A method for preparing a polytetrafluoroethylene flexible conductive circuit

Abstract

The present invention discloses a method for preparing a polytetrafluoroethylene (PTFE) flexible conductive circuit. The method first utilizes the synergistic effect of the chemical etching effect of a relatively low-concentration sodium naphthalene treatment solution and the etching effect of an ultraviolet pulsed laser to achieve good hydrophilic wetting properties in the laser-etched circuit pattern area, while hydrophobicity is exhibited outside the laser-etched circuit pattern. After laser etching, a metal ion or metal complex ion activation solution is coated on the surface of the PTFE flexible substrate. The activation solution rapidly wets the laser-etched circuit pattern. Finally, the polytetrafluoroethylene (PTFE) flexible conductive circuit is prepared through chemical plating. This method solves the problems in the prior art of preparing PTFE flexible conductive circuits, such as the difficulty in achieving the desired result, the harsh preparation conditions, the complex process steps, and the low industrial application value.

Description

Technical Field

[0001] The present invention belongs to the application field of combined laser surface treatment and chemical etching treatment, and more specifically, relates to a method for preparing a polytetrafluoroethylene (PTFE) flexible conductive circuit. Background Art

[0002] Flexible conductive circuits are the key to the preparation of flexible electronic devices due to their good flexibility, light weight and bendability. They are widely used in wearable electronic devices, flexible equipment, flexible displays, flexible skin, motion monitoring and other fields.

[0003] PTFE film is a perfluorinated linear polymer composed of carbon and fluorine covalently bonded together. It exhibits excellent chemical and aging resistance, lubricity, and radiation resistance. It also exhibits excellent high and low-temperature resistance, capable of long-term operation in temperatures ranging from -250°C to 260°C. It has long been widely used in numerous fields, including electronics, aerospace, and automotive manufacturing. Its low dielectric constant, low dielectric loss, and low water absorption make it an ideal material for high-frequency flexible printed circuit boards (PCBs). Traditional methods for fabricating flexible circuits include screen printing, gravure printing, microcontact printing, and inkjet printing. However, due to the extremely low surface energy of PTFE, its surface exhibits intrinsic superhydrophobicity, making it difficult to wet and non-stick. Therefore, it is difficult to construct flexible conductive circuits on PTFE film using these techniques, significantly limiting its application in flexible electronic devices.

[0004] Compared with these preparation technologies, laser processing technology has many advantages such as good regional selectivity, a wide range of processable materials, non-contact, and low pollution. In particular, it can be precisely controlled through computer software, giving it obvious advantages in the preparation of flexible conductive circuits.

[0005] At present, Lin et al. reported in the Journal of Adhesion Science and Technology (2000, 14(1): 1-14) that PTFE was treated with a sodium naphthalene tetrahydrofuran solution and then subjected to chemical copper plating. They found that the sodium naphthalene solution treatment effectively improved the wettability of the PTFE surface and increased the bonding strength between the PTFE and the surface copper layer. However, due to the lack of regional selectivity, this preparation method is difficult to apply to the preparation of conductive circuits. Niino et al. proposed in the journal Applied Surface Science (1996, 96: 550-557) that PTFE was metallized using a 193 nm ArF excimer laser modified with a combined chemical plating method. However, this preparation technique requires the prepared PTFE to be placed in a vacuum environment before hydrazine gas (highly toxic) is introduced into it. The experimental conditions are harsh and the risk factor is high, making it of low value for industrial production application. Mochizuki et al. published a paper in the journal MRS Online Proceedings Library, 2004, 843, in which they first irradiated PTFE with a Xe2 excimer lamp in ozone to render its surface hydrophilic. The surface was then placed in a CuSO4 solution and induced to generate copper atoms by irradiation with a 193 nm ArF excimer laser. Finally, the modified PTFE was plated with copper in an electroless plating bath. This process can produce copper-layered electronic circuits on the PTFE surface, but it also requires vacuum operation, which is a demanding process and significantly limits its industrial application. Pérez et al., in the journal Indian Journal of Materials Science, 2016, 2016:1-4, proposed using plasma technology to treat the PTFE surface area before electroless copper plating, achieving a copper layer bonding strength of 3.82 MPa on the PTFE surface. Summary of the Invention

