A copper alloy with excellent high-temperature resistance and softening performance, a preparation method and application thereof

Abstract

This invention discloses a high heat-resistant and high electrical conductivity copper alloy, its preparation method, and its applications. The copper alloy comprises 0.001wt%–0.01wt% Ag; 0.0005wt%–0.002wt% P; 0.003wt%–0.008wt% X1, with the balance being Cu and impurities, wherein X1 is Sn and Zr; the mass ratio of Sn, Ag, and Zr [Sn] / [Ag+Zr] is 0.5–2. The preparation process of this high heat-resistant and high electrical conductivity copper alloy includes: smelting → casting → continuous extrusion → solution treatment → drawing → low-temperature annealing → length setting → packaging; wherein, the alloy is batched and smelted according to the mass percentage of each element; the low-temperature annealing process is carried out at a temperature of 150℃–350℃ for a holding time of 2–10 hours.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and in particular to a copper alloy with excellent high-temperature softening resistance, its preparation method, and its application. Background Technology

[0002] With the increasing trend towards higher current in electronic and electrical equipment, pure copper materials such as oxygen-free copper, known for their excellent conductivity, are often chosen for electronic and electrical equipment components to reduce current density and effectively dissipate Joule heat. However, pure copper has a drawback in heat resistance; its hardness decreases significantly at high temperatures. Taking the assembly of high-current IGBT power modules as an example, it requires three high-temperature treatments, with the highest temperature reaching 310℃ and each lasting up to 5 minutes. During this continuous and prolonged high-temperature operation, the thermal stability of the copper alloy used in the IGBT heat sink substrate plays a decisive role. Even a single instance of copper material failing in heat resistance will cause the substrate to soften, directly affecting the assembly quality of the IGBT power module.

[0003] Therefore, the industry clearly stipulates that copper materials used in IGBT heat sink substrates must be kept at 350℃ for 10 minutes continuously, and after repeating this process three times, their hardness must still maintain more than 90% of the original hardness of the copper alloy. Furthermore, with the advancement of high-current electronic and electrical equipment and the increasing efficiency of packaging technology, the performance requirements for copper materials used in IGBT heat sink substrates in terms of heat resistance, electrical conductivity, and thermal conductivity are becoming increasingly stringent, especially regarding thermal stability—that is, they must not experience fatigue under repeated high-temperature operating conditions. If tough copper or oxygen-free copper is used, it is difficult to meet the heat resistance requirements of repeated high-temperature soldering during power module assembly, which can easily cause the heat sink substrate to soften, deform, and warp, failing to guarantee surface flatness and ultimately preventing the power module from being assembled. While using copper-tin or copper-iron alloys can improve heat resistance and thermal stability, it significantly weakens electrical conductivity and thermal conductivity, and in severe cases, may even cause the IGBT chip to fail due to excessively high temperatures caused by poor heat dissipation.

[0004] Patent document CN115917023A discloses a copper alloy suitable for components in electronic and electrical equipment such as terminals and heat dissipation parts. This copper alloy contains more than 10 ppm by mass and less than 100 ppm by mass of Mg, with the remainder being Cu and unavoidable impurities. Among the unavoidable impurities, the amounts of S, P, Se, Te, Sb, Bi, and As are less than 10 ppm by mass and less than 5 ppm by mass, respectively. The total amount of P, Se, Te, Sb, Bi and As is less than 30 ppm by mass, the mass ratio of [Mg] / [S+P+Se+Te+Sb+Bi+As] is 0.6 to 50, the conductivity is 97% IACS or higher, the semi-softening temperature is 200°C or higher, the residual stress rate RSG under the condition of 180°C and 30 hours in the direction parallel to the rolling direction is 20% or higher, and the ratio of residual stress rate RSG to residual stress rate RSB under the condition of 180°C and 30 hours in the direction orthogonal to the rolling direction, RSG / RSB, exceeds 1.0. Copper alloy ductile materials, electronic and electrical equipment components, terminals, and heat dissipation substrates made of this copper alloy have a conductivity of 97% IACS or higher, a semi-softening temperature of 200°C or higher, a residual stress rate (RSG) of 20% or higher under 180°C and 30-hour conditions in the direction parallel to the rolling direction, and a ratio (RSG / RSB) of RSG in the direction parallel to the rolling direction and RSB in the direction orthogonal to the rolling direction exceeding 1.0. It can also achieve a balance between high conductivity and excellent heat resistance and stress relaxation resistance.

