Preparation method of preferred orientation copper foil

Abstract

The invention discloses a preparation method of a preferred orientation copper foil, and relates to the technical field of metal material processing. According to the method, the copper raw material is subjected to plastic deformation through an asymmetrical rolling process, high-density dislocation and deformation energy storage are introduced, then a multi-stage annealing process is adopted, temperature gradient and heat preservation time regulation and control are combined, and collaborative optimization of grain recrystallization and preferred orientation is achieved. Through the synergistic effect of rolling deformation and annealing, the copper foil with the grain orientation consistency larger than or equal to 95% and the thickness of 0.1-1 mm can be prepared, and the method has the advantages of being low in defect and high in orientation consistency and is suitable for macro production in the fields of power transmission, electronic packaging, flexible circuits and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, and in particular to a method for preparing preferentially oriented copper foil. Background Art

[0002] As a highly conductive metal, copper plays an irreplaceable role in power transmission, electronic packaging, flexible circuits, and superconducting devices. The regulation of grain orientation is the key to improving its performance. A highly consistent {111} texture can significantly reduce grain boundary resistance, inhibit electromigration, and extend device life. However, the traditional rolling annealing process has significant limitations. Single-stage annealing makes it difficult to balance the recrystallization and grain growth processes, which can easily lead to random orientation. Conventional rolling processes cannot effectively induce the preferential arrangement of specific crystal planes due to uneven strain distribution. For example, although synchronous rolling can refine grains, the shear strain is insufficient and the {111} texture is randomly distributed. Although high-temperature annealing can eliminate residual stress, it may cause abnormal grain growth and destroy orientation consistency. In addition, the existing process has insufficient control accuracy for foil thickness (especially below 1 mm), and the thickness tolerance often exceeds ±10%, making it difficult to meet the stringent requirements of high-density interconnection.

[0003] As power transmission develops towards high efficiency and energy saving, flexible electronic devices develop towards miniaturization and high integration, which puts higher requirements on the orientation consistency, surface quality and mechanical properties of copper foil. In the existing technology, composite processes (such as electrodeposition + laser annealing) are often used to improve orientation, but the electrodeposition method relies on complex additives and precision templates, which is costly and difficult to mass produce. Although laser annealing can locally regulate the texture, it has the problems of wide heat-affected zone and low efficiency. On the other hand, although asynchronous rolling technology can introduce shear strain, its synergistic mechanism with multi-stage annealing has not yet been clarified, resulting in a lack of theoretical guidance for the optimization of process parameters. Therefore, the development of a low-cost, scalable and precisely regulated rolling-annealing synergistic process has become the key to breaking through the bottleneck of high-oriented copper foil preparation. Summary of the Invention

[0004] To address these shortcomings, the present invention provides a method for preparing preferentially oriented copper foil. This method effectively solves the problem of difficult grain orientation by introducing shear strain through asynchronous rolling and synergistically regulating it with multi-stage annealing. This method can produce copper foil with a grain orientation consistency of ≥95% and a thickness of 0.1-1 mm. This method is suitable for high-quality and large-scale production of copper foil with low defects and high orientation consistency. The specific technical solution is as follows:

[0005] A method for preparing a preferentially oriented copper foil comprises the following steps:

[0006] Step 1: Prepare the copper raw material into an initial plate with a thickness of 2 to 10 mm;

[0007] Step 2: Perform multi-pass asynchronous rolling on the sheet metal. The total reduction is 90-95%, the rolling temperature is room temperature, and the reduction per pass is ≤20%, to obtain a rolled foil with a thickness of 0.1-1 mm;

[0008] Step 3: Place the rolled foil in an annealing furnace and perform the first-stage annealing. Heat it to 500-600°C at a rate of 10-20°C / min, hold for 30-60 minutes, and then introduce high-purity argon for protection;

[0009] Step 4: Perform the second-stage annealing. Heat it to 700-800°C at a rate of 5-10°C / min, hold for 1-3 hours, and introduce high-purity argon for protection;

[0010] Step 5: Perform the third-stage annealing. Slowly cool it to 300-400°C at a rate of 1-3°C / min, hold for 1-2 hours, introduce high-purity argon for protection, and then air-cool to room temperature. Finally, obtain a copper foil with a grain size ≥50 μm and a preferred orientation of {111} texture.

[0011] Preferably, in Step 1, the purity of the copper raw material is ≥99.95 wt%.

[0012] Preferably, in Step 1, the copper raw material is made into an initial sheet by powder metallurgy process.

[0013] Preferably, in Step 2, during the asynchronous rolling, the upper and lower roll speed ratio is 1.1-1.5 to enhance the shear strain and promote the {111} crystal plane to be parallel to the rolling plane.

[0014] Preferably, in Step 2, the rolling direction is parallel to the {111} preferred orientation of the initial grains of the sheet metal or forms an angle of 15°-45°.

