Nano silver wire-copper wire gradient distribution electromagnetic shielding film and preparation method

Abstract

The present invention relates to the technical field of electromagnetic shielding film preparation, and discloses a nanosilver wire-copper wire gradient distribution electromagnetic shielding film and a preparation method. A one-dimensional alternating gradient distribution nanosilver wire-copper wire array with controllable component ratios is prepared by a double-slot electrodeposition method and a melting method. The array has a length range of 1μm-100μm and a diameter range of 40-60nm. Using the nanosilver wire array as a shielding material and one of polyvinyl chloride (PVC), polyester film, or glass film as a substrate, the resulting electromagnetic shielding film has an optical transmittance of over 80% at a wavelength of 550nm and an electromagnetic shielding performance of 20-30dB. While overcoming the high cost of silver nanowires and the poor light transmittance of copper nanowires, the present invention achieves the excellent technical effect of simultaneously maintaining excellent light transmittance and electromagnetic shielding performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding film preparation, in particular to a nano silver wire-copper wire gradient distribution electromagnetic shielding film and a preparation method thereof. Background Art

[0002] With the increase in the operating frequency of electronic components and the increase in packaging density, the electromagnetic compatibility problem between electronic components has become increasingly prominent. Therefore, there is an urgent need to introduce electromagnetic interference (EMI) shielding materials to reasonably suppress interference and improve the reliability of equipment. In some application scenarios, in addition to considering the need for electromagnetic interference shielding, the light transmittance characteristics of the shielding film should also be considered. For example, in a system-level three-dimensional package (SiP), the signal interference between chips inside the stacked package should be isolated using a transparent electromagnetic shielding film so as not to affect the subsequent chip mounting and alignment process. In addition, in optical systems in the aerospace field, such as optical windows and electronic displays, transparent electromagnetic shielding films should be used to simultaneously meet the requirements of electromagnetic shielding and optical visibility, so that both signal detection and optical observation functions can be guaranteed.

[0003] Traditional electromagnetic interference shielding composite materials are mostly opaque. Silver nanowire (AgNWs) films are considered the most promising transparent electromagnetic interference shielding material due to their excellent conductivity, high light transmittance, and ease of fabrication. However, the high cost, difficulty in development, and low reserves of AgNWs have limited their further development.

[0004] In comparison, copper nanowires have comparable optoelectronic properties to silver nanowires and an ultra-low cost, but suffer from poor light transmittance (the transmittance of copper nanowires is only 65%). The present invention chemically prepares nanowires containing both copper and silver, overcoming the high cost of silver nanowires and the poor light transmittance of copper nanowires while maintaining excellent light transmittance and electromagnetic shielding properties. Summary of the Invention

[0005] In order to overcome the high cost of silver nanowires and the poor light transmittance of copper nanowires, the present invention provides a gradient-distributed nanosilver wire-copper wire that maintains excellent light transmittance and electromagnetic shielding performance. It is prepared by a double-slot electrodeposition method and a melting method. Its length range is 1μm-100μm, and its diameter range is 40-60nm. The nanosilver wires and nanocopper wires are distributed in an alternating gradient. It is used to prepare an electromagnetic shielding film. The electromagnetic shielding film has an optical transmittance of more than 80% at a wavelength of 550nm and an electromagnetic shielding performance of 20-30dB.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, a method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film comprises the following steps:

[0008] Step 1: Wash the substrate material with deionized water and anhydrous ethanol to remove surface stains, and then perform ultrasonic vibration;

[0009] Step 2: Prepare the gradient-distributed nano silver wires and copper wires into an anhydrous ethanol suspension with a concentration of 0.1-5 mg / mL, and ultrasonically vibrate to uniformly disperse them in the solvent;

