Ultrafine-grained high-performance copper material and method for producing the same

Abstract

The application provides a kind of ultrafine-grain high-performance copper material and a preparation method thereof, comprising the following steps: high-energy ball milling of copper powder and boron powder to obtain ultrafine-grain mixed powder; cold forming of the ultrafine-grain mixed powder to obtain a preform; preheating and rolling of the preform to obtain a copper material. The application synchronously completes the rapid sintering of ultrafine copper powder and the deformation process of metal fluid under pressure through powder rolling technology, achieving powder sintering and sintered body rolling deformation in one step to obtain a copper material with high density and high mechanical properties. In comparison, conventional powder rolling products must undergo a separate long-time sintering process before subsequent rolling.

Description

Technical Field

[0001] This invention belongs to the field of copper material technology, and particularly relates to an ultrafine-grained high-performance copper material and its preparation method. Background Technology

[0002] With the rapid development of electronic information technology and the semiconductor industry, integrated circuits are constantly evolving towards large-scale, high-integration, and miniaturization. As a key structural component in integrated circuit packaging, the lead frame plays a crucial role in connecting internal chips with external circuits, and its performance directly affects packaging reliability and signal transmission efficiency.

[0003] Currently, copper alloys are the primary material for integrated circuit leadframes, accounting for over 80% of all materials used. To adapt to the trends of thinner, higher-density, and higher-power packaging, the industry has placed higher demands on leadframe materials. These materials must not only possess excellent mechanical properties (e.g., tensile strength exceeding 600 MPa) but also maintain excellent electrical conductivity (conductivity not less than 80% IACS). However, there is an inherent constraint between the strength and conductivity of copper alloys: generally, when strengthening by adding alloying elements (such as P, Ni, Si, Cr, Zr, etc.), scattering centers are introduced into the matrix, leading to a decrease in conductivity; conversely, while high-purity copper has good conductivity, its strength is low, making it difficult to meet structural requirements.

[0004] Currently, the widely studied Cu-Fe-P, Cu-Ni-Si, and Cu-Cr-Zr alloy series, while capable of synergistically improving strength and conductivity to some extent through microalloying and heat treatment, still struggle to achieve an ideal balance between high strength (>600 MPa) and high conductivity (>80% IACS). Furthermore, existing processes typically begin rolling from ingots or sintered bodies, resulting in complex processes and high costs, making them unsuitable for the electronics industry's demands for high-efficiency, short-process manufacturing.

[0005] Therefore, how to further improve the mechanical properties of copper alloys while ensuring high electrical conductivity, develop copper-based leadframe materials with ultrafine grain structure and high strength and high conductivity, and seek efficient and short-process fabrication technology to match them have become key technical problems that urgently need to be solved in this field, which are of great significance to promoting the progress of high-end semiconductor packaging materials and technologies. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an ultrafine-grained high-performance copper material and its preparation method. The method is simple and the ultrafine-grained high-performance copper material obtained is not only high in strength but also has excellent electrical conductivity.

[0007] This invention provides a method for preparing ultrafine-grained high-performance copper materials, comprising the following steps:

[0008] Copper powder and boron powder were ball-milled at high energy to obtain an ultrafine crystalline mixed powder;

[0009] The ultrafine crystalline mixed powder is cold-formed to obtain a preform;

[0010] The preform is preheated and then rolled to obtain copper material.

[0011] Preferably, the ultrafine crystalline mixed powder comprises 99.9~99.5 wt% Cu and 0.1~0.5 wt% B.

[0012] Preferably, the copper powder is selected from electrolytic copper powder and / or atomized copper powder.

[0013] Preferably, the high-energy ball milling time is 2 to 6 hours.

[0014] Preferably, the ball-to-material ratio used in the high-energy ball mill is (7~11):1.

[0015] Preferably, the average grain size of the ultrafine crystalline mixed powder is 180~500nm.

[0016] Preferably, the cold forming pressure is 130~160MPa, and the cold forming time is 5~30s.

[0017] Preferably, the preform is wrapped with pyrophyllite and then preheated to 550~680℃, and the holding time is 1~5min.

[0018] Preferably, the rolling process includes:

[0019] Hot rolling followed by cold rolling;

[0020] The total deformation of the hot rolling is 15% to 65%;

[0021] The total deformation of the cold rolling is 60-80%, and the deformation per pass is 18-20%; no intermediate annealing is required during the cold rolling deformation process.

