A method for improving copper plating on the surface of a HVLP copper foil

Abstract

The present application relates to a kind of methods for improving the surface copper plating of HVLP copper foil, comprising the following steps: preparing the surface treatment process specific process flow in electrolytic copper foil process is as follows: pickling, first roughening, first solidification, second roughening, second solidification, blackening, graying, passivation, silane, drying;Wherein, in the first roughening using silver plating roll, in the second roughening using hastelloy roll;Pulse current is used in the second roughening time.This application realizes the synergistic optimization of surface coating adhesion, uniformity and low profile characteristics of HVLP copper foil by the partition configuration of different material conductive roller and the combination of positive and negative pulse current direction control in roughening stage.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil technology, and specifically relates to a method for improving copper plating on the surface of HVLP copper foil. Background Technology

[0002] HVLP (Hyper Very Low Profile) copper foil is an electrolytic copper foil with extremely low surface roughness. Its typical profile value Rz is usually controlled below 2.0 μm, and can even reach 1.0 μm or lower. Compared with conventional electrolytic copper foil, HVLP copper foil has a lower surface tooth structure, thus exhibiting lower conductor loss and skin effect attenuation in high-frequency signal transmission. It is widely used in high-frequency, high-reliability printed circuit board (PCB) fields such as 5G communication, radar, and high-speed digital circuits.

[0003] However, the low profile of HVLP copper foil also presents significant processing and manufacturing challenges. During production, the smooth surface of HVLP copper foil makes it prone to localized plating defects and current concentrations, leading to uneven grain sizes in the plating layer.

[0004] In the surface roughening process, the conductive roller, as a key component for cathode current conduction, directly affects the uniformity of current distribution and the initial nucleation behavior of the copper foil surface. Commonly used conductive roller materials in production include stainless steel rollers, silver-plated copper rollers, and Hastelloy rollers, but each material has certain limitations in practical applications. 1. Stainless steel rollers: low cost but poor conductivity and large fluctuations in contact resistance; 2. Silver-plated rollers: Excellent conductivity, but the surface is prone to oxidation and passivation, requiring periodic activation treatment, and are costly; 3. Hastelloy rollers: good corrosion resistance, but slightly higher contact resistance.

[0005] Meanwhile, traditional roughening processes often employ unidirectional direct current, which can easily lead to localized current concentrations on low-profile surfaces. This results in uneven grain size and increased surface roughness, ultimately undermining the original low-profile advantage of HVLP copper foil. Therefore, how to optimize the material combination of conductive rollers and control the direction of roughening current to achieve a copper plating layer with high bonding strength, high uniformity, and maintained low-profile characteristics, while taking into account the surface characteristics of HVLP copper foil, is a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for improving the copper plating on the surface of HVLP copper foil. This method achieves synergistic optimization of the adhesion, uniformity and low profile characteristics of the HVLP copper foil surface by configuring conductive rollers of different materials in different zones and combining the positive and negative pulse current direction control during the roughening stage.

[0007] This invention provides a method for improving copper plating on the surface of HVLP copper foil, comprising the following steps: The specific process flow of surface treatment in the preparation of electrolytic copper foil is as follows: pickling, first roughening, first curing, second roughening, second curing, blackening, ashing, passivation, silane treatment, and drying; wherein, a silver-plating roller is used in the first roughening, and a Hastelloy roller is used in the second roughening; a pulsed current is used in the second roughening.

[0008] Preferably, the silver plating layer of the silver plating roller has a thickness of 10-15 μm and a silver content of ≥99.9%. The silver plating roller has excellent electrical and thermal conductivity, uniform current distribution, and prevents local overheating; it can produce the highest quality low profile copper foil, prevent defects such as copper plating and color difference from exerting its ultimate conductivity, and can effectively solve the problem of difficult initial nucleation on the surface of HVLP copper foil.

[0009] Preferably, the Hastelloy roller is made of C-276 material, which has a nickel content ≥57%, a molybdenum content 15-17%, a chromium content 14.5-16.5%, an iron content 4.0-7.0%, a tungsten content 3.0-4.5%, and a carbon content ≤0.01%. The Hastelloy roller exhibits well-balanced overall performance, excellent corrosion and wear resistance, long service life, and low maintenance costs.

[0010] Preferably, the first curing and the second curing are performed using Hastelloy rollers.

[0011] Preferably, the pulse current is: 5-10 A / dm in the forward direction. 2 1-5A / dm in reverse 2 The forward and reverse current ratio is 10-20:1. Conventional copper plating uses only a single-direction current, which easily forms local dendrites or nodules on smooth surfaces. By utilizing the reverse current in the pulsed current, the protruding plating layer in the high current density area is preferentially dissolved, achieving a dynamic balance of "deposition-dissolution", actively reducing the surface profile and retaining the HVLP characteristics.

[0012] The present invention has the following beneficial effects: 1. Significantly enhanced anti-peel properties The pre-plating area uses a silver-plating roller to achieve a uniform and ultra-thin initial layer, while the roughening area forms a micro-interlocking structure through reverse pulses. The peel strength can reach more than 0.96 N / mm, meeting the high reliability requirements of high-frequency PCBs.

