High-strength VLP copper foil for ultra-high-precision PCB and preparation method of high-strength VLP copper foil

Abstract

The invention belongs to the technical field of electrolytic copper foil production, and particularly relates to a high-strength VLP copper foil for an ultra-high refined PCB and a preparation method of the high-strength VLP copper foil. The method comprises the following preparation steps that an additive is added into a copper sulfate electrolyte, the additive comprises stannous mono-sulphate, trisodium citrate and phytic acid, and an electrodeposition electrolyte is obtained; carrying out electro-deposition on the obtained electrolyte on the surface of a cathode roller to obtain a raw foil with a tuberization effect, wherein the rough surface roughness Rz of the raw foil is 1.5-2.5 microns; and sequentially carrying out anti-oxidation treatment and coupling agent treatment on the obtained crude foil to obtain the high-strength VLP copper foil. The special additives are added into the electrolyte, so that the prepared raw foil has a nodulation effect, and the nodulation treatment procedures such as coarsening and curing in the surface treatment process are not needed; the VLP copper foil of which the roughness, the tensile strength and the peel strength all meet the requirements for ultra-high refinement PCB manufacturing can be obtained through one-step electro-deposition.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foil production, and in particular relates to a high-strength VLP copper foil for ultra-high-precision PCBs and a preparation method thereof. Background Art

[0002] With the development of the electronics industry, PCBs are increasingly moving towards high-density, fine-line circuits. PCB line widths and spacings have been reduced from hundreds of microns to the current mainstream tens of microns. Ultra-high-definition PCBs require line widths and spacings below 40μm. If traditional STD and HTE copper foils are used for ultra-high-definition PCB manufacturing, the uneven microscopic surface and high roughness of STD and HTE copper foils will cause some etching liquid to penetrate into the copper foil during the circuit manufacturing process (etching process), resulting in wider circuit erosion and narrowing of the actual circuit, which cannot meet the requirements of ultra-high-definition PCB production. If HVLP copper foil (very low peak copper foil) is used for ultra-high-definition PCB manufacturing, the low roughness of HVLP copper foil will result in relatively low peel strength after bonding with the substrate, making the finished PCB prone to problems such as board explosion or circuit detachment. Therefore, it is necessary to develop a copper foil with ultra-low peak value (VLP copper foil) for ultra-high-definition PCB manufacturing. In addition, since ultra-high-precision PCBs require stable, ultra-fine line width and spacing (line width and spacing <30μm), if conventional thickness copper foil (≥12μ) is used, burrs (insufficient etching) or side etching (excessive etching) are likely to occur during the circuit making process (etching process), which cannot meet the requirements of ultra-high-precision PCB production; if ordinary low-tensile strength thin-gauge copper foil (<12μ) or double-sided light lithium battery copper foil is used, because it does not have a nodular effect, if it is only treated with anti-oxidation and coupling agents and then used directly for pressing, the peeling strength is low, and the PCB made is prone to line breakage and explosion. Therefore, it must undergo nodular treatment processes such as roughening and curing during the surface treatment process. However, because the copper foil is too thin, it is easy to be folded, torn, and broken after multiple surface treatments and the driving of rollers, which cannot meet production requirements. Therefore, it is necessary to develop a high-tensile strength VLP copper foil with a self-nodulating effect, ultra-low roughness, and no need for roughening or curing. It only needs to be treated with anti-oxidation and coupling agents to meet the requirements of high-strength VLP copper foil for ultra-high-precision PCB manufacturing. Summary of the Invention

[0003] In view of the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing high-strength VLP copper foil for ultra-high-precision PCBs.

