Pure copper material, insulating substrate and electronic device

Abstract

In this pure copper material, the content of Cu is 99.96 mass% or more, and it contains either or both of a group A element selected from one or more of Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and a group B element selected from one or more of O, S, Se, and Te in a range of 10 mass ppm or more and 300 mass ppm or less based on the total amount. The average crystal grain size in the rolling surface is 15 μm or more, and the high-temperature Vickers hardness at 850 °C is 4.0 HV or more and 10.0 HV or less.

Description

Technical Field

[0001] The present invention relates to a pure copper material suitable for electrical / electronic components such as heat sinks or thick copper circuits, and particularly to a pure copper material used in an insulating substrate on which a power semiconductor or the like is mounted, an insulating substrate using the pure copper material, and an electronic device.

[0002] This application claims priority based on Japanese Patent Application No. 2022-121434 filed on July 29, 2022, and Japanese Patent Application No. 2023-120992 filed on July 25, 2023, and incorporates their contents herein. Background Art

[0003] Conventionally, pure copper materials with high conductivity have been used in electrical / electronic components such as heat sinks or thick copper circuits.

[0004] In recent years, as the amount of current flowing through components for electrical / electronic devices has increased, resistive heating has become a problem.

[0005] In electronic devices such as semiconductor devices, for example, an insulating substrate is used that is formed by bonding a pure copper material to a ceramic substrate to form the above-mentioned heat sink or thick copper circuit.

[0006] When bonding a ceramic substrate and a pure copper material, since the pressure treatment is performed in a high-temperature atmosphere, bonding defects, appearance defects, and defects in the inspection process may sometimes occur due to coarsening or uneven growth of the crystal grain size of the pure copper material.

[0007] To solve this problem, it is required that the pure copper material has a small change in crystal grain size and a uniform size even after heat treatment.

[0008] Therefore, for example, in Patent Documents 1 and 2, a technique for suppressing the growth of crystal grains in a pure copper material has been proposed.

[0009] It is described in Patent Document 1 that by containing 0.0006 to 0.0015 wt% of S, even when heat treatment is performed above the recrystallization temperature, crystal grains of a certain size can be adjusted.

[0010] In addition, in Patent Document 2, by containing Ca and specifying the ratio of the content of Ca to the total content of O, S, Se, and Te, coarsening of crystal grains can be suppressed even when heat treatment is performed at 800°C.

[0011] Patent Document 1: Japanese Patent Laid-Open No. 06-002058

[0012] Patent Document 2: International Publication No. 2020 / 203071

[0013] However, in Patent Documents 1 and 2, a configuration is adopted to suppress the coarsening of crystal grains by specifying the composition. However, depending on the heat treatment conditions and the like, it may not be possible to sufficiently suppress the coarsening of crystal grains or the deviation of crystal grain diameters.

[0014] In particular, when firmly bonding a ceramic substrate and a copper plate, high-temperature heat treatment is performed in a state where the ceramic substrate and the copper plate are pressed with a constant pressure in the stacking direction. At this time, in the copper plate, crystal grains tend to grow unevenly, and due to the coarsening or uneven growth of crystal grains, bonding defects, appearance defects, and defects in the inspection process may sometimes occur. Summary of the Invention

[0015] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a pure copper material in which the change in crystal structure is small even after heat treatment, the deviation of crystal grain diameters is suppressed, and a uniform crystal structure can be obtained, an insulating substrate using the pure copper material, and an electronic device.

[0016] As a result of intensive studies by the present inventors to solve this problem, it has been found that in order to suppress the coarsening of crystal grains during heat treatment in bonding, it is important to control the high-temperature hardness of the material within a certain range.

[0017] Generally, the material strength of copper materials at high temperatures becomes significantly lower than that at normal temperatures. If the material strength at high temperatures is too low, the introduction of strain due to the difference in linear expansion coefficients between ceramics and copper materials will be promoted, and more strain that becomes the driving force for crystal grain growth may be introduced. And if the strength at high temperatures is too high, stress will be applied to the ceramics, resulting in a decrease in the thermal reliability of the insulating substrate. Therefore, it has been clarified that controlling the strength (hardness) at high temperatures is important.

[0018] The pure copper material of Scheme 1 of the present invention is characterized in that the content of Cu is 99.96% by mass or more, and contains any one or both of Group A elements selected from Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu in a range of 10 mass ppm or more and 300 mass ppm or less in total and Group B elements selected from O, S, Se, and Te, the average crystal grain diameter in the rolling plane is 15 μm or more, and the high-temperature Vickers hardness at 850 °C is 4.0 HV or more and 10.0 HV or less.

[0019] The pure copper material according to Scheme 1 of the present invention has a Cu content of 99.96 mass% or more, and contains one or more elements of Group A selected from Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and one or more elements of Group B selected from O, S, Se, and Te in the range of 10 mass ppm or more and 300 mass ppm or less based on the total amount. Therefore, the electrical conductivity and heat dissipation are particularly excellent, and the growth of grains at high temperatures can be suppressed, making it particularly suitable as a raw material for components used in electrical / electronic devices for high-current applications.

[0020] Moreover, since the average crystal grain size in the rolling plane is 15 μm or more, the progress of recrystallization during heat treatment can be suppressed, and the coarsening of grains and the non-uniformity of the structure can be suppressed.

[0021] Furthermore, since the high-temperature Vickers hardness at 850 °C is in the range of 4.0 HV or more and 10.0 HV or less, the introduction of strain caused by the difference in the linear expansion coefficient between the ceramic and the copper material can be suppressed, and the introduction of strain that serves as a driving force for grain growth can be suppressed.

[0022] In Scheme 2 of the present invention, a compound composed of any one or both of the Group A elements and the Group B elements and Cu may be present in the pure copper material of Scheme 1.

