Pure copper plate, copper / ceramic bonded body, and insulated circuit board

Abstract

The Cu content is 99.96% or more, and the combined content of Ag, Sn, and Fe is 9.0 massppm or more but less than 100.0 massppm. The residue contains unavoidable impurities. The average crystal grain size of the rolled surface is 10μm or more. The crystal planes parallel to the rolled surface have {022}, {002}, {113}, {111}, and {133} crystals. The diffraction peak intensity of each of the aforementioned crystal planes obtained by X-ray diffraction measurement using the 2θ / θ method on the aforementioned rolled surface satisfies I{022} / (I{022}+I{002}+I{113}+I{111}+I{133})≦0.15. I{002} / I{111}≧10.0, I{002} / I{113}≧15.0. This pure copper plate has a composition which has a Cu content of 99.96 mass% or more and a total content of Ag, Sn and Fe of not less than 9.0 mass ppm but less than 100.0 mass ppm, with the balance being made up of unavoidable impurities, while having an average crystal grain size of the crystal grains in a rolled surface of 10 [mu]m or more. This pure copper plate has crystals that have the (022) plane, the (002) plane, the (113) plane, the (111) plane or the (133) plane as a crystal plane that is parallel to the rolled surface; and the diffraction peak intensities of these crystal planes as determined by X-ray diffractometry by means of a 2[Theta] / [Theta] method with respect to the rolled surface satisfy I(022) / (I(022) + I(002) + I(113) + I(111) + I(133)) ≤ 0.15, I(002) / I(111) ≥ 10.0 and I(002) / I(113) ≥ 15.0.

Description

[Technical Field]

[0001] This invention relates to a pure copper plate suitable for electrical and electronic components such as heat sinks or thick copper circuits, and particularly to a pure copper plate for suppressing the coarsening of crystal grains during heating, copper / ceramic bonding bodies using this pure copper plate, and insulating circuit boards. This invention claims priority based on Japanese Patent Application No. 2020-038764, filed on March 6, 2020, the contents of which are incorporated herein by reference. [Previous Technology]

[0002] In the past, copper or copper alloys with high conductivity were used in electrical and electronic components such as heat sinks or thick copper circuits. Recently, with the increase in the current of electronic and electrical machines, due to the decrease in current density and the heat diffusion caused by Joule heating, there has been a trend of larger and thicker electrical and electronic components used in such electronic and electrical machines.

[0003] Here, in semiconductor devices, insulating circuit boards, such as those formed by bonding copper material to a ceramic substrate, are used to constitute the aforementioned heat sinks or thick copper circuits. When bonding the ceramic substrate and the copper plate, the bonding temperature is often 800°C or higher. During bonding, there is a concern that the crystal grains of the copper material forming the heat sink or thick copper circuit may become coarse. In particular, the crystal grains tend to coarsen easily in copper materials made of pure copper, which has excellent conductivity and heat dissipation.

[0004] In the heat sink or thick copper circuit after bonding, when the crystal grains become coarse, there are concerns about the appearance due to the coarsening of the crystal grains. For example, Patent Document 1 proposes a pure copper plate that inhibits the growth of crystal grains. Patent Document 1 describes a method where, by containing 0.0006 to 0.0015 wt% S, even after heat treatment at a recrystallization temperature or higher, the crystal grains can be adjusted to a certain size. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 06-002058 [Summary of the Invention]

[0006] [The problem the invention aims to solve]

[0007] However, in Patent Document 1, although the coarsening of crystal grains is suppressed by specifying the content of sulfur (S), the different heat treatment conditions mean that simply specifying the content of S is insufficient to achieve a sufficient effect in suppressing crystal grain coarsening. Furthermore, after heat treatment, localized crystal grain coarsening occurs, resulting in an uneven crystal structure. Moreover, increasing the content of S to suppress crystal grain coarsening significantly reduces hot workability, leading to a substantial decrease in the manufacturing yield of pure copper plates.

[0008] This invention is made in view of the above-mentioned circumstances, and aims to provide a pure copper plate with high conductivity that, after heat treatment, can suppress the coarsening and inhomogeneity of crystal grains, a copper / ceramic bonding body using this pure copper plate, and an insulating circuit board. [Means for solving the problem]

[0009] To solve this problem, the inventors, through professional review, made the following discoveries. In pure copper plates, trace amounts of impurity elements exist at the grain boundaries, exhibiting a grain growth inhibition effect that suppresses grain coarsening. Here, it was found that by utilizing elements with this grain growth inhibition effect (hereinafter referred to as grain growth inhibition elements), grain coarsening or inhomogeneity can also be suppressed after heat treatment. Furthermore, it was discovered that limiting the content of specific elements is effective in fully utilizing the effect of these grain growth inhibition elements. Moreover, it was discovered that suppressing the strain energy accumulated in the material at a low level is effective in suppressing the driving force of crystal growth during heating.

