Copper material and insulating substrate

Abstract

A copper material, wherein: the Cu content is 99.9 mass% or more; the electrical conductivity is 95% IACS or more; and in a cross section orthogonal to the plate thickness direction, if a crystal orientation distribution function obtained from texture analysis by EBSD is represented by Euler angles (ϕ1, Φ, ϕ2), the average value of the orientation densities at ϕ1=30-45°, Φ=40-50°, ϕ2=0° is 3.0 or more, and the average value of the orientation densities at ϕ1=20-35°, Φ=90°, ϕ2=45° is 1.4 or less.

Description

Copper material and insulating substrate

[0001] The present invention relates to a copper material suitable for electrical and electronic components such as heat sinks and thick copper circuits, and more particularly to a copper material used in insulating substrates for power semiconductors, and to an insulating substrate using this copper material. This application claims priority based on Japanese Patent Application No. 2024-192640, filed in Japan on November 1, 2024, the contents of which are incorporated herein by reference.

[0002] Traditionally, highly conductive copper materials have been used in electrical and electronic components such as heat sinks and thick copper circuits. Recently, with the increasing amount of current used in electrical and electronic equipment components, resistive heating has become a problem. In electronic devices such as semiconductor devices, for example, insulating substrates are used in which copper material is bonded to a ceramic substrate to form the aforementioned heat sinks and thick copper circuits.

[0003] When bonding ceramic substrates and copper materials, a high-temperature, high-pressure treatment is performed. This can lead to coarsening or uneven growth of the copper grain size, resulting in poor bonding, poor appearance, and problems during the inspection process. To solve this problem, the copper material is required to have minimal and uniform grain size changes even after heat treatment.

[0004] For example, Patent Documents 1 and 2 propose techniques for suppressing crystal growth in copper materials. Patent Document 1 states that by including 0.0006 to 0.0015 wt% of S, it is possible to adjust the crystal grain size to a certain level even when heat-treated at a temperature above the recrystallization temperature. Patent Document 2 states that by including Ca and specifying the ratio of Ca content to the total content of O, S, Se, and Te, it is possible to suppress the coarsening of crystal grains even when heat-treated at 800°C.

[0005] Japanese Patent Application Publication No. 06-002058 (A) International Publication No. 2020 / 203071

[0006] Incidentally, while Patent Documents 1 and 2 describe a configuration that suppresses grain coarsening by controlling the composition, this tends to reduce strength, potentially leading to sagging and burrs during punching, and making it difficult to produce parts with good dimensional accuracy. Furthermore, there is a risk of manufacturing problems such as surface scratches and deformation during transport. On the other hand, if one attempts to improve material strength in order to improve scratch resistance, deformation resistance, and dimensional accuracy (punching ability), high strain energy accumulates in the material, causing grain coarsening when held at high temperatures.

[0007] This invention has been made in view of the circumstances described above, and aims to provide a copper material that can suppress grain coarsening and non-uniformity even when held at high temperatures, and that has excellent scratch resistance, deformation resistance, and high dimensional accuracy, as well as an insulating substrate using this copper material.

[0008] To solve this problem, the inventors conducted diligent research and obtained the following findings. When copper material is heat-treated, crystal growth occurs through primary recrystallization at low temperatures and secondary recrystallization at higher temperatures during the heating process. By sufficiently releasing strain energy through primary recrystallization at low temperatures, it is possible to suppress excessive crystal growth during secondary recrystallization at high temperatures, thereby suppressing grain coarsening and non-uniformity. Furthermore, by appropriately controlling the microstructure of the copper material, it is possible to promote primary recrystallization at low temperatures.

[0009] The present invention is based on the above-mentioned findings, and the copper material of embodiment 1 of the present invention is characterized in that the Cu content is 99.9 mass% or more, the conductivity is 95% IACS or more, and when the crystal orientation distribution function obtained from texture analysis by EBSD in a cross section perpendicular to the thickness direction is expressed in terms of Euler angles (φ1, Φ, φ2), the average value of the orientation density at φ1: 30 to 45°, Φ: 40 to 50°, and φ2: 0° is 3.0 or more, and the average value of the orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45° is 1.4 or less.

[0010] According to the copper material of Embodiment 1 of the present invention, the Cu content is 99.9 mass% or more, and the conductivity is 95% IACS or more, so it has particularly excellent conductivity and heat dissipation, making it particularly suitable as a material for electronic and electrical equipment components used in high-current applications. Furthermore, in a cross section perpendicular to the thickness direction, the average orientation density at φ1: 30-45°, Φ: 40-50°, and φ2: 0° is 3.0 or more, and the average orientation density at φ1: 20-35°, Φ: 90°, and φ2: 45° is 1.4 or less, so primary recrystallization can proceed sufficiently in a low temperature range of 400°C or less, and furthermore, crystal growth due to secondary recrystallization at high temperatures can be suppressed. As a result, grain coarsening and non-uniformity at high temperatures can be suppressed. In addition, strain energy is not reduced more than necessary, resulting in high strength, excellent scratch resistance, deformation resistance, and high dimensional accuracy.