[0015] Preferably, in Steps 3 to 5, the purity of the high-purity argon is ≥99.999%, and the oxygen content under the protection of the high-purity argon is ≤5 ppm.

[0016] Preferably, in Step 3, after the first-stage annealing, the grain recrystallization rate is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolled state.

[0017] Preferably, in Step 4, the second-stage annealing adopts gradient temperature control, and the axial temperature difference in the furnace is ≤5°C to inhibit abnormal grain growth.

[0018] Preferably, in Step 5, after the third-stage annealing, the surface roughness Ra of the copper foil is ≤0.2 μm, the tensile strength is ≥250 MPa, and the conductivity is ≥98% IACS.

[0019] Preferably, the thickness tolerance of the copper foil is ≤±5%, and the proportion of the grain boundary orientation difference angle ≤10° is ≥90%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. In the present invention, plastic deformation is carried out on copper raw materials through an asynchronous rolling process to introduce high-density dislocations and deformation energy storage. Subsequently, a multi-stage annealing process is adopted, combined with the regulation of temperature gradient and holding time, to realize the synergistic optimization of grain recrystallization and preferred orientation. Through the synergistic effect of rolling deformation and annealing, the pole density of the {111} texture is significantly increased, and the prepared copper foil has a grain orientation consistency of ≥95%, a thickness of 0.1-1 mm, a thickness tolerance of ≤±5%, and a proportion of grain boundary orientation difference angles of ≤10° of ≥90%.

[0022] 2. The asynchronous rolling (roll speed ratio of 1.1-1.5) in the present invention can introduce shear strain, and the strain distribution can be adjusted according to the raw material type to directionally induce the arrangement of specific crystal planes, promoting the {111} crystal plane to be parallel to the rolling plane. In the three-stage annealing of the present invention, the first-stage medium-temperature annealing eliminates residual stress, the second-stage high-temperature annealing drives recrystallization and orientation competition, and the third-stage low-temperature annealing stabilizes the texture and releases micro-stress. The three-stage annealing realizes dislocation annihilation, recrystallization optimization, and grain boundary straightening respectively. It avoids the problem of random orientation in traditional single-stage annealing, overcomes the defects of insufficient shear strain in synchronous rolling and abnormal grain growth in single-stage annealing, and realizes the coordinated control of foil thickness and orientation.

[0023] 3. The method of the present invention has a simple and efficient process, can macroscopically prepare high-orientation copper foil, provides an efficient and economic solution for the material requirements of high-end power transmission equipment and electronic devices, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments.

[0025] Figure 1 It is a flowchart for the preparation of a copper foil with preferred grain orientation in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will describe in detail the specific embodiments of the present invention, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0027] Example 1

[0028] A method for preparing a copper foil with preferred grain orientation jointly regulated by asynchronous rolling and multi-stage annealing is as follows:

[0029] Step 1: Prepare an initial sheet with a thickness of 6 mm from copper raw materials with a purity of ≥99.95 wt% through a powder metallurgy process;

[0030] Step 2: Carry out cold rolling in 6 passes using asynchronous rolling (upper and lower roll speed ratio of 1.3), with a total reduction of 90%. The rolling direction is parallel to the {111} preferred orientation of the initial grains of the sheet. The rolling temperature is room temperature to obtain a foil with a thickness of 0.6 mm, and the reduction per pass is controlled at 15%.

[0031] Step 3: Place the rolled foil in an annealing furnace for the first-stage annealing. Heat it up to 600 °C at a rate of 20 °C / min, hold for 30 minutes, and introduce high-purity argon with a purity ≥99.999% for protection. The oxygen content under high-purity argon protection is ≤5 ppm. After the first-stage annealing, the grain recrystallization rate is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolled state.

[0032] Step 4: Carry out the second-stage annealing. Heat it up to 780 °C at a rate of 8 °C / min, hold for 1.5 hours, and the oxygen content under argon protection is ≤5 ppm. The second-stage annealing uses gradient temperature control, and the axial temperature difference in the furnace is ≤5 °C to inhibit abnormal grain growth.

[0033] Step 5: Carry out the third-stage annealing. Slowly cool it down to 380 °C at a rate of 1.5 °C / min, hold for 2 hours, and finally air-cool to room temperature. The oxygen content under argon protection is ≤5 ppm.

[0034] Finally, a copper foil sample with preferred grain orientation is obtained. The conductivity of the copper foil is 99.5% IACS, and the tensile strength is 282 MPa.

[0035] Example 2

[0036] A preparation method for a copper foil with jointly regulated preferred grain orientation based on asynchronous rolling and multi-stage annealing is as follows:

[0037] Step 1: Prepare an initial sheet with a thickness of 10 mm from copper raw materials with a purity ≥99.95 wt% through powder metallurgy.