[0004] Another object of the present invention is to provide a high-strength VLP copper foil for ultra-high-precision PCB prepared by the above method.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing high-strength VLP copper foil for ultra-high-precision PCBs comprises the following steps:

[0007] (1) adding an additive to a copper sulfate electrolyte, wherein the additive comprises stannous sulfate, trisodium citrate and phytic acid to obtain an electrodeposition electrolyte;

[0008] (2) using the electrolyte of step (1) to carry out electrodeposition on the surface of the cathode roller to obtain a raw foil with a self-nodular effect and a matte surface roughness Rz of 1.5 to 2.5 μm;

[0009] (3) The raw foil of step (2) is subjected to anti-oxidation treatment and coupling agent treatment in sequence to obtain high-strength VLP copper foil.

[0010] Furthermore, the copper content in the copper sulfate electrolyte in step (1) is 50-100 g / L, and the sulfuric acid content is 100-180 g / L.

[0011] Furthermore, the additives added in step (1) are added at concentrations of 1-10 g / L of stannous sulfate, 1-10 g / L of trisodium citrate, and 0.5-5 g / L of phytic acid.

[0012] More preferably, the concentration ratio of stannous sulfate, trisodium citrate and phytic acid is 1:(0.6-1.5):(0.4-1).

[0013] Furthermore, the temperature of the electrodeposition in step (2) is 30-70°C, and the flow rate of the electrolyte is 40-90m 3 / h, current density is 2000~5000A / m 2 .

[0014] Furthermore, the anti-oxidation treatment in step (3) is performed by electroplating using a ZnCr anti-oxidation plating solution.

[0015] Preferably, the zinc content in the ZnCr anti-oxidation plating solution is 5-10 g / L, the chromium content is 1-3 g / L, and the pH value is 11-14; the current density of the electroplating treatment is 0.5-2 A / dm 2 .

[0016] Furthermore, the coupling agent treatment in step (3) is carried out by uniformly spraying a 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution; the mass concentration of the 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution is 0.5% to 1%, and the pH value is 4 to 7.

[0017] Furthermore, the high-strength VLP copper foil in step (3) has a thickness of 10 to 20 μm, a room temperature tensile strength of ≥450 MPa, a high temperature (180° C.) tensile strength of ≥200 MPa, and a peel strength of ≥1.2 N / mm (GB / T 5230-2020).

[0018] A high-strength VLP copper foil for ultra-high-precision PCB is prepared by the above method.

[0019] The high-strength VLP copper foil obtained by the present invention is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30 μm).

[0020] The principle of the present invention is as follows: by adding special additives to the electrolyte, among which stannous sulfate is mainly used to promote the growth of copper nodules. However, unlike the conventional roughening process which is only carried out on the surface of the raw foil, the present invention directly obtains the raw foil with a nodular effect through one-step electroplating. If the copper nodules are too loose or dispersed, the strength of the copper foil will be seriously affected. In order to overcome this problem, the present invention first adds trisodium citrate and utilizes its interface regulation effect to improve the interlayer bonding of the deposited copper. On the other hand, a certain amount of phytic acid is added and its complexation with copper ions is utilized to refine the grain size of the deposited copper, improve uniformity, reduce defects, and improve the internal bonding of the deposited copper. Through the combined action of the above-mentioned additives, VLP copper foil with roughness, tensile strength and peel strength that meet the requirements for ultra-high precision PCB manufacturing can be obtained by one-step electroplating. There is no need to use prefabricated raw foil and then carry out roughening and curing treatment separately, thereby significantly simplifying the production process of VLP copper foil, improving production efficiency and reducing production costs.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention adds a special additive to the electrolyte so that the raw foil obtained has a self-nodular effect. It does not need to undergo the nodular treatment steps such as roughening and curing in the surface treatment process. The raw foil only needs to be subjected to anti-oxidation and coupling agent surface treatment. This implementation process can be completed in a "raw foil-surface treatment machine" at one time, avoiding the risks of folding, edge tearing, and foil breakage in the complex nodular surface treatment process of thin-gauge copper foil through roughening and curing, thereby obtaining a high-strength VLP copper foil suitable for ultra-high-precision PCBs.