[0011] The copper material of embodiment 2 of the present invention is characterized in that, in the copper material of embodiment 1, when a boundary with an orientation difference of 5° or more in a cross section perpendicular to the thickness direction of the plate is defined as a grain boundary, the proportion of grain boundaries with an orientation difference of 10° or less is 4% or more. According to the copper material of embodiment 2 of the present invention, since grain boundaries with an orientation difference of 5° or more and 10° or less in a cross section perpendicular to the thickness direction of the plate have an energetically unstable structure, primary recrystallization at low temperatures can be further promoted, and grain coarsening and non-uniformity at high temperatures can be further suppressed.

[0012] The copper material of embodiment 3 of the present invention is characterized in that, in the copper material of embodiment 1 or embodiment 2, the average value of the KAM (Kernel Average Misorientation) in a cross section perpendicular to the thickness direction is 0.6 or higher. According to the copper material of embodiment 3 of the present invention, since the average value of the KAM in a cross section perpendicular to the thickness direction is set high at 0.6 or higher, scratch resistance, deformation resistance, and dimensional accuracy can be further improved. In addition, primary recrystallization in the low-temperature range can be further promoted, and grain coarsening and non-uniformity at high temperatures can be further suppressed.

[0013] The copper material of embodiment 4 of the present invention is characterized in that, in any one of the copper materials of embodiments 1 to 3, it contains one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag in a total amount of 10 mass ppm to 200 mass ppm. According to the copper material of embodiment 4 of the present invention, since it contains one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag in a total amount of 10 mass ppm to 200 mass ppm, the movement of grain boundaries can be suppressed by the solid solution of these additive elements in the copper matrix or by the fine dispersion of compounds, and it becomes possible to further reliably suppress grain growth during heat treatment.

[0014] The copper material of embodiment 5 of the present invention is characterized in that, in any one of the copper materials of embodiments 1 to 4, the tensile strength is 300 MPa or more. According to the copper material of embodiment 5 of the present invention, since the tensile strength is 300 MPa or more, the strength is sufficiently high, and scratch resistance, deformation resistance, and dimensional accuracy can be further improved.

[0015] An insulating substrate according to embodiment 6 of the present invention is an insulating substrate comprising a ceramic substrate and a copper plate bonded to at least one surface of the ceramic substrate, wherein the copper plate is made of one of the copper materials according to embodiments 1 to 5. According to the insulating substrate of embodiment 6 of the present invention, since the copper plate bonded to at least one surface of the ceramic substrate is made of one of the copper materials according to embodiments 1 to 5, the crystal grain growth of the copper plate is suppressed during bonding, resulting in a uniform crystal structure, and the copper plate has excellent scratch resistance, deformation resistance, and dimensional accuracy. Therefore, it can be used stably as an insulating substrate.

[0016] The insulating substrate of embodiment 7 of the present invention is characterized in that, in the insulating substrate of embodiment 6 of the present invention, the ceramic substrate is one of silicon nitride, alumina, or aluminum nitride. According to the insulating substrate of embodiment 7 of the present invention, since the ceramic substrate is composed of one of silicon nitride, alumina, or aluminum nitride, the insulating properties of the ceramic substrate are excellent, and it can be used stably as an insulating substrate.

[0017] The insulating substrate of embodiment 8 of the present invention is characterized in that, in the insulating substrate of embodiment 6 or embodiment 7 of the present invention, a plating layer is formed on the side of the copper plate opposite to the ceramic substrate. According to the insulating substrate of embodiment 8 of the present invention, since a plating layer is formed on the side of the copper plate opposite to the ceramic substrate, other members such as semiconductor elements and heat sinks can be well bonded to the copper plate, and various devices can be constructed.

[0018] According to the present invention, it is possible to provide a copper material that can suppress grain coarsening and non-uniformity even when held at high temperatures, and that has excellent scratch resistance, deformation resistance, and high dimensional accuracy, as well as an insulating substrate using this copper material.

[0019] This is a schematic diagram illustrating an electronic device using an insulating substrate according to this embodiment. This is a flow chart of the manufacturing method of copper material according to this embodiment.

[0020] Below, a copper material and an insulating substrate, which are embodiments of one embodiment of the present invention, will be described with reference to the attached drawings. The copper material of this embodiment is used as a material for electrical and electronic components such as heat sinks and thick copper circuits, and is bonded to a ceramic substrate, for example, when forming the aforementioned electrical and electronic components to constitute an insulating substrate.

[0021] Figure 1 shows an insulating substrate 10 and an electronic device 1 using this insulating substrate 10, which are embodiments of the present invention. The electronic device 1 shown in Figure 1 comprises the insulating substrate 10 according to this embodiment, an electronic component 3 bonded to one side of the insulating substrate 10 (upper side in Figure 1) via a first solder layer 2, and a heat sink 51 bonded to the other side of the insulating substrate 10 (lower side in Figure 1) via a second solder layer 8. In this embodiment, the electronic component 3 is a power semiconductor element, and the electronic device 1 is a power module.

[0022] The insulating substrate 10 comprises a ceramic substrate 11, a circuit layer 12 disposed on one surface of the ceramic substrate 11 (the upper surface in Figure 1), and a metal layer 13 disposed on the other surface of the ceramic substrate 11 (the lower surface in Figure 1).

