CN114269957A

CN114269957A - Pure copper plate

Info

Publication number: CN114269957A
Application number: CN202080059341.XA
Authority: CN
Inventors: 森广行; 松永裕隆
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2019-09-27
Filing date: 2020-09-11
Publication date: 2022-04-01
Anticipated expiration: 2040-09-11
Also published as: EP4036261A4; US20220403484A1; JPWO2021060023A1; EP4036261A1; CN114269957B; KR20220068985A; JP6973680B2; TW202115264A; WO2021060023A1

Abstract

The Cu content of the pure copper plate is 99.96 mass% or more, and 1X 10 is the average grain size of crystal grains in a rolled surface is X [ mu ] m, and the Ag content is Y mass ppm^‑8≤X^‑3Y^‑1≤1×10^‑5It is true that NF represents the ratio of J3 in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries to all the grain boundary triple points_J3J2 in which two grain boundaries constituting the grain boundary triple point are special grain boundaries and one grain boundary is a random grain boundary, and all the grain boundariesThe ratio of triple points is NF_J20.30 < (NF) > (NF_J2/(1‑NF_J3))^0.5Less than or equal to 0.48.

Description

Pure copper plate

Technical Field

The present invention relates to a pure copper plate suitable for use in an electric/electronic component such as a heat sink or a thick copper circuit, and more particularly to a pure copper plate in which coarsening of crystal grains during heating is suppressed.

The present application claims priority based on patent application No. 2019-176835, filed in japan on 27/9/2019, and the contents of which are incorporated herein by reference.

Background

Conventionally, in an electric and electronic component such as a heat sink or a thick copper circuit, copper or a copper alloy having high conductivity has been used.

Recently, with the increase in current of electronic devices, electric devices, and the like, there have been attempts to increase or thicken electric and electronic components used in these electronic devices, electric devices, and the like for the purpose of reducing current density and diffusing heat due to joule heating.

In the semiconductor device, for example, a copper plate material is bonded to a ceramic substrate, and an insulating circuit board or the like provided with the copper plate material is used as the heat sink or the thick copper circuit.

When a ceramic substrate and a copper plate are bonded, the bonding temperature is often 800 ℃ or higher, and there is a possibility that the crystal grains of the copper material constituting a heat sink or a thick copper circuit become coarse during bonding. In particular, in a copper plate made of pure copper having particularly excellent electrical conductivity and heat dissipation properties, crystal grains tend to be coarsened easily. Further, when the joined copper plate materials are manufactured by press working, the burr height increases as the plate becomes thicker.

When the crystal grain is coarsened in the bonded heat sink or thick copper circuit, there is a possibility that the crystal grain is coarsened to cause a problem in appearance.

Here, for example, patent document 1 proposes a pure copper plate material in which grain growth is suppressed.

Patent document 1 describes that crystal grains having a constant size can be adjusted by containing 0.0006 wt% to 0.0015 wt% of S even when heat treatment is performed at a temperature equal to or higher than the recrystallization temperature.

In patent document 1, coarsening of crystal grains is suppressed by defining the content of S, but the effect of suppressing coarsening of crystal grains cannot be sufficiently obtained by defining only the content of S depending on the heat treatment conditions. After the heat treatment, local crystal grains are coarsened and the crystal structure may become uneven.

Further, in order to suppress coarsening of crystal grains, when the content of S is increased, hot workability is greatly reduced, and the production yield of the pure copper plate is greatly reduced.

Patent document 1: japanese laid-open patent publication No. H06-002058

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pure copper plate having high electrical conductivity and capable of suppressing coarsening and non-uniformity of crystal grains even after heat treatment.

As a result of intensive studies to solve the problem, the present inventors have found that: by adjusting the average grain size of the crystal grains and the content of Ag in the rolled surface and further appropriately controlling the grain boundaries constituting the triple points of the grain boundaries, coarsening and unevenness of the crystal grains can be suppressed even after the heat treatment.

In the present specification, the meaning of suppressing the growth of crystal grains is the same as that of suppressing the coarsening of crystal grains.

The present invention has been made in view of the above-mentioned findings, and a pure copper plate according to an aspect of the present invention is characterized in that the content of Cu is 99.96 mass% or more, the following relational expression holds when the average crystal grain size of crystal grains in a rolled surface is X μm, and the content of Ag is Y mass ppm,

1×10^-8≤X^-3Y^-1≤1×10^-5

the surface perpendicular to the width direction of rolling was set to 10000 μm as an observation surface²Measuring the parent phase in steps of 0.25 μm measurement intervals in the above measurement area by EBSD method, analyzing the measurement result by OIM to obtain CI value of each measurement point, excluding the measurement points with CI value of 0.1 or less, analyzing the orientation difference of each crystal grain to make the orientation difference between adjacent measurement points 15 ° or moreThe boundary between the measurement points of (a) is defined as a grain boundary, the average grain diameter A is obtained by Area Fraction (Area Fraction), the parent phase is measured by the EBSD method at measurement intervals of one tenth or less of the average grain diameter A, and the number of the crystal grains is 10000 [ mu ] m in a plurality of visual fields so that the parent phase contains 1000 or more crystal grains in total²The above measurement area is obtained by subjecting the measurement results to OIM analysis by data analysis software to obtain CI values of the respective measurement points, and orientation difference analysis of the respective crystal grains is performed while excluding the measurement points having CI values of 0.1 or less, and when a boundary between the measurement points in which the orientation difference between adjacent measurement points is 15 ° or more is defined as a grain boundary, a corresponding grain boundary of Σ 29 or less is defined as a special grain boundary, and the other grain boundaries are defined as random grain boundaries, in the grain boundary triple points by the OIM analysis, the proportion of J3, in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries, to all the grain boundary triple points is defined as NF 3_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2When the temperature of the water is higher than the set temperature,

0.30＜(NF_J2/(1-NF_J3))^0.5less than or equal to 0.48.

The EBSD method is an Electron reflection Diffraction (EBSD) method using a scanning Electron microscope with a back-scattered Electron Diffraction Imaging system, and OIM is data analysis software (OIM) for analyzing crystal Orientation using measurement data based on EBSD. Further, the CI value is a reliability Index (Confidence Index), and is a value displayed as a value indicating reliability of crystal orientation when analyzed by using Analysis software oil Analysis (ver.7.3.1) of an EBSD device (for example, "EBSD this: oil を uses するにあたって (modified version 3)" wood cleaner, 9 months 2009, company TSL ソリューションズ manufacturer [ "EBSD reader: suzuki cleaner when using oil (modified version 3)," tsuki Solutions co., ltd. issue ]).

Here, when the structure of the measurement point measured by the EBSD method and analyzed by OIM is a processed structure, the reliability of determining the crystal orientation is low and the CI value is low because the crystal pattern is not clear. In particular, when the CI value is 0.1 or less, the tissue at the measurement point is determined to be a processed tissue.

And, the special grain boundaries are defined as the following grain boundaries: crystallographically, the value Σ defined according to CSL theory (Kronberg et al: trans. Met. Soc. AIME,185,501(1949)) belongs to the corresponding grain boundary of 3 ≦ Σ ≦ 29, and the lattice orientation defect Dq at the inherent corresponding site in the corresponding grain boundary satisfies Dq ≦ 15 °/Σ^1/2(D.G.Brandon: acta.Metallurgica.Vol.14, p.1479, (1966)).

