PTFE composite high-frequency contour-free electrolytic copper foil and preparation method thereof

Abstract

The invention provides a PTFE composite high-frequency contour-free electrolytic copper foil and a preparation method thereof.The copper foil comprises a copper foil base body, the smooth surface roughness Rz of the copper foil base body is smaller than or equal to 1.5 micrometers, semispherical crystal grains are formed on the rough surface, PTFE nano-particles are embedded in the copper foil, the PTFE mass ratio of the rough surface is higher than that of the smooth surface, gradient distribution is formed, pulse electrodeposition is adopted in the preparation method, and the surface roughness Rz of the smooth surface is smaller than or equal to 1.5 micrometers. According to the low-dielectric-loss copper foil and the preparation process thereof, a PTFE nano-emulsion is added into an electrolyte, PTFE gradient distribution and grain refinement are realized through directional flowing of the electrolyte and current density gradient control, and the copper foil is low in dielectric constant, high in peel strength and suitable for PTFE substrates such as 5G / 6G high-frequency substrates and satellite radars.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil manufacturing technology for high-frequency circuits, and particularly to a PTFE composite high-frequency non-profile electrolytic copper foil and its preparation method. Background Technology

[0002] In high-frequency applications such as 5G communication, millimeter-wave radar, and satellite navigation systems, signal transmission loss has become a core bottleneck restricting equipment performance. As a key conductive material in high-frequency copper-clad laminates, the surface profile characteristics of electrolytic copper foil directly determine electromagnetic wave transmission efficiency. Studies have shown that when the signal frequency exceeds 10 GHz, for every 0.1 μm increase in the surface roughness of the copper foil, the transmission loss will increase significantly by more than 15%.

[0003] Traditional copper foil has a surface roughness of Rz > 2.0 μm, which causes severe skin effect and signal scattering at high frequencies above 10 GHz. This results in high dielectric constant (Dk > 3.5) and loss factor (Df), leading to decreased signal transmission integrity. Consequently, signal attenuation in 5G / millimeter wave devices is aggravated, limiting transmission distance and speed.

[0004] To improve the peel strength between copper foil and substrate resin, traditional processes require mechanical roughening of the rough surface, such as nodulation and etching, but this significantly increases the surface profile (Rz > 3.0 μm), exacerbating high-frequency losses. On the other hand, reducing roughness leads to insufficient peel strength and easy delamination failure, resulting in a dilemma for high-frequency circuits: either poor signal or easy delamination.

[0005] Therefore, it is necessary to develop a PTFE composite high-frequency non-profile electrolytic copper foil to achieve the low dielectric loss, high interfacial bonding and microstructure controllability required for high-frequency applications, and to break through the performance bottleneck of traditional copper foil in high-frequency scenarios. Summary of the Invention

[0006] The purpose of this invention is to provide a PTFE composite high-frequency non-profile electrolytic copper foil and its preparation method, so as to solve the problems of high copper foil surface roughness, low adhesion, and high dielectric constant loss in the existing electrolytic copper foil manufacturing technology mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a PTFE composite high-frequency electrolytic copper foil without profile, comprising a copper foil substrate having a double-sided structure, including a smooth surface and a rough surface, wherein the surface roughness Rz of the smooth surface is ≤1.5μm to suppress signal scattering, and PTFE nanoparticles are uniformly dispersed inside the copper foil substrate, wherein the particle size of the PTFE nanoparticles is 50-200nm, and the mass percentage of the PTFE nanoparticles in the copper foil is 0.1%-1.5%;

[0008] The PTFE nanoparticles have a higher distribution density in the textured area than in the smooth area, forming a concentration gradient structure that decreases from the textured area to the smooth area.

[0009] The microstructure of the rough surface consists of hemispherical grains with a grain size ≤0.8μm, and the gaps between the grains are filled with PTFE nanoparticles. These PTFE nanoparticles are embedded inside the copper foil rather than being a surface coating, thus resolving the contradiction between dielectric properties and bonding strength.

[0010] Preferably, the PTFE nanoparticles on the textured surface account for 0.5%-1.5% of the total mass, while those on the smooth surface account for 0.1%-0.8% of the total mass. The textured surface design, with its hemispherical microcrystals and highly filled PTFE anchoring effect, enhances the bonding strength.