[0023] The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13. The ceramic substrate 11 is made of silicon nitride (Si), which has excellent insulating and heat dissipation properties. ３ N ４ ), aluminum nitride (AlN), alumina (Al ２ O ３ It is made of ceramics such as ). In this embodiment, the ceramic substrate 11 is made of silicon nitride (Si), which has particularly excellent heat dissipation properties. ３ N ４ It is composed of the following. Furthermore, the thickness of the ceramic substrate 11 is set to a range of, for example, 0.2 mm or more and 1.5 mm or less, and in this embodiment it is set to 0.32 mm.

[0024] The circuit layer 12 is formed by bonding a copper plate to one side of the ceramic substrate 11. A circuit pattern is formed on this circuit layer 12, and one side of it (the top side in Figure 1) is the mounting surface on which the electronic component 3 is mounted. Preferably, a plating layer of, for example, Ni or Ag is formed on the side of the circuit layer 12 opposite to the ceramic substrate 11.

[0025] The metal layer 13 is formed by bonding a copper plate to the other side of the ceramic substrate 11. This metal layer 13 has the effect of efficiently transferring heat from the electronic component 3 to the heat sink 51. Preferably, a plating layer of, for example, Ni or Ag is formed on the side of the metal layer 13 opposite to the ceramic substrate 11.

[0026] Here, the copper plate forming the circuit layer 12 and the ceramic substrate 11, and the copper plate forming the metal layer 13 and the ceramic substrate 11 are joined by existing joining methods such as the DBC method and the AMB method. The temperature during joining is, for example, in the high-temperature range of 750°C or higher, which may cause grain coarsening and grain non-uniformity in the circuit layer 12 and the metal layer 13.

[0027] Therefore, in this embodiment, the copper plate that forms the circuit layer 12 and the copper plate that forms the metal layer 13 are made of the copper material of this embodiment.

[0028] The copper material of this embodiment has a Cu content of 99.9 mass% or more. Furthermore, the copper material of this embodiment may contain one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag in a total amount of 10 mass ppm to 200 mass ppm.

[0029] Furthermore, in the copper material of this embodiment, the conductivity is set to 95% IACS or higher. Although not particularly limited, the conductivity may be 102% IACS or lower.

[0030] In this embodiment of the copper material, when the crystal orientation distribution function obtained from texture analysis by EBSD is expressed in terms of Euler angles (φ1, Φ, φ2) in a cross section perpendicular to the thickness direction, the average orientation density at φ1: 30 to 45°, Φ: 40 to 50°, and φ2: 0° is 3.0 or higher, and the average orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45° is 1.4 or lower.

[0031] Furthermore, in the copper material of this embodiment, when a boundary with an orientation difference of 5° or more in a cross section perpendicular to the thickness direction of the plate is defined as a grain boundary, it is preferable that the proportion of grain boundaries with an orientation difference of 10° or less (i.e., grain boundaries with an orientation difference of 5° or more and 10° or less) is 4% or more.

[0032] Furthermore, in the copper material of this embodiment, it is preferable that the average value of the KAM (Kernel Average Misorientation) value in a cross-section perpendicular to the plate thickness direction is 0.6 or higher.

[0033] Furthermore, in the copper material of this embodiment, it is preferable that the tensile strength is 300 MPa or higher.

[0034] Herein, the reasons for specifying the Cu content, the content of various elements, the crystal orientation distribution function, the KAM value, the conductivity, and the tensile strength in the copper material of this embodiment, as described above, will be explained below.

[0035] (Cu content) In electrical and electronic components for high-current applications, excellent conductivity and heat dissipation are required to suppress heat generation during current flow. Therefore, it is preferable to use a high-purity copper material with particularly excellent conductivity and heat dissipation. Accordingly, in the copper material of this embodiment, the Cu content is specified to be 99.9 mass% or more. The lower limit of the Cu content is preferably 99.93 mass% or more, and more preferably 99.96 mass% or more. On the other hand, there is no particular upper limit on the Cu content, but it is preferably 99.9999 mass% or less, and more preferably 99.999 mass% or less.

[0036] (Total content of one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag) One or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag either solid-solve in the Cu matrix or form compounds with Cu and disperse finely, thereby inhibiting grain boundary movement. This further suppresses grain coarsening and grain non-uniformity when held at high temperatures. Therefore, in order to further suppress grain coarsening and grain non-uniformity when held at high temperatures, the copper material of this embodiment may contain one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag. On the other hand, if a large amount of these additive elements is included, the conductivity may decrease.

[0037] Therefore, in the copper material of this embodiment, if it contains one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag, it is preferable that the total content of these additive elements be within the range of 10 mass ppm to 200 mass ppm. Here, the lower limit of the total content of the above-mentioned additive elements is preferably 15 mass ppm or more, and more preferably 20 mass ppm or more. Furthermore, the upper limit of the total content of the above-mentioned additive elements is preferably 150 mass ppm or less, and more preferably 100 mass ppm or less. Note that if the above-mentioned additive elements are contained as impurities, the total content of the additive elements may be 10 mass ppm or less.

