Copper alloy strip and preparation method thereof

Abstract

The invention provides a copper alloy strip and a preparation method thereof. The copper alloy strip is prepared from the following elements in percentage by mass: 2.0 to 4.0 percent of Ni element, 0.2 to 1.0 percent of Si element, 0.05 to 0.5 percent of Zr element, 0.05 to 1.0 percent of Al element, 0.05 to 0.5 percent of Mg element, 0.1 to 0.5 percent of Nb element and the balance of Cu element, the residual stress of the copper alloy strip is-50-50 MPa, and the high-temperature softening resistance temperature of the copper alloy strip is larger than or equal to 520 DEG C. By optimizing the alloy components and improving the process, the residual stress of the copper alloy strip can be further reduced and the high-temperature softening resistance of the copper alloy strip can be improved on the basis of not reducing the mechanical property and the electrical property of the copper alloy strip, and meanwhile, the copper alloy strip is promoted to form a good plate shape; therefore, the lead frame can be better applied to integrated circuit lead frames.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloys, and in particular to a copper alloy strip and a preparation method thereof. Background Art

[0002] Lead frame, as the chip carrier of integrated circuit, plays the role of a bridge connecting with external wires and is an important basic material in the electronic information industry. At present, etching lead frame materials have made great progress, but among the copper alloy materials used for integrated circuit lead frames, only the low-end Cu-Fe-P and Cu-Ni-Si alloy materials have been domestically produced in batches, while the high-end Cu-Ni-Si and Cu-Cr alloy materials still need to be imported.

[0003] In the processing and heat treatment of the lead frame, the use of hot and cold rolling processing and various heat treatment processes will cause certain residual stresses to be generated inside the copper material. The existence of residual stress causes the copper material to have different degrees of warping and deformation during the etching process. In addition, good high-temperature softening resistance is also required to improve the high-temperature performance of the lead frame material. At present, the traditional methods to reduce the residual stress in the production process of copper strip are mainly hood furnace annealing and air cushion furnace expansion annealing. Although the above processes can effectively reduce the residual stress of the copper strip, it will make the recrystallization ratio of the copper strip too high, the strength and hardness are insufficient, and the high-temperature softening resistance of the copper strip cannot be taken into account.

[0004] The prior art discloses the production of low residual stress copper alloys by various technical means, such as the Chinese patent application with the patent application publication number CN103540883A, which discloses that by applying a tensile stress of 100 to 280 MPa to the copper alloy wire during the aging treatment of the copper alloy, and applying tensile stress at the same time during the aging heat treatment of the copper alloy wire, the residual stress diffusion inside the wire tends to be uniform, thereby removing the residual stress inside the copper alloy wire to the maximum extent. However, this technology of applying tensile stress on the copper alloy wire is difficult to be suitable for all situations, and is less efficient when processing large coils of heavy wires. The Chinese patent application with the patent application publication number CN118218551A discloses that the production of copper and copper alloy low residual stress thin strips is achieved by controlling the roll crown, adjustment amount, bending roll force, front and rear tension, roll diameter difference, pass reduction rate during rolling of the rolling mill, the front and rear tension and elongation during bending and straightening before low-temperature annealing of the finished product, and the key process parameters of online annealing of the finished product in a high-tension low-temperature air cushion furnace. However, the control technology of this technology is relatively complicated, and the rolling parameters are often changed according to the copper material performance or thickness requirements during the rolling process of the rolling mill. If one of the parameters is changed, the other parameters must be adjusted to achieve the purpose of controlling the residual stress. The Chinese patent application with the patent application publication number CN115287495A discloses that by adding Nb elements to the C19400 alloy, by controlling the intermediate rolling, finished product rolling and stress relief annealing process, the recrystallization structure area in the microstructure of the copper alloy strip accounts for more than 90%, and the dislocation structure area accounts for less than 10%, and finally realizes the control of the residual stress of copper and copper alloys. However, this technology requires that the copper material reaches a recrystallization structure area of ​​more than 90%, and the residual stress is eliminated by recrystallization. However, too high a proportion of recrystallized structure will affect the final strength and hardness of the alloy, limiting the full play of the copper material performance.

