WO2020122230A1

WO2020122230A1 - Pure copper sheet, member for electronic/electric device, and member for heat dissipation

Info

Publication number: WO2020122230A1
Application number: PCT/JP2019/048948
Authority: WO
Inventors: 優樹伊藤; 広行森; 浩之松川
Original assignee: 三菱マテリアル株式会社
Priority date: 2018-12-13
Filing date: 2019-12-13
Publication date: 2020-06-18
Also published as: JP2020094241A

Abstract

This pure copper sheet is characterized in that the purity of Cu exclusive of S is 99.96 mass% or more, the balance being unavoidable impurities, and that S is included in the range of 20-1000 mass ppm. It is preferred that the total content of Pb and Bi is not more than 20 mass ppm. It is preferred that the content of P is not more than 5 mass ppm.

Description

Pure copper plate, electronic and electrical equipment parts, heat dissipation parts

The present invention is a pure copper plate suitable for a member for electronic/electrical devices such as a heat sink, a thick copper circuit, a bus bar, and the like, and particularly a pure copper plate excellent in punching workability, a member for electronic/electrical devices comprising the pure copper plate, and The present invention relates to a heat dissipation member.
The present application claims priority based on Japanese Patent Application No. 2018-233346 filed in Japan on December 13, 2018, the contents of which are incorporated herein by reference.

2. Description of the Related Art Conventionally, copper or copper alloys having high electrical conductivity and thermal conductivity have been used for members for electronic/electrical devices such as thick copper circuits and bus bars, and for heat dissipation members such as heat sinks.
Due to the decrease in current density and the diffusion of heat due to Joule heat generation accompanying the increase in current of electronic devices and electric devices, the electronic/electric device members and heat dissipation members used in these electronic devices and electric devices are It is being made larger and thicker. For this reason, high electrical conductivity and thermal conductivity and good punching workability at the time of press working are required for materials constituting the members for electronic/electrical devices and the members for heat dissipation.

For example, Patent Documents 1-3 propose a copper material with improved punching workability.
Patent Document 1 discloses a technique of improving stamping workability by adding S, Se, Te, Sb, Bi or the like to a Cu—Ni—Si alloy.
Patent Document 2 discloses a technique for improving press punchability by defining crystal texture orientation in a Cu—Fe—P alloy.
Patent Document 3 discloses a technique for improving punching workability by dispersing Cr or a Cr compound in a Cu—Cr—Sn—Zn alloy.

Japanese Patent Laid-Open No. 11-256256 JP 2000-328158 A JP 2001-181757 A

By the way, in Patent Documents 1-3, all of them are intended to improve punching workability for various copper alloys.
Since it is required to have excellent electrical conductivity and thermal conductivity in members for electronic/electrical equipment and heat radiation members for large current applications, it is particularly excellent in electrical conductivity and thermal conductivity, not the above-mentioned copper alloy. A thick plate material made of pure copper may be used.
When the material strength of the thick plate material is high, the springback amount becomes large at the time of forming, it becomes impossible to secure high dimensional accuracy, and the equipment load may become high at the time of bending. Therefore, it is preferable to use a pure copper plate having a relatively low material strength as the thick plate material.

However, in the case of pure copper plate, it is known that the punching workability is particularly poor, and by thickening the pure copper plate, this problem becomes more noticeable. Therefore, when a pure copper plate is punched, problems such as a decrease in dimensional accuracy, generation of punching scraps, and die wear occur, and the members for electronic/electrical equipment and the heat radiation member made of a pure copper plate are accurately manufactured. In addition, it was difficult to manufacture efficiently.

The present invention has been made in view of the above-mentioned circumstances, and is a pure copper plate excellent in punching workability, capable of performing punching with high precision and efficiency, and an electronic/electrical device made of this pure copper plate. An object is to provide a device member and a heat dissipation member.

