High-heat-resistance high-conductivity copper alloy, and preparation method and application thereof

Abstract

The application discloses a high-heat-resistance high-conductivity copper alloy and a preparation method and application thereof. The copper alloy comprises Ag 0.001wt%-0.01wt%, P 0.0005wt%-0.002wt%, X 10.003wt%-0.008wt% and the balance of Cu and impurities. The preparation process of the high-heat-resistance high-conductivity copper alloy comprises smelting, casting, continuous extrusion, solid solution, drawing, low-temperature annealing, sizing and packaging. According to the mass percentage of each element of the copper alloy, ingredients and smelting are carried out. In the low-temperature annealing process, the annealing temperature is 150 DEG C-350 DEG C, and the holding time is 2-10h.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and in particular to a high heat-resistant and high electrical conductivity copper alloy, its preparation method and application. Background Technology

[0002] With the increasing use of high current in electronic and electrical equipment, in order to reduce current density and diffuse the Joule...

[0003] The heat generated by heating is used in electronic and electrical equipment components, where pure copper materials such as oxygen-free copper, which have excellent conductivity, are suitable. However, pure copper materials suffer from insufficient heat resistance, meaning their hardness decreases significantly under high temperatures. For example, the assembly of high-current IGBT power modules requires three high-temperature treatment stages, with the highest temperature reaching 310°C and the longest duration reaching 5 minutes. Continuous and prolonged high-temperature conditions are crucial to the thermal stability of the copper alloy used in the IGBT heat sink substrate. Any failure of the copper material's heat resistance during any of these stages will cause the substrate to soften, thus affecting the assembly result of the IGBT power module.

[0004] Therefore, for copper materials used in IGBT heat sink substrates, the hardness must exceed 90% of the original hardness of the copper alloy after being subjected to 350℃ for 10 minutes three times consecutively. Simultaneously, with the increasing current and high efficiency of packaging technologies in electronic and electrical equipment, the requirements for the heat resistance, electrical conductivity, and thermal conductivity of copper materials used in IGBT heat sink substrates are becoming increasingly stringent, especially the thermal stability of the copper material, which must not exhibit fatigue under repeated high-temperature conditions. Using tough copper or oxygen-free copper will not meet the heat resistance requirements for repeated high-temperature soldering during the power module assembly stage, easily leading to softening, deformation, and warping of the heat sink substrate, making it impossible to maintain the surface flatness of the heat sink substrate, thus hindering the assembly of the power module. While using copper-tin or copper-iron alloys can improve heat resistance and thermal stability, the electrical and thermal conductivity are significantly reduced, and in severe cases, insufficient heat dissipation may cause the IGBT chip to overheat and fail.

[0005] Patent document CN115917023B discloses a copper alloy suitable for components of electronic and electrical equipment such as terminals and heat dissipation parts. Copper alloy plastic processing 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 hours conditions in the direction parallel to the rolling direction, and a ratio RSG / RSB of RSG under 180°C and 30 hours conditions in the direction parallel to the rolling direction to RSB under 180°C and 30 hours conditions in the direction orthogonal to the rolling direction exceeding 1.0. It can also take into account high conductivity and excellent heat resistance and stress relaxation resistance.

[0006] However, in order to further meet the requirements of fully suppressing heat generation when a large current is flowing, the heat resistance temperature needs to be increased to 350°C and the conductivity of the copper material needs to be increased to over 100% IACS. This patent does not meet these further requirements.

[0007] Therefore, there is an urgent need for a copper alloy that possesses both high heat resistance and high electrical conductivity. Summary of the Invention

[0008] 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.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A first aspect of the present invention is to provide a high heat-resistant and high electrical conductivity copper alloy, comprising:

[0011] Ag 0.001wt%~0.01wt%;

[0012] P 0.0005wt%~0.002wt%;

[0013] X1 0.003wt%~0.008wt% and

[0014] Cu and impurity balance;

[0015] X1 is one or more of the elements Hf, Sn, and Zr.

