Low-stress high-surface IGBT bottom plate copper material and preparation method thereof

Abstract

The invention provides a low-stress high-surface IGBT (Insulated Gate Bipolar Translator) bottom plate copper material and a preparation method thereof, and belongs to the field of IGBT copper material preparation, and the low-stress high-surface IGBT bottom plate copper material comprises the following components in percentage by weight: 99.95-99.98% of copper element, 10-30 ppm of oxygen element, 30-50 ppm of iron element, 15-30 ppm of phosphorus element, 30-50 ppm of zinc element, 20-50 ppm of tin element and 20-40 ppm of nickel element. The contents of trace elements such as Fe, P, Zn, Sn and Ni in the IGBT bottom plate copper material are accurately controlled, and the oxygen content in the components is greatly reduced, so that the purity of the copper material is improved, the generation of impurity elements is reduced, the Vickers hardness of the obtained copper material is still larger than or equal to 90 HV after the obtained copper material is subjected to heat preservation for 30 minutes at 320 DEG C, and the IGBT bottom plate copper material with excellent mechanical performance is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of IGBT copper material preparation, and in particular to a low-stress high-surface IGBT bottom plate copper material and a preparation method thereof. Background Art

[0002] IGBT (Insulated Gate Bipolar Transistor) is a highly efficient semiconductor device that plays an important role in many high-tech fields due to its excellent high-speed switching characteristics, high voltage tolerance and high current driving capabilities. The IGBT copper baseplate is an important component of the IGBT module. It not only provides the necessary mechanical support and electrical performance guarantee, but also undertakes the key task of thermal management. The copper baseplate has high thermal conductivity and can effectively transfer heat from the IGBT chip to the heat sink, thereby ensuring the normal operation and reliability of the module.

[0003] Although the copper material for IGBT copper base plate is simple in composition and easy to mass produce, there are also some problems in practical application. Patents CN116555619A and CN117721342A respectively provide a copper material for IGBT base plate and a preparation method thereof, which improve the heat resistance and resilience of copper alloys, so that the IGBT copper base plate can meet the requirements of equipment size after welding. Existing technical achievements have not yet fully covered the preparation technology of copper materials for IGBT copper base plates that take into account both low stress and high surface quality. During the application process, the bottom nickel plating layer often has problems such as leakage or weak bonding. For example, in a long-term high-temperature working environment, fatigue damage and corrosion may occur if the surface plating quality is not high, affecting its service life and reliability.

[0004] Based on this, the present invention provides a method for preparing low-stress and high-surface IGBT base plate copper material, so that the nickel plating layer of the entire IGBT copper base plate is uniform and defect-free, and has excellent bonding strength, thereby meeting the development needs of IGBT components in the fields of power modules, new energy, and industry. Summary of the invention

[0005] In view of this, the present invention proposes a low-stress and high-surface IGBT base plate copper material and a preparation method thereof, which are used to solve the problem that the current preparation of copper material for IGBT copper base plate cannot take into account both the low stress performance and high surface quality of the copper plate material.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a low-stress high-surface IGBT bottom plate copper material, in which the copper content is 99.95-99.98% by weight, the oxygen content is 10-30ppm, the iron content is 30-50ppm, the phosphorus content is 15-30ppm, the zinc content is 30-50ppm, the tin content is 20-50ppm, and the nickel content is 20-40ppm. For the performance of the obtained low-stress high-surface IGBT bottom plate copper material finished product, its component ratio requirement is to effectively control the oxygen content. The oxygen element exists in the copper material mainly in the form of oxides. When the oxygen content is high, the distribution of the oxide in the copper matrix may form a fragile area, resulting in a decrease in the strength and toughness of the copper material, especially under stress, which is easy to cause the formation and expansion of cracks, thereby affecting the low-stress performance of the copper material. At the same time, the conductivity of the oxide is much lower than that of pure copper. Too high an oxygen content will reduce the conductivity of the copper material and affect the thermal management and electrical properties of the IGBT. In addition, the presence of oxides will increase the surface roughness of copper materials, thus affecting the surface quality of IGBTs. Especially in high-precision machining processes, oxide particles may cause increased wear of cutting tools, leading to increased machining difficulty. Therefore, reducing the oxygen content can effectively reduce the generation of oxides, thereby reducing the brittleness of the copper matrix, improving the mechanical properties of copper materials, reducing stress concentration, and helping to improve the durability and service life of the base plate. In addition, reducing the oxygen content helps to improve the electrical conductivity and thermal conductivity of copper materials and optimize the operating temperature characteristics of IGBTs.

