JP2020070476A - Copper alloy for electronic/electric machine, copper alloy thin plate for electronic/electric machine, conductive component for electronic/electric machine and terminal - Google Patents

Abstract

To provide a copper alloy for electronic/electric machine capable of industrially stable production, and having surely and sufficiently excellent stress corrosion crack resistance, and excellent flexure workability.SOLUTION: When a host phase containing Zn in the range of exceeding 7 mass% and less than 36.5 mass%, the balance made of Cu and inevitable impurities, and Cu, Zn and Sn with a surface orthogonal to a width direction of rolling as an observation surface is measured of a measurement area of 200 μmor larger by a measurement interval 0.03 μm according to an EBSD method and analyzed by removing measurement points where a CI value analyzed by a data analysis soft OIM is 0.1 or smaller, an area ratio of grain particles in which an aspect ratio b/a represented by a major axis a and a minor axis b of grain particles (including twin grain) is 0.1 or smaller is made 40% or larger of an entire area measured by Area fraction, and 0.2% bearing force is set to 300 MPa or larger and less than 650 MPa.SELECTED DRAWING: None

Description

  INDUSTRIAL APPLICABILITY The present invention is a Cu—Zn-based copper alloy for electronic and electrical equipment used as a connector for semiconductor devices, other terminals, movable conductive pieces for electromagnetic relays, and conductive components for electronic and electrical equipment such as lead frames. And a copper alloy thin plate for electronic / electrical equipment, a conductive component for electronic / electrical equipment, and a terminal using the same.

From the viewpoints of strength, workability, cost balance, etc., Cu—Zn alloys have been widely used as the above-mentioned electronic / electrical conductive parts.
In the electronic / electrical conductive component made of the Cu-Zn alloy described above, various kinds of metal plating may be applied to the surface of the base material made of the Cu-Zn alloy depending on the intended use. For example, in the case of a terminal such as a connector, tin (Sn) plating may be formed on the surface of a base material made of a Cu—Zn-based alloy in order to improve the reliability of contact with a mating conductive member.

  Here, for example, a conductive component for an electronic / electrical device such as a connector is generally formed into a predetermined shape by punching a thin plate (rolled plate) having a thickness of about 0.05 to 1.0 mm, and at least a part thereof. It is manufactured by subjecting a sheet to a bending process. In this case, it is used in such a manner that it is brought into contact with the mating conductive member near the bent portion to obtain an electrical connection with the mating conductive member, and that the contact portion with the mating conductive material is maintained by the spring property of the bent portion. ..

In the copper alloy for electronic / electrical devices used for such conductive parts for electronic / electrical devices, as described above, due to the spring property of the bending part, the mating conductive material is formed near the bending part. In the case of a connector or the like used to maintain the contact state, it is required to have excellent bendability.
Further, in the above-mentioned conductive parts for electronic / electrical devices, stress corrosion cracking may occur depending on the environment of use, so copper alloys for electronic / electrical devices used for conductive parts for electronic / electrical devices may be used. May require improvement in stress corrosion cracking resistance.

Therefore, for example, Patent Documents 1 and 2 propose methods for improving the stress corrosion cracking resistance of Cu—Zn alloys.
In Patent Document 1, the average crystal grain size of the Cu—Zn—Sn alloy is set to 3 μm or less, and the structure is free of the second phase in which Sn is enriched, so that stress corrosion cracking resistance and bending workability are obtained. I am trying to achieve both.
Further, Patent Document 2 describes that it is possible to improve the stress corrosion cracking resistance property by adding Ni and Si to a Cu—Zn alloy.

JP, 2007-056365, A JP, 2007-182615, A

  By the way, in the above-mentioned Patent Document 1, the component composition range is strictly defined so that the second phase is not generated, and the cooling rate from the liquidus temperature to 600 ° C. at the time of casting is 270 ° C./min or more. .. Therefore, when variations occur in the composition range and manufacturing conditions, a second phase enriched in Sn is generated, and a Cu-Zn-Sn alloy that achieves both stress corrosion cracking resistance and bending workability is obtained. It was difficult to industrially produce it stably.