In order to solve this problem, as a result of diligent studies by the present inventors, by adding an appropriate amount of S to a pure copper plate to disperse a Cu—S-based compound, the characteristics such as conductivity, thermal conductivity, and strength can be improved. We have obtained the knowledge that punching workability can be improved while ensuring the same. Further, S is known to cause hot work cracking of a pure copper plate, but it has been found that the occurrence of hot work cracks can be suppressed by optimizing the S content. It was

The present invention has been made based on the above findings, and the pure copper plate according to one aspect of the present invention has a purity of Cu excluding S of 99.96 mass% or more, and the balance being inevitable impurities. , S in the range of 20 mass ppm or more and 1000 mass ppm or less.

According to the pure copper plate of this structure, since S is contained in the range of 20 mass ppm or more and 1000 mass ppm or less, it is possible to disperse the Cu—S based compound, and at the time of punching, the Cu—S based compound becomes the starting point and fracture occurs Therefore, the punching workability can be improved. Further, by setting the S content within the above range, the occurrence of hot work cracking can be suppressed.
Furthermore, since the purity of Cu excluding S is 99.96 mass% or more, and the balance is unavoidable impurities, the purity of copper is sufficiently high and it is possible to secure the properties such as conductivity and strength as a pure copper plate. Therefore, it is suitable as a material for electronic and electrical equipment members and heat dissipation members for large current applications.

In the pure copper plate which is one aspect of the present invention, the total content of Pb and Bi is preferably 20 massppm or less.
Pb and Bi, which may be contained as unavoidable impurities, are likely to segregate at the grain boundaries and have a low melting point, thus deteriorating hot workability. Therefore, by limiting the total content of Pb and Bi contained as unavoidable impurities to 20 mass ppm or less, the occurrence of hot work cracking can be further suppressed.

In the pure copper plate which is one embodiment of the present invention, the P content is preferably 5 massppm or less.
It was found that P, which may be contained as an unavoidable impurity, has an effect of affecting the distribution state of the Cu—S compound. Therefore, by limiting the content of P contained as an unavoidable impurity to 5 mass ppm or less, the Cu-S compound can be sufficiently dispersed, and the punching workability can be further improved.

In the pure copper plate which is one embodiment of the present invention, it is preferable that the fracture surface ratio in the punched cross section is 20% or more.
In this case, since the fracture surface ratio is 20% or more in the cross section after punching, the shear surface ratio is sufficiently low, burrs can be suppressed during punching, and dimensional accuracy is improved. It becomes possible. Further, it is possible to suppress wear of the mold and generation of punching scraps, and it is possible to efficiently perform punching.

In the pure copper plate which is one aspect of the present invention, the tensile strength is preferably 500 MPa or less.
In this case, since the tensile strength is 500 MPa or less and the characteristics as a pure copper plate are ensured, it is particularly suitable as a material for a member for electronic/electrical equipment and a member for heat dissipation for large current applications.

In the pure copper plate which is one aspect of the present invention, the electrical conductivity is preferably 90% IACS or more.
In this case, since the electrical conductivity is 90% IACS or more and the characteristics as a pure copper plate are secured, it is particularly suitable as a material for a member for electronic/electric equipment and a member for heat dissipation for large current applications.

The member for electronic/electrical equipment which is one aspect of the present invention is characterized by being made of the above-mentioned pure copper plate.
According to the electronic/electrical device member having this structure, since it is composed of the above-mentioned pure copper plate, the shape accuracy is good and the conductivity is excellent. Therefore, it can be preferably used even in a large current application.

The heat dissipation member according to one aspect of the present invention is characterized by being made of the above-mentioned pure copper plate.
According to the heat dissipation member having this structure, since it is composed of the above-mentioned pure copper plate, the shape accuracy is good and the heat conductivity is excellent. Therefore, it is possible to efficiently dissipate heat even in an application that generates a large amount of heat.

According to the present invention, there is provided a pure copper plate having excellent punching workability, capable of performing punching with high accuracy and efficiency, a member for electronic/electrical equipment and a member for heat dissipation made of this pure copper plate. You can

It is a binary state diagram of Cu-S. It is a schematic explanatory drawing when calculating the fracture surface ratio in the cross section at the time of stamping. It is a flowchart of the manufacturing method of the pure copper plate which is this embodiment.

