Method for preparing PTFE film sputtering and electroplating metal layer

Abstract

This invention relates to the field of metallization technology for membrane materials, specifically disclosing a method for preparing a PTFE membrane by sputtering and electroplating a metal layer. The method includes: PTFE membrane pretreatment, magnetron sputtering of a transition layer, selective electroplating of a metal layer, and post-treatment. This invention combines multi-target magnetron sputtering with multi-metal selective electroplating, resulting in a simplified process with controllable parameters. The sputtering transition layer exhibits excellent adhesion to the PTFE membrane and each metal coating. The resulting coating meets the 5B grade requirement of the ASTM D3359 standard's cross-cut adhesion test. The coating is uniform and dense, achieving high conductivity and strong corrosion resistance, while retaining the original flexibility and temperature resistance of the PTFE membrane. It is suitable for diverse applications such as electromagnetic shielding, chemical corrosion protection, and flexible electronic packaging.

Description

Technical Field

[0001] This invention relates to the field of membrane metallization technology, specifically to a method for preparing a PTFE membrane by sputtering and electroplating a metal layer. Background Technology

[0002] Polytetrafluoroethylene (PTFE) membranes, due to the tight encapsulation of carbon chains by fluorine atoms in their molecular structure, possess extremely low surface energy, excellent corrosion resistance, high-temperature resistance, insulation, and flexibility. They are widely used in industries such as chemical corrosion protection, microwave high-frequency communication, flexible electronic component packaging, and aerospace. To further expand the functionality of PTFE membranes and endow them with conductive, electromagnetic shielding, or high abrasion resistance properties, surface metallization treatment is necessary.

[0003] However, PTFE membranes are extremely chemically inert, lack polar active groups on their surface, and have very low surface energy (approximately 18-20 dyn / cm), making conventional metal deposition layers prone to peeling and detachment. The metallization of PTFE membranes in existing technologies mainly faces the following technical bottlenecks: 1. Traditional chemical plating as a base layer has a long process and often uses highly corrosive solutions (such as sodium naphthalene complex) for surface roughening. This not only damages the original flexibility and mechanical strength of the PTFE film, but also results in high porosity and poor adhesion of the chemical plating layer, which greatly reduces the performance of the subsequent electroplating layer and causes serious environmental pollution.

[0004] 2. Existing magnetron sputtering-assisted electroplating processes mostly use a single metallic chromium as the base target material, resulting in extremely poor process flexibility and failing to meet the differentiated high-end application requirements such as high temperature resistance (requiring titanium targets) and strong corrosion resistance (requiring nickel-chromium targets).

[0005] 3. Coating adhesion cannot overcome industry bottlenecks. Existing sputtering processes often have a rough control over the thickness of the transition layer. If the sputtered layer is too thick, it will cause a sharp increase in internal residual stress, leading to film peeling. If it is too thin, it will be impossible to form a continuous conductive network for subsequent electroplating. At the same time, there is a lack of subsequent electroplating solution formulations that are highly compatible with different sputtering targets. Ultimately, the adhesion between the finished metal layer and the PTFE film can generally only reach 3B or 4B level (100-cross test), making it extremely difficult to stably meet the high standard of 5B adhesion required in high-frequency or harsh environments.

[0006] Based on the above statements, this invention proposes a method for preparing a PTFE film by sputtering and electroplating a metal layer. Summary of the Invention

[0007] To address the technical problems in existing technologies, such as poor adhesion due to the strong inertness of the PTFE film surface, difficulty in controlling the thickness of the transition layer in traditional sputtering processes, detachment caused by high residual stress, and poor compatibility with multiple targets, this invention proposes a method for preparing a PTFE film by sputtering and electroplating a metal layer.

