Electrolytic copper foil with low roughness and preparation method and application thereof

Abstract

The invention belongs to the technical field of copper foil preparation, and particularly relates to a preparation method and application of a low-roughness electrolytic copper foil. A roughening liquid system taking guar gum and sodium tungstate as additives and a curing liquid system taking polyethylene glycol and antimony pentoxide as additives are adopted, so that the surface roughness of the copper foil is remarkably reduced, the high normal peeling strength of the copper foil is effectively ensured, the degradation rate of the peeling strength after heat resistance is reduced, and the service life of the copper foil is prolonged. Therefore, the polyphenyl ether-based copper-clad plate has more excellent application performance in high-end polyphenyl ether-based copper-clad plates.

Description

Technical Field

[0001] This invention belongs to the field of copper foil preparation technology, specifically relating to a low-roughness electrolytic copper foil, its preparation method, and its application. Background Technology

[0002] High-frequency, high-speed digital applications require conductor signal integrity, which necessitates copper foil with low profile and no magnetic components.

[0003] As one of the three core substrates of copper clad laminate (CCL), copper foil plays a crucial role in printed circuit board (PCB) manufacturing. This conductive medium, used for signal and power transmission between electronic components, is often hailed as the "neural network system" of modern electronic devices due to its excellent electrical conductivity. With the increasing demands from industries such as 5G, smartphones, AI, and electric vehicles, and the continuous development of the electronics industry, the demand for high-speed products is constantly increasing, leading to higher requirements for low-signal-loss circuitry. This places higher demands on the various physical properties of the copper foil on the surface of CCLs. According to Moore's Law, the exponential growth in computing power demand is driving the iterative upgrade of high-frequency, high-speed signal transmission technologies. In application scenarios where signal frequencies exceed GHz levels, the skin effect causes approximately 80% of the current density to concentrate within a 0.5μm depth range on the conductor surface, posing stringent requirements on the surface characteristics of the copper foil in PCB substrates. The industry generally adopts the method of reducing the roughness (Rz value) of copper foil to improve signal integrity. However, when the roughness is reduced to below 1μm, the copper nodule structure of traditional electrolytic copper foil is significantly reduced, resulting in a decrease in peel strength of about 40%. This contradictory relationship between mechanical and electrical properties has become a key bottleneck restricting the reliability of high-end electronic products.

[0004] Currently, copper foils used in high-speed applications face numerous problems. Their roughness is relatively high, and the copper nodules on the treated surface not only have poor morphology but also poor uniformity. These conditions lead to a series of adverse consequences, such as unstable peel resistance and poor compatibility with polyphenylene oxide (PPO) substrates. To address these challenges, most existing technologies employ methods that reduce the current during production. While this reduces the roughness of the copper foil, it also decreases the number of copper nodules and further worsens uniformity. Ultimately, this results in low peel resistance of the copper foil in high-speed substrates, negatively impacting both stability and electrical properties.

[0005] Patent No. CN202411041873.7 discloses an electrolytic copper foil with a roughness of less than 1.0 μm, its preparation method, and its applications. The preparation method includes: an electrolyte containing a raw foil additive; a roughening solution containing a roughening additive, namely sodium tungstate 30–60 mg / L; and a curing solution containing curing additives, namely sodium 3-mercapto-1-propanesulfonate 5.0–10.0 mg / L, hydroxyethyl cellulose 5.0–10.0 mg / L, polyethylene glycol (PEG) 5.0–10.0 mg / L, and polyethyleneimine 5.0–10.0 mg / L. The electrolytic copper foil prepared by this invention does not contain ferromagnetic materials, has a rough surface roughness Rz ≤ 0.8 μm, a smooth surface roughness Rz ≤ 1.5 μm, and a peel strength ≥ 0.6 N / mm, and can be used in the processing of PCBs and copper-clad laminates in high-frequency applications.

[0006] However, the above methods still cannot meet the requirements for copper foil with low roughness and high peel strength, especially in applications with polyphenylene oxide (PPO) substrates. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a low-roughness electrolytic copper foil and its preparation method.

