Silver nanowires with a length of 30±5 μm and a diameter of 30±5 nm were ultrasonically dispersed (using a probe-type ultrasonic instrument with an amplitude of 30%, a pulse on for 2 seconds and a pulse off for 1 second, and the total effective time of ultrasonic dispersion can be 20 min) in isopropanol (anhydrous grade, purity ≥99.7%), and 0.5 wt.% sodium carboxymethyl cellulose was added as a dispersant to prepare a silver nanowire dispersion with a concentration of 2 mg / mL for later use.

[0065] Cleaning and drying of open-cell foam: Select open-cell foam (polyurethane) with a pore size of 120±10 μm, a thickness of 2.0±0.1 mm, and a density of 25±2 kg / m³. Clean it with deionized water and anhydrous ethanol in sequence using an ultrasonic cleaner (frequency 40 kHz, power 150 W, room temperature (23±5℃)) for 15 min. Then dry it in a vacuum drying oven at 60 ℃ for 2 h to obtain cleaned and dried open-cell foam.

[0066] Impregnated with silver nanowires: The cleaned and dried open-pore foam is completely immersed in the above silver nanowire dispersion, and then placed in a vacuum drying oven. The vacuum is drawn to -0.09 MPa and maintained for 30 min to allow the silver nanowires to fully enter the internal pore walls of the open-pore foam. After removal, excess liquid is squeezed out with a rubber roller and dried in a 60 ℃ forced-air drying oven for 2 h.

[0067] Repeat the above steps of impregnating silver nanowires once to finally obtain conductive foam.

[0068] <Preparation of Conductive Adhesive> Using 30 wt% epoxy resin (E-51) as the matrix, 65 wt% flake silver powder (particle size 5±0.5 μm) was added, along with 2 wt% coupling agent KH-560 and 3 wt% curing agent diethylenetriamine. The mixture was first homogenized at 1500 rpm for 10 min using a homogenizer, and then uniformly dispersed using a three-roll mill to obtain a conductive adhesive. The volume resistivity of the conductive adhesive was controlled to be less than 5 × 10⁻⁶ at room temperature (23±2℃). -4 The volume resistivity of conductive adhesive can be measured using a four-probe resistance meter (Ω·cm).

[0069] <Forming conductive materials> Two nickel-plated conductive layers (surface resistivity less than or equal to 0.05 Ω / sq, thickness 0.12±0.02 mm) were taken, and the above-mentioned conductive adhesive was screen-printed onto one side of each of the two nickel-plated conductive fabrics, with a coating thickness of 30±5 μm. The side coated with the conductive adhesive was then attached to both sides of the above-mentioned conductive foam, and hot-pressed and cured at 80 ℃ and 0.3 MPa for 2 h, forming a conductive foam on both sides that were bonded to the conductive material of the nickel-plated conductive fabric through the conductive adhesive layer.

[0070] Performance Testing The surface resistance of conductive materials was tested using a four-probe resistance tester. The vertical resistance of conductive materials was tested using a digital multimeter and planar electrodes, with a 1kg weight applied during the test. The shielding performance of conductive materials in the X-band (8.2~12.4GHz) was tested using Agilent's vector network analyzer to obtain the shielding effectiveness; The test results for surface resistance, vertical resistance, and shielding effectiveness are shown in Table 1.

[0071] Example 2 <Preparation of Conductive Foam> Preparation of silver nanowire dispersion: Silver nanowires with a length of 20±5 μm and a diameter of 20±5 nm were ultrasonically dispersed (using a probe-type ultrasonic instrument with an amplitude of 30%, a pulse on for 2 seconds and off for 1 second, and a total effective ultrasonic dispersion time of 20 min) in isopropanol (anhydrous grade, purity ≥99.7%), and 0.5 wt.% sodium carboxymethyl cellulose was added as a dispersant to prepare a silver nanowire dispersion with a concentration of 4 mg / mL for later use.

[0072] Cleaning and drying of open-cell foam: Select open-cell foam (polyurethane) with a pore size of 80±10 μm, a thickness of 2.0±0.1 mm, and a density of 25±2 kg / m³. Clean it with deionized water and anhydrous ethanol in sequence using an ultrasonic cleaner (frequency 40 kHz, power 150 W, room temperature (23±5℃)) for 15 min. Then dry it in a vacuum drying oven at 60 ℃ for 2 h to obtain cleaned and dried open-cell foam.

[0073] Impregnated with silver nanowires: The cleaned and dried open-pore foam is completely immersed in the above silver nanowire dispersion, and then placed in a vacuum drying oven. The vacuum is drawn to -0.09 MPa and maintained for 30 min to allow the silver nanowires to fully enter the internal pore walls of the open-pore foam. After removal, excess liquid is squeezed out with a rubber roller and dried in a 60 ℃ forced-air drying oven for 2 h.

[0074] Repeat the above steps of impregnating silver nanowires once to finally obtain conductive foam.

[0075] <Preparation of Conductive Adhesive> Using 35 wt% epoxy resin (E-44) as the matrix, 60 wt% flake silver powder (particle size 8±0.5 μm) was added, along with 2 wt% coupling agent KH-560 and 3 wt% curing agent diethylenetriamine. The mixture was first homogenized at 2000 rpm for 15 min using a homogenizer, and then uniformly dispersed using a three-roll mill to obtain a conductive adhesive. The volume resistivity of the conductive adhesive was controlled to be less than 6 × 10⁻⁶ at room temperature (23±2℃). -4 The volume resistivity of conductive adhesive can be measured using a four-probe resistance meter (Ω·cm).

