Copper alloy for electronic and electric parts and method for producing the same

Abstract

The copper alloy for electronic and electrical components disclosed in this invention comprises: 1–2.8 wt% Ni, 0.2–0.8 wt% Si, 0.2–1.2 wt% Sn, with the remainder consisting of Cu and unavoidable impurities; the Sn concentration difference between the surface region (±5 μm at 1 / 8 of the thickness direction) and the central region (±5 μm at 1 / 2 of the thickness direction) is less than 0.1 wt%; in the microstructure of the alloy, disk-shaped δ-Ni₂Si precipitates with a particle size of 5–30 nm are present in the parent phase at a concentration of 10... 4 pcs / mm 2 ~8×10 6 pcs / mm 2 The distribution density of the δ-Ni2Si precipitates with a particle size of 5–30 nm exists. This invention limits the distribution density of the δ-Ni2Si precipitates by controlling the amount of alloying elements added and the concentration distribution of Sn. This improves the ability to resist deformation and fracture caused by tensile stress in the outer layer of the deformation zone during bending processing while ensuring the electrical conductivity of the alloy, and also takes into account excellent bending performance and thermal stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of copper alloys, and particularly relates to a copper alloy for electronic and electrical components and a preparation method and application thereof. BACKGROUND

[0002] With the development of electronic and electrical components towards light weight, miniaturization and thin wall, the conditions of the related bending materials become severe, which requires the materials to have high strength and high electrical conductivity while having excellent bending processability to improve the component formability. Although the connector realizes electrical connection through elastic contact of the material, the contact pressure will gradually decrease due to stress relaxation phenomenon under high temperature environment, and if the connector uses a material with low stress relaxation characteristic, contact failure may occur under high temperature environment. In order to ensure the contact reliability between the electronic and electrical components such as connectors, the material is also required to have excellent stress relaxation characteristic. In addition, the heat generation of the connector will increase with the increase of the contact resistance of the contact part, so the material is required to have higher thermal stability under more severe high temperature environment.

[0003] The existing Cu-Fe-P alloy has good processability and good electrical conductivity, but its comprehensive performance indicators such as tensile strength and high temperature resistance cannot meet the use requirements; Cu-Cr-Zr has high strength and electrical conductivity, but it is difficult to balance the bending processability; Cu-Ni-Si alloy is a precipitation strengthened alloy, and the alloy has high strength and medium electrical conductivity after aging. Because it does not contain toxic elements such as Be and has low cost, it is widely used. However, the existing Cu-Ni-Si alloy has large fatigue fluctuation, and has defects of not ideal processing ease and bending processability, which is not enough to be used as electronic component material of various specified shapes under high temperature and high vibration environment. It is urgent to develop a Cu-Ni-Si alloy which can resist deformation and rupture caused by tensile stress of the outer layer of the deformation zone during bending process, while balancing the electrical conductivity and thermal stability. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a copper alloy for electronic and electrical components and a preparation method thereof, which can resist deformation and rupture caused by tensile stress of the outer layer of the deformation zone during bending process, while balancing the electrical conductivity and thermal stability.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a copper alloy for electronic and electrical components, wherein the alloy comprises, by mass percentage: 1-2.8 wt% Ni, 0.2-0.8 wt% Si, 0.2-1.2 wt% Sn, and the remainder is composed of Cu and unavoidable impurities; the concentration difference of Sn in the surface region at 1 / 8 ± 5 μm along the thickness direction from the surface of the alloy strip is less than 0.1 wt% and the concentration in the central region at 1 / 2 ± 5 μm along the thickness direction from the surface of the alloy strip is less than 0.1 wt%; in the microstructure of the alloy, disk-shaped δ-Ni2Si precipitates with a particle size of 5-30 nm are present in the parent phase at a concentration of 10 4 pcs / mm 2 ~8×10 6 pcs / mm 2 The distribution density exists.

[0006] Ni, in its infinite solid solution within the copper matrix, provides solid solution strengthening, enhancing the alloy's strength. Simultaneously, Ni and Si can form nanoscale Ni-Si-based intermetallic compounds, further improving conductivity and enhancing the alloy's strength and processing precision through precipitation strengthening. If the Ni content is less than 1 wt%, the precipitated phase is insufficient, resulting in low conductivity. Conversely, if the Ni content exceeds 2.8 wt%, the Ni-Si-based intermetallic compounds agglomerate, losing their strengthening effect. Therefore, the Ni content should be between 1 and 2.8 wt%.