[0008] To achieve the above objectives, the specific preparation method of the present invention is as follows: (1) Pickling treatment: The purpose of this step is to remove the oxide layer, oil and other contaminants from the surface of the original copper foil, exposing a clean and easy-to-handle copper surface. This ensures that the subsequent roughening treatment can be carried out uniformly, forming a roughened layer with good adhesion.

[0009] (2) Roughening treatment: A roughening solution is used, which includes copper sulfate, sulfuric acid, pure water, and additive A. The copper ion concentration is 18–24 g / L, the sulfuric acid concentration is 75–135 g / L, and additive A includes sodium tungstate and guar gum. The sodium tungstate concentration is 5–20 mg / L, and the guar gum concentration is 0.5–2 g / L. The temperature of the roughening solution is 20–30 °C, the current density is 30–50 A / dm², and the electroplating time is 0.5–5 s. The purpose of this step is to rapidly and densely deposit tiny copper nodules. High current density and short time are the key process parameters for achieving fine and uniform nodules. This complements the role of the additives in the treatment solution, working together to achieve the goal of "low roughness" but "high specific surface area".

[0010] Sodium tungstate, as a grain refiner, can adsorb onto the surface of copper foil, increasing electrochemical polarization and resulting in more and finer copper deposition nuclei, thus forming smaller, denser, and more uniform roughened nodules. This is key to achieving low roughness (small and numerous nodules), rather than the traditional large and sparse nodules. Guar gum, a polymeric inhibitor, can form an adsorption film on the cathode surface, hindering the free deposition of copper ions. Working synergistically with sodium tungstate, it further refines the grains and makes the nodules more rounded and uniform in shape, preventing the formation of dendrites or overly sharp protrusions.

[0011] (3) Curing treatment: A curing solution is used, which includes copper sulfate, sulfuric acid, pure water, and additive B. The copper ion concentration is 55–60 g / L, the sulfuric acid concentration is 80–90 g / L, and additive B includes antimony pentoxide and polyethylene glycol. The antimony ion concentration is 50–100 mg / L, and the polyethylene glycol concentration is 5–10 g / L. The curing solution temperature is 30–36 °C, and the current density is 10–20 A / dm³. 2 The electroplating time is 0.5–5 seconds; the purpose of this step is to electroplat on the roughened nodules using a curing solution and a relatively low current density. The lower current density allows for more controlled and denser deposition.

[0012] Antimony pentoxide, as a brightener and leveling agent, can co-deposit with copper ions, altering the deposition habits of copper and resulting in a denser, smoother copper layer. This further reduces overall roughness and increases the tensile strength of the copper foil. Polyethylene glycol, acting as a carrier and inhibitor, typically works synergistically with antimony ions to refine the grains of the electrodeposited layer through surface adsorption, ensuring a uniform and defect-free cured layer and enhancing the mechanical strength of the nodules.

[0013] (4) Surface anti-oxidation and silanization treatment to obtain electrolytic copper foil with low roughness.

[0014] Furthermore, a sulfuric acid solution with a temperature of 10–50°C is used. Sulfuric acid is used to ensure compatibility with the subsequent electroplating solution system and to avoid introducing impurity ions.

[0015] Furthermore, the concentration of sodium tungstate is 5–18 mg / L, and the concentration of guar gum is 1–2 g / L.

[0016] Furthermore, the concentration of antimony ions is 70–85 mg / L, and the concentration of polyethylene glycol is 6–8 g / L.

[0017] Furthermore, the temperature of the roughening treatment solution was 25°C, and the current density was 35 A / dm³. 2 The electroplating time is 1 to 2 seconds.

[0018] Furthermore, the temperature of the curing solution is 35℃, the current density is 12A / dm², and the electroplating time is 1-2s.