[0008] This invention provides a method for preparing a PTFE film by sputtering and electroplating a metal layer, using the following technical solution: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select PTFE membrane as substrate, and perform neutral degreasing and plasma activation treatment in sequence to obtain pretreated PTFE membrane; Step 2: Using one of metallic chromium, titanium, or nickel-chromium alloy as the target material, the pretreated PTFE film is sputtered in a vacuum environment by magnetron sputtering to deposit a nano-transition layer with a thickness of 20 nm. Step 3: Select at least one of copper, nickel, and silver as the electroplating metal M for electroplating treatment to form a metal coating. After electroplating, rinse the film material repeatedly with deionized water and obtain a PTFE film with a metal coating by vacuum drying. Step 4: Heat the PTFE film with the metal layer at 100-120℃ for 20-30 minutes, and then let it cool naturally to room temperature to obtain the finished product.

[0009] Preferably, in step 1, the thickness of the PTFE membrane is 50-200 μm.

[0010] Preferably, in step 1, the neutral degreasing is performed using an aqueous solution of fatty alcohol polyoxyethylene ether 3-5 g / L and polyether polyol 2-4 g / L, treated with ultrasonic power of 300-500 W at 30-40℃ for 10-20 min.

[0011] Preferably, in step 1, plasma activation uses a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 5-8:1, an activation power of 100-150W, and an activation time of 3-5 minutes.

[0012] Preferably, in step 2, the purity of the sputtering target is ≥99.99%.

[0013] Preferably, in step 2, the process parameters for magnetron sputtering are: vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, sputtering power 120-180W, argon flow rate 20-30sccm, substrate temperature 40-60℃, sputtering rate 0.5-1nm / s.

[0014] Preferably, in step 3, when the electroplated metal M is copper, an acidic copper plating solution is used for electroplating. The acidic copper plating solution consists of: 200-250 g / L copper sulfate, 60-80 g / L sulfuric acid, 50-80 mg / L chloride ions, 0.5-1.5 mg / L brightener, 0.3-0.8 ml / L leveling agent, and the remainder is deionized water.

[0015] Preferably, when the electroplated metal M is copper, the brightener is sodium polydisulfide dipropane sulfonate.

[0016] Preferably, when the electroplated metal M is copper, the leveling agent is polyethylene glycol.

[0017] Preferably, the electroplating process parameters for the electroplated metal M, which is copper, are as follows: using pure copper sheet with a purity ≥ 99.95% as the anode, and a current density of 1-3 A / dm³. 2 The electroplating temperature is 25-35℃, the electroplating time is 15-40min, the stirring rate is 300-500r / min, and the copper layer thickness is 0.5-5μm.

[0018] Preferably, in step 3, when the electroplating metal M is nickel, an acidic nickel plating solution is used for electroplating. The acidic nickel plating solution consists of: 250-300 g / L nickel sulfate, 40-60 g / L nickel chloride, 30-40 g / L boric acid, 0.3-0.8 g / L brightener, 0.1-0.3 g / L leveling agent, and the balance being deionized water.

[0019] Preferably, when the electroplated metal M is nickel, the brightener is sodium saccharin.

[0020] Preferably, when the electroplated metal M is nickel, the leveling agent is sodium dodecyl sulfate.

[0021] Preferably, the electroplating process parameters for the electroplated metal M, which is nickel, are as follows: using a pure nickel plate with a purity ≥ 99.95% as the anode, and a current density of 2-4 A / dm³. 2 The electroplating temperature is 40-50℃, the electroplating time is 10-30 min, the stirring rate is 300-500 r / min, and the nickel layer thickness is 0.2-2 μm.

[0022] Preferably, in step 3, when the electroplating metal M is silver, an electroplating silver solution is used for electroplating. The composition of the electroplating silver solution is: 30-50 g / L silver nitrate, 80-120 g / L potassium cyanide, 20-30 g / L potassium carbonate, and the balance is deionized water.

[0023] Preferably, the electroplating process parameters for the electroplated metal M, which is silver, are as follows: using pure silver sheet with a purity ≥ 99.95% as the anode, and a current density of 0.5-1.5 A / dm³. 2 The electroplating temperature is 20-30℃, the electroplating time is 5-15min, and the silver layer thickness is 0.1-1μm.