[0007] On the basis of the above technical scheme, preferably, the iron-phosphorus ratio ranges from 2 to 3 by weight percentage. The second point that affects the performance of the finished copper material is the need to optimize the iron-phosphorus ratio in the components. Iron (Fe) is added to copper as an alloying element to improve the strength and hardness of copper; when the iron content is high, the lattice structure of the copper matrix may change to form an iron phase with higher hardness. Although this can improve the strength of copper, it may sacrifice some ductility and thus affect its tensile properties. Phosphorus (P) usually exists in copper alloys in the form of phosphides. These phosphides can inhibit the oxidation reaction of copper and improve the corrosion resistance of copper materials. The presence of phosphorus can also form a solid solution in copper, thereby improving the plasticity and ductility of copper materials. Therefore, the addition of phosphorus can also help improve the surface quality of copper materials, avoid the formation of surface oxidation, and reduce surface roughness. By controlling the iron-phosphorus ratio within the range of 2 to 3, while ensuring the strength and hardness of the copper material, it will not lead to excessive iron phase, avoid brittleness and low ductility caused by excessive hardness, and maintain an appropriate content of phosphide, effectively improve the antioxidant ability, improve the surface quality, and reduce the formation of oxides on the surface, thereby improving the surface finish and conductivity of the copper material, thereby optimizing the mechanical properties, corrosion resistance, conductivity and processability of the copper material, thereby improving the low stress performance and high surface quality of the IGBT base plate.

[0008] On the other hand, the present invention also provides a method for preparing a low-stress high-surface IGBT bottom plate copper material, which is used to prepare the above-mentioned low-stress high-surface IGBT bottom plate copper material, including the following steps: S1, preparing raw materials according to the composition ratio of the low-stress high-surface IGBT bottom plate copper material, the raw materials are copper materials and other elements, and the copper content in the copper materials is not less than 99.95% by weight; S2, putting the raw materials into a smelting furnace for smelting to obtain an intermediate melt, converting the intermediate melt to a holding furnace and controlling the content of iron, phosphorus, zinc, tin and nickel elements, degassing by bottom blowing argon in the holding furnace, and controlling the content of oxygen elements; S3, casting the melt obtained in step S2 with the assistance of ultrasonic oscillation technology to obtain a copper ingot, and rolling the copper ingot into a low-stress high-surface IGBT bottom plate copper material. In the ultrasonic casting process of the IGBT bottom plate copper material, the precise selection of the vibration frequency plays a decisive role in ensuring the quality of the ingot. Due to the specific requirements of ingot size, melt viscosity, casting temperature and grain refinement of IGBT base plate copper material, the selection of frequency must be carefully considered. Generally speaking, frequencies of 20 to 30 kHz are suitable for large or thick-walled castings, 30 to 50 kHz are suitable for medium-sized castings, and 50 to 100 kHz are suitable for small or thin-walled castings. Alloy type, melt viscosity, temperature, casting size and grain refinement requirements should be considered when selecting frequency. Experimental verification is the key to determining the optimal frequency. Through small-scale tests, process parameter optimization and quality inspection, the most suitable ultrasonic vibration frequency for a specific copper alloy can be found, thereby improving the performance and quality of the casting. This process emphasizes the matching of technology and material properties, as well as the importance of experiments in optimizing casting processes. Through in-depth research and corresponding simulation calculations, the present invention comprehensively considers the physical properties of copper materials and the process characteristics of ultrasonic casting, and finally determines an optimal vibration frequency range of 20 to 40 kHz. Within this frequency range, ultrasound can be effectively transmitted to the melt, generating sufficient vibration force to break the grains, form more nuclei, and achieve grain refinement. The refined grain structure helps to improve the internal quality of the ingot and the density, thereby further improving the mechanical properties and electrical conductivity of the finished copper material, which is particularly important for IGBT base plate copper materials because they need to have good thermal conductivity and electrical properties. By performing ultrasonic casting in the frequency range of 20 to 40 kHz, an IGBT base plate copper ingot with relatively refined grains, few internal defects and high overall quality can be obtained. Therefore, the present invention provides an efficient and accurate frequency selection method for ultrasonic casting of IGBT base plate copper materials, thereby significantly improving the quality of the ingot.