[0019] The present invention also discloses a low-roughness electrolytic copper foil prepared according to the above method. The prepared copper foil was tested after hot-pressing with a polyphenylene oxide (PPO) substrate, and it was found to have excellent roughness and peel strength, making it suitable for the preparation of resin-based copper clad laminates, especially polyphenylene oxide (PPO) resin-based copper clad laminates.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. By using a roughening solution system with guar gum and sodium tungstate additives, and with appropriate current and electroplating time, the controllable growth of copper nodule structures on the surface of copper foil was achieved. Tungsten ions in the roughening solution caused the copper nodules to grow into needle-like shapes, and guar gum further maintained this shape, increasing the contact area and bonding strength between the copper foil and the resin substrate.

[0021] 2. A curing liquid system using polyethylene glycol and antimony pentoxide additives is adopted. Antimony ions and polyethylene glycol further fill the uneven surface at the bottom of the copper nodule, reduce the roughness of the copper foil, and improve the electrical transport performance of the copper foil. Attached Figure Description

[0022] Figure 1 This is a scanning electron micrograph of the nano-copper nodules prepared in Example 7 of this invention; Figure 2 This is a scanning electron micrograph of the nano-copper nodules prepared in Comparative Example 1 of the present invention; Figure 3 This is a scanning electron micrograph of the nano-copper nodules prepared in Comparative Example 2 of the present invention; Figure 4 This is a scanning electron micrograph of the nano-copper nodules prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0023] The invention can be further understood through the specific embodiments and comparative embodiments given below. However, they are not intended to limit the invention.

[0024] Example 1 (1) Pickling treatment The 0.9 μm raw foil was acid-washed in an aqueous sulfuric acid solution at 30 °C.

[0025] (2) Roughening treatment After being acid-washed, the copper foil was placed in a roughening solution at a temperature of 25°C. The solution contained 20 g / L copper ions, 100 g / L sulfuric acid, 5 mg / L tungsten ions, and 1 g / L guar gum. The roughening current was 35 A / dm², and the electroplating time was 1 s, resulting in roughened electrolytic copper foil.

[0026] (3) Curing treatment After the roughened copper foil is washed with water, it is placed in a curing solution. The curing solution temperature is 35℃, the copper ion concentration in the solution is 57g / L, the sulfuric acid concentration is 80g / L, the antimony ion concentration is 70mg / L, the polyethylene glycol concentration is 6g / L, the curing current is 12A / dm², and the electroplating time is 1s, thus obtaining the cured electrolytic copper foil.

[0027] (4) Surface anti-oxidation treatment and silanization treatment After the cured copper foil is pickled, it undergoes anti-oxidation treatment by nickel plating, zinc plating and chromium plating. Finally, KBM603 silane is uniformly sprayed onto the copper foil to obtain low-roughness electrolytic copper foil.

[0028] Example 2 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 5 mg / L and the concentration of guar gum is 1.5 g / L; the concentration of antimony ions in additive B is 85 mg / L and the concentration of polyethylene glycol is 7 g / L. After electroplating, a low-roughness copper foil is obtained.

[0029] Example 3 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 5 mg / L and the concentration of guar gum is 2 g / L; the concentration of antimony ions in additive B is 75 mg / L and the concentration of polyethylene glycol is 8 g / L. After electroplating, a low-roughness copper foil is obtained.

[0030] Example 4 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 10 mg / L and the concentration of guar gum is 1 g / L; the concentration of antimony ions in additive B is 85 mg / L and the concentration of polyethylene glycol is 8 g / L. After electroplating, a low-roughness copper foil is obtained.

[0031] Example 5 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 10 mg / L and the concentration of guar gum is 1.5 g / L; the concentration of antimony ions in additive B is 75 mg / L and the concentration of polyethylene glycol is 6 g / L. After electroplating, a low-roughness copper foil is obtained.

[0032] Example 6 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 10 mg / L and the concentration of guar gum is 2 g / L; the concentration of antimony ions in additive B is 70 mg / L and the concentration of polyethylene glycol is 7 g / L. After electroplating, a low-roughness copper foil is obtained.

[0033] Example 7 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 15 mg / L and the concentration of guar gum is 1 g / L; the concentration of antimony ions in additive B is 75 mg / L and the concentration of polyethylene glycol is 7 g / L. After electroplating, a low-roughness copper foil is obtained.

