Preparation method of anti-fracturing electrolytic rolled copper foil

Abstract

The invention relates to a preparation method of an anti-fracturing electrolytic rolled copper foil, which comprises the following steps: (1) adding an additive into a copper sulfate electrolyte, and electrolyzing to obtain a copper foil; wherein the additive is polyethylene glycol 1000; (2) putting the copper foil obtained in the step (1) into a bell furnace for high-low temperature circulating heat treatment, and taking out the copper foil after the copper foil is cooled to room temperature; (3) carrying out multi-pass finish rolling on the copper foil obtained in the step (2); and (4) the finish-rolled copper foil is sequentially subjected to degreasing treatment to remove oil stains on the surface, pure water washing, acid pickling to remove surface oxides, roughening growth of copper nodules, solidification and fixation of the copper nodules, blackening nickel plating, ashing zinc plating, passivation chromium plating and surface silane coupling agent coating treatment, and the anti-fracturing electrolytic rolled copper foil is obtained. The technical problem that in the prior art, rolling treatment is conducted after a grain refining mode is adopted in the electrolysis process, and pressing cracking is likely to happen when rolling is conducted is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic rolled copper foil, and particularly relates to a preparation method of an electrolytic rolled copper foil with crack resistance. Background Art

[0002] Copper foils can be divided into lithium battery copper foils and printed circuit copper foils according to their uses. Lithium battery copper foils are used in lithium batteries, serving as both the carrier of the negative electrode active material and the collector and transporter of the negative electrode electron flow; printed circuit copper foils are mainly used on printed circuit boards (PCBs). In the prior art, the main production methods of copper foils are electrolysis and rolling. In the electrolysis method, copper is first dissolved to form a solution, and then copper sulfate electrolyte is electrodeposited into a raw foil under the action of direct current in a foil-making machine; the rolling method is a product formed by repeatedly rolling and annealing high-precision copper strips using the principle of plastic processing. The production cost of electrolytic copper foil is relatively low, and the ductility of rolled copper foil products is better. The existing methods for producing copper foils generally use pure electrolysis or pure rolling. The copper foils prepared by pure electrolysis have relatively high surface roughness, poor bending resistance and elongation. The copper foils prepared by pure rolling are limited by the cost of the entire set of copper melting ingot and hot pressing forming equipment. Both of these methods have limitations, and the production process that combines the two and is compatible with the advantages of both methods is not yet mature.

[0003] During the preparation of copper foils produced by combining electrolysis and rolling in the prior art, when transferring to rolling after electrolysis, since the grains of electrolytic copper foil are relatively fine and there are many grain boundaries, it is easy to be cracked under roll pressure. Therefore, how to improve the problem of roll cracking of electrolytic rolled copper foil is the key to realizing the advantages of compatible electrolysis and rolling methods. Chinese Patent Application No. 201510226794.8 directly rolls after electrolytic raw foil production and then performs heat treatment, simply combining the two processes without reasonably optimizing the electrolysis step and the electrolytic transition rolling step, and cracking still occurs during rolling. Chinese Patent Application No. 201710384174.6 adds conventional brightener sodium polydithiopropanesulfonate and leveling agent 2-mercaptobenzimidazole in the raw foil electrolysis step. The two can promote copper grain nucleation and reduce grain size. Such a way of refining grains is applicable to the pure electrolysis process, but it is also part of the reason for roll cracking during rolling. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of an electrolytic rolled copper foil with crack resistance, which solves the technical problem that the copper foil is easily cracked under roll pressure when the grain refinement method in the electrolysis process of the prior art is used for rolling treatment.

[0005] The present invention provides a preparation method of an electrolytic rolled copper foil with crack resistance, including the following steps: (1)Add an additive to the copper sulfate electrolyte and electrolyze to obtain a copper foil; wherein, the additive is polyethylene glycol 1000; (2)Place the copper foil obtained in step (1) into a bell jar furnace for high and low temperature cyclic heat treatment. After cooling to room temperature, take out the copper foil; (3)Perform multi-pass precision rolling on the copper foil obtained in step (2); (4)Successively degrease the precision rolled copper foil to remove surface oil stains, perform pure water washing, pickling to remove surface oxides, roughen to grow copper nodules, solidify to fix the copper nodules, blacken by nickel plating, ashing by zinc plating, passivate by chromium plating, and perform surface coating treatment with a silane coupling agent to obtain a crack-resistant electrolytic rolled copper foil.