[0023] (2) The high-strength VLP copper foil suitable for ultra-high-precision PCBs produced by the present invention has a moderate roughness of the matte surface (Rz1.5-2.5μm), which ensures the peeling strength of the PCB board and avoids the side corrosion and burrs. The room temperature tensile strength is ≥450MPa and the high temperature tensile strength is ≥200MPa, which reduces the board cracking phenomenon in the PCB manufacturing process. It is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30μm). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the production process of the VLP copper foil in Example 1.

[0025] Figure 2 This is the SEM image of the VLP copper foil obtained in Example 1.

[0026] Figure 3 This is the SEM image of the VLP copper foil obtained in Example 2.

[0027] Figure 4 This is the SEM image of the VLP copper foil obtained in Comparative Example 1. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] Example 1

[0030] Step 1: Preparation of electrolyte: Add copper material to a solution containing sulfuric acid and heat and dissolve it to obtain a copper sulfate electrolyte. The copper sulfate electrolyte has a copper content of 75 g / L, a sulfuric acid content of 120 g / L, and a temperature of 52°C.

[0031] Step 2: Adding additives: adding special additives to the copper sulfate electrolyte obtained in step 1, wherein the special additives are stannous sulfate, trisodium citrate and phytic acid, wherein the concentration of stannous sulfate is 5 g / L, the concentration of trisodium citrate is 5 g / L, and the concentration of phytic acid is 2.5 g / L.

[0032] Step 3: Raw foil production: Electrodeposit the electrolyte obtained in step 2 on the surface of the cathode roller in the "raw foil-surface treatment integrated machine". The flow rate of the electrodeposition electrolyte is 60m 3 / h, current density is 3000A / m 2 After electrodeposition, an 18μm VLP raw foil with a matte surface roughness of Rz1.8μm and a built-in tumor effect was obtained.

[0033] Step 4: Anti-oxidation treatment: The raw foil obtained in step 3 is subjected to anti-oxidation treatment in the "raw foil-surface treatment integrated machine". The anti-oxidation treatment is performed by electroplating with a ZnCr anti-oxidation plating solution. During the anti-oxidation treatment, the zinc content is 8g / L, the chromium content is 2g / L, the pH value is 12, and the current density is 1A / dm 2 , the raw foil is given an anti-oxidation layer by electroplating.

[0034] Step 5: Coupling agent treatment: The VLP copper foil coated with the anti-oxidation layer in step 4 is further treated with a coupling agent. The coupling agent treatment is to evenly spray a 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution (concentration of 0.5wt%, pH value of 6) on the 18μ VLP copper foil coated with the anti-oxidation layer in step 4 to obtain a coupling agent treatment layer on the copper foil.

[0035] The production process flow chart of VLP copper foil in this embodiment is as follows: Figure 1 The SEM image of the obtained VLP copper foil is shown as Figure 2 shown.

[0036] The high-strength, thin-gauge 18μm VLP copper foil suitable for ultra-high-precision PCBs prepared through steps 1 to 5 above has a performance test according to GB / T 5230-2020 standard, with a matte roughness Rz of 1.8μm, a peel strength of 1.28N / mm, a room temperature tensile strength of 500MPa, and a high-temperature tensile strength of 240MPa. It is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30μm).

[0037] Example 2

[0038] Step 1: Preparation of electrolyte: Add copper material to a solution containing sulfuric acid and heat and dissolve it to obtain a copper sulfate electrolyte. The copper sulfate electrolyte has a copper content of 70 g / L, a sulfuric acid content of 110 g / L, and a temperature of 50°C.

[0039] Step 2: Adding additives: adding special additives to the copper sulfate electrolyte obtained in step 1, wherein the special additives are stannous sulfate, trisodium citrate and phytic acid, wherein the concentration of stannous sulfate is 3 g / L, the concentration of trisodium citrate is 4 g / L, and the concentration of phytic acid is 2 g / L.

