Method for improving heat resistance of reverse copper foil

Abstract

The present application relates to a kind of methods for improving the heat resistance of reverse copper foil, comprising: blackening process, ashing process, passivation process in the preparation process of reverse copper foil are carried out under acidic conditions;Wherein, blackening process is carried out in the electroplating solution A containing nickel ion, hypophosphorous acid ion, boric acid electroplating nickel;Ashing process is carried out in the electroplating solution B containing zinc ion, boric acid electroplating zinc;Passivation process is carried out in the electroplating solution C containing chromium ion, hypophosphorous acid ion, boric acid electroplating chromium.The present application is obtained under the combination of acidic blackening process, acidic ashing process, acidic passivation process, and the reverse electrolytic copper foil can meet the requirements of stripping strength and can meet the heat stability (small heat attenuation), solve the problem that conventional reverse electrolytic copper foil cannot meet the requirements of stripping strength while having good heat stability.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil technology, and specifically relates to a method for improving the heat resistance of reverse copper foil. Background Technology

[0002] Printed circuit boards (PCBs) are crucial components in the electronics industry, often referred to as the "mother of electronic products." PCBs rely on copper foil traces to transmit current and signals. These copper foil traces, as one of the main raw materials for PCB and CCL (copper clad laminate) production, are often referred to as neural networks. With the application and rapid development of 5G, electric vehicles, and AI computing power, the demand for high-multilayer and high-frequency / high-speed PCBs is growing rapidly. High-frequency and high-speed applications require specific electrolytic copper foil, and reverse-phase copper foil is primarily used in the production of high-frequency / high-speed boards.

[0003] High-frequency and high-speed PCBs have high requirements for heat resistance and electrical loss in PCB manufacturing processes and end-customer applications. Currently, the electrolytic copper foil used in these high-end products is basically monopolized. Most domestic conventional reverse electrolytic copper foils cannot meet the peel strength requirements while also having good heat resistance. After long-term use, the peel strength usually decreases significantly and the heat resistance is poor, making it impossible to meet the requirements of downstream processes and products. Summary of the Invention

[0004] This invention provides a method for improving the heat resistance of reverse copper foil. The technical problem to be solved is that the peel resistance of reverse copper foil decreases significantly after repeated pressing, and it is impossible to have good heat resistance stability while meeting the peel strength requirements.

[0005] This invention provides a method for improving the heat resistance of inverted copper foil, comprising: The blackening, ashing, and passivation processes in the preparation of reverse copper foil are all carried out under acidic conditions. Specifically, the blackening process involves electroplating nickel in electroplating solution A, which contains nickel ions, hypophosphite ions, and boric acid; the ashing process involves electroplating zinc in electroplating solution B, which contains zinc ions and boric acid; and the passivation process involves electroplating chromium in electroplating solution C, which contains chromium ions, hypophosphite ions, and boric acid.

[0006] Preferably, the composition of the electroplating solution A is: Ni 2+ 20~30 g / L, PO2 3- :5~10 g / L, H3BO3: 30~40 g / L, pH: 3~4.

[0007] Preferably, the nickel plating temperature is 20~25℃ and the current density is 5~10A / dm². 2 .

[0008] Preferably, the electroplating solution B has the following composition: Zn 2+ : 4~10 g / L, H3BO3: 30~40 g / L, pH: 4~5.

[0009] Preferably, the electroplating zinc temperature is 25~30℃ and the current density is 5~10A / dm³. 2 .

[0010] Preferably, the electroplating solution C has the following composition: Cr 2+ 1~2 g / L, PO2 3- :5~10 g / L, H3BO3: 30~40 g / L, pH: 3~4.

[0011] Preferably, the electroplating temperature for chromium is 35~40℃, and the current density is 10~15A / dm³. 2 .

[0012] The key point of this invention is: Acidic electroplating of nickel / zinc / chromium essentially involves applying a direct current to induce a reduction reaction of nickel / zinc / chromium ions on the cathode (workpiece), thereby depositing a metal layer. Acidic electroplating is more stable than alkaline electroplating, and the reaction principle is as follows: Main reaction: Ni / Zn² + / Cr 3+ + 2e - → Ni / Zn / Cr; Side reaction: 2H + + 2e - → H2↑.