[0013] 2. Low surface roughness The reverse pulse selectively dissolves the protruding grains, stabilizing the final Rz at around 1.2 μm. This ensures both bonding strength and avoids increased high-frequency losses caused by excessive coarsening.

[0014] 3. Reduced risk of plating solution contamination and equipment corrosion. Hastelloy rollers have strong corrosion resistance and do not release harmful metal ions under reverse pulse conditions, thus reducing the risk of equipment corrosion. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0016] This embodiment provides a method for improving copper plating on the surface of HVLP copper foil, including the following steps: The specific process flow of surface treatment in the preparation of electrolytic copper foil is as follows: pickling, first roughening, first curing, second roughening, second curing, blackening, ashing, passivation, silane treatment, and drying.

[0017] Implementation conditions: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 3000-500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; Additives (PEG: 20ppm, SPS: 10ppm, gelatin: 5ppm); Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+ 15g / L, H2SO4: 110g / L, Additive: Sodium tungstate 10ppm, Temperature: 26℃; Curing: Cu 2+ H₂SO₄: 50 g / L, H₂SO₄: 110 g / L, temperature: 50℃; Blackening: Ni 2+ : 1.0 g / L, K4P2O7: 55 g / L, pH: 10.0, temperature: 40℃, current density: 5 A / dm2; Ashing: Zn 2+ : 1.2 g / L, K4P2O7: 60 g / L, pH: 11.5, temperature: 40℃, current density: 15 A / dm2; Passivation: Cr 2+ 1.0 g / L, pH: 12, temperature: 30℃, current density: 8 A / dm2; Silane coupling agent: aminosilane, addition amount: 1%.

[0018] Drying: After drying under the above conditions, the copper foil is finally obtained by winding.

[0019] Example 1 Conductive roller configuration: Current parameter settings: Copper foil test results: Surface non-contact Rz: 1.18 μm; Peel strength: 1.13 kgf / cm; Defect rate: No missing plating, no copper plating, defect rate 1%.

[0020] Comparative Example 1 Conductive roller configuration: Current parameter settings: Copper foil test results: Surface non-contact Rz: 1.58 μm; Peel strength: 0.76 kgf / cm; Defect rate: Scattered unplated areas, scattered small copper platings (size 5-35um), defect rate 15%.

[0021] Comparative Example 2 Conductive roller configuration: Current parameter settings: Copper foil test results: Surface non-contact Rz: 1.13 μm; Peel strength: 0.96 kgf / cm; Defect rate: No missing plating, no copper plating, defect rate 4%.

[0022] Comparative Example 3 Conductive roller configuration: Current parameter settings: Copper foil test results: Surface non-contact Rz: 0.98 μm; Peel strength: 1.03 kgf / cm; Defect rate: No missing plating, no copper plating, defect rate 2%.

[0023] Comparative Example 4 Conductive roller configuration: Current parameter settings: Copper foil test results: Surface non-contact Rz: 1.20 μm; Peel strength: 0.90 kgf / cm; Defect rate: No obvious plating defects or copper plating defects, defect rate 7%.

[0024] As can be seen from Examples 1, 1 Comparative Example, and 2, under the same conditions, the silver-plated roller has the best effect on improving the copper plating effect on the HVLP surface, followed by the Hastelloy roller, and the stainless steel roller has the worst effect. Examples 1 and 3 further confirm that using silver-plated rollers does not necessarily have the best effect on improving the copper plating effect on the HVLP surface.

[0025] In comparison with Example 1 and Comparative Example 4, in the same combination of conductive roller configurations, pulsed current can reduce the surface profile and retain HVLP characteristics compared to DC current.

Claims

1. A method for improving copper plating on the surface of HVLP copper foil, characterized in that, Includes the following steps: The specific process flow of surface treatment in the preparation of electrolytic copper foil is as follows: pickling, first roughening, first curing, second roughening, second curing, blackening, ashing, passivation, silane treatment, and drying; wherein, a silver-plating roller is used in the first roughening, and a Hastelloy roller is used in the second roughening; a pulsed current is used in the second roughening.

2. The method according to claim 1, characterized in that, The silver plating layer of the silver plating roller has a thickness of 10-15 μm and a silver content of ≥99.9%.

3. The method according to claim 1, characterized in that, The Hastelloy roller is made of C-276 material, which has a nickel content ≥57%, a molybdenum content 15-17%, a chromium content 14.5-16.5%, an iron content 4.0-7.0%, a tungsten content 3.0-4.5%, and a carbon content ≤0.01%.

4. The method according to claim 1, characterized in that, The first and second curing processes were performed using Hastelloy rollers.

5. The method according to claim 1, characterized in that, The pulse current is specifically: 5-10 A / dm in the forward direction. 2 1-5A / dm in reverse 2 The forward and reverse time ratio is 10-20:1.

Images