Copper foil with low transmission loss and high peel strength and preparation method thereof

Abstract

The invention relates to the technical field of electronic circuit materials, in particular to a copper foil with low transmission loss and high peel strength and a preparation method thereof. The copper foil comprises a copper foil body, and an insulating layer, a middle layer, a passivation layer, a coarsening layer and a curing layer which are sequentially laminated on the surface of the copper foil body. The insulating layer is a titanium-containing oxide layer, and the adhesion amount of titanium is 100-200mg / m < 2 >; the middle layer is a conductive metal layer formed by vacuum sputtering; the resistivity of the passivation layer is 7 * 10 <-4 > to 1.6 * 10 <-3 > omega.cm; the surface of the coarsening layer is provided with nanoparticles, and the lightness L * value of the coarsening layer is smaller than or equal to 65. Transmission of high-frequency current in the copper foil body is limited through cooperation of the insulating layer and the passivation layer, and the skin effect is inhibited; meanwhile, strong mechanical anchoring is formed by the coarsening layer nanostructure and the resin, and the structure is stabilized by the curing layer, so that low transmission loss and high peel strength are both considered, and the composite material is particularly suitable for a high-frequency and high-speed printed circuit board.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit materials technology, and in particular to a copper foil with low transmission loss and high peel strength, and a method for preparing the same. Background Technology

[0002] With the rapid development of communication technology, high-frequency and high-speed functions place higher demands on printed circuit board (PCB) materials for low loss, high frequency and high reliability. Among them, electrolytic copper foil, as the conductor material of PCB substrate, plays a decisive role in the integrity of signal transmission.

[0003] When signals travel through high-speed circuits, they tend to concentrate on the surface layer of the copper foil for transmission; this phenomenon is known as the "skin effect." The skin effect causes current signals to flow closer to the conductor's surface. If the copper foil surface roughness is high, the path the current must take is correspondingly longer, leading to higher conductor losses and severely impairing signal transmission integrity. Therefore, to mitigate the adverse effects of the skin effect on signal quality, the surface roughness of electrolytic copper foil needs to reach unprecedented levels to meet the stringent requirements of high-frequency, high-speed PCBs for signal transmission. Consequently, more and more high-frequency, high-speed PCB substrates are using low-roughness RTF copper foil, VLP copper foil, or HVLP copper foil. Simultaneously, to improve the reliability of the PCB substrate, it is necessary to roughen the bonding surface between the copper foil and the substrate to ensure adhesion, while also considering the impact of this roughening on signal transmission attenuation, striving to maintain the overall stability of the PCB while meeting the demands of high-performance signal transmission.

[0004] Chinese invention patent CN114318429B discloses a nano-roughening electrolyte, method, and product for ultra-low profile electrolytic copper foil. The nano-roughening electrolyte includes an electrolyte and additives. The electrolyte is an aqueous solution of copper sulfate and sulfuric acid. The additives are natural polysaccharides, specifically one or more of fenugreek gum, guar gum, carob gum, and carrageenan. The patent also discloses a nano-roughening method for ultra-low profile electrolytic copper foil, comprising the following steps: Step 1, heating the electrolyte and injecting it into a roughening electrolytic cell to prepare a raw foil; Step 2, after acid washing, the raw foil is placed into the roughening electrolytic cell for electrodeposition to prepare nano-copper nodules; Step 3, curing and oxygen-proofing treatment to obtain the target copper foil. This copper foil has low roughness and high peel strength, making it suitable for use as a high-frequency, high-speed electrolytic copper foil.

[0005] Despite significant advancements in existing technologies, the concepts remain limited to optimizing surface roughness, leading to increasingly complex processes. Obtaining a uniform rough surface at the nanoscale requires substantial investment in surface treatment processes, directly increasing the manufacturing cost of copper foil. More importantly, this passive adaptation to the skin effect mode is gradually approaching its physical limits in terms of performance improvement.

[0006] There is an urgent need in this field to develop a method that enables copper foil to minimize signal transmission loss caused by the skin effect, even when it has a surface structure for enhancing adhesion, without sacrificing or compromising between signal integrity and peel strength. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the present invention provides a copper foil with low transmission loss and high peel strength and a method for preparing the same, so as to solve the technical problem of how to minimize the signal transmission loss caused by the skin effect while taking into account the high peel strength between the copper foil and the substrate.

[0008] The first aspect of this invention provides a copper foil with low transmission loss and high peel strength, comprising a copper foil body and a surface treatment layer. The surface treatment layer includes an insulating layer, an intermediate layer, a passivation layer, a roughening layer, and a curing layer sequentially stacked on the surface of the copper foil body. The insulating layer is a titanium-containing oxide layer, and the amount of titanium element attached is 100~200 mg / m³. 2 The intermediate layer is a conductive metal layer formed by vacuum sputtering; the resistivity of the passivation layer is 7 × 10⁻⁶. -4 ~1.6×10 -3 Ω·cm; Nanoparticles are formed on the surface of the roughened layer, and the lightness L* value of the roughened layer is ≤65.

[0009] In some embodiments of the present invention, the intermediate layer comprises one or more of nickel, cobalt, chromium, titanium, manganese, zinc, tungsten, and tin.

[0010] In some embodiments of the present invention, the amount of metal element attached to the intermediate layer is 100~500 mg / m³. 2 Preferably 200~350 mg / m 2 .

[0011] In some embodiments of the present invention, the passivation layer is a nickel-phosphorus based alloy layer.

[0012] In some embodiments of the present invention, the thickness of the passivation layer is 0.05~0.2μm.

[0013] In some embodiments of the present invention, the resistivity of the passivation layer is 8.5 × 10⁻⁶. -4 ~1.55×10 -3 Ω·cm.

[0014] In some embodiments of the present invention, the roughening layer contains three elements: nickel, molybdenum, and phosphorus.

[0015] In some embodiments of the present invention, the diameter of the nanoparticles is 60-250 nm, and the center-to-center distance between adjacent nanoparticles is 50-300 nm.

[0016] In some embodiments of the present invention, the cured layer comprises nickel and phosphorus.

[0017] In some embodiments of the present invention, the thickness of the cured layer is 5~30nm.

[0018] In some embodiments of the present invention, the surface treatment layer further includes a rust-preventive layer disposed on the surface of the cured layer.

[0019] In some embodiments of the present invention, at least one surface of the copper foil body is provided with a surface treatment layer.

[0020] A second aspect of the present invention provides a method for preparing the aforementioned copper foil with low transmission loss and high peel strength, comprising the following steps:

[0021] (1) Provide the copper foil body and clean its surface;

[0022] (2) A titanium-containing oxide insulating layer is formed on the surface of the copper foil body;

[0023] (3) The intermediate layer is formed on the surface of the insulating layer by vacuum sputtering;

[0024] (4) The passivation layer is formed on the surface of the intermediate layer by electroplating;

[0025] (5) The roughening layer is formed on the surface of the passivation layer by electrochemical roughening;

[0026] (6) The cured layer is formed on the surface of the roughened layer by electroplating.

[0027] In some embodiments of the present invention, in step (1), the maximum height Rz of the contact surface between the copper foil body and the insulating layer is 2.5 μm to 4.5 μm; and the interface expansion area ratio Sdr of the contact surface between the copper foil body and the insulating layer is 5% to 10%.

[0028] In some embodiments of the present invention, in step (1), the cleaning is performed using an acidic cleaning solution.

