Copper sheet material

Abstract

Provided is a copper sheet material that maintains excellent electrical conductivity and heat resistance, does not completely soften but maintains a certain hardness even when repeatedly heated at approximately 250°C after being heated to approximately a soldering temperature, undergoes low thermal stress, and has excellent peel resistance. The copper sheet material has a Cu content of 99.98 mass% or more, a total content of at least one element selected from the group consisting of Ti, Mn, Co, Ni, V, Zr, Cr, and Mg of 5-28 ppm by mass, a cube orientation area fraction after heating at 400°C for 30 minutes of 29% or more, and an electrical conductivity of 99% IACS or more.

Description

Copper sheet material

[0001] This disclosure relates to copper sheet material.

[0002] Generally, in power devices, a large amount of heat is generated due to the use of high voltage and large current, and the accompanying deterioration of materials has become an issue. Since such issues lead to damage to electrical and electronic device components, improvement of the heat resistance of materials is required. In semiconductor devices, pure copper sheet materials with high conductivity and excellent heat dissipation are used.

[0003] For example, in Patent Document 1, as a copper material suitable for parts for electronic and electrical equipment such as bus bars and heat dissipation substrates, the purity of Cu is 99.96 mass% or more, the ratio W / t of the plate width W to the plate thickness t is 10 or more, the conductivity is 97.0% IACS or more, the ratio B / A of the average crystal grain size A at the center of the plate thickness to the average crystal grain size B at the surface layer of the plate thickness is 0.80 or more and 1.20 or less, and the average crystal grain size A at the center of the plate thickness is 25 μm or less, a slit copper material is described.

[0004] Regarding pure copper sheet materials, since strain is introduced, they have a certain strength after manufacturing. However, after being press-processed into a predetermined size and then exposed to a high temperature around 300 °C during soldering. Since pure copper has a low softening temperature, depending on the heating temperature during soldering, relaxation of strain and recrystallization due to the recovery of dislocations proceed, and it softens. As a result, during the heat cycle in chip heating after soldering and during subsequent use, warping of the pure copper sheet material occurs, and furthermore, solder cracking is likely to occur.

[0005] In recent years, in order to improve heat dissipation against the increasing heat generation amount, the tendency of thickening the sheet material is remarkable. In order to suppress peeling at the bonding interface between the sheet material and different materials, a sheet material with small thermal expansion is required during heat generation such as soldering.

[0006] Generally, the magnitude of thermal stress is proportional to Young's modulus; therefore, the smaller the Young's modulus, the smaller the thermal stress, and the less likely delamination is to occur at dissimilar material interfaces, such as solder joint interfaces, in sheet metal. For this reason, materials with a low Young's modulus are preferred for sheet metal. However, the Young's modulus of typical pure copper is high, around 125 GPa, making it prone to delamination at dissimilar material interfaces. Copper sheet metals that address this situation and suppress delamination during soldering and subsequent heat generation during use have not yet been sufficiently developed.

[0007] Furthermore, with the increasing heat generation of power modules in recent years, there is a trend towards thicker pure copper plates for heat spreaders, making it important to lower the Young's modulus of thick plates. However, as the plate thickness increases, the Young's modulus of the plate material tends to increase. This is because, in the case of plates thicker than 1 mm, the cold working rate decreases, resulting in a significant decrease in the Cube orientation, which is an effective crystal orientation for lowering Young's modulus.

[0008] No copper plate material with such a thick plate and a sufficiently high cube orientation has been reported. Furthermore, while Patent Document 1 describes a copper material with a heat resistance temperature of 150°C or higher achieved by adding Mg, no copper plate material has been developed that possesses excellent high conductivity of 99% IACS or higher, high heat resistance to soldering temperatures, and excellent thermal cycling characteristics with a low Young's modulus that takes into account the heat generated during use.

[0009] Japanese Patent Publication No. 2022-69413

[0010] The purpose of this disclosure is to provide a copper plate material that maintains excellent conductivity and heat resistance, does not completely soften even when heated to around soldering temperature and then repeatedly heated to around 250°C, maintains a certain hardness, generates little thermal stress, and has excellent peel resistance.