[0024] Preferably, in step 3, the vacuum drying temperature is 60-80℃ and the time is 15-25 minutes.

[0025] In summary, the present invention has the following beneficial effects: 1. Excellent coating adhesion, stable to 5B grade cross-cut adhesion test standard: Active groups are introduced into the PTFE film surface through plasma activation to form a micro-rough structure. Combined with a 20nm precise thickness transition layer by magnetron sputtering of chromium, titanium, and nickel-chromium alloy multi-target materials, and stress elimination in post-treatment, the interlayer adhesion is fundamentally improved. The resulting copper, nickel, and silver coatings all meet the 5B grade standard in the ASTM D3359 cross-cut adhesion test. The cut edges are completely smooth, and there is no coating peeling within the grid. The coating stability far exceeds the industry standard.

[0026] 2. High process flexibility, enabling flexible combination of multiple targets and metals: During the sputtering stage, any target material such as chromium, titanium, or nickel-chromium alloy can be selected, and during the electroplating stage, any metal such as copper, nickel, or silver can be selected. It can be flexibly combined according to the application scenario requirements. For example, chromium target + copper plating is suitable for electromagnetic shielding scenarios with high adhesion, titanium target + silver plating is suitable for high-end high-temperature resistant electronic packaging scenarios, and nickel-chromium alloy target + nickel plating is suitable for harsh chemical corrosion protection scenarios, which greatly improves the product's scenario adaptability.

[0027] 3. Streamlined and efficient process, green and environmentally friendly: Abandoning the traditional chemical plating base steps, the process adopts a four-step streamlined process of "pretreatment-sputtering-electroplating-posttreatment", which shortens the production cycle and reduces process costs; the plating solutions all use environmentally friendly components (except for silver plating solution, which is suitable for high-end scenarios), the rinsing water after electroplating can be easily treated and reused, with low pollutant emissions, which meets green production standards, and multiple process parameters are controllable, making it easy to achieve industrial scale-up.

[0028] 4. Excellent coating performance, retaining the core characteristics of PTFE film: the copper, nickel, and silver coatings are all uniform and dense, without pinholes or pits, and the resistivity of the copper layer is as low as 1.7×10⁻⁶. -8 With excellent conductivity (Ω·m), the nickel layer has resistance to neutral salt spray corrosion for ≥200h and outstanding corrosion resistance, while the silver layer has ultra-high conductivity. Titanium and nickel-chromium alloy sputtering targets can also simultaneously improve the high temperature resistance and corrosion resistance of the finished product. The entire process does not involve high-temperature and strong corrosion treatment, effectively preserving the original core characteristics of PTFE film such as flexibility, high temperature resistance, and low coefficient of friction.

[0029] 5. Controllable parameters, suitable for continuous industrial production: All process parameters are controllable within a range. Sputtering and electroplating processes can be perfectly adapted to roll-to-roll equipment, enabling continuous and large-scale production of PTFE film metallization. The process has good repeatability, high product qualification rate, and low production cost. At the same time, the coating adhesion is stable and meets the 5B grade cross-cut adhesion test standard. The product quality is highly controllable and has good prospects for industrial application. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the embodiments.

[0031] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0032] Among them, fatty alcohol polyoxyethylene ether: fatty alcohol polyoxyethylene ether AEO-9, was purchased from Jinan Yuanlian Chemical Co., Ltd.

[0033] Polyether polyol: Polyether polyol 330, purchased from Haian Petrochemical Plant, Jiangsu Province.

[0034] Sodium polydisulfide dipropane sulfonate: CAS No. 27206-35-5, model wd2116, purchased from Hubei Wode Chemical Technology Co., Ltd.

[0035] Polyethylene glycol: PEG400, purchased from Jinan Hengcheng New Materials Co., Ltd.

[0036] Examples 1-3 provide a method for preparing a PTFE film by sputtering and electroplating a metal layer.