[0010] The present invention is based on the above-mentioned discovery. The pure copper plate of the present invention has a Cu content of 99.96 mass% or more, a total Ag, Sn and Fe content of 9.0 massppm or more but less than 100.0 massppm, a residual portion having an unavoidable composition of impurities, an average crystal grain size of 10.0 μm or more on the rolled surface, and crystals parallel to the rolled surface having {022}, {002}, {113}, {111}, and {133} crystals. When the diffraction peak intensity of each of the aforementioned crystal surfaces obtained by X-ray diffraction measurement using the 2θ / θ method on the aforementioned rolled surface is I{022}, I{002}, I{113}, I{111}, and I{133} respectively, it is characterized by satisfying the following condition.

[0011] When a pure copper plate is constructed according to this method, the Cu content is 99.96 mass% or more, and the total content of Ag, Sn, and Fe is 9.0 massppm or more but less than 100.0 massppm. Since the residual portion inevitably contains impurities, the coarsening of crystal grains can be suppressed by Ag, Sn, and Fe dissolving in the copper matrix. Furthermore, the conductivity of the pure copper plate can be ensured, making it suitable as a material for components used in high-current electronic and electrical machinery and for heat dissipation components.

[0012] Furthermore, since the average crystal grain size of the rolled surface is 10.0 μm or more, the grain size can be made larger in the state before heating, the driving force for recrystallization during heating is reduced, and particle growth is suppressed. Then, since the diffraction peak intensities I{022}, I{002}, I{113}, I{111}, and I{133} of the aforementioned crystal surfaces obtained by X-ray diffraction measurement using the 2θ / θ method for the aforementioned rolled surface have the above-mentioned relationship, the accumulated strain energy can be reduced, the driving force for recrystallization during heating is reduced, and particle growth is suppressed.

[0013] Here, in the pure copper plate of the present invention, the content of sulfur (S) is preferably in the range of 2.0 massppm to 20.0 massppm. At this point, as a grain growth inhibitor, by containing 2.0 massppm or more of S, the coarsening or unevenness of the grains can be reliably suppressed after heat treatment. Furthermore, by limiting the content of S to 20.0 massppm or less, hot workability can be sufficiently ensured.

[0014] Furthermore, in the pure copper plate of the present invention, the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y is preferably 15.0 massppm or less. As unavoidable impurities, the elements Mg, Sr, Ba, Ti, Zr, Hf, and Y segregate at the grain boundaries and form compounds with grain-growth-inhibiting elements (S, Se, Te, etc.), which inhibit grain coarsening, thus potentially hindering the effect of grain growth-inhibiting elements. Therefore, by limiting the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y to 15.0 massppm or less, the grain growth-inhibiting effect of the grain growth-inhibiting elements can be fully utilized, and after heat treatment, grain coarsening or inhomogenization can be reliably suppressed. However, grain coarsening-inhibiting elements (S, Se, Te, etc.) are unavoidable impurities.

[0015] Furthermore, in the pure copper plate of the present invention, after heat treatment at 800°C for 1 hour, the ratio of the maximum crystal grain size dmax to the average crystal grain size dave within a 50mm × 50mm area is preferably 20.0 or less, and the average crystal grain size dave is preferably 500μm or less. At this time, heating under the above conditions can effectively suppress the coarsening and unevenness of the crystal grains, and further suppress the occurrence of appearance defects.

[0016] Furthermore, in the pure copper plate of the present invention, it is preferable that the Vickers hardness is below 150 HV. At this point, the Vickers hardness is below 150 HV, which is sufficiently soft, ensuring the characteristics of a pure copper plate, and thus making it particularly suitable as a material for electrical and electronic components used in high-current applications.

[0017] The copper / ceramic bonding system of the present invention is characterized by bonding the aforementioned pure copper plate and ceramic component. When the copper / ceramic bond body is constructed according to this, even during pressure heat treatment, the local coarsening of the crystal grains of the pure copper plate is suppressed, thereby preventing poor bonding or poor appearance and the occurrence of defects in the inspection process.

[0018] The copper / ceramic bonding system of the present invention is characterized by bonding the aforementioned pure copper plate and ceramic component. When an insulating circuit board with this configuration is used to bond the pure copper plate and the ceramic substrate, even during pressure heat treatment, the localized coarsening of the crystal grains in the pure copper plate is suppressed, thereby preventing poor bonding or appearance defects and ensuring proper inspection. [Effects of the Invention]

[0019] According to the present invention, a pure copper plate with high conductivity and which can suppress grain coarsening and non-uniformity after heat treatment is provided, a copper / ceramic bonding body using the pure copper plate, and an insulating circuit board are provided.

