Ultralow-profile RTF copper foil surface treatment process

Abstract

The invention relates to the technical field of electrolytic copper foil processing, and particularly provides an ultra-low profile RTF copper foil surface treatment process which comprises the following steps of acid pickling, coarsening, curing, ashing, passivation, anti-oxidation, silanization and drying, and a coarsening additive is one or a mixture of two of NaWO4, NaMoO4, D-sodium gluconate and trisodium citrate. Through alternate circulation of multiple roughening and curing processes, the bonding force between crystal grains and the surface of the copper foil is remarkably enhanced, the copper powder falling phenomenon is thoroughly eliminated, and the anti-stripping strength is higher; the reverse copper foil prepared by the production process provided by the invention has ultra-low profile tolerance, the roughened surface Rz is less than or equal to 1.8 mu m, and the peel strength is more than or equal to 0.5 N / mm. The roughness is reduced on the basis of maintaining the peel strength of the copper foil, so that the obtained electrolytic copper foil is more beneficial to high-frequency signal transmission, and the applicability is wider.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic copper foil processing, and in particular to a surface treatment process for an ultra-low profile RTF copper foil. Background Art

[0002] Electrolytic copper foil, a core material for copper-clad laminates (CCLs) and printed circuit boards (PCBs), is also a key component of the negative electrode current collector in lithium-ion batteries, playing an irreplaceable role in the electronics and electrical appliance industry. In PCB manufacturing, the copper foil must be tightly bonded to the resin substrate through a lamination process. This bonding strength directly determines the reliability of the circuit board under thermal and mechanical stress. In traditional processes, the matte side of the electrolytic copper foil is directly bonded to the substrate to provide sufficient peel strength, while the smooth side (low-roughness side) requires surface treatment (such as roughening and curing) to enhance bonding strength.

[0003] In existing technology, copper foil polishing typically involves pickling, roughening, curing, and anti-oxidation steps. The roughening and curing process involves coating the polished surface with a thin layer of copper and oxide to control surface roughness and enhance bonding strength. However, this process has significant drawbacks: uneven grain size distribution during the roughening process leads to high surface roughness; excessive pursuit of low roughness can compromise peel strength, impacting the long-term reliability of the circuit board; and it can lead to weak bonding and easy detachment of grains, further exacerbating performance fluctuations.

[0004] Therefore, it is necessary to provide an ultra-low profile RTF copper foil surface treatment process to solve the above technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the electroplating method currently used for copper foil in the prior art causes the copper foil to have poor grain uniformity, high surface roughness and weak peeling strength.

[0006] To achieve the above object, the technical solution of the present invention is: a surface treatment process for ultra-low profile RTF copper foil, comprising the following steps: pickling, roughening, curing, ashing, passivation, anti-oxidation, silanization and drying; Step A: Pickling treatment: pickling the electrolytic copper foil to be treated in a pickling solution, wherein the H⁺ concentration is 100-150g / L, the Cu²⁺ concentration is 8-15g / L, and the temperature is 30-40°C; Step B: Roughening electroplating: electroplating the original foil in a roughening electrolyte at a current density of 10-15A / dm² and a temperature of 40-50°C. The roughening electrolyte contains H⁺ concentration of 130-150g / L, Cu²⁺ concentration of 10-20g / L, and Cl⁻ concentration of 2-10mg / L. A roughening additive is added at a concentration of 10-15mg / L. Step C: Curing electroplating: The original foil is electroplated in a curing electrolyte with a current density of 20-30A / dm2 and a temperature of 40-50°C. The H⁺ concentration in the curing electrolyte is 100-120g / L, the Cu²⁺ concentration is 50-60g / L, and the Cl⁻ concentration is 5-10mg / L. Step D: Repeat steps B and C or alternate 3-5 times; Step E: Ashing electroplating: The original foil is electroplated in an ashing electrolyte with a current density of 0.5-0.75 A / dm2 and a temperature of 40-50°C. The ashing electrolyte contains 0.65±0.5 g / L Ni²⁺, 2.0±0.5 g / L Zn²⁺, 85±10 g / L K₄P₂Oₐ, and a pH of 10±0.3. Step F: Passivation plating: electroplating the original foil in a passivation electrolyte with a current density of 0.5-0.75A / dm2 and a temperature of 40-50°C. 6 ⁺The concentration is 1.7±0.5g / L and the NaOH concentration is 11±1.5g / L; Step G: Silane spray oxidation: temperature 25-35°C, organic film coupling agent concentration 500-700 ppm; Step H: Drying: Drying at a temperature of 180-220°C.

[0007] Preferably, the roughening additive used in step B is selected from one or a mixture of two of NaWO4, NaMoO4, sodium D-gluconate, and trisodium citrate.

[0008] Preferably, the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0009] Preferably, the thickness of the electrolytic copper foil is 15-35 μm.

