A coupling agent treatment liquid dedicated to ultra-low profile copper foil and application thereof

Abstract

The present application belongs to the technical field of electronic materials, and particularly relates to a super-low profile copper foil for high-frequency high-speed printed circuit board (PCB), and more particularly to a HVLP5-grade copper foil with extremely low surface roughness and high peeling strength and a preparation method thereof, which is realized by combining a special coupling agent formula with a magnetron sputtering-electroplating composite process, and comprises a main coupling agent, a metal complexation enhancer, a film-forming promoter and a solvent; the metal complexation enhancer comprises one or more of tin acetylacetone and zinc acetylacetone. The composite process of'magnetron sputtering seed layer + water electroplating thickening' completely gets rid of the dependence on the quality of the smooth surface of the cathode roller, and realizes independent and accurate control of the roughness of the smooth surface and the rough surface of the copper foil. The unique coupling agent formula containing the Sn / Zn metal complexation enhancer has a strong chemical synergistic effect with the super-flat and high-activity surface formed by magnetron sputtering, and solves the core contradiction between the super-low profile and the high peeling strength.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, specifically relating to an ultra-low profile copper foil for high-frequency and high-speed printed circuit boards (PCBs), and more particularly to an HVLP5 grade copper foil and its preparation method that achieves extremely low surface roughness and high peel strength by combining a special coupling agent formulation with a magnetron sputtering-electroplating composite process. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence (AI) servers, and high-performance computing (HPC), signal transmission rates are moving towards 112Gbps and above, placing extremely high demands on copper foil, a key material for PCB substrates. HVLP5 (fifth-generation ultra-low profile) copper foil must meet stringent requirements such as a roughness (Rz) of <0.1 μm and a smoothness (Rz) of <0.15 μm to reduce skin effect loss in signal transmission.

[0003] Currently, the high-end HVLP5 copper foil market is mainly monopolized by Japanese manufacturers through traditional cathode roller electrolysis. This process has inherent drawbacks: the roughness of the copper foil's smooth surface (the surface in contact with the cathode roller) is directly determined by the surface condition of the cathode roller and cannot be effectively improved through post-processing, becoming a bottleneck for further performance enhancement. Furthermore, as the roughness decreases, the adhesion (peel strength) between the copper foil and the resin substrate drops sharply, creating a contradiction between "low roughness" and "high adhesion." Traditional solutions often employ physical roughening or general coupling agents, but the former sacrifices roughness performance, while the latter has limited reinforcing effect on ultra-low profile surfaces and often results in delamination or copper cracking in PCB manufacturing processes (such as 288°C hot air soldering) due to insufficient heat resistance.

[0004] Therefore, developing a new generation of copper foil manufacturing technology that can simultaneously achieve nanoscale roughness control and superior adhesion enhancement has become an urgent need for the industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a coupling agent formulation specifically for ultra-low profile copper foil. This formulation can form strong chemical bonds on nanoscale roughness surfaces, significantly improving peel strength and heat resistance.

[0006] Another objective of this invention is to provide a method for preparing ultra-low profile copper foil based on a composite process of magnetron sputtering and electroplating. This method can independently and precisely control the roughness of the smooth and rough surfaces of the copper foil, fundamentally avoiding the limitations of traditional cathode roller processes, and using the above-mentioned special coupling agent formulation to prepare high-performance copper foil that fully meets the HVLP5 standard.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A coupling agent treatment solution specifically for ultra-low profile copper foil includes: a main coupling agent, a metal complexing enhancer, a film-forming promoter, and a solvent; wherein the metal complexing enhancer includes one or more of tin acetylacetonate and zinc acetylacetonate.

[0009] The core innovation of this invention lies in the introduction of a metal complexation enhancer. The amino group (-NH2) of the main coupling agent, aminosilane, can react with the epoxy groups in the resin (film-forming accelerator), while its siloxane group can hydrolyze to form Si-OM covalent bonds with the oxide layer on the copper foil surface. The added Sn / Zn organometallic compound can decompose to form nano-oxides during heat treatment, which interweave with the silane network, greatly enhancing the crosslinking density, thermal stability, and mechanical anchoring effect of the interface layer. Thus, a qualitative leap in bonding strength is achieved with almost no increase in physical roughness.