[0005] However, in order to further meet the requirement of fully suppressing heat generation when a large current is flowing, the heat resistance temperature needs to be increased to 350℃, and there is still room for improvement in maintaining the original hardness level of the copper alloy.

[0006] Therefore, there is an urgent need for a copper alloy with excellent high-temperature softening resistance. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a high heat-resistant and high electrical conductivity copper alloy and its applications.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The components of the copper alloy include: Ag 0.001wt%~0.01wt%; P 0.0005wt%~0.002wt%; X1 0.003wt%~0.008wt%, with the balance being Cu and impurities; X1 is Sn and Zr; the mass ratio of Sn, Ag and Zr added [Sn] / [Ag+Zr] is 0.5~2.

[0010] This invention provides a suitable ratio of Sn, Ag, and Zr to achieve better heat resistance and thermal stability, enabling improved heat resistance under continuous high-temperature conditions and mitigating thermal fatigue failure of the alloy. Under these conditions, a Zr4Sn, Cu3Zr, and Cu5Zr phase composition with better size and more suitable area ratio can be obtained. Zr4Sn effectively pins grain boundaries, hindering Sn grain boundary enrichment and reducing the formation of brittle phases (such as Cu3Sn), while exhibiting good high-temperature stability, but significantly impacting the alloy's conductivity. The Cu3Zr phase provides strong precipitation strengthening, improving the tensile strength and heat resistance of the copper alloy, while having a relatively small impact on the alloy's conductivity. The Cu5Zr phase possesses superior high-temperature stability, but as a typical intermetallic compound, it significantly affects the alloy's conductivity, and the coarse Cu5Zr phase is prone to forming crack initiation sites, hindering plastic processing. To obtain a more comprehensive and superior performance, it is necessary to control the optimal size and most suitable area ratio of the Zr4Sn, Cu3Zr, and Cu5Zr phase composition.

[0011] The copper alloy provided by this invention exhibits synergistic effects with Zr, Sn, and Ag. Appropriate amounts of Zr and Sn form nanoscale Zr-Sn precipitates, Zr4Sn. These Zr4Sn precipitates significantly improve the alloy's heat resistance by pinning grain boundaries and hindering dislocation movement. Conversely, an appropriate amount of Zr can reduce Sn enrichment at grain boundaries, preventing the formation of brittle tin-containing phases such as Cu2Sn, Cu3Sn, and Cu6Sn5. An appropriate amount of Ag promotes uniform precipitation of Zr and Sn, prevents the formation of coarse Cu5Zr phases, and inhibits Sn grain boundary segregation, thereby enhancing precipitation strengthening and achieving both high conductivity and increased strength.

[0012] When the mass ratio of Sn, Ag, and Zr added [Sn] / [Ag+Zr] is less than 0.5, not only is the solid solution strengthening effect of Sn affected, but the amount of Zr4Sn precipitates is also affected, thus affecting the heat resistance and thermal stability of the alloy. When the mass ratio of Sn, Ag, and Zr added [Sn] / [Ag+Zr] is greater than 2, the uniform precipitation effect of Zr and Sn is not good, and coarse Cu5Zr phase and Sn grain boundary segregation are easily formed. This is not only detrimental to the high conductivity of the alloy, making it difficult to achieve 100% IACS conductivity, but also the coarse Cu5Zr phase and Sn grain boundary segregation also bring the risk of processing cracking.

[0013] This invention involves adding an appropriate amount of Ag to form a solid solution in pure copper, significantly improving the strength and softening resistance of pure copper and reducing the impact of temperature on the material. Simultaneously, the difference in atomic radius between Ag and Cu atoms is only small, resulting in a smaller stress field and less scattering of electron waves; therefore, the solid solution of Ag atoms has a minimal impact on conductivity. Thus, the addition of Ag is beneficial to improving the strength and heat resistance of pure copper. When the Ag content is below 0.001 wt%, the solid solution strengthening effect of Ag is not significant, failing to fully exert its effect and showing little improvement in material strength, heat resistance, and thermal stability. On the other hand, when the Ag content exceeds 0.01 wt%, the lattice distortion caused by Ag can actually reduce the conductivity of the alloy. Furthermore, Ag is a precious metal, and its addition is costly. Therefore, this invention controls the Ag content to be between 0.001 wt% and 0.01 wt%.

