CN114921817B - Ultra-thin electrolytic copper foil and its preparation method and application - Google Patents

Abstract

The invention relates to the technical field of copper foil, in particular to an ultrathin electrolytic copper foil and a preparation method and application thereof. The preparation method of the ultrathin electrolytic copper foil comprises the following steps: (1) Placing a cathode and an anode in a copper-containing electrolyte, and electrifying to perform electrolytic treatment to obtain a green foil; (2) Placing the raw foil in an aqueous solution containing an antioxidant, washing with water, drying, and performing surface ionization treatment; wherein in step (1), the conductive glass is immersed in an aqueous solution containing a conductive polymer for pretreatment and dried to serve as the cathode. The obtained ultrathin electrolytic copper foil has good oxidation resistance and mechanical property, and can meet the requirement of the current chip packaging and 5G communication field on the light weight of the copper foil.

Description

Ultra-thin electrolytic copper foil and its preparation method and application

Technical Field

The present invention relates to the technical field of copper foil, and in particular to an ultra-thin electrolytic copper foil and a preparation method and application thereof.

Background technique

With the rapid development of the electronic information industry, the use of electrolytic copper foil is increasing. The products are widely used in aerospace, communication equipment, lithium-ion batteries, new energy vehicles and other fields. The domestic and foreign markets have increasing demand for electrolytic copper foil, especially high-performance electrolytic copper foil. The expansion of new functions and performance improvement of modern electronic equipment have led to an increasing number of components, occupying more internal space. In addition to its application in power batteries and circuit boards, electrolytic copper foil will open up more application space in high-end application fields. Therefore, the development trend of copper foil materials has put forward new requirements for thinness, low profile, high gloss and easy peeling.

When electrolytic copper foil is used in back-end products such as IC substrates, lithium-ion batteries, and 5G signal high-frequency and high-speed transmission, the first thing to do is to ensure that the required electrolytic copper foil is ultra-thin and low-profile (thickness ≤ 1.5μm). The low profile (surface roughness) of the copper foil is a key performance indicator that can ensure stable signal transmission, otherwise it will lead to large delays in high-frequency signal transmission and low efficiency. Secondly, the double-sided copper foil used in lithium-ion batteries has certain requirements for high-temperature resistance and oxidation resistance, tensile strength and elongation to ensure that the copper foil can be fully deformed when the negative electrode is flattened, otherwise it will cause the electrode to break easily, thereby affecting the battery's yield and cycle life. At the same time, the complete peeling of the copper foil layer and the cathode surface is also a challenge to the copper foil preparation technology. In industry, physical means are often required to peel the copper foil from the cathode. Sometimes the copper foil's adhesion is too high, which will cause the copper foil to tear easily and waste foil. However, the current ultra-thin electrolytic copper foil in China generally has problems such as high profile, poor oxidation resistance, and difficulty in completely peeling off the copper foil layer and the cathode surface. Therefore, the development of low-profile, high-oxidation-resistance, and easy-to-peel ultra-thin copper foil preparation technology suitable for high-end product applications can not only ensure the signal transmission rate, reduce the loss of signal transmission, and significantly improve the back-end application, but also save preparation costs and improve production efficiency. This will become a major research topic in the development of copper foil technology now and in the future.

At present, domestic electronic copper foil manufacturers often use chrome plating for anti-oxidation treatment. Although it has good heat resistance, wear resistance and chemical stability, hexavalent chromium is highly toxic and seriously pollutes the environment. With the emergence of new environmental protection forms in the country, electroplating is gradually developing towards chromium-free. The green and environmentally friendly surface treatment of copper foil products is a great challenge for the development of emerging industries in China. The research on high-performance ultra-thin copper foil is of great significance to the development of copper foil industry, electronics, communications, energy, transportation, aerospace, military and other industries.

Summary of the invention

The purpose of the present invention is to overcome the problems in the prior art that ultra-thin copper foil is difficult to peel off and has poor anti-oxidation performance, and to provide an ultra-thin electrolytic copper foil and a preparation method and application thereof.

In order to achieve the above-mentioned purpose, the first aspect of the present invention provides an ultra-thin electrolytic copper foil, wherein the copper foil has a thickness of 0.5-3 μm, a surface roughness R _z of 0.5-3.5 μm, a brightness of 60° of 180-250 GU, a tensile strength of 320-430 MPa, an elongation of 1.5-3.2%, and a surface tension of 65-78 mM/m or more; and does not change color when placed at 220°C for 2 hours.