[0022] This invention provides an ultrafine-grained high-performance copper material prepared by the preparation method described in the above technical solution.

[0023] This invention provides a method for preparing ultrafine-grained high-performance copper materials, comprising the following steps: high-energy ball milling of copper powder and boron powder to obtain ultrafine-grained mixed powder; cold forming of the ultrafine-grained mixed powder to obtain a preform; and preheating and rolling of the preform to obtain copper material. This invention utilizes powder rolling technology to simultaneously complete the rapid sintering of ultrafine copper powder and the deformation process of the metal fluid under pressure, achieving powder sintering and sintered body rolling deformation in one step, resulting in copper materials with high density and high mechanical properties. In contrast, conventional powder-rolled products require a separate, lengthy sintering process before subsequent rolling. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for the existing technology of rolling powder after sintering;

[0025] Figure 2 A process flow diagram of the ultrafine-grained high-performance copper material provided by the present invention;

[0026] Figure 3 TEM, EBSD, and HRTEM images of the rolled product prepared in Example 3 of this invention. Detailed Implementation

[0027] This invention provides a method for preparing ultrafine-grained high-performance copper materials, comprising the following steps:

[0028] Copper powder and boron powder were ball-milled at high energy to obtain an ultrafine crystalline mixed powder;

[0029] The ultrafine crystalline mixed powder is cold-formed to obtain a preform;

[0030] The preform is preheated and then rolled to obtain copper material.

[0031] This invention involves high-energy ball milling of copper powder and boron powder to obtain an ultrafine crystalline mixed powder.

[0032] This invention employs a method combining mechanical powder preparation and powder rolling to prepare high-performance copper materials. First, ultrafine copper powder with a clean surface and high activity is prepared; then, rapid sintering and rolling deformation of the ultrafine copper powder are achieved through powder rolling technology.

[0033] Specifically, this invention employs high-energy ball milling technology. By adjusting the ball milling process parameters and selectively adding process control agents, ultrafine, clean-surfaced, and highly active copper powder is obtained. High-energy ball milling utilizes the rotation or vibration of a ball mill to subject the raw materials to intense impact, grinding, and stirring by hard balls, thereby pulverizing the powder into nanoscale particles.

[0034] This invention involves high-energy ball milling of copper powder and boron powder to obtain an ultrafine crystalline mixed powder. In this invention, the copper powder is selected from electrolytic copper powder and / or atomized copper powder.

[0035] This invention involves high-energy ball milling of raw materials. The milling is performed in a grinding jar. The milling speed is 400-800 rpm, specifically 400 rpm, 500 rpm, 600 rpm, 700 rpm, or 800 rpm; preferably 400-700 rpm, more preferably 600 rpm. The ball-to-material ratio in the high-energy ball milling is (7-11):1, specifically 7:1, 8:1, 9:1, 10:1, or 11:1. The high-energy ball milling time is 2-5 hours, specifically 2 hours, 3 hours, 4 hours, or 5 hours.

[0036] In this invention, anhydrous ethanol is preferably added as a process control agent during high-energy ball milling. Based on the total mass of copper powder and boron powder, the amount of the process control agent added is 0.06 wt.% to 0.41 wt.%, specifically 0.06 wt.%, 0.07 wt.%, 0.08 wt.%, 0.09 wt.%, 0.10 wt.%, 0.12 wt.%, 0.14 wt.%, 0.16 wt.%, 0.18 wt.%, 0.2 wt.%, 0.22 wt.%, 0.24 wt.%, 0.26 wt.%, 0.28 wt.%, 0.3 wt.%, 0.32 wt.%, 0.34 wt.%, 0.36 wt.%, 0.38 wt.%, 0.40 wt.%, or 0.41 wt.%; more preferably 0.18 wt.% to 0.30 wt.%, and most preferably 0.24 wt.%. The gaseous molecules of the process control agent are coated onto the surface of the ultrafine, highly active powder during the process, which plays a role in blocking oxygen and protecting surface activity. The process control agent can temporarily protect the high activity and cleanliness of the surface of the ultrafine copper powder, thereby solving the technical problems of preparing, storing and transporting such copper powder in an air environment, and providing the necessary conditions for subsequent rapid sintering and rolling deformation.

