Oxygen-free copper strip and method of making and using same

Abstract

The application provides a kind of oxygen-free copper strip and its preparation method and application, it relates to copper alloy technical field.The oxygen-free copper strip provided by the application includes: Mg, Ag, La and Cu according to mass percentage;The total amount of three elements of Mg, Ag and La is not more than 0.2wt%, and the addition amount of any element is not less than 0.001wt%;In the oxygen-free copper strip, the average grain size is less than or equal to 0.06mm, the twin crystal ratio is greater than or equal to 20%, and the number density of second phase particles is greater than or equal to 1x10 ‑3 / μm 2 The oxygen-free copper strip can be applied to the heat dissipation substrate in IGT module and ceramic copper-clad plate at the same time, which can not only solve the problem of hardness reduction after heating of the heat dissipation substrate, but also solve the problem of easy failure of welding between oxygen-free copper and ceramic in ceramic copper-clad plate due to grain growth.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper alloy, in particular to a non-oxygen copper strip and a preparation method and application thereof. BACKGROUND

[0002] The IGBT module (Insulated Gate Bipolar Transistor) is a composite power semiconductor device formed by IGBT chips and freewheeling diodes through circuit packaging, which has both high input impedance of MOSFET and low on-state voltage drop characteristics of bipolar transistor. The module is packaged with heat dissipation substrate, ceramic copper clad plate and heat dissipation structure, containing components such as driving circuit and protection circuit, with voltage covering 600V-6500V and current reaching 3600A, mainly applied to the fields of high-power industrial frequency converter, electric welding machine, new energy vehicle (motor controller, vehicle-mounted air conditioner, charging pile), rail transit equipment, white household appliance, photovoltaic, wind power, etc.

[0003] Among them, the heat dissipation substrate is the key component of IGBT module heat dissipation, which needs to be formed with a certain curvature after stamping to ensure that it can be combined flatly with the heat dissipation glue after assembly. The product needs to be kept at 290℃ for 10 minutes, and the hardness should not be less than 80% of the original hardness. However, the IGBT substrate prepared by the existing production process using conventional red copper alloy has a softening point below 250℃, which cannot meet the requirement that the hardness should not be less than 80% of the original hardness at 290℃ for 10 minutes.

[0004] The copper cladding process of the ceramic copper clad plate needs to bond the copper material and the ceramic plate under high temperature. However, after high-temperature heat treatment, the copper material grains grow rapidly, and the grain size can even reach millimeter level, which will form "orange peel texture" at the bonding surface and the free surface of the copper material and the ceramic plate, increasing the surface roughness of the copper material. On the one hand, the increase of the bonding surface roughness will increase the gap between the copper material and the ceramic plate, and thus reduce the copper / ceramic bonding strength or even cause bonding failure; on the other hand, the increase of the free surface roughness will also bring a series of negative effects to the subsequent etching, cleaning, welding and other processes, and thus reduce the copper / component weld strength or even cause welding failure.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The first object of the present application is to provide a non-oxygen copper strip to solve the above technical problems.

[0007] The second object of the present application is to provide a preparation method of the non-oxygen copper strip.

[0008] The third object of the present application is to provide an application of the non-oxygen copper strip in preparing an IGBT module.

[0009] In order to achieve the above objects, the following technical solutions are adopted:

[0010] In a first aspect, the present application provides an oxygen-free copper strip, comprising Mg, Ag, La and Cu;

[0011] The total amount of the three elements of Mg, Ag and La is not more than 0.2wt%, and the addition amount of any element is not less than 0.001wt%;

[0012] In the oxygen-free copper strip, the average grain size is ≤0.06mm, the twin crystal ratio is ≥20%, and the number density of the second phase particles is ≥1×10 -3 Individual / μm 2 .

[0013] In a second aspect, the present application provides a preparation method of the above-mentioned oxygen-free copper strip, comprising the following steps:

[0014] Melting, casting, hot rolling, first cold rolling, first annealing, second cold rolling, second annealing and third cold rolling are carried out to prepare the heat-resistant oxygen-free copper strip.