[0007] Like Ni, Si is an element that enhances strength and can form Ni-Si-based intermetallic compounds with Ni. If the Si content is less than 0.2 wt%, a sufficient amount of precipitated phase cannot be formed, thus failing to achieve a strengthening effect. On the other hand, if the Si content exceeds 0.8 wt%, excess Si dissolves in the copper matrix, severely affecting conductivity and workability. Furthermore, during casting or hot working, cracks are easily generated due to the segregation of Si compounds, leading to a decrease in thermal stability. Therefore, the Si content should be 0.2–0.8 wt%.

[0008] Sn exists mainly in the form of solid solution in copper, as solute atoms dissolved in the lattice with Cu atoms as solvent to form α phase with face-centered cubic lattice, having solid solution strengthening effect, which is used together with precipitation strengthening and work hardening. It can hinder the migration of atoms and dislocations, inhibit the growth of Ni-Si-based precipitates during heat treatment, further refine and make the distribution uniform, which is beneficial to obtain higher strength under small deformation, further improve bending processability and thermal stability, so as to have higher reliability. If the content of Sn is less than 0.2wt%, it is not ideal for improving the performance of the alloy, on the other hand, if the addition amount of Sn exceeds 1.2wt%, it will lead to the decrease of elongation and electrical conductivity, and the bending processability when deformed is reduced. Therefore, the content of Sn should be 0.2-1.2wt%.

[0009] As preferred, the copper alloy of the present application can contain at least one element selected from Fe, Mg, Mn, P, Zn in a total amount of 1wt% or less. Among them, Fe improves the strength by forming Fe-Si compound and can improve the hot rolling property, Mg and Sn can significantly improve the stress relaxation resistance through synergistic effect, Mn and P have the effect of improving the hot working property, and Zn has the effect of improving the soldering tin heat resistance and weather resistance. If the total content of the above optional additive components is 1wt% or less, the improvement effect of various properties can be achieved, otherwise, if these elements exceed 1wt%, the electrical conductivity may be reduced, or cracks may occur during hot rolling, in addition, the elements hinder the behavior of dislocations so that the release of deformation after bending is hindered, resulting in uneven distribution of deformation, affecting the bending processability of the final material. Therefore, the total content of the above optional additive components should be 1wt% or less.

[0010] The concentration difference between the Sn concentration in the surface layer region 5μm from the surface of the strip material of the alloy in the thickness direction of the plate 1 / 8± and the Sn concentration in the central region 5μm from the surface of the strip material of the alloy in the thickness direction of the plate 1 / 2± of the present application is 0.1wt% or less. This difference is the segregation degree of Sn element, and for bending processability, the smaller the concentration difference is, the better. If the Sn concentration difference is greater than 0.1wt%, the change of Sn concentration is too large, the local orientation difference is large, the lattice distortion is more serious, the scattering occurs when the electrons move, the resistance to electron movement increases, and the precipitation phase particles are not easy to precipitate, which may reduce the electrical conductivity and bending processability. When the Sn concentration difference is less than 0.1wt%, the obtained microstructure has small average grain size, which is beneficial to the dynamic recovery, the distortion energy is reduced, the mobile dislocation density is reduced, not only the electrical conductivity and bending processability can be effectively improved, but also the thermal stability can be well improved, and at the same time, it can be directly used as a contact in subsequent use, further improving the weldability and plating peel resistance.

[0011] The present inventors have found that, in the Cu-Ni-Si-Sn alloy, through different heat treatment processes, the second phase formed by the precipitation of supersaturated solute atoms Ni and Si from the matrix during aging has different morphologies (spherical, needle-like, rod-like, disc-like, etc.), but the performance improvement is mainly achieved by the disc-like δ-Ni2Si in the Ni-Si phase, which is the main second phase in the initial aging or the final aging of the alloy

[0012] The habit plane is parallel to (110) Cu or (11119) Cu The disc-like δ-Ni2Si phase has a disc-like shape with a length of 5 nm to 30 nm and a width of 5 nm or less, and is dispersed in the copper matrix. The disc-like δ-Ni2Si phase has a strong pinning effect on the grain boundaries, increases the critical stress of the alloy during slip deformation, effectively prevents the migration of dislocation lines and subgrain boundaries caused by cyclic stress and strain, and thus improves the plastic deformation resistance of the copper alloy. In addition, the disc-like δ-Ni2Si phase has good interface stability during heating, effectively prevents recovery and recrystallization, and improves the bending processability and thermal stability. 4 2 6 2 The disc-like δ-Ni2Si phase has a strong pinning effect on the grain boundaries, increases the critical stress of the alloy during slip deformation, effectively prevents the migration of dislocation lines and subgrain boundaries caused by cyclic stress and strain, and thus improves the plastic deformation resistance of the copper alloy. In addition, the disc-like δ-Ni2Si phase has good interface stability during heating, effectively prevents recovery and recrystallization, and improves the bending processability and thermal stability.