[0016] 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%.

[0017] 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%.

[0018] In this invention, an appropriate amount of X1 element is added, wherein Hf, Sn and Zr elements significantly improve the hardness and strength of the copper alloy, while also enhancing its heat resistance and thermal stability, which is beneficial for the alloy to maintain its heat resistance without decay under high temperature conditions repeatedly.

[0019] Hf exists in the matrix as Cu5Hf, which has little impact on the conductivity of the alloy. Furthermore, Cu5Hf is a heat-resistant phase, which improves the alloy's softening temperature. By adding Hf, the high-temperature stability of the copper alloy is improved while ensuring conductivity.

[0020] Sn exists mainly in copper alloys through interstitial solid solution. Due to the significant difference in the radius between Sn atoms and Cu atoms, this solid solution method produces a higher degree of lattice distortion in the crystal compared to substitutional solid solution. This effectively pins dislocations, hinders dislocation movement, and suppresses the formation of recrystallization nuclei, thereby increasing the recrystallization temperature and preventing the alloy grains from rapidly recrystallizing and growing under high temperature conditions. This significantly improves the strength and heat resistance of copper alloys.

[0021] Zr has very low solubility in the 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 reduces electron scattering, improving the alloy's conductivity, and also acts as precipitation strengthening, significantly improving the alloy's strength and heat resistance. Simultaneously, an appropriate amount of Zr can greatly reduce grain boundary energy and generate solute dragging and second-phase pinning of grain boundaries, thereby significantly improving heat resistance and thermal stability.

[0022] When the content of one or more of Hf, Sn, and Zr elements is less than 0.003 wt%, the solid solution strengthening effect is not significant, failing to effectively pin dislocations and hindering dislocation movement. Consequently, the improvement in the strength and heat resistance of the copper alloy is not significant, and its effect cannot be fully realized. On the other hand, when the content of one or more of Hf, Sn, and Zr elements exceeds 0.008 wt%, the excessive solid solution of Hf, Sn, and Zr elements in the matrix causes strong lattice distortion in the copper alloy, thereby enhancing electron scattering and reducing the conductivity of the alloy. Therefore, this invention controls the addition of X1 element content to be between 0.003 wt% and 0.008 wt%.

[0023] 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%.

[0024] Preferably, the X1 element is Sn and Zr, and the microstructure of the copper alloy includes precipitates, including Zr4Sn precipitates, Cu3Zr and Cu5Zr precipitates, wherein the size of the Zr4Sn precipitates is 1-300 nm, and the size of the Cu3Zr and Cu5Zr precipitates is 1-500 nm.

[0025] The Zr4Sn, Cu3Zr, and Cu5Zr precipitates provided by this invention can not only play a role in precipitation strengthening and improve the hardness and strength of the alloy, but also greatly improve the heat resistance of the alloy, especially enhance the thermal stability of the alloy and promote the non-degradation of heat resistance under high temperature conditions.

[0026] Zr4Sn is a hard and brittle intermetallic compound. This invention achieves dispersion strengthening and precipitation hardening by controlling the size of Zr4Sn, thereby improving the alloy's strength, hardness, and heat resistance. It also exhibits good stability at high temperatures, inhibits grain boundary movement, improves creep resistance, and enhances the alloy's thermal stability. While solid solutions of both Zr and Sn reduce the electrical conductivity of copper, the formation of Zr4Sn reduces the number of dissolved atoms, thus restoring conductivity. This invention avoids increased brittleness, decreased processing performance (such as rolling and stretching), stress concentration, increased crack susceptibility, and reduced conductivity by controlling the size of Zr4Sn.