On the other hand, the random grain boundaries mean that Dq.ltoreq.15 °/Σ is satisfied in addition to the correspondence of orientation relationship that Σ is 29 or less^1/2The grain boundaries other than the special grain boundaries. That is, the special grain boundaries belong to a corresponding orientation relationship in which the Σ value is 29 or less and satisfy Dq ≦ 15 °/Σ^1/2The grain boundaries other than the special grain boundaries are random grain boundaries.

In addition, as the grain boundary triple point, there are four types as follows: j0 with all three grain boundaries being random grain boundaries, J1 with 1 grain boundary being a special grain boundary and two grain boundaries being random grain boundaries, J2 with two grain boundaries being special grain boundaries and one grain boundary being random grain boundaries, and J3 with all three grain boundaries being special grain boundaries.

Therefore, when the total number of J0 is Σ J0, the total number of J1 is Σ J1, the total number of J2 is Σ J2, and the total number of J3 is Σ J3, the proportion NF of J3, in which all three grain boundaries constituting grain boundary triple points are special grain boundaries, to all grain boundary triple points is NF 3_J3(the ratio of the number of J3 to the number of all grain boundary triple points) is defined as NF_J3＝ΣJ3/(ΣJ0+ΣJ1+ΣJ2+ΣJ3)。

Further, the proportion NF of J2 in which two grain boundaries constituting the grain boundary triple points are special grain boundaries and one grain boundary is a random grain boundary to all the grain boundary triple points_J2(the ratio of the number of J2 to the number of all grain boundary triple points), and is defined as NF_J2＝ΣJ2/(ΣJ0+ΣJ1+ΣJ2+ΣJ3)。

According to the above-structured pure copper plate, the content of Cu is 99.96 mass% or more, the average crystal grain diameter of crystal grains in a rolled surface is X (μm), and the content of Ag is adjustedWhen the amount is Y (mass ppm), 1X 10^-8≤X^-3Y^-1≤1×10^-5This is true. Therefore, Ag is partially segregated in the grain boundaries, and the grain boundaries can be reduced, so that coarsening of the crystal grains can be suppressed. Further, the pure copper plate can ensure the conductivity and can be used as a material for a module for electronic and electrical equipment and a heat dissipation module for large current applications.

Further, a surface perpendicular to the width direction of rolling was set to 10000 μm as an observation surface²In the above measurement area, the parent phase was measured by the EBSD method in steps of 0.25 μm in measurement interval. The measurement results were analyzed by data analysis software OIM to obtain CI values for the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The average particle diameter a was determined by Area Fraction (Area Fraction). The parent phase is measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. The total area of the plurality of visual fields is 10000 μm so as to contain 1000 or more crystal grains in total²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The corresponding grain boundaries below Σ 29 are special grain boundaries, and the other grain boundaries are random grain boundaries. In the grain boundary triple points by the OIM analysis, the ratio of J3, in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries, to all the grain boundary triple points was NF_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2。

The pure copper plate according to one embodiment of the present invention satisfies 0.30 < (NF)_J2/(1-NF_J3))^0.5Not more than 0.48, so that the grain boundary network is composed of special grain boundaries with low energy, so that the driving force for recrystallization during heating is small,thereby enabling to suppress grain growth.

Here, in the pure copper plate according to one aspect of the present invention, the total content of Mg and Sn is preferably 0.1 mass ppm or more and 100 mass ppm or less.

In this case, by containing Mg and Sn, which are elements that suppress the growth of crystal grains, in total in an amount of 0.1 mass ppm or more, coarsening and non-uniformity of crystal grains can be reliably suppressed even after the heat treatment. Further, the total content of Mg and Sn is limited to 100 mass ppm or less, whereby sufficient conductivity can be ensured.

Further, in the pure copper plate according to one aspect of the present invention, the content of S is preferably in a range of 1 mass ppm or more and 20 mass ppm or less.

In this case, by containing S, which is an element that suppresses the growth of crystal grains, in total by 1 mass ppm or more, coarsening and ununiformity of crystal grains can be reliably suppressed even after the heat treatment. Further, the content of S is limited to 20 mass ppm or less, whereby sufficient hot workability can be ensured.

In the pure copper plate according to one aspect of the present invention, the total content of Pb, Se, and Te is preferably 0.3 mass ppm or more and 10 mass ppm or less.

Pb, Se, and Te contained as unavoidable impurities may be elements that segregate at grain boundaries to suppress coarsening of crystal grains. Therefore, by containing these elements in a total amount of 0.3 mass ppm or more, coarsening and ununiformity of crystal grains can be reliably suppressed even after the heat treatment. On the other hand, the presence of a large amount of these elements also has an effect of suppressing grain boundary segregation of Ag, and these elements also lower hot workability. Therefore, by setting the total content of Pb, Se, and Te to 10 mass ppm or less, the effect of suppressing the grain growth can be sufficiently exhibited without inhibiting the effect of Ag.

Further, in the pure copper plate according to one aspect of the present invention, the total content of Sr, Ba, Ti, Zr, Hf and Y is preferably 10 mass ppm or less.

There is a possibility that elements such as Sr, Ba, Ti, Zr, Hf and Y contained as unavoidable impurities segregate in grain boundaries to inhibit Ag segregation, and that compounds are formed with elements (S, Se, Te, etc.) that inhibit coarsening of crystal grains, thereby possibly inhibiting elements that inhibit coarsening of crystal grains from acting. Therefore, by limiting the total content of Sr, Ba, Ti, Zr, Hf and Y to 10 mass ppm or less, the effect of the element for suppressing the growth of crystal grains (the effect of suppressing the growth of crystal grains) can be sufficiently exhibited, and the coarsening and ununiformity of crystal grains can be reliably suppressed even after the heat treatment.

In the pure copper plate according to one aspect of the present invention, the total content of Al, Cr, P, Be, Cd, Ni, and Fe is preferably 0.3 mass ppm or more and 10 mass ppm or less.

Elements such as Al, Cr, P, Be, Cd, Ni, and Fe, which may Be contained as unavoidable impurities, have an effect of suppressing grain growth by solid solution into a copper matrix or segregation into grain boundaries, and further by formation of oxides. Therefore, by containing these elements in a total amount of 0.3 mass ppm or more, coarsening and ununiformity of crystal grains can be reliably suppressed even after the heat treatment. On the other hand, when these elements are present in a large amount, they may segregate in the grain boundary and interfere with the segregation of Ag. Therefore, by limiting the total content of Al, Cr, P, Be, Cd, Ni, and Fe to 10 mass ppm or less, the effect of the element that suppresses the growth of crystal grains (the effect of suppressing the growth of crystal grains) can Be sufficiently exhibited, and coarsening and ununiformity of crystal grains can Be reliably suppressed even after the heat treatment.

Further, in the pure copper plate according to one aspect of the present invention, it is preferable that the maximum crystal grain diameter d is within a range of 50mm × 50mm after the heat treatment at 800 ℃ for 1 hour_maxWith an average crystal grain diameter d_aveRatio d of_max/d_aveHas an average crystal grain diameter d of 20 or less_aveIs 400 μm or less.