[0009] On the basis of the above technical scheme, preferably, in step S3, the process of rolling the copper ingot into a low-stress and high-surface IGBT bottom plate copper material includes the following steps: S31, hot rolling the copper ingot on a hot rolling mill for seven passes to obtain a hot-rolled billet; S32, rough rolling the hot-rolled billet on a rough rolling mill for five passes, and then performing surface degreasing, pickling and grinding after annealing to obtain a rough-rolled billet; S33, finishing rolling the rough-rolled billet on a finishing mill for two passes to obtain a low-stress and high-surface IGBT bottom plate copper material.

[0010] Further preferably, the deformation of the fifth and sixth passes in the seven-pass hot rolling process in step S31 is 28-35% and 30-36%. The fifth and sixth rolling passes are the passes that play the most important rolling deformation role in the hot rolling process, and their purpose is to control the balance between the grain refinement and mechanical properties of the copper material. A larger deformation can effectively break the original grains of the copper material and refine the grain structure, thereby enhancing the strength and toughness of the copper material, and also improving the low stress performance of the copper material. Within this deformation range, the stress during hot rolling is compressive stress rather than tensile stress, so that small casting defects can be effectively welded, making the hot-rolled strip more uniform and dense, and then the copper material can obtain higher hardness and strength, but too high deformation may lead to insufficient ductility, so reasonable control of the deformation within this range can not only ensure the internal organization and strength of the material, but also maintain its good ductility and avoid the material from becoming brittle.

[0011] Further preferably, the total deformation of the five rough rollings in step S32 is 80-85%, the roughness of the roll in the rough rolling is 0.2-0.3 μm, and the reduction of the grinding brush roller is 10-15 mm. The large total deformation of the rough rolling helps to further break the grains inherited during casting through the effective deformation of the rough rolling billet, further refine the grain structure of the copper material, and improve the mechanical properties and plasticity; through large deformation control, surface defects such as oxides and impurities can be removed, the surface finish can be improved, and the processing difficulty of the subsequent finishing stage can be reduced. The control of the reduction of the grinding brush roller is very important. If the reduction is too small, although the life of the bristles will be longer, the cleaning effect will be poor because the force between the brush roller and the steel strip is small. On the contrary, if the reduction is too large, the bending deformation of the bristles will be large, which will not only affect the cleaning effect, but also a large number of brush marks will appear on the surface of the copper material, which cannot be eliminated in the subsequent finished product rolling, and will also greatly shorten the life of the brush roller. Therefore, the pressing amount needs to be within a moderate range, and the pressing amount of the brush pattern roller of the present invention is controlled to be 10 to 15 mm.

[0012] Further preferably, the total deformation of the two passes of finishing rolling in step S33 is 10-18%, and the roughness of the roller in the finishing rolling is 0.15-0.2 μm. Finishing rolling further refines the grains of the copper material through a smaller deformation, optimizes the microstructure of copper, and improves the mechanical properties of the copper material. Roller roughness has a significant impact on the surface quality of copper strip, mainly including increased surface roughness, surface defects such as scratches and pits, affecting lubrication effect and rolling force, reducing product performance such as weldability and conductivity, and accelerating roller wear. In order to ensure the surface quality of copper strip, it is necessary to select a suitable roller roughness, regularly maintain and grind the rollers, use high-quality lubricants and ensure uniform distribution, and monitor rolling parameters to optimize the process. These measures help to control the influence of roller roughness and produce high-quality copper strips that meet industrial standards. Taking all factors into consideration, the present invention controls the roll roughness during rough rolling to 0.2-0.3 μm and the roll roughness during finished rolling to 0.15-0.2 μm according to the rolling requirements at different stages.

[0013] On the basis of the above technical solution, preferably, the smelting temperature in step S2 is 1150-1200° C. Since the melting point of pure copper is 1083° C., a reasonable smelting temperature can ensure that the melt is completely melted in the liquid phase, while avoiding excessively high temperatures that cause copper liquid to absorb air, deteriorate the quality of the melt, and increase the number of ingot defects, thereby causing a negative impact on the copper material. Therefore, it is ensured that the copper alloy is completely melted without causing excessive oxidation or precipitation of insoluble substances, and the uniformity of the melt is ensured.