[0038] Step 2: Carry out cold rolling in 19 passes using asynchronous rolling (upper and lower roll speed ratio of 1.1), with a total reduction of 95%. The rolling direction is parallel to the {111} preferred orientation of the initial grains of the sheet. The rolling temperature is room temperature to obtain a foil with a thickness of 0.5 mm, and the reduction per pass is controlled at 5%.

[0039] Step 3: Place the rolled foil in an annealing furnace for the first-stage annealing. Heat it up to 520 °C at a rate of 10 °C / min, hold for 60 minutes, and introduce high-purity argon with a purity ≥99.999% for protection. The oxygen content under high-purity argon protection is ≤5 ppm. After the first-stage annealing, the grain recrystallization rate is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolled state.

[0040] Step 4: Conduct the second-stage annealing. Heat up to 720°C at a rate of 5°C / min, hold for 2 hours, and the oxygen content is ≤5 ppm under argon protection; the second-stage annealing uses gradient temperature control, and the axial temperature difference in the furnace is ≤5°C to inhibit abnormal grain growth;

[0041] Step 5: Conduct the third-stage annealing. Slowly cool down to 400°C at a rate of 1°C / min, hold for 2 hours, and finally air-cool to room temperature. The oxygen content is ≤5 ppm under argon protection.

[0042] Finally, a copper foil sample with grain preferred orientation is obtained. The conductivity of the copper foil is 98.5% IACS, and the tensile strength is 290 MPa.

[0043] Example 3

[0044] A preparation method for copper foil with grain preferred orientation jointly regulated by asynchronous rolling and multi-stage annealing is as follows:

[0045] Step 1: Prepare an initial sheet with a thickness of 2 mm from copper raw materials with a purity of ≥99.95 wt% through powder metallurgy.

[0046] Step 2: Adopt asynchronous rolling (the upper and lower roll speed ratio is 1.2), conduct 9 passes of cold rolling, with a total reduction of 90%. The rolling direction forms a 45° angle with the {111} preferred orientation of the initial grains of the sheet. The rolling temperature is room temperature, and a foil with a thickness of 0.2 mm is obtained. The reduction per pass is controlled at 10%.

[0047] Step 3: Place the rolled foil in an annealing furnace for the first-stage annealing. Heat up to 500°C at a rate of 15°C / min, hold for 50 minutes, and introduce high-purity argon with a purity of ≥99.999% for protection. The oxygen content is ≤5 ppm under high-purity argon protection; after the first-stage annealing, the grain recrystallization rate is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolling state.

[0048] Step 4: Conduct the second-stage annealing. Heat up to 700°C at a rate of 10°C / min, hold for 1 hour, and the oxygen content is ≤5 ppm under argon protection; the second-stage annealing uses gradient temperature control, and the axial temperature difference in the furnace is ≤5°C to inhibit abnormal grain growth;

[0049] Step 5: Conduct the third-stage annealing. Slowly cool down to 300°C at a rate of 3°C / min, hold for 2 hours, and finally air-cool to room temperature. The oxygen content is ≤5 ppm under argon protection.

[0050] Finally, a copper foil sample with grain preferred orientation is obtained. The conductivity of the copper foil is 98.6% IACS, and the tensile strength is 293 MPa.

[0051] Example 4

[0052] A preparation method of copper foil with grain preferred orientation regulated by combined asynchronous rolling and multi-stage annealing, the steps are as follows:

[0053] Step 1: Prepare an initial plate with a thickness of 8 mm from copper raw materials with a purity of ≥99.95 wt% through powder metallurgy process;

[0054] Step 2: Adopt asynchronous rolling (the upper and lower roll speed ratio is 1.3), conduct 9 passes of cold rolling with a total reduction of 90%, the rolling direction is parallel to the {111} preferred orientation of the initial grains of the plate, the rolling temperature is room temperature, obtain a foil with a thickness of 0.8 mm, and control the reduction per pass at 10%;

[0055] Step 3: Place the rolled foil in an annealing furnace for the first-stage annealing, heat up to 580 °C at a rate of 15 °C / min, hold for 40 minutes, and introduce high-purity argon with a purity of ≥99.999% for protection, with the oxygen content ≤5 ppm under high-purity argon protection; after the first-stage annealing, the grain recrystallization rate is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolling state;

[0056] Step 4: Conduct the second-stage annealing, heat up to 700 °C at a rate of 5 °C / min, hold for 3 hours, with the oxygen content ≤5 ppm under argon protection; the second-stage annealing adopts gradient temperature control, and the axial temperature difference in the furnace is ≤5 °C to inhibit abnormal grain growth;

[0057] Step 5: Conduct the third-stage annealing, slowly cool down to 350 °C at a rate of 2 °C / min, hold for 1 hour, and finally air-cool to room temperature, with the oxygen content ≤5 ppm under argon protection.