[0037] The ultrafine crystalline mixed powder comprises 99.9-99.5 wt% Cu and 0.1-0.5 wt% B. In specific embodiments, the ultrafine crystalline mixed powder comprises 99.9 wt% electrolytic copper powder and 0.1 wt% B; or 99.7 wt% electrolytic copper powder and 0.3 wt% B; or 49.8 wt% electrolytic copper powder, 49.8 wt% atomized copper powder and 0.4 wt% boron powder; or 99.5 wt% atomized copper powder and 0.5 wt% boron powder; or 99.8 wt% atomized copper powder and 0.2 wt% boron powder.

[0038] The average grain size of the ultrafine crystalline mixed powder described in this invention is 180~500 nm, specifically 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, or 500 nm; preferably 200~500 nm, more preferably 300~500 nm.

[0039] After obtaining the ultrafine crystalline mixed powder, the present invention cold-forms the ultrafine crystalline mixed powder to obtain a preform. The cold-forming pressure is 130~160MPa, specifically 130MPa, 135MPa, 140MPa, 145MPa, 150MPa, 155MPa or 160MPa; the cold-forming time is 5~30s, specifically 5s, 10s, 15s, 20s, 25s or 30s.

[0040] After obtaining the preform, the present invention preheats the preform and then rolls it to obtain copper material. Preferably, the preform is preheated after being wrapped with pyrophyllite, with pyrophyllite serving as an auxiliary medium; specifically, the preform is wrapped with pyrophyllite. Pyrophyllite is a solid pressure-transmitting medium commonly used in high-pressure physics, possessing the characteristics of high temperature resistance and uniform pressure transmission. During rolling, the pyrophyllite surrounding the preform simultaneously provides sealing and support, and can synergistically undergo plastic deformation under pressure, thereby effectively ensuring uniform stress and stable forming of the preform during high-temperature rolling. The present invention preferably preheats to 550~680℃, specifically 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, or 680℃. After reaching the preheating temperature, the holding time is 1 to 5 minutes, specifically 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0041] The rolling process in this invention includes: hot rolling followed by cold rolling.

[0042] In this invention, the total deformation of the hot rolling is 15-65%; preferably 50-60%, more preferably 50%.

[0043] In this invention, the total deformation of the cold rolling is 60-80%, preferably 70-80%; the deformation per rolling pass is 18-20%; no intermediate annealing is required during the cold rolling deformation process; and the number of cold rolling deformation passes is 3-5.

[0044] This invention replaces the multi-step process in existing powder rolling processes with a one-step "rolling and sintering" process under pressure, such as... Figure 2As shown, compared with the prior art, this invention utilizes a high-energy dry ball milling process. Under the collision action of high-energy grinding media, the powder components undergo repeated cold welding and fracture, forming refined nanocrystals. The gaseous molecules of the added process control agent are coated onto the surface of the ultrafine, highly active powder during this process, playing a role in blocking oxygen and protecting surface activity. The powder is then pressed and shaped using cold pressing to obtain a uniform blank with a density of about 70%. The blank is then preheated to release the gas coated on the particle surface, re-exposing the ultrafine, highly active surface. Finally, the powder particles with highly active surfaces in the blank are rapidly sintered through a rapid sintering and hot rolling process under pressure, achieving effective bonding between particles. A reasonable cold rolling deformation process is then used to eliminate defects and pores in the rolled material, further improving the density of the copper material. The resulting copper alloy rolled product has a fine and uniform microstructure, thereby improving the mechanical properties of the copper material.

[0045] This invention provides an ultrafine-grained high-performance copper material prepared by the preparation method described in the above technical solution.

[0046] To further illustrate the present invention, the following detailed description of an ultrafine-grained high-performance copper material and its preparation method provided by the present invention is provided in conjunction with embodiments, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] 20 g of mixed powder was placed in a ball mill jar, wherein the electrolytic copper powder accounted for 99.9 wt% and the boron powder accounted for 0.1 wt%, the ball-to-powder ratio was 10:1, 0.06 wt% anhydrous ethanol was added as a process control agent, the vibration frequency was 400 r / min, and after mechanical ball milling for 2 hours, a highly active powder was obtained, the average grain size of which was 500 nanometers.

[0049] The highly active powder was cold-pressed under a pressure of 130 MPa for 5 s to obtain a preform;

[0050] After wrapping the blank with pyrophyllite, preheat it to 550°C for 1 minute.