[0023] In the pure copper material according to Scheme 2 of the present invention, since a compound composed of any one or both of the Group A elements and the Group B elements and Cu is present, the growth of grains at high temperatures can be suppressed. Even after heat treatment, the change in the crystal structure is further reduced, and a more uniform crystal structure can be obtained.

[0024] In Scheme 3 of the present invention, in the pure copper material of Scheme 2, the number density of the compound is 1.0×10 -4 pieces / μm 2 or more.

[0025] In the pure copper material according to Scheme 3 of the present invention, since the number density of the compound is 1.0×10 -4 pieces / μm 2 or more, the growth of grains during heat treatment can be further reliably suppressed by the pinning effect of the compound.

[0026] In Scheme 4 of the present invention, in the pure copper material of any one of Schemes 1 to 3, both the Group A elements and the Group B elements are contained, and the ratio A / B of the total content A mass ppm of the Group A elements to the total content B mass ppm of the Group B elements exceeds 1.0.

[0027] The pure copper material according to Embodiment 4 of the present invention, since the ratio A / B of the total content A in mass ppm of the elements in Group A to the total content B in mass ppm of the elements in Group B exceeds 1.0, can suppress the reaction between the elements in Group A and the elements in Group B, and can reliably form a compound composed of any one or both of the elements in Group A and Group B and Cu. Through the pinning effect of the compound, the growth of grains during heat treatment can be further reliably suppressed.

[0028] In Embodiment 5 of the present invention, in the pure copper material of any one of Embodiments 1 to 4, the standard deviation value of the high-temperature Vickers hardness is 1.0 HV or less.

[0029] The pure copper material according to Embodiment 5 of the present invention, since the standard deviation value of the high-temperature Vickers hardness is 1.0 HV or less, has a small deviation in high-temperature hardness and can suppress local deformation.

[0030] In Embodiment 6 of the present invention, in the pure copper material of any one of Embodiments 1 to 5, the content of P is 3.00 mass ppm or less.

[0031] The pure copper material according to Embodiment 6 of the present invention, when the content of P is 0.01 mass ppm or more and 3.00 mass ppm or less, can render oxygen contained as an impurity harmless and can fully exhibit the effect of suppressing the growth of grains of the elements in Group A and Group B (the effect of suppressing the growth of grains). When the content of P is 0 mass ppm or more and less than 0.01 mass ppm, the above-described effects are poor.

[0032] In Embodiment 7 of the present invention, in the pure copper material of any one of Embodiments 1 to 6, one or more selected from Ag, Fe, and Pb are included in a total amount of 50.0 mass ppm or less.

[0033] The pure copper material according to Embodiment 7 of the present invention, when one or more of Ag, Fe, and Pb are contained in a range of 5.0 mass ppm or more and 50.0 mass ppm or less in total amount, Ag, Fe, and Pb are dissolved in the copper matrix phase, whereby the growth of grains during heat treatment can be further suppressed. When the total amount of one or more selected from Ag, Fe, and Pb is 0 mass ppm or more and less than 5.0 mass ppm, the above-described effects are poor.

[0034] The insulating substrate according to Embodiment 8 of the present invention is characterized by including a ceramic substrate and a copper plate joined to one surface of the ceramic substrate, and the copper plate is composed of the pure copper material of any one of Embodiments 1 to 7.

[0035] The insulating substrate according to Embodiment 8 of the present invention, since the copper plate joined to the ceramic substrate is made of pure copper material of any one of Embodiments 1 to 7, can suppress the growth of crystal grains during joining, has a uniform crystal structure, and can be stably used.

[0036] The electronic device according to Embodiment 9 of the present invention is characterized by including the insulating substrate of Embodiment 8 and electronic components mounted on the insulating substrate.

[0037] The electronic device according to Embodiment 9 of the present invention, since it includes the insulating substrate of Embodiment 8, the copper plate has a uniform crystal structure and can be stably used.

[0038] According to the embodiment of the present invention, it is possible to provide a pure copper material in which the change in crystal structure is small even after heat treatment, the deviation of crystal grain size is suppressed, and a uniform crystal structure can be obtained, an insulating substrate using the pure copper material, and an electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic explanatory view of the insulating substrate and the electronic device of the present embodiment.

[0040] Figure 2 is a flowchart of the manufacturing method of the pure copper material of the present embodiment.

[0041] Figure 3A is the observation result of the compound in Example 2 of the present invention and is a TEM image (transmission electron image).

[0042] Figure 3B is the observation result of the compound in Example 2 of the present invention and is an electron diffraction image. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] Hereinafter, a pure copper material, an insulating substrate, and an electronic device according to an embodiment of the present invention will be described.

[0044] The pure copper material of the present embodiment is used as a raw material for electrical / electronic components such as heat sinks or thick copper circuits. When forming the above electrical / electronic components, the pure copper material is joined to a ceramic substrate, for example, to form an insulating substrate.

[0045] Figure 1 shows an insulating substrate 10 of an embodiment of the present invention and an electronic device 1 using the insulating substrate 10.

[0046] The electronic device 1 of the present embodiment includes: the insulating substrate 10 of the present embodiment; electronic components 3 joined to one side (the upper side in Figure 1 this figure) of the insulating substrate 10 through a first solder layer 2; and a heat sink 51 joined to the other side (the lower side in Figure 1 this figure) of the insulating substrate 10 through a second solder layer 8.

[0047] In addition, in the present embodiment, the electronic component 3 is a power semiconductor element, and the electronic device 1 is a power module.

[0048] The insulating substrate 10 includes a ceramic substrate 11, a circuit layer 12 disposed on one surface of the ceramic substrate 11 (the upper surface in Figure 1 this case), and a metal layer 13 disposed on the other surface of the ceramic substrate 11 (the lower surface in Figure 1 this case).

[0049] The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13.