[0027] This invention controls the size of the Cu3Zr precipitates, allowing nanoscale Cu3Zr precipitates to impede dislocation movement through coherent / semi-coherent interfaces, thus exerting an age-hardening effect and significantly improving strength. Furthermore, the Cu3Zr precipitates exhibit stable properties at medium temperatures (300–500℃), which is beneficial to the alloy's heat resistance and thermal stability. Simultaneously, Cu3Zr precipitation reduces Zr solid solution, improving electrical conductivity. Compared to Zr4Sn, Cu3Zr has a lower impact on the alloy's conductivity. However, at excessively high temperatures, it may coarsen, with coarse Cu3Zr potentially leading to increased brittleness and decreased processing performance (such as rolling and stretching). Simultaneously, coarse precipitates cause stress concentration, increasing crack susceptibility and further reducing conductivity.

[0028] Cu5Zr typically forms after Cu3Zr precipitation, usually at higher temperatures or with higher Zr content. It is more stable than Cu3Zr, with a melting point greater than 1100℃. It retains its strengthening effect at 500–700℃, exhibiting extremely high high-temperature stability. Similar to Cu3Zr, it reduces Zr solid solution and strengthens through precipitation. However, it exhibits strong electron scattering, which is detrimental to the alloy's conductivity, necessitating strict control of its content and size. A high content of the hard and brittle phase in Cu5Zr can become a crack initiation point, especially when distributed at grain boundaries, significantly reducing toughness and ductility, and making it prone to cracking during processing (such as cold rolling cracks).

[0029] Preferably, the contents of the Zr4Sn precipitate, Cu3Zr, and Cu5Zr precipitates are 1 to 100 per mm. 2 1-100 pieces / mm 2 and 1 to 50 pieces / mm 2 .

[0030] Preferably, the mass percentage of the Sn element at the grain boundary is 0.001 wt% to 0.008 wt%.

[0031] This invention, through strict control of the Sn content, aims to reduce the driving force of grain boundary segregation by keeping the tin content low, thus preventing Sn enrichment at grain boundaries. Simultaneously, elements such as Zr and P in this invention reduce Sn enrichment at grain boundaries through competitive segregation or the formation of stable compounds. For example, P competes with Sn for grain boundary segregation sites, forming Sn-P clusters and reducing the concentration of free Sn; Zr forms stable phases such as Zr4Sn with Sn, fixing Sn atoms and reducing their migration to grain boundaries.

[0032] In addition, designing special processing techniques, such as homogenization annealing (to promote uniform Sn distribution) and hot extrusion process (to promote dynamic recrystallization, refine grains, reduce the total area of ​​grain boundaries, and thus reduce Sn segregation concentration), are all beneficial to controlling the Sn element at grain boundaries to meet the minimum requirements.

[0033] More preferably, the microstructure of the copper alloy further includes a tin-containing brittle phase, wherein the tin-containing brittle phase has a size of 1–50 nm at the grain boundaries and a content of 1–200 phases / mm. 2 The content of particles with a size of 50-200nm is 1-100 per mm. 2 .

[0034] With the addition of Sn content, brittle tin-containing phases Cu2Sn, Cu3Sn, and Cu6Sn5 gradually precipitate. A certain amount of nano-sized Cu2Sn, Cu3Sn, or Cu6Sn5 precipitation provides precipitation strengthening, which is beneficial for improving the alloy's strength, hardness, and heat resistance. Simultaneously, the strengthening phase helps improve the alloy's thermal stability, enabling it to withstand repeated high-temperature conditions and mitigating thermal fatigue failure. However, excessive and coarse Cu3Sn or Cu6Sn5 precipitates are prone to creating crack initiation sites, leading to decreased elongation and hindering the alloy's plastic processing. In severe cases, cracking may occur during cold heading and bending. Furthermore, coarse precipitates can increase electron scattering, reducing conductivity by 30–50%.

[0035] More preferably, the tin-containing brittle phase includes Cu2Sn, Cu3Sn, and Cu6Sn5.

[0036] The copper alloy provided by this invention also includes 0.001wt% to 0.005wt% of graphene.