Below, the pure copper plate which is one embodiment of the present invention is explained.
The pure copper plate of the present embodiment is used as a material for electronic/electrical equipment members such as thick copper circuits, bus bars, and heat dissipation members such as heat sinks, and the aforementioned electronic/electrical equipment members and heat dissipation members are used. A punching process is performed at the time of molding.

The pure copper plate of the present embodiment has a purity of Cu excluding S of 99.96 mass% or more, the balance being inevitable impurities, and containing S in the range of 20 mass ppm to 1000 mass ppm. That is, the pure copper plate according to the present embodiment contains S in the range of 20 massppm or more and 1000 massppm or less with respect to pure copper having a purity of Cu excluding S of 99.96 mass% or more.

In the pure copper plate of this embodiment, it is preferable that the total content of Pb and Bi that are inevitable impurities is 20 mass ppm or less.
In the pure copper plate of this embodiment, the content of P, which is an unavoidable impurity, is preferably 5 massppm or less.

In the pure copper plate of this embodiment, it is preferable that the fracture surface ratio in the punched cross section when the punching test is performed is 20% or more.
In the pure copper plate of this embodiment, the tensile strength is preferably 500 MPa or less.
In the pure copper plate of this embodiment, it is preferable that the electrical conductivity is 90% IACS or more.

The reasons for defining the component composition and various characteristics as described above in the pure copper plate of this embodiment will be described below.

(Cu purity: 99.96 mass% or more)
It is required that electronic and electric equipment members and heat dissipation members for large current applications have excellent electrical conductivity and thermal conductivity in order to suppress heat generation during energization. It is preferable to use pure copper which is particularly excellent in
In the pure copper plate of this embodiment, the purity of Cu excluding S is specified to be 99.96 mass% or more.
The purity of Cu excluding S is preferably 99.965 mass% or more, and more preferably 99.97 mass% or more. The upper limit of the purity of Cu except S is not particularly limited, but if it exceeds 99.999 mass%, a special refining step is required, and the manufacturing cost increases significantly, so 99.999 mass% or less is required. Is preferred.

(S content: 20 massppm or more and 1000 massppm or less)
As shown in the state diagram of FIG. 1, S has a low solid solubility limit in Cu and therefore hardly reduces the conductivity. On the other hand, the segregation of S at the grain boundaries reduces the hot workability.
Then, by containing S, Cu reacts with S to produce a Cu—S-based compound such as Cu ₂ S. When the Cu-S compound is dispersed, the above-mentioned Cu-S compound becomes a starting point of fracture when punching is performed, and the punching workability is improved.

If the S content is less than 20 mass ppm, the Cu—S-based compound is not sufficiently generated, and the punching workability may not be improved. On the other hand, if the S content exceeds 1000 mass ppm, the hot workability may be significantly reduced.
From the above, in the present embodiment, the S content is set within the range of 20 mass ppm or more and 1000 mass ppm or less.
In order to further improve the punching workability, the lower limit of the S content is preferably 25 mass ppm or more, and more preferably 30 mass ppm or more. On the other hand, in order to further suppress the deterioration of hot workability, the upper limit of the S content is preferably 900 massppm or less, and more preferably 800 massppm or less.

(Pb and Bi total content: 20 massppm or less)
Since Pb and Bi contained as unavoidable impurities have a low solid solubility limit in Cu and a low melting point, they segregate at the grain boundaries to reduce hot workability.
Therefore, when further improving the hot workability, it is preferable to limit the total content of Pb and Bi, which are inevitable impurities, to 20 mass ppm or less.
When further improving the hot workability, the total content of Pb and Bi is preferably 15 massppm or less, more preferably 10 massppm or less.

(P content: 5 massppm or less)
It was found that P contained as an unavoidable impurity affects the dispersion state of the Cu-S compound. Specifically, P is preferentially present at nucleation sites (eg, grain boundaries, dislocations and strains in the grains) generated by the Cu—S compound, which may hinder the dispersion of the Cu—S compound. There is.
Therefore, when the Cu—S-based compound is further uniformly dispersed to stably improve the punching workability, it is preferable to limit the content of P, which is an unavoidable impurity, to 5 mass ppm or less.
In order to further improve the punching workability, the P content is preferably 4 massppm or less, more preferably 3 massppm or less.