[0029] In some embodiments of the present invention, in step (2), the titanium-containing oxide insulating layer is prepared by sol-gel method, and the preparation process includes three stages in sequence: sol preparation, coating film formation and heat treatment conversion.

[0030] In some embodiments of the present invention, in step (3), the background vacuum level of the vacuum sputtering is not higher than 8 × 10⁻⁶. - 3 Pa.

[0031] In some embodiments of the present invention, in step (3), argon is used as the working gas for vacuum sputtering, and the gas flow rate is 100~400 sccm, preferably 150~250 sccm. Preferably, the purity of the argon is 99.99%.

[0032] In some embodiments of the present invention, in step (3), the power of the vacuum sputtering is 5~15kW.

[0033] In some embodiments of the present invention, in step (3), the target material used for vacuum sputtering includes one or more of nickel, chromium, tin, tungsten or cobalt.

[0034] In some embodiments of the present invention, in step (3), during the vacuum sputtering process, the copper foil substrate is supported by a cooling roller and its temperature is controlled.

[0035] In some embodiments of the present invention, in step (4), the electrolyte used for electroplating includes nickel ions with a concentration of 14-25 g / L, hypophosphite ions with a concentration of 15-35 g / L, molybdate ions with a concentration of 16-35 g / L, or tungstate ions with a concentration of 17-35 g / L.

[0036] In some embodiments of the present invention, in step (4), the electrolyte used for electroplating further includes a complexing agent and a buffer. The complexing agent is selected from sodium citrate or potassium citrate, and its concentration is 60~140 g / L. The buffer is selected from one or two of ammonium sulfate or boric acid, preferably including ammonium sulfate with a concentration of 20~50 g / L and boric acid with a concentration of 20~40 g / L.

[0037] In some embodiments of the present invention, in step (4), the electroplating process conditions are: electrolyte temperature of 50~70℃, pH of 5.5~8.0, and current density of 3~7A / dm³. 2 .

[0038] In some embodiments of the present invention, in step (5), electrochemical roughening is performed by electroplating. The electrolyte used for electrochemical roughening includes nickel ions with a concentration of 8-17 g / L, hypophosphite ions with a concentration of 9-23 g / L, and molybdate ions with a concentration of 10-30 g / L.

[0039] In some embodiments of the present invention, in step (5), the electrolyte used for electrochemical roughening further includes a buffer and a complexing agent.

[0040] In some embodiments of the present invention, in step (5), the electrochemical roughening process conditions are: electrolyte temperature 55~65℃, pH value 7.5~8.5, and current density 6~10 A / dm³. 2 Processing time is 8-20 seconds.

[0041] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating includes nickel ions with a concentration of 20-25 g / L and phosphorous acid with a concentration of 10-20 g / L.

[0042] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating further includes boric acid with a concentration of 30-50 g / L and phosphoric acid with a concentration of 25-35 g / L.

[0043] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating further includes sodium saccharin with a concentration of 0.08~0.12 g / L and sodium dodecyl sulfate with a concentration of 0.01~0.03 g / L.

[0044] In some embodiments of the present invention, in step (6), the electroplating process conditions are: electrolyte temperature 55~65℃, pH value 1.0~2.0, and current density 1~3 A / dm³. 2 Processing time is 10-20 seconds.

[0045] In some embodiments of the present invention, a step of forming a rust-preventive layer on the surface of the cured layer is also included.

[0046] In some embodiments of the present invention, steps (1) to (6) are applied to only one surface of the copper foil body or steps (1) to (6) are applied to both surfaces simultaneously.

[0047] A third aspect of the present invention provides a printed circuit board comprising the aforementioned copper foil with low transmission loss and high peel strength.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] 1. This invention constructs a multi-layer functional structure on the copper foil body, consisting of an insulating layer, an intermediate layer, a passivation layer, a roughening layer, and a curing layer. Through the synergistic effect of each layer, it solves the technical problem of balancing low transmission loss and high peel strength in high-frequency and high-speed applications.

[0050] 2. Regarding the reduction of transmission loss, the insulating layer and the passivation layer with a specific resistivity range form a double barrier, which can effectively confine the high-frequency current to the low-loss copper foil body, fundamentally avoiding the signal degradation caused by the skin effect on the rough surface. At the same time, the micro-nano structure composed of nanoparticles of a specific size (60-250nm) in the roughening layer minimizes the additional increase in the signal transmission path, thereby making the insertion loss of the copper foil of this invention (as low as -0.752 dB / inch@16GHz) significantly better than that of traditional roughened copper foil.

[0051] 3. Regarding improved peel strength, the precisely controlled size, spacing, and coverage of the nanoparticles in the roughening layer create a strong micro-mechanical interlocking effect with the resin substrate, resulting in a peel strength exceeding 0.62 N / mm. The overlying curing layer effectively enhances the stability and durability of this nanostructure, ensuring its integrity during subsequent demanding PCB manufacturing processes and ultimately guaranteeing the long-term reliability of electronic products. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the structure of a copper foil with low transmission loss and high peel strength according to an embodiment of the present invention.

[0053] Figure 2 This is a process flow diagram for preparing a copper foil with low transmission loss and high peel strength according to an embodiment of the present invention. Detailed Implementation

[0054] The following specific embodiments further illustrate the present invention of a copper foil with low transmission loss and high peel strength, and its preparation method.

[0055] The first aspect of this invention provides a copper foil with low transmission loss and high peel strength, as referenced. Figure 1 The product includes a copper foil body and a surface treatment layer. The surface treatment layer comprises an insulating layer, an intermediate layer, a passivation layer, a roughening layer, and a curing layer sequentially stacked on the surface of the copper foil body. The insulating layer is a titanium-containing oxide layer, and the amount of titanium element attached is 100~200 mg / m³. 2 The intermediate layer is a conductive metal layer formed by vacuum sputtering; the resistivity of the passivation layer is 7 × 10⁻⁶. -4 ~1.6×10 -3 Ω·cm; Nanoparticles are formed on the surface of the roughened layer, and the lightness L* value of the roughened layer is ≤65.

[0056] This invention successfully confines high-frequency signal transmission within a low-loss copper foil body through the synergistic effect of its various layers. Simultaneously, it achieves strong anchoring with the resin substrate using a nanoscale roughening structure, fundamentally resolving the technical contradiction of traditional copper foil's inability to simultaneously achieve low transmission loss and high peel strength. Specifically, the insulating layer and the passivation layer with a specific resistivity range together form an electromagnetic barrier, effectively suppressing the skin effect. Meanwhile, the precisely controllable size and spacing of the nanoparticles provide a large specific surface area to enhance adhesion, while their tiny size minimizes the increase in signal transmission path, reducing signal degradation caused by surface roughening to the greatest extent. The curing layer ensures the stability of the roughened structure, maintaining its excellent performance during subsequent processing.

[0057] In some embodiments of the present invention, the intermediate layer comprises one or more of nickel, cobalt, chromium, titanium, manganese, zinc, tungsten, and tin. These metals possess good electrical conductivity and interfacial adhesion with the insulating layer and passivation layer. Preferably, the intermediate layer comprises one or more of nickel, chromium, cobalt, tungsten, and tin, with nickel and chromium being preferred due to their excellent overall performance. This intermediate layer, formed by vacuum sputtering, not only provides a continuous conductive path, but its specific crystal structure also helps induce the formation of an ideal microstructure in the subsequent passivation layer.