[0038] (Other impurities) Other unavoidable impurities besides Cu and the additive elements mentioned above include Al, As, B, Bi, Cd, Cr, Pb, V, Nb, Ta, Mo, W, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, Au, Hg, Tl, N, Li, etc. These unavoidable impurities may be present in amounts that do not affect the properties.

[0039] (Crystal Orientation Distribution Function) Euler angles represent the crystal orientation based on the relationship between the sample coordinate system and the crystal axes of individual crystal grains. The crystal orientation is expressed by rotating (φ1, Φ, φ2) around the (Z-X-Z) axis respectively from the state where the crystal axes (X-Y-Z) coincide. By expressing the ODF (orientation distribution function) by series expansion in three-dimensional Euler space, it becomes possible to confirm the distribution of crystal orientation density in the measurement range.

[0040] Here, in the copper material of this embodiment, when the crystal orientation distribution function obtained from the texture analysis by EBSD is represented by Euler angles (φ1, Φ, φ2) in a cross section orthogonal to the plate thickness direction, the average value of the orientation density at φ1: 30 to 45°, Φ: 40 to 50°, φ2: 0° is 3.0 or more, and the average value of the orientation density at φ1: 20 to 35°, Φ: 90°, φ2: 45° is 1.4 or less.

[0041] By setting the crystal orientation density as described above, the primary recrystallization of the copper material can occur at a lower temperature. Therefore, for example, the primary recrystallization proceeds sufficiently in a low temperature range of 400°C or lower, releasing strain energy to form a stable recrystallized structure. Subsequently, the secondary recrystallization in a high temperature range of 800°C or higher, for example, is suppressed, and it becomes possible to suppress the coarsening and non-uniformity of crystal grains. Also, without reducing the strain energy more than necessary, the strength becomes sufficiently high, and it has excellent scratch resistance, deformation resistance, and high dimensional accuracy.

[0042] In the copper material of this embodiment, the lower limit of the average value of the orientation density at φ1: 30 to 45°, Φ: 40 to 50°, φ2: 0° is preferably 3.3 or more, and more preferably 3.5 or more. On the other hand, although there is no particular limitation on the upper limit of the average value of the orientation density at φ1: 30 to 45°, Φ: 40 to 50°, φ2: 0°, it is preferably 20.0 or less, and more preferably 15.0 or less.

[0043] Also, in the copper material of the present embodiment, the upper limit of the average value of the orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45° is preferably 1.2 or less, and more preferably 1.0 or less. On the other hand, there is no particular limitation on the lower limit of the average value of the orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45°, but it is preferably 0.05 or more, and more preferably 0.1 or more.

[0044] (Ratio of grain boundaries with an orientation difference of 5° or more and 10° or less) Grain boundaries with an orientation difference of 5° or more and 10° or less between adjacent crystals generally have an energetically unstable structure. Here, after setting the Euler angles (φ1, Φ, φ2) within the above range, by making the ratio of grain boundaries with an orientation difference of 5° or more and 10° or less between adjacent crystals 4% or more of the whole, recrystallization in the low temperature range can be promoted, and coarsening and non-uniformity of crystal grains at high temperature can be further suppressed. In the copper material of the present embodiment, the lower limit of the ratio of grain boundaries with an orientation difference of 5° or more and 10° or less is more preferably 5% or more, and even more preferably 8% or more. On the other hand, there is no particular limitation on the upper limit of the ratio of grain boundaries with an orientation difference of 5° or more and 10° or less, but it is preferably 40% or less, and more preferably 30% or less.

[0045] (KAM value) The KAM (Kernel Average Misorientation) value measured by EBSD is calculated by averaging the orientation difference between one pixel and the surrounding pixels. Since the shape of the pixel is a regular hexagon, when the degree of proximity is set to 1, the average value of the orientation difference with six adjacent pixels is calculated as the KAM value. By using this KAM value, the local orientation difference, i.e., the strain distribution, can be visualized. In the copper material of this embodiment, if the average value of the KAM value is 0.6 or higher in a cross section perpendicular to the plate thickness direction, sufficient strain is present, the strength becomes sufficiently high, and it will have excellent scratch resistance, deformation resistance and high dimensional accuracy. Furthermore, primary recrystallization in the low temperature range can be further promoted, and grain coarsening and non-uniformity in the high temperature range can be further suppressed. In the copper material of this embodiment, the lower limit of the average KAM value is more preferably 0.8 or higher, and even more preferably 1.0 or higher. On the other hand, there is no particular limit to the upper limit of the average KAM value, but it is preferably 1.8 or lower, and more preferably 1.5 or lower.

[0046] (Conductivity) In electrical and electronic equipment components, excellent conductivity is required to suppress heat generation during current flow. For this reason, the copper material of this embodiment is specified to have a conductivity of 95% IACS or higher. Preferably, the conductivity of the copper material of this embodiment is 98% IACS or higher, and more preferably 100% IACS or higher.