[0011] [1] A copper plate material having a Cu content of 99.98 mass% or more, a total content of at least one element selected from the group consisting of Ti, Mn, Co, Ni, V, Zr, Cr, and Mg of 5 mass ppm or more and 28 mass ppm or less, an area ratio of the cube orientation after heating at 400°C for 30 minutes of 29% or more, and an electrical conductivity of 99% IACS or more. [2] The copper plate material according to [1] above, wherein the Young's modulus (Y1) in the direction parallel to rolling before heating is 65 GPa or more and 110 GPa or less, and the change in Young's modulus (Y1-Y2) from the Young's modulus (Y1) to the Young's modulus (Y2) in the direction parallel to rolling after heating at 400°C for 30 minutes of 30 minutes is within ±10 GPa. [3] The copper plate material according to [1] or [2] above, wherein the residual resistance ratio is 100 or more and 220 or less. [4] The copper plate material according to any one of [1] to [3] above, wherein the area ratio of the cube orientation after heating at 400°C for 30 minutes is 40% or more. [5] The copper plate material according to any one of [1] to [4] above, wherein the heat resistance temperature is 320°C or higher. [6] The copper plate material according to any one of [1] to [5] above, wherein the Vickers hardness after heating at 50°C to 500°C is 70 HV or higher. [7] The copper plate material according to any one of [1] to [6] above, wherein the average grain size on the rolled surface of the copper plate material is 80 μm or more.

[0012] According to this disclosure, it is possible to provide a copper plate material that maintains excellent conductivity and heat resistance, does not completely soften even when heated to around soldering temperature and then repeatedly heated to around 250°C, maintains a certain hardness, generates little thermal stress, and has excellent peel resistance.

[0013] The embodiments will be described in detail below.

[0014] The inventors of this invention have conducted extensive research on copper plate materials and have found that if a copper plate material has a predetermined composition and the area ratio of the cube orientation and the conductivity of the copper plate material after heating at 400°C for 30 minutes are within a predetermined range, the copper plate material maintains excellent conductivity and heat resistance, and even when heated to around soldering temperature and then repeatedly heated at around 250°C, it does not completely soften, maintains a certain hardness, generates little thermal stress, and exhibits excellent peel resistance. Based on these findings, the inventors have completed the present invention.

[0015] The copper plate material of the embodiment has a Cu content of 99.98 mass% or more, a total content of at least one element selected from the group consisting of Ti, Mn, Co, Ni, V, Zr, Cr, and Mg of 5 mass ppm or more and 28 mass ppm or less, an area ratio of the cube orientation after heating at 400°C for 30 minutes of 29% or more, and an electrical conductivity of 99% IACS or more.

[0016] In the copper plate material of the above embodiment, the Cu (copper) content is 99.98 mass% or more, preferably 99.99 mass% or more. If the Cu content is less than 99.98 mass%, the thermal conductivity of the copper plate material decreases, the desired heat dissipation cannot be obtained, the Cube orientation does not develop easily, and the Young's modulus of the copper plate material increases.

[0017] Furthermore, in the copper sheet material, the total content of at least one element selected from the group consisting of Ti (titanium), Mn (manganese), Co (cobalt), Ni (nickel), V (vanadium), Zr (zirconium), Cr (chromium), and Mg (magnesium) is 5 mass ppm or more and 28 mass ppm or less, preferably 12 mass ppm or more and 25 mass ppm or less. When the total content is within the above range, a copper sheet material can be obtained that maintains high conductivity, has excellent heat resistance, a high area ratio of the cube orientation before heating and after heating at 400°C for 30 minutes (hereinafter also simply referred to as "after heating"), and a low Young's modulus.

[0018] Furthermore, the area ratio of the Cube orientation of the copper plate material after heating it at 400°C for 30 minutes is 29% or more, preferably 40% or more, and more preferably 45% or more. The Cube orientation is the orientation that shows {1 0 0} < 0 0 1 >. If the area ratio of the Cube orientation of the copper plate material after heating is within the above range, the increase in the Young's modulus of the copper plate material can be suppressed, and therefore the occurrence of delamination at the bonding interface between the copper plate material and dissimilar materials can be suppressed.