(Other inevitable impurities)
Other unavoidable impurities other than Pb, Bi, P are Ag, B, Ca, Mg, Sr, Ba, Sc, Y, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Se, Te, Rh, Ir, Ni, Pd, Pt, Au, Zn, Cd, Hg, Al, Ga, In, Ge, Sn, As, Sb, Examples include Tl, Be, N, C, Si, Li, H, O and the like. Since these unavoidable impurities may reduce the conductivity, the total amount is preferably 100 massppm or less.
Ti, Mg, Zr, Nb, Ca, V, Ni, Mn, and Cr may react with S in Cu to reduce the number of Cu—S-based compounds produced, and may reduce the conductivity. Therefore, it is preferable to limit the total content to 10 mass ppm or less.

(Fracture surface ratio in punched cross section: 20% or more)
When observing the cross section after the punching test, as shown in FIG. 2, when the surface formed by shearing is the shear surface and the other surface is the fracture surface, the fracture surface ratio = (fracture surface ratio If the cross-sectional area)/(shear surface area+fracture surface area) is 20% or more, burrs are less likely to occur during punching and the dimensional accuracy is improved. Further, it becomes possible to suppress wear of the mold and generation of punching scraps.

In order to further secure the punching workability, the fracture surface ratio in the punched cross section is preferably 25% or more, more preferably 30% or more. The upper limit of the fracture surface ratio is not particularly limited, but is preferably 80% or less.
The clearance of the die during the punching test is not particularly limited, but it is preferably set to about 5% of the plate thickness. The thickness of the sample during the punching test is preferably set to 0.3 to 3 mm.

(Tensile strength: 500 MPa or less)
In the pure copper plate of the present embodiment, the tensile strength of 500 MPa or less ensures the properties as a pure copper plate, and is particularly suitable as a material for a member for electronic and electric devices and a member for heat dissipation for large current applications. ..
The tensile strength of the pure copper plate is preferably 475 MPa or less, more preferably 450 MPa or less. The lower limit of the tensile strength of the pure copper plate is not particularly limited, but it is preferably 100 MPa or more.

(Conductivity: 90% IACS or more)
In the pure copper plate of the present embodiment, by setting the electrical conductivity to 90% IACS (International Annealed Copper Standard) or more, the properties as a pure copper plate are secured, and a member for electronic and electric devices for large current use and heat dissipation It is particularly suitable as a material for components.
The electric conductivity of the pure copper plate is preferably 95% IACS or more, and more preferably 97% IACS or more. The upper limit of the conductivity of the pure copper plate is not particularly limited, but it is preferably 103% IACS or less.

A method of manufacturing the pure copper plate of this embodiment having such a configuration will be described with reference to the flow chart shown in FIG.

(Melting/casting process S01)
The copper raw material is melted, S is added to adjust the components, and a molten copper is produced. As the copper raw material, for example, oxygen-free copper defined by C1020 is preferably used. A simple substance of S, a Cu—S master alloy, or the like can be used to add S. Also when producing a Cu—S master alloy, it is preferable to use oxygen-free copper specified by C1020. In the melting step, in order to reduce the hydrogen concentration, it is preferable to carry out atmosphere melting in an inert gas atmosphere (for example, Ar gas) having a low vapor pressure of H ₂ O to keep the holding time during melting to a minimum.
Then, the molten copper having the adjusted components is poured into a mold to produce an ingot. In consideration of mass production, it is preferable to use the continuous casting method or the semi-continuous casting method.
In the cooling process at the time of casting, a part of S reacts with Cu to form a Cu—S-based compound.

(Heat treatment step S02)
Heat treatment is performed for homogenization and solution treatment of the obtained ingot. In a non-oxidizing atmosphere or a reducing atmosphere, the heat treatment temperature of 500° C. or more and 900° C. or less is maintained for 1 hour or more and 8 hours or less.
By this heat treatment step S02, a part of S of the Cu—S based compound generated during casting is solid-dissolved, so that the Cu—S based compound can be generated again and dispersed uniformly in a later step. ..