[0013] The phase difference between adjacent grains is considered to be intragranular strain when the phase difference is 15° or less. Since the region with a phase difference of 0° or more and 1° or less is difficult to disappear even after heat treatment, the intragranular strain rate is evaluated by calculating the region with a phase difference of 0° or more and 1° or less in the region with a phase difference of 15° or less. Preferably, in the alloy of the present application, the intragranular strain rate η is greater than 0.05% and less than 10%, wherein the intragranular strain rate η = A1 / A0 x 100%, A1 is the proportion of grain boundaries with a phase difference of 0° or more and 1° or less, and A0 is the proportion of grain boundaries with a phase difference of 15° or less. If η is 10% or more, the effect of the outer periphery of the bending process on the internal deformation stress is reduced, and thus orange peel cracking can occur, or when used in electronic and electrical components, the risk of short circuiting and fire can increase. If η is 0.05% or less, the heat resistance is poor and the thermal stress relaxation rate is reduced. When the intragranular strain rate satisfies the predetermined value, the stacking fault energy of the alloy and the substructure present in the matrix increase the recrystallization temperature of the alloy, thereby improving the heat resistance and satisfying the bending property. ​​​

[0014] Generally, the bending workability is evaluated by the ratio R / t of the minimum bending radius R at which no cracks occur in a 90° bending test to the plate thickness t. With the miniaturization and thinning of parts, higher requirements are placed on the bending workability. As a preference, for the plate strip of the alloy of the present application, the average roughness Ra of the outer circumferential surface of the bending workability part at the time of adjustment of R / t = 0.5 after a 90° bending test along the transverse direction of rolling is 4.0 μm or less, the roughness of the surface bending workability outer circumferential surface is sufficiently small, the bendability is excellent, and the uniform adhesion of plating to parts obtained by bending workability after stamping and the contact reliability between electronic and electric parts are ensured.

[0015] As a preference, the plate strip of the alloy of the present application has a thermal stress relaxation rate of 20% or less and an electrical conductivity of 40% IACS or more after exposure to 150°C for 1000 h. The plate strip of the alloy of the present application has excellent dimensional stability and thermal shock resistance, the bending deformation angle value changes by 5° or less before and after heat treatment, and no significant cracks or damage occur on the surface after 3 cold-heat cycles at a temperature condition of 25 to 300°C. The contact reliability between electronic and electric parts is ensured, and further the current load capacity of the connecting terminal, particularly the load performance after high-temperature aging, is ensured, and the requirements for temperature rise durability of, for example, high-power connectors are well satisfied.

[0016] The present application also provides a preparation method of the copper alloy for electronic and electric parts as described above, comprising the following steps: melting and casting → homogenization annealing → hot deformation → primary cold rolling → annealing → secondary cold rolling → solution quenching treatment → tertiary cold rolling → gradient aging treatment → fine cold rolling → gradient low-temperature short-time heat treatment, wherein the first gradient temperature of the gradient aging treatment is 500 to 600°C, and the temperature is kept for 5 to 12 h, then the temperature is decreased to the second gradient temperature of 200 to 350°C at a cooling rate of 0.1 to 50°C / min, and the temperature is kept for 8 to 12 h, and the temperature difference between the first gradient temperature and the second gradient temperature is 150 to 350°C.

[0017] Gradient aging treatment: first, a first stage, at a first gradient temperature of 500-600°C for 5-12h, the alloy first undergoes a continuous phase transformation process, a large number of dispersed nucleation sites are formed in advance, and extremely small, coherent δ-Ni2Si phase with the matrix is obtained in the early aging stage, so that the alloy has good thermal stability without affecting the strength and hardness; then enter the second stage, the temperature is reduced to the second gradient temperature of 200-350°C, and the temperature is kept for 8-12h. When the second gradient temperature is lower than the first gradient temperature, the highest performance combination can be obtained. In order to make the bending property and dimensional stability of the material after the treatment good, the temperature difference between the first gradient temperature and the second gradient temperature is further adjusted to 150-350°C, and the cooling rate between them is 0.1-50°C / min. When the temperature difference is less than 150°C or the cooling rate is less than 0.1°C / min, the precipitates precipitated in the first stage are coarse, which leads to the decrease of bending property and dimensional stability, and when the temperature difference is greater than 350°C or the cooling rate exceeds 50°C / min, it is difficult to generate new precipitates in the second stage. Therefore, by controlling the temperature, the required fine precipitates can be added in the second stage, the grain size and precipitation density of Ni-Si intermetallic compounds are adjusted, and good bending property and dimensional stability are realized. More preferably, after the gradient aging treatment, it is considered necessary to rapidly cool the material by water quenching to obtain a metastable phase segregation microstructure without discontinuous precipitates, which helps to improve the intracrystalline precipitation of fine second phase particles.