Implementation Method

[0020] Hereinafter, a pure copper plate according to one embodiment of the present invention will be described. The pure copper plate of this embodiment is used as a material for electrical and electronic components such as heat sinks or thick copper circuits. When forming the aforementioned electrical and electronic components, it can be bonded to a ceramic substrate for example.

[0021] The pure copper plate of this embodiment contains Cu of 99.96 mass% or more, and Ag, Sn and Fe of a total content of 9.0 massppm or more but less than 100.0 massppm, with the residue containing unavoidable impurities. Hereinafter, "mass%" and "massppm" will be referred to as "%" and "ppm" respectively.

[0022] However, in the pure copper plate of this embodiment, the content of S is preferably in the range of 2.0 massppm to 20.0 massppm. Furthermore, in the pure copper plate of this embodiment, the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y (A element group) is preferably 15.0 massppm or less.

[0023] Furthermore, in the pure copper plate of this embodiment, the average grain size of the crystal grains on the roll-pressed surface is 10.0 μm or more. The average grain size of the crystal grains on the roll-pressed surface can be, for example, the average value of the grain size of the crystals measured at three equidistant points from the center of the roll-pressed surface. Then, in the pure copper plate of this embodiment, the crystal surfaces parallel to the roll-pressed surface have {022}, {002}, {113}, {111}, and {133} crystals. When the diffraction peak intensity of each crystal surface obtained by X-ray diffraction measurement of the aforementioned roll-pressed surface using the 2θ / θ method becomes I{022}, I{002}, I{113}, I{111}, and I{133} respectively, the following relationships (1) to (3) are satisfied.

[0024] However, in the pure copper plate of this embodiment, the ratio of the maximum crystal grain size dmax to the average crystal grain size dave within a 50mm × 50mm area after heat treatment at 800°C for 1 hour, dmax / dave, is preferably 20 or less, and the average crystal grain size dave is preferably 500μm or less. The maximum crystal grain size dmax is determined by selecting any area of ​​50mm × 50mm, and measuring the grain size of crystals at at least three locations within this area, selecting the largest of the measured grain sizes. Furthermore, in the pure copper plate of this embodiment, a Vickers hardness of 150HV or less is preferred. Moreover, in the pure copper plate of this embodiment, a conductivity of 97% IACS or higher is preferred.

[0025] Hereinafter, the reasons for specifying the composition, crystal orientation and various properties as described above in the pure copper plate of this embodiment are explained as follows.

[0026] (Cu purity: 99.96 mass% or higher) In electrical and electronic components used for high-current applications, excellent conductivity and heat dissipation are required to suppress heat generation during energization. Therefore, pure copper with particularly excellent conductivity and heat dissipation is preferred. Furthermore, when bonding to ceramic substrates, low deformation resistance is preferable to mitigate thermal strain generated under cyclic loading. In this embodiment, the purity of Cu in the pure copper plate is specified to be 99.96 mass% or higher. However, a Cu purity of 99.965 mass% or higher is preferred, and more preferably 99.97 mass% or higher. While no specific upper limit is imposed on the Cu purity, exceeding 99.999 mass% requires special refining processes, significantly increasing manufacturing costs; therefore, 99.999 mass% or lower is preferred.

[0027] (Total content of Ag, Sn, and Fe: 9.0 massppm or more, less than 100.0 massppm) Ag, Sn, and Fe are elements that, through solid solution into the copper matrix, have the effect of suppressing grain coarsening. Therefore, in this embodiment, when the content of Ag, Sn, and Fe is 9.0 massppm or more, the grain coarsening suppression effect of Ag, Sn, and Fe can be fully utilized, and grain coarsening can be reliably suppressed even after heat treatment. On the other hand, due to concerns about increased manufacturing costs or decreased conductivity from the necessary addition, the total content of Ag, Sn, and Fe is kept below 100.0 massppm. However, the lower limit of the total content of Ag, Sn, and Fe is preferably 9.5 massppm or more, and more preferably 10.0 massppm or more. On the other hand, the upper limit of the total content of Ag, Sn and Fe is preferably less than 80.0 massppm, and more preferably less than 60.0 massppm. In particular, the total content of Sn and Fe, which greatly reduces conductivity, is preferably less than 30.0 massppm.

[0028] (S content: 2.0 massppm to 20.0 massppm) S is an element that, by inhibiting grain boundary movement, has the effect of suppressing grain coarsening, which can reduce hot workability. Therefore, in this embodiment, when the S content is 2.0 massppm or more, the grain coarsening suppression effect of S can be fully utilized, and grain coarsening can be reliably suppressed after heat treatment. On the other hand, when the S content is limited to 20.0 massppm or less, hot workability can be ensured. However, the lower limit of the S content is preferably 2.5 massppm or more, and more preferably 3.0 massppm or more. Furthermore, the upper limit of the S content is preferably 17.5 massppm or less, and more preferably 15.0 massppm or less.