[0006] To address the above-mentioned shortcomings or improvements in the prior art, the present invention provides a method for preparing a flexible polytetrafluoroethylene (PTFE) conductive circuit. First, a PTFE film of a predetermined thickness is placed in a quartz bath, and a thin quartz glass sheet is placed over the PTFE surface. Next, a pre-prepared sodium naphthalene treatment solution is injected into the bath, forming a thin liquid layer between the PTFE surface and the quartz glass sheet. Laser treatment is then performed, and finally, chemical plating is performed to produce the flexible PTFE conductive circuit. This method addresses the difficulties in producing flexible PTFE conductive circuits in the prior art, as well as the harsh preparation conditions, complex process steps, and low industrial application value.

[0007] In order to achieve the above object, according to one aspect of the present invention, a method for preparing a polytetrafluoroethylene flexible conductive circuit is provided, comprising the following steps:

[0008] (1) Preparation of sodium naphthalene treatment solution: Tetrahydrofuran, refined naphthalene and metallic sodium are used as raw materials to prepare a sodium naphthalene treatment solution of a certain concentration.

[0009] (2) Placement of PTFE film and injection of sodium naphthalene treatment solution: Select a PTFE film of a certain thickness and lay it flat on the bottom of the quartz tank. The surface must be flat. Then, inject the appropriate amount of sodium naphthalene treatment solution prepared in (1) onto the PTFE surface. Then, cover the sodium naphthalene treatment solution with a quartz glass sheet.

[0010] (3) Laser processing: According to the set circuit pattern, the PTFE surface in (2) is processed by laser. During laser processing, the synergistic effect of the laser etching effect and the chemical etching effect of the naphthalene treatment solution is utilized to make the laser-etched area exhibit good hydrophilic wetting properties, while the laser-unetched area still exhibits hydrophobic properties.

[0011] (4) Cleaning: Use tap water and distilled water respectively to clean the PTFE film processed in (3).

[0012] (5) Pre-setting an activator: Pre-setting a solution containing metal ions or metal complex ions on the surface of the PTFE film obtained in step (4). The solution of metal ions or metal complex ions will quickly wet the laser-etched circuit pattern.

[0013] (6) Chemical plating: The PTFE flexible film treated in step (5) is placed in a chemical plating solution to deposit a metal layer, thereby obtaining a PTFE flexible conductive circuit.

[0014] Preferably, the concentration of the sodium naphthalene treatment solution used in step (1) is 0.05-0.25 mol / L.

[0015] Preferably, the thickness of the quartz glass sheet in step (2) is preferably 0.2 mm to 0.6 mm.

[0016] Preferably, the thickness of the sodium naphthalene treatment solution between the quartz glass sheet and the PTFE film in step (2) is preferably 0.50-1.00 mm.

[0017] Preferably, the sodium naphthalene treatment solution between the quartz glass sheet and the PTFE in step (2) cannot contain bubbles.

[0018] Preferably, the laser used in step (3) is an ultraviolet band pulse laser, the pulse laser power is preferably 4W-12W, the laser scanning rate is preferably 500-1000 mm / s, the scanning spacing is preferably 5-40 μm, and the laser pulse frequency is preferably 50KHz-20MHz.

[0019] In step (2) and step (3), the PTFE film is preferably immersed in the naphthalene treatment solution for 1-3 minutes.

[0020] Preferably, the specific steps of cleaning in step (4) are: placing the laser-processed PTFE obtained in step (3) in tap water and distilled water for rinsing for 20-300 s respectively.

[0021] Preferably, the solution of metal ions or metal complex ions in step (5) is a solution composed of one or more ions or complex ions of aluminum, copper, zinc, nickel, iron, manganese, molybdenum, gold, ruthenium, tungsten, rhodium, and silver, and the concentration of the metal ions or metal complex ions is preferably 0.04-2.00 mol / L.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0023] (1) Compared with the excimer laser preparation technology, the present invention does not need to be in a vacuum environment or in a certain chemical atmosphere. It is easy to operate and more suitable for application in industrial production.