[0050] The circuit layer 12 is formed by bonding a copper plate to one surface of the ceramic substrate 11. A circuit pattern is formed on the circuit layer 12, and one surface (the upper surface in Figure 1 this case) is set as the mounting surface for mounting the electronic component 3.

[0051] The metal layer 13 is formed by bonding a copper plate to the other surface of the ceramic substrate 11. The metal layer 13 has the effect of efficiently transferring heat from the electronic component 3 to the heat sink 51.

[0052] In addition, the copper plate forming the circuit layer 12 and the copper plate forming the metal layer 13 are bonded to the ceramic substrate 11 by existing bonding methods such as the DBC method and the AMB method.

[0053] Here, the temperature during bonding is, for example, a high temperature condition of 750 °C or higher, and coarsening of grains may occur in the circuit layer 12 and the metal layer 13.

[0054] Therefore, in the present embodiment, the copper plate forming the circuit layer 12 and the copper plate forming the metal layer 13 are made of the pure copper material of the present embodiment.

[0055] In the pure copper material of the present embodiment, the content of Cu is 99.96 mass% or more, and contains one or more elements of Group A selected from Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and one or more elements of Group B selected from O, S, Se, and Te in a range of 10 mass ppm or more and 300 mass ppm or less in total amount.

[0056] In addition, in the pure copper material of the present embodiment, it is preferable to contain both Group A elements and Group B elements, and the ratio A / B of the total content A mass ppm of Group A elements to the total content B mass ppm of Group B elements exceeds 1.0.

[0057] Moreover, in the pure copper material of the present embodiment, the content of P can be in the range of 0.01 mass ppm or more and 3.00 mass ppm or less.

[0058] Furthermore, in the pure copper material of the present embodiment, one or more selected from Ag, Fe, and Pb can be included in the range of 5.0 mass ppm or more and 50.0 mass ppm or less in total.

[0059] Moreover, in the pure copper material of the present embodiment, the average crystal grain size in the rolling plane is 15 μm or more, and the high-temperature Vickers hardness at 850 °C is in the range of 4.0 HV or more and 10.0 HV or less.

[0060] In addition, in the pure copper material of the present embodiment, the standard deviation value of the above high-temperature Vickers hardness is preferably 1.0 HV or less.

[0061] Moreover, in the pure copper material of the present embodiment, a compound composed of any one or both of the group A elements and the group B elements and Cu preferably exists. And the number density of this compound is preferably 1×10 -4 pieces / μm 2 or more.

[0062] Here, in the pure copper material of the present embodiment, the reasons for stipulating the content of Cu, the average crystal grain size, the high-temperature Vickers hardness, the content of various elements, and the compound as described above will be described below.

[0063] (Content of Cu: 99.96 mass% or more)

[0064] In electrical / electronic components for high-current applications, in order to suppress heat generation during energization, excellent electrical conductivity and heat dissipation are required, and pure copper with particularly excellent electrical conductivity and heat dissipation is preferably used.

[0065] Therefore, in the pure copper material of the present embodiment, the purity of Cu is stipulated to be 99.96 mass% or more. In addition, the purity of Cu is preferably 99.965 mass% or more, and more preferably 99.97 mass% or more. And there is no particular limitation on the upper limit of the purity of Cu, but when it exceeds 99.999 mass%, a special refining process is required and the manufacturing cost will increase significantly, so it is preferably 99.999 mass% or less.

[0066] (Average crystal grain size in the rolling plane: 15 μm or more)

[0067] In the pure copper material of the present embodiment, if the grain size of the grains in the rolling plane is fine, for example, when this pure copper material is heated to 800 °C or more, recrystallization is likely to occur, and it may promote grain growth and inhomogenization of the structure.

[0068] Therefore, in the pure copper material of the present embodiment, in order to suppress the coarsening of crystal grains and the non-uniformity of the structure during heat treatment, the average crystal grain diameter in the rolling plane is set to 15 μm or more.

[0069] In addition, in order to further suppress the coarsening of crystal grains during heat treatment, the average crystal grain diameter in the rolling plane is more preferably 30 μm or more, still more preferably 35 μm or more, and even more preferably 40 μm or more. Moreover, the average crystal grain diameter in the rolling plane is preferably 300 μm or less, more preferably 275 μm or less, and still more preferably 250 μm or less.

[0070] (High-temperature Vickers hardness at 850 °C: 4.0 HV or more and 10.0 HV or less)

[0071] In the pure copper material of the present embodiment, as the temperature rises, the mechanical properties decrease significantly. In the high-temperature state, deformation is likely to be locally concentrated due to external forces. Therefore, by increasing the hardness at high temperatures, deformation can be dispersed. On the other hand, if the hardness at high temperatures is too high, it may impose a large stress on the bonded ceramic substrate 11, which may lead to a decrease in the reliability of the insulating substrate 10.

[0072] Therefore, in the present embodiment, the high-temperature Vickers hardness at 850 °C is set within the range of 4.0 HV or more and 10.0 HV or less.

[0073] In addition, the high-temperature Vickers hardness at 850 °C is preferably 4.25 HV or more, and more preferably 4.5 HV or more. Moreover, the high-temperature Vickers hardness at 850 °C is preferably 9.9 HV or less, and more preferably 9.8 HV or less.

[0074] (Standard deviation value of high-temperature Vickers hardness at 850 °C: 1.0 HV or less)

[0075] In the pure copper material of the present embodiment, if the deviation of the high-temperature Vickers hardness is large, local deformation is likely to occur.

[0076] Therefore, in the present embodiment, it is preferable to set the standard deviation value of the high-temperature Vickers hardness at 850 °C to 1.0 HV or less.

[0077] In addition, the standard deviation value of the high-temperature Vickers hardness at 850 °C is more preferably 0.90 HV or less, further preferably 0.80 HV or less, and even more preferably 0.70 HV. Moreover, the standard deviation value of the high-temperature Vickers hardness at 850 °C is preferably 0.05 HV or more, further preferably 0.075 HV or more, and more preferably 0.10 HV or more.