[0029] (Total content of Mg, Sr, Ba, Ti, Zr, Hf, Y (Group A elements): 15.0 massppm or less) As unavoidable impurities, one or more of Mg, Sr, Ba, Ti, Zr, Hf, and Y (Group A elements) segregate at the grain boundaries and form compounds with grain-growth-inhibiting elements (S, Se, Te, etc.) that inhibit grain growth, raising concerns about their role in hindering grain growth. Therefore, to reliably suppress grain coarsening after heat treatment, it is preferable that the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y (Group A elements) be 15.0 massppm or less. However, the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y (A element group) is preferably below 10.0 massppm, more preferably below 7.5 massppm, and most preferably below 5.0 massppm.

[0030] (Other Elements) However, Al, Cr, P, Be, Cd, Mg, Ni, and Pb (Group M elements) have the effect of solid solution or grain boundary segregation in the copper matrix, and further inhibit grain growth through the formation of oxides. Therefore, in order to effectively suppress the coarsening of crystal grains after heat treatment, it is preferable that the total content of Al, Cr, P, Be, Cd, Mg, Ni, and Pb (Group M elements) exceeds 2.0 massppm. However, when Al, Cr, P, Be, Cd, Mg, Ni, and Pb (Group M elements) are intentionally included, it is preferable that the lower limit of the total content of Al, Cr, P, Be, Cd, Mg, Ni, and Pb (Group M elements) is 2.1 massppm or more, more preferably 2.3 massppm or more, even more preferably 2.5 massppm or more, and most preferably 3.0 massppm or more. On the other hand, there are concerns that the conductivity may decrease when Al, Cr, P, Be, Cd, Mg, Ni, and Pb (M element group) are present. Therefore, it is preferable that the total content of Al, Cr, P, Be, Cd, Mg, Ni, and Pb (M element group) is less than 100.0 massppm, more preferably less than 50.0 massppm, even more preferably less than 20.0 massppm, and even more preferably less than 10.0 massppm.

[0031] (Other unavoidable impurities) Other unavoidable impurities besides the elements mentioned above include B, Bi, Ca, Sc, rare earth elements, V, Nb, Ta, Mo, W, Mn, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, Au, Zn, Hg, Ga, In, Ge, As, Sb, Tl, N, C, Si, Li, H, and O. These unavoidable impurities may cause a decrease in conductivity, so the fewer they are, the better.

[0032] (Average grain size of the rolled surface: 10 μm or more) In the pure copper plate of this embodiment, when the average grain size of the rolled surface is fine, recrystallization is easily carried out when the pure copper plate is heated, which may promote grain growth and cause unevenness in the structure. Therefore, in order to further suppress the coarsening of the grains during heating, it is preferable that the average grain size of the rolled surface is 10 μm or more. However, it is preferable that the average grain size of the rolled surface is 15 μm or more, and more preferably 20 μm or more.

[0033] I{022} / (I{022}+I{002}+I{113}+I{111}+I{133})≦0.15 In the roll forming surface, the {220} surface is formed at the crystallization position during roll forming. The higher the proportion of the {220} surface, the higher the strain energy accumulated in the material. Here, when the strain energy of the material is high, the driving force for recrystallization becomes high, and the crystal grains tend to coarsen during heating. Therefore, in order to suppress the coarsening of crystal grains, in this embodiment, I{022} / (I{022}+I{002}+I{113}+I{111}+I{133})) is made to be 0.15 or less. Here, it is preferable that (I{022} / (I{022}+I{002}+I{113}+I{111}+I{133}) is less than 0.12, and more preferably less than 0.10.

[0034] (I{002} / I{111}≧10.0, I{002} / I{113}≧15.0) The {002} facet is the crystal orientation formed during recrystallization. By increasing the proportion of the {111} or {113} facets that are easily formed during processing, the strain energy in the material that drives recrystallization is suppressed, thereby suppressing the coarsening of crystal grains. Therefore, in this embodiment, I{002} / I{111} is 10.0 or more, and I{002} / I{113} is 15.0 or more. Here, it is preferable that I{002} / I{111} is 11.0 or more, and more preferably 12.0 or more. Also, it is preferable that I{002} / I{113} is 16.0 or more, and more preferably 17.0 or more.

[0035] (Average grain size after heat treatment at 800°C for 1 hour: 500 μm or less) In the pure copper plate of this embodiment, when the average grain size after heat treatment at 800°C for 1 hour is 500 μm or less, even when heated to above 800°C, the coarsening of the grains can be reliably suppressed, making it particularly suitable as a material for thick copper circuits or heat sinks bonded to ceramic substrates. However, the upper limit of the average grain size after heat treatment at 800°C for 1 hour is preferably 450 μm or less, and more preferably 400 μm or less.

