Method for roughening the surface of an electrolytic copper foil

Abstract

The present application relates to a kind of electrolytic copper foil micro-roughening surface treatment method, mainly including surface micro-etching pretreatment and additive auxiliary pulse micro-roughening processing.The present application can effectively increase the specific surface area of processing surface, be favorable to promote the peel strength between electrolytic copper foil and prepreg, to ensure the reliability in the processing process of copper-clad plate;At the same time, the lower roughness not only helps to reduce the risk of roughening organization etching residue, and is favorable to reduce the adverse effects of skin effect on signal transmission.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuit material processing, and specifically relates to a method for micro-roughening surface treatment of electrolytic copper foil. Background Technology

[0002] Copper foil is one of the key materials for copper-clad laminates (CCL) and printed circuit boards (PCBs), widely used in electronic circuits, aerospace, and other fields. In recent years, with the rapid development of the electronic information industry (including the Internet of Things, cloud computing, and smartphones), human life has entered the digital age. As a key material for electronic and signal transmission, PCBs used in high-frequency and high-speed communication have gradually become a research hotspot. CCL is the basic material of PCBs, and copper foil, resin, and fiberglass cloth are the three major raw materials of CCL. The performance of copper foil directly affects the performance of PCBs. Currently, high-end electronic circuit copper foil not only requires excellent signal transmission performance but also low roughness. Therefore, electronic circuit copper foil used in high-end PCBs needs to balance low roughness and sufficient peel strength. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for micro-roughening surface treatment of electrolytic copper foil. The copper foil treated by this process has low roughness while retaining good peel strength and oxidation resistance.

[0004] This invention provides a method for micro-roughening the surface of electrolytic copper foil, comprising the following steps:

[0005] Step 1: Perform micro-etching pretreatment on the surface of the electrolytic copper foil;

[0006] Step 2: Additive-assisted pulse micro-fine roughening treatment;

[0007] Step 3, curing treatment;

[0008] Step four: blackening nickel plating, graying zinc plating, and passivation chromium plating;

[0009] Step 5: Apply silane coupling agent and dry.

[0010] The micro-etching pretreatment uses a mixed solution of phosphoric acid and sulfuric acid, with a phosphoric acid concentration of 40–150 g / L and a sulfuric acid concentration of 40–150 g / L. The purpose of micro-etching is to micro-etch the rough surfaces of the copper foil, creating uniform and fine corrosion pits, increasing the specific surface area, and increasing the number of nodular coarsened particles.

[0011] The micro-etching pretreatment temperature is 20–30°C, and the time is 3–10 seconds.

[0012] The additive is one or more of gelatin (molecular weight Mw 10,000-100,000), collagen, sodium tungstate, sodium citrate, and trithiocyanate, and is used in an amount of 1-100 ppm.

[0013] The pulsed micro-roughening process includes primary roughening, secondary roughening, and tertiary roughening; all roughening solutions contain additives; and electrochemical deposition is performed using pulsed unidirectional square wave current during the roughening process.

[0014] The current density for the first-stage coarsening is 10–40 A / dm. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%; the current density of the secondary coarsening is 10–35 A / dm³. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%; the current density of the three-stage coarsening is 10–35 A / dm³. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%.

[0015] The curing process corresponds to pulse micro-roughening treatment, including primary curing, secondary curing, and tertiary curing; the same curing solution is used, wherein Cu 2+ The concentration is 40–200 g / L, the H2SO4 concentration is 60–200 g / L, and the temperature range is 30–60 °C. During the curing process, a pulsed unidirectional square wave current is used for electrochemical deposition.

[0016] The current density for the first-stage curing is 10–40 A / dm³. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%; the current density for the secondary curing is 10–35 A / dm³. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%; the current density of the three-stage curing is 10–35 A / dm³. 2 The pulse frequency is 100–3000 Hz, and the duty cycle is 20–60%.

[0017] The surface-treated electrolytic copper foil has a coarsened particle morphology that is spherical, with a particle size between 300-700 nm.

[0018] The blackening nickel plating solution is an alkaline electroplating solution with a temperature of 25–50°C. 2+ The concentration was 0.8±0.5 g / L, the pH value was 10±2.0, the potassium pyrophosphate concentration was 10~100 g / L, and the current density was 0.1~1.0 A / dm³. 2Potassium pyrophosphate is mainly used to stabilize the pH of the solution; the nickel plating layer acts as a barrier layer to prevent the resin from directly contacting the copper during hot pressing and causing a chemical reaction that would generate gas and reduce the copper foil's peel resistance.

