High-hardness and high-softening-resistance Cu-Fe-P alloy strip and preparation method thereof

Abstract

The invention relates to a high-hardness and high-softening-resistance Cu-Fe-P alloy strip and a preparation method thereof.The method comprises the following steps that under the protective atmosphere, high-temperature aging treatment is conducted on Cu-Fe-P alloy base metal; then, large-deformation cold rolling with the total deformation being 60%-70% is carried out; and finally, finished product rolling is conducted, and the copper alloy strip with the target thickness is obtained. According to the alloy strip prepared through the method, the Vickers hardness can reach 170 or above, the tensile strength is larger than or equal to 580 MPa, under the condition of 470 DEG C / 3 min, the Vickers hardness stably reaches 90% or above of the original hardness, the comprehensive performance is remarkably superior to that of a traditional technology and a similar advanced technical scheme, and the harsh requirement for the comprehensive performance of a copper alloy lead frame material in the electronic information industry can be met.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of non-ferrous metal calendering, and particularly relates to a Cu-Fe-P alloy strip with high hardness and high softening resistance and a preparation method thereof. BACKGROUND

[0002] Lead frame materials are widely used in the electronic information industry, including 5G communication, Internet of Things intelligence, mobile phone intelligence, etc. Copper alloys are increasingly becoming indispensable key materials for integrated circuits due to their good electrical and thermal conductivity and high strength. Copper alloy lead frame materials, as carriers of integrated circuit chips, play a role in electrical conduction and heat dissipation, and are key components of integrated circuits. The performance improvement of integrated circuits puts higher requirements on the comprehensive performance of copper alloy lead frame materials.

[0003] The mechanical properties and high-temperature softening resistance of lead frame materials are one of the key performance indicators, and are directly related to the structural stability, electrical connection reliability and heat dissipation efficiency of semiconductor packages in welding and long-term high-temperature working environments. Therefore, improving the high-temperature softening resistance of the material can further improve the applicability of the alloy terminal product. The performance of the current Cu-Fe-P alloy lead frame material generally meets the performance indicators in the standard GB / T20254.1-2015 "Copper and Copper Alloy Strip for Lead Frame": HV≥145, and the high-temperature softening resistance is 470℃, and after 3min treatment, the Vickers hardness should be not less than 80% of the original hardness. This indicator can meet the requirements of traditional packaging processes, but it is difficult to adapt to the trend of integrated circuits developing towards high power, high density and miniaturization. The application can effectively improve the hardness and high-temperature softening resistance of the Cu-Fe-P alloy material through reasonable design of a processing method without reducing other properties. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides a Cu-Fe-P alloy strip with high hardness and high softening resistance and a preparation method thereof. Through alloy composition control and two-step rolling + aging process during material cold deformation, the second phase is fully analyzed and high-density dislocations, deformation twins and nano precipitates are formed, so as to improve the mechanical properties of the alloy, especially the hardness and high-temperature softening resistance. Without reducing other properties, the strength and high-temperature softening resistance of the material are improved, so as to meet the requirements of the electronic information industry on the comprehensive performance of copper alloy lead frame materials.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is as follows: a preparation method of a Cu-Fe-P alloy strip with high hardness and high softening resistance, comprising the following steps: (1) high temperature aging: the Cu-Fe-P alloy base material is aged at 480-550℃ for 7-15 hours in a protective atmosphere, so that the Fe and P elements are fully analyzed to form a strengthening phase; (2) large deformation cold rolling: the base material treated in step (1) is subjected to multi-pass large deformation cold rolling, with a total deformation of 60%-70%; (3) step aging: the strip after step (2) cold rolling is first aged at 300-350℃ for 4-8 hours, then the temperature is raised to 440-460℃ for 3-6 hours, and then the furnace is discharged, and a protective gas is used during aging; (4) finished product rolling: the strip after step (3) treatment is cold rolled, with a total deformation of 60%-70%, to obtain a copper alloy strip with a target thickness.

[0006] Further, the Cu-Fe-P alloy base material composition includes, by weight percentage: Fe: 2.3-2.5%; P: 0.07-0.09%; Zn: 0.05-0.20%; Sn: 0.01-0.04%; Mg: 0.02-0.09%; Ni: 0.005-0.025%; the balance is copper and unavoidable impurities.

[0007] Further, the thickness of the Cu-Fe-P alloy base material is 1.0-2.0mm.

[0008] Further, the Cu-Fe-P alloy base material is made of Cu-Fe-P alloy ingot by heating, hot rolling, quenching and cold working.

[0009] Further, the Cu-Fe-P alloy base material in step (1) is subjected to high temperature aging treatment in a bell furnace.