[0014] In this invention, phosphorus (P) can fully exert its degassing and deoxidizing effects. If the deoxidation effect is poor, it can lead to the oxidation of Sn during the casting process, resulting in some Sn existing in oxide form. This negatively impacts the heat resistance of the tin-containing copper alloy. Furthermore, the Cu3P and tin-phosphorus intermetallic compounds formed by P with Cu and Sn can improve the alloy's high-temperature softening resistance and thermal stability. It is worth noting that while the addition of P can improve the alloy's performance, it also significantly reduces electrical and thermal conductivity. When the P content is below 0.0005 wt%, its effects may not be fully realized. On the other hand, when the P content exceeds 0.002 wt%, not only does the lattice distortion caused by P reduce the alloy's conductivity, but it also promotes the anti-segregation process. The segregated structure forms a network between dendrites, which is detrimental to the alloy's processing performance. Therefore, this invention controls the addition of P content between 0.0005 wt% and 0.002 wt%.

[0015] In this invention, the addition of an appropriate amount of X1 element also includes Hf element. Hf element exists in the matrix in the form of Cu5Hf, which has little effect on the conductivity of the alloy. Furthermore, Cu5Hf is a heat-resistant phase, which improves the alloy's resistance to softening temperature. By adding Hf element, the high-temperature stability of the copper alloy is improved while ensuring conductivity.

[0016] The Sn provided by this invention exists mainly in the form of interstitial solid solution in copper alloys. Due to the significant difference in the radius between Sn atoms and Cu atoms, dislocations are effectively pinned, dislocation movement is hindered, the formation of recrystallization nuclei is suppressed, the recrystallization temperature is increased accordingly, and the rapid recrystallization and grain growth of the alloy structure are prevented under high temperature conditions, thereby significantly improving the strength and heat resistance of the copper alloy.

[0017] The Zr provided by this invention has very low solubility in a Cu matrix. After addition, it dissolves into the copper matrix through solid solution treatment to form supersaturated solid solutions Cu5Zr and Cu3Zr. Subsequently, the solid solutions decompose into dispersed precipitates during heat treatment. The precipitation of Cu5Zr and Cu3Zr phases can reduce electron scattering and improve the conductivity of the alloy. On the other hand, it can also play a precipitation strengthening role, greatly improving the strength and heat resistance of the alloy. At the same time, an appropriate amount of Zr can greatly reduce the grain boundary energy and generate solute dragging and second-phase pinning of grain boundaries, thereby greatly improving heat resistance and thermal stability.

[0018] Preferably, the microstructure of the copper alloy includes Zr4Sn precipitates, Cu3Zr precipitates, and Cu5Zr precipitates;

[0019] The Zr4Sn precipitates have a size of 1–100 nm and an area percentage of 0.1–0.5% in the copper alloy microstructure.

[0020] The Cu3Zr precipitates have a size of 1–200 nm and an area ratio of 0.1–1% in the copper alloy microstructure.

[0021] The Cu5Zr precipitates have a size of 1–50 nm and an area ratio of 0.1–0.5% in the copper alloy microstructure.

[0022] Preferably, the mass percentage of the Sn element at the grain boundary is 0.001 wt% to 0.004 wt%.

[0023] Preferably, the tin-containing brittle phase within the grain boundaries has a size of 1–50 nm and a content of 1–80 phases / mm. 2 The content of particles with a size of 50-200nm is 1-50 per mm. 2 .

[0024] Sn tends to accumulate at grain boundaries, forming brittle phases (such as Cu3Sn and Cu6Sn5), which reduces the grain boundary binding energy, induces intergranular fracture, and is detrimental to plastic processing. Simultaneously, Sn enrichment at grain boundaries reduces electrical conductivity. To achieve good processing performance and minimize the impact on conductivity, the mass percentage of Sn at grain boundaries in this invention is 0.001 wt% to 0.004 wt%.