[0051] After the sample is taken out, it is powder rolled, and a large reduction is used for one-time rolling deformation. The rolling deformation is 15%. After hot rolling, it is air-cooled to room temperature.

[0052] The cold-rolled billet is subjected to cold rolling deformation, with a total cold rolling deformation of 60%; the rolled product is obtained.

[0053] The product prepared in Example 1 was subjected to performance testing, and the test results are shown in Table 1.

[0054] Example 2

[0055] 20 g of mixed powder was placed in a ball mill jar, wherein the electrolytic copper powder accounted for 99.7 wt% and the boron powder accounted for 0.3 wt%, the ball-to-powder ratio was 7:1, 0.18 wt% anhydrous ethanol was added as a process control agent, the vibration frequency was 500 r / min, and after mechanical ball milling for 3 hours, a highly active powder was obtained, the average grain size of which was 400 nanometers.

[0056] The highly active powder was cold-pressed under a pressure of 130 MPa for 10 s to obtain a preform;

[0057] After wrapping the blank with pyrophyllite, preheat it to 550°C for 2 minutes.

[0058] After the sample is taken out, it is powder rolled, and a large reduction is used for one-time rolling deformation. The rolling deformation is 40%. After hot rolling, it is air-cooled to room temperature.

[0059] The cold-rolled billet is subjected to cold rolling deformation, with a total cold rolling deformation of 60%; the rolled product is obtained.

[0060] The product prepared in Example 2 was subjected to performance testing, and the test results are shown in Table 1.

[0061] Example 3

[0062] 20 g of mixed powder was placed in a ball mill jar, wherein the electrolytic copper powder accounted for 49.8 wt%, the atomized copper powder accounted for 49.8 wt%, and the boron powder accounted for 0.4 wt%, the ball-to-powder ratio was 8:1, and 0.24 wt% anhydrous ethanol was added as a process control agent. The vibration frequency was 600 r / min, and after mechanical ball milling for 4 hours, a highly active powder was obtained with an average grain size of 300 nanometers.

[0063] The highly active powder was cold-pressed under a pressure of 140 MPa for 20 s to obtain a preform;

[0064] After wrapping the blank with pyrophyllite, preheat it to 600℃ for 3 minutes.

[0065] After the sample is taken out, it is powder rolled, and a large reduction is used for one-time rolling deformation. The rolling deformation is 50%. After hot rolling, it is air-cooled to room temperature.

[0066] The cold-rolled billet is subjected to cold rolling deformation, with a total cold rolling deformation of 70%; the rolled product is obtained.

[0067] The product prepared in Example 3 of this invention was sampled, polished, and tested. Tensile testing was performed according to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Tests at room temperature," and electrical conductivity testing was performed according to GB / T 32791-2016 "Edge current test method for conductivity of copper and copper alloys." The properties of the rolled samples obtained are shown in Table 1. Microstructural analysis revealed that the copper alloy rolled product prepared in Example 3 possesses a nanoscale microstructure. Figure 3 In the image, 'a' is a TEM image of a copper alloy rolled part. Figure 3 Figure b shows the EBSD image of the copper alloy rolled part, which indicates that the rolled part has a nanoscale microstructure. Figure 3 In the image c, which is the HRTEM image of the copper alloy rolled part, it can be seen that the rolled part has a stacked fault structure.

[0068] Example 4

[0069] 20 g of mixed powder was placed in a ball mill jar, wherein the atomized copper powder accounted for 99.5 wt% and the boron powder accounted for 0.5 wt%, the ball-to-powder ratio was 9:1, 0.3 wt% anhydrous ethanol was added as a process control agent, the vibration frequency was 700 r / min, and after mechanical ball milling for 5 hours, a highly active powder was obtained, the average grain size of which was 200 nanometers.

[0070] The highly active powder was cold-pressed under a pressure of 150 MPa for 30 s to obtain a preform;

[0071] After wrapping the blank with pyrophyllite, preheat it to 650°C for 4 minutes.

[0072] After the sample is taken out, it is powder rolled, and a large reduction is used for one-time rolling deformation. The rolling deformation is 60%. After hot rolling, it is air-cooled to room temperature.

[0073] The cold-rolled billet is subjected to cold rolling deformation, with a total cold rolling deformation of 80%; the rolled product is obtained.

[0074] The product prepared in Example 4 was subjected to performance testing, and the test results are shown in Table 1.