[0058] In some embodiments of the present invention, the amount of metal element attached to the intermediate layer is 100~500 mg / m³. 2 Preferably 200~350 mg / m 2 This range was determined through extensive experimental verification: when the adhesion concentration is below 100 mg / m³ 2 When the adhesion amount is higher than 500 mg / m³, the intermediate layer may be discontinuous, resulting in insufficient conductivity and affecting subsequent electroplating. 2 At high frequencies (as in Comparative Example 4), an excessively thick intermediate layer may generate significant eddy current effects, increasing insertion loss. This occurs at concentrations of 200–350 mg / m³. 2 Within the preferred range, it can ensure good conductivity and bonding strength while keeping high-frequency loss to a minimum.

[0059] In some embodiments of the present invention, the passivation layer is a nickel-phosphorus based alloy layer. Preferably, the nickel-phosphorus based alloy layer also contains at least one element selected from molybdenum and tungsten. This alloy layer typically exists in an amorphous or microcrystalline state, exhibiting excellent uniformity and corrosion resistance. More importantly, by adjusting the phosphorus content and adding specific elements, its resistivity can be precisely controlled within the desired range.

[0060] In some embodiments of the present invention, the thickness of the passivation layer is 0.05~0.2μm. This thickness range can form a complete cover layer, ensuring its resistance regulation function, while avoiding the increased brittleness and cost caused by excessive thickness.

[0061] In this invention, the resistivity of the passivation layer is 7 × 10⁻⁶. -4 ~1.6×10 -3 Ω·cm. This optimized resistivity range is crucial for subsequent coarsening effects. Excessively high resistivity (such as 17.1 × 10⁻⁶ in Comparative Example 5) is detrimental. -4 (Ω·cm) will inhibit the efficiency of the current during the coarsening process, resulting in insufficient growth of coarsened particles; excessively low resistivity (such as 4.5×10 in Comparative Example 6) will also hinder the growth of coarsened particles. -4 A current distribution of Ω·cm would be too uniform, weakening the coarsening driving force, both of which would lead to a decrease in peel strength. Preferably, at 8.5 × 10⁻⁶ Ω·cm...-4 ~1.55×10 -3 The effect is best within the Ω·cm range.

[0062] In some embodiments of the present invention, the roughening layer comprises nickel, molybdenum, and phosphorus. The introduction of molybdenum significantly improves the electrochemical properties of the nickel-phosphorus alloy, enabling the formation of uniformly sized and regularly distributed nanoparticle structures during the roughening process. This specific elemental combination is key to achieving the ideal roughening morphology. Preferably, the lightness L* value of the roughening layer is 30~65, and can be 30~35, 35~40, 40~45, 45~50, 50~55, or 55~60.

[0063] In some embodiments of the present invention, the nanoparticles have a diameter of 60-250 nm and a center-to-center spacing of 50-300 nm between adjacent nanoparticles. This precisely controlled microstructure creates optimal "anchor" density and size: sufficient particle size and appropriate spacing provide a large specific surface area to achieve high peel strength (e.g., 0.62 N / mm in Example 1) while avoiding performance degradation due to overly dense or sparse structures. Preferably, in the roughened layer, the projected area coverage of the nanoparticles, viewed from a planar perspective, is 60% or more, for example, 60%-65%, 65%-70%, 70%-75%, 75%-80%, etc.

[0064] In some embodiments of the present invention, the cured layer comprises nickel and phosphorus. This alloy layer is formed by electroplating, and its dense structure effectively encapsulates and fixes the underlying coarsened nanoparticles, preventing them from detaching or deforming during subsequent processing, thereby maintaining long-lasting adhesion.

[0065] In this invention, the thickness of the cured layer is 5-30 nm. This thickness range is carefully designed; if it is too thin (<5 nm), the curing effect will be insufficient, and if it is too thick (>30 nm), it may overfill the gaps between the roughened layers, thereby weakening the mechanical interlocking effect. Preferably, the effect is best within the range of 15-28 nm.

[0066] In some embodiments of the present invention, the surface treatment layer further includes a rust-preventive layer disposed on the surface of the cured layer. The rust-preventive layer is selected from at least one of a chromate layer or a silane layer, and can be a conventional chromate layer (as in Example 1) or an environmentally friendly silane layer (as in Example 2). Both can provide reliable anti-oxidation protection for the copper foil and ensure the stability of the product during storage and transportation.

[0067] In some embodiments of the invention, at least one surface of the copper foil body is provided with a surface treatment layer. This design provides manufacturing flexibility, allowing for the production of single-sided treated copper foil for specific applications or double-sided treated copper foil to meet a wider range of needs, reflecting the adaptability and economy of the process of the invention.

[0068] A second aspect of the present invention provides a method for preparing the aforementioned copper foil with low transmission loss and high peel strength, as described above. Figure 2 This includes the following steps:

[0069] (1) Provide the copper foil body and clean its surface;

[0070] (2) The insulating layer is formed on the surface of the copper foil body by the sol-gel method;

[0071] (3) The intermediate layer is formed on the surface of the insulating layer by vacuum sputtering;

[0072] (4) The passivation layer is formed on the surface of the intermediate layer by electroplating;

[0073] (5) The roughening layer is formed on the surface of the passivation layer by electrochemical roughening;

[0074] (6) The cured layer is formed on the surface of the roughened layer by electroplating.

[0075] In some embodiments of the present invention, in step (1), the maximum height Rz of the contact surface between the copper foil body and the insulating layer is 2.5 μm to 4.5 μm; the interface expansion area ratio Sdr of the contact surface between the copper foil body and the insulating layer is 5% to 10%. In the present invention, the copper foil body can be electrolytic copper foil or rolled copper foil, and the thickness of the copper foil body is 9 to 35 μm.

[0076] In some embodiments of the present invention, in step (1), the cleaning is performed using an acidic cleaning solution; preferably, the acidic cleaning solution is selected from one or more of sulfuric acid solution, hydrochloric acid solution, or nitric acid solution, more preferably sulfuric acid solution. The mass fraction of the sulfuric acid solution is preferably 10%~20%, more preferably 12%~18%. The cleaning process is usually carried out at room temperature (e.g., 15~40°C), and the processing time is usually controlled within 20~60 seconds depending on the cleaning method (spraying or immersion) and the state of the copper foil. After cleaning with the acidic cleaning solution, it is rinsed thoroughly with pure water.

[0077] In some embodiments of the present invention, in step (2), the titanium-containing oxide insulating layer is prepared by sol-gel method, and the preparation process includes three stages in sequence: sol preparation, coating film formation and heat treatment conversion.

[0078] In some embodiments of the present invention, the sol preparation includes the following steps: a) adding a titanium source to pure water to prepare a solution, then stirring and sonicating at 30-50°C to obtain a white suspension. b) adding urea to the suspension, raising the solution temperature to 80-100°C, and stirring at a constant temperature until the solution becomes transparent. c) aging the obtained transparent solution to obtain a titanium-containing sol.

[0079] In some embodiments of the present invention, in step (a), the titanium source is selected from titanium oxysulfate, tetrabutyl titanate, or titanium tetrachloride. These titanium sources can all undergo hydrolysis in aqueous solution to generate active titanium-containing species, which then form a Ti-O-Ti network structure through condensation. Titanium oxysulfate is preferred due to its good water solubility, moderate hydrolysis rate, low cost, and ease of obtaining high-purity products. Tetrabutyl titanate is commonly used in non-aqueous systems and is suitable for special processes sensitive to moisture. Titanium tetrachloride has high reactivity, but its release of hydrogen chloride requires strictly controlled ventilation conditions.