[0040] Step 3: Raw foil production: Electrodeposit the electrolyte obtained in step 2 on the surface of the cathode roller in the "raw foil-surface treatment integrated machine". The flow rate of the electrodeposition electrolyte is 48m 3 / h, current density is 4000A / m 2 After electrodeposition, a 12μm VLP raw foil with a matte surface roughness of Rz1.7μm and a built-in tumor effect was obtained.

[0041] Step 4: Anti-oxidation treatment: The raw foil obtained in step 3 is subjected to anti-oxidation treatment in the "raw foil-surface treatment integrated machine". The anti-oxidation treatment is performed by electroplating with a ZnCr anti-oxidation plating solution. During the anti-oxidation treatment, the zinc content is 8g / L, the chromium content is 2.5g / L, the pH value is 13, and the current density is 1.5A / dm 2 , the raw foil is given an anti-oxidation layer by electroplating.

[0042] Step 5: Coupling agent treatment: The VLP copper foil coated with the anti-oxidation layer in step 4 is further treated with a coupling agent. The coupling agent treatment is to evenly spray an aqueous solution of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (concentration of 0.6wt%, pH value of 5.5) on the VLP copper foil coated with the anti-oxidation layer in step 4 to obtain a coupling agent treatment layer on the copper foil.

[0043] The SEM image of the VLP copper foil obtained in this embodiment is as follows: Figure 3 shown.

[0044] The high-strength, thin-gauge 12μm VLP copper foil suitable for ultra-high-precision PCBs prepared through steps 1 to 5 above has a performance test according to GB / T 5230-2020 standard, with a matte roughness Rz of 1.7μm, a peel strength of 1.25N / mm, a room temperature tensile strength of 550MPa, and a high-temperature tensile strength of 250MPa. It is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30μm).

[0045] Example 3

[0046] Step 1: Preparation of electrolyte: Add copper material to a solution containing sulfuric acid and heat and dissolve it to obtain a copper sulfate electrolyte. The copper sulfate electrolyte has a copper content of 68 g / L, a sulfuric acid content of 125 g / L, and a temperature of 48°C.

[0047] Step 2: Adding additives: adding special additives to the copper sulfate electrolyte obtained in step 1, wherein the special additives are stannous sulfate, trisodium citrate and phytic acid, wherein the concentration of stannous sulfate is 8 g / L, the concentration of trisodium citrate is 5 g / L, and the concentration of phytic acid is 3.2 g / L.

[0048] Step 3: Raw foil production: Electrodeposit the electrolyte obtained in step 2 on the surface of the cathode roller in the "raw foil-surface treatment integrated machine". The flow rate of the electrodeposition electrolyte is 55m 3 / h, current density is 2000A / m 2 After electrodeposition, a 10μm VLP raw foil with a matte surface roughness of Rz1.6μm and a tumor-like effect was obtained.

[0049] Step 4: Anti-oxidation treatment: The raw foil obtained in step 3 is subjected to anti-oxidation treatment in the "raw foil-surface treatment integrated machine". The anti-oxidation treatment is performed by electroplating with a ZnCr anti-oxidation plating solution. During the anti-oxidation treatment, the zinc content is 7g / L, the chromium content is 1.8g / L, the pH value is 13, and the current density is 1.5A / dm 2 , the raw foil is given an anti-oxidation layer by electroplating.

[0050] Step 5: Coupling agent treatment: The VLP copper foil coated with the anti-oxidation layer in step 4 is further treated with a coupling agent. The coupling agent treatment is to evenly spray a 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution (concentration of 0.8wt%, pH value of 5) on the VLP copper foil coated with the anti-oxidation layer in step 4 to obtain a coupling agent treatment layer on the copper foil.

[0051] The high-strength, thin-gauge 10μm VLP copper foil suitable for ultra-high-precision PCBs prepared through steps 1 to 5 above is tested for performance according to the GB / T 5230-2020 standard, with a matte roughness Rz of 1.6μm, a peel strength of 1.21N / mm, a room temperature tensile strength of 580MPa, and a high-temperature tensile strength of 260MPa. It is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30μm).