[0078] (Total content of any one or both of the Group A elements and the Group B elements: 10 mass ppm or more and 300 mass ppm or less)

[0079] The solid solubility limits of Group A elements (Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and Group B elements (O, S, Se, Te) in Cu are very small, and they form compounds with Cu. Therefore, by adding either or both of Group A elements and Group B elements, stable compounds are formed even at high temperatures. And since these compounds contain Cu, the thermal conductivity is not significantly reduced. Thus, by adding either or both of Group A elements and Group B elements, stable compounds can be formed at high temperatures, the movement of grain boundaries at high temperatures can be inhibited, and the growth of grains can be inhibited. Also, due to the presence of the compounds, even after heat treatment, the change in the crystal structure is further reduced, and a more uniform crystal structure can be obtained. On the other hand, if a large amount of either or both of Group A elements and Group B elements is contained, it may have an adverse effect on manufacturability.

[0080] Therefore, in the present embodiment, the total content of either or both of Group A elements and Group B elements is set within the range of 10 mass ppm or more and 300 mass ppm or less.

[0081] In addition, the total content of either or both of Group A elements and Group B elements is preferably 15 mass ppm or more, more preferably 20 mass ppm or more. And the total content of either or both of Group A elements and Group B elements is preferably 290 mass ppm or less, more preferably 280 mass ppm or less.

[0082] (The ratio A / B of the total content A mass ppm of Group A elements to the total content B mass ppm of Group B elements: exceeding 1.0)

[0083] The reactivity between Group A elements (Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and Group B elements (O, S, Se, Te) is high, so Group A elements and Group B elements are consumed by reacting with each other.

[0084] Therefore, in order to sufficiently form the compounds composed of either or both of the Group A elements and the Group B elements and Cu, it is preferable to set the ratio A / B of the total content A mass ppm of Group A elements to the total content B mass ppm of Group B elements to exceed 1.0.

[0085] In addition, the ratio A / B of the total content A in mass ppm of the group A elements to the total content B in mass ppm of the group B elements is more preferably more than 1.5, and further preferably more than 2.0. Moreover, the ratio A / B is preferably 100 or less, further preferably 75 or less, and more preferably 50 or less.

[0086] (Number density of the compound composed of any one or both of the group A elements and the group B elements and Cu: 1.0×10 -4 pieces / μm 2 or more)

[0087] As described above, the compound composed of any one or both of the group A elements and the group B elements and Cu has high stability at high temperatures. Therefore, during heat treatment, the pinning effect of this compound can sufficiently suppress the growth of grains.

[0088] Therefore, in the present embodiment, it is preferable to set the number density of the compound composed of any one or both of the group A elements and the group B elements and Cu to 1.0×10 -4 pieces / μm 2 or more. In addition, the number density of the compound composed of any one or both of the group A elements and the group B elements and Cu is more preferably 2.5×10 -4 pieces / μm 2 or more, and further preferably 5.0×10 -4 pieces / μm 2 or more. Moreover, the number density of the compound composed of any one or both of the group A elements and the group B elements and Cu is preferably 1000×10 -4 pieces / μm 2 or less, further preferably 900×10 -4 pieces / μm 2 or less, and more preferably 800×10 -4 pieces / μm 2 or less.

[0089] (P: 0.01 mass ppm or more and 3.00 mass ppm or less)

[0090] P is widely used as an element that deactivates oxygen in copper. However, when the amount of P is above a certain level, it not only hinders the action of oxygen but also hinders the action of the grain growth inhibitory element (element that inhibits the growth of grains) present at the grain boundaries. Therefore, when heated to a high temperature, the element that inhibits the growth of grains cannot fully function, and thus coarsening and non-uniformity of grains may occur.

[0091] Therefore, in the present embodiment, it is preferable to set the content of P to 0.01 mass ppm or more and 3.00 mass ppm or less.

[0092] In addition, the content of P is preferably 2.50 mass ppm or less, more preferably 2.00 mass ppm or less.

[0093] (Total content of one or more selected from Ag, Fe, and Pb: 5.0 mass ppm or more and 50.0 mass ppm or less)

[0094] Ag, Fe, and Pb are elements that have the effect of suppressing the coarsening of crystal grains by dissolving in the copper matrix phase. On the other hand, when a large amount of Ag, Fe, and Pb is contained, it may lead to an increase in manufacturing cost and a decrease in conductivity.

[0095] Therefore, in the present embodiment, it is preferable to set the total content of one or more selected from Ag, Fe, and Pb within the range of 5.0 mass ppm or more and 50.0 mass ppm or less.

[0096] In addition, the total content of one or more selected from Ag, Fe, and Pb is more preferably 6.0 mass ppm or more, and even more preferably 7.0 mass ppm or more. On the other hand, the total content of one or more selected from Ag, Fe, and Pb is more preferably 40.0 mass ppm or less, and even more preferably 30.0 mass ppm or less.

[0097] (Other inevitable impurities)

[0098] Examples of inevitable impurities contained in the remaining portion other than the above-mentioned elements with determined contents include Al, As, B, Be, Bi, Cd, Cr, Sc, V, Nb, Ta, Mo, Mg, Ni, W, Mn, Re, Ru, Ti, Os, Co, Rh, Ir, Pd, Pt, Au, Zn, Hg, Ga, In, Ge, Tl, N, Sb, Si, Sn, Li, etc. These inevitable impurities can be contained within a range that does not affect the properties.

[0099] Here, these inevitable impurities may reduce the conductivity, so the total amount is preferably 0.04 mass% or less, more preferably 0.03 mass% or less, even more preferably 0.02 mass% or less, and still more preferably set to 0.01 mass% or less.