[0024] (2) Although the effect of treating PTFE with sodium naphthalene solution is good, it is difficult to achieve regional selective modification. The present invention can achieve regional selective modification by combining sodium naphthalene wet chemical etching treatment with laser etching treatment, so that flexible conductive circuits can be successfully prepared on PTFE, and the bonding between PTFE and the surface metal layer is relatively high.

[0025] (3) The modification treatment of PTFE materials with a single sodium naphthalene solution takes a long time. However, the combination of sodium naphthalene wet chemical treatment and laser etching treatment can effectively shorten the time required for PTFE modification, which is more suitable for application in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the placement of PTFE film during composite film preparation;

[0027] Figure 2 It is a structural schematic diagram of the PTFE flexible conductive circuit;

[0028] 1-naphthalene sodium treatment solution; 2-quartz glass sheet; 3-PTFE film; 4-quartz tank; 301-hydrophobic surface; 302-flexible conductive circuit. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] The present invention provides a method for preparing a polytetrafluoroethylene flexible conductive circuit, characterized by comprising the following steps:

[0031] (1) Preparation of sodium naphthalene solution: Use tetrahydrofuran, refined naphthalene and metallic sodium as raw materials to prepare a sodium naphthalene treatment solution of a certain concentration.

[0032] The concentration of the sodium naphthalene solution used in step (1) is preferably 0.05-0.25 mol / L. The concentration of the sodium naphthalene solution cannot be too high. The main reason is that during the laser etching process, a high concentration of sodium naphthalene solution is too chemically corrosive and will chemically etch away the laser-unetched areas outside the circuit pattern in a short period of time, thereby making both the circuit pattern area and the area outside the circuit pattern hydrophilic, making it impossible to successfully prepare the conductive circuit.

[0033] (2) Placement of PTFE film and injection of sodium naphthalene treatment solution: Select a PTFE film of a certain thickness and lay it flat on the bottom of the quartz tank. The surface must be flat. Then, inject the appropriate amount of sodium naphthalene solution prepared in (1) onto the PTFE surface. Then, cover the sodium naphthalene treatment solution with a quartz glass sheet.

[0034] The thickness of the quartz glass sheet used in step (2) is preferably 0.2 mm to 0.6 mm. The quartz glass sheet should not be too thick or too thin. A thick quartz glass sheet will absorb more laser energy, while a thin quartz glass sheet will easily break during the experiment.

[0035] In step (2), the distance between the quartz glass sheet and the upper surface of the PTFE is preferably 0.50 mm to 1.00 mm. Since a gap is reserved between the lower surface of the quartz glass sheet and the upper surface of the PTFE, it is for the purpose of filling the naphthalene solution prepared in (1) into the gap, thereby chemically etching the upper surface of the PTFE. The naphthalene solution itself is dark green or dark brown. Therefore, the thickness of the liquid layer between the lower surface of the quartz glass sheet and the upper surface of the PTFE cannot be too large, otherwise it will absorb more laser energy.

[0036] In step (2), the sodium naphthalene solution between the quartz glass sheet and the PTFE film must not contain any bubbles. This is because the presence of bubbles will cause a large amount of scattering and refraction of the processing laser, which will rapidly reduce its energy and affect the width of the laser-etched circuit.

[0037] (3) Laser processing: According to the set circuit pattern, the PTFE surface in (2) is processed by laser. During laser processing, the synergistic effect of the laser etching effect and the chemical etching effect of the naphthalene treatment solution is utilized to make the laser etched area show good hydrophilic wetting properties, while the unetched area still shows super hydrophobic properties.

[0038] The laser used in step (3) is preferably an ultraviolet laser. The wavelength of the ultraviolet laser is short, the frequency is high, and the corresponding single photon energy is high. In the process of etching PTFE, photochemical action is the main factor. Etching the PTFE surface with this wavelength laser can directly break the chemical bonds in the PTFE structure, thereby generating more active free radicals in the laser etching area. Then, under the synergistic effect of the naphthalene treatment solution, more hydrophilic functional groups can be generated in the laser etching area. Infrared and visible light lasers have longer wavelengths, lower frequencies, and corresponding single photon energy is low. The thermal effect they have in the process of etching PTFE is greater. When they are used as light sources in the process of etching PTFE, fewer active free radicals are generated, which is not conducive to improving the hydrophilic properties of the laser etching area.