[0010] Step 3, vertically fixing the substrate material in Step 1 on the working arm of the pulling machine, moving the substrate at an immersion speed of 40-80 mm / min to immerse it in the suspension in Step 2, when the substrate material is completely immersed in the suspension, standing, and the substrate begins to leave the suspension at a lifting speed of 80-120 mm / min. After completely leaving the solution, it is naturally dried. The immersion process is repeated three times, and then vacuum dried to a constant weight to obtain a nano silver wire-copper wire gradient distribution electromagnetic shielding film;

[0011] Wherein, the base material is one of polyvinyl chloride (PVC), polyester film (PET, CPI, PC, PDMS, PEN, PVA, etc.) or glass film;

[0012] The method for preparing the gradient-distributed nano silver wire-copper wire comprises the following steps:

[0013] Step 1: Prepare a porous anodic aluminum oxide film with a through-pore diameter of 40-60 nm and a pore depth of 100 μm. Vacuum evaporate a gold layer with a thickness of 200-300 nm on the back of the aluminum oxide film by vacuum evaporation. The gold layer serves as a deposition electrode for direct current electrodeposition, which is the cathode of the aluminum oxide film.

[0014] Step 2, prepare a silver electrodeposition solution, the required reagents are: 40g / L silver nitrate (AgNO3), 32g / L boric acid (H3BO3) and 40g / L tartaric acid (DL-C4H6O4);

[0015] Step 3, prepare a copper electrodeposition solution, the required reagents are: 100g / L of copper sulfate pentahydrate (CuSO4·5H2O), 40g / L of copper chloride dihydrate (CuCl2·2H2O) and 32g / L of boric acid (H3BO3);

[0016] Step 4: Using a double-tank electrochemical deposition method, alternately deposit nanosilver wires and copper wires in the nanopores of the aluminum oxide film cathode to obtain a gradient distribution nanosilver wire-copper wire array. The specific steps are as follows:

[0017] Step 4-1: Pour the silver electrodeposition solution into the Ag electrodeposition tank, and let the cathode with the aluminum oxide film precipitate 100-500nm silver nanowires in the Ag electrodeposition tank; wherein, the deposition conditions of the silver nanowires are: deposition voltage, 0.5V at room temperature; deposition current, 1.25mA / cm 2 ; Sedimentation time, 10-50s;

[0018] Step 4-2, taking out the cathode with silver nanowires deposited in the nanopores of the aluminum oxide film in Step 4-1, soaking and cleaning it in deionized water to clean the silver electrodeposition solution;

[0019] Step 4-3: Pour the copper electrodeposition solution into the Cu electrodeposition tank, and let the cathode cleaned in Step 4-2 precipitate 100-500 nm copper nanowires in the Cu electrodeposition tank; wherein the deposition conditions of the copper nanowires are: deposition voltage, 1.2 V, deposition current, 1.75 mA / cm at room temperature. 2 , sedimentation time, 20-100s;

[0020] Step 4-4, taking out the cathode with silver nanowires and copper nanowires deposited in the nanopores of the aluminum oxide film in Step 4-3, soaking and cleaning it in deionized water to clean the copper electrodeposition solution;

[0021] Step 4-5, repeating the preparation process of Step 4-1, Step 4-2, Step 4-3, and Step 4-4 50-200 times, alternately depositing nano silver wires and nano copper wires;

[0022] Step 5: Apply a layer of silver paste on the front surface of the aluminum oxide film on the cathode in Step 4-5 to block the pores of the aluminum oxide film, and then melt-mix and react at 600-650° C. for 2-5 hours under nitrogen protection;

[0023] In step 6, the aluminum oxide film on the cathode in step 5 is immersed in a 2-8% wt NaOH solution, and the aluminum oxide film is corroded and dissolved by chemical dissolution to remove the aluminum oxide film. Then, it is washed by ultrasonic centrifugation with deionized water and anhydrous ethanol multiple times, and vacuum dried to constant weight to prepare nano silver wires-copper wires with a length of 1-100 μm, a diameter of 40-60 nm, and an alternating gradient distribution.