In this case, even when heating is performed under the above-described conditions, the crystal grains can be reliably prevented from being coarsened and uneven, and the occurrence of appearance defects can be further suppressed.

In the pure copper plate according to one aspect of the present invention, the vickers hardness is preferably 150Hv or less.

In this case, the vickers hardness is 150Hv or less, and the pure copper plate is sufficiently soft to ensure the characteristics as a pure copper plate, and therefore, the material is particularly suitable as a material for electric and electronic components for large current applications.

According to one embodiment of the present invention, it is possible to provide a pure copper plate having high electrical conductivity and capable of suppressing coarsening and non-uniformity of crystal grains even after heat treatment.

Drawings

Fig. 1 is a flowchart of a method of manufacturing a pure copper plate according to the present embodiment.

Detailed Description

Hereinafter, a pure copper plate according to an embodiment of the present invention will be described.

The pure copper plate of the present embodiment is used as a material for an electric/electronic component such as a heat sink or a thick copper circuit, and is used by bonding to, for example, a ceramic substrate when the electric/electronic component is molded.

In the pure copper plate of the present embodiment, the following relational expression holds when the content of Cu is 99.96 mass% or more, the average crystal grain size of crystal grains in a rolled surface is X (μm), and the content of Ag is Y (mass ppm).

1×10^-8≤X^-3×Y^-1≤1×10^-5

In the copper alloy for electronic and electrical equipment according to the embodiment of the present invention, the surface perpendicular to the width direction of rolling is set to 10000 μm as an observation surface²In the above measurement area, the parent phase was measured by the EBSD method in steps of 0.25 μm in measurement interval. The measurement results were analyzed by data analysis software OIM to obtain CI values for the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The average particle diameter a was determined by Area Fraction (Area Fraction) using the data analysis software OIM. The parent phase is measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. In a manner to include a total of more than 1000 grains,the total area of the plurality of viewing fields is 10000 μm²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The corresponding grain boundaries below Σ 29 are special grain boundaries, and the other grain boundaries are random grain boundaries. In the grain boundary triple points by the OIM analysis, the ratio of J3, in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries, to all the grain boundary triple points was NF_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2When the temperature of the water is higher than the set temperature,

0.30＜(NF_J2/(1-NF_J3))^0.5less than or equal to 0.48.

The parent phase was measured twice by the EBSD method as described above. In the first measurement, the average particle diameter a was obtained. The step length of the measurement interval in the second measurement is determined based on the obtained average particle diameter a.

Here, in the pure copper plate of the present embodiment, the total content of Mg and Sn is preferably set in a range of 0.1 mass ppm or more and 100 mass ppm or less.

In the pure copper plate of the present embodiment, the content of S is preferably in the range of 1 mass ppm or more and 20 mass ppm or less.

Further, in the pure copper plate of the present embodiment, the total content of Pb, Se, and Te is preferably 0.3 mass ppm or more and 10 mass ppm or less.

In the pure copper plate of the present embodiment, the total content of Sr, Ba, Ti, Zr, Hf and Y (element group a) is preferably 10 mass ppm or less.

In the pure copper plate of the present embodiment, the total content of Al, Cr, P, Be, Cd, Ni, and Fe (M element group) is preferably 0.3 mass ppm or more and 10 mass or less.

The composition of the pure copper plate can also be explained as follows.

The pure copper plate contains 99.96 mass% or more of Cu and Ag, and the balance is inevitable impurities.

The pure copper plate preferably further contains one or both of Mg and Sn in a total amount of 0.1 mass ppm to 100 mass ppm.

The pure copper plate preferably further contains S in an amount of 1 to 20 mass ppm.

The pure copper plate preferably further contains at least one selected from the group consisting of Pb, Se, and Te in a total amount of 0.3 to 10 ppm by mass.

The pure copper plate preferably further contains at least one selected from the group consisting of Sr, Ba, Ti, Zr, Hf, and Y in a total amount of 10 ppm by mass or less.

The pure copper plate preferably further contains at least one selected from the group consisting of Al, Cr, P, Be, Cd, Ni, and Fe in a total amount of 0.3 ppm by mass or more and 10 ppm by mass or less.

When the elements other than Cu are contained as unavoidable impurities or intentionally contained, the preferable contents of these elements are all within the above range. Also, elements other than Cu can also be referred to as unavoidable impurities. The remaining unavoidable impurities may be elements other than the elements whose contents are particularly specified.

In the pure copper plate of the present embodiment, the maximum crystal grain diameter d in the range of 50mm × 50mm after the heat treatment at 800 ℃ for 1 hour is preferable_maxWith an average crystal grain diameter d_aveRatio d of_max/d_aveHas an average crystal grain diameter d of 20 or less_aveIs 400 μm or less.

In the pure copper plate of the present embodiment, the vickers hardness is preferably 150Hv or less.

Further, in the pure copper plate of the present embodiment, the electric conductivity is preferably 97% IACS or more.

Here, the reason why the composition, the crystal structure, and various properties are defined as described above will be described below in the pure copper plate of the present embodiment.

(purity of Cu: 99.96% by mass or more)

In an electric/electronic module for large current applications, in order to suppress heat generation during energization, it is required to have excellent electrical conductivity and heat dissipation properties, and it is preferable to use pure copper having particularly excellent electrical conductivity and heat dissipation properties. In addition, when the ceramic substrate is bonded to a ceramic substrate or the like, it is preferable that the deformation resistance is small so that thermal strain generated during a cooling-heating cycle load can be relaxed.

Here, in the pure copper plate of the present embodiment, the purity of Cu is defined to be 99.96 mass% or more.

The purity of Cu is preferably 99.965 mass% or more, and more preferably 99.97 mass% or more. The upper limit of the purity of Cu is not particularly limited, and when it exceeds 99.9999 mass%, a special refining step is required, and the production cost is greatly increased, so that it is preferably 99.9999 mass% or less.

(relation between average grain size X of crystal grains in rolled surface and Ag content Y)

Ag has a narrow solid solution limit at low temperatures and is hardly soluble in the Cu matrix. Therefore, heat treatment is performed at a high temperature to dissolve Ag in copper (a parent phase of Cu), and then warm working is performed at 150 ℃ to 350 ℃, whereby a part of Ag dissolved in the parent phase is segregated in grain boundaries. As a result, the grain boundary energy is reduced, and the coarsening of a part of the crystal grains during high-temperature heating and abnormal grain growth due to secondary recrystallization are suppressed, and the crystal grain size can be made uniform. When the average crystal grain size is sufficiently small relative to the amount of Ag added, segregation of Ag is relatively small, or a large number of non-segregated grain boundaries exist. Such grain boundaries are coarsened or abnormal grain growth occurs during high-temperature heating, and thus variation in grain size is increased.

Here, when the average crystal grain size of the crystal grains in the rolled surface is X μm and the Ag content is Y mass ppm, X is^-3Y^-1When the value of (A) is large, the content of Ag is small and the average crystal grain size is small. Therefore, the grain boundary area per unit volume becomes large, and Ag cannot be sufficiently segregated at the grain boundary. Therefore, the crystal grains are coarsened during high-temperature heating, and the variation in the particle diameter becomes large.