[0036] (dmax / dave after heat treatment at 800°C for 1 hour: 20.0 or less) In the pure copper plate of this embodiment, when the ratio dmax / dave of the maximum crystal grain size dmax to the average crystal grain size dave in a 50mm×50mm area after heat treatment at 800°C for 1 hour is 20.0 or less, the non-uniformity of the crystal grains can be reliably suppressed even when heated to above 800°C, making it particularly suitable as a material for thick copper circuits or heat sinks bonded to ceramic substrates. However, it is preferable that the ratio dmax / dave of the maximum crystal grain size dmax to the average crystal grain size dave in a 50mm×50mm area after heat treatment at 800°C for 1 hour is 18.0 or less, and more preferably 15.0 or less.

[0037] (Vickers hardness: 150 HV or less) In this embodiment of the pure copper sheet, by setting the Vickers hardness to 150 HV or less, the properties of pure copper sheet are ensured, making it particularly suitable as a material for electrical and electronic components used in high-current applications. Furthermore, it is sufficiently flexible to be bonded to other components such as ceramic substrates under thermal cycles, thus relieving thermal strain caused by deformation of the pure copper sheet. However, a Vickers hardness of 140 HV or less is preferred for the pure copper sheet, more preferably 130 HV or less, and most preferably 110 HV or less. Although the lower limit of the Vickers hardness of the pure copper sheet is not specifically limited, if the hardness is too low, it is easy to deform during manufacturing, making processing more difficult; therefore, 30 HV or more is preferred, more preferably 45 HV or more, and most preferably 60 HV or more.

[0038] (Conductivity: 97% IACS or higher) In this embodiment of the pure copper plate, by achieving a conductivity of 97% IACS or higher, the characteristics of a pure copper plate are ensured, making it particularly suitable as a material for components used in electronic and electrical machinery and for heat dissipation in high-current applications. However, a conductivity of 98% IACS or higher is preferred for the pure copper plate, and more preferably 99% IACS or higher. No specific upper limit is imposed on the conductivity of the pure copper plate.

[0039] Next, the manufacturing method of the pure copper plate of this embodiment will be described with reference to the flowchart shown in FIG1.

[0040] (Melting and Casting Process S01) First, copper raw materials are melted to produce a copper molten metal. However, it is preferable to use 4NCu with a purity of 99.99 mass% or higher, or 5NCu with a purity of 99.999 mass% or higher, as the copper raw material. However, when adding sulfur, sulfur monomer or Cu-S master alloy can be used. However, when manufacturing the Cu-S master alloy, it is also preferable to use 4NCu with a purity of 99.99 mass% or higher, or 5NCu with a purity of 99.999 mass% or higher. Furthermore, in the melting process, to reduce the hydrogen concentration, melting is performed in an inactive gas environment with low H2O vapor pressure (e.g., Ar gas), and the holding time during melting is kept to a minimum. Then, the copper molten metal with adjusted composition is poured into a mold to produce a cast block. However, considering mass production, continuous casting or semi-continuous casting is preferable.

[0041] (Hot Working Process S02) Next, hot working is performed to homogenize the microstructure. While there are no particular restrictions on the hot working temperature, a range of 500°C to 1000°C is preferred. Furthermore, the total processing yield of the hot working is preferably 50% or higher, more preferably 60% or higher, and even more preferably 70% or higher. Moreover, while there are no particular restrictions on the cooling method after hot working, air cooling or water cooling is preferred. Furthermore, while there are no particular restrictions on the processing method in Hot Working Process S02, methods such as rolling, extrusion, groove rolling, forging, and pressurization can be used. When the final shape is a sheet or strip, rolling is preferred; when the final shape is a block, forging or pressurization is preferred.

[0042] (Intermediate Roll Forming Process S03) Next, the copper material after the heat treatment process S02 is subjected to intermediate rolling to process it into a specific shape. However, although the temperature conditions for this intermediate rolling process S03 are not particularly limited, it is preferable to perform it in a range of -200°C to 200°C. Furthermore, the processing rate of this intermediate rolling process S03 is appropriately selected to approximate the final shape, but to improve productivity, it is preferable to be 30% or more.

[0043] (Recrystallization Heat Treatment Process S04) Next, the copper material after the intermediate rolling process S03 is subjected to a heat treatment for recrystallization. Here, it is preferable that the average grain size of the recrystallized grains on the rolling surface is 10 μm or more. If the recrystallized grains are fine, there is a concern that subsequent heating to 800°C or higher may promote grain growth and lead to uneven microstructure. While the heat treatment conditions for the recrystallization heat treatment process S04 are not specifically limited, it is preferable to maintain a heat treatment temperature in the range of 200°C to 900°C for 1 second to 10 hours. For example, heat treatment at 350°C for 6 hours, at 700°C for 1 minute, or at 850°C for 5 seconds may be performed. Furthermore, to achieve uniform recrystallized microstructure, the intermediate rolling process S03 and the recrystallization heat treatment process S04 may be repeated two or more times.