[0024] On the other hand, the present invention provides a nano-silver wire-copper wire gradient distribution electromagnetic shielding film, which uses nano-silver wire-copper wire with a length of 1-100 μm, a diameter of 40-60 nm and an alternating gradient distribution as the shielding material, and one of polyvinyl chloride (PVC), polyester film (PET, CPI, PC, PDMS, PEN, PVA, etc.) or glass film as the base material. Its optical transmittance at a wavelength of 550 nm is above 80%, and its electromagnetic shielding performance is 20-30 dB.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present invention prepares a one-dimensional alternating gradient distribution nano silver wire-copper wire array with controllable component ratio through a double-tank electrodeposition method and a melting method. Using it as the shielding material and PVC (transmittance 84%, thickness 180μm) as the base material, the prepared electromagnetic shielding film has an optical transmittance of 83.11% at a wavelength of 550nm and an electromagnetic shielding performance of 29dB. This overcomes the high cost of silver nanowires and the poor light transmittance of copper nanowires, while achieving the excellent technical effect of maintaining excellent light transmittance and electromagnetic shielding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the gradient distribution structure of nano silver wires and copper wires prepared in Example 4;

[0028] Figure 2 Schematic diagram of the gradient distribution structure of nano silver wire-copper wire prepared in Example 5. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The reagents used in the following examples can all be purchased from conventional manufacturers in the field; the experimental methods used are all conventional experimental methods known to those skilled in the art.

[0031] Example 1:

[0032] The present invention provides a method for preparing gradient-distributed nano silver wire-copper wire, comprising the following steps:

[0033] Step 1: preparing an aluminum oxide film cathode, the specific method is as follows: using a two-step anodization method, in a 0.3 mol / L oxalic acid electrolyte, at a voltage of 40V, to prepare a porous anodized aluminum oxide film with a through-pore diameter of 40-60 nm and a pore depth of 100 μm, and vacuum evaporating a 250 nm thick gold layer on the back of the aluminum oxide film by a vacuum evaporation method, which serves as a deposition electrode for direct current electrodeposition, and is the aluminum oxide film cathode;

[0034] Step 2, preparing a silver electrodeposition solution. The entire process of preparation is completed in a dark room. The specific preparation process is as follows: first, weigh 10 parts by weight of silver nitrate (AgNO3), 8 parts by weight of boric acid (H3BO3) and 10 parts by weight of tartaric acid (DL-C4H6O4), then weigh 250 parts by weight of deionized water and pour it into a beaker with a magnet, and stir it on a magnetic stirrer. Then, add tartaric acid, boric acid, and silver nitrate into the beaker in this order and stir until they are completely dissolved. Finally, use a pH meter to detect the pH value of the solution, use dilute nitric acid solution or ammonia water to adjust the pH value to 3, and prepare the silver electrodeposition solution, which is stored in a brown wide-mouth bottle for standby use;

[0035] Step 3, preparing a copper electrodeposition solution, the specific preparation process is as follows: first, weighing 25 parts by weight of copper sulfate pentahydrate (CuSO4·5H2O), 10 parts by weight of copper chloride dihydrate (CuCl2·2H2O) and 8 parts by weight of boric acid (H3BO3), then weighing 250 parts by weight of deionized water into a beaker with a magnet, and placing it on a magnetic stirrer for stirring, then placing boric acid, copper chloride dihydrate, and copper sulfate pentahydrate into the beaker in order and stirring until completely dissolved, finally using a pH meter to detect the pH value of the solution, and using dilute hydrochloric acid or ammonia water to adjust the acidity and alkalinity of the solution to a pH value of 4, to prepare a copper electrodeposition solution;

[0036] Step 4: Using a double-tank electrochemical deposition method, alternately deposit nanosilver wires and copper wires in the nanopores of the aluminum oxide film cathode to obtain a gradient distribution nanosilver wire-copper wire array. The specific steps are as follows:

[0037] Step 4-1: Pour the silver electrodeposition solution into the Ag electrodeposition tank, and let the cathode with the aluminum oxide film deposit 300nm silver nanowires in the Ag electrodeposition tank; wherein, the deposition conditions of the silver nanowires are: deposition voltage, 0.5V at room temperature; deposition current, 1.25mA / cm 2 ; Sedimentation time, 30s;

[0038] Step 4-2: remove the cathode with silver nanowires deposited in the nanopores of the aluminum oxide membrane in Step 4-1, and soak it in deionized water for 60 seconds to clean the silver electrodeposition solution;

[0039] Step 4-3: Pour the copper electrodeposition solution into the Cu electrodeposition tank, and let the cathode cleaned in Step 4-2 deposit 300nm copper nanowires in the Cu electrodeposition tank; wherein, the deposition conditions of the copper nanowires are: deposition voltage, 1.2V, deposition current, 1.75mA / cm at room temperature. 2 , sedimentation time, 60s;

[0040] Step 4-4, taking out the cathode with silver nanowires and copper nanowires deposited in the nanopores of the aluminum oxide film in Step 4-3, soaking it in deionized water for 60 seconds to clean the copper electrodeposition solution;

[0041] Step 4-5, repeating the preparation process of Step 4-1, Step 4-2, Step 4-3, and Step 4-4 100 times, alternately depositing nano silver wires and nano copper wires;

[0042] Step 5: Apply a layer of silver paste on the front surface of the aluminum oxide film on the cathode in Step 4-5 to block the pores of the aluminum oxide film, and then melt-mix and react at 630° C. for 3 hours under nitrogen protection;

[0043] Step 6: Immerse the aluminum oxide film on the cathode in Step 5 in a 5% wt NaOH solution and use a chemical dissolution method to corrode and dissolve for 20 minutes to remove the aluminum oxide film. Then, wash the aluminum oxide film by multiple ultrasonic centrifugations with deionized water and anhydrous ethanol, and vacuum dry the solution at 80° C. to a constant weight, thereby preparing nano silver-copper wires with a length of 50 μm and a diameter of 50 nm and a gradient distribution.

[0044] Example 2:

[0045] The present invention provides a method for preparing nano silver wires, comprising the following steps:

[0046] Step 1: Pour the silver electrodeposition solution into the Ag electrodeposition tank, and let the cathode with the aluminum oxide film precipitate silver nanowires in the Ag electrodeposition tank; wherein, the deposition conditions of the silver nanowires are: deposition voltage, 0.5V at room temperature; deposition current, 1.25mA / cm 2 ; Sedimentation time, 1.5h;

[0047] Step 2: immersing the aluminum oxide film on the cathode in Step 1 in a 5% wt NaOH solution, and using a chemical dissolution method to corrode and dissolve for 20 minutes to remove the aluminum oxide film. The aluminum oxide film is then washed by multiple ultrasonic centrifugations with deionized water and anhydrous ethanol, and vacuum dried at 80° C. to a constant weight, thereby preparing nanosilver wires with a length of 55 μm and a diameter of 40-50 nm.

[0048] The remaining preparation steps are as in Example 1.

[0049] Example 3:

[0050] The present invention provides a method for preparing nano copper wires, comprising the following steps:

[0051] Step 1: Pour the copper electrodeposition solution into the Cu electrodeposition tank, and let the cathode with the aluminum oxide film deposit copper nanowires in the Cu electrodeposition tank; wherein, the deposition conditions of the copper nanowires are: deposition voltage, 1.2V, deposition current, 1.75mA / cm at room temperature. 2 , precipitation time, 3h;

[0052] Step 2: Immerse the aluminum oxide film on the cathode in Step 1 in a 5% wt NaOH solution, and use a chemical dissolution method to corrode and dissolve for 20 minutes to remove the aluminum oxide film. Then, wash the aluminum oxide film by multiple ultrasonic centrifugations with deionized water and anhydrous ethanol, and vacuum dry the solution at 80° C. to a constant weight, thereby preparing a copper-silver wire with a length of 55 μm and a diameter of 40-50 nm.