On the other hand, inX^-3Y^-1When the value (2) is small, the Ag content is large and the average crystal grain size is large. In this case, the effect of suppressing grain growth is high, but the amount of expensive Ag is large, and further, the heat treatment temperature is high and the treatment time is long, which significantly increases the cost.

Here, the pure copper plate of the present embodiment satisfies 1 × 10^-8≤X^-3Y^-1≤1×10^-5。

Here, X^-3Y^-1The upper limit of (B) is preferably 7.5X 10^-6Hereinafter, more preferably 5.0 × 10^-6Hereinafter, more preferably 3.0 × 10^-6Hereinafter, 2.0 × 10 is particularly preferable^-6The following. On the other hand, X^-3Y^-1The lower limit of (B) is preferably 5.0X 10^-8Above, more preferably 1.0 × 10^-7The above.

The substantial amount of Ag added is 5 to 150 mass ppm. If the content of Ag is less than 5 mass ppm, the particle size needs to be made coarser, which not only increases the cost, but also causes a problem in appearance because the particle size after heat treatment becomes relatively coarse. Therefore, the lower limit of the substantial amount of Ag to be added is 5 mass ppm or more. The lower limit is preferably 6 mass ppm or more, more preferably 7 mass ppm or more.

Addition of Ag is preferable from the viewpoint of suppressing coarsening of crystal grains, but if the addition amount of Ag is increased, not only the cost is increased, but also the conductivity is decreased. Therefore, the upper limit of the substantial amount of Ag to be added is 150 mass ppm or less. The upper limit is preferably 100 mass ppm or less, more preferably 60 mass ppm or less, further preferably 50 mass ppm or less, further preferably 40 mass ppm or less, further more preferably 30 mass ppm or less, and particularly preferably 25 mass ppm or less.

(ratio of grain boundary triple points)

The grain growth in the high-temperature heat treatment of the pure copper plate is due to the high grain boundary migration speed of random grain boundaries having high grain boundary energy. Therefore, two grain boundaries or three grain boundaries among the three grain boundaries constituting the grain boundary triple point are special grain boundaries having a small grain boundary energy represented by Σ 29 or less, and thus grain growth at high temperature can be suppressed and the crystal grain size can be made uniform.

Therefore, the surface perpendicular to the width direction of rolling was set to 10000 μm as an observation surface²In the above measurement area, the parent phase was measured by the EBSD method in steps of 0.25 μm in measurement interval. The measurement results were analyzed by data analysis software OIM to obtain CI values for the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The average particle diameter a was determined by Area Fraction (Area Fraction). The parent phase is measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. The total area of the plurality of visual fields is 10000 μm so as to contain 1000 or more crystal grains in total²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The corresponding grain boundaries below Σ 29 are special grain boundaries, and the other grain boundaries are random grain boundaries. In the grain boundary triple points by the OIM analysis, the ratio of J3, in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries, to all the grain boundary triple points was NF_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2When, stipulate (NF)_J2/(1-NF_J3))^0.5The numerical value of (c).

From the viewpoint of suppressing grain growth, (NF)_J2/(1-NF_J3))^0.5The higher the more preferred. Here, in (NF)_J2/(1-NF_J3))^0.5When the number is 0.30 or less, the number of random grain boundaries becomes relatively large with respect to the grain boundary network, and the network length becomes long. Therefore, the effect of suppressing the grain growth becomes small, and the size of the crystal grain diameter also becomes uneven. On the other hand, if (NF)_J2/(1-NF_J3))^0.5If the burr height exceeds 0.48, the burr height during press working increases. Therefore, management of burrs becomes difficult, and the cost at the time of manufacturing may increase.

In light of the above, in the present embodiment, (NF) is_J2/(1-NF_J3))^0.5Is set in a range of more than 0.30 and 0.48 or less.

In addition, (NF)_J2/(1-NF_J3))^0.5The upper limit of (b) is preferably 0.47 or less, more preferably 0.46 or less. On the other hand, (NF)_J2/(1-NF_J3))^0.5The lower limit of (b) is preferably more than 0.31, more preferably more than 0.32.

Considering the grain boundary network, random grain boundaries of J0 or J1 form a network with special grain boundaries constituting J3, and thus the number of J2 increases according to the number of J3. Namely, NF_J3Increased simultaneous NF_J2And also increases. Thus, NF_J3Preferably 0.007 or more, more preferably 0.008 or more, and further preferably 0.010 or more. And, to reduce burr height, NF_J3Preferably 0.036 or less, more preferably 0.034 or less, and still more preferably 0.030 or less.

(total content of Mg and Sn: 0.1 ppm by mass or more and 100 ppm by mass or less)

Mg and Sn are elements having an effect of suppressing coarsening of crystal grains by making a solid solution in the copper matrix phase. Therefore, in the present embodiment, when the total content of Mg and Sn is 0.1 mass ppm or more, the effect of suppressing the coarsening of crystal grains due to Mg and Sn can be exhibited, and the coarsening of crystal grains can be reliably suppressed even after the heat treatment. On the other hand, since there is a possibility that the production cost increases or the conductivity decreases due to the addition of the required amount or more, the content of any one of Mg and Sn or the total content thereof is set to less than 100 mass ppm.

The lower limit of the content of any one or the total of Mg and Sn is preferably 0.5 mass ppm or more, and more preferably 1 mass ppm or more. On the other hand, the upper limit of the total content of Mg and Sn is preferably less than 80 mass ppm, more preferably less than 60 mass ppm, and still more preferably less than 10 mass ppm.

(S content: 1 to 20 ppm by mass.)

S is an element that suppresses the coarsening of crystal grains by suppressing the movement of grain boundaries, and reduces hot workability.

Therefore, in the present embodiment, when the content of S is 1 mass ppm or more, the effect of suppressing the coarsening of crystal grains by S can be sufficiently exhibited, and the coarsening of crystal grains can be reliably suppressed even after the heat treatment. On the other hand, when the S content is limited to 20 mass ppm or less, hot workability can be ensured.

The lower limit of the S content is preferably 2 mass ppm or more, and more preferably 3 mass ppm or more. The upper limit of the S content is preferably 17.5 mass ppm or less, and more preferably 15 mass ppm or less.

(total content of Pb, Se, and Te: 0.3 to 10 mass ppm.)

Pb, Se, and Te have a low solid solution limit in Cu, and have an effect of suppressing grain coarsening by segregating at grain boundaries. On the other hand, these elements also have an effect of suppressing grain boundary segregation of Ag by being present in a large amount, and degrade hot workability.

Therefore, in the present embodiment, in order to exhibit the effect of suppressing coarsening and to ensure hot workability, the total content of Pb, Se, and Te is preferably limited to 10 mass ppm or less. If the total content of Pb, Se and Te is less than 0.3 mass ppm, the effect of the suppressing action is small, and only the cost increase due to refining is incurred. Therefore, the lower limit of the total content of Pb, Se, and Te is preferably 0.3 mass ppm or more.

In order to further improve the hot workability, the upper limit of the content of Pb, Se, and Te is preferably 9 mass ppm or less, more preferably 8 mass ppm or less, and still more preferably 7 mass ppm or less. The lower limit of the content of Pb, Se, and Te is preferably 0.4 mass ppm or more, and more preferably 0.5 mass ppm or more.