[0019] Furthermore, the upper limit of the area ratio of the Cube orientation of the copper plate material after heating at 400°C for 30 minutes is, for example, 95% or less. If the area ratio of the Cube orientation after heating is greater than 95%, the mechanical strength and elongation of the copper plate material will decrease, and the copper plate material may not be suitable depending on the application.

[0020] Furthermore, for the same reasons as above, the area ratio of the copper plate material in the Cube orientation (copper plate material before heating) is preferably 45% or more, more preferably 50% or more. Also, the upper limit of the area ratio of the copper plate material in the Cube orientation is, for example, 95% or less.

[0021] The area ratio of the cube orientation of the copper plate material can be obtained from crystal orientation analysis data calculated using analysis software (TSL Corporation, OIM Analysis) from crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning electron microscope (JEOL Ltd., JSM-7001FA). "EBSD" is an abbreviation for Electron BackScatter Diffraction, and is a crystal orientation analysis technique that utilizes backscattered electron Kikuchi line diffraction that occurs when an electron beam is irradiated onto a copper plate material sample in a scanning electron microscope (SEM). "OIM Analysis" is analysis software for data measured by EBSD.

[0022] For the observation portion of the copper plate material, a cross-section of the copper plate material embedded in resin and finished from the surface by mechanical polishing and buffing (colloidal silica) is acceptable. However, from the viewpoint of ensuring quantitative accuracy through measurement over a wide area, it is preferable that the surface of the copper plate material be mirror-finished by electrolytic polishing.

[0023] The measurement is performed in a measurement area of ​​approximately 2000 μm square on the surface of the copper plate material, with a scan step size of 0.2 μm. The area of ​​the atomic plane of crystal grains having a deviation angle of 10° or less from the ideal orientation {1 0 0} < 0 0 1 > is determined, and by dividing this area by the total measurement area, the area ratio of crystal grains in the cube orientation can be obtained. Furthermore, if the measurement is performed on the cross-section of the copper plate material, measurements are performed in three or more different measurement areas, and the average value of the obtained values ​​is taken as the area ratio of crystal grains in the cube orientation.

[0024] Furthermore, the conductivity of the copper plate material is 99% IACS or higher, preferably 100% IACS or higher. If the conductivity of the copper plate material is less than 99% IACS, the thermal conductivity of the copper plate material decreases, and the heat dissipation performance of the copper plate material tends to deteriorate.

[0025] Furthermore, the Young's modulus (Y1) of the copper sheet material in the direction parallel to rolling before heating is preferably 65 GPa or more and 110 GPa or less, and more preferably 70 GPa or more and 100 GPa or less. When the Young's modulus (Y1) in the direction parallel to rolling is within the above range, thermal expansion during high-temperature heating is suppressed, and delamination at the dissimilar material interface in the copper sheet material can be further reduced.

[0026] Furthermore, the change in Young's modulus (Y1-Y2) from the Young's modulus of the copper sheet material in the rolling direction parallel to the heating (Y1) before heating to the Young's modulus of the copper sheet material in the rolling direction parallel to the heating (Y2) after heating at 400°C for 30 minutes is preferably within ±10 GPa, and more preferably within ±5 GPa. When the change in Young's modulus (Y1-Y2) is within the above range, thermal expansion during high-temperature heating is suppressed, delamination at the dissimilar material interface in the copper sheet material can be further reduced, and a small Young's modulus can be maintained even after heating, resulting in excellent thermal cycle characteristics.

[0027] Furthermore, the inventors have revealed that controlling the residual resistance ratio (RRR), that is, controlling the amount of solid solution and precipitation of elements other than Cu in the Cu matrix, facilitates the development of cube orientations effective for low Young's modulus. Controlling the residual resistance ratio requires controlling the solid solution and precipitation state of at least one element selected from the group consisting of trace additive elements Ti, Mn, Co, Ni, V, Zr, Cr, and Mg. As a result of various studies, the residual resistance ratio of the copper plate material after sufficient strain removal is preferably 100 to 220, more preferably 130 to 190. The inventors have revealed that when the residual resistance ratio of the copper plate material is within the above range, it is possible to obtain a copper plate material with suppressed conductivity reduction, excellent heat resistance, a high area ratio of cube orientations before and after heating, and a low Young's modulus.