[0047] (Tensile Strength) In electrical and electronic equipment components, miniaturization and thinning are progressing, and the materials that make up electrical and electronic equipment components are required to have excellent mechanical properties. For this reason, in the copper material of this embodiment, it is preferable that the tensile strength, which is one of the mechanical properties, is 300 MPa or more. More preferably, the lower limit of the tensile strength of the copper material of this embodiment is 330 MPa or more, and even more preferably 360 MPa or more. On the other hand, there is no particular upper limit to the tensile strength of the copper material of this embodiment, but it is preferable that it is 460 MPa or less, and more preferably 430 MPa or less.

[0048] Next, the method for manufacturing the copper material according to this embodiment, which has the above configuration, will be explained with reference to the flowchart shown in Figure 2.

[0049] (Melting and Casting Process S01) First, the molten copper obtained by melting oxygen-free copper raw material is adjusted by adding the aforementioned Group A elements and, if necessary, Group B elements. Individual elements or master alloys can be used for the addition of various elements. Alternatively, raw materials containing the above-mentioned elements may be melted together with the copper raw material. Here, it is preferable that each element has a purity of 99.9 mass% or higher, known as 3N, or 99.99 mass% or higher, known as 4N. During melting, to reduce the hydrogen concentration, H ２ It is preferable to perform atmospheric melting in an inert gas atmosphere with a low vapor pressure of oxygen (e.g., Ar gas), and to minimize the holding time during melting. Then, the molten copper with adjusted composition is poured into a mold to produce an ingot. When considering mass production, it is preferable to use a continuous casting method or a semi-continuous casting method.

[0050] (Solidifying Heat Treatment Step S02) The obtained ingot is subjected to a solidifying heat treatment in order to homogenize the segregated components within the material. It is preferable that the heat treatment temperature in the thermal treatment step S02 is 800°C or higher. It is also preferable that the holding time at 800°C or higher is 4 hours or more. By performing a solidifying heat treatment under these conditions, it is possible to suppress the segregation of various elements and achieve a homogeneous state without having to apply a high processing rate in the subsequent hot rolling process.

[0051] (Hot working process S03) Next, hot working is performed to form a dynamic recrystallized structure. In this hot working process S03, the objective is to obtain a dynamic recrystallized structure from the cast structure, so in order to create the structure, hot working is required in 1 to 3 passes with a total processing rate of 30% or less. Furthermore, by setting the processing temperature to 700°C or higher, a structure in the preliminary stage before creating the desired structure can be formed. The total processing rate is more preferably 25% or less, and more preferably 20% or less. Furthermore, the processing temperature is more preferably 720°C or higher, and more preferably 740°C or higher. The processing method is not particularly limited, but if the final shape is a plate or strip, rolling is preferred. For wires and rods, extrusion or groove rolling is preferred, and for bulk shapes, forging or pressing is preferred. By combining this with subsequent rolling and heat treatment processes, the desired structure can be obtained.

[0052] (Surface Machining Process S04) Surface machining is performed to remove the oxide film formed on the surface in the hot working process S03 described above. The surface machining allowance is preferably in the range of 0.5 mm to 3.0 mm.

[0053] (Plastic working process S05) Next, plastic working is performed with a processing rate of 85% or more. By applying plastic working with a processing rate of 85% or more to the recrystallized structure obtained in the hot working process S03, a crystal structure oriented in a specific direction can be obtained during the subsequent recrystallization process. By obtaining a crystal structure with a specific direction, a crystal structure with the aforementioned orientation density can be formed by subsequent heat treatment and processing. The processing method in the plastic working process S05 is not particularly limited, but rolling is used when the final form is a plate or strip. Other methods such as forging, pressing, and groove rolling may also be used. The processing temperature is also not particularly limited, but it is preferable to set it within the range of -200°C to 400°C, which is either cold or warm.

[0054] (First heat treatment step S06) Next, heat treatment is performed to create a crystalline structure. Here, it is preferable to perform the heat treatment in a non-oxidizing or reducing atmosphere. It is also preferable that the heat treatment temperature be in the range of 500°C to 900°C. Furthermore, it is preferable that the holding time at the heat treatment temperature be in the range of 1 minute to 60 minutes. It is also preferable to cool the material by adding water after the heat treatment. By performing this first heat treatment step S06, a crystalline structure oriented in a specific direction is formed. And by forming a crystalline structure oriented in a specific direction, it becomes possible to form the crystalline structure of the copper material of this embodiment in a later step.

[0055] (Intermediate rolling process S07) Next, rolling is applied with a rolling ratio of 70% to 90%. As described above, by applying rolling with a rolling ratio of 70% to 90% to a crystal structure oriented in a specific direction, new recrystallization nuclei are preferentially formed from the grain boundary interfaces during subsequent heat treatment, and a desirable crystal orientation can be grown.

[0056] (Second heat treatment step S08) Next, heat treatment is performed. Here, it is preferable to perform the heat treatment in a non-oxidizing or reducing atmosphere. It is also preferable that the heat treatment temperature be in the range of 500°C to 900°C. Furthermore, it is preferable that the holding time at the heat treatment temperature be in the range of 1 minute to 60 minutes. It is also preferable to cool the material by adding water after the heat treatment. By performing this second heat treatment step S08, it is possible to preferentially grow crystals in a preferred crystal orientation and form a preferred structure.