[0037] Example 1 A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to perform neutral degreasing by ultrasonic treatment at 300W for 20min at 30℃. Then, use a mixed gas of argon and oxygen with a volume ratio of 5:1 for plasma activation treatment, control the activation power at 100W and the activation time at 5min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3 Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 20nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2 The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 60℃ for 25min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 100℃ for 30 minutes, then let it cool naturally to room temperature to obtain the finished product.

[0038] Example 2 A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 120μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 4g / L and polyether polyol 3g / L to perform neutral degreasing by ultrasonic treatment at 35℃ with a power of 400W for 15min. Then, use a mixed gas of argon and oxygen with a volume ratio of 6.5:1 for plasma activation treatment, control the activation power at 120W and the activation time at 4min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure titanium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4.5 × 10⁻⁶. -3 Pa, sputtering power 150W, argon flow rate 25sccm, substrate temperature 50℃, sputtering rate 0.8nm / s, depositing a nano-transition layer with a thickness of 20nm; Step 3: Prepare an acidic nickel plating solution containing 275 g / L nickel sulfate, 50 g / L nickel chloride, 35 g / L boric acid, 0.5 g / L sodium saccharin, and 0.2 g / L sodium dodecyl sulfate, with the balance being deionized water; use a pure nickel plate with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 3 A / dm³. 2 The electroplating temperature was 45℃, the electroplating time was 20min, the stirring rate was 400r / min, and the nickel layer thickness was 1μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 70℃ for 20min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 110℃ for 25 minutes, and then let it cool naturally to room temperature to obtain the finished product.

[0039] Example 3 A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 200μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 5g / L and polyether polyol 4g / L to perform neutral degreasing by ultrasonic treatment at 40℃ with a power of 500W for 10min. Then, use a mixed gas of argon and oxygen with a volume ratio of 8:1 for plasma activation treatment, control the activation power at 150W and the activation time at 3min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 5×10⁻⁶. -3 Pa, sputtering power 180W, argon flow rate 30sccm, substrate temperature 60℃, sputtering rate 1nm / s, depositing a nano-transition layer with a thickness of 20nm. Step 3: Prepare the silver plating solution, containing 40 g / L silver nitrate, 100 g / L potassium cyanide, and 25 g / L potassium carbonate, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 1 A / dm³. 2 The electroplating temperature was 25℃, the electroplating time was 10min, and the silver layer thickness was 0.5μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 80℃ for 15min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 120℃ for 20 minutes, and then let it cool naturally to room temperature to obtain the finished product.

[0040] To verify the overall performance of the PTFE film sputtering and electroplating metal layer preparation method provided by the present invention, comparative examples 1-5 were set up, wherein: Comparative Example 1 Comparative Example 1 is the same as Example 1, except that the gas used for plasma activation in step 1 is argon. Details are as follows: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to treat it with ultrasonic power of 300W at 30℃ for 20min for neutral degreasing. Then, use argon gas for plasma activation treatment, control the activation power to 100W and the activation time to 5min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3 Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 20nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 60℃ for 25min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 100℃ for 30 minutes, then let it cool naturally to room temperature to obtain the finished product.

[0041] Comparative Example 2 Comparative Example 2 is the same as Example 1, except that the plasma activation treatment step in step 1 is omitted. Specifically: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate, and use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to perform neutral degreasing by ultrasonic treatment at 30℃ and 300W power for 20min to obtain a pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3 Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 20nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2 The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 60℃ for 25min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 100℃ for 30 minutes, then let it cool naturally to room temperature to obtain the finished product.

[0042] Comparative Example 3 Comparative Example 3 is the same as Example 1, except that the magnetron sputtering time in step 2 is shortened, resulting in a nano-transition layer thickness of only 5 nm. Details are as follows: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to perform neutral degreasing by ultrasonic treatment at 300W for 20min at 30℃. Then, use a mixed gas of argon and oxygen with a volume ratio of 5:1 for plasma activation treatment, control the activation power at 100W and the activation time at 5min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3 Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 5nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2 The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 60℃ for 25min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 100℃ for 30 minutes, then let it cool naturally to room temperature to obtain the finished product.