[0025] Preferably, in order to achieve a balance between conductivity and heat resistance, and to realize the excellent conductivity performance of 100% IACS and the high heat resistance performance of 350℃, the content of X1 element is further preferably set to 0.004wt%~0.006wt%.

[0026] The copper alloy provided by this invention also includes 0.001wt% to 0.005wt% of graphene.

[0027] This invention adds an appropriate amount of graphene to copper alloys, which improves strength, refines grain size, and enhances thermal stability. On one hand, graphene has a strong interfacial bond with the copper matrix, hindering dislocation movement and delaying plastic deformation, thus improving strength. On the other hand, graphene's high melting point and chemical inertness inhibit grain coarsening in copper alloys at high temperatures, reducing strength loss and improving heat resistance and thermal stability. Simultaneously, it reduces the occurrence of strong lattice distortion in the copper alloy, minimizing increased electron scattering and reducing the alloy's conductivity.

[0028] Preferably, the O content in this invention is controlled to be ≤5ppm. This invention controls the O element to avoid adverse effects, minimizing excessive burning loss of alloying elements due to O addition, and also minimizing the formation of inclusions and other defects that could affect subsequent processing. Furthermore, if the O content is too high, the added Zr easily combines with oxygen to form ZrO2 inclusions, significantly weakening the effect of Zr addition.

[0029] Preferably, the content of other unavoidable impurities besides the above-mentioned elements, such as Fe, Al, Si, Mn, Ni, Co, S, Se, Te, Sb, Bi, As, etc., is ≤5ppm for each element and ≤30ppm for the total amount of impurities.

[0030] More preferably, in order to further improve conductivity, the content of each individual impurity element such as Fe, Al, Si, Mn, Ni, Co, S, Se, Te, Sb, Bi, and As in the unavoidable impurities is ≤3ppm.

[0031] Preferably, the crystal orientation of the copper alloy in this invention satisfies the following condition within a deviation angle of less than 15°: Brass orientation {011} <211> The area ratio is 1-10%, S orientation {123} <634> The area ratio is 5-15%, Copper orientation {112} <111> The area ratio is 1-10%.

[0032] Copper alloys are used as key components in connectors, busbars, relay contacts, and heat dissipation systems, all of which require plastic deformation processing, such as stamping, etching, cold heading, hot heading, and bending. If the copper alloy has poor plastic deformation properties, uneven deformation can easily occur at stress concentration points during plastic deformation processing, leading to poor flatness and, in severe cases, cracking. The most common mode of plastic deformation in copper alloys is slip, where a portion of a crystal slips relative to another portion along a certain crystal plane and orientation; the accumulation of a large amount of slip constitutes macroscopic plastic deformation. Copper alloys are polycrystalline; under applied stress, the superposition of plastic deformation of different crystals (grains) within the copper alloy constitutes plastic deformation. The area ratio of different orientations on the processed surfaces of the copper alloy (such as the drawing / rolling direction) has a significant impact on improving the alloy's plastic deformation capability. To further enhance the plastic deformation capability of the alloy, this invention controls the area ratio of different orientations on the alloy's machined surface, ensuring that the crystal orientation of the copper alloy strip satisfies the following condition within a deviation angle of less than 15°: Brass orientation {011} <211> The area ratio is 1-10%, S orientation {123} <634> The area ratio is 5-15%, Copper orientation {112} <111> The area ratio is 1-10%. When the area ratio of different orientations of the processed surface meets the above requirements, the plastic deformation capacity of the alloy is improved. During the plastic deformation treatment of the alloy, such as stamping, etching, cold heading, hot heading and bending, there will be no problem of uneven deformation or cracking, thus meeting the material processing requirements.

[0033] Preferably, in this invention, the area ratio of each orientation with a Schmitt factor ≥ 0.3 on the copper alloy machining surface is 80-95%, and the area ratio of each orientation with a Schmitt factor ≥ 0.4 is 60-85%.