[0019] The ashing zinc plating solution is an alkaline electroplating solution with a temperature range of 25–50°C. (Zn) 2+ The concentration was 1±0.5 g / L, the pH value was 10±2.0, the potassium pyrophosphate concentration was 10~100 g / L, and the current density was 0.1~1.0 A / dm³. 2 The purpose of ashing zinc plating is to increase the protection of the Cu crystal structure during the pressing of copper-clad laminates, and to prevent the amines produced by the decomposition of the curing agent dicyandiamide from reacting with the bare copper phase at high temperatures, generating water vapor and causing bubbles, which would separate the copper foil from the prepreg. At the same time, zinc plating can also improve the high-temperature oxidation resistance of the copper foil.

[0020] The passivation chromium plating solution is an alkaline electroplating solution, with a temperature of 25–50℃, a hexavalent chromium concentration of 1 ± 0.5 g / L, a pH value of 10 ± 2.0, and a current density of 0.1–1.0 A / dm³. 2 Electroplated chromium can form a passivation film on the surface of copper foil, improving the copper foil's ability to resist oxidation in air at room temperature.

[0021] The aqueous solution of silane coupling agent was sprayed onto the surface of the electrolytic copper foil using a spray method, and then the copper foil was dried in an oven at 200°C. The silane coupling agent was KBM-403, and the solution concentration was 2–10 g / L.

[0022] Beneficial effects

[0023] (1) The present invention can effectively increase the specific surface area of ​​the processed surface, which is beneficial to improve the peel strength between the electrolytic copper foil and the prepreg, thereby ensuring the reliability of the copper clad laminate processing; at the same time, the lower roughness not only helps to reduce the risk of etching residue of the roughened structure, but also helps to reduce the adverse effect of the skin effect on signal transmission.

[0024] (2) In the roughening process, additives are added to the present invention to electrodeposit submicron copper particles, which effectively increases the specific surface area of ​​the processed surface. (3) The copper foil of the present invention has low roughness and excellent anti-peel properties, which is suitable for halogen-free and lead-free soldering production of PCBs; it has a uniform appearance and excellent room temperature oxidation resistance and high temperature (200℃+60min) oxidation resistance; it has excellent chemical resistance and etching properties, which is suitable for ultra-fine circuits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0026] Figure 2This is a 5000x SEM image of the copper foil before surface treatment in Example 1.

[0027] Figure 3 This is a 3D laser morphology photograph of the copper foil before surface treatment in Example 1;

[0028] Figure 4 This is a 5000x SEM image of the electrolytic copper foil after surface treatment in Example 1.

[0029] Figure 5 This is a 3D laser morphology photograph of the surface of the electrolytic copper foil after surface treatment in Example 1;

[0030] Figure 6 This is a cross-sectional SEM image of the electrolytic copper foil after surface treatment in Example 1. Detailed Implementation

[0031] 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.

[0032] Example 1

[0033] This embodiment provides a micro-roughening surface treatment process for electrolytic copper foil, including the following process steps:

[0034] (1) Using electronic circuit foil (35μm) as the base foil, the base foil was placed in a mixed solution containing 60g / L phosphoric acid and 60g / L H2SO4 for acid washing pretreatment. The acid washing temperature was 30℃ and the treatment time was 5s.

[0035] (2) Roughening: The copper foil processed in step (1) is roughened under the following process conditions: Roughening solution: Cu 2+ The concentration was 15 g / L, the H2SO4 concentration was 110 g / L, and the temperature was 25°C. The roughening process was performed using a pulsed unidirectional square wave current electroplating, with a first-stage roughening current density of 30 A / dm². 2 The pulse frequency is 1000Hz, the duty cycle is 50%, and the current density for the second-stage coarsening is 20A / dm². 2 The pulse frequency is 1000Hz, the duty cycle is 50%, and the current density for the third-stage coarsening is 15A / dm. 2 The pulse frequency was 1000Hz, and the duty cycle was 50%. The processing time was 5 seconds for all samples. The roughening solution contained additive M at a concentration of 20 ppm. Additive M was a mixture of sodium citrate and cyanuric acid, with a citric acid to cyanuric acid ratio of 3:1.