[0028] Furthermore, the higher the heat resistance temperature of the copper sheet material, the less likely it is to soften when exposed to high temperatures, resulting in less warping of the copper sheet material. This further reduces the likelihood of delamination at the interface between the copper sheet material and other materials. From this perspective, it is preferable that the heat resistance temperature of the copper sheet material be 320°C or higher. While there is no particular upper limit to the heat resistance temperature, it is preferable that it be 500°C or lower considering the manufacturability of the copper sheet material. The higher the heat resistance temperature of the copper sheet material, the more difficult it becomes to homogenize the structure in the hot rolling process, requiring higher processing rates and temperatures, which increases the load on the equipment. The heat resistance temperature of the copper sheet material is measured in accordance with the Japan Copper Association Technical Standard JCBA T325:2013.

[0029] Furthermore, the inventors have found through various studies that, in order to ensure stable use of copper plate material for power semiconductors against soldering and heat generation during use at temperatures of approximately 200 to 300°C, it is preferable that the Vickers hardness of the copper plate material after heating at temperatures between 50°C and 500°C is 70 HV or higher. From this perspective, although the soldering temperature is at most around 350°C, in order for the copper plate material to maintain stable heat resistance during the subsequent heat generation and cooling cycles during use, it is preferable that the copper plate material has a Vickers hardness of 70 HV or higher after heating at temperatures between 50°C and 500°C. The above Vickers hardness of the copper plate material is measured using a test load of 1.96 N, in accordance with the micro-Vickers hardness test method specified in JIS Z 2244, for copper plate material heated at 500°C for 5 minutes.

[0030] Furthermore, the average grain size of the crystal grains on the rolled surface of the copper sheet material is preferably 80 μm or more, and more preferably 100 μm or more. When the average grain size of the copper sheet material is 80 μm or more, the crystal orientation can be sufficiently controlled, and the heat resistance properties are further improved.

[0031] As described above, the copper plate material of the embodiment maintains excellent conductivity and heat resistance, and even when subjected to repeated heating at around 250°C after soldering, it does not completely soften but maintains a certain hardness, generates little thermal stress, and has excellent peel resistance. Therefore, it is suitable as a heat dissipation plate material for power modules, such as a copper plate material for heat dissipation of power semiconductors, especially a thick copper plate material for heat dissipation.

[0032] Next, a method for manufacturing the copper sheet material of the above embodiment will be described. The copper sheet material of the above embodiment can be manufactured by sequentially performing the following steps: melting and casting [step 1], homogenization heat treatment and hot rolling [step 2], continuous two-stage aging heat treatment [step 3], cold rolling [step 4], recrystallization heat treatment [step 5], and temper rolling [step 6].

[0033] In melting and casting [Step 1], copper material and additive elements are melted and cast to obtain a copper ingot having a predetermined composition. For example, melting is carried out in an inert gas atmosphere or vacuum using a high-frequency melting furnace. Casting conditions are set as appropriate. For mass production, continuous casting is preferred.

[0034] In the homogenization heat treatment and hot rolling [Step 2] performed after melting and casting [Step 1], the copper ingot obtained in melting and casting [Step 1] is subjected to a heat treatment in which it is held at a predetermined temperature for a predetermined time to homogenize it, and then hot rolling is performed under conditions that cause dynamic recrystallization. For the heat treatment conditions of the homogenization heat treatment, it is preferable that the heating temperature is in the range of 500°C to 1000°C and the heating time is in the range of 1 hour to 10 hours. Furthermore, for the hot rolling conditions, it is preferable that it is accompanied by dynamic recrystallization and the total processing rate is in the range of 50% to 99%. In this way, the material structure is made uniform.

[0035] In this specification, the reduction ratio is the value obtained by subtracting the cross-sectional area after rolling from the cross-sectional area before rolling, dividing the result by the cross-sectional area before rolling, multiplying by 100, and expressing it as a percentage, and is represented by the following formula (1).