[0043] Comparative Example 4 Comparative Example 4 is the same as Example 1, except that the magnetron sputtering time in step 2 is extended, resulting in a nano-transition layer thickness of 40 nm. Details are as follows: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to perform neutral degreasing by ultrasonic treatment at 300W for 20min at 30℃. Then, use a mixed gas of argon and oxygen with a volume ratio of 5:1 for plasma activation treatment, control the activation power at 100W and the activation time at 5min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 40nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2 The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times and then vacuum dried at 60℃ for 25min to obtain a PTFE film with a metal layer. Step 4: Heat the PTFE film with the metal coating at 100℃ for 30 minutes, then let it cool naturally to room temperature to obtain the finished product.

[0044] Comparative Example 5 Comparative Example 5 is the same as Example 1, except that step 4 is omitted. Details are as follows: A method for preparing a PTFE film by sputtering and electroplating a metal layer includes the following steps: Step 1: Select a PTFE membrane with a thickness of 50μm as the substrate. Use an aqueous solution of fatty alcohol polyoxyethylene ether 3g / L and polyether polyol 2g / L to perform neutral degreasing by ultrasonic treatment at 300W for 20min at 30℃. Then, use a mixed gas of argon and oxygen with a volume ratio of 5:1 for plasma activation treatment, control the activation power at 100W and the activation time at 5min to obtain the pretreated PTFE membrane. Step 2: Using 99.99% pure metallic chromium as the target material, the pretreated PTFE film is sputtered in a vacuum environment using magnetron sputtering, with the vacuum level controlled at 4×10⁻⁶. -3 Pa, sputtering power 120W, argon flow rate 20sccm, substrate temperature 40℃, sputtering rate 0.5nm / s, depositing a nano-transition layer with a thickness of 20nm; Step 3: Prepare an acidic copper plating solution containing 220 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, 1 mg / L sodium dithiopropane sulfonate, 0.5 ml / L polyethylene glycol, with the remainder being deionized water; use a pure copper sheet with a purity ≥ 99.95% as the anode and a sputtered PTFE film as the cathode, controlling the current density to 2 A / dm³. 2 The electroplating temperature was 30℃, the electroplating time was 28min, the stirring rate was 400r / min, and the copper layer thickness was 3μm. After electroplating, the film was repeatedly rinsed with deionized water 3 times, vacuum dried at 60℃ for 25min, and naturally cooled to room temperature to obtain the finished product.

[0045] The comprehensive performance of the PTFE films sputtered and electroplated with metal layers prepared in Examples 1-3 and Comparative Examples 1-5 of this invention was tested respectively.

[0046] Coating adhesion: Performed according to ASTM D3359 standard 100-cross adhesion test (5B means no peeling, 0B means complete peeling).

[0047] Peel bond strength: Tested according to GB / T 2792-2014 standard, peel bond strength (unit: N / 10mm) was measured at a 90° peel angle. Surface macroscopic morphology observation: Under normal temperature light source, observe the smoothness, density and presence of defects such as blistering, pitting and cracks on the coating surface with the naked eye and a 50x optical microscope.

[0048] Volume resistivity test: According to GB / T 1551-2021 standard, a four-probe thin film resistivity tester was used to test the metal coating of the sample under constant temperature of 25℃. Five different locations were measured for each sample, and the average value was taken. The unit is Ω·m.

[0049] Neutral salt spray corrosion test: Conducted according to GB / T 10125-2021 standard, using a 5wt% NaCl aqueous solution, adjusting the pH of the liquid to 6.8, and maintaining the test chamber temperature at 35℃. The test sample is placed in the salt spray chamber at an angle of 15° to 30°. The surface condition of the coating is observed and recorded every 12 hours, recording the time it takes for obvious pitting, pitting, or red rust to appear. The test is stopped if no corrosion points are observed after 240 hours. The time unit is hours.