[0036] (3) Curing: The first-stage curing, second-stage curing, and third-stage curing all use the same curing liquid, and the Cu in the curing liquid... 2+ The concentration was 50 g / L, the H2SO4 concentration was 100 g / L, and the temperature was 45℃. The roughening process was performed using a pulsed unidirectional square wave current electroplating, with a first-stage curing current density of 35 A / dm³. 2 The pulse frequency is 1000Hz, the duty cycle is 50%, and the current density for secondary curing is 25A / dm³. 2 The pulse frequency is 1000Hz, the duty cycle is 50%, and the current density for three-stage curing is 15A / dm³. 2 The pulse frequency is 1000Hz, and the duty cycle is 50%. The processing time is 5 seconds.

[0037] (4) Nickel plating: After step (3) is completed, the copper foil is washed with water and then blackened for nickel plating. The specific parameters are as follows: Ni in the nickel plating blackening solution 2+ The concentration was 0.8 g / L, the potassium pyrophosphate concentration was 60 g / L, the temperature was 30℃, the pH value was 10.1, and the current density was 0.2 A / dm³. 2 The processing time is 5 seconds.

[0038] (5) Zinc plating: After step (4) is completed, the copper foil is washed with water and then subjected to ashing zinc plating. The specific parameters are as follows: Zn in the zinc plating ashing solution 2+ The concentration was 1.5 g / L, the pH was 11.2, the potassium pyrophosphate concentration was 50 g / L, the temperature was 30℃, and the current density was 0.1 A / dm³. 2 The processing time is 5 seconds, and the copper foil is washed with water after processing.

[0039] (6) Chromium plating: After step (5) is completed, the copper foil is passivated and chromium plating is performed. The specific parameters are as follows: the concentration of hexavalent chromium in the chromium plating passivation solution is 1.0 g / L, the pH value is 11.4, the temperature is 40℃, and the current density is 0.2 A / dm³. 2 The processing time is 5 seconds, and the copper foil is washed with water after processing.

[0040] (7) Silane coupling agent coating: A 5 g / L silane coupling agent KBM-403 aqueous solution is uniformly coated onto the copper foil surface by spraying for 5 seconds, and then dried in an oven at 200°C.

[0041] Example 2

[0042] The difference from Example 1 is that the frequency of the pulsed unidirectional square wave current is adjusted to 2000Hz, the duty cycle is 25%, and the current density of the first-stage coarsening is 30A / dm. 2 The current density for the second-order coarsening is 20 A / dm. 2The current density for the third-stage coarsening is 15 A / dm. 2 Everything else is the same as in Example 1.

[0043] Example 3

[0044] The difference from Example 1 is that the pretreatment solution, which originally had a phosphoric acid concentration of 60 g / L and an H2SO4 concentration of 60 g / L, was adjusted to a mixed solution with a phosphoric acid concentration of 100 g / L and an H2SO4 concentration of 100 g / L for acid washing. The acid washing temperature was 30°C, and the treatment time was 5 seconds. All other aspects were the same as in Example 1.

[0045] Example 4

[0046] The difference from Example 1 is that the additive M in the roughening solution is collagen and sodium tungstate, with the ratio of collagen to sodium tungstate being 1:1, and the concentration of additive M being 20 ppm. Everything else is the same as in Example 1.

[0047] Comparative Example 1

[0048] The electronic circuit foil (35μm) adopts the traditional copper foil surface treatment process of pickling, roughening, curing, roughening, curing, roughening, curing, blackening zinc plating, graying zinc plating, passivation chromium plating, silane coating, and drying.

[0049] 1) The original foil was placed in a mixed solution containing 60 g / L phosphoric acid and 60 g / L H2SO4 for acid washing pretreatment. The acid washing temperature was 30℃ and the treatment time was 5 s.

[0050] 2) Coarsening, Cu in the coarsening solution 2+ The concentration of H₂SO₄ was 110 g / L, the temperature was 25℃, and the treatment time was 5 seconds. All roughening processes were performed using direct current electroplating, with a first-stage roughening current density of 30 A / dm². 2 The current density for the second-order coarsening is 20 A / dm. 2 The current density for the third-stage coarsening is 15 A / dm. 2 No additives are used in the roughening solution.

[0051] 3) Curing: Cu in the curing solution 2+ The concentration was 50 g / L, the H2SO4 concentration was 100 g / L, the temperature was 45℃, and the treatment time was 5 seconds. All curing processes involved direct current electroplating, with a first-stage curing current density of 35 A / dm³. 2 The current density for secondary curing is 25 A / dm³. 2 The current density for three-stage curing is 15 A / dm³. 2 .