[0018] As preferred, the solid solution temperature of the solid solution quenching treatment is 800-950°C, and the solid solution time is 0.1-1h, which promotes the solid solution of the second phase particles after deformation to form a supersaturated solid solution, improves the aging hardening ability, fully performs the recrystallization of the above-mentioned product based on the matrix phase and the solid solution after cold rolling, adjusts the electrical conductivity to the appropriate range and improves the thermal stability, and the solid solution temperature is preferably above 800°C; based on the densification of the metal structure and the good bending property, the solid solution temperature is not more than 950°C. Preferably, the average cooling rate in the temperature range of 800-600°C during the quenching cooling process after the solid solution treatment is set to 110-150°C / s, thereby a large number of fine precipitates are generated in the grain, the growth of the precipitate particles is slow, and in the subsequent series of steps, the precipitation points suitable for dispersing a large number of fine Ni-Si precipitates can be obtained. If the cooling rate is too slow, the second phase particles during the cooling process are coarse, and the aging hardening ability is reduced. If the average cooling rate is too high, the precipitation points of the fine precipitates cannot be obtained.

[0019] As preferred, the process of the gradient low-temperature short-time heat treatment is as follows: first, a first-stage heat treatment is performed by heating to 150-200 DEG C at a heating rate of 25-35 DEG C / min and holding for 100-200 s, and then a second-stage heat treatment is performed by heating to 350-500 DEG C at the same heating rate as the first-stage heat treatment and holding for 5-600 s. After cold rolling and finish cold rolling, the large processing rate of the copper alloy leads to a serious decrease in plasticity and poor material formability; when a common single-stage low-temperature annealing heat treatment is used, the plasticity of the material is improved to a limited extent and the subsequent bending processability is poor; in the present application, the alloy after finish cold rolling is held at various temperature gradients, so as to ensure that the center and the outside of the alloy strip are at the same temperature and prevent surface cracks caused by too large temperature difference, and then gradient heating and holding are performed to remove the strain increased in the process of finish cold rolling, so as to obtain the final copper alloy product with a small intracrystalline strain rate.

[0020] As preferred, the final reduction rate Z of the finish cold rolling satisfies lg(Z)≤1.667+0.054×[Ni+Si]+0.03[Sn], wherein [Sn] and [Ni+Si] are the mass percentage contents of Sn, Ni+Si in the alloy, respectively. The finish cold rolling introduces more shear bands, which improves the stress relaxation resistance, and the elongated deformation structure in the rolling direction is divided by the introduced shear bands, which can inhibit grain growth and adjust the intracrystalline strain rate.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1. In the present application, Cu, Ni, Si and Sn are essential elements, and the distribution density of disc-shaped δ-Ni2Si precipitated phases with a particle size of 5-30 nm in the copper alloy is limited by further controlling the addition amount of alloying elements and the concentration distribution of Sn, so as to improve the deformation and rupture resistance caused by the outer layer tensile stress during bending process while ensuring the electrical conductivity of the alloy, and the excellent bending property and thermal stability are taken into account.

[0023] 2. The copper alloy obtained by alloying design of elements and process control has an electrical conductivity of more than 40% IACS, an average roughness Ra of the outer periphery surface after 90 DEG bending along the vertical rolling direction and R / t=0.5 is ≤4.0 μm, a thermal stress relaxation rate after exposure at 150 DEG C for 1000 h is ≤20%, a change value of bending deformation angle before and after heat treatment is ≤5 DEG, and no obvious cracks and damages occur on the surface after 3 cold-thermal cycles at a temperature of 25-300 DEG C. While maintaining good electrical conductivity, the bending processability and thermal stability are excellent, and the performance requirements of electronic and electrical components can be met. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below with reference to the embodiments.