A second aspect of the present invention provides a method for preparing an ultra-thin electrolytic copper foil, wherein the method comprises:

(1) placing a cathode and an anode in a copper-containing electrolyte, applying electricity for electrolysis, and obtaining a raw foil;

(2) soaking the raw foil in an aqueous solution containing an antioxidant, washing it with water, drying it, and then performing a surface ionization treatment;

Wherein, in step (1), the conductive glass is immersed in an aqueous solution containing a conductive polymer for pretreatment and dried to serve as the cathode.

The third aspect of the present invention provides an ultra-thin electrolytic copper foil prepared by the method described in the second aspect.

A fourth aspect of the present invention provides an application of the ultra-thin electrolytic copper foil described in the third aspect in chip packaging.

Through the above technical solution, the ultra-thin electrolytic copper foil prepared by the method provided by the present invention has the following advantages:

(1) It can be automatically peeled off from the cathode during preparation, and the peeled copper foil is a double-sided copper foil, which solves the tearing phenomenon caused by the difficulty of peeling the copper foil in actual production;

(2) The copper foil is extremely thin, has high oxidation resistance, and good mechanical properties. It can be used for chip packaging. Compared with similar electrolytic copper foil for chip packaging, the volume and weight can be reduced by 50-70%, meeting the current requirements for lightweight copper foil in chip packaging and 5G communication fields;

(3) It has the characteristics of ultra-low profile (surface roughness _Rz is 0.5-3.5μm), which can speed up signal transmission and improve the stability of signal transmission when used in the communication field;

(4) The surface tension of copper foil is large (65-78mM/m), which shows hydrophilicity and has certain adhesion. It can be used in lithium batteries to improve the cycle capacity; it has certain peel strength and good performance when used in printed circuit boards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a scanning electron microscope (SEM) image of the ultra-thin copper foil of Example 1 (magnified 20,000 times);

FIG2 is a scanning electron microscope (SEM) image of a cross section of the ultra-thin copper foil of Example 1 (magnified 10,000 times);

3 is a scanning electron microscope (SEM) image of a cross section of the ultra-thin copper foil of Example 2 (magnified 10,000 times).

Detailed ways

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

The first aspect of the present invention provides an ultra-thin electrolytic copper foil, wherein the copper foil has a thickness of 0.5-3 μm, a surface roughness R _z of 0.5-3.5 μm, a brightness of 180-250 GU at 60°, a tensile strength of 320-430 MPa, an elongation of 1.5-3.2%, and a surface tension of 65-78 mM/m or more; and does not change color when placed at 220°C for 2 hours.

In the present invention, the thickness of the copper foil is obtained by a scanning electron microscope (SEM) of the model FEI MLA650F of the United States; the surface roughness of the copper foil is measured by a roughness meter of the model MARL PS-10 of Germany; the tensile strength and elongation of the copper foil are measured by a tensile testing machine of the model SHIMADZU of Japan AG-IS/1KN; the brightness is measured by a 3nh gloss meter of Shenzhen Sanenshi; the surface tension is measured by an A.Shine dyne pen of the United States; and the oxidation resistance is measured by heating in a DZ-1BCIV vacuum drying oven.

In the present invention, the copper foil is extremely thin, has high oxidation resistance, and good mechanical properties, and can be used for chip packaging. Compared with similar electrolytic copper foils for chip packaging, the volume and weight ratio can be reduced by 50-70%, meeting the current chip packaging and 5G communication fields. The requirements for lightweight copper foil; and it has an ultra-low profile (surface roughness _Rz is 0.5-3.5μm), and can be used in the communication field to accelerate signal transmission and improve signal transmission stability; the surface tension is large (65-78mM/m), showing hydrophilicity, and has certain adhesion, and can be used in lithium batteries to increase the cycle capacity; it has certain peel strength and good performance when used in printed circuit boards.

A second aspect of the present invention provides a method for preparing an ultra-thin electrolytic copper foil, wherein the method comprises:

(1) placing a cathode and an anode in a copper-containing electrolyte, applying electricity for electrolysis, and obtaining a raw foil;

(2) soaking the raw foil in an aqueous solution containing an antioxidant, washing it with water, drying it, and then performing a surface ionization treatment;

Wherein, in step (1), the conductive glass is immersed in an aqueous solution containing a conductive polymer for pretreatment and dried to serve as the cathode.

In the present invention, the conductive glass is produced by coating a layer of indium tin oxide (ITO) film on a soda-lime-based or silicon-boron-based substrate glass by magnetron sputtering.

In the present invention, conductive glass is defined as the cathode and is placed in a conductive polymer aqueous solution for pretreatment. Through the synergistic effect of the above technical means, the technical effect of copper foil self-peeling can be achieved, and the surface roughness _Rz of the copper foil can be controlled within 0.5-3.5μm.

In the present invention, the anode material can be selected from conventional anode electrode materials in the art; preferably, the anode material can be selected from pure copper plate, tantalum-titanium coated plate, tantalum-iridium-titanium coated plate or ruthenium-iridium-titanium ternary coated titanium plate.