[0080] In some embodiments of the present invention, in step (a), the concentration of the titanium source in the preparation system is 3-10 g / L, preferably 5-8 g / L. A concentration below 3 g / L makes it difficult to form a continuous and complete capping layer, resulting in an excessively thin insulating layer and preventing the titanium adhesion from reaching the minimum requirement of 100 mg / m³. 2 Insufficient insulation performance; concentration above 10 g / L: increased sol viscosity, decreased stability, easy to rapid gelation or particle agglomeration, resulting in uneven coating and the formation of a thick, uneven, and easily cracked film layer.

[0081] In some embodiments of the present invention, in step (b), the concentration of urea in the preparation system is 3-8 g / L; under heating conditions (e.g., 90°C), urea slowly decomposes to generate OH. - The ions provide a uniform and mild alkaline environment for the hydrolysis of the titanium source. This avoids violent precipitation caused by excessively high local pH, thus ensuring the uniform nucleation and growth of nanoscale TiO2·xH2O particles. By controlling the reaction kinetics, a transparent sol is ultimately formed instead of a white suspension (as described in Example 1), indicating that the particle size reaches the nanoscale and is uniformly distributed, which is a prerequisite for obtaining a dense, defect-free insulating layer.

[0082] In some embodiments of the present invention, in step (c), the aging temperature is 60~95℃, which can be 60~65℃, 65~70℃, 70~75℃, 75~80℃, 80~85℃, 85~90℃, or 90~95℃, and the time is 0.5~3h, which can be 0.5~1h, 1~1.5h, 1.5~2h, 2~2.5h, or 2.5~3h; then the sol is coated onto the surface of the copper foil body, and then heat treatment is performed at a temperature of 80~120℃ for a time of 0.5~3h.

[0083] The coating process involves applying the prepared titanium-containing sol to the surface of the copper foil. Roller coating is preferred to ensure the formation of a uniform wet film.

[0084] The sol-gel method forms a sol, which is then coated onto the surface of the copper foil substrate. Following this, a heat treatment is performed at a temperature of 80–120°C (or 80–90°C, 90–100°C, 100–110°C, or 110–120°C) for a duration of 0.5–3 hours (or 0.5–1 hour, 1–1.5 hours, 1.5–2 hours, 2–2.5 hours, or 2.5–3 hours). This process aims to remove physically adsorbed water and promote the condensation reaction between Ti-OH groups to form strong Ti-O-Ti bonds, thereby achieving a complete transformation from a gel to a robust titanium oxide insulating layer.

[0085] In some embodiments of the present invention, in step (3), the ion source for vacuum sputtering includes a Hall ion source, a Kaufman ion source, a pulsed bias ion source, etc.

[0086] In some embodiments of the present invention, in step (3), the background vacuum level of the vacuum sputtering is not higher than 8 × 10⁻⁶. - 3 Pa.

[0087] In some embodiments of the present invention, in step (3), argon is used as the working gas for vacuum sputtering, with a gas flow rate of 100-400 sccm, preferably 150-250 sccm. Preferably, the purity of the argon is 99.99%.

[0088] In some embodiments of the present invention, in step (3), the power of the vacuum sputtering is 5~15kW.

[0089] In some embodiments of the present invention, in step (3), the target material used for vacuum sputtering includes one or more of nickel, chromium, tin, tungsten or cobalt.

[0090] In some embodiments of the present invention, in step (3), during the vacuum sputtering process, the copper foil substrate is supported by a cooling roller and its temperature is controlled.

[0091] In some embodiments of the present invention, in step (4), the electrolyte used for electroplating includes nickel ions at a concentration of 14-25 g / L, hypophosphite ions at a concentration of 15-35 g / L, molybdate ions at a concentration of 16-35 g / L, or tungstate ions at a concentration of 17-35 g / L. The nickel ions are derived from nickel sulfate or nickel chloride, the hypophosphite ions are derived from sodium hypophosphite or potassium hypophosphite, the molybdate ions are derived from sodium molybdate, and the tungstate ions are derived from sodium tungstate.

[0092] In some embodiments of the present invention, in step (4), the electrolyte used for electroplating further includes a complexing agent and a buffer. The complexing agent is selected from sodium citrate or potassium citrate, and its concentration is 60~140 g / L. The buffer is selected from one or two of ammonium sulfate or boric acid, preferably including ammonium sulfate with a concentration of 20~50 g / L and boric acid with a concentration of 20~40 g / L.

[0093] In some embodiments of the present invention, in step (4), the electroplating process conditions are as follows: the electrolyte temperature is 50~70℃, which can be 50~55℃, 55~60℃, 60~65℃, or 65~70℃; the pH is 5.5~8.0, which can be 5.5~6.0, 6.0~6.5, 6.5~7.0, 7.0~7.5, or 7.5~8.0; and the current density is 3~7A / dm³. 2 It can be 3~4 A / dm 2 4~5A / dm 2 5~6 A / dm 2 It can also be 6~7 A / dm 2 .

[0094] In some embodiments of the present invention, in step (5), electrochemical roughening is performed by electroplating. The electrolyte used for electrochemical roughening includes nickel ions with a concentration of 8-17 g / L, hypophosphite ions with a concentration of 9-23 g / L, and molybdate ions with a concentration of 10-30 g / L.

[0095] In some embodiments of the present invention, in step (5), the electrolyte used for electrochemical roughening further includes a buffer and a complexing agent; the buffer is selected from boric acid, the concentration of which is 30~40 g / L, to maintain pH stability; the complexing agent is selected from one or two of tartrate or citrate, for example, sodium tartrate with a concentration of 35~45 g / L and sodium citrate with a concentration of 55~65 g / L, as a composite complexing agent to prevent nickel ions from precipitating under alkaline conditions, and to ensure the stability of the plating solution and uniform deposition.

[0096] In some embodiments of the present invention, in step (5), the electrochemical roughening process conditions are: electrolyte temperature 55~65℃, pH value 7.5~8.5, and current density 6~10 A / dm³. 2 Processing time is 8-20 seconds.

[0097] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating includes nickel ions with a concentration of 20-25 g / L and phosphorous acid with a concentration of 10-20 g / L.

[0098] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating further includes boric acid with a concentration of 30-50 g / L and phosphoric acid with a concentration of 25-35 g / L.

[0099] In some embodiments of the present invention, in step (6), the electrolyte used for electroplating further includes sodium saccharin with a concentration of 0.08~0.12 g / L and sodium dodecyl sulfate with a concentration of 0.01~0.03 g / L; sodium saccharin, as a stress reliever and brightener, helps to form a dense coating with low internal stress; sodium dodecyl sulfate, as a wetting agent, reduces pinholes, prevents hydrogen embrittlement, and makes the coating more uniform.

[0100] In some embodiments of the present invention, in step (6), the electroplating process conditions are: electrolyte temperature 55~65℃, pH value 1.0~2.0, and current density 1~3 A / dm³. 2 Processing time is 10-20 seconds.

[0101] In some embodiments of the present invention, a step of forming a rust-preventive layer on the surface of the cured layer is also included.