[0075] Example 5

[0076] 20 g of mixed powder was placed in a ball mill jar, wherein the atomized copper powder accounted for 99.8 wt% and the boron powder accounted for 0.2 wt%, the ball-to-powder ratio was 11:1, 0.41 wt% anhydrous ethanol was added as a process control agent, the vibration frequency was 800 r / min, and after mechanical ball milling for 6 hours, a highly active powder was obtained, the average grain size of which was 180 nanometers.

[0077] The highly active powder was cold-pressed under a pressure of 160 MPa for 30 s to obtain a preform;

[0078] After wrapping the blank with pyrophyllite, preheat it to 680℃ for 5 minutes.

[0079] After the sample is taken out, it is powder rolled, and a large reduction is used for one-time rolling deformation. The rolling deformation is 65%. After hot rolling, it is air-cooled to room temperature.

[0080] The cold-rolled billet is subjected to cold rolling deformation, with a total cold rolling deformation of 80%; the rolled product is obtained.

[0081] The product prepared in Example 5 was subjected to performance testing, and the test results are shown in Table 1.

[0082] Table 1

[0083]

[0084] The preparation method provided by this invention can achieve rapid sintering and rolling deformation simultaneously under pressure, without the need for separate powder metallurgy sintering processes, separate rolling processes, and subsequent heat treatment processes such as solution treatment and aging, thus achieving the high mechanical properties of the rolled parts. Moreover, the entire preparation process of this invention can be carried out in an air atmosphere. It also has the advantages of simple process, convenient operation, and few steps, making it suitable for the industrial production of large-scale copper alloy rolled parts.

[0085] This invention utilizes a simple technique to simultaneously complete copper alloy powder metallurgy sintering and rolling under pressure, resulting in copper alloy rolled products with ultra-fine microstructure and high mechanical properties. The invention employs high-energy ball milling technology to prepare nano-copper alloy powder; and through in-situ activation sintering and rolling technology, it obtains highly dense copper alloy rolled products, significantly improving their strength.

[0086] As can be seen from the above embodiments, the key to this invention lies in the preparation method of copper alloy rolled parts. Through powder rolling sintering technology, the rapid sintering of ultrafine copper alloy powder under pressure, along with fluid deformation, flow, and molding processes, are achieved simultaneously. This simultaneously realizes powder sintering and sintered body rolling deformation, ultimately obtaining copper alloy rolled parts with high density and high mechanical properties, such as Cu-B rolled parts with ultrafine structures. Experimental results show that the tensile strength of the copper material is 580~638MPa, the yield strength is 478~580MPa, the elongation is 6.5~8.1%, and the electrical conductivity is 88~92% IACS.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine-grained high-performance copper material, comprising the following steps: Copper powder and boron powder were ball-milled at high energy to obtain an ultrafine crystalline mixed powder; The ultrafine crystalline mixed powder is cold-formed to obtain a preform; The preform is preheated and then rolled to obtain copper material.

2. The preparation method according to claim 1, characterized in that, The ultrafine crystalline mixed powder comprises 99.9~99.5 wt% Cu and 0.1~0.5 wt% B.

3. The preparation method according to claim 1, characterized in that, The copper powder is selected from electrolytic copper powder and / or atomized copper powder.

4. The preparation method according to claim 1, characterized in that, The high-energy ball milling time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that, Anhydrous ethanol is used as a process control agent in the high-energy ball milling process. Based on the total mass of copper powder and boron powder, the amount of anhydrous ethanol added is 0.06~0.41wt%.

6. The preparation method according to claim 1, characterized in that, The average grain size of the ultrafine crystalline mixed powder is 180~500nm.

7. The preparation method according to claim 1, characterized in that, The cold forming pressure is 130~160MPa, and the cold forming time is 5~30s.

8. The preparation method according to claim 1, characterized in that, The preform is wrapped with pyrophyllite and preheated to 550~680℃, and held for 1~5 minutes.

9. The preparation method according to claim 1, characterized in that, The rolling process includes: Hot rolling followed by cold rolling; The total deformation of the hot rolling is 15-65%; The total deformation of the cold rolling is 60-80%, and the deformation per pass is 18-20%; no intermediate annealing is required during the cold rolling deformation process; the cold rolling deformation passes are 3-5 times.

10. An ultrafine-grained high-performance copper material prepared by the preparation method according to any one of claims 1 to 9.

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