In a preferred embodiment of the present invention, the pre-treatment time is 5-10s.

In a preferred embodiment of the present invention, the conductive polymer is selected from at least one of polypyrrole, polyaniline and polyphthalocyanine.

In a preferred embodiment of the present invention, the volume concentration of the aqueous solution of the conductive polymer is 2-4.5%.

In a preferred embodiment of the present invention, the preparation method of the copper-containing electrolyte comprises: adding a complexing agent and an auxiliary complexing agent to an alkaline solution to obtain a solution A; adding a copper-containing compound, a zinc-containing compound, an auxiliary metal compound, and a brightener to water to obtain a solution B, and then mixing the solution A and the solution B to obtain the copper-containing electrolyte.

In the present invention, by adding a brightener, the brightness of the copper foil prepared can reach 180-250GU at 60°.

In a preferred embodiment of the present invention, the alkali solution is an aqueous solution of alkali, and the alkali is sodium hydroxide and/or potassium hydroxide.

In a preferred embodiment of the present invention, the complexing agent is selected from at least one of potassium sodium tartrate, potassium tartrate, sodium tartrate, potassium pyrophosphate, sodium pyrophosphate, glycine, histidine, proline, cysteine, sodium sulfite, potassium sulfite, sodium bisulfite, and potassium bisulfite.

In a preferred embodiment of the present invention, the auxiliary complexing agent is selected from at least one of sodium citrate, potassium citrate and disodium citrate.

In a preferred embodiment of the present invention, the copper-containing compound is selected from at least one of copper sulfate, copper chloride and copper nitrate.

In a preferred embodiment of the present invention, the zinc-containing compound is selected from at least one of zinc sulfate, zinc chloride and zinc nitrate.

In a preferred embodiment of the present invention, the auxiliary metal in the auxiliary metal compound is selected from at least one of Bi, Sn, Sb, and Cd, and the auxiliary metal compound is selected from at least one of sulfates, chlorides, and nitrates of the auxiliary metal.

In a preferred embodiment of the present invention, the brightener is selected from at least one of 2-mercaptobenzimidazole, polyethyleneimine, thiourea, 2-mercaptopropionic acid, and thiomorpholine-3-carboxylic acid hydrochloride.

In a preferred embodiment of the present invention, the amount of the alkali solution, the complexing agent, the auxiliary complexing agent, the copper-containing compound, the zinc-containing compound, the auxiliary metal compound and the brightener is such that in the copper-containing electrolyte, the concentration of the alkali is 20-60 g/L, preferably 30-55 g/L;

The concentration of the complexing agent is 70-150 g/L, preferably 80-100 g/L;

The concentration of the auxiliary complexing agent is 5-50 g/L, preferably 10-40 g/L;

Calculated in terms of copper element, the concentration of the copper-containing compound is 10-60 g/L, preferably 30-50 g/L;

Calculated in terms of zinc element, the concentration of the zinc-containing compound is 10-25 g/L, preferably 11-15 g/L;

The concentration of the additive metal compound is 0.01-1 g/L, preferably 0.01-0.5 g/L, based on the additive metal;

The concentration of the brightener is 0.001-0.1 g/L, preferably 0.001-0.05 g/L.

In a preferred embodiment of the present invention, the electrolysis treatment uses a stabilized DC power supply.

In a preferred embodiment of the present invention, the current density of the electrolytic treatment is 0.5 A/dm ² -3.5 A/dm ² , preferably 0.5 A/dm ² -2 A/dm ² .

In a preferred embodiment of the present invention, the electrolytic treatment time is 400s-800s, preferably 500s-700s.

In a preferred embodiment of the present invention, the temperature of the electrolytic treatment is 40-60°C, preferably 40-55°C.

In a preferred embodiment of the present invention, the circulation rate of the copper-containing electrolyte is 1-10 L/min, preferably 2-8 L/min.

In the present invention, by limiting the electrolysis process parameters and using conductive glass as the cathode material, the copper foil obtained by electrodeposition has fine grains and a dense surface, thereby making the obtained copper foil have better mechanical properties, with a tensile strength of 320-430 MPa and an elongation of 1.5-3.2%.

In a preferred embodiment of the present invention, the antioxidant is selected from two or more of chromic anhydride, glucose, gluconic acid, galactose, fucose, sodium molybdate, potassium molybdate, zinc molybdate, bismuth molybdate, nickel sulfate, zinc sulfate, and chromium sulfate.

In a preferred embodiment of the present invention, the concentration of the antioxidant is 0.5-5 g/L, preferably 0.6-4 g/L.