[0044] (Temperature Processing Process S05) Next, to adjust the material strength, the copper material after the recrystallization heat treatment process S04 may be subjected to tempering. However, if it is not necessary to improve the material strength, tempering may not be performed. Although the tempering rate is not specifically limited, it is preferable to perform it within a range of more than 0% to less than 50% in order to adjust the material strength. Furthermore, it is preferable to limit the processing rate to more than 0% to less than 40% when the material strength is further reduced, and when I{022} / (I{022}+I{002}+I{113}+I{111}+I{133}) becomes less than 0.15, and when I{002} / I{111} becomes more than 10 and I{002} / I{113} becomes more than 15. Also, if necessary, heat treatment may be performed after tempering to remove residual strain.

[0045] Through the above processes, a pure copper plate of this embodiment is manufactured.

[0046] In the pure copper plate of this embodiment with the above-described structure, the Cu content is 99.96 mass% or more, and the total content of Ag, Sn, and Fe is 9.0 massppm or more but less than 100.0 massppm. Since the residue inevitably contains impurities, the coarsening of crystal grains can be suppressed by Ag, Sn, and Fe dissolving in the copper matrix. Furthermore, since the average crystal grain size of the rolled surface is 10 μm or more, the grain size can be made larger in the state before pressure heating treatment, the driving force for recrystallization during pressure heating is reduced, and particle growth is suppressed.

[0047] In the pure copper plate of this embodiment, the diffraction peak intensities I{022}, I{002}, I{113}, I{111}, and I{133} of each crystal plane obtained by X-ray diffraction measurement of the roll-pressed surface using the 2θ / θ method have the relationship I{022} / (I{022}+I{002}+I{113}+I{111}+I{133})≦0.15, which reduces the accumulated strain energy, decreases the driving force for recrystallization during heating, and inhibits particle growth.

[0048] Furthermore, in the pure copper plate of this embodiment, since I{002} / I{111} is 10 or more and I{002} / I{113} is 15 or more, the proportion of the {002} facets formed during recrystallization is greater than that of the {111} or {113} facets that are easy to form during processing. This suppresses the strain energy in the material that drives recrystallization during bonding, thereby suppressing the coarsening of crystal grains.

[0049] Furthermore, in this embodiment, when the content of S is in the range of 2.0 massppm to 20.0 massppm, S, one of the grain growth inhibitory elements, will segregate at the grain boundaries, which can effectively suppress the coarsening or inhomogenization of the grains during heating. In addition, hot workability can be ensured.

[0050] Furthermore, in this embodiment, when the total content of Mg, Sr, Ba, Ti, Zr, Hf, and Y (group A elements) is 15.0 massppm or less, the reaction between these group A elements and grain growth inhibiting elements such as S, Se, and Te can be suppressed to form compounds, thus fully leveraging the role of grain growth inhibiting elements. Therefore, the coarsening and inhomogenization of crystal grains during heating can be effectively suppressed.

[0051] Furthermore, in this embodiment, when the ratio of the maximum crystal grain size dmax to the average crystal grain size dave within a 50mm×50mm area after heat treatment at 800℃ for 1 hour is dmax / dave or less, and the average crystal grain size dave is 500μm or less, the coarsening and unevenness of the crystal grains can be effectively suppressed after heat treatment, and the occurrence of poor appearance can be suppressed.

[0052] Furthermore, in this embodiment, when the Vickers hardness is below 150 HV, it is sufficiently soft, ensuring the properties of a pure copper plate, making it particularly suitable as a material for electrical and electronic components used in high-current applications.

[0053] However, in this embodiment, when Al, Cr, P, Be, Cd, Mg, Ni, Pb (M element group) contain more than 2.0 massppm, the solid solution or grain boundary segregation in the element parent phase of the M element copper group, and the formation of oxides, can more effectively suppress grain growth after heat treatment.

[0054] Although the pure copper plate of the present invention has been described above, the present invention is not limited thereto, and appropriate modifications can be made without departing from the technical concept of the invention. For example, in the above embodiment, one example of a method for manufacturing a pure copper plate has been described, but the method for manufacturing a pure copper plate is not limited to that described in the embodiment, and an existing manufacturing method can be appropriately selected for manufacturing. [Example]

[0055] Hereinafter, the results of the confirming experiments conducted to verify the effects of the present invention will be described. A copper raw material with a purity of 99.999 mass% or higher was prepared, along with a Cu-1 mass% master alloy of various elements made using the aforementioned copper raw material and various elements with a purity of 99 mass% or higher. The aforementioned copper raw material was placed in a high-purity graphite crucible and subjected to high-frequency melting in an ambient furnace under an Ar gas atmosphere. The Cu-1 mass% master alloy of the aforementioned various elements was added to the resulting molten copper to prepare a specific composition. The resulting molten copper was poured into a mold to produce a mold block. However, the size of the mold block was approximately 100 mm thick × 120 mm wide × 150-200 mm long.