[0015] As a further technical solution, the temperature of the melting is 1160-1190℃;

[0016] In the melting process, copper plates are first added, and after melting, silver and lanthanum elements are introduced, and finally magnesium element is introduced;

[0017] The temperature of the casting is 1160-1180℃, and the casting speed is 50~100mm / min.

[0018] As a further technical solution, the hot rolling comprises: heating the cast ingot obtained by casting to 750~850℃, and then carrying out hot rolling, wherein the opening rolling temperature of the hot rolling is 700~750℃, and the final rolling temperature is above 450℃;

[0019] The total processing rate of the hot rolling is 80%~95%.

[0020] As a further technical solution, the processing pass of the first cold rolling is 5~9 passes, the single pass processing rate is 15%~40%, and the total processing rate is 75%~90%.

[0021] As a further technical solution, the temperature of the first annealing is 400~500℃, and the holding time is 0.5~8h.

[0022] As a further technical solution, the processing pass of the second cold rolling is 5~7 passes, the single pass processing rate is 20%~35%, and the total processing rate is 60%~80%.

[0023] As a further technical solution, the temperature of the second annealing is 400~450℃, and the holding time is 1~8h.

[0024] As a further technical solution, the processing pass of the third cold rolling is 2-3 passes, the single pass processing rate is 10%-25%, and the total processing rate is 30%-45%.

[0025] In a third aspect, the application provides application of the above-mentioned oxygen-free copper strip in preparation of an IGBT module.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] The oxygen-free copper strip provided by the application has an average grain size of ≤0.06 mm, a twin crystal ratio (ratio of grain area containing twin crystals in a unit area to unit area) of ≥20%, a number density of second phase particles of ≥1×10 -3 / μm 2 The copper matrix has an electrical conductivity of ≥98% IACS, an oxygen content of ≤20 ppm, a hardness of ≥105 HV, and the hardness remains ≥80% of the original hardness after 1 hour of heat preservation at 400 DEG C, the grain size is ≤0.07 mm after 30 min of heat preservation at 900 DEG C, and the grain size is ≤0.08 mm after 3 min of heat preservation at 1065 DEG C. The oxygen-free copper strip can be applied to both heat dissipation substrates and ceramic copper-clad plates in IGT modules, and can solve the problems of hardness reduction of the heat dissipation substrate after heating and easy failure of welding between the oxygen-free copper and the ceramic in the ceramic copper-clad plate due to grain growth. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0029] Figure 1 The second phase particle image under a transmission electron microscope;

[0030] Figure 2 The grain size and twin crystal image under a metallographic microscope. EMBODIMENT

[0031] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] In a first aspect, the present invention provides an oxygen-free copper strip, mainly composed of Mg, Ag, La, and Cu. The total amount of Mg, Ag, and La does not exceed 0.2 wt%, and the amount of any one element added is not less than 0.001 wt%. In the oxygen-free copper strip, the mass percentage of Mg is 0.001%-0.1%, for example, but not limited to 0.001%, 0.01%, or 0.1%; the mass percentage of Ag is 0.001%-0.1%, for example, but not limited to 0.001%, 0.01%, or 0.1%; and the mass percentage of La is 0.001%-0.1%, for example, but not limited to 0.001%, 0.01%, or 0.1%.

[0033] In the oxygen-free copper strip, the average grain size is ≤0.06mm, the twinning ratio is ≥20%, and the number density of second-phase particles is ≥1×10⁻⁶. -3 per μm 2 .

[0034] In this scheme, twins and second-phase particles mainly achieve the increase of softening temperature of oxygen-free copper and the suppression of grain growth at high temperatures through the synergistic effect of hindering dislocation movement and pinning grain boundary migration. The strengthening mechanisms of the two are different but complementary, as detailed below:

[0035] 1. The role of twins:

[0036] 1) The principle of increasing the softening temperature

[0037] Softening is essentially the process by which the energy stored in deformation is released through recovery and recrystallization. Twin boundaries are a special type of coherent grain boundary with low interfacial energy, acting as a barrier to dislocation movement. When a dislocation crosses a twin boundary, it must change its slip direction or decompose into partial dislocations, increasing the energy barrier for dislocation movement. At high temperatures, the coherent structure of twin boundaries exhibits higher stability than ordinary grain boundaries, making them less prone to migration and decomposition, effectively delaying the initiation of recovery and recrystallization.