According to the present invention, the surface ionization treatment of the raw foil can be carried out in a corona machine; preferably, the process of the surface ionization treatment includes: placing the raw foil between an anode and a cathode and applying a high voltage power supply; more preferably, the anode and cathode in the surface ionization treatment are selected from high temperature resistant, ozone resistant, high insulation silicone rubber rollers or ceramic rollers.

According to the present invention, during the surface ionization treatment process, the antioxidant molecules on the surface of the raw foil are oxidized and react with the free radicals generated by air ionization to form a physical barrier, thereby further achieving the purpose of surface oxidation protection.

In the present invention, the surface ionization treatment mainly relies on the activation of active ions such as electrons, ions, excited atoms and free radicals, so that the antioxidant on the surface of the copper foil reacts to form stable simple small molecules, which can effectively block oxygen from contacting the copper foil, achieve anti-oxidation effect, and at the same time increase the surface tension of the copper foil.

In a preferred embodiment of the present invention, the voltage of the surface ionization treatment is 1000-5000V and the power is 2-10kW.

The third aspect of the present invention provides an ultra-thin electrolytic copper foil prepared by the method described in the second aspect.

The structure and performance of the ultra-thin electrolytic copper foil are as described above and will not be described in detail.

A fourth aspect of the present invention provides an application of the ultra-thin electrolytic copper foil described in the third aspect in chip packaging.

The present invention will be described in detail below through examples.

In the following examples and comparative examples, the thickness of the copper foil was obtained by a scanning electron microscope (SEM) of the American FEI MLA650F model;

The surface roughness of the copper foil was measured using a German Mahr PS-10 roughness meter.

The tensile strength and elongation of copper foil were measured using a Japanese Shimadzu AG-IS/1KN tensile testing machine;

The brightness is measured using Shenzhen Sannh 3nh gloss meter;

The surface tension was measured using an American Aisha A. Shine dyne pen;

The oxidation resistance is measured using a DZ-1BCIV vacuum drying oven. In the DZ-1BCIV vacuum drying oven, the copper foil is heated at 150°C or 220°C. The higher the temperature, the longer the copper foil remains unchanged, and the higher its oxidation resistance.

Example 1

The complexing agent potassium sodium tartrate and the auxiliary complexing agent sodium citrate are added to a sodium hydroxide solution (the sodium hydroxide concentration is 50 g/L) to obtain a solution A; copper sulfate pentahydrate, zinc sulfate heptahydrate, Bi ₂ (SO ₄ ) ₃ , and 2-mercaptobenzimidazole are added to deionized water to obtain a solution B; the above-obtained solution A is mixed with the solution B, and deionized water is added to make up to the required volume to obtain a copper-containing electrolyte;

Wherein, in the copper-containing electrolyte, the concentration of sodium hydroxide is 50 g/L, the concentration of potassium sodium tartrate is 100 g/L, the concentration of sodium citrate is 20 g/L, the concentration of Cu ²⁺ is 40 g/L, the concentration of Zn ²⁺ is 11.5 g/L, the concentration of Bi ³⁺ is 0.2 g/L, and the concentration of 2-mercaptobenzimidazole is 0.002 g/L;

Conductive glass is pretreated in a polypyrrole aqueous solution with a volume concentration of 2% (pretreatment time is 8s) and used as a cathode. An iridium-coated titanium plate is used as an anode. A stabilized DC power supply is used to electrolyze the copper-containing electrolyte under stirring to obtain a raw foil. The electrolysis treatment conditions are: current density of 0.9A/ ^dm2 , deposition time of 600s, temperature of 45°C, and electrolyte circulation rate of 6L/min.

The raw foil is immersed in an aqueous solution containing chromic anhydride and glucose (chromic anhydride concentration is 0.8 g/L, glucose concentration is 3 g/L) for 30 seconds, then washed with water and air-dried at 80°C, and then placed between an anode and a cathode and a high voltage power supply is applied to perform surface ionization treatment to obtain an ultra-thin electrolytic copper foil; wherein the conditions for the surface ionization treatment are: a power of 2 kW, an instantaneous voltage of 1270 V, and the anode and cathode materials for the surface ionization treatment are both silicone rubber rollers.

The scanning electron microscope (SEM) image of the ultra-thin electrolytic copper foil prepared in this embodiment (magnified 20,000 times) is shown in Figure 1, and the scanning electron microscope (SEM) image of the cross-section of the ultra-thin electrolytic copper foil (magnified 10,000 times) is shown in Figure 2. It can be seen from Figure 1 that the surface of the ultra-thin copper foil prepared in this embodiment is complete, dense, and has no cracks. It can be seen from Figure 2 that the thickness of the copper foil is 1.241-1.376μm, which meets the requirements of ultra-thin copper foil.