[0039] In step (3), the laser-etched area shows good hydrophilicity due to the dual effects of laser etching and the naphthalene solution, while the laser-unetched area still shows hydrophobicity because it is only exposed to the low-concentration naphthalene solution for a short time. That is, the laser-etched area shows good hydrophilicity, while the unetched area shows hydrophobicity.

[0040] The laser used in step (3) is preferably a pulsed laser. Since the etching threshold of the PTFE film material is relatively large, if a continuous laser is used, it is difficult to etch away the PTFE surface material due to its low peak power. However, the peak power of a single pulse of a pulsed laser is high, which can construct a deeper groove structure on the PTFE surface. At the same time, it is also beneficial to improve the hydrophilicity of the laser-etched area, which is also beneficial to improving the bonding strength between the PTFE and the subsequent metal copper plating layer.

[0041] The pulse laser power in step (3) is preferably 4W-12W, the laser scanning rate is preferably 500-1000 mm / s, the scanning interval is preferably 5-40 μm, and the laser pulse frequency is preferably 50 KHz-20 MHz.

[0042] In step (3), the PTFE film should be immersed in the naphthalene solution for no more than 3 minutes. If the immersion time is too long, the area outside the laser-etched circuit pattern will also change from hydrophobic to hydrophilic, and then both the laser-etched circuit pattern area and the area outside the laser-etched circuit pattern will become hydrophilic, which will cause the preparation of the polytetrafluoroethylene flexible conductive circuit to fail. Therefore, the PTFE film should not be immersed in the naphthalene treatment solution for too long.

[0043] (4) Cleaning: Clean the PTFE film after laser processing in (3) to remove the naphthalene treatment liquid attached to the surface of the PTFE film.

[0044] (5) Pre-setting an activator: Pre-setting a solution containing metal ions or metal complex ions on the surface of the PTFE film obtained in step (4). The solution of metal ions or metal complex ions will quickly wet the circuit pattern.

[0045] The solution of metal ions or metal complex ions in step (5) is a solution composed of one or more ions or complex ions of aluminum, copper, zinc, nickel, iron, manganese, molybdenum, gold, ruthenium, tungsten, rhodium, or silver. After laser etching, these metal salts will form active centers that catalyze the chemical plating reaction.

[0046] The concentration of the metal ion or metal complex ion in step (5) is preferably 0.04-2.00 mol / L.

[0047] The following are examples:

[0048] Example 1

[0049] (1) Preparation of sodium naphthalene solution: Accurately measure 1000 ml of tetrahydrofuran and inject it into a designated container. Then, place it in an ice bath for stirring and cooling. Next, add 32 g of refined naphthalene. Continue stirring for 3 minutes. Then, cut 5.8 g of metallic sodium into small pieces and slowly add them to the container in two batches. Continue stirring for 5 hours to obtain a sodium naphthalene treatment solution with a concentration of 0.25 mol / L.

[0050] (2) Placement of PTFE film and injection of sodium naphthalene solution: A PTFE film with an area of ​​50 mm × 50 mm and a thickness of 0.5 mm is laid flat on the bottom of the quartz tank. Its surface is required to be flat. Then, a sodium naphthalene treatment solution with a concentration of 0.25 mol / L is injected into the PTFE surface so that the sodium naphthalene treatment solution surface is 1.00 mm higher than the surface of the PTFE film. Then, a quartz glass sheet with a thickness of 0.6 mm is completely covered on the sodium naphthalene treatment solution to ensure that the upper surface of the PTFE and the lower surface of the quartz glass sheet are completely filled with the sodium naphthalene treatment solution and there is no problem of bubble inclusion.