[0036] Processing rate = {([Cross-sectional area before rolling] - [Cross-sectional area after rolling]) / [Cross-sectional area before rolling]} × 100 (%) Equation (1)

[0037] In the continuous two-stage aging heat treatment [Step 3], which is performed after the homogenization heat treatment and hot rolling [Step 2], the first and second heat treatments are performed as a continuous two-stage aging heat treatment with controlled heating and cooling rates. By performing the continuous two-stage heat treatment under the following conditions, the size and number of precipitates of additive elements and impurity elements can be controlled. As a result, high conductivity and heat resistance, as well as a residual resistance ratio within a predetermined range, can be obtained.

[0038] In the first heat treatment of the two-stage aging heat treatment, it is held at 420°C or higher and 580°C or lower for 1 hour or longer and 6 hours or shorter. When heating from room temperature, in the temperature range of 300°C or higher, the heating rate is 5°C / second or lower.

[0039] In the second heat treatment performed after the first heat treatment, it is continuously held in the same furnace after the first heat treatment at 180°C or higher and 300°C or lower for 4 hours or longer and 12 hours or shorter. The cooling rate from the holding temperature of the first heat treatment to the holding temperature of the second heat treatment is 0.5°C / second or lower. Thus, the residual resistivity is controlled.

[0040] In the cold rolling [Process 4] performed after the continuous two-stage aging heat treatment [Process 3], cold rolling is performed. The total rolling reduction of the cold rolling is preferably 60% or higher and 99% or lower.

[0041] In the recrystallization heat treatment [Process 5] performed after the cold rolling [Process 4], a heat treatment in which recrystallization occurs is performed. The heat treatment conditions are preferably 200°C or higher and 550°C or lower for 30 seconds or longer and 600 seconds or shorter.

[0042] The temper rolling [Process 6] performed after the recrystallization heat treatment [Process 5] is a process for adjusting the strength, and may not be performed if the strength is not required. That is, the temper rolling [Process 6] is an optional process. The rolling reduction of the temper rolling is preferably more than 0% and 35% or lower. The thickness of the copper plate is not particularly limited, but is preferably 0.1 mm or more and 5.0 mm or less, more preferably 0.1 mm or more and 4.0 mm or less.

[0043] According to the embodiment described above, by controlling the area ratio of the Cube orientation of the copper plate and the conductivity within a predetermined range after heating at 400°C for 30 minutes with a predetermined composition, the copper plate maintains excellent conductivity and heat resistance, and even when repeatedly heated at about 250°C after heating at about the soldering temperature, it does not completely soften and maintains a certain hardness, the generated thermal stress is small, and the peel resistance can be excellent.

[0044] Although the embodiment has been described above, the present invention is not limited to the above embodiment, includes all aspects included in the concept of the present disclosure and the scope of the claims, and can be variously modified within the scope of the present disclosure.

[0045] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0046] (Examples 1 to 14 and Comparative Examples 1 to 6) In the melting and casting [Step 1], a copper ingot having the component composition shown in Table 1 was obtained by melting a copper material and additive elements using a high-frequency melting furnace and casting the molten metal. Subsequently, in the homogenization heat treatment and hot rolling [Step 2], the copper ingot obtained in the melting and casting [Step 1] was subjected to a homogenization heat treatment under heat treatment conditions of 500°C or higher and 1000°C or lower for 1 hour or longer and 10 hours or shorter, and then hot rolling with a total reduction ratio of 50% or higher and 98% or lower was performed to make the material structure uniform. Subsequently, in the continuous two-step aging heat treatment [Step 3], a continuous two-step aging heat treatment with controlled heating and cooling rates was performed. In the first heat treatment of the continuous two-step aging heat treatment [Step 3], heat treatment was performed under the conditions shown in Table 2, and when heating from room temperature, the heating rate was set to 5°C / second or lower in the temperature range of 300°C or higher. In the second heat treatment performed after the first heat treatment, heat treatment was continuously performed under the conditions shown in Table 2 in the same furnace after the first heat treatment, and the cooling rate from the holding temperature of the first heat treatment to the holding temperature of the second heat treatment was set to 0.5°C / second or lower. Subsequently, in the cold rolling [Step 4], cold rolling with a total reduction ratio of 60% or higher and 99% or lower was performed. Subsequently, in the recrystallization heat treatment [Step 5], recrystallization heat treatment was performed under heat treatment conditions of 200°C or higher and 550°C or lower for 30 seconds or longer and 600 seconds or shorter. In the temper rolling [Step 6], temper rolling with a rolling ratio of more than 0% and 35% or lower was performed. Thus, a copper sheet having a thickness of 1.2 mm was obtained. In Comparative Example 4, the first heat treatment of the continuous two-step aging heat treatment [Step 3] was not performed. In Comparative Example 5, the second heat treatment of the continuous two-step aging heat treatment [Step 3] was not performed. In Comparative Example 6, the continuous two-step aging heat treatment [Step 3] was not performed.