[0011] Preferably, the dielectric constant Dk of the copper foil is ≤3.0 (@10GHz), and the peel strength is ≥0.8kN / m.

[0012] A method for preparing PTFE composite high-frequency non-profile electrolytic copper foil includes electrolyte preparation, electrodeposition process, and post-treatment process. The method is characterized in that: the electrolyte contains 1-5 g / L of PTFE nanoemulsion, and the PTFE nanoemulsion pulse electrodeposition duty cycle is 20%-40%, and the frequency is 100-500 Hz.

[0013] The electrolyte is prepared by adding PTFE nanoemulsion and compound additives to a basic electrolyte. The basic electrolyte is Cu²⁺ 80-100 g / L, H₂SO₄ 90-120 g / L, Cl⁻ 30-80 ppm. The added PTFE nanoemulsion has a particle size of 50-200 nm and a concentration of 1-5 g / L. The compound additives are a grain refiner and a surfactant. The grain refiner is gelatin 0.5-2 mg / L + polyethylene glycol (MW=6000) 10-50 mg / L, and the surfactant is potassium perfluorooctyl sulfonate 0.1-0.5 mg / L.

[0014] The electrodeposition process includes:

[0015] a) Initial deposition was performed using a cathode current density of 30-40 A / dm² for the first 5 minutes;

[0016] b) After 5 minutes, increase the cathode current density to 50-60 A / dm² to complete the subsequent deposition;

[0017] c) Pulse electrodeposition is used throughout the process, with a duty cycle of 20%-40% and a frequency of 100-500Hz;

[0018] d) The electrolyte flows in from the inlet of the rough surface forming zone at a flow rate of 2-5 m / s and flows out from the outlet of the smooth surface forming zone, inducing a PTFE gradient distribution.

[0019] The post-processing involves immersing the electrodeposited workpiece in a benzotriazole (BTA) solution for passivation, forming a protective antioxidant layer on its surface. Then, it is dried at a low temperature of 60-80°C to remove moisture and prevent the PTFE particles in the coating from agglomerating due to excessive temperature, thus locking the PTFE in place and resisting oxidation.

[0020] Preferably, the PTFE nanoemulsion compound dispersant includes 0.1-0.5 mg / L potassium perfluorooctyl sulfonate and 10-30 mg / L polyvinylpyrrolidone.

[0021] Preferably, the electrolyte temperature is 48±2℃, and the PTFE emulsion is ultrasonically treated with 300W for 10 minutes before injection.

[0022] Preferably, the post-treatment includes immersion in a 0.1-0.5 wt% benzotriazole solution for 3-8 seconds.

[0023] Preferably, the electrolyte flow rate is 2-5 m / s, and the PTFE concentration on the rough side is 20%-50% higher than that on the smooth side.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. By designing hemispherical microcrystals with a rough surface and filling them with high-density PTFE particles, the overall contour roughness is significantly reduced while maintaining the micro-anchoring effect of the rough surface. This achieves both low signal loss and high peel strength, solving the problem that high-frequency signal transmission requires ultra-low surface roughness of copper foil to reduce signal loss, but a smooth surface would weaken the adhesion between the copper foil and the substrate resin.

[0026] 2. Through gradient distribution design, the bonding force is enhanced on the rough surface and the low dielectric constant is maintained on the smooth surface; through pulse electrodeposition combined with compound dispersant and ultrasonic pretreatment, the nanoparticles are stably dispersed and precisely positioned and filled, solving the problems of easy agglomeration of PTFE nanoparticles, difficulty in uniform dispersion, and reduction of copper foil conductivity when added in excess.

[0027] 3. By inducing a PTFE concentration gradient through directional electrolyte flow rate; optimizing grain growth through staged current density; and preventing PTFE agglomeration and ensuring antioxidant stability through low-temperature drying and BTA passivation, the problem of simultaneously controlling copper grain morphology and PTFE distribution in electrolytic deposition can be solved by traditional processes. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the copper foil structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the flow direction control in the electrolytic cell of the present invention;

[0030] Figure 3 This is a flowchart of the electrodeposition process of the present invention;

[0031] Figure 4 This is a schematic diagram of the process flow of Embodiment 2 of the present invention;

[0032] Figure 5 This is a graph showing the relationship between PTFE concentration gradient ratio and peel strength in an embodiment of the present invention.