[0102] In some specific embodiments of the present invention, a rust-preventive layer is formed by electroplating, wherein the electroplating solution contains chromate. As one embodiment, the electroplating solution contains 0.8-1.2 g / L zinc ions, 0.8-1.2 g / L hexavalent chromium, and 0.5-1.0 g / L tin ions. The pH of the electrolyte is adjusted to 10-12 with sodium hydroxide, the temperature is maintained at 35-45°C, and the current density is 1.0-4.0 A / dm³. 2 The following treatment is performed to form a zinc-chromium-tin composite anti-rust layer; as another implementation method, the anti-rust treatment can also adopt the traditional chromate electroplating method, wherein the electroplating solution contains only hexavalent chromium at a concentration of 0.5~1.0 g / L, the pH is 11~13, the electrolyte temperature is about 35℃, and the current density is 0.5~1.5 A / dm³. 2 The following process is carried out to form the main chromate anti-rust layer.

[0103] In some specific embodiments of the present invention, a silane anti-rust layer is formed by coating a silane treatment solution. The coating method can be roller coating. The silane treatment solution contains a silane coupling agent with a concentration of 1% to 5%. The silane coupling agent includes one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-triethoxysilyl-1-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0104] In some embodiments of the present invention, steps (1) to (6) and the step of forming an anti-rust layer on the surface of the cured layer are performed on one surface of the copper foil body or simultaneously on both surfaces of the copper foil body. Depending on the application requirements, it can be implemented in two modes: Double-sided treatment mode: Steps (1) to (6) are performed simultaneously on both surfaces of the copper foil body, forming a symmetrical surface treatment layer structure. Single-sided treatment mode: Steps (1) to (6) are performed only on one designated surface of the copper foil body, forming an asymmetrical surface treatment layer structure. In both modes, an anti-rust layer can be selectively formed on one or both surfaces of the copper foil after step (6).

[0105] A third aspect of the present invention provides a printed circuit board comprising the aforementioned copper foil with low transmission loss and high peel strength.

[0106] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0107] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, this invention can be implemented using any prior art methods, apparatus, and materials similar to or equivalent to those described in the embodiments of this invention, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention.

[0108] Unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in this invention all employ conventional techniques in analytical chemistry and related fields. Unless otherwise stated, all materials and equipment used in this invention are commercially available.

[0109] Example 1

[0110] The method for preparing the copper foil with low transmission loss and high peel strength in this embodiment is described in reference to... Figure 2It includes the following steps:

[0111] (1) Select a copper foil body with Rz of 3μm and Sdr of 7% on one side. Spray the copper foil body with a concentrated sulfuric acid aqueous solution of 15% by mass and then rinse it with pure water.

[0112] (2) Preparation of an insulating layer on the surface of the copper foil: (2.1) First, a titanium-containing colloid was prepared: a) An appropriate amount of titanium oxysulfate was added to pure water, the concentration of titanium oxysulfate was 6 g / L, and ultrasonically stirred at 40℃ for 20 min at a stirring rate of 100 rpm to obtain a white suspension; b) An appropriate amount of urea was added to the above suspension, the concentration of urea was 3.6 g / L, and stirred at 90℃ until a transparent solution was obtained at a stirring rate of 60 rpm; c) The solution was stirred at 70℃ for 1 h to obtain a sol at a stirring rate of 40 rpm. (2.2) The obtained sol was coated on the surface of the copper foil and kept at 100℃ for 2 h to obtain an insulating layer. The amount of titanium attached to the insulating layer was 150 mg / m 2 .

[0113] (3) Preparation of an intermediate layer on the surface of the insulating layer: A nickel target is selected as the sputtering target material, and the copper foil is placed in the coating chamber and evacuated to a base vacuum of 6×10⁻⁶. -3 The pressure was 8 Pa, with 99.99% pure argon gas introduced at a flow rate of 200 sccm; the vacuum sputtering power was 8 kW. The amount of metal elements deposited in the intermediate layer was 300 mg / m³. 2 .

[0114] (4) Preparation of a passivation layer on the surface of the intermediate layer: The passivation layer was prepared by electroplating. The electrolyte formulation was as follows: nickel ion concentration of 18 g / L, hypophosphite ion concentration of 20 g / L, molybdate ion concentration of 26 g / L, sodium citrate concentration of 100 g / L, ammonium sulfate concentration of 25 g / L, and boric acid concentration of 30 g / L. The electrolyte temperature was 60 °C, the pH value of the electrolyte was 7.5, and the current density was 4 A / dm³. 2 The passivation layer has a thickness of 0.15 μm.

[0115] (5) The passivation layer surface was roughened. The electrolyte formulation was as follows: nickel ion concentration of 10 g / L, hypophosphite ion concentration of 14 g / L, molybdate ion concentration of 18 g / L, boric acid concentration of 35 g / L, sodium tartrate concentration of 40 g / L, and sodium citrate concentration of 60 g / L. The electrolyte temperature was 60℃, the electrolyte pH was 7.8, and the current density was 8 A / dm³. 2 Processing time: 12 seconds.

[0116] (6) The roughened layer is cured using the following electrolyte formula: nickel ion concentration 22 g / L, phosphorous acid concentration 15 g / L, boric acid concentration 40 g / L, phosphoric acid concentration 30 g / L, sodium saccharin concentration 0.1 g / L, and sodium dodecyl sulfate concentration 0.02 g / L. The electrolyte temperature is 60℃, the electrolyte pH is 1.5, and the current density is 2 A / dm³. 2 Processing time: 15 seconds.

[0117] (7) Rust prevention treatment is applied to both sides of the copper foil. A rust-preventive layer is deposited on the outermost surface of the copper foil by electroplating. The electrolyte contains 0.8 g / L hexavalent chromium, the pH of the electrolyte is 12, the temperature of the electrolyte is 35℃, and the current density is 1.0 A / dm³. 2 Processing time: 5 seconds.

[0118] Example 2

[0119] The method for preparing the copper foil with low transmission loss and high peel strength in this embodiment is described in reference to... Figure 2 It includes the following steps:

[0120] (1) Select a copper foil body with Rz of 2.5μm and Sdr of 5% on one side. Spray the copper foil body with a concentrated sulfuric acid aqueous solution of 15% by mass and then rinse it with pure water.

[0121] (2) Preparation of an insulating layer on the surface of the copper foil: (2.1) First, a titanium-containing colloid was prepared: a) An appropriate amount of titanium oxysulfate was added to pure water, the concentration of titanium oxysulfate was 8 g / L, and ultrasonically stirred at 40℃ for 30 min at a stirring rate of 150 rpm to obtain a white suspension; b) An appropriate amount of urea was added to the above suspension, the concentration of urea was 6 g / L, and stirred at 90℃ until a transparent solution was obtained at a stirring rate of 60 rpm; c) The solution was stirred at 70℃ for 2 h to obtain a sol at a stirring rate of 40 rpm. (2.2) The obtained sol was coated on the surface of the copper foil and kept at 100℃ for 2 h to obtain an insulating layer. The amount of titanium attached to the insulating layer was 200 mg / m 2 .

[0122] (3) Preparation of an intermediate layer on the surface of the insulating layer: A chromium target is selected as the sputtering target material, and the copper foil is placed in the coating chamber and evacuated to a base vacuum of 6×10⁻⁶. -3 The pressure was 99.99% pure argon gas at a flow rate of 200 sccm; the vacuum sputtering power was 8 kW. The amount of metal element deposited in the intermediate layer was 200 mg / m³. 2 .