[0052] Example 4

[0053] Step 1: Preparation of electrolyte: Add copper material to a solution containing sulfuric acid and heat and dissolve it to obtain a copper sulfate electrolyte. The copper sulfate electrolyte has a copper content of 50 g / L, a sulfuric acid content of 100 g / L, and a temperature of 45°C.

[0054] Step 2: Adding additives: adding special additives to the copper sulfate electrolyte obtained in step 1, wherein the special additives are stannous sulfate, trisodium citrate and phytic acid, wherein the concentration of stannous sulfate is 1 g / L, the concentration of trisodium citrate is 1.5 g / L, and the concentration of phytic acid is 1 g / L.

[0055] Step 3: Raw foil production: Electrodeposit the electrolyte obtained in step 2 on the surface of the cathode roller in the "raw foil-surface treatment integrated machine". The flow rate of the electrodeposition electrolyte is 70m 3 / h, current density is 5000A / m 2 After electrodeposition, a 15μm VLP raw foil with a matte surface roughness of Rz2.3μm and a built-in tumor effect was obtained.

[0056] Step 4: Anti-oxidation treatment: The raw foil obtained in step 3 is subjected to anti-oxidation treatment in the "raw foil-surface treatment integrated machine". The anti-oxidation treatment is performed by electroplating with a ZnCr anti-oxidation plating solution. During the anti-oxidation treatment, the zinc content is 6g / L, the chromium content is 1.5g / L, the pH value is 12, and the current density is 2A / dm 2 , the raw foil is given an anti-oxidation layer by electroplating.

[0057] Step 5: Coupling agent treatment: The VLP copper foil coated with the anti-oxidation layer in step 4 is further treated with a coupling agent. The coupling agent treatment is to evenly spray a 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution (with a concentration of 1 wt % and a pH value of 5) on the VLP copper foil coated with the anti-oxidation layer in step 4 to obtain a coupling agent treatment layer on the copper foil.

[0058] The high-strength, thin-gauge 15μm VLP copper foil suitable for ultra-high-precision PCBs prepared through steps 1 to 5 above has a performance test according to GB / T 5230-2020 standard, with a matte roughness Rz of 1.5μm, a peel strength of 1.20N / mm, a room temperature tensile strength of 530MPa, and a high-temperature tensile strength of 250MPa. It is suitable for the manufacture of ultra-high-precision PCBs with high density and fine circuits (line width and line spacing <30μm).

[0059] Comparative Example 1

[0060] Compared with Example 1, this comparative example does not contain trisodium citrate and phytic acid as additives, and the rest are the same.

[0061] The SEM image of the VLP copper foil obtained in this comparative example is as follows: Figure 4 shown.

[0062] The 18μm copper foil obtained in this comparative example, tested according to GB / T 5230-2020, has a matte surface roughness Rz of 4.5μm, a peel strength of 1.15N / mm, a room temperature tensile strength of 330MPa, and a high-temperature tensile strength of 180MPa. This makes it suitable for the manufacture of PCBs with wider circuits (line width and line spacing ≥ 50μm).

[0063] The results of this comparative example show that the addition of only stannous sulfate as a roughening agent during the electrolytic green foil manufacturing process significantly increases the matte surface roughness, making it unable to meet the requirements of ultra-high-precision PCB production with line widths and spacings less than 30μm. Furthermore, despite the increased roughness, the peel strength actually decreases, indicating that the copper nodules are too loose and of poor quality. Furthermore, the tensile strength decreases significantly, indicating that the addition of a roughening agent during the green foil manufacturing process significantly reduces the strength of the copper foil.

[0064] Comparative Example 2

[0065] Compared with Example 1, this comparative example did not add trisodium citrate to the additive, increased the phytic acid concentration to 7.5 g / L, and remained the same.