[0034] The plastic deformation capacity of an alloy is also related to its Schmidt factor, and the closer the Schmidt factor is to its maximum value in each orientation, the better its plastic deformation capacity. The Schmidt factor is the ratio of the shear stress on the slip plane of a crystal to the applied stress, and can be calculated using cosΦ*cosλ, where Φ is the angle between the applied stress direction and the normal to the slip plane, and λ is the angle between the applied stress direction and the slip direction. The Schmidt factor is also called the orientation factor; the larger the value, the greater the shear stress acting on the slip plane, and the easier the crystal is to deform. Since Φ+λ satisfies 90°, it can be known that the Schmidt factor has a maximum value of 0.5. Copper alloy strips are polycrystalline, and due to processing methods, many grains with different orientations exist within the copper alloy. Through processing techniques, the Schmidt factor values ​​of different crystals within the copper alloy strip can be increased, bringing them closer to their maximum value, thereby improving the cold heading deformation performance of the material. Therefore, in order to achieve better cold heading deformation performance, the present invention further controls the Schmidt factor on the strip surface of the copper alloy. When the area of ​​each orientation with a Schmidt factor ≥ 0.3 on the copper alloy processing surface is 80-95% and the area of ​​each orientation with a Schmidt factor ≥ 0.4 is 60-85%, the plastic deformation capability of the alloy is further improved.

[0035] Preferably, the copper alloy has a hardness of HV80-HV110, an electrical conductivity of not less than 100% IACS, a thermal conductivity of not less than 390 W / (m·K), and after being held at 350℃ for 10 minutes three times consecutively, the copper alloy retains more than 97% of its original hardness.

[0036] The heat resistance of a material refers to the change in its room temperature mechanical properties after being heated to different temperatures under certain holding time conditions. Generally, maintaining the hardness of copper alloys above 80% (i.e., the ratio of room temperature hardness after heat treatment to the original hardness) is used as the benchmark for judging whether the material has softened. For copper alloys used in IGBT heat sink substrates, three high-temperature treatment steps are required during the assembly of high-current power modules. These steps are crucial to the thermal stability of the copper alloys used in IGBT heat sink substrates, because any softening of the substrate will lead to the failure of power module assembly. In order to meet the assembly requirements under high-temperature welding conditions, it is appropriate to use the ratio of the residual hardness to the original hardness after holding at 350℃ for 10 minutes three times consecutively to evaluate its heat resistance. When the heat resistance of the material is poor, the grains in the structure tend to grow rapidly, leading to a decrease in the hardness and strength of the material, which in turn leads to softening, deformation and warping of the heat sink substrate, making it impossible to maintain surface flatness, thus failing to complete the assembly of the power module. In severe cases, insufficient heat dissipation may cause the IGBT chip to overheat and fail.

[0037] The technical solution adopted by the present invention to solve the second technical problem is: a method for preparing a high heat-resistant and high electrical conductivity copper alloy, characterized in that: the preparation process of the copper alloy includes: smelting → casting → continuous extrusion → solution treatment → drawing → low temperature annealing → length setting → packaging;

[0038] The copper alloy is prepared and smelted according to the mass percentage of each element.

[0039] The low-temperature annealing temperature is 150℃~350℃, and the holding time is 2~10h.

[0040] The low-temperature annealing process provided by this invention has two main effects: firstly, it can relieve stress by eliminating stress concentration, thus facilitating deformation processing such as cold heading of alloys; secondly, the synergistic effect of the ratio of Ag, Zr and Sn can precipitate strengthening phases, thereby achieving excellent heat resistance and thermal stability.

[0041] After cold working and stretching deformation with a certain processing rate, additional precipitation channels and driving forces are provided for aging treatment. This allows the small amount of elements dissolved in the matrix to precipitate further, ensuring that the appropriate precipitation amounts of Zr4Sn, Cu3Zr and Cu5Zr phases are obtained, thereby improving the conductivity, strength, heat resistance and thermal stability of the alloy. It can also work synergistically with an appropriate amount of Zr phase to reduce Sn grain boundary segregation and eliminate the risk of grain boundary cracking.

[0042] When the temperature of the low-temperature annealing process is below 150℃, the excessively low temperature only releases the internal stress of the alloy without allowing further precipitation, thus reducing the alloy's strength and conductivity, and failing to achieve effective heat resistance and thermal stability. Conversely, when the annealing temperature exceeds 350℃, even with the addition of an appropriate amount of Ag, the excessively high temperature causes the existing precipitated strengthening phases to grow rapidly, especially Cu5Zr. This not only significantly reduces the alloy's conductivity but also impairs its plastic processing properties, potentially leading to deformation and cracking. Therefore, the low-temperature annealing process should be performed at temperatures between 150℃ and 350℃, with a holding time of 2 to 10 hours.