[0010] Preferably, the initial roughness Rz of the smooth surface of the original electrolytic copper foil is ≤0.5 μm.

[0011] Compared with related technologies, the ultra-low profile RTF copper foil surface treatment process provided by the present invention has the following beneficial effects: 1. The present invention significantly enhances the bonding force between the grains and the copper foil surface through multiple alternating cycles of roughening and curing processes, completely eliminates the copper powder shedding phenomenon, and has higher peeling strength.

[0012] The present invention optimizes parameters based on existing production lines, without the need for new equipment or complex process modifications. The target performance can be achieved through the coordinated regulation of the electrolyte formula and process steps, significantly reducing production costs and implementation barriers.

[0013] The reverse copper foil multiple roughening and curing process method of the present invention is simple, easy to operate, and suitable for batch production.

[0014] The reverse copper foil prepared by the production process provided by the present invention has an ultra-low profile, a roughened surface Rz ≤ 1.8 μm, and a peel strength ≥ 0.5 N / mm. The present invention reduces the roughness while maintaining the peel strength of the copper foil, making the obtained electrolytic copper foil more conducive to high-frequency signal transmission and more widely applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Example 1 of the present invention; Figure 2 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Example 2 of the present invention; Figure 3 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Example 3 of the present invention; Figure 4 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Comparative Example 1 of the present invention; Figure 5 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Comparative Example 2 of the present invention; Figure 6 This is a SEM image of the smooth surface of the electrolytic copper foil after surface treatment in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] The present invention provides an ultra-low profile RTF copper foil surface treatment process, comprising the following steps: pickling, roughening, curing, ashing, passivation, anti-oxidation, silanization and drying; Step A: Pickling treatment: pickling the electrolytic copper foil to be treated in a pickling solution, wherein the H⁺ concentration is 100-150g / L, the Cu²⁺ concentration is 8-15g / L, and the temperature is 30-40°C; Step B: Roughening electroplating: electroplating the original foil in a roughening electrolyte at a current density of 10-15A / dm² and a temperature of 40-50°C. The roughening electrolyte contains H⁺ concentration of 130-150g / L, Cu²⁺ concentration of 10-20g / L, and Cl⁻ concentration of 2-10mg / L. A roughening additive is added at a concentration of 10-15mg / L. The roughening additive used in step B is selected from one or a mixture of two of NaWO4, NaMoO4, sodium D-gluconate, and trisodium citrate.

[0018] Step C: Curing electroplating: The original foil is electroplated in a curing electrolyte with a current density of 20-30A / dm2 and a temperature of 40-50°C. The H⁺ concentration in the curing electrolyte is 100-120g / L, the Cu²⁺ concentration is 50-60g / L, and the Cl⁻ concentration is 5-10mg / L. Step D: Repeat steps B and C or alternate 3-5 times; Step E: Ashing electroplating: The original foil is electroplated in an ashing electrolyte with a current density of 0.5-0.75 A / dm2 and a temperature of 40-50°C. The ashing electrolyte contains 0.65±0.5 g / L Ni²⁺, 2.0±0.5 g / L Zn²⁺, 85±10 g / L K₄P₂Oₐ, and a pH of 10±0.3. Step F: Passivation plating: electroplating the original foil in a passivation electrolyte with a current density of 0.5-0.75A / dm2 and a temperature of 40-50°C. 6 ⁺The concentration is 1.7±0.5g / L and the NaOH concentration is 11±1.5g / L; Step G: Silane spray oxidation: temperature 25-35 ° C, organic film coupling agent concentration 500-700 ppm; the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane Step H: Drying: Drying at a temperature of 180-220°C.

[0019] The thickness of the original electrolytic copper foil is 15-35 μm, and the initial roughness Rz of the smooth surface of the original electrolytic copper foil is ≤ 0.5 μm.

[0020] Example 1: The surface treatment process includes the following steps in sequence: pickling, roughening, curing, roughening, curing, roughening, curing, roughening, curing, ashing, passivation, silanization and drying.

[0021] The conditions of the pickling step were: temperature 30 °C, H+ concentration 106.30 g / L, and Cu2+ concentration 10.58 g / L; The conditions for the roughening step were: current density 12.5 A / dm2, temperature 45 °C, Cu2+ concentration 13.97 g / L, H+ concentration 137.76 g / L, Cl- concentration 7.21 mg / L, and NaWO4 concentration 10.38 mg / L; The curing step conditions were: current density 23 A / dm2, temperature 40 ℃, Cu2+ concentration 61.81 g / L, H+ concentration 102.50 g / L, and Cl- concentration 6.39 mg / L.

[0022] The above-mentioned roughing / solidification process steps are repeated four times alternately for roughening and solidification, with the conditions remaining unchanged.