[0025] Eleven examples and two comparative examples were prepared by the preparation method of the present application: melting casting → homogenization annealing → hot deformation → first cold rolling → annealing → second cold rolling → solid solution quenching treatment → third cold rolling → gradient aging treatment → fine cold rolling → gradient low temperature short time heat treatment.

[0026] (1) Melting casting: the alloy raw material was melted at 1150-1300℃, and then casted at a cooling speed of 0.1-100℃ / s at 950-1100℃;

[0027] (2) Homogenization annealing: homogenization heat treatment was carried out at a heating rate of 10-110℃ / s to 900-1000℃, and the holding time was 5min-5h;

[0028] (3) Hot deformation: plastic deformation was carried out after heating at 800-900℃ for 30min-2h, and the total deformation amount of the hot deformation was controlled to be 40-90%;

[0029] (4) First cold rolling: the rolling rate was 60% or more, intermediate annealing was carried out at 550-600℃ for 10-30s to remove the minimum amount of strain in the grains, and the second cold rolling was carried out to inhibit grain coarsening caused by strain crystal structure, wherein the total reduction of the first and second cold rolling was controlled to be more than 80%;

[0030] (5) Solid solution quenching treatment: the obtained product was subjected to solid solution heat treatment at 800-950℃ for 0.1-1h; the average cooling speed during quenching cooling at 800-600℃ was set to be in the range of 110-150℃ / s;

[0031] (6) Third cold rolling: the rolling rate was 5-50%, and the rolling speed was 100-150m / min;

[0032] (7) Gradient aging treatment: the temperature was held at the first gradient temperature of 500-600℃ for 5-12h, and then the temperature was decreased to the second gradient temperature of 200-350℃, and the holding time was 8-12h, the temperature difference between the two temperatures was 150-350℃, and the cooling rate was 0.1-50℃ / min;

[0033] (8) Fine cold rolling: the final reduction Z met the requirement of lg(Z)≤1.667+0.054×[Ni+Si]+0.03[Sn];

[0034] (9) Gradient low temperature short time heat treatment: the temperature in the furnace was increased to 150-200℃ at a heating rate of 25-35℃ / min, and then held for 100-200s, and then the temperature was increased to 350-500℃ at the same heating rate, and then held for 5-600s.

[0035] For each of the obtained embodiment and comparative example alloy samples of the present application, the following conditions were used for property evaluation, and the microstructure characteristics and performance test results are shown in Table 2. The chemical composition and preparation process of each embodiment and comparative example are shown in Table 1.

[0036] Electrical conductivity: tested according to GB / T 32791-2016 Copper and copper alloy - Electrical conductivity - Eddy current method.

[0037] Thermal stress relaxation rate: according to GB / T 39152-2020 Copper and copper alloy - Bending stress relaxation test method, sampling along the rolling direction, test temperature is 150℃, time is 1000h.

[0038] Bending processability: according to GB / T 232-2010 Metal materials - Bending test method, 90° bending test was carried out by a bending tester along the vertical rolling direction, the sample width is 10mm, length is 25mm. When the safe bending radius R / t is 0.5, the average roughness Ra of the bending outer periphery is measured. If the average roughness Ra is ≤4.0μm, it is judged as excellent bending, marked as “O”, if the average roughness Ra is >4.0μm, it is judged as poor bending, marked as “X”.

[0039] Microstructure: the concentration of Sn solid-solved in the grains at a position 1 / 8±5μm away from the plate thickness and 1 / 2±5μm away from the plate thickness direction perpendicular to the rolling direction of the sample was measured by a scanning electron microscope at a magnification of 50000 times, the concentration difference was calculated; the proportion of grain boundaries with a phase difference of 0° or more but not more than 1° and 15° or less was measured by EBSD observation, the intragranular strain rate was calculated; the size of precipitated phase was photographed and measured by a center dark field image, 10 fields of view were observed at 2000 times and 20000 times respectively, and the number of δ-Ni2Si with a size of 5-30nm per unit area ( / mm 2 ) in the field of view was calculated and determined.

[0040] Dimensional stability: the material before final heat treatment was bent within the range without bending fracture, and the bending deformation angle θ of the bending processed part was calculated. The safe bending radius R / t was selected as 0.5 as the bending condition, the material after heat treatment was bent under the same condition, and the bending deformation angle θ' was calculated. The absolute value of the change in bending deformation angle before and after heat treatment |θ'-θ| was calculated, and the value ≤5° was judged as excellent dimensional stability, marked as “O”, and the value >5° was judged as poor dimensional stability, marked as “X”.