[0043] Preferably, the smelting process temperature is maintained at 1160–1190℃, and the surface of the molten copper is covered with charcoal with a thickness of 60–100 mm. The casting adopts an upward continuous casting method, with a casting temperature of 1140–1170℃ and a drawing speed of 300–360 mm / min.

[0044] Preferably, the preheating temperature of the extrusion chamber in the continuous extrusion is 450-550℃, the preheating time is 1.5-2.5h, the extrusion temperature is 500℃-800℃, and the extrusion speed is 3-10m / min.

[0045] Continuous extrusion involves the intense plastic deformation of copper alloys at high temperatures and strain rates, leading to a sharp increase in dislocation density. When the deformation energy accumulates to a critical value, dynamic recrystallization is triggered, forming fine equiaxed grains. Therefore, continuous extrusion can eliminate the adverse effects of coarse as-cast microstructures, allowing recrystallized grains to continue to break down and refine the grain structure. Simultaneously, continuous extrusion can also create specific textures, with most of the cube texture transforming into copper and S textures. This ensures that the copper-type texture accounts for more than 55% of the measured area after continuous extrusion, preparing for the formation of specific textures and area proportions in subsequent products. Furthermore, continuous extrusion provides formation sites for the precipitation of second phases, resulting in a more uniform and dispersed distribution. It promotes the pinning of grain boundaries by precipitates such as Cr3Zr, inhibits the growth of recrystallized grains, and further refines the microstructure. When the extrusion temperature is below 500℃, the fluidity of the molten metal is poor, the solute diffusion is insufficient, and the deformation is more hindered during extrusion, which easily leads to cracking. When the extrusion temperature is above 800℃, it will cause oxidation or excessive burning of alloying elements, which is detrimental to the quality of hot-rolled billets. At the same time, problems such as coarse grains, insufficient precipitation of precipitates, and low conversion of copper texture are also likely to occur after extrusion, making it difficult to obtain a texture ratio in the final product that meets the requirements.

[0046] Preferably, the solution treatment process involves a solution temperature of 450–800°C and a solution time of 0.5–60 min.

[0047] The solution treatment of this invention is carried out by rapid cooling. After continuous extrusion, the solution is immediately introduced into the cooling water channel to achieve online solution treatment.

[0048] Further preferably, the cooling rate of the solution treatment process is 5–30 °C / s.

[0049] In the solution treatment process, to ensure a supersaturated solid solution and reduce the precipitation of strengthening phases during cooling, the cooling rate of the solution treatment process in this invention is controlled at 5–30 °C / s to obtain sufficient amounts of Copper and S-textures, and Schmidt factors in each orientation. When the cooling rate is below 5 °C / s, the alloy grains will coarsen; when the cooling rate is above 30 °C / s, the development of Copper and S-textures, and Schmidt factors in each orientation is insufficient.

[0050] Preferably, the drawing process has a drawing rate of 20% to 45%.

[0051] The purpose of drawing is to provide more energy and channels for the precipitation of precipitates, and to cause orientation rotation of the microstructure after solution treatment during the drawing process, thereby controlling the transformation of cubic texture to copper and S-textures. The drawing rate of this invention should be controlled between 20% and 45%. When the drawing rate is below 20%, sufficient internal energy cannot be provided for the subsequent aging process, leading to insufficient precipitation, resulting in lower strength and heat resistance of the final product, and a conductivity below 100% IACS. When the drawing rate is above 45%, the cubic texture in the microstructure will transform into a brass texture instead of copper and S-textures, leading to a reduction in the alloy's plastic deformation capacity, such as uneven cold heading, and in severe cases, significant warping and deformation. Simultaneously, the Schmidt factor content in each orientation is undesirable, which is detrimental to plastic deformation performance.