[0010] Preferably, in the metal complexing enhancer, the mass ratio of tin acetylacetone to zinc acetylacetone is 1 to 3: 1.

[0011] The metal complexation enhancer is an organometallic compound, which is a mixture of tin acetylacetone (Sn(C5H7O2)2) and zinc acetylacetone (Zn(C5H7O2)2) in a mass ratio of 1:1 to 3:1.

[0012] Preferably, the components include the following volume percentages:

[0013] The main coupling agent is 3-5%.

[0014] The metal complexing enhancer is 1-2%.

[0015] The film-forming promoter is 0.5-1%.

[0016] The remaining amount of solvent.

[0017] Preferably, the main coupling agent includes an aminosilane coupling agent; the film-forming promoter includes an aqueous polyurethane dispersion or polyvinyl butyral (PVB); the solvent includes one or more of deionized water and ethanol; the pH of the coupling agent treatment solution specifically for ultra-low profile copper foil includes 8.5 to 9.5; the coupling agent treatment solution specifically for ultra-low profile copper foil also includes a pH adjuster.

[0018] Film-forming accelerators can be selected from water-based polyurethane dispersions or film-forming polymers such as polyvinyl butyral (PVB). These polymers can form an interpenetrating structure with the silane coupling agent network, enhancing the continuity, toughness, and density of the interfacial layer, thereby jointly improving peel strength and heat resistance. When using water-based polyurethane dispersions as film-forming accelerators, they further improve the leveling properties of the coupling agent treatment solution and form a flexible polymer film after curing, interpenetrating with the silane coupling agent network and enhancing the toughness and continuity of the interfacial layer. When using polyvinyl butyral as a film-forming accelerator, it effectively improves the adhesion of the treatment solution and the film quality, resulting in a denser and more uniform interfacial layer.

[0019] Preferably, the solvent comprises a mixture of deionized water and ethanol. Using only deionized water leads to problems such as excessively rapid hydrolysis of the coupling agent, poor stability, poor wetting and spreading properties, and slow drying, ultimately affecting coating quality and interfacial bonding strength. Using only ethanol results in insufficient hydrolysis of KH-550 in pure ethanol, leading to inadequate formation of its silanol groups (-Si-OH), which severely affects its chemical bonding (Si-O-Cu bond) with the copper foil surface, resulting in a significant decrease in peel strength. Using a mixture of deionized water and ethanol offers the following advantages:

[0020] 1. The main coupling agent, KH-550, etc., only functions effectively after hydrolysis. While pure water can hydrolyze it, the process is too rapid, easily leading to premature self-polymerization and condensation of the silanol, forming a white precipitate and making the treated solution unstable. The addition of ethanol can regulate the hydrolysis rate, inhibit self-polymerization, and significantly improve the storage stability of the treated solution.

[0021] 2. The ultra-flat copper foil formed by magnetron sputtering has a high surface energy, but remains very smooth microscopically. Pure water has a high surface tension and may not be able to completely and uniformly wet the entire surface, easily leading to uneven coating and the formation of "pinhole" defects. Ethanol has a low surface tension, and its addition can significantly reduce the surface tension of the mixed solvent, allowing it to spread rapidly on the copper foil surface and form an extremely uniform film, which is crucial for ensuring the consistency of the final interface properties.

[0022] 3. Water evaporates slowly, and using it alone may result in incomplete drying or water stains in the oven. Ethanol evaporates quickly, and when mixed with water, it can create a gradient evaporation process, allowing the coupling agent molecules sufficient time to arrange themselves in an orderly manner and cross-link, forming a dense interfacial layer.

[0023] Preferably, the main coupling agent comprises one or more of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-540), or N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792); the solvent comprises a volume ratio of deionized water to ethanol of 7:3; and the pH adjuster comprises ammonia.

[0024] An application of the above-mentioned coupling agent treatment solution specifically for ultra-low profile copper foil, characterized in that it is used for the preparation of ultra-low profile copper foil.

[0025] Preferably, it includes the following steps:

[0026] S1. Substrate preparation: Prepare the copper foil substrate;

[0027] S2. The copper foil body is magnetron sputtered to form a nanocrystal seed layer to obtain sputtered copper foil;

[0028] S3. The sputtered copper foil is thickened and alloyed by electroplating to obtain electroplated thickened copper foil.