[0047]

[0048]

[0049] [Measurement and Evaluation] The copper sheets obtained in the above examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Tables 1 and 3.

[0050] [1] Component analysis: The component composition of each element in the copper plate material was analyzed using a glow discharge mass spectrometer (GDMS).

[0051] [2] Conductivity The conductivity of the copper plate material was calculated from the resistivity values ​​measured by the four-terminal method in a constant temperature bath maintained at 20°C (±0.5°C).

[0052] [3] Average grain size The average grain size of the crystal grains on the rolled surface of the copper sheet material was measured in accordance with the cutting method of JIS H 0501.

[0053] [4] Residual Resistivity Ratio The residual resistance ratio (RRR) of the copper plate material is the electrical resistance ρ of the copper plate material at room temperature (293K). ２９３Ｋ , and the electrical resistance ρ of copper plate material under liquid helium (4.2 K) ４．２Ｋ The values ​​were measured using the four-terminal method, and RRR = ρ ２９３Ｋ / ρ ４．２Ｋ The result was calculated using the following formula. To minimize the influence of processing distortion, samples heat-treated at 600°C for 60 minutes were used for measurement.

[0054] [5] Area ratio of Cube orientation The area ratio of the Cube orientation {1 0 0} <0 0 1> of the copper plate material was obtained from crystal orientation analysis data calculated using analysis software (TSL Corporation, OIM Analysis) from crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning analytical electron microscope (JEOL Ltd., JSM-7001FA). The surface of the copper plate material that was mirror-finished by electropolishing was used as the observation area. The measurement was performed in a measurement area of ​​approximately 2000 μm square on the above surface of the copper plate material with a scan step size of 0.2 μm. The area of ​​the atomic plane of crystal grains having a deviation angle of 10° or less from the ideal orientation {1 0 0} <0 0 1> was determined, and the area ratio of crystal grains with the Cube orientation was obtained by dividing this area by the total measurement area.

[0055] [6] Young's modulus (Y1) and (Y2) Three strip-shaped test pieces, 10 mm wide and 42 mm long, were taken from the copper sheet material along the direction parallel to the rolling process. The Young's modulus of the test pieces in the direction parallel to the rolling process was measured using a Young's modulus measuring device (JE-RT, manufactured by Nippon Techno Plus Co., Ltd.) by the free resonance method, and the average value was taken as the Young's modulus of the copper sheet material in the direction parallel to the rolling process.

[0056] [7] Heat resistance temperature In accordance with the Japan Copper Association Technical Standard JCBA T325:2013, the heating temperature at which the Vickers hardness of the copper plate material decreased to 80% of the initial value (before heating) was defined as the heat resistance temperature of the copper plate material.

[0057] [8] Vickers hardness The Vickers hardness of copper plates heated at 500°C for 5 minutes was measured with a test load of 1.96 N in accordance with the micro-Vickers hardness test method specified in JIS Z 2244. The measurement position was the rolled surface of the copper plate.

[0058] [9] Thermal Cycle Characteristics The thermal cycle characteristics were evaluated using Young's modulus and Vickers hardness as material properties required for copper plates used in power semiconductors. The thermal cycle test of the copper plate material was performed as follows. First, simulating soldering, the plate was heated to 400°C for 5 minutes, which is sufficiently higher than the actual processing temperature. Then, simulating the heat generation at specifications, the plate was heated from room temperature to 250°C at a heating rate of 1°C / sec to 50°C / sec and held for 10 minutes, and then cooled to room temperature at a cooling rate of 1°C / sec to 50°C / sec. This process was considered one cycle and was performed 100 times. After 100 cycles, the Young's modulus and Vickers hardness of the copper plate material were measured in the same manner as above. If the Young's modulus is 105 GPa or less and the Vickers hardness is 70 HV or more, it can be estimated that there is sufficient stable delamination resistance at the bonding interface.