(total content of Sr, Ba, Ti, Zr, Hf and Y (element group A): 10 ppm by mass or less)

Sr, Ba, Ti, Zr, Hf and Y (a group of elements) contained as unavoidable impurities form compounds with elements (S, Se, Te, etc.) which segregate at grain boundaries to inhibit coarsening of crystal grains, and may inhibit the elements inhibiting coarsening of crystal grains from functioning.

Therefore, in order to reliably suppress coarsening of crystal grains after heat treatment, the total content of Sr, Ba, Ti, Zr, Hf, and Y (element group a) is preferably 10 mass ppm or less.

The total content of Sr, Ba, Ti, Zr, Hf and Y (element group a) is preferably 7.5 mass ppm or less, more preferably 5 mass ppm or less. The lower limit is not particularly limited, and when the total content of Sr, Ba, Ti, Zr, Hf and Y (element group a) is less than 0.01 mass ppm, the cost for refining increases, so the total content of Sr, Ba, Ti, Zr, Hf and Y (element group a) is preferably 0.01 mass ppm or more, and more preferably 0.05 mass ppm or more.

(total content of Al, Cr, P, Be, Cd, Ni and Fe (M element group): 0.3 mass ppm or more and 10 mass% or less)

Further, Al, Cr, P, Be, Cd, Ni, and Fe (M element group) have an effect of suppressing grain growth by solid solution in the copper matrix or segregation to grain boundaries, and further by formation of oxides.

Therefore, in order to reliably suppress the coarsening of crystal grains after the heat treatment, it is preferable to contain Al, Cr, P, Be, Cd, Ni, and Fe (M element group) in a total amount of 0.3 mass ppm or more. When Al, Cr, P, Be, Cd, Ni, and Fe (M element group) are intentionally contained, the lower limit of the total content of Al, Cr, P, Be, Cd, Ni, and Fe (M element group) is preferably 1.0 mass ppm or more, more preferably 1.5 mass ppm or more, further preferably 2.0 mass ppm or more, and most preferably 2.5 mass ppm or more.

On the other hand, if Al, Cr, P, Be, Cd, Ni, and Fe (M element group) are contained in an amount not less than a required amount, grain boundary segregation of Ag may Be inhibited, and the conductivity may Be lowered, so that the upper limit of the total content of Al, Cr, P, Be, Cd, Ni, and Fe (M element group) is preferably 10 mass ppm or less, more preferably less than 8 mass ppm, and still more preferably less than 5 mass ppm.

(other unavoidable impurities)

Examples of unavoidable impurities other than the above elements 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, O, and the like. These unavoidable impurities may lower the conductivity, and are therefore less preferred.

(average crystal grain diameter d after heat treatment at 800 ℃ for 1 hour_ave: less than 400 μm)

In the pure copper plate of the present embodiment, when the average particle size after the heat treatment is 400 μm or less after the retention at 800 ℃ for 1 hour, the occurrence of coarsening of crystal grains can be reliably suppressed even when the pure copper plate is heated to 800 ℃ or more, and the pure copper plate is particularly suitable as a material for a thick copper circuit or a heat sink bonded to a ceramic substrate.

The upper limit of the average particle diameter after heat treatment at 800 ℃ for 1 hour is preferably 380 μm or less, more preferably 350 μm or less.

The lower limit of the average crystal grain size after the heat treatment at 800 ℃ for 1 hour is not particularly limited, but is usually 200 μm or more.

(d after heat treatment at 800 ℃ for 1 hour_max/d_ave: below 20)

In the pure copper plate of the present embodiment, the maximum crystal grain diameter d after the heat treatment at 800 ℃ for 1 hour is within the range of 50mm × 50mm_maxWith an average crystal grain diameter d_aveRatio d of_max/d_aveWhen the temperature is 20 or less, the occurrence of non-uniformity of crystal grains can be reliably suppressed even when the temperature is heated to 800 ℃ or higher, and the material is particularly suitable as a material for a thick copper circuit or a heat sink bonded to a ceramic substrate.

Further, the maximum crystal grain diameter d in the range of 50mm X50 mm after heat treatment at 800 ℃ for 1 hour_maxWith an average crystal grain diameter d_aveRatio d of_max/d_avePreferably 18 or less, more preferably 16 or less.

(Vickers hardness: 150Hv or less)

In the pure copper plate of the present embodiment, the vickers hardness is set to 150Hv or less, thereby ensuring the properties as a pure copper plate, which is particularly suitable as a material for electric and electronic components for large current applications. The pure copper plate of the present embodiment is sufficiently soft, and can release thermal strain caused by deformation of the pure copper plate even when the pure copper plate is bonded to another component such as a ceramic substrate and a cooling-heating cycle is applied.

The vickers hardness is preferably 140Hv or less, more preferably 120Hv or less, still more preferably 100Hv or less, and still more preferably 95Hv or less.

The lower limit of the Vickers hardness is not particularly limited, but is preferably 60Hv or more.

(conductivity: 97% IACS or more)

In the pure copper plate of the present embodiment, the conductivity is set to 97% IACS or more, thereby ensuring the characteristics as a pure copper plate, and the pure copper plate is particularly suitable as a material for a package for electronic and electrical equipment and a heat dissipation package for large current applications.

The conductivity is preferably 98% IACS or more, more preferably 99% IACS or more, and further preferably 100% IACS or more.

The upper limit of the conductivity is not particularly limited, but is usually 103% IACS or less.

Next, a method for manufacturing the pure copper plate of the present embodiment configured as described above will be described with reference to a flowchart shown in fig. 1.

(melting and casting step S01)

First, the above-described elements are added to a copper melt obtained by melting a copper raw material to adjust the composition, thereby producing a copper alloy melt. For addition of various elements, simple elements, mother alloys, and the like can be used. Further, the raw material containing the above-mentioned elements may be melted together with the copper raw material. Furthermore, the alloy recycled material and scrap of the present embodiment may also be used. Here, the molten copper is preferably 4NCu having a purity of 99.99 mass% or more, or 5NCu having a purity of 99.999 mass% or more. In the melting step, it is preferable to use H for suppressing the oxidation of the additive element and for reducing the hydrogen concentration₂Inert gas atmosphere having low vapor pressure of O (e.g., Ar gas or N)₂Gas) such gasMelting is performed under an atmosphere, and the holding time at the time of melting is limited to a minimum.

Then, the copper alloy melt adjusted in composition is poured into a mold to form an ingot. In addition, when mass production is considered, it is preferable to use a continuous casting method or a semi-continuous casting method.

The cooling rate of the melt is preferably 0.1 ℃/sec or more, more preferably 0.5 ℃/sec or more.

(Hot working Process S02)

Then, thermal processing is performed to homogenize the structure. The hot working temperature is not particularly limited, but is preferably in the range of 500 ℃ to 1000 ℃.

The total reduction ratio in hot working is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more.

Further, the cooling method after hot working is not particularly limited, but air cooling or water cooling is preferable.

The processing method in the hot working step S02 is not particularly limited, and rolling, extrusion, groove rolling, forging, pressing, or the like can be used, for example.