[0066] The 18μm copper foil obtained in this comparative example was tested for performance according to GB / T 5230-2020 standard, with a matte roughness Rz of 1.1μm, a peel strength of 0.74N / mm, a room temperature tensile strength of 440MPa, and a high temperature tensile strength of 220MPa.

[0067] The results of this comparative example show that replacing trisodium citrate with phytic acid significantly reduces the roughness and peel strength of the resulting copper foil, indicating that excessively high concentrations of phytic acid inhibit the growth of copper nodules, leading to a significant reduction in the roughness and peel strength of the copper foil. Simultaneously, the tensile strength of the copper foil also showed a significant decrease, indicating that the addition of trisodium citrate and phytic acid has a significant synergistic effect in improving the tensile strength of the copper foil.

[0068] Comparative Example 3

[0069] Compared with Example 1, this comparative example did not add phytic acid to the additive, increased the concentration of trisodium citrate to 7.5 g / L, and remained the same.

[0070] The 18μm copper foil obtained in this comparative example was tested for performance according to GB / T 5230-2020 standard, with a matte roughness Rz of 2.5μm, a peel strength of 1.12N / mm, a room temperature tensile strength of 430MPa, and a high temperature tensile strength of 210MPa.

[0071] The results of this comparative example show that replacing phytic acid with trisodium citrate significantly increases the roughness of the resulting copper foil, but reduces its peel strength. This indicates that phytic acid inhibits excessive roughness increases and improves the quality and strength of the copper nodules. At the same time, the tensile strength of the copper foil also decreases significantly, further demonstrating that the addition of trisodium citrate and phytic acid has a significant synergistic effect in improving the tensile strength of the copper foil.

[0072] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing high-strength VLP copper foil for ultra-high-precision PCB, characterized in that: The method comprises the following preparation steps: (1) adding an additive to a copper sulfate electrolyte, wherein the additive comprises stannous sulfate, trisodium citrate and phytic acid to obtain an electrodeposition electrolyte; (2) using the electrolyte of step (1) to carry out electrodeposition on the surface of the cathode roller to obtain a raw foil with a self-nodular effect and a matte surface roughness Rz of 1.5 to 2.5 μm; (3) The raw foil of step (2) is subjected to anti-oxidation treatment and coupling agent treatment in sequence to obtain high-strength VLP copper foil.

2. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The copper content in the copper sulfate electrolyte described in step (1) is 50-100 g / L, and the sulfuric acid content is 100-180 g / L.

3. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The additives added in step (1) are added at concentrations of 1-10 g / L of stannous sulfate, 1-10 g / L of trisodium citrate, and 0.5-5 g / L of phytic acid.

4. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 3, characterized in that: The concentration ratio of stannous sulfate, trisodium citrate and phytic acid is 1:(0.6-1.5):(0.4-1).

5. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The temperature of the electrodeposition in step (2) is 30-70°C, and the flow rate of the electrolyte is 40-90m 3 / h, current density is 2000~5000A / m 2 .

6. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The anti-oxidation treatment in step (3) is performed by electroplating using a ZnCr anti-oxidation plating solution.

7. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 6, characterized in that: The ZnCr anti-oxidation plating solution contains 5-10 g / L zinc, 1-3 g / L chromium, and a pH value of 11-14. The current density of the electroplating process is 0.5-2 A / dm 2 .

8. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The coupling agent treatment in step (3) is carried out by uniformly spraying a 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution; the mass concentration of the 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane aqueous solution is 0.5% to 1%, and the pH value is 4 to 7.

9. The method for preparing a high-strength VLP copper foil for ultra-high-precision PCB according to claim 1, characterized in that: The high-strength VLP copper foil in step (3) has a thickness of 10 to 20 μm, a room temperature tensile strength of ≥450 MPa, a high temperature tensile strength of ≥200 MPa, and a peel strength of ≥1.2 N / mm.

10. A high-strength VLP copper foil for ultra-high-precision PCB, characterized in that: It is prepared by the method according to any one of claims 1 to 9.

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