[0013] In alkaline processes, the pH at the cathode rises as side reactions occur, leading to significant fluctuations in electroplating efficiency. In contrast, acidic processes, due to different plating solution formulations and higher resistivity, exhibit more stable pH throughout the plating process, resulting in consistent electroplating efficiency.

[0014] Beneficial effects The present invention, through a combination of acid blackening, acid ashing, and acid passivation processes, produces a reverse electrolytic copper foil that meets both peel strength and heat resistance (low thermal decay) requirements, thus solving the problem that conventional reverse electrolytic copper foil cannot achieve both peel strength and good heat resistance. 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] The following examples and comparative examples all use 35μm reverse copper foil as an example.

[0017] Example 1 Preparation methods include: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 4900-5700 A / m 2 Electrolyte flow rate: 45m³ 3 / h; The molecular weight of collagen is 2000 Daltons, and the collagen concentration in the electrolyte is 10ppm; Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+ 15 g / L, H2SO4: 110 g / L, temperature: 26℃, current density: 70 A / dm³ 2 ; Curing: Cu 2+ 50 g / L, H2SO4: 110 g / L, temperature: 50℃, current density: 100 A / dm³ 2 ; Blackening: Ni 2+ 22g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.4, temperature: 20℃, current density: 5 A / dm³ 2 ; Ashing: Zn 2+ 4.5 g / L, H3BO3: 32 g / L, pH: 4.5, temperature: 26℃, current density: 7 A / dm³ 2 ; Passivation: Cr 2+ 1.0 g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.8, temperature: 38℃, current density: 11 A / dm³ 2 ; Silane coupling agent: aminosilane, ratio: 10%.

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

[0019] Example 2 Preparation methods include: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 4900-5700 A / m 2 Electrolyte flow rate: 45m³ 3 / h; The molecular weight of collagen is 2000 Daltons, and the collagen concentration in the electrolyte is 10ppm; Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+ 15 g / L, H2SO4: 110 g / L, temperature: 26℃, current density: 70 A / dm³ 2 ; Curing: Cu 2+ 50 g / L, H2SO4: 110 g / L, temperature: 50℃, current density: 100 A / dm³ 2 ; Blackening: Ni 2+ 22g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.4, temperature: 20℃, current density: 5 A / dm³ 2 ; Ashing: Zn 2+ 4.5 g / L, H3BO3: 32 g / L, pH: 5.0, temperature: 26℃, current density: 7 A / dm³ 2 ; Passivation: Cr 2+ 1.0 g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.8, temperature: 38℃, current density: 11 A / dm³ 2 ; Silane coupling agent: aminosilane, ratio: 10%.

[0020] Drying: After drying under the above conditions, the copper foil is finally obtained by winding.

[0021] Example 3 Preparation methods include: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 4900-5700 A / m2 Electrolyte flow rate: 45m³ 3 / h; The molecular weight of collagen is 2000 Daltons, and the collagen concentration in the electrolyte is 10ppm; Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+ 15 g / L, H2SO4: 110 g / L, temperature: 26℃, current density: 70 A / dm³ 2 ; Curing: Cu 2+ 50 g / L, H2SO4: 110 g / L, temperature: 50℃, current density: 100 A / dm³ 2 ; Blackening: NI 2+ 22g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.0, temperature: 20℃, current density: 5 A / dm³ 2 ; Ashing: Zn 2+ 4.5 g / L, H3BO3: 32 g / L, pH: 4.0, temperature: 26℃, current density: 7 A / dm³ 2 ; Passivation: Cr 2+ 1.0 g / L, PO2 3- 5.5 g / L, H3BO3: 35 g / L, pH: 3.8, temperature: 38℃, current density: 11 A / dm³ 2 ; Silane coupling agent: aminosilane, ratio: 10%.

[0022] Drying: After drying under the above conditions, the copper foil is finally obtained by winding.