[0033] Figure 6 This is a PTFE gradient distribution diagram of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] A PTFE composite high-frequency electrolytic copper foil without a surface roughness (Rz ≤ 1.5 μm) comprises a copper foil substrate having a double-sided structure, including a smooth surface and a rough surface. PTFE nanoparticles with a particle size of 50-200 nm are uniformly dispersed within the copper foil substrate, and the mass percentage of the PTFE nanoparticles in the copper foil is 0.1%-1.5%. The distribution density of the PTFE nanoparticles is higher on the rough surface than on the smooth surface, forming a concentration gradient from the rough surface to the smooth surface. The structure is reduced; the microstructure of the rough surface is hemispherical grains with a grain size ≤ 0.8 μm, and the intergranular spaces are filled with PTFE nanoparticles. The mass percentage of PTFE nanoparticles in the rough surface is 0.5%-1.5%, and the mass percentage of PTFE nanoparticles in the smooth surface is 0.1%-0.8%. The size of the hemispherical grains is 0.3-0.8 μm, and the PTFE filling rate in the intergranular spaces is ≥ 60%. The dielectric constant Dk of the copper foil is ≤ 3.0 (@10 GHz), and the peel strength is ≥ 0.8 kN / m.

[0036] It is a special copper foil used in high-frequency circuits. The surface of the copper foil itself is made flat and smooth with a roughness of less than 1.5μm, so the signal has low resistance and low loss when running on it.

[0037] During the copper foil manufacturing process, PTFE plastic particles with a diameter of 50-200 nm (D50 distribution) are added to the electrolyte. These particles are then evenly embedded within the copper foil, further reducing energy loss during signal transmission. A special transition layer is created on the side of the copper foil that will be attached to the plastic substrate of the circuit board. This transition layer doesn't abruptly change from copper to plastic; rather, the copper and PTFE particles gradually mix and transition, acting like an adhesive. This ensures a very tight and secure bond between the copper foil and the plastic substrate, preventing delamination and guaranteeing stable operation even under high-frequency signals. This makes this type of copper foil particularly suitable for transmitting high-speed, high-frequency signals.

[0038] Example 1

[0039] Reference Appendix Figure 1-3 Preparation process

[0040] 1. Electrolyte preparation:

[0041] A) Basic component: Cu 2+ 90g / L, H2SO4100g / L, Cl⁻50ppm;

[0042] B) PTFE nanoemulsion: 3g / L (solid content 60wt%, average particle size 100nm, dispersed by 300W ultrasonication for 10min).

[0043] C) Dispersing stabilizer: Potassium perfluorooctyl sulfonate 0.3 mg / L + PVP-K30 20 mg / L;

[0044] D) Grain refiner: 1 mg / L gelatin + 30 mg / L polyethylene glycol (MW=6000).

[0045] 2. Electrodeposition:

[0046] A) Equipment: Titanium cathode roller (diameter 1.5m), electrolytic cell volume 2000L;

[0047] B) Pulse parameters: duty cycle 30%, frequency 200Hz;

[0048] C) Current density gradient:

[0049] a) 0-5 min: 35 A / dm² (to promote PTFE adsorption);

[0050] b) 5-30 min: 55 A / dm² (grain refinement);

[0051] D) Electrolyte flow direction: The inlet is located at 15° to the rough side of the axial center line of the cathode roller, and the outlet is located on the smooth side, with a flow velocity of 3.5m / s;

[0052] E) Temperature: 50±1℃, deposition time: 30min;

[0053] 3. Post-processing:

[0054] A) Passivation: Immerse in 0.3wt% benzotriazole (BTA) solution for 5 seconds;

[0055] B) Drying: Preheat at 60℃ for 1 min → Dry at 80℃ for 2 min.