[0010] Further, the Cu-Fe-P alloy base material in step (3) is subjected to step aging treatment in a bell furnace.

[0011] The second technical solution proposed by the application is a high hardness and high softening resistance Cu-Fe-P alloy strip prepared by the above preparation method.

[0012] Further, the prepared high hardness and high softening resistance Cu-Fe-P alloy strip has a Vickers hardness HV≥170, a tensile strength≥580 MPa, and after 470℃ / 3min treatment, the high temperature softening hardness is not less than 90% of the original hardness.

[0013] The technical principles and beneficial effects of the present application are: 1. The present application forms high-density dislocations and deformation twins through large-deformation cold processing and finished product rolling cold processing; high-temperature aging and combined with step aging, Fe and P are analyzed to form Fe2P, Fe3P and other nano precipitates in the form of second phase, and Mg and P form Mg3P2 in the form of compound; the mixed structure of high-density dislocations, deformation twins, nano precipitates and compounds formed by the preparation process can effectively improve the strength of the material and improve the mechanical properties of the alloy, especially the hardness and high-temperature softening resistance.

[0014] 2. The current Cu-Fe-P alloy lead frame material has a general performance of HV>145, and after 470℃ / 3min heat treatment, the hardness is not less than 80% of the original hardness. After the above preparation process, the hardness HV can reach more than 170, and the softening resistance is stable at more than 90% of the original hardness under the condition of 470℃ / 3min, which can effectively expand the applicability of downstream terminal products.

[0015] 3. The method of the present application realizes performance improvement of the product through component control and the above processing process, reduces the dependence of the current lead frame material on high-end equipment through high-temperature solid solution + aging strengthening mode, and is convenient for popularization and use. DETAILED DESCRIPTION

[0016] The present application will be further described in detail below in combination with examples, but it is not as a basis for any limitation on the invention.

[0017] The present application takes the mother material of a Cu-Fe-P alloy ingot after conventional processing as the test raw material, and the conventional process includes ingot-stepping furnace heating-hot rolling-quenching-cold rolling, and the obtained mother material thickness can be 1.0-2.0mm, and then high-temperature aging-large-deformation cold rolling-step aging-finished product rolling are carried out to obtain the high-hardness high-softening-resistance Cu-Fe-P alloy strip product of the present application.

[0018] The alloy composition of the Cu-Fe-P alloy ingot includes, by weight percentage: Fe: 2.3-2.5%; P: 0.07-0.09%; Zn: 0.05-0.20%; Sn: 0.01-0.04%; Mg: 0.02-0.09%; Ni: 0.005-0.025%; and the balance is copper and unavoidable impurities.

[0019] The preparation process will be described in detail below in different examples. Examples 1-4 are descriptions of the preparation process of the present application, and Comparative Examples 1-4 are comparative tests from different angles to demonstrate the necessity of the preparation process of the present application.

[0020] Example 1 In this embodiment, the base material with a thickness of 1.5 mm obtained through ingot casting-step furnace heating-hot rolling-quenching-cold working, etc. is subjected to high-temperature aging-large deformation cold rolling-staged aging-finished product rolling, and the specific process steps are as follows: Step one, high-temperature aging: aging treatment is performed using a bell furnace at 550°C, and the material is kept in a protective atmosphere (N2+H2) for 8 hours; Step two, large deformation cold rolling: the surface of the material after high-temperature aging is cleaned, and then large processing rate rolling is performed, with a total processing rate of 66.7%, to obtain a 0.5 mm thick strip; Step three, staged aging: the 0.5 mm thick strip is placed in a bell furnace and kept at 340°C for 5 hours, and then the temperature is raised to 450°C for 4 hours before being taken out of the furnace. A protective atmosphere (N2+H2) is used during the holding period; Step four, finished product rolling: the 0.5 mm thick strip is rolled to 0.203 mm, with a processing rate of 59.4%.

[0021] Product performance: after the above production process, the 0.203 mm copper strip has a hardness of HV=175 and a tensile strength of 590 MPa. After treatment at 470°C for 3 minutes, its Vickers hardness is 161, and the high-temperature softening hardness reaches 92% of the original hardness.