[0057] (Finishing Rolling Process S09) Next, rolling is applied to a predetermined rolling ratio in order to adjust the strength of the material. Preferably, the rolling ratio in the finishing rolling process S09 is 30% or more. This improves the strength of the material and suppresses recrystallization at high temperatures.

[0058] Through the processes described above, the copper material of this embodiment is produced.

[0059] According to the copper material of this embodiment, which has the above configuration, the Cu content is 99.9 mass% or more, and the conductivity is 95% IACS or more, so it has particularly excellent conductivity and heat dissipation properties, making it particularly suitable as a material for components of electronic and electrical equipment used in high-current applications.

[0060] Furthermore, in cross-sections perpendicular to the plate thickness direction, the average orientation density at φ1: 30-45°, Φ: 40-50°, and φ2: 0° is 3.0 or higher, and the average orientation density at φ1: 20-35°, Φ: 90°, and φ2: 45° is 1.4 or lower. Therefore, primary recrystallization can be sufficiently advanced in the low-temperature range of 400°C or below, and crystal growth due to secondary recrystallization at high temperatures can be suppressed. Thus, even when held at high temperatures, grain coarsening and non-uniformity can be suppressed. In addition, since the strain energy is not reduced more than necessary, it has high strength, excellent scratch resistance, deformation resistance, and high dimensional accuracy, making it suitable for use as a material for electronic and electrical equipment components.

[0061] In the copper material of this embodiment, when a boundary with an orientation difference of 5° or more in a cross section perpendicular to the thickness direction is defined as a grain boundary, if the proportion of grain boundaries with an orientation difference of 10° or less is 4% or more, then there are a relatively large number of grain boundaries with an orientation difference of 5° to 10° that have an energetically unstable structure. For example, primary recrystallization in the low temperature range of 400°C or less is further promoted, crystal growth in the high temperature range can be suppressed, and grain coarsening and non-uniformity at high temperatures can be further suppressed.

[0062] In the copper material of this embodiment, if the average value of the KAM (Kernel Average Misorientation) in a cross-section perpendicular to the thickness direction is 0.6 or higher, sufficient strain is present, the strength is sufficiently high, and scratch resistance, deformation resistance, and dimensional accuracy can be further improved. Furthermore, primary recrystallization can be further promoted in the low-temperature range, crystal growth can be suppressed in the high-temperature range, and grain coarsening and non-uniformity at high temperatures can be further suppressed.

[0063] In the copper material of this embodiment, if one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag are included in a total amount of 10 mass ppm to 200 mass ppm, the solid solution of these additive elements and the fine dispersion of compounds with Cu can suppress grain boundary movement, thereby suppressing crystal growth in high-temperature ranges and further suppressing grain coarsening and non-uniformity at high temperatures.

[0064] In the copper material of this embodiment, if the tensile strength is 300 MPa or higher, the strength is sufficiently high, and scratch resistance, deformation resistance, and dimensional accuracy can be further improved.

[0065] In this embodiment, the insulating substrate 10 has a ceramic substrate 11 and a copper plate bonded to the surface of the ceramic substrate 11 to form a circuit layer 12 and a metal layer 13. Since the copper plate that forms the circuit layer 12 and the metal layer 13 is made of the copper material of this embodiment, grain growth during bonding is suppressed, resulting in a uniform crystalline structure and stable use.

[0066] In the insulating substrate 10 of this embodiment, if the ceramic substrate 11 is silicon nitride, alumina, or aluminum nitride, the insulating properties of the ceramic substrate 11 are excellent, and it can be used stably.

[0067] In the insulating substrate 10 of this embodiment, if a plating layer is formed on either the side of the circuit layer 12 opposite to the ceramic substrate 11, or on either or both of the side of the metal layer 13 opposite to the ceramic substrate 11, the electronic component 3 can be well bonded to the circuit layer 12 and the heat sink 51 can be well bonded to the metal layer 13, thereby enabling the construction of the electronic device 1 shown in Figure 1.

[0068] Although an embodiment of the present invention, a copper material, has been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. For example, although an example of a method for manufacturing a copper material was described in the above embodiment, the method for manufacturing a copper material is not limited to that described in the embodiment, and an existing manufacturing method may be appropriately selected and used for manufacturing.

[0069] The results of the verification experiments conducted to confirm the effects of the present invention are described below.

[0070] Using a band melting refining method, copper raw materials consisting of pure copper with a purity of 99.99 to 99.999 mass% or higher were charged into a high-purity graphite crucible and high-frequency melted in an atmospheric furnace under an Ar gas atmosphere. The resulting molten copper was then mixed with 1-mass master alloys of various elements prepared using 6N (purity of 99.9999 mass% or higher) high-purity copper and 2N (purity of 99 mass% or higher) elements to adjust the composition. The mixture was then poured into an IsoWool (registered trademark) mold to produce ingots. The ingot size was approximately 100 mm thick x 100 mm wide x 150-200 mm long. The cooling rate for all samples was 0.1°C / sec or higher.

[0071] Table 1 shows the results of measuring the copper content and the content of various elements in the obtained ingots. Samples were taken from the obtained ingots. The sulfur (S) content was measured by infrared absorption spectroscopy, and the other elements were measured using glow discharge mass spectrometry (GD-MS). Measurements were taken at two locations: the center of the sample and the widthwise edge. The higher content was used as the sample's content.