Example 2

Adding complexing agent glycine and auxiliary complexing agent sodium citrate into sodium hydroxide solution (sodium hydroxide concentration is 50 g/L) to obtain solution A; adding copper sulfate pentahydrate, zinc sulfate heptahydrate, Sb ₂ (SO ₄ ) ₃ , and polyethyleneimine into deionized water to obtain solution B; mixing the above-obtained solution A with solution B, adding deionized water to make up to the required volume to obtain a copper-containing electrolyte;

Wherein, in the copper-containing electrolyte, the concentration of sodium hydroxide is 40 g/L, the concentration of glycine is 100 g/L, the concentration of sodium citrate is 20 g/L, the concentration of Cu ²⁺ is 50 g/L, the concentration of Zn ²⁺ is 13 g/L, the concentration of the auxiliary agent Sb ³⁺ is 0.3 g/L, and the concentration of polyethyleneimine is 0.002 g/L;

Conductive glass is pretreated in a polyaniline aqueous solution with a volume concentration of 2.5% (pretreatment time is 8s) and used as a cathode. An iridium-coated titanium plate is used as an anode. A stabilized DC power supply is used to electrolyze the copper-containing electrolyte under stirring to obtain a raw foil. The electrolysis treatment conditions are: current density of 1A/ ^dm2 , deposition time of 700s, temperature of 50°C, and electrolyte circulation rate of 8L/min.

The raw foil is immersed in an aqueous solution containing chromic anhydride and galactose (chromic anhydride concentration is 0.9 g/L, galactose concentration is 3 g/L) for 30 seconds, then washed with water and air-dried at 80°C, and then placed between an anode and a cathode and a high voltage power supply is applied to perform surface ionization treatment to obtain an ultra-thin electrolytic copper foil; wherein the conditions for the surface ionization treatment are: a power of 3 kW, an instantaneous voltage of 1860 V, and the anode and cathode materials for the surface ionization treatment are both silicone rubber rollers.

A scanning electron microscope (SEM) image (magnified 10,000 times) of the cross section of the ultra-thin electrolytic copper foil prepared in this embodiment is shown in FIG3 . It can be seen from FIG3 that the thickness of the copper foil is 1.268-1.430 μm, which meets the requirements of ultra-thin copper foil.

Example 3

Adding a complexing agent, sodium sulfite, and an auxiliary complexing agent, sodium citrate, into a sodium hydroxide solution (sodium hydroxide concentration is 50 g/L) to obtain a solution A; adding copper sulfate pentahydrate, zinc sulfate heptahydrate, SnSO ₄ , and thiourea into deionized water to obtain a solution B; mixing the above-obtained solution A with the solution B, and adding deionized water to the required volume to obtain a copper-containing electrolyte;

Wherein, in the copper-containing electrolyte, the concentration of sodium hydroxide is 30 g/L, the concentration of sodium sulfite is 80 g/L, the concentration of sodium citrate is 20 g/L, the concentration of Cu ²⁺ is 60 g/L, the concentration of Zn ²⁺ is 13 g/L, the concentration of Sn ²⁺ is 0.4 g/L, and the concentration of thiourea is 0.002 g/L;

Conductive glass is pretreated in a polyphthalocyanine aqueous solution with a volume concentration of 3% (pretreatment time is 10s) and used as a cathode. An iridium-coated titanium plate is used as an anode. A stabilized DC power supply is used to electrolyze the copper-containing electrolyte under stirring to obtain a raw foil. The electrolysis treatment conditions are: current density of 1.5A/ ^dm2 , deposition time of 750s, temperature of 55°C, and electrolyte circulation rate of 9L/min.

The raw foil is immersed in an aqueous solution containing potassium molybdate and nickel sulfate (potassium molybdate concentration is 1.5 g/L, nickel sulfate concentration is 3.5 g/L) for 30 seconds, then washed with water and air-dried at 80°C, and then placed between an anode and a cathode and a high voltage power supply is applied to perform surface ionization treatment to obtain an ultra-thin electrolytic copper foil; wherein the conditions for the surface ionization treatment are: a power of 5 kW, an instantaneous voltage of 3520 V, and the anode and cathode materials for the surface ionization treatment are both silicone rubber rollers.