[0052] 4) Nickel plating: After washing with water, the copper foil undergoes blackening nickel plating. Specific parameters are as follows: temperature 30℃, Ni... 2+The concentration is 0.8 g / L.

[0053] The pH value is 10.1, the potassium pyrophosphate concentration is 60 g / L, and the current density is 0.2 A / dm³. 2 The processing time is 5 seconds.

[0054] 5) Zinc plating: After washing with water, the copper foil undergoes ashing zinc plating. Specific parameters are as follows: temperature 30℃, Zn... 2+ The concentration is 1.5 g / L.

[0055] pH 11.2, potassium pyrophosphate concentration 50 g / L, current density: 0.1 A / dm³ 2 The processing time is 5 seconds.

[0056] 6) Chromium plating: After step 5), the copper foil undergoes passivation chromium plating. Specific parameters are as follows: temperature 40℃, hexavalent chromium concentration 1.0 g / L, pH value 11.3, and current density 0.2 A / dm³. 2 The processing time is 5 seconds.

[0057] 7) Silane coupling agent coating: A 5 g / L aqueous solution of silane coupling agent KBM-403 is uniformly coated onto the copper foil surface by spraying for 5 seconds, and then dried in an oven at 200°C.

[0058] The electrolytic copper foils prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0059] Table 1. Comparison of process parameters and performance of copper foil preparation in the examples and comparative examples

[0060]

[0061] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A micro-roughening surface treatment method for electrolytic copper foil, comprising the following steps: Step one, micro-etching pretreatment of the surface of electrolytic copper foil; Step two, additive-assisted pulse micro-roughening treatment; wherein, The pulse micro-roughening treatment includes primary roughening, secondary roughening and tertiary roughening; the roughening liquid used contains an additive; the electrochemical deposition is carried out by using a pulse unidirectional square wave current in the roughening process; the current density of the primary roughening is 10-40 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%; the current density of the secondary roughening is 10-35 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%; the current density of the tertiary roughening is 10-35 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%. Step three, solidification treatment; wherein the solidification treatment corresponding to the pulse micro-roughening treatment includes primary solidification, secondary solidification and tertiary solidification; the same solidification liquid is used, wherein Cu 2+ The concentration of H2SO4 is 40-200 g / L, the concentration of H2SO4 is 60-200 g / L, and the temperature range is 30-60℃; a pulse unidirectional square wave current is used in the solidification process for electrochemical deposition; the current density of the primary solidification is 10-40 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%; the current density of the secondary solidification is 10-35 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%; the current density of the tertiary solidification is 10-35 A / dm 2 , the pulse frequency is 100-3000 Hz, and the duty cycle is 20-60%. Step four, blackening, nickel plating, graying, zinc plating, passivation, and chromium plating; Step five, silane coupling agent coating, and drying.

2. The method of claim 1, wherein: The micro-etching pretreatment uses a mixed solution of phosphoric acid and sulfuric acid, with a phosphoric acid concentration of 40-150 g / L and a sulfuric acid concentration of 40-150 g / L.

3. The method of claim 1, wherein: The micro-etching pretreatment temperature is 20-30℃, and the time is 3-10 s.

4. The method of claim 1, wherein: The additive is one or more of gelatin, collagen, sodium tungstate, sodium citrate, and thiocyanic acid, with a dosage of 1-100 ppm.

5. The method of claim 1, wherein: The black nickel plating solution is an alkaline plating solution, with a temperature of 25-50℃, a Ni 2+ concentration of 0.8±0.5g / L, a pH value of 10±2.0, a potassium pyrophosphate concentration of 10-100g / L, and a current density of 0.1-1.0A / dm 2 ; the grey zinc plating solution is an alkaline plating solution, with a temperature of 25-50℃, a Zn 2+ concentration of 1±0.5g / L, a pH value of 10±2.0, a potassium pyrophosphate concentration of 10-100g / L, and a current density of 0.1-1.0A / dm 2 ; the passivation chromium plating solution is an alkaline plating solution, with a temperature of 25-50℃, a hexavalent chromium concentration of 1±0.5g / L, a pH value of 10±2.0, and a current density of 0.1-1.0A / dm 2 .

6. The method of claim 1, wherein: The silane coupling agent aqueous solution is sprayed on the treated surface of the electrolytic copper foil using a spraying method, and then the copper foil is dried in a 200℃ oven.

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