[0034] Example 8 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 15 mg / L and the concentration of guar gum is 1.5 g / L; the concentration of antimony ions in additive B is 70 mg / L and the concentration of polyethylene glycol is 8 g / L. After electroplating, a low-roughness copper foil is obtained.

[0035] Example 9 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 15 mg / L and the concentration of guar gum is 2 g / L; the concentration of antimony ions in additive B is 85 mg / L and the concentration of polyethylene glycol is 6 g / L. After electroplating, a low-roughness copper foil is obtained.

[0036] Comparative Example 1 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 0 mg / L and the concentration of guar gum is 0 g / L; the concentration of antimony ions in additive B is 85 mg / L and the concentration of polyethylene glycol is 6 g / L. After electroplating, a low-roughness copper foil is obtained.

[0037] Comparative Example 2 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 10 mg / L and the concentration of guar gum is 1 g / L; the concentration of antimony ions in additive B is 0 mg / L and the concentration of polyethylene glycol is 0 g / L. After electroplating, a low-roughness copper foil is obtained.

[0038] Comparative Example 3 The preparation process is basically the same as in Example 1, except that in steps 2 and 3, the concentration of tungsten ions in additive A is 0 mg / L and the concentration of guar gum is 0 g / L; the concentration of antimony ions in additive B is 0 mg / L and the concentration of polyethylene glycol is 0 g / L. After electroplating, a low-roughness copper foil is obtained.

[0039] Performance testing: The low-roughness electrolytic copper foils prepared in each example and comparative example were subjected to high-temperature pressing with PPO substrate (first stage: 30℃, 7psi, 40min; second stage: 200℃, 20psi, 120min; third stage: 30℃, 15psi, 20min). The peel strength (refer to national standard GB / T29847-2013-7.3.3.2) and heat resistance (refer to national standard GB / T29847-2013-7.3.3.3) were evaluated. The specific values ​​are listed in Table 1 below.

[0040] Table 1 Rz Ra Normal peel strength (N / mm) Peel strength (N / mm) after 10 minutes of tin bleaching Recession rate % Example 1 1.323 0.551 0.712 0.621 12.80% Example 2 1.217 0.535 0.682 0.604 11.40% Example 3 1.304 0.527 0.691 0.603 12.70% Example 4 1.261 0.503 0.681 0.601 11.70% Example 5 1.263 0.512 0.702 0.625 11.00% Example 6 1.211 0.527 0.723 0.64 11.50% Example 7 1.053 0.418 0.77 0.694 9.90% Example 8 1.103 0.446 0.71 0.650 8.40% Example 9 1.136 0.453 0.701 0.617 12.00% Comparative Example 1 1.078 0.428 0.633 0.556 12.20% Comparative Example 2 1.355 0.546 0.693 0.626 9.70% Comparative Example 3 1.423 0.581 0.609 0.554 9.10% As shown in Table 1, the electrolytic copper foil prepared by this invention has a surface roughness (Rz) ≤ 1.35 μm, a surface roughness (Ra) ≤ 0.55 μm, a normal peel strength ≥ 0.65 N / mm, a peel strength after 10 min of tin bleaching ≥ 0.60 N / mm, and a degradation rate ≤ 13%. The electrolytic copper foil prepared by this invention significantly reduces the surface roughness of the copper foil while effectively ensuring its high normal peel strength and high heat-resistant peel strength, thus giving it superior applicability in high-end polyphenylene ether-based copper clad laminates.

[0041] As can be seen from Table 1, the overall performance of Examples 1-9 is better than that of Comparative Examples 1-3.

[0042] Comparing the data in Table 1, it can be seen that the electrolytic copper foil prepared in Example 7 exhibits the highest peel strength and better heat resistance on the polyphenylene oxide (PPO) substrate. Furthermore, this copper foil has low roughness, and combined with the skin effect, it indicates excellent electrical transport properties. The table shows a strong correlation between roughness and the additives used in roughening and curing. Increasing the antimony ion concentration lowers the roughness but results in finer copper nodules. Peel strength (PS) is strongly correlated with the roughening additives; adding tungsten ions at 15 mg / L improves peel strength. Simultaneous addition during roughening and curing may cause more complex effects; therefore, it is necessary to balance the additive dosage to obtain a copper foil with low roughness and high peel resistance. Obtaining a low-roughness copper foil while maintaining high normal peel strength (PS) reduces the rate of degradation after heat resistance, allowing for better application in high-end PPO substrates.