[0100] Moreover, the content of each of these inevitable impurities is preferably 30 mass ppm or less, more preferably 20 mass ppm or less, and even more preferably 15 mass ppm or less.

[0101] Next, with reference to Figure 2 the flowchart shown, the manufacturing method of the pure copper material of the present embodiment having such a configuration will be described.

[0102] (Melting / Casting Process S01)

[0103] First, either or both of the above Group A elements and Group B elements, and other additive elements are added to the copper melt obtained by melting the oxygen-free copper raw material to adjust the composition, thereby producing a copper alloy melt. Additionally, for the addition of various elements, elemental monomers or master alloys can be used. Moreover, the raw materials containing the above elements can be melted together with the copper raw material. Here, the copper melt is preferably so-called 4N Cu with a purity of 99.99 mass% or more, or so-called 5N Cu with a purity of 99.999 mass% or more.

[0104] In the melting process, in order to reduce the hydrogen concentration, it is preferably melted in an inert gas atmosphere (such as Ar gas) with a low vapor pressure of H2O, and the holding time during melting is limited to the minimum. Then, the copper alloy melt with adjusted composition is poured into a mold to produce an ingot. Additionally, when considering mass production, a continuous casting method or a semi-continuous casting method is preferably used.

[0105] Here, by setting the cooling rate during casting to 0.1 °C / sec or more, trace impurities and additive elements present in copper during solidification can be uniformly dispersed.

[0106] (First Cold Working Process S02)

[0107] For the obtained ingot, cold working is performed to deform the shape into a specified size. The working rate here is not particularly specified, but it is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more.

[0108] The working method is not particularly limited, but in the case where the final shape is a plate or strip, rolling is preferably used. In the case where the final shape is a wire or rod, extrusion or groove rolling is preferably used. In the case where the final shape is a block, forging or stamping is preferably used.

[0109] (First Heat Treatment Process S03)

[0110] Next, for the purpose of homogenizing the structure through recrystallization, heat treatment is performed on the copper raw material after the first cold working process S02.

[0111] Here, the heat treatment method is not particularly limited, but it is preferably performed in a non-oxidizing or reducing atmosphere. By performing heat treatment at a high temperature of 500 °C or more, such as 800 °C × 1 minute, for a short time, the homogenization of the structure can be promoted.

[0112] The cooling method is not particularly limited, but a method with a cooling rate of 200 °C / min or more, such as water quenching, is preferably used.

[0113] (Second cold working process S04)

[0114] Next, for the copper raw material after the first heat treatment process S03, cold working is performed while maintaining the material in a temperature region where the surface temperature of the material is 10°C or lower.

[0115] During cold working, the temperature of the material rises during processing due to processing heat. Here, if recrystallization occurs in a part of the material due to the temperature rise caused by processing heat, it will have an adverse effect on the microstructure control in subsequent multi-stage heat treatments, and it may not be possible to disperse elements uniformly. The processing rate here is not particularly specified, but it is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more.

[0116] The processing method is not particularly limited, but in the case where the final shape is a plate or strip, rolling is preferably used. In the case where the final shape is a wire or rod, extrusion or groove rolling is preferably used. In the case where the final shape is a block, forging or stamping is preferably used.

[0117] (Multi-stage heat treatment process S05)

[0118] Next, multi-stage heat treatment is performed on the copper raw material that has undergone the second cold working process S04 to intentionally segregate trace additive elements to the grain boundaries.

[0119] In the multi-stage heat treatment process S05, first, by maintaining the copper raw material at a high temperature of 750°C or higher, the crystal grain size is coarsened to a certain standard degree. And, instead of directly cooling to room temperature, the temperature of the copper raw material is changed to the medium temperature region of 400°C to 750°C within 60 seconds and maintained at this temperature for 1 minute or more, whereby it is possible to intentionally segregate trace additive elements to the grain boundaries without introducing lattice defects (atomic vacancies) generated by cooling. By segregating trace additive elements at the grain boundaries, the high-temperature Vickers hardness at 850°C can be controlled to 4.0 - 10.0 HV. When changing the heat treatment temperature, it can be achieved by moving the copper raw material in a furnace that maintains the corresponding temperature region without significantly reducing the temperature.

[0120] Here, the heat treatment method is not particularly limited, but it is preferably performed in a non-oxidizing or reducing atmosphere. And, during heat treatment, heat treatment can also be performed by moving the copper raw material between liquids maintained at a high temperature such as in a salt bath.

[0121] The cooling method after multi-stage heat treatment is not particularly limited, but a method with a cooling rate of 200°C / min or more such as water quenching is preferred.

[0122] (Conditioning rolling process S06)

[0123] In order to adjust the material strength, temper rolling can be performed on the copper raw material after the multi-stage heat treatment process S05. Additionally, in cases where low material strength is required, temper rolling can be omitted.

[0124] In this temper rolling process S06, if the strain energy becomes high, the structure at high temperatures becomes unstable. Therefore, the rolling ratio is preferably set to 30% or less, more preferably 25% or less, and even more preferably 20% or less.

[0125] Furthermore, the final thickness is not particularly limited. For example, a thickness in the range of 0.5 mm or more and 5 mm or less is preferred.

[0126] Through the above-mentioned respective processes, the pure copper material of the present embodiment can be produced.

[0127] According to the pure copper material of the present embodiment configured as above, the content of Cu is 99.96 mass% or more, and it contains, in a total amount, one or more elements of Group A selected from Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and one or more elements of Group B selected from O, S, Se, and Te, either one or both. Therefore, the electrical conductivity and heat dissipation are particularly excellent, and the growth of grains at high temperatures can be suppressed, making it particularly suitable as a raw material for components used in electrical / electronic devices for high-current applications.