[0006] Preferably, the content of polyethylene glycol 1000 in step (1) is 20 - 50 mg / L.

[0007] Preferably, the electrolysis process parameters in step (1) are: wire speed is 0.4 - 0.7 m / min, electrolysis current is 15 - 25 KA, electrolyte temperature is 50 - 65 °C, and current density is 3000 - 7000 A / m 2 。

[0008] Preferably, nitrogen is introduced into the bell jar furnace in step (2) for protection.

[0009] Preferably, the process curve of the high and low temperature cyclic heat treatment in step (2) is set as follows: ① Set the temperature to 350 - 450 °C, the heating time is 40 - 45 min, the heat preservation time is 1 - 2 h, and then cool to 150 - 200 °C; ② Keep the temperature at 150 - 200 °C for 1 - 2 h, heat up to 350 - 450 °C, the heating time is 20 - 25 min, the heat preservation time is 1 - 2 h, and then cool to 150 - 200 °C; ③ Keep the temperature at 150 - 200 °C for 1 - 2 h, and then cool to room temperature.

[0010] Preferably, the number of precision rolling passes in step (3) is determined according to the required product thickness.

[0011] Beneficial effects (1)The additive in the electrolytic raw foil of the present invention is only polyethylene glycol 1000. As an inhibitor, polyethylene glycol 1000 acts synergistically with chloride ions to enhance the adsorption and inhibition functions, inhibit the electrodeposition of copper, reduce the non-uniform deposition phenomenon caused by the difference between high and low currents, and reduce the nucleation rate of copper, thereby further increasing the size of individual grains.

[0012] (2)When electrolyzing the raw foil of the present invention, a small current is passed and the wire speed is also adjusted to be small. By depositing slowly with a small current and a small wire speed, copper grains have more time to grow.

[0013] (3) In the electrolytic transition rolling step of the present invention, a high-low temperature cyclic heat treatment process is adopted, which can not only completely release the surface stress before rolling, but also promote the migration movement of grain boundaries, engulf surrounding grains, and further increase the grain size. Specific Embodiments

[0014] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0015] Example 1 Step a, electrolytic copper foil production. The copper sulfate electrolyte obtained after dissolving copper is filtered through a three-stage filtration system of a diatomite filter, a security filter, and a precision filter. The concentration of Cu in the copper sulfate electrolyte is 95 g / L, and the concentration of H2SO4 is 110 g / L. Weigh 30 mg / L of polyethylene glycol 1000 and add it to the additive preparation tank, and configure concentrated hydrochloric acid into a dilute hydrochloric acid aqueous solution with a concentration of 8 mg / L. The additive solution and the hydrochloric acid solution are injected into the precision filter through a peristaltic pump, mixed evenly with the electrolyte, and after filtration, are supplied to the electrolytic copper foil machine. By adjusting the linear velocity, an electrolytic copper foil with a thickness of 70 μm is continuously deposited on the surface of the cathode titanium roll. The linear velocity is 0.6 m / min, the electrolytic current is 20 KA, the electrolyte temperature is 58 °C, and the current density is 5000 A / m 2+ . 2 .

[0016] Step b, high-low temperature cyclic heat treatment. The copper foil produced by electrolysis is placed in a bell jar furnace filled with nitrogen for high-low temperature cyclic heat treatment. Set the heat treatment process as follows: ① Set the temperature to 400 °C, the heating time is 40 min, the holding time is 2 h, and then cool to 180 °C; ② Hold at 180 °C for 1 h, heat up to 400 °C, the heating time is 20 min, the holding time is 1 h, and then cool to 180 °C; ③ Hold at 180 °C for 1 h, and then cool to room temperature. After cooling to room temperature, take out the copper foil roll.

[0017] Step c: Rolling. The taken-out copper foil roll is subjected to three passes of finish rolling. The inlet thickness of the first finish rolling is 70 μm, the outlet thickness is 44 μm, and the reduction ratio is 37.1%; the inlet thickness of the second finish rolling is 44 μm, the outlet thickness is 28 μm, and the reduction ratio is 36.4%; the inlet thickness of the third finish rolling is 28 μm, the outlet thickness is 18 μm, and the reduction ratio is 35.7%.