[0072] The ingot obtained as described above was subjected to soaking heat treatment in an Ar gas atmosphere under the conditions shown in Table 2. Next, hot rolling was performed under the conditions shown in Table 2. After that, surface milling was performed to remove the oxide film. Next, rolling (plastic deformation) was performed under the conditions shown in Table 2. After that, a first heat treatment was performed in an Ar gas atmosphere under the conditions shown in Table 2. Next, intermediate rolling (plastic deformation) was performed under the conditions shown in Table 2. After that, a second heat treatment was performed in an Ar gas atmosphere under the conditions shown in Table 2. Finally, finish rolling was performed under the conditions shown in Table 2 to produce a strip material with a thickness of 0.8 mm (a strip material for character evaluation).

[0073] The following items were evaluated. The evaluation results are shown in Table 3.

[0074] (Orientation Density) After mechanical polishing the cross-section perpendicular to the thickness direction of the sample taken from the characteristic evaluation strip, using waterproof abrasive paper and diamond abrasive grains, finish polishing was performed using a colloidal silica solution. Then, using an EBSD measuring device (Hitachi High-Tech SU7000, EDAX / AMETEK Velocity Super, APEX EBSD Ver. 2.9) and analysis software (EDAX / AMETEK OIM Analysis Ver. 8.6), electron beam acceleration voltage 15kV, 10000μm ２ The above measurement area was analyzed, excluding measurement points with a CI value of 0.1 or less at a measurement interval of 0.1 μm, and the orientation density was determined. The crystal orientation distribution function obtained from the analysis was expressed in Euler angles. Then, the average orientation density was calculated for the ranges φ1: 30 to 45°, Φ: 40 to 50°, φ2: 0°, and φ1: 20 to 35°, Φ: 90°, φ2: 45°, based on the obtained orientation density. The evaluation results are shown in Table 3.

[0075] (Proportion of grain boundaries with orientation difference of 10° or less) As described above, the orientation difference of each grain was analyzed, excluding measurement points where the CI value analyzed by the data analysis software OIM was 0.1 or less. Grain boundaries were defined as measurement points where the orientation difference between adjacent measurement points was 5° or more. The proportion of grain boundaries with orientation differences of 5 to 10° was calculated from the distribution of the angle difference (Misorientation Angle) between adjacent crystals across the grain boundary. The evaluation results are shown in Table 3.

[0076] (KAM value) As described above, excluding measurement points where the CI value analyzed by the data analysis software OIM was 0.1 or less, the orientation difference of each crystal grain was analyzed using the data analysis software OIM. With the proximity order set to 1, the boundary between pixels where the orientation difference between adjacent pixels is 5° or more was considered a crystal grain boundary and analyzed to obtain the KAM value for all pixels. Then, the average value of the KAM value was calculated. The evaluation results are shown in Table 3.

[0077] (Tensile Strength) Test specimens No. 13B, as specified in JIS Z 2241, were taken from the strip material used for characteristic evaluation, and the tensile strength was measured using the offset method of JIS Z 2241. The test specimens were taken in a direction parallel to the rolling direction. The evaluation results are shown in Table 3.

[0078] (Conductivity) A test specimen measuring 10 mm in width and 150 mm in length was taken from the strip material used for characteristic evaluation, and its electrical resistance was determined using the four-terminal method. The dimensions of the test specimen were measured using a micrometer, and its volume was calculated. The conductivity was then calculated from the measured electrical resistance value and volume. The test specimen was taken so that its longitudinal direction was parallel to the rolling direction of the strip material used for characteristic evaluation. The evaluation results are shown in Table 3.

[0079] (Scratch and Deformation Resistance) To evaluate the scratch and deformation resistance of the copper material, the Vickers hardness of the outer surface was measured. The measurement was performed according to JIS Z 2241-1. A load of 10 g was used to measure the hardness of the outer surface. A value of 80 HV or higher was evaluated as "G", and a value of less than 80 HV was evaluated as "NG". The evaluation results are shown in Table 3.

[0080] (Dimension Accuracy) To evaluate the dimension accuracy of the copper material, the amount of sag when punching was evaluated. A large number of square holes (8 mm × 8 mm) were punched from the strip for characteristic evaluation using a mold, and the evaluation was performed by measuring the height of the sag portion. The clearance of the mold was set to 3 - 6% of the plate thickness ratio, and punching was performed at a punching speed of 50 spm (strokes per minute). The measurement of the sag height was carried out by observing the cut surface on the punching side, and the average of 10 points at each measurement location was evaluated. When the sag height was 10% or more of the plate thickness, it was evaluated as "C", when it was 6% or more and less than 10%, it was evaluated as "B", and when it was less than 6%, it was evaluated as "A". The evaluation results are shown in Table 3.