[0052] A third aspect of the present invention is to provide an application of the copper alloy as described above in connectors, busbars, relay contacts, and heat dissipation systems.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The copper alloy of this invention, by optimizing the mass ratio of Sn, Ag, and Zr, achieves improved high-temperature softening resistance and thermal stability while maintaining strength performance at a suitable cost. It achieves a hardness of HV80–HV110, an electrical conductivity of not less than 100% IACS, and a thermal conductivity of not less than 390 W / (m·K). Furthermore, after repeated exposure to 350°C for 10 minutes, the hardness of the copper alloy remains 97% higher than its original hardness, demonstrating excellent high-temperature stability and meeting the performance requirements of IGBT heat dissipation substrates. Attached Figure Description

[0055] Figure 1 This is a metallographic diagram of Example 1.

[0056] Figure 2 This is the metallographic structure diagram of Comparative Example 6. Detailed Implementation

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0058] The present invention provides Examples 1-5 and Comparative Examples 1-5, and the specific components are shown in Table 1 and Table 2.

[0059] The preparation method of the high heat resistance and high electrical conductivity copper alloy provided in Examples 1-5 of the present invention includes: the preparation process of the copper alloy includes: smelting → casting → continuous extrusion → solution treatment → drawing → low temperature annealing → length setting → packaging.

[0060] The smelting temperature provided by this invention is maintained at 1160-1190℃, and the surface of the molten copper is covered with charcoal with a thickness of 60-100mm.

[0061] The casting method provided by this invention adopts the upward continuous casting method, with a casting temperature of 1140~1170℃ and a pulling speed of 300~360mm / min.

[0062] The continuous extrusion process provided by this invention has an extrusion chamber preheating temperature of 450-550℃, a preheating time of 1.5-2.5h, an extrusion temperature of 500℃-800℃, and an extrusion speed of 3-10m / min.

[0063] The solution treatment process provided by this invention has a solution temperature of 450-800℃ and a solution time of 0.5-60min. The solution treatment is carried out by rapid cooling. After continuous extrusion, the solution immediately enters the cooling water channel to achieve online solution effect. The cooling rate of the solution treatment process is 5-30℃ / s.

[0064] The drawing process provided by this invention has a drawing rate of 20% to 45%.

[0065] The low-temperature annealing method provided by this invention has an annealing temperature of 150℃~350℃ and a holding time of 2~10h.

[0066] Table 1 shows the alloy composition of Examples 1-4 and Comparative Examples 1-3.

[0067]

[0068] Table 2 shows the alloy composition of Comparative Examples 4-6.

[0069]

[0070] Table 3 shows the specific values ​​of the main parameters for Examples 1-8 and Comparative Examples 1-9.

[0071]

[0072] Copper alloy strips were prepared using Examples 1-4 and Comparative Examples 1-6, and the resulting copper alloys were tested: Brass orientation {011} <211> Area ratio + S orientation {123} <634> Area ratio + Copper orientation {112} <111> Area ratio + Schmidt factor ≥ 0.3 area ratio of each orientation + Schmidt factor ≥ 0.4 area ratio of each orientation + hardness + electrical conductivity + thermal conductivity + and high temperature softening resistance under 20mm×20mm size.

[0073] Conductivity tests were conducted on a DC resistance tester using a bridge circuit, in accordance with GB / T 3048.2 2007 Test Methods for Electrical Properties of Wires and Cables Part 2: Test for Resistivity of Metallic Materials. The sample width was 20 mm and the length was 500 mm.

[0074] EBSD was used to analyze the texture type and area ratio of the strip. Texture ratio refers to the ratio of the area within 15° of each orientation deviation angle to the measured area.

[0075] The texture and Schmidt factor of the strip were measured using EBSD with a test deflection angle of 15°. The percentage of crystal area occupied by different textures and the percentage of crystal area of ​​different Schmidt factor sizes were statistically analyzed.

[0076] When testing the size of the precipitated phase and the Sn content at grain boundaries in the microstructure, the microstructure of the sample was observed under scanning electron microscopy and transmission electron microscopy. Based on the observation results, the average grain size of the alloy precipitated phase was calculated, and its number density was calculated respectively.

[0077] "High-temperature softening resistance - three consecutive times" is the ratio of the hardness of a copper alloy after being kept at 350°C for 10 minutes, then removed and allowed to cool naturally to room temperature, and the process is repeated twice (a total of three times) to the "hardness (room temperature)".