[0018] Step d: Surface treatment. The rolled copper foil coils are successively subjected to degreasing to remove the oil on the surface, pure water washing, pickling to remove the surface oxides, roughening to grow copper nodules, curing to fix the copper nodules, blackening by nickel plating, ashing by zinc plating, passivation by chromium plating, and surface coating with a silane coupling agent, and then dried and wound up to obtain a copper foil with a thickness of 18 μm. Among them, the concentration of H2SO4 for pickling is 140 g / L, the flow rate is 10 m 3 / h, and the pretreatment time is 8 S; the concentration of Cu for roughening is 2+ 10 g / L, the concentration of H2SO4 is 140 g / L, and the electroplating time is 8 s; the concentration of Cu for curing is 2+ 50 g / L, and the electroplating time is 8 s; the concentration of Ni for blackening is 2+ 5 g / L, the pH of the blackening solution is 8, and the electroplating time is 8 s; the concentration of Zn for ashing is 2+ 3 g / L, the pH of the ashing solution is 8, and the electroplating time is 8 s; the concentration of Cr for passivation is 6+ 1 g / L, the pH of the passivation solution is 11, and the electroplating time is 8 s; by combining spraying and roller coating, an epoxy-based silane coupling agent is coated on both the treated surface and the non-treated surface of the copper foil.

[0019] Step e: The obtained finished copper foil is subjected to a tensile elongation test at room temperature and a bending resistance test after annealing (180 °C, 60 min). The average grain size is analyzed and calculated for the cross-section perpendicular to the length direction of the rolled copper foil by the EBSD method.

[0020] Example 2 The difference between Example 2 and Example 1 lies in Step c. Step c, rolling. The washed copper foil coils are subjected to four passes of precision rolling, and the thickness of the copper foil after precision rolling is 12 μm. The inlet thickness of the first precision rolling is 70 μm, the outlet thickness is 44 μm, and the reduction ratio is 37.1%; the inlet thickness of the second precision rolling is 44 μm, the outlet thickness is 28 μm, and the reduction ratio is 36.4%; the inlet thickness of the third precision rolling is 28 μm, the outlet thickness is 18 μm, and the reduction ratio is 35.7%; the inlet thickness of the fourth precision rolling is 18 μm, the outlet thickness is 12 μm, and the reduction ratio is 33.3%.

[0021] Example 3 The difference between Example 3 and Example 1 lies in Step c. Step c, rolling. The washed copper foil coils are subjected to five passes of precision rolling, and the thickness of the copper foil after precision rolling is 9 μm. The inlet thickness of the first precision rolling is 70 μm, the outlet thickness is 44 μm, and the reduction ratio is 37.1%; the inlet thickness of the second precision rolling is 44 μm, the outlet thickness is 28 μm, and the reduction ratio is 36.4%; the inlet thickness of the third precision rolling is 28 μm, the outlet thickness is 18 μm, and the reduction ratio is 35.7%; the inlet thickness of the fourth precision rolling is 18 μm, the outlet thickness is 12 μm, and the reduction ratio is 33.3%; the inlet thickness of the fifth precision rolling is 12 μm, the outlet thickness is 9 μm, and the reduction ratio is 25%.

[0022] Example 4 The only difference between Example 4 and Example 1 is that the content of polyethylene glycol 1000 in step a is 20 mg / L.

[0023] Example 5 The only difference between Example 5 and Example 1 is that the content of polyethylene glycol 1000 in step a is 50 mg / L.

[0024] Example 6 The difference between Example 6 and Example 1 lies in step b. Step b, high and low temperature cycle heat treatment. The copper foil produced by electrolytic copper foil is placed in a bell jar furnace with nitrogen protection for high and low temperature cycle heat treatment. Set the heat treatment process, which are in turn: ① Set the temperature at 350 °C, the heating time is 40 min, the holding time is 2 h, and then cool to 180 °C; ② Hold at 180 °C for 1 h, heat up to 350 °C, the heating time is 20 min, the holding time is 1 h, and then cool to 180 °C; ③ Hold at 180 °C for 1 h, and then cool to room temperature. After cooling to room temperature, take out the copper foil roll.