(Hot working step S03)
Hot working is carried out in order to homogenize the structure and to uniformly disperse the Cu-S based compound produced by casting. In order to disperse the Cu-S compound, it is effective to set the end temperature of hot working to be high. Specifically, the hot working finish temperature is preferably 500° C. or higher, more preferably 550° C. or higher, even more preferably 600° C. or higher, and even more preferably 650° C. or higher. preferable.
The hot working temperature is preferably in the range of 500° C. or higher and 1000° C. or lower.

The total working rate of hot working is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more.
The cooling method after hot working is not particularly limited, but air cooling or water cooling is preferable.
The working method in the hot working step S03 is not particularly limited, and for example, rolling, extrusion, groove rolling, forging, pressing or the like can be adopted. When the final shape is a plate or strip, rolling is preferably adopted.

(Cold processing step S04)
Cold working is performed on the copper material after the hot working step S03 to work it into a predetermined shape. The temperature condition in the cold working step S04 is not particularly limited, but it is preferably performed in the range of −200° C. or higher and 200° C. or lower. The working rate in the cold working step S04 is appropriately selected so as to approximate the final shape, but it is preferably 30% or more in order to refine the crystal grains in the subsequent steps. When further improving the strength, it is more preferable that the processing rate is 50% or more.
The working method in the cold working step S04 is not particularly limited, and for example, rolling, extrusion, groove rolling, forging, pressing or the like can be adopted. When the final shape is a plate or strip, rolling is preferably adopted.

(Recrystallization heat treatment step S05)
A heat treatment for the purpose of recrystallization is performed on the copper material after the cold working step S04. In order to uniformly disperse the Cu—S compound, it is preferable to perform heat treatment at a temperature of 700° C. or lower.
The heat treatment condition of the recrystallization heat treatment step S05 is not particularly limited, but it is preferable to hold the heat treatment temperature in the range of 200° C. to 600° C. for 1 second to 24 hours.
In order to make the recrystallization structure uniform, the cold working step S04 and the recrystallization heat treatment step S05 may be repeated twice or more.

(Refining process S06)
In order to adjust the material strength, heat treatment may be performed on the copper material after the recrystallization heat treatment step S05. If it is not necessary to increase the material strength, refining may not be performed.
The processing rate of the refining process is not particularly limited, but it is preferably carried out within the range of 0% to 50% in order to adjust the material strength.
If necessary, in order to remove residual strain, a heat treatment may be further performed after the tempering process.

In this way, the pure copper plate of this embodiment is produced. There is no particular upper limit on the thickness of the pure copper plate, but when the punching process such as press working is performed on the pure copper plate to manufacture the electronic/electrical device member and the heat dissipation member, the thickness is 5.0 mm. If it exceeds, the load of the press machine will remarkably increase and the productivity per unit time will decrease, resulting in high cost. Therefore, in the present embodiment, the thickness of the pure copper plate is preferably 0.3 mm or more and 5.0 mm or less. The lower limit of the thickness of the pure copper plate is preferably 1.0 mm or more, more preferably 1.5 mm or more.

According to the pure copper plate of the present embodiment configured as described above, since S is contained in the range of 20 mass ppm or more and 1000 mass ppm or less, it is possible to generate a Cu—S-based compound, and Cu can be formed at the time of punching. Since the destruction starts from the —S-based compound, the punching workability can be improved. Further, by setting the content of S within the above range, it becomes possible to suppress deterioration of hot workability.
Since the purity of Cu excluding S is 99.96 mass% or more, and the balance is unavoidable impurities, the purity of copper is sufficiently high and the properties such as electrical conductivity and thermal conductivity and strength as a pure copper plate are secured. Therefore, it is suitable as a material for a member for electronic/electrical devices and a member for heat dissipation for large current applications.

In the present embodiment, when the total content of Pb and Bi, which are inevitable impurities, is 20 massppm or less, it is possible to prevent Pb and Bi having a low melting point from segregating at the grain boundaries and deteriorating the hot workability. Therefore, it is possible to further suppress the occurrence of hot working cracks.