[0037] As a two-dimensional nanomaterial, graphene, when added in appropriate amounts to copper alloys, enhances strength, refines grain size, and improves thermal stability. On one hand, graphene exhibits strong interfacial bonding 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. When the content of one or more types of graphene is below 0.001 wt%, the strengthening effect is not significant, and the improvement in mechanical and heat resistance properties is affected. When the graphene content exceeds 0.005 wt%, it causes strong lattice distortion in the copper alloy, leading to enhanced electron scattering and reduced conductivity. Therefore, this invention further controls the graphene content to be between 0.001 wt% and 0.005 wt%.

[0038] Preferably, the O content in this invention is controlled to be ≤5ppm.

[0039] This invention controls the amount of oxygen (O) in the alloy to avoid exceeding a certain content, which could have adverse effects. It aims to minimize excessive burning loss of alloying elements due to O addition and to reduce 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.

[0040] 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.

[0041] 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, and the total content of impurities is ≤30ppm.

[0042] 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%.

[0043] 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.

[0044] 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%.

[0045] 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 ratio of each orientation with a Schmidt factor ≥ 0.3 on the copper alloy processing surface is 80-95% and the area ratio of each orientation with a Schmidt factor ≥ 0.4 is 60-85%, the plastic deformation capability of the alloy is further improved.

[0046] 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 95% of its original hardness.

[0047] 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.

[0048] 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;

[0049] The copper alloy is prepared and smelted according to the mass percentage of each element.

[0050] The low-temperature annealing temperature is 150℃~350℃, and the holding time is 2~10h.

[0051] The low-temperature annealing process provided by this invention serves two purposes: firstly, it provides stress-relieving annealing, eliminating the effects of stress concentration and facilitating deformation processing such as cold heading of the alloy; secondly, it allows for the precipitation of strengthening phases, achieving excellent heat resistance and thermal stability. After cold working and drawing deformation at a certain processing rate, it provides additional precipitation channels and impetus for aging treatment, enabling the further precipitation of small amounts of elements dissolved in the matrix. This ensures appropriate precipitation amounts of Zr4Sn, Cu3Zr, and Cu5Zr phases, thereby improving the alloy's electrical conductivity, strength, heat resistance, and thermal stability. It also reduces Sn grain boundary segregation, eliminating the risk of grain boundary cracking. 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 is above 350℃, 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.

[0052] 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.

[0053] 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.

[0054] 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, solute diffusion is insufficient, and deformation is hindered during extrusion, making cracking more likely. When the extrusion temperature is above 800℃, it can cause oxidation or excessive burning of alloying elements, which is detrimental to the quality of the hot-rolled billet. It also easily leads to problems such as coarse grains in the extruded microstructure, insufficient precipitation of precipitates, and a low conversion of copper texture, making it difficult to achieve the required texture ratio in the final product. Preferably, the solution treatment process involves a solution temperature of 450–800℃ and a solution time of 0.5–60 min.

[0055] 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.

[0056] Further preferably, the cooling rate of the solution treatment process is 5–30 °C / s.

[0057] 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.

[0058] Preferably, the drawing process has a drawing rate of 20% to 45%.

[0059] 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.

[0060] 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.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] The copper alloy of this invention, through optimized control of the added Ag, P, and X1 elements and their mass percentages, improves strength, high-temperature softening resistance, and thermal stability at a suitable cost, achieving 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 repeated exposure to 350°C for 10 minutes, the hardness of the copper alloy still remains higher than 95% of its original hardness, demonstrating excellent high-temperature stability and meeting the performance requirements of IGBT heat dissipation substrates. Attached Figure Description

[0063] Figure 1 This is a metallographic diagram of Example 4.

[0064] Figure 2 This is the metallographic structure diagram of Comparative Example 9. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0066] The present invention provides Examples 1-8 and Comparative Examples 1-9, and the specific components are shown in Tables 1 and 2.

[0067] The preparation method of the high heat resistance and high electrical conductivity copper alloy provided in Examples 1-14 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.

[0068] 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.

[0069] The casting method provided by this invention is top-draw continuous casting, with a casting temperature of 1140~1170℃ and a drawing speed of 300~360mm / min.