[0053] Example 4:

[0054] A method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film comprises the following steps:

[0055] Step 1: Wash the PVC substrate (transmittance 84%, thickness 180 μm) with deionized water and anhydrous ethanol to remove surface stains, and then ultrasonically vibrate for 5 minutes;

[0056] Step 2: Prepare the gradient-distributed silver nanowire-copper nanowire prepared in Example 1 into a 1 mg / mL anhydrous ethanol suspension, and ultrasonically vibrate for 0.5 h to uniformly disperse it in the solvent;

[0057] Step 3, vertically fix the PVC in step 1 on the working arm of the pulling machine, move the substrate at an immersion speed of 60 mm / min to immerse it in the suspension in step 2, and when the PVC substrate is completely immersed in the suspension, let it stand for 30 seconds, and the PVC substrate begins to leave the suspension at a lifting speed of 100 mm / min. After completely leaving the solution, it is naturally dried for 30 seconds. The immersion process is repeated three times, and then vacuum dried at 80°C for 5 minutes to obtain a nano silver wire-copper wire gradient distribution electromagnetic shielding film, wherein the nano silver wire-copper wire gradient distribution structure is as follows Figure 1 As shown;

[0058] Step 4, using a UV / visible spectrophotometer to test the optical transmittance of the nano silver wire-copper wire gradient distribution electromagnetic shielding film prepared in Step 3 at a wavelength of 550 nm is 83.11%;

[0059] Using a vector network analyzer connected to two X-band waveguides, the electromagnetic shielding performance of the nano silver wire-copper wire gradient distribution electromagnetic shielding film prepared in Step 3 was measured at room temperature, an X-band frequency band (8.2-12.4 GHz), and a bandwidth of 1 kHz. The total shielding performance was 29 dB.

[0060] Example 5:

[0061] A method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film comprises the following steps:

[0062] Step 1: Wash the PVC substrate (transmittance 84%, thickness 180 μm) with deionized water and anhydrous ethanol to remove surface stains, and then ultrasonically vibrate for 5 minutes;

[0063] Step 2: Prepare the gradient-distributed silver nanowires prepared in Example 2 into a 0.5 mg / mL anhydrous ethanol suspension, and ultrasonically vibrate for 0.5 h to uniformly disperse them in the solvent;

[0064] Step 3: Prepare the gradient-distributed copper nanowires prepared in Example 3 into a 0.5 mg / mL anhydrous ethanol suspension, and ultrasonically vibrate for 0.5 h to uniformly disperse them in the solvent;

[0065] Step 4: Fix the PVC in Step 1 vertically on the working arm of the lifting machine. The specific dipping process is as follows:

[0066] In step 4-1, the substrate was moved at a dipping speed of 60 mm / min to be immersed in the suspension prepared in step 3. When the PVC substrate was completely immersed in the suspension, it was allowed to stand for 30 seconds. The PVC substrate began to leave the suspension at a lifting speed of 100 mm / min. After being completely out of the solution, it was naturally dried for 30 seconds.

[0067] Step 4-2: Move the substrate at a dipping speed of 60 mm / min to immerse it in the suspension in step 2. When the PVC substrate is completely immersed in the suspension, let it stand for 30 seconds. The PVC substrate begins to leave the suspension at a lifting speed of 100 mm / min. After it is completely out of the solution, dry it naturally for 30 seconds.