[0059]

[10] Overall Evaluation The overall evaluation was ranked according to the following criteria: A: The copper plate material after the thermal cycling test had a Young's modulus of 95 GPa or less and a Vickers hardness of 70 HV or more. B: The copper plate material after the thermal cycling test had a Young's modulus greater than 95 GPa and 110 GPa or less and a Vickers hardness of 70 HV or more. C: The copper plate material after the thermal cycling test had a Young's modulus greater than 110 GPa and a Vickers hardness of less than 70 HV, or at least one of the above.

[0060]

[0061] As shown in Tables 1 to 3, in Examples 1 to 14, the area ratio of the cube orientation and the conductivity of the copper plate material having a predetermined composition and heated at 400°C for 30 minutes were controlled within a predetermined range. As a result, a copper plate material was obtained that maintained excellent conductivity and heat resistance, and did not completely soften even when repeatedly heated at around 250°C after heating at soldering temperature, maintaining a certain hardness, generating small thermal stresses, and exhibiting excellent peel resistance. Furthermore, a low Young's modulus was achieved by sufficiently developing the cube orientation, while simultaneously achieving excellent conductivity. As a result, a copper plate material for heat dissipation with excellent heat resistance and a low Young's modulus was obtained.

[0062] On the other hand, Comparative Examples 1 to 6 failed to satisfy at least one of the following conditions: having a predetermined composition, and controlling the area ratio of the Cube orientation and conductivity of the copper plate material after heating at 400°C for 30 minutes within a predetermined range. As a result, it was not possible to obtain a copper plate material that maintained excellent conductivity and heat resistance, did not completely soften even after repeated heating at around 250°C after heating at around soldering temperature, maintained a certain hardness, generated low thermal stress, and had excellent peel resistance. In particular, in Comparative Example 1, the Cube orientation developed before heating, and the Young's modulus before heating was low. However, because it did not contain additive elements, it had low heat resistance, a low area ratio of the Cube orientation after heating, and a large increase in Young's modulus after the thermal cycle test. In Comparative Examples 2 to 3, the total content of additive elements was outside the range of 5 mass ppm to 28 mass ppm, so the Cube orientation did not develop and the Young's modulus was high. In Comparative Examples 4 to 6, because the continuous two-stage aging heat treatment under the specified conditions was not performed, at least one of the requirements for high conductivity and residual resistance ratio within the specified range was not met. As a result, the area ratio of the cube orientation after heating was low, and the Young's modulus increased after the thermal cycling test.

Claims

1. A copper plate material having a Cu content of 99.98 mass% or more, a total content of at least one element selected from the group consisting of Ti, Mn, Co, Ni, V, Zr, Cr, and Mg of 5 mass ppm or more and 28 mass ppm or less, a cube orientation area ratio of 29% or more after heating at 400°C for 30 minutes, and an electrical conductivity of 99% IACS or more.

2. The copper plate material according to claim 1, wherein the Young's modulus (Y1) in the direction parallel to rolling before heating is 65 GPa or more and 110 GPa or less, and the change in Young's modulus (Y1-Y2) from the Young's modulus (Y1) to the Young's modulus (Y2) in the direction parallel to rolling after heating at 400°C for 30 minutes is within ±10 GPa.

3. The copper plate material according to claim 1, wherein the residual resistance ratio is 100 or more and 220 or less.

4. The copper plate material according to claim 1, wherein the area ratio of the cube orientation after heating at 400°C for 30 minutes is 40% or more.

5. The copper plate material according to claim 1, wherein the heat resistance temperature is 320°C or higher.

6. The copper plate material according to claim 1, wherein the Vickers hardness after heating to a temperature of 50°C or higher and 500°C or lower is 70 HV or higher.

7. The copper sheet material according to any one of claims 1 to 6, wherein the average grain size on the rolled surface of the copper sheet material is 80 μm or more.

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