[0005] Therefore, how to reduce the internal stress of copper alloys and improve their resistance to high-temperature softening without reducing their basic properties such as mechanical and electrical properties still needs to be further resolved. Summary of the invention

[0006] The main purpose of the present invention is to provide a copper alloy strip and a preparation method thereof, so as to solve the problems in the prior art that when reducing the residual stress of the copper alloy, the copper alloy strip cannot have both excellent mechanical properties and electrical properties and the high temperature softening resistance is insufficiently improved.

[0007] In order to achieve the above-mentioned object, according to one aspect of the present invention, a copper alloy strip is provided, which comprises the following elements, in mass percentage: 2.0-4.0% Ni element, 0.3-1.0% Si element, 0.05-0.5% Zr element, 0.05-1.0% Al element, 0.05-0.5% Mg element and 0.1-0.5% Nb element, and the balance is Cu element; the residual stress of the copper alloy strip is -50-50MPa, and the high temperature softening temperature of the copper alloy strip is ≥520°C.

[0008] Furthermore, the copper alloy strip comprises the following elements, in percentage by mass: 2.5-3.5% of Ni, 0.5-1.0% of Si, 0.05-0.5% of Zr, 0.2-1.0% of Al, 0.1-0.5% of Mg and 0.1-0.4% of Nb, with the remainder being Cu.

[0009] Furthermore, the mass ratio of the Ni element to the Si element is 3.2 to 4.2:1, and the mass ratio of the Al element to the Zr element is 0.5 to 1.5:1.

[0010] Furthermore, the average grain size of the copper alloy strip is 2-15 μm, and / or the average size of the second phase in the copper alloy strip is 1-100 nm; the thickness of the copper alloy strip is 0.1-0.3 mm.

[0011] According to another aspect of the present invention, a method for preparing the above-mentioned copper alloy strip is provided, and the preparation method comprises: step S1, sequentially performing batching, smelting, casting, hot rolling, solutionizing, primary cold rolling, primary aging, secondary cold rolling and secondary aging on the raw materials corresponding to the copper alloy to obtain a copper strip; step S2, hot pressing the copper strip to obtain a copper alloy strip.

[0012] Furthermore, in the above step S2, the pressure of the hot pressing treatment is 50-300 MPa, and / or the temperature of the hot pressing treatment is 100-280° C., and / or the holding time of the hot pressing treatment is 30-180 min.

[0013] Furthermore, in the above step S1, the processing rate of the primary cold rolling is 70-90%; and / or the temperature of the primary aging is 450-500°C.

[0014] Furthermore, in the above step S1, the processing rate of the secondary cold rolling is 70-95%; and / or the temperature of the secondary aging is 360-400°C.

[0015] Furthermore, in the above step S1, the holding temperature of smelting is 1250-1300°C, and / or the casting temperature is 1200-1250°C.

[0016] Furthermore, the above-mentioned step S1 includes, in sequence, batching, smelting and casting the raw materials corresponding to the copper alloy to obtain an ingot; hot rolling the ingot after keeping it at 900-960°C for 2-5h, and / or the number of hot rolling passes is 9-11 times, and / or the final rolling temperature of the hot rolling is 700-850°C.