[0058] Finally, obtain a copper foil sample with grain preferred orientation, the conductivity of the copper foil is 100.2% IACS, and the tensile strength is 285 MPa.

[0059] Comparative Example 1

[0060] A preparation method of copper foil based on asynchronous rolling and conventional annealing, the steps are as follows:

[0061] Step 1: Prepare an initial plate with a thickness of 8 mm from copper raw materials with a purity of ≥99.95 wt% through powder metallurgy process;

[0062] Step 2: Adopt asynchronous rolling (the upper and lower roll speed ratio is 1.3), conduct 9 passes of cold rolling with a total reduction of 90%, the rolling direction is parallel to the {111} preferred orientation of the initial grains of the plate, the rolling temperature is room temperature, obtain a foil with a thickness of 0.8 mm, and control the reduction per pass at 10%;

[0063] Step 3: Place the rolled foil in an annealing furnace for single-stage annealing, heat up to 700 °C at a rate of 15 °C / min, hold for 3 hours and then air-cool, with the oxygen content ≤5 ppm under high-purity argon protection.

[0064] The conductivity of the obtained copper foil is 97.2% IACS, and the tensile strength is 265 MPa.

[0065] Comparative Example 2

[0066] A method for preparing a copper foil based on synchronous rolling and multi-stage annealing, the steps are as follows:

[0067] Step 1: Prepare an initial sheet with a thickness of 8 mm from a copper raw material with a purity of ≥99.95 wt% through powder metallurgy.

[0068] Step 2: Adopt synchronous rolling (roll speed ratio 1.0), perform 9 passes of cold rolling with a total reduction of 90%, the rolling direction is parallel to the {111} preferred orientation of the initial grains of the sheet, the rolling temperature is room temperature, and obtain a foil with a thickness of 0.8 mm. The reduction per pass is controlled at 10%.

[0069] Step 3: Place the rolled foil in an annealing furnace for the first-stage annealing. Heat it to 580 °C at a rate of 15 °C / min, hold for 40 minutes, and introduce high-purity argon with a purity of ≥99.999% for protection. The oxygen content under high-purity argon protection is ≤5 ppm. After the first-stage annealing, the recrystallization rate of the grains is ≥80%, and the dislocation density is reduced to less than 10% of the initial rolled state.

[0070] Step 4: Perform the second-stage annealing. Heat it to 700 °C at a rate of 5 °C / min, hold for 3 hours, and the oxygen content under argon protection is ≤5 ppm. The second-stage annealing adopts gradient temperature control, and the axial temperature difference in the furnace is ≤5 °C to inhibit abnormal grain growth.

[0071] Step 5: Perform the third-stage annealing. Slowly cool it to 350 °C at a rate of 2 °C / min, hold for 1 hour, and finally air-cool to room temperature. The oxygen content under argon protection is ≤5 ppm.

[0072] The conductivity of the obtained copper foil is 96.8% IACS, and the tensile strength is 255 MPa.

[0073] The foregoing description of the specific exemplary embodiments of the present invention is for the purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and changes. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a preferred orientation copper foil, characterized in that, It includes the following steps: Step 1: Make the copper raw material into an initial sheet with a thickness of 2 - 10 mm; Step 2: Conduct multi-pass asynchronous rolling on the sheet, with a total reduction of 90 - 95%, a rolling temperature of room temperature, and a single-pass reduction ≤ 20%, to obtain a rolled foil with a thickness of 0.1 - 1 mm; Step 3: Anneal the rolled foil in the first stage, heat it to 500 - 600 °C at a rate of 10 - 20 °C / min, hold for 30 - 60 minutes, and then introduce high-purity argon for protection; Step 4: Conduct the second-stage annealing, heat it to 700 - 800 °C at a rate of 5 - 10 °C / min, hold for 1 - 3 hours, and introduce high-purity argon for protection; Step 5: Conduct the third-stage annealing, slowly cool it to 300 - 400 °C at a rate of 1 - 3 °C / min, hold for 1 - 2 hours, introduce high-purity argon for protection, and then air-cool to room temperature to finally obtain a copper foil with a grain size ≥ 50 μm and a preferred orientation of {111} texture.

2. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that In Step 1, the purity of the copper raw material ≥ 99.95 wt%.

3. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that, In Step 1, the copper raw material is made into the initial sheet by powder metallurgy process.

4. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that, In Step 2, during the asynchronous rolling, the upper and lower roll speed ratio is 1.1 - 1.

5.

5. The preparation method of a preferred orientation copper foil according to claim 1, wherein [[ID= 6. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that, ​ 7. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that, ​ 8. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that ​ 9. The preparation method of a preferred orientation copper foil according to claim 1, characterized in that, ​ 10. The preparation method of a preferred orientation copper foil according to claim 1, wherein, ​

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