[0029] S4. Passivate the electroplated thickened copper foil, and then treat it with the coupling agent treatment solution specifically for ultra-low profile copper foil to obtain ultra-low profile copper foil.

[0030] Preferably, it includes the following steps:

[0031] S1. Substrate preparation, using electrolytic green foil with a thickness of 12~18μm as the main body of the copper foil;

[0032] S2. The copper foil body is subjected to magnetron sputtering at a vacuum level below 5.0 × 10⁻⁶. -3 The working gas introduced into the cavity includes argon gas, with a pressure of 0.3~0.8 Pa. The target material used is pure copper, and the sputtering power is applied to achieve a power density of 1.5~2.5 W / cm³. 2 By controlling the feed rate of the raw foil, a nanoscale copper seed layer with a thickness of 50~150 nm is deposited on the surface to obtain the sputtered copper foil;

[0033] S3. The sputtered copper foil is introduced into an electroplating tank containing a copper electroplating solution. The electroplating temperature is 40~50℃ and the cathode current density is 10~15 ASD. Electroplating is performed to increase the total electroplating thickness to 0.3~0.6 μm, thereby obtaining the electroplated thickened copper foil. The copper electroplating solution includes copper sulfate, sulfuric acid, chloride ions, nickel ions, brightener, and leveling agent.

[0034] S4. Passivate the electroplated thickened copper foil, and then uniformly coat the coupling agent treatment solution specifically for ultra-low profile copper foil onto the rough surface, with a coating amount of 0.5~1.5 g / m². 2 The ultra-low profile copper foil is then heat-treated in an oven at 120-150°C for 1-2 minutes to obtain the ultra-low profile copper foil; the passivation method includes one or more of zinc-chromium alloy passivation and zinc-nickel alloy passivation; the coating method includes microgravure coating.

[0035] S5. After cooling, the ultra-low profile copper foil undergoes anti-oxidation post-treatment and is then wound up.

[0036] Preferably, in step S3, the copper electroplating solution comprises 80-100 g / L copper sulfate, 100-120 g / L sulfuric acid, 50-70 ppm chloride ions, 5-15 ppm nickel ions, 50-200 mL / kL brightener, 10-50 mL / kL leveling agent, and the remainder deionized water. Using deionized water as a solvent, the above components are adjusted to a suitable concentration to obtain the copper electroplating solution. Generally, chloride ions are introduced in the form of hydrochloric acid (HCl), and nickel ions are introduced in the form of nickel sulfate.

[0037] A method for preparing ultra-low profile copper foil includes the following steps:

[0038] (1) Substrate preparation: Provide a roll of electrolytic green foil with a thickness of 12~18μm as the copper foil body.

[0039] (2) Formation of a nanocrystal seed layer by magnetron sputtering: The green foil is unwound so that its rough side faces the sputtering target. Under a vacuum level below 5.0 × 10⁻⁶, -3 Argon gas is introduced into the cavity at a pressure of 0.3–0.8 Pa as the working gas. Pure copper (purity ≥99.99%) is used as the target material, and sputtering power is applied to achieve a power density of 1.5–2.5 W / cm³. 2 The feed rate of the green foil is controlled to deposit a 50-150 nm thick nanoscale copper seed layer on its surface. This layer has a dense structure and uniform grains, resulting in extremely low initial roughness (Rz < 0.05 μm).

[0040] (3) Electroplating Thickening and Alloying: The sputtered copper foil is introduced into an electroplating bath containing copper electroplating solution. The main components of the electroplating solution are: copper sulfate 80~100 g / L, sulfuric acid 100~120 g / L, chloride ions 50~70 ppm, and appropriate amounts of brightener and leveling agent. Electroplating is carried out at a temperature of 40~50℃ and a cathode current density of 10~15 ASD (amperes / dm²) to increase the total thickness of the copper foil layer to 0.3~0.6 μm. An additional 5~15 ppm of nickel ions (in the form of nickel sulfate) is added to the electroplating solution. The trace amount of nickel co-deposited with copper can refine the grain size of the electroplated layer, further improving the heat resistance and mechanical strength of the copper foil layer.