[0017] By applying the technical solution of the present invention, the present application can further reduce the residual stress of the copper alloy strip and improve the high temperature softening resistance of the copper alloy strip without reducing the mechanical properties and electrical properties of the copper alloy strip by optimizing the alloy composition. Specifically, adding Zr and Al elements to the alloy can form Al with good heat resistance. 3 Zr precipitates phase, thereby effectively improving the high temperature stability of the copper alloy strip, and then improving the high temperature softening resistance of the copper alloy strip. When Mg is added to the copper-nickel-silicon alloy, Mg can be segregated in the copper matrix in the form of "Mg atomic gas clusters", thereby increasing the density of the precipitated phase during the aging process. At the same time, Mg atoms have a dragging effect on dislocation movement, which can effectively hinder dislocation movement, thereby improving the high temperature softening resistance of the copper alloy strip. The added Nb element can be basically immiscible with the Cu element in a balanced state, and exists in the copper matrix as a single phase. At the same time, since the Nb element is a high melting point element, it helps to inhibit the recrystallization of the copper alloy strip at high temperature, which can significantly improve the thermal stability of the copper alloy strip. The added Si element and Ni element can form a NiSi phase, thereby ensuring the basic strength and conductivity of the copper alloy strip. At the same time, the residual stress of the copper alloy strip of the present application is controlled within -50 to 50MPa, which helps to further improve the high temperature softening resistance of the copper alloy strip. Copper alloy strips in a low stress state can reduce the hardness drop caused by stress release during the recovery and recrystallization process of the copper alloy strips at high temperatures, thereby having better resistance to high temperature softening and being better applicable to integrated circuit lead frames. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0019] As analyzed in the background technology of this application, there is a problem in the prior art that when reducing the residual stress of copper alloy, it is impossible to make the copper alloy strip have both excellent mechanical properties and electrical properties and the high-temperature softening resistance is insufficiently improved. In order to solve the above problems, this application provides a copper alloy strip and a preparation method thereof.

[0020] In a typical embodiment of the present application, a copper alloy strip is provided, which includes the following elements, in mass percentage: 2.0-4.0% Ni element, 0.3-1.0% Si element, 0.05-0.5% Zr element, 0.05-1.0% Al element, 0.05-0.5% Mg element and 0.1-0.5% Nb element, and the balance is Cu element; the residual stress of the copper alloy strip is -50-50MPa, and the high temperature softening temperature of the copper alloy strip is ≥520°C.

[0021] The present invention optimizes the alloy composition, and can further reduce the residual stress of the copper alloy strip and improve the high temperature softening resistance of the copper alloy strip without reducing the mechanical properties and electrical properties of the copper alloy strip. Specifically, adding Zr and Al elements to the alloy can form Al with good heat resistance. 3 Zr precipitates phase, thereby effectively improving the high temperature stability of the copper alloy strip, and then improving the high temperature softening resistance of the copper alloy strip. When Mg is added to the copper-nickel-silicon alloy, Mg can be segregated in the copper matrix in the form of "Mg atomic gas clusters", thereby increasing the density of the precipitated phase during the aging process. At the same time, Mg atoms have a dragging effect on dislocation movement, which can effectively hinder dislocation movement, thereby improving the high temperature softening resistance of the copper alloy strip. The added Nb element can be basically immiscible with the Cu element in a balanced state, and exists in the copper matrix as a single phase. At the same time, since the Nb element is a high melting point element, it helps to inhibit the recrystallization of the copper alloy strip at high temperature, which can significantly improve the thermal stability of the copper alloy strip. The added Si element and Ni element can form a NiSi phase, thereby ensuring the basic strength and conductivity of the copper alloy strip. At the same time, the residual stress of the copper alloy strip of the present application is controlled within -50 to 50MPa, which helps to further improve the high temperature softening resistance of the copper alloy strip. Copper alloy strips in a low stress state can reduce the hardness drop caused by stress release during the recovery and recrystallization process of the copper alloy strips at high temperatures, thereby having better resistance to high temperature softening and being better applicable to integrated circuit lead frames.

[0022] In order to further reduce the residual stress of the copper alloy strip and improve the high temperature softening resistance of the copper alloy strip, in one embodiment of the present application, the copper alloy strip includes the following elements, by mass percentage: 2.5-3.5% Ni element, 0.5-1.0% Si element, 0.05-0.5% Zr element, 0.2-1.0% Al element, 0.1-0.5% Mg element and 0.1-0.4% Nb element, and the balance is Cu element.