[0050] The test results are shown in Table 1: Table 1: Comprehensive performance test data of PTFE film sputtering and electroplating metal layer in Examples 1-3 and Comparative Examples 1-5 As shown in Table 1, the PTFE films sputtered and electroplated metal layers prepared in Examples 1-3 of this invention all exhibit excellent comprehensive performance. Their coating adhesion consistently meets the 5B standard, with peel strength between 3.52-3.65 N / 10 mm, and the surfaces are dense, free of pinholes and blistering defects. Meanwhile, the copper coating prepared in Example 1 exhibits extremely low resistivity, demonstrating excellent conductivity; the nickel coating prepared in Example 2 showed no corrosion points after 240 hours of neutral salt spray testing, meeting stringent corrosion protection requirements; and the silver coating prepared in Example 3 possesses excellent electrical properties. Their overall performance is significantly superior to that of Comparative Examples 1-5.

[0051] As shown in Example 1 and Comparative Example 1, after replacing the plasma activation gas from a mixture of argon and oxygen to pure argon, the peel adhesion decreased from 3.65 N / 10 mm to 2.65 N / 10 mm, and the coating adhesion dropped to level 4B. The decreased microscopic adhesion resulted in impaired coating density, and its volume resistivity increased to 1.85 × 10⁻⁶. -8 Ω·m. This indicates that pure argon plasma only has a single physical etching and roughening effect on the PTFE surface, while the addition of oxygen can introduce oxygen-containing polar groups (such as -OH, -COOH) at the breakage of the PTFE macromolecular chain, significantly improving the surface energy and interlayer bonding force through the synergistic effect of physical interlocking and chemical bonding.

[0052] As shown in Example 1 and Comparative Example 2, when the plasma activation treatment step after neutral degreasing is completely omitted, the peel adhesion drops sharply to 0.85 N / 10 mm, the coating adhesion is only grade 1B, and there are obvious bubbles and local peeling on the metal layer surface. This indicates that the surface of the unactivated PTFE film has extremely high chemical inertness and extremely low surface energy, and sputtered metal atoms cannot form an effective anchor on its surface, making it difficult for subsequent electroplating layers to adhere and making them very easy to peel off.

[0053] As shown in Example 1 and Comparative Example 3, reducing the deposition thickness of the sputtered nano-transition layer from 20 nm to 5 nm resulted in a decrease in peel strength to 2.15 N / 10 mm, a decrease in coating adhesion to grade 3B, and the appearance of pitting on the coating surface. These pitting micropores blocked some electron transport paths, causing the resistivity to increase to 2.80 × 10⁻⁶. -8 The Ω·m thickness provides a penetration channel for salt spray, accelerating corrosion. This indicates that an excessively thin transition layer cannot form a continuous, dense conductive network on the PTFE substrate surface. During subsequent electroplating, uneven current distribution leads to micropores in the metal deposition, resulting in a decrease in macroscopic adhesion.

[0054] As shown in Example 1 and Comparative Example 4, increasing the deposition thickness of the sputtered nano-transition layer from 20 nm to 40 nm resulted in a sharp decrease in peel adhesion to 1.45 N / 10 mm, a drop in coating adhesion to grade 2B, the appearance of microcracks on the surface, and these microcracks becoming direct channels for corrosive media. The salt spray test time was also shortened to 18 hours. This indicates that with increasing metal film thickness, the residual stress within the coating increases exponentially. When the transition layer is too thick, excessive internal stress directly disrupts the weak van der Waals forces and chemical bonds between the metal film and the PTFE substrate, causing coating cohesion failure and spontaneous detachment.

[0055] As shown in Example 1 and Comparative Example 5, omitting the 100-120℃ heat treatment and natural cooling steps resulted in a decrease in peel strength to 2.85 N / 10 mm and a coating adhesion grade of 4B. Unreleased internal stress caused lattice distortion at the grain boundaries, slightly affecting conductivity and corrosion resistance. This indicates that residual internal stress inevitably accumulates within the coating during the multiple phase transitions and ion deposition processes of vacuum magnetron sputtering and liquid phase electroplating. Without annealing within a specific temperature range to release this stress, it will persist at the grain boundaries and phase interfaces for a long time. Under external shearing forces (such as cross-cutting or peeling), the unreleased stress will accelerate interface fracture, preventing the overall bonding strength from reaching its optimal state.