[0023] The conditions of the ashing step are: current density 0.5-0.75 A / dm2, temperature 40 ℃, Ni2+ concentration 0.65±0.5g / L, Zn2+ concentration 2.0±0.5g / L, K4P2O7 concentration 85±10g / L, pH: 10±0.3L.

[0024] The passivation step conditions were: current density 23 A / dm2, temperature 40 ℃, Cr6+ concentration 1.7±0.5g / L, and NaOH concentration 11±1.5g / L.

[0025] The process conditions for silane spraying are as follows: temperature 25°C, organic film coupling agent concentration 624 mg / L; the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane; The temperature used in the drying process is 180 ° C. The scanning electron microscope image of the copper foil after the surface treatment method of this scheme is as follows: Figure 1 shown.

[0026] Example 2: The surface treatment process includes the following steps: pickling, roughening, curing, roughening, curing, roughening, curing, roughening, curing, roughening, curing, ashing, passivation, silanization and drying. The process flow chart is as follows.

[0027] The conditions of the pickling step were: temperature 34 °C, H+ concentration 108.92 g / L, Cu2+ concentration 10.9 g / L; The conditions for the roughening step were: current density 12.5 A / dm2, temperature 43 °C, Cu2+ concentration 14.94 g / L, H+ concentration 140.05 g / L, Cl- concentration 8.92 mg / L, and NaWO4 concentration 10.25 mg / L; The curing step conditions were: current density 23 A / dm2, temperature 40 °C, Cu2+ concentration 60.39 g / L, H+ concentration 100.95 g / L, and Cl- concentration 6.41 mg / L.

[0028] The above-mentioned roughing / solidification process steps are repeated five times alternately for roughening and solidification, with the conditions remaining unchanged.

[0029] The conditions of the ashing step are: current density 0.5-0.75 A / dm2, temperature 40 ℃, Ni2+ concentration 0.65±0.5g / L, Zn2+ concentration 2.0±0.5g / L, K4P2O7 concentration 85±10g / L, pH: 10±0.3L.

[0030] The passivation step conditions were: current density 23 A / dm2, temperature 40 ℃, Cr6+ concentration 1.7±0.5g / L, and NaOH concentration 11±1.5g / L.

[0031] The process conditions for silane spraying are as follows: temperature 25°C, organic film coupling agent concentration 656 mg / L; the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane; The temperature used in the drying process is 180 ° C. The copper foil treated by the surface treatment method of this scheme is as follows Figure 2 shown.

[0032] Example 3: The surface treatment process includes the following steps: pickling, roughening, roughening, roughening, roughening, roughening, roughening, curing, curing, curing, curing, curing, ashing, passivation, silanization and drying. The process flow chart is as follows.

[0033] The conditions of the pickling step were: temperature 33 °C, H+ concentration 106.33 g / L, Cu2+ concentration 11.02 g / L; The conditions for the roughening step were: current density 12.5 A / dm2, temperature 42 °C, Cu2+ concentration 13.82 g / L, H+ concentration 141.12 g / L, Cl- concentration 8.56 mg / L, and NaWO4 concentration 9.97 mg / L; The curing step conditions were: current density 23 A / dm2, temperature 40 °C, Cu2+ concentration 59.8 g / L, H+ concentration 100.70 g / L, and Cl- concentration 7.70 mg / L.

[0034] The roughing / solidification process steps were repeated five times for each of the roughening and solidification processes, with the conditions remaining unchanged.

[0035] The conditions of the ashing step are: current density 0.5-0.75 A / dm2, temperature 40 ℃, Ni2+ concentration 0.65±0.5g / L, Zn2+ concentration 2.0±0.5g / L, K4P2O7 concentration 85±10g / L, pH: 10±0.3L.

[0036] The passivation step conditions were: current density 23 A / dm2, temperature 40 ℃, Cr6+ concentration 1.7±0.5g / L, and NaOH concentration 11±1.5g / L.

[0037] The process conditions for silane spraying are: temperature 25°C, organic film coupling agent concentration 632 mg / L; the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane; The temperature used in the drying process is 180 ° C. The copper foil treated by the surface treatment method of this scheme is as follows Figure 3 shown.

[0038] Comparative Example 1: The operation and steps are the same as those in Example 1, but the roughening and curing treatments are not performed. The copper foil treated by the surface treatment method of this solution is as follows: Figure 4 shown.

[0039] Comparative Example 2: The operation and steps are the same as those in Example 2, but only the roughening treatment is not performed. The copper foil treated by the surface treatment method of this scheme is as follows: Figure 5 shown.

[0040] Comparative Example 3: The operation and steps are the same as those in Example 3, but the curing treatment is not performed. The copper foil treated by the surface treatment method of this scheme is as follows: Figure 6 shown.