[0023] In one embodiment of the present application, the mass ratio of the Ni element to the Si element is 3.2-4.2:1; and / or the mass ratio of the Al element to the Zr element is 0.5-1.5:1.

[0024] Preferably, the mass ratio of Si element to Ni element is controlled within the above range, which helps to enhance the strengthening effect of Si element and Ni element, thereby helping to form a pure matrix structure and a dispersed second phase, thereby improving the high conductivity of the copper alloy strip. Preferably, the mass ratio of Zr element to Al element is controlled within the above range, which helps to improve the synergistic effect of Zr element and Al element and the mutual synergistic effect of zirconium aluminum intermetallic compound and nickel silicon intermetallic compound, inhibiting the recrystallization and grain growth of the copper alloy strip at high temperature, thereby further improving the high temperature stability of the copper alloy strip, thereby improving the high temperature softening resistance of the copper alloy strip.

[0025] In addition, alloys with both of the above intermetallic compounds have better strengthening effects in subsequent processing than alloys with a single intermetallic compound. This is due to the synergistic effect of the zirconium-aluminum intermetallic compound and the nickel-silicon intermetallic compound, which help to promote each other's dispersed distribution. The dispersed precipitate phase can leave more immobile dislocations when dislocations bypass the precipitate phase particles during the subsequent cold deformation process, thereby promoting the alloy to have a better strengthening effect.

[0026] In one embodiment of the present application, the average grain size of the copper alloy strip is 2-15 μm, and / or the average grain size of the second phase in the copper alloy strip is 1-100 μm; the thickness of the copper alloy strip is 0.1-0.3 mm.

[0027] It is preferred that the average grain size of the copper alloy strip and the average grain size of the second phase in the copper alloy strip be controlled within the above range, and the grain size is uniform, which helps to improve the mechanical properties and electrical conductivity, and helps to further improve the high temperature stability of the copper alloy strip, thereby improving the high temperature softening resistance of the copper alloy strip. It is preferred that the thickness of the copper alloy strip be within the above range, which helps to better apply to integrated circuit lead frames.

[0028] In another typical embodiment of the present application, a method for preparing the above-mentioned copper alloy strip is provided, and the preparation method comprises: step S1, sequentially performing batching, smelting, casting, hot rolling, solutionizing, primary cold rolling, primary aging, secondary cold rolling and secondary aging on the raw materials corresponding to the copper alloy to obtain a copper strip; step S2, hot pressing the copper strip to obtain a copper alloy strip.

[0029] In the preparation method of the present application, the residual stress of the copper strip can be fully released by performing low-temperature hot pressing on the copper strip on a hot press, thereby obtaining an aging state copper strip with low residual stress. Since most of the stress unevenness in the copper strip comes from process stages such as hot rolling and cold rolling, the present application performs low-temperature hot pressing on the copper strip, which can more specifically reduce the residual stress of the copper strip. In addition, the copper alloy strip with low residual stress will not produce a stress release effect due to the effect of temperature in a high temperature state, thereby reducing the hardness reduction of the copper alloy strip at high temperature and causing the copper alloy strip to reduce its high temperature softening resistance. Therefore, the preparation method of the present invention has a simple control process, can effectively reduce the internal stress of the copper alloy strip and improve the high temperature softening resistance at the same time, and takes into account excellent mechanical properties and electrical properties, so that the above-mentioned copper alloy strip can be better applied to integrated circuit lead frames.

[0030] In one embodiment of the present application, in the above step S2, the pressure of the hot pressing treatment is 50-300 MPa, and / or the temperature of the hot pressing treatment is 100-280°C, and / or the holding time of the hot pressing treatment is 30-180 min.