(crude processing step S03)

Next, rough machining is performed to machine the workpiece into a predetermined shape. In addition, in the rough processing step S03, warm processing is performed at 150 ℃ to 350 ℃. By performing warm working at 150 ℃ to 350 ℃, Ag can be segregated in the vicinity of the grain boundaries, and the grain boundary energy can be reduced. In this step, warm working and cold working may be combined. In this case, warm working may be performed for a plurality of passes before final working. For example, if rolling is used, warm working may be performed three or more times last.

(recrystallization Heat treatment Process S04)

Next, the copper material after the rough machining step S03 is subjected to a heat treatment for the purpose of recrystallization. Here, the grain size of the recrystallized grains is preferably 10 μm or more. When the recrystallized grains are fine, the growth of the grains and the nonuniformity of the structure may be promoted when the temperature is increased to 800 ℃ or higher after recrystallization. The crystal grain size after recrystallization is preferably 15 μm or more, more preferably 20 μm or more, and still more preferably 25 μm or more.

The heat treatment conditions in the recrystallization heat treatment step S04 are not particularly limited, but the heat treatment temperature is preferably 200 ℃ to 900 ℃ and the holding time is preferably 1 second to 10 hours.

In order to obtain a desired shape, the rough processing step S03 and the recrystallization heat treatment step S04 may be repeated twice or more.

(thermal refining step S05)

Next, in order to adjust the material strength, the copper material after the recrystallization heat treatment step S04 may be subjected to thermal refining. The working ratio of the thermal refining is not particularly limited, but is preferably in the range of more than 0% and 50% or less in order to adjust the material strength. The working ratio is more preferably limited to 3% or more and 40% or less.

Further, in order to remove the residual strain as necessary, heat treatment may be further performed after the thermal refining.

Through the above steps, the pure copper plate of the present embodiment is produced.

According to the pure copper plate of the present embodiment configured as described above, when the average crystal grain size of the crystal grains in the rolled surface is X (μm) and the Ag content is Y (mass ppm), the requirement is satisfied

1×10^-8≤X^-3Y^-1≤1×10^-5。

Therefore, since a part of Ag segregates in the grain boundary and the grain boundary energy is reduced, coarsening of the crystal grains can be suppressed.

The surface perpendicular to the width direction of rolling was set to 10000 μm as an observation surface²In the above measurement area, the parent phase was measured by the EBSD method in steps of 0.25 μm in measurement interval. The measurement results were analyzed by data analysis software OIM to obtain CI values for the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. Performing orientation difference analysis of each crystal grain by data analysis software OIM, and making the orientation difference between adjacent measurement points be 15 ° or moreThe boundaries are grain boundaries. The average particle diameter a was determined by Area Fraction (Area Fraction). The parent phase is measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. So as to contain more than 1000 crystal grains in total, and the total area of multiple visual fields is 10000 μm²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. Measurement points with CI values of 0.1 or less were excluded. The misorientation analysis of each crystal grain was performed by the data analysis software OIM, and the boundary between the measurement points where the misorientation between the adjacent measurement points was 15 ° or more was defined as the grain boundary. The corresponding grain boundaries below Σ 29 are special grain boundaries, and the other grain boundaries are random grain boundaries. In the grain boundary triple points by the OIM analysis, the ratio of J3, in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries, to all the grain boundary triple points was NF_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2When the amount is more than or equal to 0.30 (NF)_J2/(1-NF_J3))^0.5Less than or equal to 0.48. Therefore, the grain boundary network is composed of special grain boundaries having low energy, and the driving force for recrystallization during heating is small, thereby suppressing grain growth. Further, the burr height can be suppressed during press working.

In the present embodiment, even when the content of Mg and Sn, which are elements that suppress the growth of crystal grains, is 0.1 mass ppm or more, coarsening and ununiformity of crystal grains can be reliably suppressed after the heat treatment. When the total content of Mg and Sn is limited to 100 mass ppm or less, sufficient conductivity can be ensured.

In the present embodiment, when the content of S is in the range of 1 mass ppm to 20 mass ppm, S, which is one of the elements that suppress the growth of crystal grains, is segregated in the grain boundary, and thus coarsening and ununiformity of crystal grains during heating can be reliably suppressed. Further, hot workability can be ensured.

Further, in the present embodiment, when the total content of Pb, Se, and Te as elements segregated at the grain boundary to suppress coarsening of crystal grains is set to 0.3 mass ppm or more, coarsening and ununiformity of crystal grains can be reliably suppressed even after the heat treatment. Further, when the total content of Pb, Se, and Te is 10 ppm by mass or less, the effect of suppressing the grain growth can be sufficiently exhibited without inhibiting the effect of Ag.

In the present embodiment, when the total content of Sr, Ba, Ti, Zr, Hf and Y (a element group) is 10 mass ppm or less, the elements of the a element group do not inhibit the effect of Ag as an element for suppressing grain growth, and further, the elements of the a element group can be suppressed from reacting with S, Se, Te, and the like to form compounds. Therefore, the function of the element for suppressing the grain growth can be sufficiently exhibited. Therefore, coarsening and unevenness of crystal grains during heating can be reliably suppressed.

Further, in the present embodiment, when the total content of Al, Cr, P, Be, Cd, Ni, and Fe (M element group) is 0.3 mass ppm or more, coarsening and unhomogenization of crystal grains after heat treatment can Be reliably suppressed even by solid solution into the copper matrix, segregation into grain boundaries, and formation of oxides. Further, when the total content of Al, Cr, P, Be, Cd, Ni, and Fe is limited to 10 mass ppm or less, the effect of suppressing the growth of crystal grains can Be sufficiently exhibited without suppressing the effect of Ag, and coarsening and ununiformization of crystal grains during heating can Be reliably suppressed.

In the present embodiment, the maximum crystal grain diameter d is within the range of 50mm × 50mm after the heat treatment at 800 ℃ for 1 hour_maxWith an average crystal grain diameter d_aveRatio d of_max/d_aveHas an average crystal grain diameter d of 20 or less_aveWhen the particle size is 400 μm or less, the crystal grains can be reliably suppressed from being coarsened and uneven even after the heat treatment, and the occurrence of appearance defects can be further suppressed.

In the present embodiment, the pure copper plate is soft enough to ensure the properties as a pure copper plate when the vickers hardness is 150Hv or less, and is therefore particularly suitable as a material for an electric/electronic component for large current applications.

The pure copper plate according to the embodiment of the present invention has been described above, but the present invention is not limited to this, and can be modified as appropriate within a range not departing from the technical requirements of the present invention.

For example, although the above embodiment describes an example of the method for producing a pure copper plate, the method for producing a pure copper plate is not limited to the method described in the embodiment, and a conventional production method may be appropriately selected for production.

Regarding the average crystal grain size X of the crystal grains in the rolled surface, the maximum crystal grain size d after heat treatment at 800 ℃ for 1 hour_maxWith an average crystal grain diameter d_aveThe measurement was performed by the method described in the examples described below.

Examples

The results of the confirmation experiment performed to confirm the effects of the present invention will be described below.

A copper raw material composed of pure copper having a purity of 99.999 mass% or more is prepared, and the raw material is charged into a high-purity graphite crucible, and melted by high-frequency induction heating in an atmosphere furnace having an Ar gas atmosphere.

To the obtained copper melt, each element was added, and the melt was cast into a carbon mold, thereby producing ingots having the composition shown in tables 1 and 3. Then, a part of the ingot was cut to obtain an ingot having a thickness of 50mm, a width of 100mm and a length of 100 mm.