[0038] 2) The principle of inhibiting high-temperature grain growth

[0039] The driving force of grain growth is the reduction of grain boundary interface energy, and the grain boundary will spontaneously migrate at high temperature to reduce the total interface energy. Twin as a barrier to grain boundary migration can effectively hinder the migration of grain boundary, and its high thermal stability can be anchored in the grain for a long time. At high temperature, when the recrystallized grain begins to grow, the twin will constantly break the growth process, and a rapidly growing grain cannot easily "annex" another grain divided by a dense twin network, because a large amount of energy is needed to eliminate these low-energy twin boundaries, which leads to the discontinuity of grain growth, effectively limiting the maximum grain size.

[0040] 2. The role of the second phase particles:

[0041] The second phase particles have a similar effect to twins, which also hinder the recovery, recrystallization and grain growth process by hindering dislocations and pinning grain boundary migration, thereby achieving the effect of improving the softening temperature and inhibiting grain growth. The difference is that the second phase particles in the present application are refractory compounds, which are smaller in size and have higher thermal stability, and can remain stable even at temperatures near the melting point of the substrate, thereby providing more persistent forces.

[0042] 3. Synergistic effect of the two:

[0043] The proportion of the second phase particles and the alloying elements is related, and too much proportion of alloying elements will lead to a decrease in the electrical conductivity of the copper matrix, so the present application selects the synergistic effect of the second phase particles and the twins. The twin establishes a "trunk defense network" at the micron scale, and the second phase particles fill a "base defense network" at the nanoscale, and the two synergistically hinder the recovery, recrystallization and grain growth process at multiple scales, thereby achieving the effect of improving the softening temperature and inhibiting grain growth.

[0044] The oxygen-free copper of the present application has a synergistic effect of twins and second phase particles, an electrical conductivity of ≥98%IACS, an oxygen content of ≤20ppm, a hardness of ≥105HV, a hardness of more than 80% of the original hardness after 1 hour of holding at 400℃, a grain size of ≤0.07mm after 30min of holding at 900℃, and a grain size of ≤0.08mm after 3min of holding at 1065℃.

[0045] In a second aspect, the present application provides a preparation method of the above-mentioned oxygen-free copper strip, comprising the following steps:

[0046] Melting, casting, hot rolling, first cold rolling, first annealing, second cold rolling, second annealing and third cold rolling are carried out to prepare the heat-resistant oxygen-free copper strip.

[0047] The preparation method provided by the present application is simple and convenient, and can prepare an oxygen-free copper strip with an average grain size of ≤0.06mm, a twin proportion of ≥20%, and a number density of second phase particles of ≥1×10 -3 / μm2 Oxygen-free copper strip.

[0048] In some alternative embodiments, the melting temperature may be, for example, but not limited to, 1160-1190°C;

[0049] During the smelting process, copper plates are added first, then silver and lanthanum are introduced after melting, and finally magnesium is introduced.

[0050] The casting temperature can be, for example, but not limited to, 1160°C, 1170°C, or 1180°C, and the casting speed can be, for example, but not limited to, 50 mm / min, 80 mm / min, or 100 mm / min.

[0051] In some alternative implementations, the time interval between the introduction of silver and lanthanum and the introduction of magnesium is 5-15 min (e.g., but not limited to 5 min, 10 min or 15 min).