[0031] It is preferred to control the pressure, temperature and holding time of the hot pressing treatment within the above range, which helps to further produce thermal effects and stress release effects, reduce defects such as movable dislocations inside the copper alloy, thereby further fully releasing the residual stress inside the copper strip, and promoting the copper alloy strip to form a good plate shape. The reduction of residual stress slows down the reduction in hardness of the copper strip due to recovery and recrystallization under high-temperature use conditions, thereby simultaneously improving the high-temperature softening performance of the copper strip. In addition, hot pressing treatment is performed in a hot pressing device, and graphite paper is placed on the upper and lower surfaces of the copper strip, which helps to ensure lubrication during the hot pressing process and protect the surface of the copper strip.

[0032] In one embodiment of the present application, in the above step S1, the processing rate of the first cold rolling is 70-90%; and / or the temperature of the first aging is 450-500°C; the processing rate of the second cold rolling is 70-95%; and / or the temperature of the second aging is 360-400°C.

[0033] It is preferred to control the processing rates of the primary cold rolling and the secondary cold rolling and the temperatures of the primary aging and the secondary aging within the above ranges, which helps to refine the grains of the alloy, thereby improving the strength and hardness of the alloy.

[0034] In one embodiment of the present application, in the above step S1, the holding temperature of smelting is 1250-1300°C, and / or the casting temperature is 1200-1250°C.

[0035] It is preferred to control the holding temperature of the smelting within the above range, which helps to better dissolve and evenly distribute the above copper alloy raw materials, thereby ensuring uniform alloy composition. It is preferred to control the casting temperature within the above range, which helps to prepare high-quality ingots.

[0036] In one embodiment of the present application, the above-mentioned step S1 includes, in sequence, batching, smelting and casting the raw materials corresponding to the copper alloy to obtain an ingot; hot rolling the ingot after keeping it at 900-960°C for 2-5 hours, and / or the number of hot rolling passes is 9-11 times, and / or the final rolling temperature of the hot rolling is 700-850°C.

[0037] It is preferred to adopt the above hot rolling method and further control the hot rolling number and the final rolling temperature within the above range, which is helpful to control the grain size and uniformity of the alloy, thereby improving the strength and toughness of the copper alloy strip. In addition, the above hot rolling process helps the coarse precipitated phase existing in the ingot to be dissolved into the matrix again, thereby achieving the purpose of homogenization. At the same time, in order to minimize the precipitation of phase particles after hot rolling, the final rolling temperature is controlled at above 700°C.

[0038] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0039] Example 1

[0040] Ingredients: In terms of mass percentage, the copper alloy raw material is prepared according to the following components: 2.0% Ni element, 0.8% Si element, 0.05% Zr element, 0.55% Al element, 0.05% Mg element, 0.3% Nb element and the balance Cu element. Specifically, standard electrolytic copper, nickel block, silicon block, copper-zirconium master alloy, copper-magnesium master alloy and pure aluminum are weighed.

[0041] Melting and casting: After the above ingredients are baked, first add the electrolytic copper and nickel blocks into a vacuum melting furnace for melting, draw the vacuum to 0.8Pa, then heat up and melt, use a low power of 50KW for heating, and keep warm when the melting temperature reaches 1250℃, then add the remaining raw materials, keep warm for 5 minutes, and cast at 1200℃ to obtain an ingot.

[0042] Hot rolling and solution treatment: After the copper ingot is sawed, it is kept at 900℃ for 2h and then hot rolled. The heated copper ingot is hot rolled back and forth 9 times by a double-roll hot rolling mill, and the final rolling temperature is kept at 700℃. The thickness of the strip after hot rolling is 14.5mm, and then it is water quenched and cooled to remove the surface oxide scale.

[0043] Cold rolling and heat treatment: The solution-solution strip is cold rolled once on a cold rolling mill to about 3 mm and then aged, and then cold rolled twice to 0.3 mm and then aged to obtain a copper strip, wherein the processing rate of the first cold rolling is 80%, the temperature of the first aging is 450°C, the processing rate of the second cold rolling is 90%, and the temperature of the second aging is 360°C.