Example 4

The complexing agent cysteine and the auxiliary complexing agent sodium citrate are added to a sodium hydroxide solution (the sodium hydroxide concentration is 50 g/L) to obtain a solution A; copper sulfate pentahydrate, zinc sulfate heptahydrate, CdSO ₄ , and thiomorpholine-3-carboxylic acid hydrochloride are added to deionized water to obtain a solution B; the above-obtained solution A is mixed with the solution B, and deionized water is added to make up to the required volume to obtain a copper-containing electrolyte;

Wherein, in the copper-containing electrolyte, the concentration of sodium hydroxide is 20 g/L, the concentration of cysteine is 100 g/L, the concentration of sodium citrate is 20 g/L, the concentration of Cu ²⁺ is 40 g/L, the concentration of Zn ²⁺ is 15 g/L, the concentration of Cd ²⁺ is 0.5 g/L, and the concentration of thiomorpholine-3-carboxylic acid hydrochloride is 0.004 g/L;

Conductive glass is pretreated in a polypyrrole aqueous solution with a volume concentration of 2% (pretreatment time is 10s) and used as a cathode. An iridium-coated titanium plate is used as an anode. A stabilized DC power supply is used to electrolyze the copper-containing electrolyte under stirring to obtain a raw foil. The electrolysis treatment conditions are: current density of 2A/ ^dm2 , deposition time of 800s, temperature of 55°C, and electrolyte circulation rate of 10L/min.

The raw foil is immersed in an aqueous solution containing bismuth molybdate and chromium sulfate (bismuth molybdate concentration is 0.9 g/L, chromium sulfate concentration is 3 g/L) for 30 seconds, then washed with water and air-dried at 80°C, and then placed between an anode and a cathode and a high voltage power supply is applied to perform surface ionization treatment to obtain an ultra-thin electrolytic copper foil; wherein the conditions for the surface ionization treatment are: a power of 7 kW, an instantaneous voltage of 4070 V, and the anode and cathode materials for the surface ionization treatment are both silicone rubber rollers.

Example 5

A complexing agent, potassium pyrophosphate, and an auxiliary complexing agent, sodium citrate, are added to a sodium hydroxide solution (the concentration of sodium hydroxide is 50 g/L) to obtain a solution A; copper sulfate pentahydrate, zinc sulfate heptahydrate, Bi ₂ (SO ₄ ) ₃ , and 2-mercaptopropionic acid are added to deionized water to obtain a solution B; the above-obtained solution A is mixed with the solution B, and deionized water is added to make the volume to a required volume to obtain a copper-containing electrolyte;

Wherein, in the copper-containing electrolyte, the concentration of sodium hydroxide is 60 g/L, the concentration of potassium pyrophosphate is 120 g/L, the concentration of sodium citrate is 20 g/L, the concentration of Cu ²⁺ is 45 g/L, the concentration of Zn ²⁺ is 12 g/L, the concentration of Bi ³⁺ is 0.2 g/L, and the concentration of 2-mercaptopropionic acid is 0.05 g/L;

Conductive glass is pretreated in a polypyrrole aqueous solution with a volume concentration of 2% (pretreatment time is 5s) and used as a cathode. An iridium-coated titanium plate is used as an anode. A stabilized DC power supply is used to electrolyze the copper-containing electrolyte under stirring to obtain a raw foil. The electrolysis treatment conditions are: current density of 2A/ ^dm2 , deposition time of 1000s, temperature of 60°C, and electrolyte circulation rate of 15L/min.

The raw foil is immersed in an aqueous solution containing zinc sulfate and fucose (zinc sulfate concentration is 1 g/L, fucose concentration is 3 g/L) for 30 seconds, then washed with water and air-dried at 80°C, and then placed between an anode and a cathode and a high voltage power supply is applied to perform surface ionization treatment to obtain an ultra-thin electrolytic copper foil; wherein the conditions for the surface ionization treatment are: a power of 10 kW, an instantaneous voltage of 4930 V, and the anode and cathode materials for the surface ionization treatment are both silicone rubber rollers.

Comparative Example 1

The preparation is carried out according to the method of Example 1, except that the conductive glass is not pre-treated.

The surface of the ultra-thin copper foil prepared in this comparative example has obvious defects. At the same time, the ultra-thin copper foil is difficult to separate from the cathode. The ultra-thin copper foil is torn and has a poor self-peeling effect, and cannot be provided for back-end applications.

Comparative Example 2

The preparation was carried out according to the method of Example 1, except that the cathode was replaced with a titanium plate and the cathode was pre-treated.

The ultra-thin copper foil and cathode prepared in this comparative example cannot be peeled off and cannot be subsequently processed.

Comparative Example 3

The preparation was carried out according to the method of Example 1, except that the cathode was replaced with a titanium plate and the cathode material was not pre-treated.

The ultra-thin copper foil and cathode prepared in this comparative example cannot be peeled off and cannot be subsequently processed.

Comparative Example 4

The preparation was carried out according to the method of Example 1, except that the surface ionization treatment was not performed.

The surface of the ultra-thin copper foil prepared in this comparative example is complete, dense, and free of cracks, and has a good self-peeling effect. However, it is severely oxidized at 150°C for 10 minutes, and its anti-oxidation ability is relatively poor.