[0056] The product performance test results are shown in the table below:

[0057] This embodiment achieves the following through innovative techniques: nano-PTFE gradient filling, pulsed electrodeposition process, and composite additive system:

[0058] ① High-frequency loss is reduced by 40%, meeting the needs of 10GHz+ scenarios;

[0059] ② Peel strength is increased by 25%, solving the delamination problem under high PTFE filling;

[0060] ③2000L-level mass production stability, yield rate breaks through industry bottlenecks.

[0061] Example 2

[0062] Reference Appendix Figure 1-4 ,

[0063] 1. Preparation process

[0064] A) Electrolyte preparation:

[0065] B) PTFE nanoemulsion: 2 g / L (particle size 150 nm);

[0066] C) Dispersing stabilizer: Potassium perfluorooctane sulfonate 0.2 mg / L + PVP-K30 15 mg / L;

[0067] D) Grain refiner: 1 mg / L gelatin + 30 mg / L polyethylene glycol (MW=6000).

[0068] 2. Electrodeposition:

[0069] A) Pulse parameters: duty cycle 35%, frequency 300Hz

[0070] B) Current density gradient:

[0071] a) 0-5min: 30A / dm²

[0072] b) 5-25 min: 50 A / dm²

[0073] C) Electrolyte flow rate: 2.8 m / s, temperature 49℃.

[0074] 3. Post-processing:

[0075] A) Passivation: Immerse in 0.3wt% benzotriazole (BTA) solution for 5 seconds;

[0076] B) Drying: Preheat at 60℃ for 1 min → Dry at 80℃ for 2 min.

[0077] The product performance test results are shown in the table below:

[0078] This embodiment achieves the following through precise control of PTFE concentration (2g / L) and optimization of high-frequency pulses (300Hz):

[0079] ① High-frequency loss is reduced by 40% compared to traditional copper foil, meeting the needs of 5G consumer electronics;

[0080] ② The gradient ratio was increased to 2.02, breaking through the binding force bottleneck of the medium concentration scheme;

[0081] ③ The overall cost decreased by 18% and the yield rate reached 99.2%, solving the industry problem of "cost reduction inevitably leads to performance loss".

[0082] Core value: Providing cost-effective high-frequency copper foil solutions for smartphones, wearable devices, and IoT modules, bridging the technological gap between consumer-grade high-frequency hardware and cost constraints.

[0083] Core value: Providing copper foil solutions for high-frequency and high-speed PCBs that combine ultra-low Dk, high reliability, and mass production feasibility, driving the hardware upgrade of 6G communication and AI computing power.

[0084] Comparative Example

[0085] Reference Appendix Figure 1-6 Process adjustment: Eliminate current gradient and directional flow field

[0086] Performance degradation:

[0087] a) Peel strength: 0.68 kN / m

[0088] b) High-frequency loss: -0.33dB / cm

[0089] The comparison data is shown in the table below:

[0090] High-frequency performance comparison

[0091] Reference Appendix Figure 6The ultra-low roughness of the smooth surface (Rz=1.2μm) can also suppress skin effect scattering and solve the physical limitations of high-frequency signal transmission, such as the skin effect: the skin depth of a 10GHz signal in copper foil is only 0.66μm, and the surface roughness (Rz) needs to be ≤1.5μm.

[0092] Reference Appendix Figure 5 This invention discloses a PTFE composite high-frequency non-profile electrolytic copper foil. The high gradient ratio causes the rough surface to form a PTFE-rich network, generating a "pseudo-alloy effect" at the copper-resin interface, which improves the bonding strength without increasing the macroscopic roughness. The key role of the gradient ratio is to meet the requirements of high-frequency PCBs that need to withstand thermal cycling stress and have a peel strength of 0.8~1.0kN / m.

[0093] The two embodiments and comparative examples together demonstrate:

[0094] Gradient control technology (current timing + directional flow field) is the core to break through the performance bottleneck of PTFE copper foil, achieving a peel strength improvement of 26%~37%, completely solving the delamination risk of high / medium PTFE filling; reducing high frequency loss by 36%~48%, filling the gap in domestic high frequency copper foil technology; and achieving a stable gradient ratio >1.95, solving the problem of inverted concentration and performance, providing cost-controllable high frequency copper foil for consumer electronics, and accelerating the popularization of 5G terminals.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PTFE composite high-frequency non-profile electrolytic copper foil, characterized in that: The invention includes a copper foil substrate having a double-sided structure, comprising a smooth surface and a rough surface, wherein the surface roughness Rz of the smooth surface is ≤1.5μm, and PTFE nanoparticles are uniformly dispersed within the copper foil substrate, wherein the particle size of the PTFE nanoparticles is 50-200nm, and the mass percentage of the PTFE nanoparticles in the copper foil is 0.1%-1.5%. The PTFE nanoparticles have a higher distribution density in the textured area than in the smooth area, forming a concentration gradient structure that decreases from the textured area to the smooth area. The microstructure of the textured surface consists of hemispherical grains with a grain size ≤0.8μm, and the intergranular spaces are filled with PTFE nanoparticles.

2. The PTFE composite high-frequency non-profile electrolytic copper foil according to claim 1, characterized in that: The PTFE nanoparticles on the textured surface account for 0.5%-1.5% of the total mass, while those on the smooth surface account for 0.1%-0.8% of the total mass.

3. The PTFE composite high-frequency non-profile electrolytic copper foil according to claim 1, characterized in that: The size of the hemispherical grains is 0.3-0.8 μm, and the PTFE filling rate of the grain gaps is ≥60%.

4. The PTFE composite high-frequency non-profile electrolytic copper foil according to claim 1, characterized in that: The dielectric constant of the copper foil is Dk≤3.0 (@10GHz), and the peel strength is ≥0.8kN / m.

5. A method for preparing PTFE composite high-frequency non-profile electrolytic copper foil as described in claim 1, comprising electrolyte preparation, electrodeposition process, and post-treatment process, characterized in that: The electrolyte contains 1-5 g / L of PTFE nanoemulsion, and the PTFE nanoemulsion pulse electrodeposition duty cycle is 20%-40% with a frequency of 100-500 Hz. The electrolyte is prepared by adding PTFE nanoemulsion and compound additives to a basic electrolyte. The basic electrolyte is Cu²⁺ 80-100 g / L, H₂SO₄ 90-120 g / L, Cl⁻ 30-80 ppm. The added PTFE nanoemulsion has a particle size of 50-200 nm and a concentration of 1-5 g / L. The compound additives are a grain refiner and a surfactant. The grain refiner is gelatin 0.5-2 mg / L + polyethylene glycol (MW=6000) 10-50 mg / L, and the surfactant is potassium perfluorooctyl sulfonate 0.1-0.5 mg / L. The electrodeposition process includes: a) Initial deposition was performed using a cathode current density of 30-40 A / dm² for the first 5 minutes; b) After 5 minutes, increase the cathode current density to 50-60 A / dm² to complete the subsequent deposition; c) Pulse electrodeposition is used throughout the process, with a duty cycle of 20%-40% and a frequency of 100-500Hz; d) The electrolyte flows in from the inlet of the rough surface forming zone at a flow rate of 2-5 m / s and flows out from the outlet of the smooth surface forming zone; The post-processing involves immersing the electrodeposited workpiece in a benzotriazole (BTA) solution for passivation, forming a protective antioxidant layer on its surface. Then, it is dried at a low temperature of 60-80°C to remove moisture and prevent the PTFE particles in the coating from agglomerating due to excessive temperature.

6. The method for preparing a PTFE composite high-frequency non-profile electrolytic copper foil according to claim 5, characterized in that: The PTFE nanoemulsion compound dispersant includes potassium perfluorooctane sulfonate 0.1-0.5 mg / L and polyvinylpyrrolidone 10-30 mg / L.

7. The method for preparing a PTFE composite high-frequency non-profile electrolytic copper foil according to claim 5, characterized in that: The electrolyte temperature is 48±2℃, and the PTFE emulsion is ultrasonically treated at 300W for 10 minutes before injection.

8. The method for preparing a PTFE composite high-frequency non-profile electrolytic copper foil according to claim 5, characterized in that: The post-treatment includes immersion in a 0.1-0.5 wt% benzotriazole solution for 3-8 seconds.

9. The method for preparing a PTFE composite high-frequency non-profile electrolytic copper foil according to claim 5, characterized in that: The electrolyte flow rate is 2-5 m / s, and the PTFE concentration on the rough side is 20%-50% higher than that on the smooth side.

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