[0081] (Bonding Test) Samples of 40 mm × 40 mm were cut out from the above-mentioned strip for characteristic evaluation. A paste-like active silver brazing material (TB - 608T manufactured by Tokyo Blaze) was applied to both sides of a ceramic plate (material: Si ３ N ４ , 50 mm × 50 mm × thickness 0.32 mm). A ceramic plate was sandwiched between two of the above-mentioned samples (pure copper plates), and heat treatment was carried out under a load with a pressing pressure of 0.59 MPa. The heat treatment was performed under the following conditions. The laminated pure copper plates and the ceramic plate were put into a furnace at 850 °C, and after confirming with a thermocouple that the material temperature had reached 850 °C, it was held for 60 minutes. After the heating was completed, furnace cooling (cooling in the furnace) was carried out until it reached room temperature. After the temperature had dropped to room temperature, the crystal structure was observed for a cross-section (rolling surface) orthogonal to the plate thickness direction of the copper plate.

[0082] (Uniformity) Using EBSD, the average crystal grain size (Area Fraction) was randomly measured at 5 locations on the copper plate joined to the ceramic substrate in the above-mentioned bonding test. When all 5 numerical values were within the range from 0.9 times to 1.1 times the median of the 5 measurement values, it was evaluated as "A", when all 5 numerical values were within the range from 0.8 times to 1.2 times the median of the 5 measurement values, it was evaluated as "B", and those that did not meet these were evaluated as "C". The evaluation results are shown in Table 3.

[0083] (Grain Growth Inhibition Evaluation) The average grain size (Area Fraction) was measured at five random locations using EBSD. Of the five measured values, if the maximum average grain size was 500 μm or less, it was evaluated as "A"; if it was between 500 μm and 1000 μm, it was evaluated as "B"; and if it was greater than 1000 μm, it was evaluated as "C". The evaluation results are shown in Table 3.

[0084]

[0085]

[0086]

[0087] In Comparative Example 1, the average orientation density was low at φ1: 30-45°, Φ: 40-50°, and φ2: 0° (1.2), while the average orientation density was high at φ1: 20-35°, Φ: 90°, and φ2: 45° (1.5), indicating insufficient scratch resistance, deformation resistance, and dimensional accuracy. In Comparative Example 2, the average orientation density was high at φ1: 20-35°, Φ: 90°, and φ2: 45° (1.6), indicating insufficient dimensional accuracy. Furthermore, the crystalline structure of the copper material in the bonded material was non-uniform.

[0088] In Comparative Example 3, the average orientation density at φ1: 30-45°, Φ: 40-50°, and φ2: 0° was low at 2.1, resulting in a non-uniform crystal structure of the copper material in the bonded material, and thus insufficient suppression of grain growth. In Comparative Example 4, the average orientation density at φ1: 20-35°, Φ: 90°, and φ2: 45° was high at 1.8, resulting in a non-uniform crystal structure of the copper material in the bonded material, and thus insufficient suppression of grain growth.

[0089] In contrast, in Examples 1 to 13 of the present invention, the average orientation density at φ1: 30 to 45°, Φ: 40 to 50°, and φ2: 0° was 3.0 or higher, and the average orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45° was 1.4 or lower, resulting in excellent scratch resistance, deformation resistance, and dimensional accuracy. Furthermore, the crystal structure of the copper material in the bonding material became uniform, and grain growth was sufficiently suppressed.

[0090] From the above, it has been confirmed that, according to the present invention, it is possible to suppress grain coarsening and non-uniformity even when held at high temperatures, and to provide a copper material with excellent scratch resistance, deformation resistance and high dimensional accuracy, as well as an insulating substrate using this copper material.

Claims

1. A copper material characterized by having a Cu content of 99.9 mass% or more, an electrical conductivity of 95% IACS or more, and, when the crystal orientation distribution function obtained from texture analysis by EBSD in a cross section perpendicular to the thickness direction is expressed in terms of Euler angles (φ1, Φ, φ2), the average value of the orientation density at φ1: 30 to 45°, Φ: 40 to 50°, and φ2: 0° is 3.0 or more, and the average value of the orientation density at φ1: 20 to 35°, Φ: 90°, and φ2: 45° is 1.4 or less.

2. The copper material according to claim 1, characterized in that, in a cross section perpendicular to the thickness direction, when boundaries with an orientation difference of 5° or more are defined as grain boundaries, the proportion of grain boundaries with an orientation difference of 10° or less is 4% or more.

3. The copper material according to claim 1, characterized in that the average value of the KAM (Kernel Average Misorientation) value in a cross section perpendicular to the plate thickness direction is 0.6 or higher.

4. The copper material according to claim 1, characterized in that it contains one or more additive elements selected from Be, Mg, Ca, Sr, Ba, rare earth elements, S, Se, Te, P, Sn, Ni, Zr, and Ag in a total amount of 10 mass ppm or more and 200 mass ppm or less.

5. The copper material according to claim 1, characterized in that its tensile strength is 300 MPa or more.

6. An insulating substrate comprising a ceramic substrate and a copper plate bonded to at least one surface of the ceramic substrate, wherein the copper plate is made of the copper material described in any one of claims 1 to 5.

7. The insulating substrate according to claim 6, characterized in that the ceramic substrate is silicon nitride, alumina, or aluminum nitride.

8. The insulating substrate according to claim 6, characterized in that a plating layer is formed on the side of the copper plate opposite to the ceramic substrate.

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