[0043] Comparing Example 7, Example 1, and Control Example 1, it can be seen that higher levels of cured guar gum and antimony ions significantly reduce the surface roughness of the copper foil. From Example 1... Figure 1 Compared with Example 1 Figure 2 It can be seen that tungsten ions and guar gum can significantly increase the length of copper nodules, keep the nodules columnar, and make the nodules more dispersed with less aggregation.

[0044] Comparative Example 7 Figure 1Compared with Example 2 Figure 3 It can be seen that the roughness is significantly reduced after curing, and the cured copper nodules are slightly larger, exhibiting a better cylindrical shape. The cylindrical copper nodules also show better anti-peeling and heat resistance after pressing.

[0045] Comparative Example 7 Figure 1 Compare with Example 1 Figure 2 Compare with Example 2 Figure 3 Compared with Example 3 Figure 3 The copper foil without additives A and B exhibits a distinctly rounded shape and a large size with high roughness, but this copper nodule does not provide better peel resistance in polyphenylene oxide (PPO) substrates.

[0046] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A roughening treatment liquid comprising copper sulfate, sulfuric acid, pure water, and an additive A, characterized in that, The copper ion concentration is 18-24 g / L, the sulfuric acid concentration is 75-135 g / L, the additive A includes sodium tungstate and guar gum, the sodium tungstate concentration is 5-20 mg / L, and the guar gum concentration is 0.5-2 g / L.

2. The roughening treatment liquid according to claim 1, characterized by The sodium tungstate concentration is 5-18 mg / L, and the guar gum concentration is 1-2 g / L.

3. A curing treatment liquid comprising copper sulfate, sulfuric acid, pure water, and an additive B, characterized in that, The copper ion concentration is 55-60 g / L, the sulfuric acid concentration is 80-90 g / L, the additive B includes antimony pentoxide and polyethylene glycol, the antimony ion concentration is 50-100 mg / L, and the polyethylene glycol concentration is 5-10 g / L.

4. The curing treatment liquid according to claim 3, characterized by The antimony ion concentration is 70-85 mg / L, and the polyethylene glycol concentration is 6-8 g / L.

5. A method for producing an electrolytic copper foil having low roughness, characterized by, The method comprises the following steps: (1) acid pickling treatment; (2) roughening treatment, using the roughening treatment solution of claim 1 or 2, the temperature is 20-30 ℃, the current density is 30-50 A / dm², and the electroplating time is 0.5-5 s; (3) solidification treatment, using the solidification treatment solution of claim 3 or 4, the temperature is 30-36 ℃, the current density is 10-20 A / dm², and the electroplating time is 0.5-5 s; (4) surface anti-oxidation and silanization treatment, to obtain a low-roughness electrolytic copper foil.

6. The method of producing a low-roughness electrolytic copper foil according to claim 5, wherein The step (1) acid pickling treatment uses a sulfuric acid solution, and the temperature is 10-50 ℃.

7. The method of producing a low-roughness electrolytic copper foil according to claim 5, wherein The step (2) roughening treatment uses a roughening treatment solution, the temperature is 25 ℃, the current density is 35 A / dm², and the electroplating time is 1-2 s.

8. The method of producing a low-roughness electrolytic copper foil according to claim 5, wherein The step (3) solidification treatment uses a solidification treatment solution, the temperature is 35 ℃, the current density is 12 A / dm², and the electroplating time is 1-2 s.

9. An electrolytic copper foil having a low roughness, characterized in that, Prepared by the method of any one of claims 5 to 8.

10. Use of the low-roughness electrolytic copper foil according to claim 9 in a polyphenylene oxide (PPO) substrate.

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