[0041] (4) Surface passivation and coupling agent treatment: The electroplated thickened copper foil is subjected to conventional zinc-chromium or zinc-nickel alloy passivation treatment to enhance its oxidation resistance. Finally, the coupling agent treatment solution described in Scheme 1 is uniformly coated onto the rough surface of the copper foil using a micro-gravure coating method, with the coating amount controlled at 0.5~1.5 g / m². 2 .

[0042] Heat treatment in an oven at 120~150℃ for 1~2 minutes to allow the coupling agent to fully cross-link and cure, forming a strong functionalized interface layer.

[0043] (5) Post-processing and winding: After cooling, the copper foil surface is subjected to anti-oxidation treatment, and finally the finished product is obtained by winding.

[0044] An ultra-low profile copper foil obtained by the above application.

[0045] The reduction in the surface roughness of copper foil means an exponential decrease in its effective contact area and mechanical anchoring effect with the resin substrate, which directly leads to a sharp decline in the peel strength between the two. Meanwhile, the multiple lead-free reflow soldering processes (peak temperature 288℃) required for high-end chip packaging pose a significant challenge to the interface's heat resistance reliability. Therefore, reconciling 'low roughness', 'high peel strength', and 'high heat resistance' presents a difficult problem.

[0046] This invention is achieved through:

[0047] Step 1: Substrate Interface Reconstruction. A 50-150 nm nanocrystalline copper seed layer is deposited on the rough surface of the electrolytic green foil using magnetron sputtering. This process not only achieves a smooth surface roughness (R0)... z The leap from micrometer to nanometer scale (<0.05μm) creates a dense, uniform, and highly reactive pure copper surface, providing an ideal substrate for subsequent chemical bonding that traditional electrolytic rough surfaces cannot match. This surface is rich in dangling bonds and has uniform oxidation, a prerequisite for achieving high-strength chemical bonding.

[0048] Step 2: Molecular-level interface enhancement. For this nanoscale active surface, we designed a dedicated complex-linking agent system. The core mechanism lies in the formation of strong Si-O-Cu covalent bonds between the silanol groups (-Si-OH) of γ-aminopropyltriethoxysilane (KH-550) and the Cu-OH / Cu-O bonds on the substrate surface; its amino groups (-NH2) react with the epoxy groups in the resin. Crucially, we introduced tin acetylacetonate and zinc acetylacetonate as metal complexing reinforcing agents. During curing at 120–150 °C, they decompose to generate SnO2 and ZnO nanoparticles, which are in situ embedded in the cross-linking silane three-dimensional network. The SnO2 nanophase provides extremely high thermal stability and rigidity, effectively resisting thermal shock at 288 °C; the ZnO nanophase imparts a certain degree of toughness to the interface layer, alleviating internal stress caused by CTE mismatch. This synergistic effect of the 'rigid SnO2-tough ZnO' nanocomposite creates a strong and heat-resistant interfacial transition layer at the molecular scale, achieving a doubling of peel strength and heat resistance without relying on physical roughness.

[0049] Compared with the prior art, implementing the present invention has the following beneficial effects:

[0050] Revolutionary process: The composite process of "magnetron sputtering seed layer + electroplating thickening" completely eliminates the dependence on the surface quality of the cathode roller, and realizes independent and precise control over the surface roughness of the copper foil.

[0051] Breakthrough in bonding strength: The unique coupling agent formula containing Sn / Zn metal complexation enhancer produces a powerful chemical synergy with the ultra-flat, highly active surface formed by magnetron sputtering, solving the core contradiction between ultra-low profile and high peel strength. Detailed Implementation

[0052] To make the technical solution of the present invention easier to understand, the present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. Modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance of the present invention are all within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0053] Example 1

[0054] A method for preparing ultra-low profile copper foil includes the following steps:

[0055] (1) Substrate preparation: Provide a roll of electrolytic green foil with a thickness of 18μm as the copper foil body.

[0056] (2) Formation of a nanocrystal seed layer by magnetron sputtering: The green foil is unwound so that its rough side faces the sputtering target. Under a vacuum level below 5.0 × 10⁻⁶, -3 Argon gas is introduced into the cavity at a pressure of 0.5 Pa as the working gas. Pure copper (purity ≥ 99.99%) is used as the target material, and sputtering power is applied to achieve a power density of 2.0 W / cm³. 2 The foil feed rate was controlled at 2 m / min to deposit a nanoscale copper seed layer approximately 100 nm thick on its surface. This layer has a dense structure and uniform grain size, resulting in extremely low initial roughness (R0). z <0.05 μm).