[0014] On the basis of the above technical solution, preferably, the dew point temperature of the bottom blowing argon gas used in step S2 is -69°C to -75°C, and the flow rate is 0.01 to 0.02 m 3 / h. Controlling the flow rate of argon gas can prevent the violent stirring of the melt caused by excessive gas flow rate, which will affect the uniformity of the alloy and the stability of the melt; controlling the dew point temperature can help to more effectively remove moisture and impurities in the melt, and prevent moisture or impurities in the argon gas from affecting the melt quality of the copper liquid and causing the melt to deteriorate. Too low a dew point value can improve the melt quality, but increase the smelting cost, while too high a dew point value will bring in more moisture and impurities, which will not achieve the degassing effect and further increase the impurity content of the melt.

[0015] On the basis of the above technical scheme, preferably, in step S3, a horizontal pouring pipe is used for semi-continuous casting, and the casting is assisted by ultrasonic oscillation technology; the length of the horizontal pouring pipe is 250-300 mm, and the ultrasonic vibration frequency is 20-40 kHz. The horizontal pouring pipe is combined with ultrasonic oscillation technology to help the smooth flow of the melt, avoid uneven solidification of the melt or defects, and at the same time, by improving the casting quality, it helps to improve the structural uniformity of the copper ingot.

[0016] The low-stress and high-surface IGBT bottom plate copper material and the preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0017] (1) The present invention accurately controls the contents of trace elements such as Fe, P, Zn, Sn and Ni in the IGBT base plate copper material and significantly reduces the oxygen content in the components, thereby improving the purity of the copper material and reducing the generation of impurity elements. After the obtained copper material is kept at 320°C for 30 minutes, the Vickers hardness of the copper material is still ≥90HV, thereby preparing an IGBT base plate copper material with excellent mechanical properties.

[0018] (2) The present invention optimizes the preparation process, including the steps of smelting, casting, rolling and heat treatment, controls the total deformation and surface roughness of multiple rolling processes, significantly improves the surface quality of the copper material, and achieves zero surface defects after the entire roll of copper material is nickel-plated. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a physical picture of the low stress and high surface IGBT bottom plate copper material of Example 1 of the present invention;

[0021] Figure 2 This is a physical picture of the copper material of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] In this embodiment, 100 g of copper material is weighed, wherein the copper content is 99.98% by weight; and 1 mg of Fe, P, Zn and Ni elements are prepared so as to adjust the content of Fe, P, Zn and Ni elements in the melt during the smelting process.

[0025] The specific steps of the method for preparing the low stress and high surface IGBT bottom plate copper material of this embodiment are as follows:

[0026] S1, according to the composition ratio of low stress and high surface IGBT bottom plate copper material, the raw materials are copper and other elements. Among them, the copper material uses old copper material, which is the recycling of waste materials, which not only reduces production costs, but also reduces environmental pollution, which is in line with the concept of green manufacturing. When the copper material is added, the baking temperature is 220℃ and the baking time is 5min.

[0027] S2, put the raw materials into the smelting furnace for smelting, and the smelting temperature is 1170℃. During the smelting process, dry charcoal is added to cover to obtain an intermediate melt; the intermediate melt is transferred to the holding furnace and the contents of iron, phosphorus, zinc, tin and nickel are controlled to be 48μg, 16μg, 40μg and 20μg by mass; if the content of iron, phosphorus, zinc, tin or nickel is lower than the expected range, the corresponding single substance is added to the melt for supplementation. If the content exceeds the expected range, the smelting time is extended to allow iron, zinc, tin and nickel to react with phosphorus or oxygen to form impurities to reduce their content. At the same time, bottom blowing argon is used in the four areas at the bottom of the holding furnace for degassing and impurity removal. The purpose of degassing is to remove impurities such as hydrogen; the argon dew point temperature is -72℃, and the flow rate is 0.015m 3 / h. At this time, it is also necessary to remove oxygen through other elements, such as phosphorus, which can be combined with oxygen to replace and remove oxygen. The oxygen content can be adjusted by adjusting the melting temperature to change the effect of phosphorus and oxygen combination replacement and deoxidation; or by removing oxygen through charcoal covering and reacting with oxygen, so as to achieve the purpose of controlling the oxygen content within the required range. Adjusting the operating parameters of bottom blowing argon can change the efficiency of oxygen participating in the oxidation reaction and adjust the deoxidation effect. Finally, the oxygen content in the melt is adjusted to 20μg. At the same time, graphite covering is used for heat preservation.