[0044] Hot pressing treatment: The copper strip was cut into about 210 mm × 300 mm and then hot pressed in a hot pressing device. A pressure of 50 MPa was applied and the temperature was adjusted to 100° C. and kept warm for 30 minutes to obtain a copper alloy strip.

[0045] Example 2

[0046] Ingredients: In terms of mass percentage, the copper alloy raw material is prepared according to the following components: 3.0% Ni element, 0.3% Si element, 0.2% Zr element, 0.2% Al element, 0.3% Mg element, 0.1% Nb element and the balance Cu element. Specifically, standard electrolytic copper, nickel block, silicon block, copper-zirconium master alloy, copper-magnesium master alloy and pure aluminum are weighed.

[0047] Melting and casting: After the above ingredients are baked, first add the electrolytic copper and nickel blocks into the vacuum melting furnace for melting, draw the vacuum to 0.8Pa, then heat up and melt, use 50KW low power heating, when the melting temperature reaches 1280℃, keep warm, then add the remaining raw materials, keep warm for 5 minutes, and cast at 1220℃ to obtain an ingot.

[0048] Hot rolling and solution treatment: After the copper ingot is sawed, it is kept at 930℃ for 4h and then hot rolled. The heated copper ingot is hot rolled back and forth 10 times by a double-roll hot rolling mill, and the final rolling temperature is kept at 750℃. The thickness of the strip after hot rolling is 14.5mm, and then it is water quenched and cooled to remove the surface oxide scale.

[0049] Cold rolling and heat treatment: the solution-solutionized strip is cold rolled once on a cold rolling mill to about 3 mm and then aged, and then cold rolled twice to 0.3 mm and then aged to obtain a copper strip, wherein the processing rate of the first cold rolling is 80%, the temperature of the first aging is 480°C, the processing rate of the second cold rolling is 90%, and the temperature of the second aging is 380°C.

[0050] Hot pressing treatment: The copper strip was cut into about 210 mm × 300 mm and then hot pressed in a hot pressing device. A pressure of 200 MPa was applied and the temperature was adjusted to 200° C. and kept warm for 100 min to obtain a copper alloy strip.

[0051] Example 3

[0052] Ingredients: In terms of mass percentage, the copper alloy raw material is prepared according to the following components: 4.0% Ni element, 1% Si element, 0.5% Zr element, 0.05% Al element, 0.5% Mg element, 0.5% Nb element and the balance Cu element. Specifically, standard electrolytic copper, nickel block, silicon block, copper-zirconium master alloy, copper-magnesium master alloy and pure aluminum are weighed.

[0053] Melting and casting: After the above ingredients are baked, first add the electrolytic copper and nickel blocks into a vacuum melting furnace for melting, draw the vacuum to 0.8Pa, then heat up and melt, use a low power of 50KW for heating, and keep warm when the melting temperature reaches 1300℃, then add the remaining raw materials, keep warm for 5 minutes, and cast at 1250℃ to obtain an ingot.

[0054] Hot rolling and solution treatment: After the copper ingot is sawed, it is kept at 960℃ for 5h and then hot rolled. The heated copper ingot is hot rolled back and forth 11 times by a double-roll hot rolling mill, and the final rolling temperature is maintained at 850℃. The thickness of the strip after hot rolling is 14.5mm, and then it is water quenched and cooled to remove the surface oxide scale.

[0055] Cold rolling and heat treatment: the solution-solutionized strip is cold rolled once on a cold rolling mill to about 3 mm and then aged, and then cold rolled twice to 0.3 mm and then aged to obtain a copper strip, wherein the processing rate of the first cold rolling is 80%, the temperature of the first aging is 500°C, the processing rate of the second cold rolling is 90%, and the temperature of the second aging is 400°C.