[0023] Comparative Example 1 Preparation methods include: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 4900-5700 A / m 2 Electrolyte flow rate: 45m³ 3 / h; The molecular weight of collagen is 2000 Daltons, and the collagen concentration in the electrolyte is 10ppm; Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+15 g / L, H2SO4: 110 g / L, temperature: 26℃, current density: 70 A / dm³ 2 ; Curing: Cu 2+ 50 g / L, H2SO4: 110 g / L, temperature: 50℃, current density: 100 A / dm³ 2 ; Blackening: Ni 2+ 22 g / L, K₄P₂O₇: 55 g / L, pH: 10.0, temperature: 40℃, current density: 5 A / dm³ 2 ; Ashing: Zn 2+ 4.5 g / L, K₄P₂O₇: 60 g / L, pH: 11.5, temperature: 40℃, current density: 7 A / dm³ 2 ; Passivation: Cr 2+ 1.0 g / L, pH: 12, temperature: 30℃, current density: 11 A / dm³ 2 ; Silane coupling agent: aminosilane, ratio: 10%; Drying: After drying under the above conditions, the copper foil is finally obtained by winding.

[0024] Comparative Example 2 Preparation methods include: Electrolysis: Cu 2+ 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57℃, current density: 4900-5700 A / m 2 Electrolyte flow rate: 45m³ 3 / h; The molecular weight of collagen is 2000 Daltons, and the collagen concentration in the electrolyte is 10ppm; Pickling: Cu 2+ ≤1.5g / L, H2SO4: 110g / L, temperature: 26℃; Coarsening: Cu 2+ 15 g / L, H2SO4: 110 g / L, temperature: 26℃, current density: 70 A / dm³ 2 ; Curing: Cu 2+ 50 g / L, H2SO4: 110 g / L, temperature: 50℃, current density: 100 A / dm³ 2 ; Blackening: Ni 2+ 22 g / L, K₄P₂O₇: 55 g / L, pH: 10.0, temperature: 40℃, current density: 5 A / dm³ 2 ; Ashing: Zn 2+ 4.5 g / L, K₄P₂O₇: 55 g / L, pH: 11, Temperature: 40℃, Current density: 7 A / dm³ 2 ; Passivation: Cr 2+ 1.0 g / L, pH: 12, temperature: 30℃, current density: 11 A / dm³ 2 ; Silane coupling agent: aminosilane, ratio: 10%; Drying: After drying under the above conditions, the copper foil is finally obtained by winding.

[0025] Table 1. Relationship between different pulse waveforms and surface weight gain and peel resistance Comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2, it can be seen that the combination of acidic blackening, acidic ashing, and acidic passivation processes exhibits lower peel resistance attenuation and better thermal stability than the combination of alkaline blackening, alkaline ashing, and alkaline passivation processes after immersion in tin at 288°C for 20 minutes.

[0026] Comparing Examples 1, 2, and 3, Example 1 exhibited the best conditions under the same acidic process combination. Under tin immersion conditions of 288°C for 20 minutes, the peel resistance degradation was minimal, almost negligible, and effectively met the thermal stability requirements.

Claims

1. A method for improving the heat resistance of reverse copper foil, characterized in that, include: The blackening, ashing, and passivation processes in the preparation of reverse copper foil are all carried out under acidic conditions; among them, the blackening process is carried out by electroplating nickel in electroplating solution A containing nickel ions, hypophosphite ions, and boric acid. The ashing process involves electroplating zinc in electroplating solution B, which contains zinc ions and boric acid; the passivation process involves electroplating chromium in electroplating solution C, which contains chromium ions, hypophosphite ions, and boric acid.

2. The method according to claim 1, characterized in that, The composition of the electroplating solution A is: Ni 2+ 20~30 g / L, PO2 3- :5~10 g / L, H3BO3: 30~40 g / L, pH: 3~4.

3. The method according to claim 1, characterized in that, The nickel plating temperature is 20~25℃, and the current density is 5~10A / dm². 2 .

4. The method according to claim 1, characterized in that, The composition of the electroplating solution B is: Zn 2+ : 4~10 g / L, H3BO3: 30~40 g / L, pH: 4~5.

5. The method according to claim 1, characterized in that, The electroplating zinc temperature is 25~30℃, and the current density is 5~10A / dm². 2 .

6. The method according to claim 1, characterized in that, The composition of the electroplating solution C is: Cr 2+ 1~2 g / L, PO2 3- :5~10 g / L, H3BO3: 30~40 g / L, pH: 3~4.

7. The method according to claim 1, characterized in that, The electroplating temperature for chromium is 35~40℃, and the current density is 10~15A / dm². 2 .

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