Then, the mixture was heated at 800 ℃ for 4 hours in an Ar gas atmosphere using an electric furnace, and homogenized.

The ingot after the homogenization heat treatment was hot forged by free forging so that the forging ratio became 4 or more, and a plate material having a height of about 25mm × a width of about 150mm was obtained. In the hot forging, the surface temperature is 500 ℃ or higher, and the hot forging is performed again at a time point when the surface temperature reaches about 600 ℃ after reheating in an electric furnace maintained at 800 ℃. The temperature at the end of hot forging is 500 ℃ or higher. After completion of the hot forging, the resultant was subjected to a solution heat treatment for 1min in an electric furnace heated to 800 ℃.

The forged plate was subjected to surface grinding to remove the oxide film on the surface.

Then, the rolling rolls were heated to 300 ℃ and rough rolled (warm rolled) at a rolling rate shown in the table. The hot-rolled copper plate was subjected to recrystallization heat treatment in an electric furnace at heat treatment temperatures shown in tables 2 and 4, so that the crystal grain size was adjusted to 10 μm to 150 μm.

Then, temper rolling was performed on the copper material after the recrystallization heat treatment under the conditions shown in tables 2 and 4, and a strip for property evaluation (test piece for property evaluation) having a width of 60mm was produced at the thickness shown in tables 2 and 4.

The following items were evaluated.

(composition analysis)

The obtained ingot was sampled and measured for the content of each element by a glow discharge mass spectrometer (GD-MS). In addition, the measurement was performed at 2 points of the center and the width direction end of the sample, and the one with the larger content was defined as the content of each sample. The measurement results are shown in tables 1 and 3.

(ratio of grain boundary triple points)

The grain boundaries (special grain boundaries and random grain boundaries) and the triple point of the grain boundaries were measured as follows using a TD plane (Transverse direction) as an observation plane, which is a cross section perpendicular to the width direction of rolling, by an EBSD measuring apparatus and OIM analysis software. Mechanical grinding was performed using water-resistant sandpaper, diamond abrasive grains. Subsequently, fine grinding was performed using a silica gel solution. Furthermore, the particle size of the particles was measured at 10000 μm using an EBSD measuring apparatus (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX/TSL, Inc. (currently available AMETEK), Inc.) and Analysis software (OIM Data Analysis ver.7.3.1 manufactured by EDAX/TSL, Inc. (currently available AMETEK), Inc.)²In the measurement area above, the acceleration voltage of the electron beam in the matrix phase was measured by the EBSD method at 20kV and at measurement intervals of 0.25. mu.m. Analysis of the measurements by the data analysis software OIM gave CI values for each measurement point. The difference in orientation of each crystal grain was analyzed by the data analysis software OIM, excluding the measurement points having CI values of 0.1 or less. The boundary between measurement points at which the orientation difference between adjacent measurement points is 15 ° or more is defined as a grain boundary. By area fraction(Area Fraction) the average particle diameter A was determined. The parent phase was measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. The total area of the plurality of visual fields is 10000 μm so as to contain 1000 or more crystal grains in total²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. The difference in orientation of each crystal grain was analyzed by the data analysis software OIM, excluding the measurement points having CI values of 0.1 or less. The boundary between measurement points at which the orientation difference between adjacent measurement points is 15 ° or more is defined as a grain boundary. Then, for each of the three grain boundaries constituting the grain boundary triple point, a special grain boundary and a random grain boundary are identified using the value of the coincidence position lattice Σ (CSL sigma value) calculated at the adjacent grid point (Neighboring grid point). Corresponding grain boundaries exceeding Σ 29 are regarded as random grain boundaries.

(Press workability)

Punching a plurality of round holes from a web for characteristic evaluation using a die

The burr height was measured, and the press workability was evaluated.

The die gap was set to about 3% of the plate thickness, and punching was performed at a punching speed of 50spm (stroke per minute). The notch surface on the punching side was observed, the burr height at ten or more positions was measured, and the ratio of the burr height to the plate thickness was determined.

The maximum value of the burr height was evaluated as "a" (good) when the sheet thickness was 3.0% or less. The case where the maximum value of the burr height exceeded 3.0% with respect to the sheet thickness was evaluated as "B" (defective). The evaluation results are shown in tables 5 and 6.

(Vickers hardness)

The Vickers hardness was measured under a test load of 0.98N in accordance with the microscopic Vickers hardness test method defined in JIS Z2244. The measurement position is the rolled surface of the test piece for characteristic evaluation. The evaluation results are shown in tables 5 and 6.

(conductivity)

A test piece having a width of 10 mm. times.a length of 60mm was sampled from a strip for characteristic evaluation, and the resistance was determined by a four-terminal method. Then, the size of the test piece was measured using a micrometer, and the volume of the test piece was calculated. Then, the conductivity was calculated from the measured resistance value and the volume. The evaluation results are shown in tables 5 and 6.

The test piece was sampled so that the longitudinal direction thereof was parallel to the rolling direction of the property evaluation strip.

(grain size before Heat treatment)

A20 mm × 20mm sample was cut out from the obtained bar for characteristic evaluation, and the average crystal grain size was measured by an SEM-EBSD (Electron Back Diffraction Patterns) measuring apparatus.

The rolled surface was mechanically polished with water-resistant polishing paper and diamond abrasive grains. Subsequently, fine grinding was performed using a silica gel solution. Thereafter, the measurement was carried out at 10000 μm using an EBSD measuring apparatus (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX/TSL, Inc. (currently available from AMETEK), Inc.) and Analysis software (OIM Data Analysis ver.7.3.1 manufactured by EDAX/TSL, Inc. (currently available from AMETEK), Inc.)²In the measurement area above, the acceleration voltage of the electron beam in the matrix phase was measured by the EBSD method at 20kV and at measurement intervals of 0.25. mu.m. Analysis of the measurements by the data analysis software OIM gave CI values for each measurement point. The difference in orientation of each crystal grain was analyzed by the data analysis software OIM, excluding the measurement points having CI values of 0.1 or less. The boundary between measurement points at which the orientation difference between adjacent measurement points is 15 ° or more is defined as a grain boundary. The average particle diameter a was determined by Area Fraction (Area Fraction). The parent phase was measured by the EBSD method in a step size of one tenth or less of the average particle diameter a at measurement intervals. The total area of the plurality of visual fields is 10000 μm so as to contain 1000 or more crystal grains in total²The measurement results of the above measurement areas were analyzed by OIM software to obtain CI values at the respective measurement points. The difference in orientation of each crystal grain was analyzed by the data analysis software OIM, excluding the measurement points having CI values of 0.1 or less. Between measurement points where the orientation difference between adjacent measurement points is 15 ° or moreThe boundaries were large angle grain boundaries, and those with a difference in orientation between adjacent measurement points of less than 15 ° were small angle grain boundaries. A grain boundary map was prepared using large-angle grain boundaries, and five line segments of a predetermined length were drawn at predetermined intervals in the longitudinal and lateral directions of the grain boundary map in accordance with the cutting method of JIS H0501. The number of completely cut crystal grains was counted, and the average value of the cut lengths was calculated as the average crystal grain size before heat treatment. The evaluation results are shown in tables 5 and 6.