Comparative Example 5

The preparation is carried out according to the method of Example 1, except that the obtained raw foil is not immersed in the aqueous solution containing the antioxidant, but is directly subjected to surface ionization treatment.

The surface of the ultra-thin copper foil prepared in this comparative example is complete, dense, and free of cracks, and has a good self-peeling effect. However, it is severely oxidized at 150° C. for 20 min, and has a poor antioxidant capacity.

Comparative Example 6

The preparation is carried out according to the method of Example 1, except that no subsequent treatment is performed after the raw foil is obtained.

The surface of the ultra-thin copper foil prepared in this comparative example is complete, dense, and free of cracks, and has a good self-peeling effect. However, it is severely oxidized at room temperature and has poor anti-oxidation ability.

Comparative Example 7

The preparation was carried out according to the method of Example 1, except that the current density of the electrolysis treatment was 4 A/dm ² .

According to the conditions used in this comparative example, it is impossible to produce an extremely thin copper foil because the resistance of the conductive glass is greater than that of the titanium plate and the current efficiency is low. When the current density is too large, the mass of copper actually deposited is too small to form a copper foil.

The parameters of the ultra-thin electrolytic copper foils of the above embodiments and comparative examples are listed in Table 1. Among them, the ultra-thin copper foils prepared in comparative examples 2-3 cannot be peeled off from the cathode and cannot be subsequently processed. Comparative example 7 cannot produce copper foil. Therefore, the relevant parameters of comparative examples 2-3 and 7 cannot be measured.

Table 1

Note: *- Average thickness measured by SEM

From the implementation results of the above embodiments and comparative examples and the data in Table 1, it can be seen that the copper foil prepared by the technical solution of the present invention has a self-peeling effect, which solves the tearing problem caused by the difficulty in peeling the copper foil in actual production, and the prepared copper foil is extremely thin, has a large surface tension, high oxidation resistance and good mechanical properties.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims (40)

1. An ultrathin electrolytic copper foil, which is characterized in that the thickness of the copper foil is 0.5-3 mu m, the surface roughness R _z is 0.5-3.5 mu m, the brightness is 180-250GU, the tensile strength is 320-430MPa, the elongation is 1.5-3.2%, and the surface tension is 65-78mM/m or more; the color is not changed when the product is placed for 2 hours at 220 ℃;

The preparation method of the ultrathin electrolytic copper foil comprises the following steps:

(1) Placing a cathode and an anode in a copper-containing electrolyte, and electrifying to perform electrolytic treatment to obtain a green foil;

(2) Placing the raw foil in an aqueous solution containing an antioxidant, washing with water, drying, and performing surface ionization treatment;

wherein, in the step (1), the conductive glass is immersed in an aqueous solution containing a conductive polymer for pretreatment and dried to be used as the cathode;

The preparation method of the copper-containing electrolyte comprises the following steps: adding a complexing agent and an auxiliary complexing agent into alkali liquor to obtain a solution A; adding a copper-containing compound, a zinc-containing compound, an auxiliary metal-containing compound and a brightening agent into water to obtain a solution B, and mixing the solution A and the solution B to obtain the copper-containing electrolyte.

2. A method for preparing an ultrathin electrolytic copper foil, the method comprising:

(1) Placing a cathode and an anode in a copper-containing electrolyte, and electrifying to perform electrolytic treatment to obtain a green foil;

(2) Placing the raw foil in an aqueous solution containing an antioxidant, washing with water, drying, and performing surface ionization treatment;

wherein, in the step (1), the conductive glass is immersed in an aqueous solution containing a conductive polymer for pretreatment and dried to be used as the cathode;

The preparation method of the copper-containing electrolyte comprises the following steps: adding a complexing agent and an auxiliary complexing agent into alkali liquor to obtain a solution A; adding a copper-containing compound, a zinc-containing compound, an auxiliary metal-containing compound and a brightening agent into water to obtain a solution B, and mixing the solution A and the solution B to obtain the copper-containing electrolyte.

3. The method of claim 2, wherein the pretreatment time is 5-10s;

the conductive polymer is at least one selected from polypyrrole, polyaniline and polymalocyanine;

the volume concentration of the aqueous solution of the conductive polymer is 2-4.5%.

4. A process according to claim 2 or 3, wherein the lye is an aqueous solution of a base, the base being sodium hydroxide and/or potassium hydroxide.

5. A method according to claim 2 or 3, wherein the complexing agent is selected from at least one of potassium sodium tartrate, potassium tartrate, sodium tartrate, potassium pyrophosphate, sodium pyrophosphate, glycine, histidine, proline, cysteine, sodium sulfite, potassium sulfite, sodium bisulphite, potassium bisulphite.