[0041] Thermal shock resistance: using a cold and hot shock test chamber, heating and cooling were repeated at intervals of 30 seconds between 25 and 300°C, the heating time was 10 minutes each time, and the cycle test was performed 3 times. Whether the surface was damaged was finally observed, and the surface without cracks and damage was determined to be excellent in thermal shock resistance, marked as "O", and the surface with cracks or obvious damage was determined to be poor in thermal shock resistance, marked as "X".

[0042]

[0043]

Claims

1. A copper alloy for electronic and electric parts, characterized by comprising, in mass %, The alloy contains, in terms of mass percentage, 1 to 2.8 wt% of Ni, 0.2 to 0.8 wt% of Si, 0.2 to 1.2 wt% of Sn, and the remainder of Cu and inevitable impurities; the concentration difference between the Sn concentration in a surface layer region 1 / 8 of the plate thickness direction ± 5 μm from the surface of the alloy plate strip and the Sn concentration in a central region 1 / 2 of the plate thickness direction ± 5 μm from the surface of the alloy plate strip is 0.1 wt% or less; and in the microstructure of the alloy, disc-shaped δ-Ni2Si precipitated phases having a particle size of 5 to 30 nm exist in the parent phase at a distribution density of 10 4 × 10 2 8×10 6 2 mm-2.​ 2. The copper alloy for electronic / electric parts according to claim 1, characterized by The alloy further contains, in terms of mass percentage, 1wt% or less of at least one element selected from Fe, Mg, Mn, P, and Zn.

3. The copper alloy for electronic / electric parts according to claim 1, characterized by The intracrystalline strain rate η of the alloy is greater than 0.05% and less than 10%, wherein the intracrystalline strain rate η=A1 / A0×100%, A1 is the proportion of grain boundaries with a phase difference of 0° or more but not more than 1° between adjacent grains, and A0 is the proportion of grain boundaries with a phase difference of 15° or less between adjacent grains.

4. The copper alloy for electronic / electric parts according to claim 1, characterized by For the strip of the alloy, a 90° bending test is performed along the transverse direction of the rolling direction, and the average roughness Ra of the outer circumferential surface is 4.0 μm or less when the safe bending radius R / t is 0.

5.

5. The copper alloy for electronic / electric parts according to claim 1, characterized by The thermal stress relaxation rate of the strip of the alloy after exposure at 150℃ for 1000h is 20% or less, and the electrical conductivity is 40% IACS or more.

6. The copper alloy for electronic / electric parts according to claim 1, characterized by The absolute value of the change in bending deformation angle before and after heat treatment of the strip of the alloy is |θ'-θ|≤5°, wherein θ is the bending deformation angle before heat treatment, and θ' is the bending deformation angle after heat treatment; the strip of the alloy is subjected to 3 cold-heat cycles under temperature conditions of 25-300℃, and no obvious cracks or damage are observed on the surface.

7. The method of producing a copper alloy for an electronic part according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: melting and casting → homogenization annealing → hot deformation → primary cold rolling → annealing → secondary cold rolling → solid solution quenching treatment → tertiary cold rolling → gradient aging treatment → fine cold rolling → gradient low-temperature short-time heat treatment, wherein the first gradient temperature of the gradient aging treatment is 500-600℃, and the temperature is kept for 5-12h, then the temperature is lowered to the second gradient temperature of 200-350℃ at a cooling rate of 0.1-50℃ / min, and the temperature difference between the first gradient temperature and the second gradient temperature is 150-350℃, and the process of the gradient low-temperature short-time heat treatment is as follows: first, the temperature is raised to 150-200℃ at a heating rate of 25-35℃ / min, and the temperature is kept for 100-200s for the first stage heat treatment, then the temperature is raised to 350-500℃, and the temperature is kept for 5-600s for the second stage heat treatment, and the heating rate of the second stage heat treatment is the same as that of the first stage heat treatment.

8. The method of producing a copper alloy for electronic and electric parts according to claim 7, characterized by, The solid solution temperature of the solid solution quenching treatment is 800-950℃, the solid solution time is 0.1-1h, and the average cooling speed in the temperature range of 800-600℃ during quenching cooling is 110-150℃ / s.

9. The method of producing a copper alloy for electronic and electric parts according to claim 7, characterized by, The final reduction rate Z of the fine cold rolling satisfies the formula: lg(Z)≤1.667+0.054×[Ni+Si]+0.03[Sn], wherein [Sn] and [Ni+Si] are the mass percentage contents of Sn and Ni+Si in the alloy, respectively.

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