[0052] Lanthanum and magnesium are both easily oxidized elements, and at 1160-1190℃, the oxygen potential of lanthanum is lower than that of magnesium, indicating that lanthanum will preferentially react with oxygen within the smelting temperature range of this invention. If lanthanum and magnesium are added simultaneously, or magnesium is added first, although some of the oxidized magnesium will be reduced by lanthanum, some magnesium oxides will still aggregate into slag and float on the surface of the molten copper, unable to be reduced, resulting in a decrease in magnesium content, a decrease in second-phase particles, and a decrease in hardness retention at 400℃. If the time interval between introducing lanthanum and magnesium is too short, the effect of lanthanum is not obvious; if the interval is too long, the lanthanum content will decrease due to evaporation, which will also affect the microstructure and properties of the finished product.

[0053] In some optional embodiments, the hot rolling includes: heating the cast ingot to 750~850°C for 4-5 hours, followed by hot rolling. The initial rolling temperature of the hot rolling can be, for example, but not limited to, 700°C, 730°C or 750°C, and the final rolling temperature can be, for example, but not limited to, above 450°C.

[0054] The total processing rate of the hot rolling can be, for example, but not limited to, 80%, 90% or 95%.

[0055] In some optional embodiments, the hot rolling process further includes milling. The present invention does not impose specific limitations on the milling method, and any method well known to those skilled in the art can be used.

[0056] In some alternative embodiments, the first cold rolling process pass can be, but is not limited to, 5 passes, 7 passes or 9 passes, with a single pass reduction rate in the range of 15% to 40% (e.g., but not limited to, 15%, 25% or 40%), and a total reduction rate of, e.g., but not limited to, 75%, 80% or 90%.

[0057] In some alternative embodiments, the first annealing temperature can be, but is not limited to, 400°C, 450°C or 500°C, and the holding time can be, but is not limited to, 0.5h, 4h or 8h.

[0058] In some alternative embodiments, the first annealing process can further include a cleaning process, the specific operation method of which is not limited, and any method known to those skilled in the art can be used.

[0059] In some alternative embodiments, the second cold rolling process pass can be, but is not limited to, 5 passes or 7 passes, with a single pass reduction rate in the range of 20% to 35% (e.g., but not limited to, 20%, 25% or 30%), and a total reduction rate of, e.g., but not limited to, 60%, 70% or 80%.

[0060] In some alternative embodiments, the second annealing temperature can be, but is not limited to, 400°C, 430°C or 450°C, and the holding time can be, but is not limited to, 1h, 4h or 8h.

[0061] The purpose of annealing is to regulate the recrystallization structure and form a sufficient number of twins. If the annealing temperature is too low or the holding time is too short, the recrystallization structure and a sufficient number of twins cannot be obtained; if the annealing temperature is too high or the holding time is too long, the recrystallization grains will become coarse, and the twin boundaries will migrate, merge or annihilate, resulting in a decrease in the number of twins. Although the second cold rolling after the first annealing will cause the twins to be covered by the deformed fiber structure, the specific orientation difference between the twin region and the matrix still exists, and the original twin boundary is a region with high dislocation density and high interface energy, which is often the preferred position for the nucleation of recrystallization grains. Some newly formed recrystallization nuclei will generate new twins by inheriting the original orientation. Therefore, without the first annealing, the number of twins will be greatly reduced. The second annealing directly regulates the grain size and the number of twins of the finished product. Without the second annealing, not only there are no twins, but also the material will degenerate into a high driving force and low resistance system, and the grain growth rate at high temperature will be significantly accelerated. The difference between the second annealing process parameters and the first annealing is to more accurately adjust the grain size of the finished product.

[0062] In some alternative embodiments, the second annealing process can further include a cleaning process, the specific operation method of which is not limited, and any method known to those skilled in the art can be used.

[0063] In some alternative embodiments, the third cold rolling process can be, but is not limited to, 2-3 passes, with a single pass reduction rate in the range of 10%-25% (for example, but not limited to, 10%, 20% or 25% for each pass), and a total reduction rate of, for example, but not limited to, 30%, 35% or 45%.

[0064] In some alternative embodiments, the third cold rolling is followed by cleaning, the specific operation method of which is not limited and can be performed using methods well known to those skilled in the art.

[0065] In some alternative embodiments, the third cold rolling is followed by a stretch bending and straightening process.