In the present embodiment, when the content of P, which is an unavoidable impurity, is 5 massppm or less, it is possible to suppress the influence of P on the distribution state of the Cu—S based compound, and the Cu—S based compound is sufficiently added. Can be dispersed in This makes it possible to further improve the punching workability of the pure copper plate.

In this embodiment, when the fracture surface ratio in the punched cross section is 20% or more, the ratio of the sheared surface is sufficiently low, the occurrence of burrs during the punching process can be suppressed, and the dimensional accuracy can be improved. It will be possible. Further, it is possible to suppress wear of the mold and generation of punching scraps, and it is possible to efficiently perform punching.

In the present embodiment, when the tensile strength is 500 MPa or less, the characteristics as a pure copper plate are sufficiently ensured, so that it is suitable as a material for a member for electronic/electrical devices and a member for heat dissipation for large current applications. ..

In the present embodiment, when the electrical conductivity is 90% IACS or more, the characteristics as a pure copper plate are sufficiently ensured, and thus it is suitable as a material for a member for electronic/electrical equipment and a member for heat dissipation for large current applications. ing.

Since the electronic/electrical device member of the present embodiment is formed of the pure copper plate of the present embodiment described above, it has good shape accuracy and excellent conductivity. Therefore, it can be preferably used even in a large current application.
Since the heat dissipation member of the present embodiment is formed of the pure copper plate of the present embodiment described above, the shape accuracy is good and the heat conductivity is excellent. For this reason, it is possible to efficiently dissipate heat even in applications that generate a large amount of heat.

The pure copper plate, the member for electronic/electrical devices, and the member for heat dissipation, which are the embodiments of the present invention, have been described above, but the present invention is not limited to this, and within the scope not departing from the technical idea of the invention. It can be changed as appropriate.
For example, in the above-described embodiment, an example of the method for producing a pure copper plate has been described, but the method for producing a pure copper plate is not limited to the one described in the embodiment, and an existing production method may be appropriately selected. It may be manufactured.

The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.
A copper raw material made of oxygen-free copper (ASTM B152 C10100) having a purity of 99.99 mass% or more, and Cu-1 mass% S prepared by using pure S having a purity of 99 mass% or more for the oxygen-free copper having a purity of 99.99 mass% or more. A mother alloy was prepared.
Regarding Pb, Bi, and P, which are impurities, a mother alloy of each element is prepared from Pb, Bi, P having a purity of 99.9 mass% or more and pure copper having a purity of 99.9 mass%, and adjusted using the mother alloy. did.

The above-mentioned copper raw material was charged into a high-purity graphite crucible and subjected to high frequency melting in an atmosphere furnace in an Ar gas atmosphere. To the obtained copper melt, the above Cu-1 mass% S master alloy and a master alloy of various elements for adjusting the amount of impurities were added to prepare the composition shown in Table 1. The obtained copper melt was poured into a carbon mold and solidified at 10° C./sec. The ingot was produced by cooling at a cooling rate of. The size of the ingot was about 25 mm in thickness x about 60 mm in width x about 150 to 200 mm in length.

The obtained ingot was subjected to a heat treatment in the Ar gas atmosphere under the temperature condition shown in Table 2 for 1 hour, and then water-cooled.
The copper material after the heat treatment was cut and surface grinding was performed to remove the oxide film on the surface. At this time, the thickness of the copper material to be subjected to hot rolling is adjusted so that the final thickness is as shown in Table 2 in consideration of the rolling rates of the subsequent hot rolling, cold rolling and temper rolling. did.
The copper material, the thickness of which was adjusted as described above, was hot-rolled under the conditions shown in Table 2 and water-cooled.

The copper material after hot rolling was subjected to cold rolling at the rolling ratios shown in Table 2.
Next, the copper material after cold rolling was subjected to recrystallization heat treatment under the conditions shown in Table 2.
Then, the copper material after the recrystallization heat treatment was temper-rolled under the conditions shown in Table 2 to produce a strip for characteristic evaluation having a thickness shown in Table 2 and a width of 60 mm.