[0025] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the electrolytic additive of the prior art is used in step a, specifically: the concentration of tetrahydrothiazole thione copper is 10 mg / L, the concentration of polyethylene glycol 1000 is 30 mg / L, the concentration of gelatin is 40 mg / L, and the concentration of sodium polydithiopropanesulfonate is 100 mg / L. As a result, during the third pass of precision rolling in step c, it was cracked by the pressure roller and needed to be scrapped and reworked, and there was no subsequent step.

[0026] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that high and low temperature cycle heat treatment is not carried out in step b. As a result, during the third pass of precision rolling in step c, there were visible cracks on the copper foil and it needed to be scrapped and reworked, and there was no subsequent step.

[0027] Table 1 Test Results of Experimental Examples and Comparative Examples It can be seen from the test results in the above table that the copper foil manufactured by the method of the present invention has a room temperature tensile strength greater than 300 MPa, an elongation greater than 20%, the number of times of bending resistance after annealing at 180 °C for 60 min is greater than 1300, and the average grain size is greater than 2.2 μm. When using the electrolytic additive formula of the prior art, during the third pass of precision rolling in step c, it was cracked by the pressure roller and could not be tested; when high and low temperature cycle heat treatment was not carried out before rolling, it would also be cracked by the pressure roller.

[0028] In the electrolytic copper foil production step of the solution of the present invention, it is inconsistent with the existing idea of preparing copper foil by electrolysis. The composite additives used in the prior art are designed to refine the grains to improve the tensile strength and prepare copper foil with fine grains. Without undergoing rolling treatment, it is directly subjected to surface treatment and slitting and then applied. In order to have excellent elongation, bending resistance and low roughness, the rolling treatment method stands out. However, if the method of refining grains in the existing electrolysis process is adopted and then rolling treatment is carried out, it is easy to be cracked under rolling. But if grain refinement is not carried out during electrolysis to allow larger-sized grains to grow, and the large-sized grains have fewer grain boundaries and stronger plasticity, they have stronger anti-cracking ability during rolling.

Claims

1. A preparation method of a crack-resistant electrolytic rolled copper foil, comprising the following steps: (1) Add an additive to the copper sulfate electrolyte and electrolyze to obtain a copper foil; among them, The additive is polyethylene glycol 1000; (2) Place the copper foil obtained in step (1) into a bell jar furnace for high and low temperature cyclic heat treatment. After cooling to room temperature, take out the copper foil; (3) Perform multi-pass precision rolling on the copper foil obtained in step (2); (4) Sequentially perform degreasing treatment on the precision rolled copper foil to remove surface oil stains, pure water washing, pickling to remove surface oxides, roughening to grow copper nodules, curing to fix copper nodules, blackening by nickel plating, ashing by zinc plating, passivation by chromium plating, and surface coating treatment with a silane coupling agent to obtain a crack-resistant electrolytic rolled copper foil.

2. The preparation method according to claim 1, characterized in that: The content of polyethylene glycol 1000 in step (1) is 20 - 50 mg / L.

3. The preparation method according to claim 1, characterized in that: The electrolysis process parameters in the step (1) are as follows: the linear velocity is 0.4 - 0.7 m / min, the electrolysis current is 15 - 25 KA, the electrolyte temperature is 50 - 65 °C, and the current density is 3000 - 7000 A / m 2 .

4. The preparation method according to claim 1, characterized in that: Nitrogen is introduced into the bell jar furnace in step (2) for protection.

5. The preparation method according to claim 1, characterized in that: The process curve of the high and low temperature cyclic heat treatment in step (2) is set as follows: ① Set the temperature at 350 - 450 °C, the heating time is 40 - 45 min, the holding time is 1 - 2 h, and then cool to 150 - 200 °C; ② Hold at 150 - 200 °C for 1 - 2 h, heat up to 350 - 450 °C, the heating time is 20 - 25 min, the holding time is 1 - 2 h, and then cool to 150 - 200 °C; ③ Hold at 150 - 200 °C for 1 - 2 h, and then cool to room temperature.

6. The preparation method according to claim 1, wherein: The number of precision rolling passes in step (3) is determined according to the required product thickness.

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