[0056] The resulting mold block was heated for 1 hour in an Ar gas environment at the temperatures recorded in Tables 1 and 2, and then hot-rolled to a thickness of 50 mm. Simultaneously, the copper material after hot rolling was cut, and surface grinding was performed to remove the oxide film on the surface. At this time, considering the rolling ratios of subsequent hot rolling, intermediate rolling, and tempering rolling, the thickness of the copper material supplied for intermediate rolling was adjusted to achieve the final thickness shown in Tables 1 and 2.

[0057] For the copper material with the thickness adjusted as described above, intermediate rolling is performed under the conditions described in Tables 1 and 2, followed by water cooling. Next, the copper material after intermediate rolling is subjected to recrystallization heat treatment under the conditions described in Tables 1 and 2. Then, the copper material after recrystallization heat treatment is subjected to temper rolling under the conditions described in Tables 1 and 2, and a strip with a width of 60 mm is manufactured to the thickness shown in Tables 3 and 4 for characteristic evaluation.

[0058] Then, an evaluation is carried out for the following items.

[0059] (Composition Analysis) Samples were taken from the obtained casting block for analysis. S was determined using infrared absorption spectrometry, and other elements were determined using glow discharge mass spectrometry (GD-MS). However, the measurements were performed at two locations: the center of the sample and the end in the width direction. The sample containing the higher concentration was taken as the total content of the sample. The results are shown in Tables 1 and 2.

[0060] (Processability Assessment) As a processability assessment, the presence or absence of edge cracks in the aforementioned hot rolling and intermediate rolling processes is observed. Let "A" represent edge cracks that are visually absent or barely detectable; "B" represent edge cracks with a length less than 1 mm; and "C" represent edge cracks with a length of 1 mm or more. However, the length of the edge crack is the length of the edge crack extending from the end of the rolled material in the width direction towards the center of the width direction.

[0061] (Vickers Hardness) The Vickers hardness was determined according to the micro Vickers hardness test method specified in JIS Z 2244, with a test load of 0.98 N. However, the test location was the roll-pressed surface of the test piece used for characteristic evaluation. The evaluation results are shown in Tables 3 and 4.

[0062] (Conductivity) A test piece with a width of 10 mm and a length of 60 mm was taken from the strip used for characteristic evaluation, and the resistance was obtained using the 4-terminal method. Furthermore, the dimensions of the test piece were measured using a micrometer, and the volume of the test piece was calculated. Then, the conductivity was calculated from the measured resistance value and volume. The evaluation results are shown in Tables 3 and 4. However, the test piece was taken with its length direction parallel to the rolling direction of the strip used for characteristic evaluation.

[0063] (Average crystal grain size before heat treatment at 800℃ for 1 hour) A 20mm × 20mm sample was cut from the obtained characteristic evaluation strip and the average crystal grain size was measured using a SEM-EBSD (Electron Backscatter Diffraction Patterns) measuring device. The roller-pressed surface was mechanically ground using water-resistant abrasive paper and diamond abrasive grains, followed by final grinding using a colloidal silica solution. Subsequently, using a scanning electron microscope, electron beams were irradiated at each measurement point (pixel) within the measurement range on the sample surface. The orientation resolution formed by the backscattered electron beams determined that the orientation difference between adjacent measurement points was greater than 15˚, and the measurement points were designated as large grain boundaries, while those less than 15˚ were designated as small grain boundaries. Using large-angle grain boundaries, a grain boundary map was created. According to the cutting method of JIS H 0501, five lines of specific length were drawn for each grain boundary map, both longitudinal and transverse. The number of grains completely cut out was counted, and the average value of the cut length was recorded as the grain size before heat treatment. The evaluation results are shown in Tables 3 and 4.

[0064] (X-ray diffraction intensity) Let the X-ray diffraction intensity of the {111} surface of the plate be I{111}, let the X-ray diffraction intensity from the {002} surface be I{002}, let the X-ray diffraction intensity from the {022} surface be I{022}, let the X-ray diffraction intensity from the {113} surface be I{113}, and let the X-ray diffraction intensity from the {133} surface be I{133}. The intensity is measured using the integral intensity method in the following procedure. A test specimen is taken from the characteristic evaluation strip, and the X-ray diffraction intensity around one axis of rotation of the test specimen is measured using the reflection method. A Cu target is used, and Kα X-rays are used. Measurements were performed under the following conditions: tube current 40mA, tube voltage 40kV, measurement angle 40~150˚, and measurement step 0.02˚. After removing the background of the X-ray diffraction intensity from the contours of the diffraction angle and X-ray diffraction intensity, the integrated X-ray diffraction intensity of Kα1 and Kα2, which are merged from the peaks of each diffraction plane, was obtained. Then, I{022} / (I{022}+I{002}+I{113}+I{111}+I{133}), I{002} / I{111}, and I{002} / I{113} were calculated.