[0028] S3, semi-continuously casting the melt obtained in step S2 through a horizontal pouring pipe, the length of the horizontal pouring pipe is 300 mm; and ultrasonic oscillation technology is used to assist casting and obtain a copper ingot, the ultrasonic vibration frequency is 30 kHz. The copper ingot is rolled into a low-stress and high-surface IGBT bottom plate copper material.

[0029] In step S3, the process of rolling the copper ingot into a low-stress and high-surface IGBT bottom plate copper material includes the following steps:

[0030] S31, heating the copper ingot obtained by casting in step S3 in a walking furnace, the heating atmosphere is a reducing atmosphere, and removing the oxide scale through a dephosphorization process; then hot rolling the copper ingot on a hot rolling mill for seven passes to obtain a hot-rolled billet. Among them, the deformation amounts of the fifth and sixth passes are 35% and 32%.

[0031] S32, the hot rolled billet is subjected to double-sided milling and then subjected to five passes of rough rolling on a rough rolling mill, with a total rolling deformation of 85% and a roll roughness of 0.2 μm. Then, the billet is annealed in a bell furnace at a temperature of 400° C. for 8 hours, followed by surface degreasing, pickling and grinding, with a grinding brush roll reduction of 14 mm, to obtain a rough rolled billet.

[0032] S33, the rough rolled billet is subjected to two passes of finish rolling on a finishing mill, with a total rolling deformation of 10% and a roller roughness of 0.15 μm, followed by degreasing, cleaning and drying to obtain a low-stress and high-surface IGBT bottom plate copper material.

[0033] Example 2

[0034] This embodiment uses the same raw materials as in embodiment 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that the melting temperature in step S2 is 1150°C; the argon dew point temperature of the bottom blowing argon in step S3 is -69°C, and the flow rate is 0.01m 3 The composition ratio of the intermediate melt was detected at this time, so that the contents of O, Fe, P, Zn or Ni were 30 μg, 48 μg, 16 μg, 40 μg and 20 μg respectively.

[0035] Example 3

[0036] This embodiment uses the same raw materials as in embodiment 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that the melting temperature in step S2 is 1200°C; the argon dew point temperature of the bottom blowing argon in step S3 is -75°C, and the flow rate is 0.02m 3 The composition ratio of the intermediate melt was detected at this time, so that the contents of O, Fe, P, Zn or Ni were 10 μg, 48 μg, 16 μg, 40 μg and 20 μg respectively.

[0037] Example 4

[0038] This embodiment uses the same raw materials as in embodiment 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that after the intermediate melt is transferred into the holding furnace in step S2, the contents of Fe and P are adjusted to 40 μg and 20 μg respectively, thereby changing Fe / P to 2.

[0039] Example 5

[0040] This embodiment uses the same raw materials as in embodiment 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that after the intermediate melt is transferred into the holding furnace in step S2, the contents of Fe and P are adjusted to 45 μg and 18 μg respectively, thereby changing Fe / P to 2.5.

[0041] Example 6

[0042] This embodiment uses the same raw materials as in embodiment 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that in step S2, after the intermediate melt is transferred into the holding furnace, the contents of Fe and P are adjusted to 20 μg and 20 μg respectively, thereby changing Fe / P to 1.

[0043] Example 7

[0044] This embodiment uses the same raw materials as in Example 1. The difference between the preparation method of this embodiment and that of Example 1 is that after the intermediate melt is transferred into the holding furnace in step S2, the contents of Fe and P are adjusted to 60 μg and 15 μg, respectively, thereby changing Fe / P to 4, and making the iron content exceed the expected range.

[0045] Comparative Example 1

[0046] In this comparative example, 100 g of copper material was weighed, wherein the copper content was 99.92% by weight; and 1 mg of Fe, P, Zn and Ni were prepared to adjust the content of Fe, P, Zn and Ni in the melt during the smelting process. The preparation method of this comparative example is the same as that of Example 1.

[0047] Comparative Example 2

[0048] This comparative example uses the same raw materials as comparative example 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that after the intermediate melt is transferred into the holding furnace in step S2, the contents of Fe and P are adjusted to 60 μg and 15 μg, respectively, thereby changing Fe / P to 4, and making the iron content exceed the expected range.