[0022] Example 2 In this embodiment, the base material with a thickness of 1.2 mm obtained through ingot casting-step furnace heating-hot rolling-quenching-cold working, etc. is subjected to high-temperature aging-large deformation cold rolling-staged aging-finished product rolling, and the specific process steps are as follows: Step one, high-temperature aging: aging treatment is performed using a bell furnace at 480°C, and the material is kept in a protective atmosphere (N2+H2) for 15 hours; Step two, large deformation cold rolling: the surface of the material after high-temperature aging is cleaned, and then large processing rate rolling is performed, with a total processing rate of 66.7%, to obtain a 0.4 mm thick strip; Step three, staged aging: the 0.4 mm thick strip is placed in a bell furnace and kept at 350°C for 4 hours, and then the temperature is raised to 460°C for 4 hours before being taken out of the furnace. A protective atmosphere (N2+H2) is used during the holding period; Step four, finished product rolling: the 0.4 mm thick strip is rolled to 0.127 mm, with a processing rate of 68.25%.

[0023] Product performance: after the above production process, the 0.127 mm copper strip has a hardness of HV=173 and a tensile strength of 588 MPa. After treatment at 470°C for 3 minutes, its Vickers hardness is 163, and the high-temperature softening hardness reaches 94% of the original hardness.

[0024] Example 3 In this embodiment, a 1.0 mm thick base material obtained through ingot casting, walking beam furnace heating, hot rolling, quenching, and cold working is used for high-temperature aging, large deformation cold rolling, graded aging, and finished product rolling. The specific process steps are as follows: Step 1, High-temperature aging: Aging treatment is carried out using a bell furnace at 500℃, and the protective gas is N2+H2 for 12 hours. Step 2, large deformation cold rolling: The surface of the material after high temperature aging is cleaned, and then rolled with a large processing rate of 70% to obtain a strip with a thickness of 0.3mm. Step 3, grading and aging: The 0.3mm strip is placed in a bell furnace and held at 300℃ for 6 hours. Then the temperature is increased to 440℃ and held for 4 hours before being removed from the furnace. A protective gas, N2+H2, is used during the holding process. Step 4, Finished product rolling: Roll the 0.3mm thick strip to 0.11mm, with a processing rate of 63.3%.

[0025] Product performance: After the above production process, the produced 0.11mm copper strip has a hardness of HV=175, a tensile strength of 582MPa, and a Vickers hardness of 159 after treatment at 470℃ for 3min. The high-temperature softening hardness reaches 91% of the original hardness.

[0026] Example 4 In this embodiment, a 2.0 mm thick base material obtained through ingot casting, walking beam furnace heating, hot rolling, quenching, and cold working is used for high-temperature aging, large deformation cold rolling, graded aging, and finished product rolling. The specific process steps are as follows: Step 1, High-temperature aging: Aging treatment is carried out using a bell furnace at 530℃, and the protective gas is used for heat preservation for 10 hours. The protective gas is N2+H2. Step 2, large deformation cold rolling: The surface of the material after high temperature aging is cleaned, and then rolled with a large processing rate of 62.5% to obtain a strip with a thickness of 0.75mm; Step 3, grading and aging: Place the 0.75mm strip into a bell furnace and hold it at 350℃ for 6 hours. Then raise the temperature to 460℃ and hold it for 4 hours before removing it from the furnace. Use a protective gas during the holding process. The protective gas is N2+H2. Step 4, Finished product rolling: Roll the 0.75mm thick strip to 0.3mm, with a processing rate of 60%.

[0027] Product performance: After the above production process, the produced 0.75mm copper strip has a hardness of HV=174, a tensile strength of 588MPa, and a Vickers hardness of 158 after treatment at 470℃ for 3min. The high-temperature softening hardness reaches 91% of the original hardness.

[0028] The following are comparative test examples.

[0029] Comparative Example 1 Comparative Example 1 uses the same alloy composition as Examples 1-4. The preparation process does not involve graded aging; it uses only a general aging method. A 2.0 mm thick base material obtained through ingot casting, walking beam furnace heating, hot rolling, quenching, and cold working is used for high-temperature aging, large-deformation cold rolling, general low-temperature aging, and final rolling. Specific process parameters are as follows: Step 1, High-temperature aging: Aging treatment is carried out using a bell furnace at 530℃, and the protective gas is used for heat preservation for 10 hours. The protective gas is N2+H2. Step 2, large deformation cold rolling: The surface of the material after high temperature aging is cleaned, and then rolled with a large processing rate of 62.5% to obtain a strip with a thickness of 0.75mm; Step 3, general low temperature aging: Put the 0.75mm strip into the bell furnace and keep it at 460℃ for 4 hours before taking it out of the furnace. Use a protective gas during the heat preservation. The protective gas is N2+H2. Step 4: Finished product rolling: Roll the 0.75mm thick strip to 0.3mm.