[0057] (3) Electroplating for Thickening and Alloying: The sputtered copper foil is introduced into an electroplating bath containing copper electroplating solution. The main components of the electroplating solution are: copper sulfate 90 g / L, sulfuric acid 110 g / L, Cl... - 60 ppm, current density 12 ASD, with 10 ppm Ni added. 2+Add appropriate amounts of brightener and leveling agent. Electroplating is carried out at a temperature of 45℃ and a cathode current density of 12 ASD to thicken the total copper tooth layer to 0.5 μm.

[0058] (4) Surface passivation and coupling agent treatment: The electroplated thickened copper foil is subjected to conventional zinc-chromium alloy passivation treatment to enhance its oxidation resistance. Finally, the coupling agent treatment solution is uniformly coated onto the rough surface of the copper foil using a micro-gravure coating method. Coupling agent treatment solution: 4% KH-550, 1.5% Sn / Zn mixed complexing agent (tin acetylacetone (Sn(C5H7O2)2) and zinc acetylacetone (Zn(C5H7O2)2) mass ratio 2:1), 0.8% waterborne polyurethane, pH=9.0. Coating amount 1.0 g / m 2 .

[0059] Heat treatment in an oven at 140°C for 90 seconds allows the coupling agent to fully cross-link and cure, forming a robust functionalized interface layer.

[0060] (5) Post-processing and winding: After cooling, the copper foil surface is subjected to anti-oxidation treatment, and finally the finished product is obtained by winding.

[0061] Performance test results: Surface roughness R z =0.07 μm, surface roughness R z =0.11 μm, peel strength of 0.63 N / mm, no abnormalities after hot air welding at 288℃, no delamination, no blistering.

[0062] Example 2

[0063] A method for preparing ultra-low profile copper foil includes the following steps:

[0064] (1) Substrate preparation: Provide a roll of electrolytic green foil with a thickness of 12μm as the main body of copper foil.

[0065] (2) Formation of a nanocrystal seed layer by magnetron sputtering: The green foil is unwound so that its rough side faces the sputtering target. Under a vacuum level below 5.0 × 10⁻⁶, -3 Argon gas is introduced into the cavity at a pressure of 0.3 Pa as the working gas. Pure copper (purity ≥ 99.99%) is used as the target material, and sputtering power is applied to achieve a power density of 1.5 W / cm³. 2 The foil feed rate was controlled at 4 m / min to deposit a nanoscale copper seed layer approximately 50 nm thick on its surface. This layer has a dense structure and uniform grain size, resulting in extremely low initial roughness (R0). z <0.05 μm).

[0066] (3) Electroplating for Thickening and Alloying: The sputtered copper foil is introduced into an electroplating bath containing copper electroplating solution. The main components of the electroplating solution are: copper sulfate 80 g / L, sulfuric acid 100 g / L, Cl... - 50 ppm, add 5 ppm Ni 2+ Add appropriate amounts of brightener and leveling agent. Electroplating is carried out at a temperature of 40℃ and a cathode current density of 10 ASD to thicken the total copper tooth layer to 0.5 μm.

[0067] (4) Surface passivation and coupling agent treatment: The electroplated thickened copper foil is subjected to conventional zinc-nickel alloy passivation treatment to enhance its oxidation resistance. Finally, the coupling agent treatment solution is uniformly coated onto the rough surface of the copper foil using a micro-gravure coating method. Coupling agent treatment solution: 3% KH-540, 0.5% Sn / Zn mixed complexing agent (tin acetylacetone (Sn(C5H7O2)2) and zinc acetylacetone (Zn(C5H7O2)2) mass ratio 1:1), 0.5% polyvinyl butyral (PVB), pH=8.5. Coating amount: 0.5 g / m 2 .

[0068] Heat treatment in an oven at 120°C for 60 seconds allows the coupling agent to fully cross-link and cure, forming a robust functionalized interface layer.

[0069] (5) Post-processing and winding: After cooling, the copper foil surface is subjected to anti-oxidation treatment, and finally the finished product is obtained by winding.

[0070] Performance test results: Surface roughness R z =0.08 μm, surface roughness R z =0.12 μm, peel strength reached 0.58 N / mm, no abnormalities after hot air welding at 288℃, no delamination, no blistering.