[0123] (4) Preparation of a passivation layer on the surface of the intermediate layer: The passivation layer was prepared by electroplating. The electrolyte formulation was as follows: nickel ion concentration of 22 g / L, hypophosphite ion concentration of 20 g / L, tungstate ion concentration of 32 g / L, sodium citrate concentration of 120 g / L, ammonium sulfate concentration of 20 g / L, and boric acid concentration of 40 g / L. The electrolyte temperature was 50 °C, the pH value was 5.5, and the current density was 6 A / dm³. 2 The passivation layer has a thickness of 0.1 μm.

[0124] (5) The passivation layer surface was roughened. The electrolyte formulation was as follows: nickel ion concentration of 10 g / L, hypophosphite ion concentration of 14 g / L, molybdate ion concentration of 18 g / L, boric acid concentration of 35 g / L, sodium tartrate concentration of 40 g / L, and sodium citrate concentration of 60 g / L. The electrolyte temperature was 60℃, the electrolyte pH was 7.8, and the current density was 8 A / dm³. 2 Processing time: 16 seconds.

[0125] (6) The roughened layer is cured using the following electrolyte formula: nickel ion concentration 22 g / L, phosphorous acid concentration 15 g / L, boric acid concentration 40 g / L, phosphoric acid concentration 30 g / L, sodium saccharin concentration 0.1 g / L, and sodium dodecyl sulfate concentration 0.02 g / L. The electrolyte temperature is 60℃, the electrolyte pH is 1.5, and the current density is 2 A / dm³. 2 Processing time: 15 seconds.

[0126] (7) Apply rust prevention treatment to both sides of the copper foil by roller coating γ-glycidyl oxypropyltrimethoxysilane to the outermost surface of the copper foil to form a rust prevention layer.

[0127] Example 3

[0128] The method for preparing the copper foil with low transmission loss and high peel strength in this embodiment is described in reference to... Figure 2 It includes the following steps:

[0129] (1) Select a copper foil body with Rz of 4.5μm and Sdr of 10% on one side. Spray the copper foil body with a concentrated sulfuric acid aqueous solution of 15% by mass and then rinse it with pure water.

[0130] (2) Preparation of an insulating layer on the surface of the copper foil: (2.1) First, a titanium-containing colloid was prepared: a) An appropriate amount of titanium oxysulfate was added to pure water, the concentration of titanium oxysulfate was 4 g / L, and ultrasonically stirred at 40℃ for 20 min at a stirring rate of 100 rpm to obtain a white suspension; b) An appropriate amount of urea was added to the above suspension, the concentration of urea was 3 g / L, and stirred at 90℃ until a transparent solution was obtained at a stirring rate of 60 rpm; c) The solution was stirred at 70℃ for 1 h to obtain a sol at a stirring rate of 40 rpm. (2.2) The obtained sol was coated on the surface of the copper foil and kept at 100℃ for 2 h to obtain an insulating layer. The amount of titanium attached to the insulating layer was 108 mg / m 2 .

[0131] (3) Preparation of an intermediate layer on the surface of the insulating layer: A tin target is selected as the sputtering target material, and the copper foil is placed in the coating chamber and evacuated to a base vacuum of 6×10⁻⁶. -3 The pressure was 99.99% pure argon gas at a flow rate of 200 sccm; the vacuum sputtering power was 8 kW. The amount of metal element deposited in the intermediate layer was 350 mg / m³. 2 .

[0132] (4) Preparation of a passivation layer on the surface of the intermediate layer: The passivation layer was prepared by electroplating. The electrolyte formulation was as follows: nickel ion concentration of 22 g / L, hypophosphite ion concentration of 30 g / L, molybdate ion concentration of 26 g / L, sodium citrate concentration of 100 g / L, ammonium sulfate concentration of 25 g / L, and boric acid concentration of 30 g / L. The electrolyte temperature was 70 °C, the pH value of the electrolyte was 7.5, and the current density was 5 A / dm³. 2 The passivation layer has a thickness of 0.15 μm.

[0133] (5) The passivation layer surface was roughened. The electrolyte formulation was as follows: nickel ion concentration of 10 g / L, hypophosphite ion concentration of 14 g / L, molybdate ion concentration of 18 g / L, boric acid concentration of 35 g / L, sodium tartrate concentration of 40 g / L, and sodium citrate concentration of 60 g / L. The electrolyte temperature was 60℃, the electrolyte pH was 7.8, and the current density was 8 A / dm³. 2 Processing time: 8 seconds.

[0134] (6) The roughened layer is cured using the following electrolyte formula: nickel ion concentration 22 g / L, phosphorous acid concentration 15 g / L, boric acid concentration 40 g / L, phosphoric acid concentration 30 g / L, sodium saccharin concentration 0.1 g / L, and sodium dodecyl sulfate concentration 0.02 g / L. The electrolyte temperature is 60℃, the electrolyte pH is 1.5, and the current density is 2 A / dm³. 2 Processing time: 20 seconds.

[0135] (7) Rust prevention treatment is applied to both sides of the copper foil. A rust-preventive layer is deposited on the outermost surface of the copper foil by electroplating. The electrolyte contains 0.8 g / L hexavalent chromium, the pH of the electrolyte is 12, the temperature of the electrolyte is 35℃, and the current density is 1.0 A / dm³. 2 Processing time: 5 seconds.

[0136] Comparative Example 1

[0137] Except for step (4), in which the passivation layer is not roughened, the rest is the same as in Example 1.

[0138] Comparative Example 2

[0139] Except in step (2), where the concentration of titanium oxysulfate is 2 g / L and the amount of titanium adhering to the insulating layer is less than 100 mg / m², the concentration of titanium oxysulfate is less than 2 g / L. 2 The rest is the same as in Example 1.

[0140] Comparative Example 3

[0141] In addition to step (3), the vacuum sputtering time was shortened to achieve a nickel deposition rate of 40 mg / m³. 2 The rest is the same as in Example 1.

[0142] Comparative Example 4

[0143] In addition to step (3), the vacuum sputtering time was extended to achieve a nickel deposition rate of 650 mg / m³. 2 The rest is the same as in Example 1.

[0144] Comparative Example 5

[0145] Except for step (4), in which the concentration of sodium citrate in the electrolyte for preparing the passivation layer is 40 g / L and the concentration of nickel ions is 10 g / L, the rest is the same as in Example 1.

[0146] Comparative Example 6

[0147] Except for step (4), in which molybdate ions are not added to the electrolyte for preparing the passivation layer and the concentration of hypophosphite ions is 5 g / L, the rest is the same as in Example 1.

[0148] The products of the above embodiments and comparative examples were tested as follows:

[0149] (1) Copper foil body thickness: based on the mass of copper foil per unit area, for example, 1 dm 2 The thickness of the copper foil is obtained by dividing the mass of the copper foil by the density of copper, where the density of the copper foil is 8.93 g / cm³. 3 calculate.

[0150] (2) Surface roughness Rz: The surface roughness Rz was tested using a contact tester in accordance with GB / T 29847-2013.

[0151] (3) Surface roughness Sdr: Tested using a laser confocal microscope, referring to ISO 25178-3:2012.