[0041] The morphology, roughness and tensile strength of the copper foil treated surfaces of Examples 1, 2, 3 and Comparative Examples 1, 2, 3 were tested as follows: Detection method: Use scanning electron microscope to observe the morphology of copper foil surface and copper grain size. The specific test results are shown in Figure 1-6 The peel strength of copper foil was tested according to the method disclosed in IPC-TM-650 2.4.8. The thickness of the copper foil used for the test was 18 μm. The Rz value of the treated surface was measured using an SJ-210 roughness meter. The specific test results are shown in Table 1 below.

[0042] Table 1 Surface roughness and tensile strength of electrolytic copper foil after surface treatment in Examples 1-3 and Comparative Examples 1-3 From the scanning electron microscope, it can be seen that Figure 4 The copper foil without roughening and curing treatment (Comparative Example 1) has a smooth surface and no copper grains. Figure 5 This is an SEM image of the smooth surface of the electrolytic copper foil after surface treatment without roughening treatment (Comparative Example 2). Grains with an average diameter of about 200 nm are evenly distributed on the surface of the copper foil. Figure 6 This is an SEM image of the smooth surface of the electrolytic copper foil after surface treatment without curing treatment (Comparative Example 3). The copper foil surface is electroplated with grains of uneven diameter, with a diameter distribution of 150-300 nm. In addition, larger grains formed by the stacking of multiple small-sized grains can be observed, thereby enhancing the roughness. Figure 1This is the SEM image of the smooth surface of the copper foil after only three roughening-curing (Example 1). The copper grains are more stacked and the size is significantly increased. The copper foil after five roughening-curing (Example 2) is as follows: Figure 2 As shown, the copper grain size is further enhanced and the roughness is increased compared with Example 1. Figure 3 This is an SEM image of the treated surface of the copper foil that was first roughened five times and then solidified five times (Example 3). Compared with Examples 1-2, it can be seen that multiple roughening treatments and then solidification treatments can effectively reduce the copper grain size and reduce the roughness without significantly reducing the peel strength.

[0043] The roughness of the treated surface of the electrolytic copper foil prepared in Examples 1-3 is significantly improved compared with that of Comparative Examples 1-3, indicating that the electrolytic copper foil prepared in the present invention can ensure that the peel strength is ≥0.5 N / mm, and the roughened surface Rz is ≤1.8 μm, that is, the roughness is reduced without reducing the peel strength, making the obtained electrolytic copper foil more conducive to high-frequency signal transmission and more widely applicable.

[0044] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. An ultra-low profile RTF copper foil surface treatment process, characterized by: The following steps are involved: Pickling, roughening, curing, ashing, passivation, anti-oxidation, silanization and drying; Step A: Pickling treatment: pickling the electrolytic copper foil to be treated in a pickling solution, wherein the H⁺ concentration is 100-150g / L, the Cu²⁺ concentration is 8-15g / L, and the temperature is 30-40°C; Step B: Roughening electroplating: The original foil is electroplated in a roughening electrolyte with a current density of 10-15 A / dm² and a temperature of 40-50°C. The roughening electrolyte contains 130-150 g / L H⁺, 10-20 g / L Cu²⁺, and 2-10 mg / L Cl⁻. A roughening additive is added at a concentration of 10-15 mg / L. Step C: Curing electroplating: The original foil is electroplated in a curing electrolyte with a current density of 20-30A / dm2 and a temperature of 40-50°C. The H⁺ concentration in the curing electrolyte is 100-120g / L, the Cu²⁺ concentration is 50-60g / L, and the Cl⁻ concentration is 5-10mg / L. Step D: Repeat steps B and C or alternate 3-5 times; Step E: Ashing electroplating: The original foil is electroplated in an ashing electrolyte with a current density of 0.5-0.75 A / dm2 and a temperature of 40-50°C. The ashing electrolyte contains 0.65±0.5 g / L Ni²⁺, 2.0±0.5 g / L Zn²⁺, 85±10 g / L K₄P₂Oₐ, and a pH of 10±0.

3. Step F: Passivation plating: electroplating the original foil in a passivation electrolyte with a current density of 0.5-0.75A / dm2 and a temperature of 40-50°C. 6 ⁺The concentration is 1.7±0.5g / L and the NaOH concentration is 11±1.5g / L; Step G: Silane spray oxidation: temperature 25-35°C, organic film coupling agent concentration 500-700 ppm; Step H: Drying: Drying at a temperature of 180-220°C.

2. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: The roughening additive used in step B is selected from one or a mixture of two of NaWO4, NaMoO4, sodium D-gluconate, and trisodium citrate.

3. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step G, the organic film coupling agent is γ-glycidyloxypropyltrimethoxysilane.

4. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: The thickness of the electrolytic copper foil is 15-35 μm.

5. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: The initial roughness Rz of the smooth surface of the original electrolytic copper foil is ≤0.5 μm.

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