[0078] The results are shown in the table below:

[0079] Metallographic structure dimensions and proportions of copper alloys obtained in Examples 1-4 and Comparative Examples 1-3

[0080]

[0081] Texture, Schmidt factor and properties of copper alloys prepared in Examples 1-4 and Comparative Examples 1-6

[0082]

[0083] Note: "High-temperature softening resistance - three consecutive times" is the ratio of the hardness of the copper alloy after it has been kept at 350°C for 10 minutes, taken out, and naturally cooled to room temperature, and the process is repeated twice (a total of three times) to "hardness (room temperature)".

[0084] In summary, compared with Comparative Examples 1-9 provided by the present invention, the copper alloys prepared in Examples 1-8 of the present invention, by controlling the added elements and their mass percentages, achieved a hardness of HV80 to HV110, an electrical conductivity of not less than 100% IACS, and a thermal conductivity of not less than 390 W / (m·k). Furthermore, after being held at 350°C for 10 minutes three times consecutively, the hardness of the copper alloy was 95% higher than the original hardness of the copper alloy, demonstrating excellent high-temperature stability and meeting the performance requirements of IGBT heat dissipation substrates.

[0085] like Figure 1 As shown, in the alloy microstructure of Example 1 of this invention, the Zr4Sn, Cu3Zr and Cu5Zr precipitates play a role in improving heat resistance and thermal stability.

[0086] like Figure 2 As shown, the alloy microstructure of Comparative Example 6 has no other precipitated phases and belongs to the normal T2 microstructure of copper.

[0087] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A copper alloy with excellent high-temperature softening resistance, characterized in that, The components of the copper alloy include: Ag 0.001wt%~0.01wt%; P 0.0005wt%~0.002wt%; X1 0.003wt%~0.008wt%, with the balance being Cu and impurities; X1 is Sn and Zr; the mass ratio of Sn, Ag and Zr [Sn] / [Ag+Zr] is 0.5~2; The microstructure of the copper alloy includes Zr4Sn precipitates, Cu3Zr precipitates, and Cu5Zr precipitates; The Zr4Sn precipitates have a size of 1–100 nm and an area percentage of 0.1–0.5% in the copper alloy microstructure. The Cu3Zr precipitates have a size of 1–200 nm and an area ratio of 0.1–1% in the copper alloy microstructure. The Cu5Zr precipitates have a size of 1–50 nm and an area ratio of 0.1–0.5% in the copper alloy microstructure.

2. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The mass percentage of Sn element at the grain boundary is 0.001 wt% to 0.004 wt%.

3. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The brittle tin-containing phases within the grain boundaries range in size from 1 to 50 nm and have a content of 1 to 80 phases / mm. 2 The content of particles with a size of 50-200nm is 1-50 per mm. 2 .

4. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The copper alloy with excellent high-temperature softening resistance also includes 0.001wt% to 0.005wt% of graphene.

5. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The oxygen content in the copper alloy with excellent high-temperature softening resistance is controlled to be ≤5ppm.

6. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The impurities include Fe, Al, Si, Mn, Ni, Co, S, Se, Te, Sb, Bi, and As, with each element having a content ≤5ppm and the total impurities ≤30ppm.

7. The copper alloy with excellent high-temperature softening resistance according to claim 1, characterized in that, The crystal orientation of the copper alloy with excellent high-temperature softening resistance satisfies the following within a deviation angle of less than 15°: Brass orientation {011} <211> The area ratio is 1-10%, S orientation {123} <634> The area ratio is 5-15%, Copper orientation {112} <111> The area ratio is 1-10%.

8. A method for preparing a copper alloy with excellent high-temperature softening resistance according to any one of claims 1-7, characterized in that: The preparation process of this copper alloy includes: smelting → casting → continuous extrusion → solution treatment → drawing → low temperature annealing → length cutting → packaging; The copper alloy is prepared and smelted according to the mass percentage of each element. The low-temperature annealing temperature is 150℃~350℃, and the holding time is 2~10h.

9. The application of a copper alloy with excellent high-temperature softening resistance as described in any one of claims 1-7 in connectors, busbars, relay contacts, and heat dissipation systems.

Images