[0128] Moreover, since the average crystal grain size in the rolling plane is 15 μm or more, the progress of recrystallization during heat treatment can be suppressed, and the coarsening of grains and the non-uniformity of the structure can be suppressed.

[0129] Furthermore, since the high-temperature Vickers hardness at 850 °C is in the range of 4.0 HV or more and 10.0 HV or less, the introduction of strain caused by the difference in the linear expansion coefficients between the ceramic and the copper material can be suppressed, and the introduction of strain that serves as a driving force for grain growth can be suppressed.

[0130] The method for obtaining the high-temperature Vickers hardness at 850 °C within the above range is not limited to a specific method. For example, it can be achieved by controlling the temperature of the first heat treatment process and the multi-stage heat treatment process, the surface temperature of the material in the second cold working process, and the rolling ratio in the temper rolling process as described above.

[0131] Here, in the pure copper material of the present embodiment, when there is a compound composed of any one or both of the group A elements and the group B elements and Cu, the pinning effect of the compound stable at high temperature can suppress the growth of grains at high temperature. Even after heat treatment, the change in the crystal structure is further reduced, so that a more uniform crystal structure can be obtained.

[0132] Moreover, in the pure copper material of the present embodiment, when the number density of the compound composed of any one or both of the group A elements and the group B elements and Cu is 1.0×10 -4 pieces / μm 2 or more, the pinning effect of the compound stable at high temperature can be fully exerted, and thus the growth of grains during heat treatment can be further reliably suppressed.

[0133] Furthermore, in the pure copper material of the present embodiment, when the ratio A / B of the total content A mass ppm of the group A elements to the total content B mass ppm of the group B elements exceeds 1.0, the reaction between the group A elements and the group B elements can be suppressed and consumed, so that a compound composed of any one or both of the group A elements and the group B elements and Cu can be reliably formed. Through the pinning effect of this compound, the growth of grains during heat treatment can be further reliably suppressed.

[0134] Moreover, in the pure copper material of the present embodiment, when the standard deviation value of the high-temperature Vickers hardness is 1.0 HV or less, the deviation of the high-temperature hardness is controlled to be small, so that local deformation can be suppressed.

[0135] Furthermore, in the pure copper material of the present embodiment, when the content of P is 0.01 mass ppm or more and 3.00 mass ppm or less, the oxygen contained as an impurity can be rendered harmless, and the grain growth inhibitory effects of the group A elements and the group B elements can be fully exerted.

[0136] Moreover, in the pure copper material of the present embodiment, when one or more selected from Ag, Fe, and Pb are included in a total amount in the range of 5.0 mass ppm or more and 50.0 mass ppm or less, Ag, Fe, and Pb are dissolved in the copper matrix phase, whereby the growth of grains during heat treatment can be further suppressed.

[0137] In the insulating substrate 10 of the present embodiment, there are a ceramic substrate 11, a circuit layer 12 joined to one surface of the ceramic substrate 11, and a metal layer 13 joined to the other surface of the ceramic substrate 11. The copper plates forming the circuit layer 12 and the metal layer 13 are made of the pure copper material of the present embodiment. Therefore, the growth of grains during bonding to the ceramic substrate 11 can be suppressed, and the deviation of the crystal grain size can be suppressed, so that it has a uniform crystal structure and can be stably used.

[0138] In the electronic device 1 of the present embodiment, since the insulating substrate 10 and the electronic components 3 mounted on the circuit layer 12 of the insulating substrate 10 are provided, the copper plates forming the circuit layer 12 and the metal layer 13 have a uniform crystal structure and can be stably used.

[0139] As described above, the pure copper material as the embodiment of the present invention has been described. However, the present invention is not limited thereto, and can be appropriately changed without departing from the technical gist of the invention.

[0140] For example, in the above embodiment, an example of the manufacturing method of the pure copper material has been described. However, the manufacturing method of the pure copper material is not limited to the method described in the embodiment, and an existing manufacturing method can also be appropriately selected for manufacturing.

[0141] Moreover, when the manufacturing method has a rolling process, the pure copper material of the present embodiment can also be referred to as a pure copper rolled material.

[0142] Examples

[0143] Hereinafter, the results of the confirmation experiment conducted to confirm the effects of the present invention will be described.

[0144] The P concentration was purified to 0.001 mass ppm or less by the zone melting purification method, thereby obtaining pure copper with a purity of 99.999 mass% or more. The raw material composed of this pure copper was put into a high-purity graphite crucible and melted by high-frequency induction heating in an atmosphere furnace set to an Ar gas atmosphere.

[0145] Using 6N (purity of 99.9999 mass% or more) high-purity copper and 2N (purity of 99 mass% or more) elements, a master alloy containing 1 mass% of various elements was produced. The master alloy was added to the obtained copper melt, and the composition shown in Tables 1 to 4 was prepared to obtain a copper alloy melt. The obtained copper alloy melt was poured into a graphite mold to produce an ingot.

[0146] In addition, the size of the ingot was set to a thickness of about 100 mm × a width of about 100 mm × a length of about 150 to 200 mm. The cooling rate here was 0.1 °C / sec or more in all samples.

[0147] As the first cold working, the obtained ingot was cold-rolled at the rolling ratios described in Tables 5 and 6.

[0148] Next, the copper raw material after the first cold working was subjected to the first heat treatment under the conditions described in Tables 5 and 6 in an Ar gas atmosphere. In addition, in order to remove the oxide film generated by the heat treatment, surface grinding was performed and cut into a specified size.

[0149] Next, for the copper raw material after the first heat treatment, as the second cold working, cold rolling was carried out at the rolling ratios described in Tables 5 and 6. Here, in the second cold working, before each pass of rolling, the copper raw material was held in a freezer at 0°C or lower, and immediately after taking out the copper raw material, rolling was carried out. While measuring the surface temperature of the copper raw material after rolling with a contact thermometer, it was confirmed whether the surface temperature was maintained below 10°C during rolling. In addition, in Comparative Example 5, the surface temperature of the copper raw material in the second cold working was 50°C.