The average crystal grain size before heat treatment was also X μm, which is the average crystal grain size of crystal grains in the rolled surface. X is calculated when the average grain size of the crystal grains in the rolled surface is X [ mu ] m and the Ag content is Y mass ppm^-3Y^-1The values of (b) are shown in tables 5 and 6. In addition, the calculated value is "a × 10^-b"in Table 5 and Table 6," aE-b "is shown. For example, "1.2E-08" means "1.2X 10^-8”。

(grain size after Heat treatment)

A60 mm × 60mm sample was cut out from the above-mentioned strip for characteristic evaluation, and heat treatment was performed at 800 ℃ for 1 hour. A sample of 50 mm. times.50 mm was cut out from the test piece, and the rolled surface was mirror-polished and etched. Then, the image was taken by an optical microscope so that the rolling direction was a horizontal direction of the photograph. Selecting the most fine grain size in the observation region of about 1mm²The part formed with uniform particle size in the above field of view is about 1mm²The above field of view was observed and measured. Then, five line segments of a predetermined length are drawn at predetermined intervals in the longitudinal and lateral directions of the photograph in accordance with the cutting method of JIS H0501. The number of completely cut crystal grains was counted, and the average value of the cut lengths was calculated as the average crystal grain diameter d after the heat treatment_ave. The evaluation results are shown in tables 5 and 6.

(deviation of particle size after Heat treatment)

As described above, regarding the sample sampled from the test piece subjected to the heat treatment, the twins were excluded in the range of 50mm × 50mm, and the average value of the major diameter and the minor diameter of the coarsest crystal grains was defined as the maximum crystal grain diameter d_max. Has a major diameter ofThe longest line segment among line segments connecting two points on the grain boundary (outline of the crystal grain), and the short diameter is the length of the longest line segment among line segments cut by the grain boundary when drawing a line perpendicular to the long diameter. The maximum crystal grain diameter is set to the above-mentioned average crystal grain diameter d_aveRatio of d_max/d_aveThe case of 20 or less was evaluated as "A" (good), and d was_max/d_aveIf it exceeds 20, the evaluation is "B" (defective). The evaluation results are shown in tables 5 and 6.

[ Table 1]

Element group A: one or more selected from Sr, Ba, Ti, Zr, Hf and Y

M element group: one or more than two of Al, Cr, P, Be, Cd, Ni and Fe

[ Table 2]

[ Table 3]

Element group A: one or more selected from Sr, Ba, Ti, Zr, Hf and Y

M element group: one or more than two of Al, Cr, P, Be, Cd, Ni and Fe

[ Table 4]

[ Table 5]

X: average crystal grain diameter (μm) of crystal grains in a rolled surface, Y: ag content (ppm by mass)

[ Table 6]

In comparative example 1, X^-3Y^-1The range of the particle size after the heat treatment is larger than that of the present embodiment, the variation of the particle size after the heat treatment is "B" (defective), and the particle size after the heat treatment is more than 400 μm.

In comparative example 2, (NF)_J2/(1-NF_J3))^0.5The range of the particle size distribution after the heat treatment is smaller than that of the present embodiment, the variation of the particle size after the heat treatment is "B" (defective), and the particle size after the heat treatment is more than 400 μm.

In comparative example 3, (NF)_J2/(1-NF_J3))^0.5The press workability was "B" (defective) over a wider range than in the present embodiment. Therefore, the crystal grain size after the heat treatment was not evaluated.

In comparative example 4, X^-3Y^-1Smaller than the range of the present embodiment, the crystal grain size before the heat treatment exceeds 400. mu.m. Therefore, no other evaluation was performed.

In contrast, in the present invention example, the average crystal grain size after the heat treatment was small, and the variation in grain size was small. The conductivity is also 97% IACS or higher.

As described above, according to the present invention, it is confirmed that a pure copper plate having excellent conductivity and capable of suppressing coarsening and non-uniformity of crystal grains even after heat treatment can be provided.

Industrial applicability

The pure copper plate of the present embodiment can be suitably used for an electric and electronic component such as an insulating circuit board having a copper plate material as a heat sink or a thick copper circuit.

Claims

1. A pure copper sheet characterized in that the Cu content is 99.96 mass% or more, the following relational expression holds when the average crystal grain size of crystal grains in a rolled surface is X [ mu ] m and the Ag content is Y mass ppm,

1×10^-8≤X^-3Y^-1≤1×10^-5

the surface perpendicular to the width direction of rolling was set to 10000 μm as an observation surface²Measuring the parent phase at a measurement interval of 0.25 μm in the measurement area by EBSD, obtaining CI values at the measurement points by OIM analysis of the measurement result by data analysis software, excluding the measurement points having CI values of 0.1 or less, performing misorientation analysis of the crystal grains, determining the average grain diameter A by area fraction using the boundary between the measurement points at which the misorientation between adjacent measurement points is 15 ° or more as the grain boundary, measuring the parent phase at a measurement interval of one tenth or less of the average grain diameter A by EBSD, and allowing the parent phase to have a plurality of fields of view of 10000 μm or more so as to include 1000 or more crystal grains in total and have a plurality of fields of view of 10000 μm or less²The above measurement area is obtained by subjecting the measurement results to OIM analysis by data analysis software to obtain CI values at the respective measurement points, and orientation difference analysis of the respective crystal grains is performed while excluding the measurement points having CI values of 0.1 or less, and when the boundary between the measurement points where the orientation difference between adjacent measurement points is 15 ° or more is defined as a grain boundary, the corresponding grain boundary of Σ 29 or less is defined as a special grain boundary, and the other grain boundaries are defined as random grain boundaries, among the grain boundary triple points according to the OIM analysis,

the proportion of J3 in which all three grain boundaries constituting the grain boundary triple points are special grain boundaries to all the grain boundary triple points was NF_J3The ratio of J2 in which two grain boundaries constituting grain boundary triple points are special grain boundaries and one grain boundary is random grain boundaries to all the grain boundary triple points is NF_J2When the temperature of the water is higher than the set temperature,

0.30＜(NF_J2/(1-NF_J3))^0.5less than or equal to 0.48.

2. The pure copper plate according to claim 1,

the total content of Mg and Sn is in the range of 0.1 mass ppm to 100 mass ppm.

3. The pure copper plate according to claim 1 or 2,

the content of S is in the range of 1-20 mass ppm.

4. The pure copper plate according to any one of claims 1 to 3,

the total content of Pb, Se and Te is in the range of 0.3-10 mass ppm.

5. The pure copper plate according to any one of claims 1 to 4,

the total content of Sr, Ba, Ti, Zr, Hf and Y is 10 mass ppm or less.

6. The pure copper plate according to any one of claims 1 to 5,

the total content of Al, Cr, P, Be, Cd, Ni and Fe is in the range of 0.3-10 mass ppm.

7. The pure copper plate according to any one of claims 1 to 6,

maximum crystal grain diameter d in the range of 50mm x 50mm after heat treatment at 800 ℃ for 1 hour_maxWith an average crystal grain diameter d_aveRatio d of_max/d_aveHas an average crystal grain diameter d of 20 or less_aveIs 400 μm or less.

8. The pure copper plate according to any one of claims 1 to 7,

the Vickers hardness is 150Hv or less.