[0056] Hot pressing treatment: The copper strip was cut into about 210 mm × 300 mm and then hot pressed in a hot pressing device. A pressure of 300 MPa was applied and the temperature was adjusted to 280° C. and kept warm for 180 min to obtain a copper alloy strip.

[0057] Example 4

[0058] The difference from Example 1 is that the total mass content of Ni element and Si element is 2.8%, the mass ratio of Ni element to Si element is 3.2:1, and finally a copper alloy strip is obtained.

[0059] Example 5

[0060] The difference from Example 1 is that the total mass content of Ni element and Si element is 2.8%, the mass ratio of Ni element to Si element is 4.2:1, and finally a copper alloy strip is obtained.

[0061] Example 6

[0062] The difference from Example 1 is that the total mass content of Ni element and Si element is 2.8%, the mass ratio of Ni element to Si element is 3:1, and finally a copper alloy strip is obtained.

[0063] Example 7

[0064] The difference from Example 1 is that the total mass content of Al element and Zr element is 0.6%, the mass ratio of Al element to Zr element is 0.5:1, and finally a copper alloy strip is obtained.

[0065] Example 8

[0066] The difference from Example 1 is that the total mass content of Al element and Zr element is 0.6%, the mass ratio of Al element to Zr element is 1.5:1, and finally a copper alloy strip is obtained.

[0067] Example 9

[0068] The difference from Example 1 is that the total mass content of Al element and Zr element is 0.6%, the mass ratio of Al element to Zr element is 2:1, and finally a copper alloy strip is obtained.

[0069] Example 10

[0070] The difference from Example 1 is that the pressure of the hot pressing treatment is 300 MPa, the temperature of the hot pressing treatment is 280° C., and the holding time of the hot pressing treatment is 180 min, thereby obtaining a copper alloy strip.

[0071] Embodiment 11

[0072] The difference from Example 1 is that the pressure of the hot pressing treatment is 30 MPa, the temperature of the hot pressing treatment is 50° C., and the holding time of the hot pressing treatment is 10 min, thereby obtaining a copper alloy strip.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that the copper strip is not subjected to hot pressing treatment to obtain a copper alloy strip.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that the ingredients are: in terms of mass percentage, the copper alloy raw material is formulated according to 4.5% Ni element, 1.5% Si element, 0.02% Zr element, 0.01% Al element, 0.7% Mg element and the balance Cu element, and finally a copper alloy strip is obtained.

[0077] Comparative Example 3

[0078] The difference from Comparative Example 2 is that the copper strip is not subjected to hot pressing treatment to obtain a copper alloy strip.

[0079] Test Method

[0080] Test of average grain size and average size of second phase: The test was carried out in accordance with YS / T347-2020 "Method for Determination of Average Grain Size of Copper and Copper Alloys". The average size of the second phase was obtained using Image Pro Plus (IPP) software, and the size was determined based on twenty randomly selected second phase organization diagrams.

[0081] Strength test: Test in accordance with GB / T 228.1-2021 Tensile test of metal materials.

[0082] Conductivity test: Test in accordance with GB / T 32791-2016 Eddy current test method for electrical conductivity of copper and copper alloys.

[0083] Residual stress test: Tested in accordance with the X-ray diffraction method of GB / T 7704-2008.

[0084] Anti-softening performance test: measured in accordance with the test method specified in the national standard "GB / T 33370-2016 Determination of softening temperature of copper and copper alloys".