[0068] Step 4-3, repeat the dipping process of Step 4-1 and Step 4-2 three times, and then vacuum dry at 80°C for 5 minutes to obtain a nano silver wire-copper wire gradient distribution electromagnetic shielding film, wherein the nano silver wire-copper wire gradient distribution structure is as follows Figure 2 As shown;

[0069] Step 5: Using a UV / visible spectrophotometer to test the optical transmittance of the nano silver wire-copper wire gradient distribution electromagnetic shielding film prepared in Step 4-3 at a wavelength of 550 nm is 74.31%;

[0070] Using a vector network analyzer connected to two X-band waveguides, the electromagnetic shielding performance of the nano silver wire-copper wire gradient distribution electromagnetic shielding film prepared in Step 4-3 was measured at room temperature, X-band (8.2-12.4 GHz) frequency band, and 1 kHz bandwidth. The total shielding performance was 24 dB.

[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film, characterized in that: The steps include: Step 1: washing the substrate material with deionized water and anhydrous ethanol to remove surface stains, followed by ultrasonic vibration; Step 2: Prepare a silver nanowire-copper wire array with a controllable composition ratio of 50 μm in length and 50 nm in diameter in a one-dimensional alternating gradient distribution by a double-tank electrodeposition method and a melting method. Prepare the silver nanowire-copper wire array into a suspension in anhydrous ethanol with a concentration of 0.1-5 mg / mL and ultrasonically oscillate to uniformly disperse it in the solvent. Step 3: The base material in step 1 is fixed vertically on the working arm of the pulling machine, and the base is moved at an immersion speed of 40-80 mm / min to immerse it in the suspension in step 2. When the base material is completely immersed in the suspension, it is allowed to stand, and the base material begins to leave the suspension at a lifting speed of 80-120 mm / min. After completely leaving the solution, it is naturally dried. The immersion process is repeated three times, and then vacuum dried to constant weight to obtain a nano silver wire-copper wire gradient distribution electromagnetic shielding film; The double tank electrodeposition method is: Step 1: pouring the silver electrodeposition solution into the Ag electrodeposition tank, and allowing the cathode with the aluminum oxide film to precipitate silver nanowires in the Ag electrodeposition tank; Step 2: Take out the cathode with silver nanowires deposited in the nanopores of the aluminum oxide film in step 1, soak it in deionized water for cleaning, and clean the silver electrodeposition solution; Step 3: Pour the copper electrodeposition solution into a Cu electrodeposition tank, and allow the cathode cleaned in step 2 to deposit copper nanowires in the Cu electrodeposition tank; Step 4: remove the cathode with silver nanowires and copper nanowires deposited in the nanopores of the aluminum oxide film in step 3, soak it in deionized water for cleaning, and clean the copper electrodeposition solution; Repeat the above steps 1, 2, 3, and 4 for 50-200 times, alternately depositing silver nanowires and copper nanowires; The deposition conditions of silver nanowires were as follows: deposition voltage, 0.5 V at room temperature; Deposition current, 1.25 mA / cm 2 ; Sedimentation time, 10-50s; Sedimentation length, 100-500nm; The deposition conditions of copper nanowires were as follows: deposition voltage, 1.2 V at room temperature; Deposition current, 1.75 mA / cm 2 ; Sedimentation time, 20-100s; Sedimentation length, 100-500nm.

2. The method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film according to claim 1, characterized in that: The melting method is as follows: a layer of silver paste is applied to the front of the aluminum oxide film with silver nanowires and copper nanowires deposited in the nanopores to block the pores of the aluminum oxide film, and then the mixture is melted and mixed at 600-650°C for 2-5 hours under nitrogen protection.

3. The method for preparing a nano silver wire-copper wire gradient distribution electromagnetic shielding film according to claim 1, characterized in that: The base material is one of polyvinyl chloride (PVC), polyester film and glass film.

4. The nano silver wire-copper wire gradient distribution electromagnetic shielding film prepared by the method according to any one of claims 1 to 3, characterized in that: The optical transmittance of the electromagnetic shielding film at a wavelength of 550nm is above 80%, and the electromagnetic shielding performance is 20-30dB.

Images