[0065] (Average grain size after heat treatment at 800°C for 1 hour) A 60mm × 60mm sample was cut from the strip used for the above characteristic evaluation and subjected to heat treatment at 800°C for 1 hour. From this test piece, a 50mm × 50mm sample was cut. The rolled surface was mirror-polished and etched, and photographed under an optical microscope with the rolling direction aligned with the transverse direction of the image. Among the observation areas, the area with the finest grains, forming uniform grain size within a field of view of approximately 1mm², was selected for observation and measurement. Then, according to the cutting method of JIS H 0501, five lines of specific length were drawn in both the longitudinal and transverse directions of the image. The number of completely cut grains was counted, and the average value of these cut lengths was recorded as the average grain size after heat treatment. The evaluation results are shown in Tables 3 and 4.

[0066] (Difference in average particle size after heat treatment at 800°C for 1 hour) As described above, for a sample taken from a heat-treated test piece, within a 50mm × 50mm area, twinning is removed, and the average of the major axis of the largest crystal grain and the minor axis cut off by the grain boundary when a line perpendicular to this is drawn is taken as the maximum crystal grain size dmax. When the ratio of this maximum crystal grain size to the above-mentioned average crystal grain size dave, dmax / dave, is 15.0 or less, it is evaluated as "0", when dmax / dave is more than 15.0 but less than 20.0, it is evaluated as "△", and when dmax / dave is more than 20.0, it is evaluated as "×".

[0067]

[0068]

[0069]

[0070]

[0071] In Comparative Example 1, the total content of Ag, Sn, and Fe was less than that of the present invention. Therefore, the average crystal grain size before heat treatment at 800°C for 1 hour was less than 10 μm. After heat treatment at 800°C for 1 hour, the average crystal grain size increased to over 500 μm, and the uniformity of grain size also increased. In Comparative Example 2, the total content of Ag, Sn, and Fe was greater than that of the present invention, resulting in lower conductivity. In Comparative Example 3, I{O22} / (I{O22}+I{O02}+I{I13}+I{I111}+I{I133}) exceeded 0.15, while I{O02} / I{I111} was less than 10, and I{O02} / I{I113} was less than 15. Therefore, after heat treatment, the crystal grains became coarser, and the uniformity of grain size also increased.

[0072] In this regard, in Examples 1-27 of the present invention, the average grain size after heat treatment is small, and the grain size inhomogeneity is also reduced. Furthermore, the conductivity also becomes 97% IACS or higher. Based on the above description, according to the present invention, it can be confirmed that a pure copper plate with excellent conductivity is provided, and that grain coarsening and inhomogeneity can be suppressed after heat treatment. [Simplified Explanation of the Diagram]

[0073] [Figure 1] Flowchart of the manufacturing method of pure copper plate in this embodiment.

Claims

1. A pure copper plate, characterized in that the Cu content is 99.96 mass% or more, the total content of Ag, Sn and Fe is 9.0 massppm or more but less than 100.0 massppm, the residue contains unavoidable impurities, the average grain size of the crystal grains on the rolled surface is 10 μm or more, and the crystal planes parallel to the rolled surface have {022}, {002}, {113}, {111}, and {133} crystal planes, such that the diffraction peak intensities of the aforementioned crystal planes obtained by X-ray diffraction measurement using the 2θ / θ method on the aforementioned rolled surface are respectively I{022}, I{002}, I{113}, I{111}, and I{133}. Satisfies I{022} / (I{022}+I{002}+I{113}+I{111}+I{133})≦0.15, I{002} / I{111}≧10.0, I{002} / I{113}≧15.

0.

2. The pure copper plate as described in claim 1, wherein, The content of sulfur is in the range of 2.0 massppm to 20.0 massppm.

3. The pure copper plate as described in claim 1 or 2, wherein, The content of Mg, Sr, Ba, Ti, Zr, Hf, and Y is below 15.0 mass ppm.

4. The pure copper plate described in any of claims 1 to 3, wherein, After heat treatment at 800℃ for 1 hour, the ratio of the maximum crystal grain size dmax to the average crystal grain size dave within a 50mm×50mm area is dmax / dave or less, and the average crystal grain size dave is 500μm or less.

5. The pure copper plate described in any of claims 1 to 4, wherein, Its Vickers hardness is below 150 HV.

6. A copper / ceramic joint, characterized in that it is formed by joining a pure copper plate as described in any one of claims 1 to 5 and a ceramic component.

7. An insulating circuit board, characterized in that a pure copper plate as described in any one of claims 1 to 5 is bonded to the surface of a ceramic substrate.

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