[0071] Example 3

[0072] A method for preparing ultra-low profile copper foil includes the following steps:

[0073] (1) Substrate preparation: Provide a roll of electrolytic green foil with a thickness of 15μm as the copper foil body.

[0074] (2) Formation of a nanocrystal seed layer by magnetron sputtering: The green foil is unwound so that its rough side faces the sputtering target. Under a vacuum level below 5.0 × 10⁻⁶, -3 Argon gas is introduced into the cavity at a pressure of 0.8 Pa as the working gas. Pure copper (purity ≥ 99.99%) is used as the target material, and sputtering power is applied to achieve a power density of 2.5 W / cm³. 2The foil feed rate was controlled at 1.3 m / min to deposit a nanoscale copper seed layer approximately 150 nm thick on its surface. This layer has a dense structure and uniform grain size, resulting in extremely low initial roughness (R0). z <0.05 μm).

[0075] (3) Electroplating for Thickening and Alloying: The sputtered copper foil is introduced into an electroplating bath containing copper electroplating solution. The main components of the electroplating solution are: 100 g / L copper sulfate, 120 g / L sulfuric acid, and Cl... - 70 ppm, with the addition of 15 ppm Ni 2+ Add appropriate amounts of brightener and leveling agent. Electroplating is carried out at a temperature of 50℃ and a cathode current density of 15 ASD to thicken the total copper tooth layer to 0.6 μm.

[0076] (4) Surface passivation and coupling agent treatment: The electroplated thickened copper foil is subjected to conventional zinc-chromium alloy passivation treatment to enhance its oxidation resistance. Finally, the coupling agent treatment solution is uniformly coated onto the rough surface of the copper foil using a micro-gravure coating method. Coupling agent treatment solution: 5% KH-792, 2% Sn / Zn mixed complexing agent (tin acetylacetone (Sn(C5H7O2)2) and zinc acetylacetone (Zn(C5H7O2)2) mass ratio 3:1), 1% waterborne polyurethane, pH=9.5. Coating amount 1.5 g / m 2 .

[0077] Heat treatment in an oven at 150°C for 120 seconds allows the coupling agent to fully cross-link and cure, forming a robust functionalized interface layer.

[0078] (5) Post-processing and winding: After cooling, the copper foil surface is subjected to anti-oxidation treatment, and finally the finished product is obtained by winding.

[0079] Performance test results: Surface roughness R z =0.09 μm, surface roughness R z =0.13 μm, peel strength of 0.61 N / mm, no abnormalities after hot air welding at 288℃, no delamination or blistering.

[0080] Example 1

[0081] The copper foils prepared in Examples 1-3 of this invention and the copper foils obtained by the conventional HVLP4 process were subjected to multiple parallel performance tests, and the comparison results are shown in Table 1.

[0082] Table 1

[0083]

[0084] The test data above show that the ultra-low profile copper foils prepared in Examples 1-3 of this invention have a surface roughness R.z All are significantly lower than 0.1 μm, and the surface roughness R z With a thickness of less than 0.15μm, it fully meets the HVLP5 standard.

[0085] Within the framework of traditional copper foil manufacturing technology, "ultra-low profile (low roughness)" and "high peel strength" are indeed two contradictory and difficult-to-achieve performance indicators. Traditional copper foil (including HVLP4 and earlier models) primarily uses an electrolytic process to create microscopic "nodular" or "peak-like" rough structures on the surface. When resin flows through and cures, it embeds itself into these microstructures, forming a strong mechanical anchoring force. Roughness (R... z A higher roughness value indicates more and deeper "anchor points," resulting in a stronger mechanical interlocking effect and naturally higher peel strength. To achieve ultra-low roughness at the HVLP5 level, these microscopic rough structures must be suppressed or eliminated to a great extent. This is analogous to polishing a rough stone wall into a smooth glass surface; the resin loses its anchor points to "grip," causing the mechanical anchoring effect to decay exponentially. Therefore, simply relying on physical methods to reduce roughness will inevitably lead to a sharp decrease in peel strength.

[0086] The most outstanding feature of this invention is that, despite such low roughness, the peel strength is better than 0.58 N / mm, far exceeding that of traditional HVLP4 copper foil (0.45~0.55 N / mm), and all of them passed the stringent 288°C hot air soldering test, demonstrating excellent interfacial heat resistance and reliability. Furthermore, the excellent etching uniformity indicates that this copper foil is suitable for higher precision circuit processing.