[0051] Figure 1 This is a schematic diagram of the placement of the PTFE film. It can be seen that the PTFE is placed at the bottom of the quartz tank, in close contact with the bottom of the quartz tank, and the top of the PTFE is covered with the naphthalene treatment liquid. Then, a quartz glass sheet is used to cover the naphthalene treatment liquid. No bubbles can be trapped between the PTFE film and the quartz glass sheet.

[0052] (3) Laser processing: According to the set circuit pattern, a picosecond pulse laser with a wavelength of 355 nm is used, the laser output power is set to 4 W, the scanning speed is 500 mm / s, the pulse frequency is 20 MHz, the laser scanning spacing is 5 μm, and the PTFE film is processed by parallel line scanning.

[0053] In step (2) and step (3), the PTFE film is immersed in the naphthalene solution for 3.0 minutes.

[0054] (4) Cleaning: Use tap water and distilled water to clean the PTFE film processed by laser in (3) for 1 minute each.

[0055] Figure 2 This is a schematic diagram of the preparation method of PTFE flexible conductive circuits. It can be seen that the laser-etched circuit pattern area is hydrophilic, while the area outside the laser-etched circuit pattern is hydrophobic.

[0056] (5) Pre-activating agent: Apply an activation solution containing copper chloride at a concentration of 2.00 mol / L to the surface of the PTFE substrate in (4) by brushing. The activation solution will quickly wet the laser-etched circuit pattern area, while the area outside the laser-etched circuit pattern cannot be wetted due to its superhydrophobicity. After 20 minutes, wash the PTFE film with distilled water and dry it.

[0057] (6) Chemical plating: The PTFE sheet cleaned in step (5) was placed in a chemical plating solution for chemical copper plating. The chemical plating solution was composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol. During the chemical plating, the temperature was controlled at 55°C, the pH value was 12.5, and the chemical plating time was 90 min.

[0058] The bonding strength of the copper layer on the surface of the prepared PTFE film was measured by the solder welding vertical stretching method. The test results showed that the bonding strength of the copper layer on the surface of the PTFE sheet was 4.95 MPa.

[0059] Example 2:

[0060] (1) Preparation of sodium naphthalene treatment solution: Accurately measure 1000 ml of tetrahydrofuran and inject it into a designated container. Then, place it in an ice bath for stirring and cooling. Next, add 6.4 g of refined naphthalene and continue stirring for 5 min. Then, cut 1.15 g of metallic sodium into small pieces and slowly add them to the container in two batches. Continue stirring for 4.0 h to obtain a sodium naphthalene treatment solution with a concentration of 0.05 mol / L.

[0061] (2) Placement of PTFE film and injection of sodium naphthalene treatment solution: A PTFE film with an area of ​​45 mm × 45 mm and a thickness of 0.3 mm is laid flat on the bottom of the quartz tank. Its surface is required to be flat. Then, a sodium naphthalene solution with a concentration of 0.05 mol / L is injected into the PTFE surface so that the sodium naphthalene treatment solution surface is 0.50 mm higher than the surface of the PTFE film. Then, a quartz glass sheet with a thickness of 0.20 mm is completely covered on the sodium naphthalene treatment solution to ensure that the upper surface of the PTFE and the lower surface of the quartz glass sheet are completely filled with the sodium naphthalene treatment solution and there is no problem of bubble inclusion.

[0062] (3) Laser processing: According to the set circuit pattern, a nanosecond pulse laser with a wavelength of 355 nm is used, the laser output power is set to 12 W, the scanning speed is 1000 mm / s, the pulse frequency is 50 kHz, the laser scanning spacing is 40 μm, and the PTFE film is processed using a parallel line scanning method.

[0063] In step (2) and step (3), the PTFE film is immersed in the naphthalene solution for 1.0 min.

[0064] (4) Cleaning: Use tap water and distilled water to clean the PTFE film processed by laser in (3) for 2 minutes each.

[0065] The water static contact angle of the PTFE film was measured, and it was found that the water static contact angle of the laser-etched circuit pattern area was 25.1±0.8°, showing good hydrophilic properties; while the water static contact angle of the area outside the laser-etched circuit pattern was 121±1.5°, showing good hydrophobicity.