[0056] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a PTFE film by sputtering and electroplating a metal layer, characterized in that, Includes the following steps: Step 1: Select PTFE membrane as substrate, and perform neutral degreasing and plasma activation treatment in sequence to obtain pretreated PTFE membrane; Step 2: Using one of metallic chromium, titanium, or nickel-chromium alloy as the target material, the pretreated PTFE film is sputtered in a vacuum environment by magnetron sputtering to deposit a nano-transition layer with a thickness of 20 nm. Step 3: Select at least one of copper, nickel, and silver as the electroplating metal M for electroplating treatment to form a metal coating. After electroplating, rinse the film material repeatedly with deionized water and obtain a PTFE film with a metal coating by vacuum drying. Step 4: Heat the PTFE film with the metal layer at 100-120℃ for 20-30 minutes, and then let it cool naturally to room temperature to obtain the finished product.

2. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 1, the neutral degreasing process uses an aqueous solution of fatty alcohol polyoxyethylene ether 3-5 g / L and polyether polyol 2-4 g / L, which is treated with ultrasonic power of 300-500 W at 30-40℃ for 10-20 min.

3. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 1, plasma activation uses a mixture of argon and oxygen gas with a volume ratio of argon to oxygen of 5-8:1, an activation power of 100-150W, and an activation time of 3-5min.

4. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 2, the process parameters for magnetron sputtering are: vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, sputtering power 120-180W, argon flow rate 20-30sccm, substrate temperature 40-60℃, sputtering rate 0.5-1nm / s.

5. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 3, when the electroplated metal M is copper, an acidic copper plating solution is used for electroplating. The acidic copper plating solution consists of: 200-250 g / L copper sulfate, 60-80 g / L sulfuric acid, 50-80 mg / L chloride ions, 0.5-1.5 mg / L brightener, 0.3-0.8 ml / L leveling agent, and the remainder is deionized water.

6. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 5, characterized in that, The electroplating process parameters for the electroplated metal M, which is copper, are as follows: using pure copper sheet with a purity ≥ 99.95% as the anode, and a current density of 1-3 A / dm³. 2 The electroplating temperature is 25-35℃, the electroplating time is 15-40min, the stirring rate is 300-500r / min, and the copper layer thickness is 0.5-5μm.

7. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 3, when the electroplating metal M is nickel, an acidic nickel plating solution is used for electroplating. The acidic nickel plating solution consists of: 250-300 g / L nickel sulfate, 40-60 g / L nickel chloride, 30-40 g / L boric acid, 0.3-0.8 g / L brightener, 0.1-0.3 g / L leveling agent, and the balance being deionized water.

8. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 7, characterized in that, The electroplating process parameters for the electroplated metal M, which is nickel, are as follows: using a pure nickel plate with a purity ≥ 99.95% as the anode, and a current density of 2-4 A / dm³. 2 The electroplating temperature is 40-50℃, the electroplating time is 10-30 min, the stirring rate is 300-500 r / min, and the nickel layer thickness is 0.2-2 μm.

9. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 1, characterized in that, In step 3, when the electroplating metal M is silver, an electroplating silver solution is used for electroplating. The composition of the electroplating silver solution is: 30-50 g / L silver nitrate, 80-120 g / L potassium cyanide, 20-30 g / L potassium carbonate, and the balance is deionized water.

10. The method for preparing a PTFE film by sputtering and electroplating a metal layer according to claim 9, characterized in that, The electroplating process parameters for the electroplated metal M, which is silver, are as follows: using pure silver sheet with a purity ≥ 99.95% as the anode, and a current density of 0.5-1.5 A / dm³. 2 The electroplating temperature is 20-30℃, the electroplating time is 5-15min, and the silver layer thickness is 0.1-1μm.

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