6. A method according to claim 2 or 3, wherein the auxiliary complexing agent is selected from at least one of sodium citrate, potassium citrate and disodium citrate.

7. A method according to claim 2 or 3, wherein the copper-containing compound is selected from at least one of a sulphate, chloride and nitrate salt of copper.

8. A method according to claim 2 or 3, wherein the zinc-containing compound is selected from at least one of zinc sulphate, chloride and nitrate.

9. A method according to claim 2 or 3, wherein the promoter metal in the promoter metal-containing compound is selected from at least one of Bi, sn, sb, cd and the promoter metal-containing compound is selected from at least one of a sulfate, chloride and nitrate of the promoter metal.

10. A method according to claim 2 or 3, wherein the brightening agent is selected from at least one of 2-mercaptobenzimidazole, polyethylenimine, thiourea, 2-mercaptopropionic acid, thiomorpholine-3-carboxylate.

11. A method according to claim 2 or 3, wherein the alkaline liquor, complexing agent, auxiliary complexing agent, copper-containing compound, zinc-containing compound, auxiliary metal-containing compound and brightening agent are used in such an amount that the concentration of the alkali in the copper-containing electrolyte is 20-60g/L.

12. The method of claim 11, wherein the lye, complexing agent, auxiliary complexing agent, copper-containing compound, zinc-containing compound, auxiliary metal-containing compound and brightening agent are used in amounts such that the concentration of the base in the copper-containing electrolyte is between 30 and 55g/L.

13. A method according to claim 2 or 3, wherein the complexing agent is at a concentration of 70-150g/L.

14. The method of claim 13, wherein the complexing agent is at a concentration of 80-100g/L.

15. A method according to claim 2 or 3, wherein the concentration of the auxiliary complexing agent is 5-50g/L.

16. The method of claim 15, wherein the concentration of the auxiliary complexing agent is 10-40g/L.

17. A method according to claim 2 or 3, wherein the concentration of the copper-containing compound is 10-60g/L, calculated as elemental copper.

18. A method according to claim 17, wherein the concentration of the copper-containing compound is 30-50g/L, calculated as elemental copper.

19. A process according to claim 2 or 3, wherein the concentration of the zinc-containing compound is from 10 to 25g/L, calculated as elemental zinc.

20. The process according to claim 19, wherein the concentration of the zinc-containing compound is 11-15g/L, calculated as elemental zinc.

21. A process according to claim 2 or 3, wherein the concentration of the promoter metal-containing compound is from 0.01 to 1g/L based on the promoter metal.

22. The process of claim 21, wherein the concentration of the promoter metal-containing compound is from 0.01 to 0.5g/L based on the promoter metal.

23. A method according to claim 2 or 3, wherein the concentration of the brightening agent is 0.001-0.1g/L.

24. The method of claim 23, wherein the concentration of the brightening agent is 0.001-0.05g/L.

25. A method according to claim 2 or 3, wherein the electrolytic treatment uses a regulated dc power supply.

26. A method according to claim 2 or 3, wherein the current density of the electrolytic treatment is 0.5A/dm ²-3.5A/dm².

27. The method of claim 26, wherein the electrolytic treatment has a current density of 0.5A/dm ²-2A/dm².

28. A method according to claim 2 or 3, wherein the time of the electrolytic treatment is 400s-800s.

29. The method of claim 28, wherein the electrolytic treatment is for a time of 500s-700s.

30. A method according to claim 2 or 3, wherein the temperature of the electrolytic treatment is 40-60 ℃.

31. The method of claim 30, wherein the temperature of the electrolytic treatment is 40-55 ℃.

32. A method according to claim 2 or 3, wherein the copper-containing electrolyte is circulated at a rate of 1-10L/min.

33. The method of claim 32, wherein the copper-containing electrolyte is circulated at a rate of 2-8L/min.

34. A method according to claim 2 or 3, wherein in step (2), the antioxidant is selected from two or more of chromic anhydride, glucose, gluconic acid, galactose, fucose, sodium molybdate, potassium molybdate, zinc molybdate, bismuth molybdate, nickel sulfate, zinc sulfate, chromium sulfate.

35. A method according to claim 2 or 3, wherein the concentration of the antioxidant is 0.5-5g/L.

36. The method of claim 35, wherein the concentration of the antioxidant is 0.6-4g/L.

37. A method according to claim 2 or 3, wherein the process of surface ionization treatment comprises: the green foil is placed between an anode and a cathode and a high voltage power supply is applied.

38. A method according to claim 2 or 3, wherein the surface ionisation treatment has a voltage of 1000-5000V and a power of 2-10kW.

39. An extra thin electrolytic copper foil, characterized in that said copper foil is produced by the method according to any one of claims 2 to 38.

40. The use of the copper foil of claim 39 in chip packaging.