[0150] Next, multi-stage heat treatment was performed on the copper raw material after the second cold working. In addition, the multi-stage heat treatment was carried out by moving the copper raw material between salt baths held at the temperatures described in Tables 5 and 6. In addition, in order to remove the oxide film generated by the heat treatment, surface grinding was carried out, and in order to adjust the final thickness, it was cut into a specified size.

[0151] Finally, temper rolling was carried out under the conditions described in Tables 5 and 6 to manufacture a strip (strip for property evaluation) with a thickness of 0.8 mm and a width of 60 mm.

[0152] Moreover, the following items were evaluated.

[0153] (Composition analysis)

[0154] Measurement specimens were collected from the obtained ingot. The contents of S and O were measured by the infrared absorption method, and the contents of other elements were measured by using a glow discharge mass spectrometer (GD-MS). In addition, the measurement was carried out at two places, the central part of the specimen and the end part in the width direction, and the one with the higher content was taken as the content of the sample.

[0155] (Average crystal grain size)

[0156] A 20 mm × 20 mm sample was cut out from the obtained strip for property evaluation, and the average crystal grain size was determined by a SEM-EBSD (Electron Backscatter Diffraction Patterns) measuring device. The conditions of the electron microscope and the conditions of the EBSD detector are shown below.

[0157] (Conditions of the electron microscope)

[0158] Magnification of observation or area of measurement field: 400 μm × 800 μm

[0159] Accelerating voltage: 20 kV

[0160] Working distance: 20 mm

[0161] Specimen tilt angle: 70°

[0162] (Conditions of EBSD detector)

[0163] Name of analysis software: OIM DataAnalysis ver.8.6 manufactured by EDAX / TSL Corporation (now AMETEK Corporation) CI value (reliability index): Measurement points with a value greater than 0.1 were used for analysis.

[0164] Grain boundary angular difference: A difference of 5° or more was regarded as a grain boundary.

[0165] Minimum grain size: Two or more step sizes were regarded as a grain.

[0166] Step size: 1 μm

[0167] Treatment of twins: Twins were regarded as grain boundaries.

[0168] The rolling surface was mechanically polished using water-resistant abrasive paper and diamond abrasive grains. Then, fine polishing was performed using a colloidal silica solution. Subsequently, an electron beam was irradiated onto each measurement point (pixel) within the measurement range on the sample surface using a scanning electron microscope, and through orientation analysis based on the electron backscatter diffraction method, the boundary between measurement points with an orientation difference of 5° or more between adjacent measurement points was set as a grain boundary. The boundary between measurement points with an orientation difference of more than 5° and less than 15° between adjacent measurement points was set as a small-angle grain boundary. The boundary between measurement points with an orientation difference of 15° or more between adjacent measurement points was set as a large-angle grain boundary. At this time, twin boundaries were also set as large-angle grain boundaries. Also, the measurement range was adjusted so that each sample contained 100 or more grains. Based on the obtained orientation analysis results, a grain boundary map was made using large-angle grain boundaries. According to the cutting method of JIS H 0501, for the grain boundary map, five line segments of a specified length were drawn at specified intervals in both the vertical and horizontal directions. The number of grains that were completely cut was counted, and the average value of their cutting lengths was calculated as the crystal grain size.

[0169] (High-temperature Vickers hardness)

[0170] A 10 mm × 10 mm sample was cut from the obtained property evaluation strip, and the rolling surface was mechanically polished using water-resistant abrasive paper and diamond abrasive grains. The high-temperature Vickers hardness was measured using a high-temperature Vickers hardness tester (HTM-1200-III) manufactured by INTESCO Corporation.

[0171] The pressure was reduced to 1×10 -3 Pa, then heated to 850°C at a heating rate of 20°C / min and held at 850°C for 5 minutes. Subsequently, using a diamond indenter and a test force of 0.98 N, the indenter was struck in, and the size of the indentation of the indenter shape was measured, thereby measuring the Vickers hardness.

[0172] For a sample, the Vickers hardness was measured at 10 points, and the average value was calculated using the measured values at the 10 points. The average value was taken as the high-temperature Vickers hardness of the sample. Also, the standard deviation value of the high-temperature Vickers hardness was obtained using the measured values at the 10 points.

[0173] (Number density of compounds)

[0174] Measurement specimens were collected from the strip for property evaluation, and the rolling surface was subjected to CP polishing. Using FE-SEM (field emission scanning electron microscope), observations were made in 50 regions at a magnification of 2000 times (approx. 2500 μm 2 / field of view). The number density of compounds (compounds composed of any one or both of the group A elements and the group B elements and Cu) was calculated based on the observation results in the 50 regions.

[0175] (Identification of compounds)

[0176] Using the FIB (Focused Ion Beam) method, a sample for observing compounds was prepared from the strip for property evaluation. For this sample, particle observation was performed using a transmission electron microscope (TEM: manufactured by JEOL Ltd., JEM-2010F), and EDX analysis (energy dispersive X-ray spectroscopy) was carried out to confirm whether the compound was a particle composed of any one or both of the group A elements and the group B elements and Cu.

[0177] Here, in Figure 3A 、 Figure 3B the observation results of the compounds in Example 2 of the present invention are shown. It was confirmed that the observed compounds contained Cu5Ca.