[0049] Comparative Example 3

[0050] This comparative example uses the same raw materials as comparative example 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that in step S2, no bottom blowing of argon is used for degassing and impurity removal, and no combined replacement means are used to remove the oxygen element, so that the content of the oxygen element is 50 μg by mass, which exceeds the expected range.

[0051] Comparative Example 4

[0052] This comparative example uses the same raw materials as comparative example 1. The difference between the preparation method of this embodiment and that of embodiment 1 is that: when the intermediate melt is transferred from the converter to the holding furnace in step S2, the contents of iron, phosphorus, zinc, tin and nickel are controlled to be 60 μg, 40 μg, 60 μg and 50 μg by mass, respectively, according to the principle of less supplement and less supplement; bottom blowing of argon is not used for degassing and impurity removal, and combined replacement means are not used to remove oxygen elements, so that the content of oxygen elements is 50 μg by mass, so the contents of oxygen, iron, phosphorus, zinc and nickel exceed the expected range.

[0053] The present invention prepares samples according to the preparation methods of Examples 1 to 7 and Comparative Examples 1 to 4 and tests their performance. For the convenience of comparative analysis, the component proportions of the low stress and high surface IGBT bottom plate copper materials obtained in Examples 1 to 7 and Comparative Examples 1 to 4 are listed in Table 1, and the performance test results of the samples obtained in Examples 1 to 7 and Comparative Examples 1 to 4 are listed in Table 2.

[0054] Table 1 Comparison table of composition ratios of various embodiments and comparative examples

[0055] Group distribution ratio Cu / g O / μg Fe / μg P / μg Zn / μg Ni / μg Fe / P Example 1 99.98 20 48 16 40 20 3 Example 2 99.98 30 48 16 40 20 3 Example 3 99.98 10 48 16 40 20 3 Example 4 99.98 20 40 20 40 20 2 Example 5 99.98 20 45 18 40 20 2.5 Example 6 99.98 20 20 20 40 20 1 Example 7 99.98 20 60 15 40 20 4 Comparative Example 1 99.92 20 48 16 40 20 3 Comparative Example 2 99.92 20 60 15 40 20 4 Comparative Example 3 99.92 50 48 16 40 20 3 Comparative Example 4 99.92 50 60 40 60 50 1.5

[0056] According to Table 1, the difference between Examples 1 to 3 is that there is a large difference in their oxygen content, the difference between Examples 1 and 4 to 7 is that there is a large difference in their iron-phosphorus ratios, and the copper content in Comparative Examples 1 and 2 is relatively low and there is also a difference in the iron-phosphorus ratios of the two.

[0057] Table 2 Comparison table of sample performance of each embodiment and comparative example

[0058]

[0059]

[0060] By comparing the detection performance data of the samples obtained in Examples 1 to 3, it can be found that as the oxygen content in the copper material gradually decreases, the residual stress of the sample shows a significant decreasing trend, and the surface roughness of the copper material also decreases accordingly, proving that as shown above, the increase in the oxygen content will cause the distribution of oxides in the copper matrix to form fragile areas, thereby affecting the low-stress performance of the copper material, and the presence of oxides will increase the surface roughness of the copper material, resulting in poor surface quality of the IGBT.

[0061] By comparing the detection performance data of the samples obtained in Examples 1, 4 and 5, it can be found that the reduction of the iron-phosphorus ratio in the copper material will also cause the residual stress of the sample to show a significant decreasing trend, and when the iron-phosphorus ratio is within an appropriate range (2-3), as the iron content increases (i.e., the iron-phosphorus ratio increases), the iron phase in the copper material increases and the phosphorus element is appropriate, which not only helps to improve the mechanical properties of the copper material (the strength data of Example 1 is relatively better), but also can weaken the generation of oxides in the copper material through the phosphorus element, thereby ensuring the high surface quality of the copper material; as the iron-phosphorus ratio gradually increases within an appropriate range, the influence of the iron-phosphorus ratio on the residual stress and surface roughness gradually weakens. By comparing the test performance data of the samples obtained by adding Examples 6 and 7 with those of Examples 1, 4 and 5, it can be found that when the optimized iron-phosphorus ratio is not controlled within the appropriate range (2-3), a relatively small iron-phosphorus ratio means that there are fewer iron phases and excessive phosphorus in the copper material. At this time, not only the mechanical properties of the copper material will be affected, but also the residual stress of the copper material cannot be effectively reduced, and it is difficult to help reduce its roughness, which leads to obvious defects on the surface of the copper material; if the iron-phosphorus ratio is too large, it means that there are more iron phases and insufficient phosphorus in the copper material, resulting in an increase in the oxide content in the copper material, which leads to an increase in the residual stress of the copper material, and the roughness is also large, and obvious defects also occur on the surface of the copper material.