[0066] The parameters of the stretch bending and straightening process include: an unwinding tension of 10-45 N / mm 2 , a winding tension of 18-60 N / mm 2 , and an entry extension of 0.05%-0.3%.

[0067] In a third aspect, the present application provides the use of the oxygen-free copper strip described above in the preparation of an IGBT module.

[0068] The oxygen-free copper strip provided by the present application has an average grain size of ≤0.06 mm, a twin crystal ratio (the ratio of the area of the grain containing twin crystals per unit area to the unit area) of ≥20%, and a number density of second phase particles of ≥1×10 -3 particles / μm 2 . The copper matrix has an electrical conductivity of ≥98% IACS, an oxygen content of ≤20 ppm, a hardness of ≥105 HV, and a hardness retention rate of ≥80% after being kept at 400℃ for 1 hour, a grain size of ≤0.07 mm after being kept at 900℃ for 30 min, and a grain size of ≤0.08 mm after being kept at 1065℃ for 3 min. The oxygen-free copper strip can be simultaneously applied to a heat dissipation substrate and a ceramic copper-clad plate in an IGT module, and can not only solve the problem of hardness reduction of the heat dissipation substrate after heating, but also solve the problem of easy failure of the welding between the oxygen-free copper and the ceramic in the ceramic copper-clad plate due to grain growth.

[0069] The present application will be further described below through specific examples and comparative examples, but it should be understood that these examples are only for a more detailed description and should not be understood as limiting the present application in any form.

[0070] Example 1:

[0071] Melting and casting: The raw materials are weighed according to the alloy composition ratio, and then melting and casting are performed in sequence. The raw materials need to be cleaned and dried before melting; after being added to the melting furnace, vacuum is first extracted to 1.5×10 -2Pa, and then copper was melted by heating; after the copper plate was completely melted, the temperature was raised to 1175℃ and kept for 25 min; then argon was introduced with a pressure of 0.4 MPa; then the alloy elements were added, 0.05% of silver and 0.05% of lanthanum elements were added first, 0.05% of magnesium elements was added after 10 min of standing, and 10 min of standing again; finally, casting was started, the casting temperature was 1165℃, the casting speed was 75 mm / min, and the cooling water flow was 40 m 3 / h.

[0072] Hot rolling: the ingot was heated by using a step furnace, the heating temperature was 800℃, the heating time was 4.5 h, the opening rolling temperature was 725℃, the final rolling temperature was 480℃, the total processing rate was 85%, and after the hot rolling was completed, water cooling and face milling were performed;

[0073] First cold rolling: the oxygen-free copper plate after face milling was cold rolled, the processing pass was 7 passes, the single pass processing rate was 15%-35%, and the total processing rate was 85%;

[0074] First annealing: the oxygen-free copper plate after the first cold rolling was coiled, and was placed in a bell furnace for recrystallization annealing, the annealing temperature was 450℃, the holding time was 3 h, and after the first annealing was completed, cleaning was performed;

[0075] Second cold rolling: the cleaned oxygen-free copper plate strip after the first cold rolling was cold rolled, the processing pass was 5 passes, the single pass processing rate was 20%-30%, and the total processing rate was 70%;

[0076] Second annealing: the oxygen-free copper strip after the second cold rolling was placed in a bell furnace for recrystallization annealing, the annealing temperature was 430℃, the holding time was 4 h, and after the second annealing was completed, cleaning was performed;

[0077] Third cold rolling: the processing pass was 3 passes, the single pass processing rate was 15%-20%, and the total processing rate was 40%; after the third cold rolling was completed, cleaning was performed;

[0078] Stretching, bending and straightening, opening tension 25 N / mm 2 , winding tension 35 N / mm 2 , inlet extension 0.1%.

[0079] The transmission electron microscope result of the prepared strip is shown in Figure 1 , and the metallographic microscope result is shown in Figure 2 .