[0152] (4) Thickness of passivation layer: Three 1dm samples were cut from the copper foil before and after the electroplating passivation layer treatment. 2 For each sample, three 5mm × 2mm test samples were cut. The cross-section of each test sample was polished using an ion polisher. The test samples were then placed under a scanning electron microscope at 15kx magnification to observe the cross-sectional thickness of the copper foil. Three points were randomly selected for testing each test sample, and the average value of all test results was taken. The difference between the thickness of the copper foil treated with the electroplated passivation layer and the thickness of the copper foil without the electroplated passivation layer is the thickness of the passivation layer.

[0153] (5) The amount of titanium attached to the insulating layer: Three 1dm sections were cut from the copper foil treated in step S2). 2 For samples of various sizes, the content of surface metal elements was measured using X-ray fluorescence spectrometry (XRF), and the average value of the test results was taken.

[0154] (6) The amount of metal elements attached in the intermediate layer: Three 1dm sections were cut from the copper foil that underwent surface treatment in step S3). 2 Samples of various sizes were digested with dilute acid, and the digested liquid was analyzed using inductively coupled plasma spectrometry (ICP) to obtain the content of different metal elements.

[0155] (7) Resistivity of the passivation layer: A passivation layer is electroplated on the copper foil body, and then the obtained copper foil is pressed into contact with an S1170G prepreg (held at 210℃ / 3MPa for 2.5h) to obtain a copper-clad laminate with an area of ​​15×15cm. 2 The copper foil body on the surface of the copper-clad laminate is etched using an etching solution. Then, the sheet resistance (in Ω / □) at 9 points on the board surface is measured using a four-probe tester, and the average value is taken. The resistivity is the average sheet resistance × the thickness of the passivation layer.

[0156] (8) Proportion of different elements in the passivation layer: Three 1mm×1mm samples were cut from the copper foil after electroplating passivation layer. The surface of the sample was scanned using an energy dispersive spectroscopy (EDS) instrument with a scanning electron microscope. Three points were tested on each sample to obtain the distribution of elements. Finally, the average value of all results was taken.

[0157] (9) Peel strength: The test was conducted according to Section 7.1 of GB / T 29847-2013, as follows: The prepared copper foil and prepreg were stacked, and four PPO resin prepregs with a glass transition temperature of 200℃ were placed between the two copper foils. Then, they were hot-pressed together. The hot-pressing temperature was 220~250℃, the surface pressure was 400~450psi, and the hot-pressing time was 100min~150min. The hot-pressed copper-clad laminate was cut into strips with a width of 3.0mm using a cutter. Then, the copper foil on one side of the copper-clad laminate was peeled off by 1~2cm using a utility knife. The peeled copper foil was fixed to one end of a weight. Finally, the copper foil was tested by moving the weight on the peel strength tester.

[0158] (10) Insertion Loss: Insertion loss was measured using the hot-pressed copper-clad laminates described above. The transmission loss in the high-frequency bandwidth was measured. In the evaluation of insertion loss, the transmission loss in the frequency range of 0-16 GHz was measured using the stripline resonator method with a bandwidth of 0-16 GHz. The microstrip line structure had the following characteristics: electrolyte thickness 50 μm, transmission line length 5 inch, conductor thickness 18 μm, conductor circuit width 120 μm, characteristic impedance 50 Ω, and impedance tolerance ±10%.

[0159] The test results are shown in Table 1 below.

[0160] Table 1. Test results of copper foils with low transmission loss and high peel strength in the examples and comparative examples.

[0161]

[0162] In Example 1, a copper foil with Rz=3μm was used, and the titanium deposition amount of the insulating layer was 150 mg / m. 2 The Ni interlayer adhesion amount is 300 mg / m 2 The resulting product exhibits a peel strength of 0.62 N / mm and an insertion loss of -0.752 dB / inch, demonstrating excellent overall performance.

[0163] In Example 2, the copper foil body is thinner and has a smoother surface compared to Example 1, increasing the titanium adhesion of the insulating layer to 200 mg / m². 2 The intermediate layer was changed from Ni to Cr and the adhesion amount was controlled at 200 mg / m³. 2 Meanwhile, the passivation layer is thinner (0.1 μm) and has lower resistivity (8.6 × 10⁻⁶). -4 The peel strength of the product was improved to 0.72 N / mm and the insertion loss was improved to -0.744 dB / inch by changing the anti-rust layer to silane treatment (Ω·cm).

[0164] In Example 3, the copper foil body is thicker and rougher than that in Example 1, and the titanium adhesion of the insulating layer is as low as 108 mg / m². 2 The intermediate layer was changed to Sn and the adhesion amount was increased to 350 mg / m³. 2 The resistivity of the passivation layer increased to 15.3 × 10⁻⁶. -4 The particle size of the coarsened particles was smaller than that of Example 1, the thickness of the cured layer was greater than that of Example 1, the peel strength decreased to 0.56 N / mm, and the insertion loss deteriorated to -0.758 dB / inch, indicating poor synergy between the layers.

[0165] Compared with Example 1, in step (4), the passivation layer was not roughened, and the peel strength of the product dropped sharply to 0.34 N / mm. Although the insertion loss was slightly improved to -0.751 dB / inch, this seriously sacrificed the peel strength, indicating that roughening is the key process to achieve high peel strength.

[0166] Compared with Example 1, in Comparative Example 2, the concentration of titanium oxysulfate was reduced to 2 g / L in step (2), resulting in an excessively low titanium adhesion amount in the insulating layer (<100 mg / m). 2 The insulation performance was substandard, and the insertion loss increased significantly to -0.785 dB / inch. Although the peel strength of the product increased slightly to 0.63 N / mm, the core problem was the surge in high-frequency losses caused by the deterioration of the insulation performance.

[0167] Compared with Example 1, in Comparative Example 3, the amount of Ni attached to the intermediate layer in step (3) was only 40 mg / m. 2 The product failed because the intermediate layer lacked sufficient conductivity, preventing subsequent electroplating processes. This demonstrates that the intermediate layer must possess sufficient continuity and conductivity to ensure the successful application of subsequent passivation and roughening layers.

[0168] Compared with Example 1, in Comparative Example 4, the amount of Ni attached to the intermediate layer in step (3) is as high as 650 mg / m 2 The insertion loss of the product increased to -0.771 dB / inch, while the peel strength remained at 0.62 N / mm. The analysis suggests that the excessively thick Ni interlayer introduces eddy current effects and electromagnetic shielding at high frequencies, leading to signal shunting and thus increasing transmission loss.

[0169] Compared to Example 1, Comparative Example 5 reduced the concentrations of nickel ions and sodium citrate in the electrolyte used to prepare the passivation layer, resulting in an increase in the resistivity of the passivation layer to 17.1 × 10⁻⁶. -4The nanoparticle size of the coarsened layer decreased to 64 nm, the surface brightness increased, and the peel strength decreased to 0.5 N / mm. Analysis suggests that the high resistivity of the passivation layer inhibited the coarsening current efficiency, preventing the coarsened particles from growing sufficiently. The sparse coarsened structure weakened the mechanical anchoring effect, thus reducing the peel strength.

[0170] Compared to Example 1, Comparative Example 6 completely removed molybdate ions and significantly reduced hypophosphate concentration in the electrolyte used to prepare the passivation layer, resulting in a sharp decrease in the resistivity of the passivation layer to 4.5 × 10⁻⁶. -4 The nanoparticle size of the roughened layer was significantly reduced to 43 nm, the surface brightness was greatly increased, and the peel strength was severely deteriorated to 0.41 N / mm. Analysis suggests that the low resistivity of the passivation layer prevented the current from concentrating during the roughening process, resulting in insufficient driving force for roughening nucleation and making it difficult to form an effective roughened structure. Ultimately, insufficient anchoring points led to peel strength failure.