[0085] The copper alloy strips of the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0090] The present invention optimizes the alloy composition, and can further reduce the residual stress of the copper alloy strip and improve the high temperature softening resistance of the copper alloy strip without reducing the mechanical properties and electrical properties of the copper alloy strip. Specifically, adding Zr and Al elements to the alloy can form Al with good heat resistance. 3Zr precipitates phase, thereby effectively improving the high temperature stability of the copper alloy strip, and then improving the high temperature softening resistance of the copper alloy strip. When Mg is added to the copper-nickel-silicon alloy, Mg can be segregated in the copper matrix in the form of "Mg atomic gas clusters", thereby increasing the density of the precipitated phase during the aging process. At the same time, Mg atoms have a dragging effect on dislocation movement, which can effectively hinder dislocation movement, thereby improving the high temperature softening resistance of the copper alloy strip. The added Nb element can be basically immiscible with the Cu element in a balanced state, and exists in the copper matrix as a single phase. At the same time, since the Nb element is a high melting point element, it helps to inhibit the recrystallization of the copper alloy strip at high temperature, which can significantly improve the thermal stability of the copper alloy strip. The added Si element and Ni element can form a NiSi phase, thereby ensuring the basic strength and conductivity of the copper alloy strip. At the same time, the residual stress of the copper alloy strip of the present application is controlled within -50 to 50MPa, which helps to further improve the high temperature softening resistance of the copper alloy strip. Copper alloy strips in a low stress state can reduce the hardness drop caused by stress release during the recovery and recrystallization process of the copper alloy strips at high temperatures, thereby having better resistance to high temperature softening and being better applicable to integrated circuit lead frames.

[0091] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A copper alloy strip, characterized in that: The copper alloy strip comprises the following elements in percentage by mass: 2.0-4.0% Ni, 0.3-1.0% Si, 0.05-0.5% Zr, 0.05-1.0% Al element, 0.05-0.5% Mg element, 0.1-0.5% Nb element, and the balance is Cu element; The residual stress of the copper alloy strip is -50 to 50 MPa, and the high temperature softening temperature of the copper alloy strip is ≥520°C.

2. The copper alloy strip according to claim 1, characterized in that: The copper alloy strip comprises the following elements in percentage by mass: 2.5-3.5% of the Ni element, 0.5-1.0% of the Si element, 0.05-0.5% of the Zr element, 0.2-1.0% of the Al element, 0.1-0.5% of the Mg element, 0.1-0.4% of the Nb element, and the balance is the Cu element.

3. The copper alloy strip according to claim 1 or 2, characterized in that: The mass ratio of the Ni element to the Si element is 3.2-4.2:1, and the mass ratio of the Al element to the Zr element is 0.5-1.5:

1.

4. The copper alloy strip according to any one of claims 1 to 3, characterized in that: The average grain size of the copper alloy strip is 2-15 μm, and / or the average size of the second phase in the copper alloy strip is 1-100 nm; the thickness of the copper alloy strip is 0.1-0.3 mm.

5. A method for preparing the copper alloy strip according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, subjecting raw materials corresponding to the copper alloy to batching, smelting, casting, hot rolling, solutionizing, primary cold rolling, primary aging, secondary cold rolling and secondary aging in sequence to obtain a copper strip; Step S2, hot pressing the copper strip to obtain a copper alloy strip.

6. The preparation method according to claim 5, characterized in that: In the step S2, the pressure of the hot pressing treatment is 50 to 300 MPa, and / or the temperature of the hot pressing treatment is 100 to 280° C., and / or the holding time of the hot pressing treatment is 30 to 180 min.

7. The preparation method according to claim 5 or 6, characterized in that: In the step S1, the processing rate of the primary cold rolling is 70-90%; and / or the temperature of the primary aging is 450-500°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In the step S1, the processing rate of the secondary cold rolling is 70-95%; and / or the temperature of the secondary aging is 360-400°C.

9. The preparation method according to any one of claims 5 to 8, characterized in that: In the step S1, the holding temperature of the smelting is 1250-1300°C, and / or the casting temperature is 1200-1250°C.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The step S1 comprises: preparing, smelting and casting the raw materials corresponding to the copper alloy in sequence to obtain an ingot; hot rolling the ingot after keeping it at 900-960°C for 2-5h, and / or the hot rolling is performed 9-11 times, and / or the final rolling temperature of the hot rolling is 700-850°C.

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