Then, the following items were evaluated. The evaluation results are shown in Table 3.

(Processability evaluation)
As an evaluation of workability, the presence or absence of edge cracks was observed during the above hot rolling and cold rolling.
"A" indicates that there was no or little ear cracking visually, "B" indicates that a small ear crack having a length of less than 1 mm occurred, and "B" indicates that a ear crack having a length of 1 mm or more and less than 3 mm occurred. "C", and those in which a large ear crack having a length of 3 mm or more occurred were designated as "D".
The length of the edge crack is the length of the edge crack extending from the end in the width direction of the rolled material toward the center in the width direction.

(Tensile strength)
A No. 13B test piece specified in JIS Z 2201 was sampled from the characteristic evaluation strip, and the tensile strength was measured according to JIS Z 2241.
The test piece was sampled so that the tensile direction of the tensile test was parallel to the rolling direction of the characteristic evaluation strip.

(conductivity)
A test piece having a width of 10 mm and a length of 60 mm was sampled from the characteristic evaluation strip, and the electrical resistance was determined by the four-terminal method. Moreover, the dimension 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 electric resistance value and the volume. The test piece was sampled so that its longitudinal direction was parallel to the rolling direction of the characteristic evaluation strip.

(Punching processability)
A large number of square holes (8 mm×8 mm) were punched out from the characteristic evaluation strip with a die, and the evaluation was performed by measuring the fracture surface ratio and the burr height. The clearance of the mold was appropriately adjusted so that the plate thickness ratio was 3%, and punching was performed at a punching speed of 50 spm (stroke per minute). The fracture surface ratio and the burr height were measured by observing the cut surface on the punching side (the punching surface parallel to the rolling direction of the characteristic evaluation strip) with an optical microscope and evaluating it as the average value of 10 punched samples. .. The punched surface was observed using an optical microscope, the surface generated by shear deformation was taken as the shear surface, and the portion obtained by subtracting the thickness of the shear surface from the sample thickness was taken as the fracture surface thickness. The fracture surface ratio was calculated as the fracture surface thickness/sample thickness. The burr height was measured from the longitudinal section of the punched sample using an optical microscope.

In Comparative Example 1, the S content was 2 massppm, which was smaller than the range of the present invention, so the fracture surface ratio was as low as 10% and the burr height was as large as 25 μm.
In Comparative Example 2, the S content was 1075 mass ppm, which was higher than the range of the present invention, and cracking occurred during hot working. Therefore, the subsequent processing and evaluation were stopped.

On the other hand, in Example 1-36 of the present invention in which the S content was in the range of 20 mass ppm to 1000 mass ppm, the fracture surface ratio was sufficiently high and the burr height was also small. Therefore, it was possible to perform punching with high dimensional accuracy. Further, it was excellent in workability during hot working and cold working.
In the present invention example 35 in which the total content of Pb and Bi exceeded 20 massppm, and in the present invention example 36 in which the P content exceeded 5 massppm, ear cracking was confirmed during hot working, but in practice, There was no problem.

From the above, according to the present invention example, it was confirmed that it is possible to provide a pure copper plate having excellent punching workability, capable of performing punching with high accuracy and efficiency.

Claims

A pure copper plate characterized in that the purity of Cu excluding S is 99.96 mass% or more, the balance is unavoidable impurities, and contains S in the range of 20 mass ppm to 1000 mass ppm.
The pure copper plate according to claim 1, wherein the total content of Pb and Bi is 20 massppm or less.
The pure copper plate according to claim 1 or 2, wherein the content of P is 5 massppm or less.
The pure copper plate according to any one of claims 1 to 3, wherein the fracture surface ratio in the punched cross section is 20% or more.
The pure copper plate according to any one of claims 1 to 4, which has a tensile strength of 500 MPa or less.
The pure copper plate according to any one of claims 1 to 5, which has an electrical conductivity of 90% IACS or more.
A member for electronic/electrical equipment, comprising the pure copper plate according to any one of claims 1 to 6.
A heat dissipation member comprising the pure copper plate according to any one of claims 1 to 6.