[0171] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A copper foil having low transmission loss and high peel strength, characterized by, The copper foil body and the surface treatment layer, the surface treatment layer includes the insulating layer, the intermediate layer, the passivation layer, the roughening layer and the solidification layer which are sequentially arranged on the surface of the copper foil body; the insulating layer is the titanium-containing oxide layer, and the attachment amount of titanium element is 100-200 mg / m 2 ; The intermediate layer is a conductive metal layer formed by vacuum sputtering; the resistivity of the passivation layer is 7x10 -4 -3 Ω·cm; the roughening layer has nanoparticles formed on the surface thereof, and the lightness L* value of the roughening layer is ≤65.​ 2. The low transmission loss, high peel strength copper foil of claim 1, wherein, The surface treatment layer comprises one or more of the following features: (a) the intermediate layer comprises one or more of nickel, cobalt, chromium, titanium, manganese, zinc, tungsten, tin; (b) the amount of the metal element adhered in the intermediate layer is 100 to 500 mg / m 2 , preferably 200 to 350 mg / m 2 ; (c) the passivation layer is a nickel-phosphorus-based alloy layer; (d) the thickness of the passivation layer is 0.05-0.2 μm; (e) the passivation layer has a resistivity of 8.5 x 10 -4 1.55 x 10 -3 Ω-cm; (f) the roughening layer comprises nickel, molybdenum, and phosphorus; (g) the diameter of the nanoparticles is 60-250 nm, and the center-to-center spacing between adjacent nanoparticles is 50-300 nm; (h) the solidification layer comprises nickel and phosphorus; (i) the thickness of the solidification layer is 5-30 nm; (j) the surface treatment layer further comprises a rust-prevention layer disposed on the surface of the solidification layer; (k) at least one surface of the copper foil body is provided with a surface treatment layer.

3. The low transmission loss, high peel strength copper foil of claim 2, wherein, The surface treatment layer comprises one or more of the following features: (a1) the intermediate layer comprises one or more of nickel, chromium, cobalt, tungsten, and tin; (c1) the nickel-phosphorus-based alloy layer further contains at least one of molybdenum and tungsten; (f1) in the roughening layer, the projection area coverage of the nanoparticles, as viewed from a planar perspective, is 60% or more; (i1) the thickness of the solidification layer is 15-28 nm; (j1) the rust-prevention layer is selected from at least one of a chromate layer and a silane layer.

4. A method of producing a copper foil having low transmission loss and high peel strength according to any one of claims 1 to 3, characterized by, The method comprises the following steps: (1) providing a copper foil body and cleaning the surface thereof; (2) forming a titanium-containing oxide insulating layer on the surface of the copper foil body; (3) forming the intermediate layer on the surface of the insulating layer by vacuum sputtering; (4) forming the passivation layer on the surface of the intermediate layer by electroplating; (5) forming the roughening layer on the surface of the passivation layer by electrochemical roughening; (6) forming the solidification layer on the surface of the roughening layer by electroplating.

5. The method of claim 4, wherein the copper foil has a peel strength of 100 gf / 3 mm or more and a transmission loss of 10 dB / m or less at a frequency of 1 MHz. The method comprises one or more of the following features: (a) in step (1), the profile maximum height Rz of the contact surface of the copper foil body and the insulating layer is 2.5 μm-4.5 μm; (b) in step (1), the interface extension area ratio Sdr of the contact surface of the copper foil body and the insulating layer is 5%-10%; (c) in step (1), the cleaning is performed using an acidic cleaning solution; (d) in step (2), the titanium-containing oxide insulating layer is prepared by a sol-gel method, and the preparation process comprises three stages of sol preparation, film coating, and heat treatment conversion in sequence.

6. The method of claim 4, wherein the copper foil has a peel strength of 100 gf / 3 mm or more. The method comprises one or more of the following features: (a) In step (3), the base vacuum of the vacuum sputtering is not higher than 8 x 10 -3 Pa; (b) in step (3), the vacuum sputtering uses argon as the working gas, and the gas flow is 100-400 sccm; (c) in step (3), the power of the vacuum sputtering is 5-15 kW; (d) in step (3), the target material used in the vacuum sputtering comprises one or more of nickel, chromium, tin, tungsten, or cobalt; (e) in step (3), during the vacuum sputtering process, the copper foil substrate is carried by a cooling roller and the temperature is controlled; (f) in step (4), the electrolyte used in the electroplating comprises nickel ions at a concentration of 14-25 g / L, hypophosphite ions at a concentration of 15-35 g / L, molybdate ions at a concentration of 16-35 g / L, or tungstate ions at a concentration of 17-35 g / L. (g) In step (4), the electrolyte used in the electroplating further comprises a complexing agent and a buffering agent; (h) In step (4), the process conditions for the electroplating are: electrolyte temperature is 50-70°C, pH is 5.5-8.0, current density is 3-7 A / dm 2 .

7. The method of claim 4, wherein the copper foil has a peel strength of 100 gf / 3 mm or more and a transmission loss of 10 dB / m or less at a frequency of 1 MHz. One or more of the following features are included: (a) In step (5), the electrolyte used in the electrochemical roughening comprises nickel ions at a concentration of 8-17 g / L, hypophosphite ions at a concentration of 9-23 g / L, and molybdate ions at a concentration of 10-30 g / L; (b) In step (5), the electrolyte used in the electrochemical roughening further comprises a buffering agent and a complexing agent; (c) In step (5), the process conditions for the electrochemical roughening are: electrolyte temperature 55-65°C, pH value 7.5-8.5, current density 6-10 A / dm², and treatment time 8-20 seconds; (d) In step (6), the electrolyte used in the electroplating comprises nickel ions at a concentration of 20-25 g / L and phosphorous acid at a concentration of 10-20 g / L; (e) In step (6), the electrolyte used in the electroplating further comprises boric acid at a concentration of 30-50 g / L and phosphoric acid at a concentration of 25-35 g / L; (f) In step (6), the electrolyte used in the electroplating further comprises sodium saccharin at a concentration of 0.08-0.12 g / L and sodium dodecyl sulfate at a concentration of 0.01-0.03 g / L; (g) In step (6), the process conditions for electroplating: electrolyte temperature 55-65°C, pH value 1.0-2.0, current density 1-3 A / dm 2 , processing time 10-20 seconds.

8. The method of claim 4, wherein the copper foil has a peel strength of 100 gf / inch or more and a transmission loss of 10 dB / m or less at 1 MHz. The step of forming a rust-preventive layer on the surface of the solidified layer is further included; and / or, the steps (1)-(6) are applied only to one surface of the copper foil body, or the steps (1)-(6) are applied simultaneously to both surfaces of the copper foil body.

9. The method of claim 8, wherein the copper foil has a peel strength of 100 gf / inch or more and a transmission loss of 10 dB / m or less at 1 MHz. The step of forming a rust-preventive layer includes one or more of the following features: (a) The rust-preventive layer is formed by an electroplating method, and the electroplating solution comprises a chromate salt; (b) A silane rust-preventive layer is formed by applying a silane treatment solution, and the silane treatment solution comprises a silane coupling agent at a concentration of 1%-5%.

10. A printed circuit board, characterized by A copper foil with low transmission loss and high peel strength as claimed in any one of claims 1-3.

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