[0080] Example 2:

[0081] Melting and casting: the raw materials were weighed according to the alloy composition ratio, and then melting and casting were sequentially performed. Before melting, the raw materials needed to be cleaned and dried; after being added to the melting furnace, vacuum was first extracted to 1.1 x 10 -2Pa, and then copper is heated; after the copper plate is completely melted, the temperature is raised to 1160°C, and is kept for 30 min; then argon is introduced, and the pressure is 0.3 MPa; then the alloy elements are added, 0.001% of silver and 0.001% of lanthanum elements are added first, 0.001% of magnesium elements is added after 10 min of standing, and is again stood for 10 min; finally, casting is started, the casting temperature is 1160°C, the casting speed is 100 mm / min, and the cooling water flow is 50 m 3 / h.

[0082] Hot rolling: the ingot is heated by using a step furnace, the heating temperature is 750°C, the heating time is 5 h, the rolling start temperature is 700°C, the final rolling temperature is 450°C, the total processing rate is 80%, and after the hot rolling is completed, water cooling and face milling are performed, the specific operation method is not limited, and methods well known to those skilled in the art can be used;

[0083] First cold rolling: the oxygen-free copper plate after face milling is cold-rolled, the processing pass is 9 passes, the single pass processing rate is 15%-30%, and the total processing rate is 90%;

[0084] First annealing: the oxygen-free copper plate after the first cold rolling is coiled, and is placed in a bell furnace for recrystallization annealing, the annealing temperature is 400°C, and the holding time is 8 h; after the first annealing is completed, cleaning is performed;

[0085] Second cold rolling: the oxygen-free copper plate after cleaning is secondarily cold-rolled, the processing pass is 5 passes, the single pass processing rate is 20%-25%, and the total processing rate is 60%;

[0086] Second annealing: the oxygen-free copper plate after the second cold rolling is placed in a bell furnace for recrystallization annealing, the annealing temperature is 400°C, and the holding time is 8 h; after the second annealing is completed, cleaning is performed;

[0087] Third cold rolling: the processing pass is 3 passes, the single pass processing rate is 10%-25%, and the total processing rate is 45%; after the third cold rolling is completed, cleaning is performed;

[0088] Stretching, bending and straightening, unwinding tension 10 N / mm 2 , winding tension 18 N / mm 2 , inlet extension 0.01%.

[0089] Example 3:

[0090] Melting and casting: the raw materials are weighed according to the alloy composition ratio, and then are sequentially subjected to melting and casting. Before melting, the raw materials need to be cleaned and dried; after being added to a melting furnace, vacuum is first extracted to 1.3 x 10 -2Pa, then copper is heated and melted; after the copper plate is completely melted, the temperature is raised to 1190℃, and kept for 20 min; then argon is introduced, and the pressure is 0.5 MPa; then the alloy elements are added, 0.1% of silver and 0.05% of lanthanum elements are added first, 0.05% of magnesium elements are added after 10 min of standing, and again 10 min of standing; finally, casting is started, the casting temperature is 1180℃, the casting speed is 50 mm / min, and the cooling water flow is 25 m 3 / h.

[0091] Hot rolling: the ingot is heated by using a step furnace, the heating temperature is 850℃, the heating time is 4 h, the rolling starting temperature is 750℃, the final rolling temperature is 500℃, the total reduction is 95%, and after the hot rolling is completed, water cooling and face milling are performed, the specific operation method is not limited, and methods well known to those skilled in the art can be used;

[0092] First cold rolling: the oxygen-free copper plate after face milling is cold-rolled, the processing passes are 5 passes, the single-pass reduction is 20%-40%, and the total reduction is 75%;

[0093] First annealing: the oxygen-free copper plate after the first cold rolling is coiled, and is placed in a bell furnace for recrystallization annealing, the annealing temperature is 500℃, and the holding time is 0.5 h; after the first annealing is completed, cleaning is performed;

[0094] Second cold rolling: the oxygen-free copper plate after cleaning is cold-rolled for the second time, the processing passes are 7 passes, the single-pass reduction is 20%-30%, and the total reduction is 80%;

[0095] Second annealing: the oxygen-free copper plate after the second cold rolling is placed in a bell furnace for recrystallization annealing, the annealing temperature is 450℃, and the holding time is 1 h; after the second annealing is completed, cleaning is performed;

[0096] Third cold rolling: the processing passes are 2, the single-pass reduction is 15%-20%, and the total reduction is 30%; after the third cold rolling is completed, cleaning is performed, and the specific operation method is not limited, and methods well known to those skilled in the art can be used;

[0097] Stretching, bending, straightening, unwinding tension 45 N / mm 2 , winding tension 60 N / mm 2 , inlet extension 0.3%.