[0087] Example 2

[0088] Study on the Influence of Metal Complexing Agent Type and Ratio on the Properties of Ultra-Low Profile Copper Foil

[0089] 1. Experimental objective: To verify the influence of different metal complexing agents and their ratios on the final performance on the specific magnetron sputtering-electroplating ultra-smooth substrate of this invention.

[0090] 2. Experimental Procedure:

[0091] Reference substrate: The ultra-low profile copper foil (rough surface R) prepared in Example 1 of this invention is used uniformly. z = 0.07 ± 0.01μm, smooth surface R z = 0.11 ± 0.01 μm).

[0092] Processing technology: Microgravure coating is used uniformly, with a coating amount of (1.0 ± 0.1) g / m², and heat curing at 140℃ for 90 seconds.

[0093] Coupling agent base solution: 4.0 wt% KH-550, 0.8 wt% aqueous polyurethane dispersion, solvent is deionized water + ethanol (7:3), pH adjusted to 9.0 with ammonia.

[0094] Variable groups: Different types and ratios of metal complexing agents were added to the base solution (each addition amount was 1.5 wt% of the total mass of the metal complexing agent). A total of 7 experimental groups were set up:

[0095] This invention uses a ratio of tin acetylacetone to zinc acetylacetone of 2:1.

[0096] Comparative Example 1: Tin acetylacetone only

[0097] Comparative Example 2: Zinc acetylacetone only

[0098] Comparative Example 3: Tin acetylacetone : Zinc acetylacetone = 1 : 2

[0099] Comparative Example 4: Tin acetylacetone : Zinc acetylacetone = 5 : 1

[0100] Comparative Example 5: Add an equimolar amount of cobalt acetylacetone

[0101] Comparative Example 6: No metal complexing enhancer added (blank control)

[0102] Comparative Example 7: Tin chloride (SnCl2): Zinc acetylacetonate = 2:1

[0103] Comparative Example 8: Tin acetylacetone: Zinc chloride (ZnCl2) = 2:1

[0104] 3. Experimental results: as shown in Table 2.

[0105] Table 2

[0106]

[0107] 4. Experimental Conclusion:

[0108] 1. The data shows that there is an optimal window (1:1 to 3:1) for the Sn to Zn ratio. Deviating from this window (Comparative Examples 3 and 4) leads to a significant decrease in performance, proving its non-obviousness. Using Sn or Zn alone (Comparative Examples 1 and 2) also fails to achieve optimal results, proving the existence of a synergistic effect.

[0109] 2. If a Co-type complexing agent is used (Comparative Example 5), the performance deteriorates sharply, even worse than the blank group, indicating that the choice of metal type is highly specific and unpredictable, and cannot be easily thought of or replaced by those skilled in the art.

[0110] 3. If Sn is introduced in the form of common inorganic salts such as chlorides... 2+ Zn2+ The addition of ions, because the resulting inorganic salts are usually strong acid-weak base salts, significantly lowers the pH of the coupling agent treatment solution (from 9.0 to acidic or near-neutral), preventing KH-550 and other agents from hydrolyzing and cross-linking properly; and Sn 2+ / Zn 2+ The ions will immediately react with OH- in the solution. - The formation of hydroxide precipitates prevents uniform distribution within the interface layer and hinders the formation of a nano-oxide-reinforced phase. Instead, it compromises the stability and film-forming properties of the treatment solution. Furthermore, residual chloride ions and other contaminants can corrode the copper foil substrate.

[0111] 4. This invention group (Sn) 2+ :Zn 2+ The peel strength (0.63 N / mm) of the 2:1 ratio was significantly higher than that of all comparative examples and the blank control group, and it passed the most stringent 288℃ heat resistance test, which fully demonstrates the outstanding substantive features and significant progress of the present invention compared with the prior art.