[0076] <Forming conductive materials> Two nickel-plated conductive layers (surface resistivity less than or equal to 0.05 Ω / sq, thickness 0.12±0.02 mm) were taken, and the above-mentioned conductive adhesive was screen-printed onto one side of each of the two nickel-plated conductive fabrics, with a coating thickness of 50±5 μm. The side coated with the conductive adhesive was then attached to both sides of the above-mentioned conductive foam, and hot-pressed and cured at 80 ℃ and 0.3 MPa for 2 h, forming a conductive foam on both sides that were bonded to the conductive material of the nickel-plated conductive fabric through the conductive adhesive layer.

[0077] Performance Testing Same as Example 1.

[0078] Comparative Example 1 Open-pore foam (polyurethane) with a pore size of 80±10 μm, a thickness of 2.0±0.1 mm, and a density of 25±2 kg / m³ was selected. It was ultrasonically cleaned with deionized water and anhydrous ethanol in sequence (using an ultrasonic cleaner, frequency 40 kHz, power 150 W, room temperature (23±5℃)) for 15 min, and then dried in a vacuum drying oven at 60 ℃ for 2 h to obtain the cleaned and dried open-pore foam. Two pieces of nickel-plated conductive cloth (surface resistivity less than or equal to 0.05 Ω / sq, thickness 0.12±0.02 mm) were taken, and conductive hot melt adhesive was applied to one side of each piece of nickel-plated conductive cloth. The adhesive-coated surfaces were then attached to both sides of the perforated foam and hot-pressed and cured at 80℃ and 0.3 MPa pressure for 2 h to obtain conductive material. The surface resistance, vertical resistance and shielding effectiveness of the conductive material were tested according to Example 1, and the results are shown in Table 1.

[0079] Table 1. Properties of conductive materials

[0080] As shown in Table 1, the conductive materials provided in Examples 1 and 2 of this invention have relatively low vertical resistances, at 0.03 Ω and 0.04 Ω respectively, significantly better than the 0.09 Ω of Comparative Example 1. This indicates that the conductive materials provided in these embodiments of the invention form an excellent three-dimensional conductive network through conductive foam, and achieve good interfacial bonding stability by bonding the conductive layer and conductive foam with conductive adhesive layer, maintaining a low-resistance path even under long-term compression deformation and temperature cycling conditions. Furthermore, the surface resistance of the conductive materials provided in Examples 1 and 2 of this invention remains consistent with Comparative Example 1, both at 0.04 Ω. Equally important, the shielding effectiveness of the conductive materials provided in Examples 1 and 2 of this invention reaches 85.0 dB and 80.2 dB respectively, significantly higher than the 65.6 dB of Comparative Example 1. The conductive materials provided in these embodiments of the invention can effectively ensure low resistance, high shielding, and long-life electromagnetic sealing functions.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A conductive material, characterized in that, include: The conductive material includes a conductive foam and conductive layers disposed on both sides of the foam. The conductive material also includes two conductive adhesive layers, one of which is bonded between one side of the conductive foam and one of the conductive layers, and the other of which is bonded between the other side of the conductive foam and the other conductive layer.

2. The conductive material according to claim 1, characterized in that, The conductive foam includes open-cell foam and silver nanowires disposed in the open-cell foam.

3. The conductive material according to claim 1, characterized in that, The conductive adhesive layer includes: 30 wt% to 35 wt% epoxy resin; 60 wt% to 65 wt% silver powder; 2 wt% coupling agent; 3 wt% of curing agent diethylenetriamine.

4. The conductive material according to any one of claims 1-3, characterized in that, The conductive layer is a nickel-plated conductive cloth.

5. The conductive material according to any one of claims 1-3, characterized in that, The conductive material further includes an adhesive layer, which is bonded to one side of the conductive layer facing away from the conductive foam.

6. A method for preparing a conductive material, characterized in that, include: The preparation of conductive foam includes: preparing a silver nanowire dispersion, immersing a cleaned and dried open-pore foam in the silver nanowire dispersion, and drying the open-pore foam immersed in the silver nanowire dispersion to obtain conductive foam. Preparation of conductive adhesive; The conductive adhesive is applied to one side of each of the two conductive layers to form a conductive adhesive layer on the conductive layer. The conductive adhesive layer is then bonded to both sides of the conductive foam and heated to cure, so that the conductive foam is bonded to the conductive material of the conductive layer through the conductive adhesive layer on both sides.

7. The method for preparing the conductive material according to claim 6, characterized in that, The method for preparing the conductive adhesive includes: mixing 30 wt% to 35 wt% of epoxy resin, 60 wt% to 65 wt% of silver powder, 2 wt% of coupling agent and 3 wt% of curing agent diethylenetriamine to obtain the conductive adhesive.

8. The method for preparing the conductive material according to claim 6, characterized in that, The method for preparing the silver nanowire dispersion includes: Silver nanowires were dispersed in isopropanol, and 0.5 wt.% sodium carboxymethyl cellulose was added as a dispersant to prepare a silver nanowire dispersion with a concentration of 2 mg / mL to 4 mg / mL. The length of the silver nanowires was between 20±5 μm and 30±5 μm, and the diameter of the silver nanowires was between 20±5 nm and 30±5 nm.

9. The method for preparing the conductive material according to claim 6, characterized in that, The method of immersing the cleaned and dried open-pore foam in the silver nanowire dispersion and drying the impregnated open-pore foam to obtain conductive foam includes: The cleaned and dried perforated foam was immersed in the nano-silver wire dispersion to obtain the first substance; The first substance was placed in a vacuum drying oven, vacuumed to a preset value, and maintained for a preset time. The open-pore foam impregnated with the silver nanowire dispersion was then removed to obtain the second substance. Remove excess liquid from the second substance and dry it to obtain the conductive foam.

10. A conductive material, characterized in that, The conductive material is prepared using the method for preparing conductive materials as described in any one of claims 6-9.

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