[0098] Comparative Example 1:

[0099] The difference from Example 1 is that the mass fraction of silver is 0.0005%, the mass fraction of magnesium is 0.0005%, and the mass fraction of lanthanum is 0.0005%.

[0100] Comparative Example 2:

[0101] The difference from Example 1 is that the mass fraction of silver is 0.1%, the mass fraction of magnesium is 0.1%, and the mass fraction of lanthanum is 0.1%.

[0102] Comparative Example 3:

[0103] The difference from Example 1 is that silver, lanthanum and magnesium elements are added at the same time.

[0104] Comparative Example 4:

[0105] The difference from Example 1 is that the final hot rolling temperature is 420℃.

[0106] Comparative Example 5:

[0107] The difference from Example 1 is that there is no first annealing.

[0108] Comparative Example 6:

[0109] The difference from Example 1 is that the second annealing temperature is 500℃, and the time is 1h.

[0110] Comparative Example 7:

[0111] The difference from Example 1 is that the second annealing temperature is 350℃, and the time is 6h.

[0112] Comparative Example 8:

[0113] The difference from Example 1 is that there is no second annealing.

[0114] Table 1 Performance and microstructure table of examples and comparative examples

[0115]

[0116] Note: The electrical conductivity cannot be lower than 98% to meet product requirements.

[0117] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An oxygen-free copper strip, characterized in that, Including Mg, Ag, La, and Cu; The total amount of the three elements Mg, Ag, and La shall not exceed 0.2 wt%, and the amount of any one element added shall not be less than 0.001 wt%. In the oxygen-free copper strip, the average grain size is ≤0.06mm, the twinning ratio is ≥20%, and the number density of second-phase particles is ≥1×10⁻⁶. -3 per μm 2 .

2. The method for preparing the oxygen-free copper strip according to claim 1, characterized in that, Includes the following steps: Heat-resistant oxygen-free copper strip is prepared by smelting, casting, hot rolling, first cold rolling, first annealing, second cold rolling, second annealing and third cold rolling.

3. The preparation method according to claim 2, characterized in that, The melting temperature is 1160-1190℃; During the smelting process, copper plates are added first, then silver and lanthanum are introduced after melting, and finally magnesium is introduced. The casting temperature is 1160-1180℃, and the casting speed is 50-100mm / min.

4. The preparation method according to claim 2, characterized in that, The hot rolling includes: heating the cast ingot to 750~850℃ and then hot rolling it, wherein the initial rolling temperature of the hot rolling is 700~750℃ and the final rolling temperature is above 450℃. The total processing rate of the hot rolling is 80% to 95%.

5. The preparation method according to claim 2, characterized in that, The first cold rolling process consists of 5 to 9 passes, with a single pass processing rate of 15% to 40% and a total processing rate of 75% to 90%.

6. The preparation method according to claim 2, characterized in that, The first annealing temperature is 400~500℃, and the holding time is 0.5~8h.

7. The preparation method according to claim 2, characterized in that, The second cold rolling process consists of 5 to 7 passes, with a single pass processing rate of 20% to 35% and a total processing rate of 60% to 80%.

8. The preparation method according to claim 2, characterized in that, The second annealing temperature is 400~450℃, and the holding time is 1~8h.

9. The preparation method according to claim 2, characterized in that, The third cold rolling process consists of 2 to 3 passes, with a single pass processing rate of 10% to 25% and a total processing rate of 30% to 45%.

10. The application of the oxygen-free copper strip according to claim 1 in the fabrication of IGBT modules.

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