[0178] (Average crystal grain size d after pressure heat treatment ave )

[0179] A sample of 40 mm × 40 mm was cut out from the above-mentioned strip for property evaluation. A paste-like active silver solder (TB-608T manufactured by TOKYO BLAZE CO., LTD.) was coated on both sides of a ceramic plate (material: Si3N4, 50 mm × 50 mm × thickness 0.32 mm). The ceramic plate was sandwiched between two of the above samples (pure copper plates), and heat treatment was carried out under a load with a pressure of 0.59 MPa applied. Heat treatment was carried out under the following conditions. The stacked pure copper plates and the ceramic plate were placed in a furnace at 850 °C. After confirming that the material temperature reached 850 °C with a thermocouple, it was held for 60 minutes. After the heating was completed, furnace cooling (cooling was carried out in the furnace) was performed until the temperature reached room temperature. After the temperature dropped to room temperature, the average crystal grain size d was measured on the rolling surface of the pure copper plate by the following method ave .

[0180] First, the rolling surface (the surface not in contact with the ceramic plate) was mechanically polished using water-resistant abrasive paper and diamond abrasive grains. Subsequently, colloidal silica solution was used for fine polishing. Then, etching was carried out, and the rolling surface (the observation surface) was observed with an optical microscope. In accordance with the cutting method of JIS H 0501, five line segments of a specified length were each drawn at specified intervals in the longitudinal and transverse directions. The number of grains that were completely cut was counted, and the average value of their cutting lengths was taken as the average crystal grain size. When the average crystal grain size was 200 μm or less, it was designated as "A" (excellent). When the average crystal grain size exceeded 200 μm and was 300 μm or less, it was designated as "B" (good). When the average crystal grain size exceeded 300 μm and was 500 μm or less, it was designated as "C" (fair). When the average crystal grain size exceeded 500 μm, it was designated as "D" (poor).

[0181] (Particle size deviation after pressure heat treatment)

[0182] As described above, within the range of 40 mm × 40 mm of the test piece on which pressure heat treatment was performed, the average value of the major axis and minor axis of the coarsest grain excluding twins was taken as the maximum crystal grain size d max . Here, the maximum value of the length of the line segment cut by the grain boundary among the line segments drawn on the coarsest grain was taken as the major axis. And the maximum value of the length of the line segment cut by the grain boundary among the line segments perpendicular to the major axis was taken as the minor axis. The ratio d max of this maximum crystal grain size d ave to the above-mentioned average crystal grain size d max / d ave being 15 or less was evaluated as "B" (good), and when d max / d ave exceeded 15 and was 20 or less, it was evaluated as "C" (fair), and when d max / d ave exceeded 20, it was evaluated as "D" (poor).

[0183]

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191] In Comparative Example 1, the total content of the Group A elements and the Group B elements was 5.3 mass ppm, the high-temperature Vickers hardness was as low as 4.6 HV, the grains coarsened after pressure heat treatment, and the particle size deviation also increased.

[0192] In Comparative Example 2, the total content of the Group A elements and the Group B elements was 537.1 mass ppm, the high-temperature Vickers hardness was as high as 11.6 HV, and the particle size deviation also increased.

[0193] In Comparative Example 3, the high-temperature Vickers hardness was as low as 3.9 HV, the grains coarsened after pressure heat treatment, and the particle size deviation also increased.

[0194] In Comparative Example 4, the average crystal grain size in the rolling plane was 14 μm, the grains coarsened after pressure heat treatment, and the particle size deviation also increased.

[0195] In Comparative Example 5, the high-temperature Vickers hardness was as low as 3.8 HV, the grains coarsened after pressure heat treatment, and the particle size deviation also increased.

[0196] In contrast, in Examples 1 to 26 of the present invention, the total content of the Group A elements and the Group B elements was in the range of 10 mass ppm or more and 300 mass ppm or less, the high-temperature Vickers hardness was in the range of 4.0 HV or more and 10.0 HV or less, the average crystal grain size was 15 μm or more, and the average crystal grain size after pressure heat treatment was small and the particle size deviation decreased.

[0197] From the above, it was confirmed that according to the examples of the present invention, it was possible to provide a pure copper material in which the change in crystal structure was small even after heat treatment, and the deviation of crystal grain size was suppressed to obtain a uniform crystal structure.

[0198] Industrial Applicability

[0199] The pure copper material of the present embodiment is preferably applicable to electrical / electronic components such as heat sinks or thick copper circuits.

[0200] Symbol Explanation

[0201] 1 Electronic device

[0202] 3 Electronic component

[0203] 10 Insulating substrate

[0204] 11 Ceramic substrate

[0205] 12 Circuit layer

[0206] 13 Metal layer

Claims

1. A pure copper material, characterized in that the content of Cu is 99.96 mass% or more, it contains both one or more Group A elements selected from Ca, Ba, Sr, Zr, Hf, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and one or more Group B elements selected from O, S, Se, and Te in the range of 10 mass ppm or more and 300 mass ppm or less in total amount, and the ratio A / B of the total content A mass ppm of the Group A elements to the total content B mass ppm of the Group B elements exceeds 1.0, the average crystal grain size in the rolling plane is 15 μm or more, the high-temperature Vickers hardness at 850 °C is 4.0 HV or more and 10.0 HV or less.

2. The pure copper material according to claim 1, characterized in that there is a compound composed of any one or both of the Group A elements and the Group B elements and Cu.

3. The pure copper material according to claim 2, characterized in that The number density of the said compound is 1.0×10 -4 pieces / μm 2 or more.

4. The pure copper material according to claim 1, characterized in that the standard deviation value of the high-temperature Vickers hardness is 1.0 HV or less.

5. The pure copper material according to claim 1, characterized in that the content of P is 3.00 mass ppm or less.

6. The pure copper material according to claim 1, characterized in that it contains one or more selected from Ag, Fe, and Pb in a total amount of 50.0 mass ppm or less.

7. An insulating substrate, characterized in that it includes a ceramic substrate and a copper plate joined to one side of the ceramic substrate, and the copper plate is composed of the pure copper material according to any one of claims 1 to 6.

8. An electronic device, characterized in that it has the insulating substrate according to claim 7 and electronic components mounted on the insulating substrate.

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