[0066] (5) Pre-activating agent: Apply the activation solution containing ZnCl2 at a concentration of 0.04 mol / L to the surface of the PTFE substrate in (4) by brushing. The activation solution will quickly wet the laser-etched circuit pattern area, while the area outside the laser-etched circuit pattern cannot be wetted due to its superhydrophobicity. After 15 minutes, wash the PTFE film with distilled water and dry it.

[0067] (6) Chemical plating: The PTFE sheet cleaned in step (5) was placed in a chemical plating solution for chemical copper plating. The chemical plating solution was composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol. During the chemical plating, the temperature was controlled at 50°C, the pH value was 12.5, and the chemical plating time was 100 min.

[0068] The bonding strength of the copper layer on the surface of the prepared PTFE sheet was measured using the solder welding vertical tensile method. The test results showed that the bonding strength of the copper layer on the surface of the PTFE sheet was 3.96 MPa.

[0069] Example 3

[0070] (1) Preparation of sodium naphthalene treatment solution: Accurately measure 1000 ml of tetrahydrofuran and inject it into a designated container. Then, place it in an ice bath for stirring and cooling. Next, add 25.6 g of refined naphthalene and continue stirring for 5 minutes. Then, cut 4.6 g of metallic sodium into small pieces and slowly add them to the container in two batches. Continue stirring for 5 hours to obtain a sodium naphthalene treatment solution with a concentration of 0.20 mol / L.

[0071] (2) Placement of PTFE film and injection of sodium naphthalene treatment solution: A PTFE film with an area of ​​60 mm × 60 mm and a thickness of 0.8 mm is laid flat on the bottom of the quartz tank. Its surface is required to be flat. Then, the prepared sodium naphthalene treatment solution is injected into the PTFE surface so that the sodium naphthalene treatment solution surface is 0.75 mm higher than the surface of the PTFE film. Then, a quartz glass sheet with a thickness of 0.4 mm is completely covered on the sodium naphthalene treatment solution to ensure that the upper surface of the PTFE and the lower surface of the quartz glass sheet are completely filled with the sodium naphthalene treatment solution and there is no problem of air bubbles being included.

[0072] (3) Laser processing: According to the set circuit pattern, a picosecond pulse laser with a wavelength of 355 nm is used, the laser output power is set to 10 W, the scanning speed is 800 mm / s, the pulse frequency is 200 kHz, the laser scanning spacing is 20 μm, and the PTFE film is processed using a parallel line scanning method.

[0073] In steps (2) and (3), the PTFE film is immersed in the sodium naphthalene solution for 2.0 minutes. However, the time required for modifying PTFE with sodium naphthalene alone is at least 10 minutes. It can be seen that the technology of the present invention can shorten the processing time, thereby improving production efficiency.

[0074] (4) Cleaning: Use tap water and distilled water to clean the PTFE film processed by laser in (3) for 2 minutes each.

[0075] The water static contact angle of the PTFE film was measured, and it was found that the water static contact angle of the laser-etched circuit pattern area was 21.2±0.9°, showing good hydrophilic properties; while the water static contact angle of the area outside the laser-etched circuit pattern was 125±1.4°, showing good hydrophobicity.

[0076] (5) Pre-activating agent: Spray an activation solution containing AgNO3 at a concentration of 0.3 mol / L onto the surface of the PTFE substrate in (4). The activation solution will quickly wet the laser-etched circuit pattern area, while the area outside the laser-etched circuit pattern cannot be wetted due to its super-hydrophobicity. After 15 minutes, wash the PTFE film with distilled water and dry it.

[0077] (6) Chemical plating: The PTFE sheet cleaned in step (5) was placed in a chemical plating solution for chemical copper plating. The chemical plating solution was composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol. During the chemical plating, the temperature was controlled at 50°C, the pH value was 12.5, and the chemical plating time was 120 min.

[0078] The bonding strength of the copper layer on the surface of the prepared PTFE sheet was measured using the solder welding vertical tensile method. The test results showed that the bonding strength of the copper layer on the surface of the PTFE sheet was 5.43 MPa.