[0030] Product Performance and Analysis: After the above production processes, the produced 0.3mm copper strip has a hardness HV=156 and a tensile strength of 540MPa. After treatment at 470℃ for 3min, its Vickers hardness is 140, and the high-temperature softening hardness reaches 88.5% of the original hardness, which does not meet the performance indicators required by this invention. The reason is that this example lacks a graded aging process, and the Fe atoms dissolved in the alloy did not form precipitated strengthening phases as much as possible, thus failing to meet the performance indicators required by the preparation process of this invention.

[0031] Comparative Example 2 This comparative example uses the same alloy composition as Examples 1-4 and employs a general Cu-Fe-P alloy strip processing method; that is, a base material with a thickness of 2.0 mm is obtained through ingot casting, walking beam furnace heating, hot rolling, quenching, and cold working, and then prepared using a high-temperature aging, large deformation cold rolling, softening annealing, and finished product rolling process. The specific process parameters are as follows: Step 1, High-temperature aging: Aging treatment is carried out using a bell furnace at 550℃, and the protective gas is used for heat preservation for 10 hours. The protective gas is N2+H2. Step 2, large deformation cold rolling: The surface of the material after high temperature aging is cleaned, and then rolled with a large processing rate of 62.5% to obtain a strip with a thickness of 0.75mm; Step 3, softening annealing: Anneal the 0.75mm strip in an air cushion furnace at 600℃ and an annealing speed of 12m / min. Use a protective gas, N2+H2, during annealing. Step 4: Finished product rolling: Roll the 0.75mm thick strip to 0.3mm.

[0032] Product Performance and Analysis: After the above production processes, the produced 0.3mm copper strip has a hardness HV=152 and a tensile strength of 535MPa. After treatment at 470℃ for 3min, its Vickers hardness is 126, and the high-temperature softening hardness reaches 83% of the original hardness, which does not meet the performance indicators required by this invention. The reason is that the softening annealing process temperature in step three causes the Fe strengthening phase and Mg3P2 compound to dissolve back into the copper matrix, thereby affecting the overall amount of strengthening phase precipitation and impacting the overall performance indicators.

[0033] Comparative Example 3 This comparative example uses an ingot of grade TFe2.5, with an alloy composition including: Fe: 2.1-2.6%; P: 0.015-0.15%; Zn: 0.05-0.2%; the balance being copper and unavoidable impurities. The processing method described in Examples 1-4, i.e., ingot casting-walking furnace heating-hot rolling-quenching-cold working, yields a base material with a thickness of 1.5 mm. Then, following the method of this invention, it undergoes high-temperature aging-large deformation cold rolling-graded aging-finished product rolling. Specific process parameters are as follows: Step 1, High-temperature aging: Aging treatment is carried out using a bell furnace at 500℃, and the protective gas is used for heat preservation for 10 hours. The protective gas is N2+H2. Step 2, large deformation cold rolling: The surface of the material after high temperature aging is cleaned, and then rolled with a large processing rate of 66.7% to obtain a strip with a thickness of 0.5 mm. Step 3, grading and aging: Place the 0.5mm strip into a bell furnace and hold it at 340℃ for 5 hours, then raise the temperature to 450℃ and hold it for 4 hours before removing it from the furnace. Use a protective gas during the holding process, which is N2+H2. Step 4: Finished product rolling: Roll the 0.5mm thick strip to 0.203mm; Product Performance and Analysis: After the above production processes, the produced 0.203mm copper strip has a hardness HV=153 and a tensile strength of 545MPa. After treatment at 470℃ for 3min, its Vickers hardness is 127, and the high-temperature softening hardness reaches 83% of the original hardness. Therefore, without compositional control, the performance indicators described in the preparation process of this invention cannot be achieved. This is because the composition of a typical Cu-Fe-P alloy frame, after the above processing, has reached its limit in terms of improving material strength.

[0034] This invention increases the P content by adding Mg, which adds a Mg3P2 strengthening phase compared to the aging precipitates of general Cu-Fe-P alloys. Sn exists in the copper alloy in solid solution, improving the strength and heat resistance of the material, thereby enhancing the overall material performance.