[0112] 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 coupling agent treatment liquid for exclusive use in an ultra-low profile copper foil, characterized by comprising: Comprise: The main coupling agent, metal complex enhancer, film forming promoter, solvent; the metal complex enhancer comprises one or more of acetylacetone tin, acetylacetone zinc; in the metal complex enhancer, the mass ratio of the acetylacetone tin, the acetylacetone zinc is 1-3: 1; the coupling agent treatment solution specially used for ultra-low profile copper foil comprises the following components by mass percentage: The main coupling agent 3-5%, The metal complex enhancer 1-2%, The film forming promoter 0.5-1%, The solvent the rest.

2. The coupling agent treatment solution for ultra-low profile copper foil according to claim 1, wherein The main coupling agent comprises an aminosilane coupling agent; the film forming promoter comprises one or more of an aqueous polyurethane dispersion and polyvinyl butyral; the solvent comprises one or more of deionized water and ethanol; the pH of the coupling agent treatment solution specially used for ultra-low profile copper foil is 8.5-9.5; the coupling agent treatment solution specially used for ultra-low profile copper foil further comprises a pH adjuster.

3. The coupling agent treatment solution for the ultra-low profile copper foil according to claim 2, wherein The main coupling agent comprises one or more of γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane and N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane; in the solvent, the volume ratio of the deionized water to the ethanol is 7:3; the pH adjuster comprises ammonia water.

4. Use of the coupling agent treatment liquid for ultra-low profile copper foil according to claim 1, characterized in that, Preparation of an ultra-low profile copper foil.

5. The use according to claim 4, wherein the compound is ###0002### Comprise the following steps: S1, substrate preparation, prepare a copper foil body; S2, the copper foil body is subjected to magnetron sputtering to form a nanocrystalline seed layer, and a sputtered copper foil is obtained; S3, the sputtered copper foil is subjected to water electroplating thickening and alloying, and an electroplated thickened copper foil is obtained; S4, the electroplated thickened copper foil is passivated, and then treated with the coupling agent treatment solution specially used for ultra-low profile copper foil, and an ultra-low profile copper foil is obtained.

6. The use according to claim 5, wherein the compound is ###00003### or a pharmaceutically acceptable salt thereof. Comprise the following steps: S1, substrate preparation, an electrolytic raw foil with a thickness of 12-18 μm is used as the copper foil body; S2, magnetron sputtering is performed on the copper foil body, a working gas including argon is introduced into a cavity with a pressure of 0.3-0.8 Pa, a pure copper target is used, and a sputtering power is applied to make a power density of 1.5-2.5 W / cm -3 2, and a copper foil after sputtering is obtained by controlling a walking speed of the copper foil body to deposit a nanoscale copper seed layer with a thickness of 50-150 nm on the surface. 2 S2, magnetron sputtering is performed on the copper foil body, a working gas including argon is introduced into a cavity with a pressure of 0.3-0.8 Pa, a pure copper target is used, and a sputtering power is applied to make a power density of 1.5-2.5 W / cm -3 2, and a copper foil after sputtering is obtained by controlling a walking speed of the copper foil body to deposit a nanoscale copper seed layer with a thickness of 50-150 nm on the surface. 2 S3, the sputtered copper foil is introduced into a copper electroplating bath, the electroplating temperature is 40-50 ℃, the cathode current density is 10-15 ASD, electroplating is performed, the total thickness of electroplating is increased to 0.3-0.6 μm, and the electroplated thickened copper foil is obtained; the copper electroplating bath comprises copper sulfate, sulfuric acid, chloride ions, nickel ions, brightener, leveling agent and deionized water; S4, passivating the electroplating thickened copper foil, and then uniformly coating a coupling agent treatment liquid for the ultra-low profile copper foil on the matte surface, with a coating amount of 0.5-1.5 g / m 2 and then performing heat treatment in an oven at 120-150°C for 1-2 minutes to obtain the ultra-low profile copper foil; the passivation method comprises one or more of zinc-chromium alloy passivation and zinc-nickel alloy passivation; the coating method comprises micro-gravure coating; S5, after cooling, the ultra-low profile copper foil is subjected to anti-oxidation post-treatment and winding.

7. The use as claimed in claim 6, characterised in that In step S3, the copper electroplating bath comprises 80-100 g / L of copper sulfate, 100-120 g / L of sulfuric acid, 50-70 ppm of chloride ions, 5-15 ppm of nickel ions, 50-200 mL / kL of brightener, 10-50 mL / kL of leveling agent and the rest of deionized water.

8. An ultra-low profile copper foil obtained by the application of claim 4.

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