[0079] The maximum bonding strength of the copper coating obtained on the PTFE surface after plasma treatment can reach 3.82 Mpa. It can be seen that the technology of the present invention can increase the bonding strength of the PTFE sheet by more than 40%.

[0080] At the same time, in order to compare the effect of the present invention on improving the bonding strength of the copper plating layer on the PTFE surface, the PTFE was first treated with chemical etching using a sodium naphthalene solution (prepared by dissolving 25.6 g of refined naphthalene in 1000 ml of tetrahydrofuran) and then copper-plated. The bonding strength of the copper plating layer was tested, and the results showed that the bonding strength of the copper layer on the PTFE sheet surface was 3.09 MPa.

[0081] It can be seen that the present invention can improve the bonding strength of the PTFE sheet by about 75% through the synergistic effect of the chemical etching effect of the sodium naphthalene treatment solution and the ultraviolet pulse laser etching effect.

Claims

1. A method for preparing a polytetrafluoroethylene flexible conductive circuit, characterized in that: The steps include: (1) Preparation of sodium naphthalene treatment solution: using tetrahydrofuran, refined naphthalene and metallic sodium as raw materials, prepare a sodium naphthalene treatment solution of a certain concentration; (2) Placement of PTFE film and injection of sodium naphthalene treatment solution: Select a PTFE film of a certain thickness and lay it flat on the bottom of the quartz tank. The surface of the film should be flat. Then, inject the appropriate amount of sodium naphthalene treatment solution prepared in (1) onto the surface of the PTFE film. Then, soak the PTFE film in the sodium naphthalene treatment solution and cover the quartz glass sheet on the sodium naphthalene treatment solution. The thickness of the sodium naphthalene treatment solution between the quartz glass sheet and the PTFE film is 0.50-1.00 mm; (3) Laser processing: according to the set circuit pattern, the surface of the PTFE film in (2) is processed by using a laser. During the laser processing, the synergistic effect of the laser etching effect and the chemical etching effect of the naphthalene treatment solution is utilized to make the laser-etched area exhibit good hydrophilic wetting properties, while the laser-unetched area still exhibits hydrophobic properties; the laser is a pulsed laser in the ultraviolet band; (4) Cleaning: Use tap water and distilled water to clean the PTFE film processed in (3); (5) Pre-setting an activator: Pre-setting a solution containing metal ions or metal complex ions on the surface of the PTFE film obtained in step (4). The solution of metal ions or metal complex ions will quickly wet the laser-etched circuit pattern; (6) Chemical plating: The PTFE flexible film treated in step (5) is placed in a chemical plating solution to deposit a metal layer, thereby obtaining a PTFE flexible conductive circuit.

2. The preparation method according to claim 1, wherein The concentration of the sodium naphthalene treatment solution used in step (1) is 0.05-0.25 mol / L.

3. The preparation method according to claim 1, wherein The thickness of the quartz glass sheet in step (2) is 0.2 mm to 0.6 mm.

4. The preparation method according to claim 1, wherein In the step (2), the sodium naphthalene treatment solution between the quartz glass sheet and the PTFE film must not contain any bubbles.

5. The preparation method according to claim 1, wherein The pulse laser power is 4W-12W, the laser scanning rate is 500-1000 mm / s, the scanning interval is 5-40 μm, and the laser pulse frequency is 50KHz-20MHz.

6. The preparation method according to claim 1, wherein In the steps (2) and (3), the PTFE film is immersed in the naphthalene treatment solution for 1-10 minutes.

7. The preparation method according to claim 1, wherein The specific steps of cleaning in step (4) are: placing the laser-processed PTFE film obtained in step (3) in tap water and distilled water for rinsing for 20-300 seconds respectively.

8. The preparation method according to claim 1, wherein The solution of metal ions or metal complex ions in step (5) is a solution composed of one or more ions or complex ions of aluminum, copper, zinc, nickel, iron, manganese, molybdenum, gold, ruthenium, tungsten, rhodium, and silver, and the concentration of the metal ions or metal complex ions is 0.04-2.00 mol / L.

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