[0062] By comparing the test performance data of the samples obtained in Example 1 with those in Comparative Examples 1 and 2, it can be found that when the copper content in the copper material is significantly reduced, the density of the copper matrix is ​​reduced, causing the oxides to be more commonly distributed inside the copper matrix to form more fragile areas, which not only affects the mechanical properties of the copper material, but also causes its residual stress to be very high and the surface quality to be very poor; even if the mechanical properties of the copper material can be improved to a certain extent by increasing the iron-phosphorus ratio (comparing Comparative Examples 1 and 2), its residual stress and surface quality are still in a relatively poor state.

[0063] By comparing the test performance data of the samples obtained in Example 1 with those in Comparative Examples 3 and 4, it can be found that when there are more oxygen impurities in the copper material, the influence on the mechanical properties of the copper material is extremely significant, resulting in high residual stress and poor surface quality. At the same time, by comparing Comparative Examples 3 and 4, it can be found that the control of other metal elements is also a major factor affecting the mechanical properties of the copper material.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low stress and high surface IGBT bottom plate copper material, characterized by: Measured by weight percentage, the copper content of the copper material is 99.95-99.98%, the oxygen content is 10-30 ppm, the iron content is 30-50 ppm, the phosphorus content is 15-30 ppm, the zinc content is 30-50 ppm, the tin content is 20-50 ppm, and the nickel content is 20-40 ppm.

2. The low stress and high surface IGBT bottom plate copper material according to claim 1, characterized in that: The iron-to-phosphorus ratio ranges from 2 to 3 by weight.

3. A method for preparing a low-stress high-surface IGBT bottom plate copper material, characterized in that: Used for preparing the low stress and high surface IGBT bottom plate copper material as claimed in claim 1 or 2, The following steps are included: S1, preparing raw materials according to the composition ratio of the low stress and high surface IGBT bottom plate copper material, the raw materials are copper material and other elements, and the copper content in the copper material is not less than 99.95% by weight; S2, putting the raw materials into a smelting furnace for smelting to obtain an intermediate melt, transferring the intermediate melt to a holding furnace and controlling the contents of iron, phosphorus, zinc, tin and nickel elements, degassing by bottom blowing argon in the holding furnace, and controlling the content of oxygen elements; S3, casting the melt obtained in the step S2 with the assistance of ultrasonic oscillation technology to obtain a copper ingot, and rolling the copper ingot into a low-stress and high-surface IGBT bottom plate copper material.

4. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 3, characterized in that: In step S3, the process of rolling the copper ingot into a low-stress and high-surface IGBT bottom plate copper material includes the following steps: S31, hot rolling the copper ingot on a hot rolling mill for seven passes to obtain a hot-rolled billet; S32, performing five passes of rough rolling on the hot rolled billet on a rough rolling mill, and then performing surface degreasing, pickling and grinding after annealing to obtain a rough rolled billet; S33, performing two passes of finish rolling on the rough-rolled billet on a finishing mill to obtain a low-stress and high-surface IGBT bottom plate copper material.

5. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 4, characterized in that: In the seven-pass hot rolling process in step S31 , the deformation amounts of the fifth and sixth passes are controlled respectively.

6. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 4, characterized in that: In the step S32, the total deformation of the five rough rolling passes is controlled, the roughness of the roll in the rough rolling is adjusted, and the pressing amount of the brush roller in the grinding treatment is adjusted.

7. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 4, characterized in that: In step S33, the total deformation of two passes of finishing rolling is controlled, and the roughness of the rolls during finishing rolling is adjusted.

8. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 3, characterized in that: The smelting temperature in step S2 is 1150-1200°C.

9. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 3, characterized in that: The dew point temperature of the bottom-blown argon gas used in step S2 is -69°C to -75°C, and the flow rate is 0.01 to 0.02 m 3 / h.

10. The method for preparing a low-stress high-surface IGBT bottom plate copper material according to claim 3, characterized in that: In step S3, semi-continuous casting is performed using a transverse pouring tube, and the casting is assisted by ultrasonic oscillation technology.

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