[0035] Comparative Example 4 This comparative example uses the same alloy composition as Examples 1-4. The preparation process is hot rolling-milling-primary rolling-solution treatment-one-cold rolling-pre-aging-reversion heat treatment-cold rolling and aging. The specific process parameters are as follows: Step 1, Hot rolling: The copper alloy ingot is heated, hot rolled, and then quenched to a thickness of 16.5 mm. Step 2, Milling: Mill the hot-rolled copper alloy to remove the oxide layer, leaving a thickness of 15mm. Step 3, Preliminary rolling: The milled copper alloy is pre-rolled to 2.0 mm; Step 4, Solution treatment: The copper alloy after initial rolling is subjected to high-temperature online solution treatment. The heating temperature is 960℃, the flow rate is 4m / min, and the cooling medium is nitrogen or ammonia decomposition gas. Step 5, One-time cold rolling: The solution-treated copper alloy is cold-rolled to 0.8mm in one pass, with a processing rate of 60%. Step 6, Pre-aging: The copper alloy after one cold rolling is subjected to pre-aging treatment at a temperature of 500℃ for 10 hours. Step 7, Regression Heat Treatment: The pre-aged copper alloy is subjected to regression heat treatment at a temperature of 600℃ and a holding time of 5 minutes. Step 8, Cold Rolling and Aging: a. Cold rolling: The 0.8mm strip after step seven is cold rolled on a finishing mill to a thickness of 0.34mm, with a processing rate of 57.5%; b. Single aging: Aging is carried out once in a bell-shaped furnace at an aging temperature of 450℃ for 5 hours; c. Cold rolling: After cold rolling on a finishing mill, the strip thickness is 0.18 mm, and the deformation is 47%; d. Secondary aging: Secondary aging is carried out in a bell-shaped furnace at an aging temperature of 400℃ for 4 hours; e. Final rolling: Final rolling is performed on the finishing mill, with a thickness of 0.11 mm and a total deformation of 38.9%.

[0036] Product Performance and Analysis: After the above production processes, the produced 0.11mm copper strip has a hardness HV=161 and a tensile strength of 555MPa. After treatment at 470℃ for 3min, its Vickers hardness is 140, and the high-temperature softening hardness reaches 87% of the original hardness, which does not meet the performance indicators required by this invention.

[0037] Based on the above preparation process, the solution treatment in step four is beneficial to improving the overall performance of the alloy, but it requires a specific high-temperature air cushion furnace. The reversion heat treatment in step seven will also cause some of the second phase to dissolve back, thus affecting the improvement of the material's comprehensive performance after the subsequent rolling process. Furthermore, the initial rolling process requires at least four cold workings, resulting in a large overall processing rate and a thin final product thickness, with a thickness of 0.203 mm or more. The high-temperature solution treatment thickness in step four needs to be controlled above 3.0 mm, which places high demands on existing equipment and is not suitable for industrial production.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the specific implementation of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the pending claims.

Claims

1. A method for preparing a Cu-Fe-P alloy strip with high hardness and high resistance to softening, characterized in that, Includes the following steps: (1) High temperature aging: Under a protective atmosphere, the Cu-Fe-P alloy base material is kept at 480-550℃ for 7-15 hours to allow Fe and P elements to fully precipitate and form strengthening phases; (2) Large deformation cold rolling: The base material after step (1) is subjected to multiple passes of large-processing cold deformation rolling, with a total deformation of 60% to 70%; (3) Grading and aging: The strip after cold rolling in step (2) is first kept at 300-350℃ for 4-8 hours, and then the temperature is raised to 440-460℃ and kept for 3-6 hours before being taken out of the furnace. Protective gas is used during the heat preservation. (4) Finished product rolling: The strip after step (3) is cold rolled with a total deformation of 60% to 70% to obtain copper alloy strip of the target thickness.

2. The method for preparing the high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 1, characterized in that, The composition of the Cu-Fe-P alloy base material, by weight percentage, includes: Fe: 2.3-2.5%; P: 0.07-0.09%; Zn: 0.05-0.20%; Sn: 0.01-0.04%; Mg: 0.02-0.09%; Ni: 0.005-0.025%; the balance being copper and unavoidable impurities.

3. The method for preparing the high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 1, characterized in that, The thickness of the Cu-Fe-P alloy base material is 1.0~2.0 mm.

4. The method for preparing the high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 3, characterized in that, The Cu-Fe-P alloy base material is made from Cu-Fe-P alloy ingots through heating, hot rolling, quenching, and cold working.

5. The method for preparing the high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 1, characterized in that, In step (1), the Cu-Fe-P alloy base material is subjected to high-temperature aging treatment in a bell furnace.

6. The method for preparing the high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 1, characterized in that, In step (3), the Cu-Fe-P alloy base material is subjected to graded aging treatment in a bell furnace.

7. A Cu-Fe-P alloy strip with high hardness and high resistance to softening, prepared by the method described in any one of claims 1 to 6.

8. The high-hardness, high-softening-resistance Cu-Fe-P alloy strip according to claim 7, characterized in that, Its Vickers hardness HV≥170, tensile strength≥580 MPa, and after treatment at 470℃ / 3min, the high-temperature softening hardness is not less than 90% of the original hardness.