[0070] 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.

[0071] 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.

[0072] The drawing process provided by this invention has a drawing rate of 20% to 45%.

[0073] The low-temperature annealing method provided by this invention has an annealing temperature of 150℃~350℃ and a holding time of 2~10h.

[0074] Table 1 shows the alloy composition of Examples 1-8.

[0075]

[0076] Table 2 shows the alloy compositions of Comparative Examples 1-5.

[0077]

[0078] Table 3 shows the specific values ​​of the main parameters for Examples 1-8 and Comparative Examples 1-9.

[0079]

[0080] Copper alloy strips were prepared using Examples 1-14 and Comparative Examples 1-9, 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 in 20mm×20mm size.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] "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)".

[0086] The results are shown in the table below:

[0087] Metallographic structure dimensions and proportions of copper alloys obtained in Examples 1-8 and Comparative Examples 1-9

[0088]

[0089] Texture, Schmidt factor and properties of copper alloys prepared in Examples 1-8 and Comparative Examples 1-9

[0090]

[0091] 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)".

[0092] 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.

[0093] like Figure 1 As shown, in the alloy microstructure of Example 4 of this invention, the Cu3Zr and Cu5Zr precipitates play a role in improving heat resistance and thermal stability.

[0094] like Figure 2 As shown, the alloy microstructure of Comparative Example 9 has no other precipitated phases and belongs to the normal copper T2 microstructure.

[0095] 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 high heat-resistant and high electrical conductivity copper alloy, characterized in that, Each elemental component, including: Ag 0.001wt%~0.01wt%; P 0.0005wt%~0.002wt%; X1 0.003wt%~0.008wt% and Cu and impurity balance; X1 is selected from the following group: (1) Sn and Zr; or (2) Hf, Sn and Zr; The microstructure of the copper alloy includes precipitates, which include Zr4Sn precipitates, Cu3Zr and Cu5Zr precipitates. The size of the Zr4Sn precipitates is 1-300 nm, and the size of the Cu3Zr and Cu5Zr precipitates is 1-500 nm. The contents of the Zr4Sn precipitate, Cu3Zr, and Cu5Zr precipitates are 1–100 per mm, respectively. 2 1-100 pieces / mm 2 and 1 to 50 pieces / mm 2 .

2. The high heat-resistant and high electrical conductivity copper alloy according to claim 1, characterized in that, The content of the X1 element is 0.004wt% to 0.006wt%.

3. The high heat-resistant and high electrical conductivity copper alloy according to claim 1, characterized in that, The mass percentage of Sn element at the grain boundary is 0.001 wt% to 0.008 wt%.

4. The high heat-resistant and high electrical conductivity copper alloy according to claim 1, characterized in that, The microstructure of the copper alloy also includes a tin-containing brittle phase, which has a size of 1–50 nm at the grain boundaries and a content of 1–200 phases / mm. 2 The content of particles with a size of 50-200nm is 1-100 per mm. 2 .

5. The high heat-resistant and high electrical conductivity copper alloy according to claim 4, characterized in that, The tin-containing brittle phases include Cu2Sn, Cu3Sn and Cu6Sn5.

6. The high heat-resistant and high electrical conductivity copper alloy according to claim 1, characterized in that, The high heat-resistant and high electrical conductivity copper alloy also includes 0.001wt% to 0.005wt% of graphene.

7. A method for preparing a high heat-resistant and high electrical conductivity copper alloy according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: melting → casting → continuous extrusion → solution treatment → drawing → low-temperature annealing; The high heat-resistant and high electrical conductivity copper alloy is prepared and smelted according to the mass percentage of each element as described in any one of items 1-6. The low-temperature annealing temperature is 150℃~350℃, and the holding time is 2~10h.

8. The application of a high heat-resistant and high conductivity copper alloy according to any one of claims 1-6 in connectors, busbars, relay springs and heat dissipation systems.

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