  Further, in Patent Document 2, although the stress corrosion cracking resistance is improved by adding Ni or Si, it is necessary to perform an aging treatment in order to generate a precipitate, resulting in an increase in manufacturing cost. I will end up. In addition, depending on the production conditions, a coarse precipitate may be generated, and this coarse precipitate may deteriorate bending workability.

As described above, it has been difficult to industrially stably produce a Cu—Zn alloy having excellent stress corrosion cracking resistance and bending workability by the conventionally proposed methods.
Therefore, in the above-mentioned Cu-Zn alloy, it is strongly desired that both stress corrosion cracking resistance and bending workability can be achieved at the same time, and that stable production is possible.

  The present invention has been made under the circumstances as described above, and can be manufactured industrially stably, and the stress corrosion cracking resistance is surely and sufficiently excellent, and the bending workability is improved. An object of the present invention is to provide an excellent copper alloy for electronic / electrical devices, a thin copper alloy sheet for electronic / electrical devices using the same, a conductive component for electronic / electrical devices, and a terminal.

  In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive experiments and researches, and as a result, in a Cu-Zn alloy, by appropriately adjusting the aspect ratio of the crystal grain size of the matrix phase, stress corrosion resistance can be improved. It was found that the cracking characteristics can be reliably and sufficiently improved, and bending workability can be secured by adjusting the 0.2% proof stress within a predetermined range.

The present invention has been made based on the above findings, and the copper alloy for electronic / electrical devices according to the present invention contains Zn in a range of more than 7 mass% and less than 36.5 mass%, and the balance Cu. And an unavoidable impurity and a plane orthogonal to the width direction of the rolling as an observation plane, the mother phase containing Cu and Zn is measured by the EBSD method over a measurement area of 200 μm ² or more at a measurement interval of 0.03 μm. Then, when the analysis is performed excluding the measurement points where the CI value analyzed by the data analysis software OIM is 0.1 or less, the aspect expressed by the major axis a and the minor axis b of the crystal grain size (including twin). The area ratio of the crystal grains where the ratio b / a is 0.1 or less is 40% or more of the entire area measured by Area fraction, and the 0.2% proof stress is 300 MPa or more and 650MP or more. It is characterized in that it is less than.

  According to the copper alloy for electronic / electrical devices having the above-described configuration, the area ratio of the crystal grains in which the aspect ratio of the crystal grains of the mother phase is 0.1 or less is 40% or more of the entire area measured by Area fraction. Therefore, the stress corrosion cracking resistance is surely and sufficiently excellent.

  Note that the EBSD method means an electron backscatter diffraction pattern (EBSD) method using a scanning electron microscope with a backscattered electron diffraction image system, and OIM means a crystal obtained by using EBSD measurement data. Data analysis software for analyzing orientation (Orientation Imaging Microscopy: OIM). Further, the CI value is a reliability index (Confidence Index), which is a numerical value indicating the reliability of crystal orientation determination when analyzed using the analysis software OIM Analysis (Ver. 7.3.1) of the EBSD device. Is a numerical value displayed as (for example, “EBSD reader: In using OIM (revised 3rd edition)” by Seiichi Suzuki, September 2009, issued by TSL Solutions Co., Ltd.). Here, when the structure of the measurement point measured by EBSD and analyzed by OIM is a processed structure, the crystal pattern is not clear, so the reliability of crystal orientation determination becomes low and the CI value becomes low. Particularly, when the CI value is 0.1 or less, the structure at the measurement point is determined to be the processed structure.

Further, in the present invention, since the 0.2% proof stress is adjusted to 300 MPa or more and less than 650 MPa, the strength is high and the bending workability is excellent. Therefore, conductive parts for electronic / electrical devices of various shapes can be formed by bending.
Further, in the present invention, by controlling the aspect ratio of the crystal grains of the parent phase and controlling the 0.2% proof stress, both stress corrosion cracking resistance and bending workability are achieved, so the composition of the components and It is not necessary to strictly control the cooling conditions during casting, and industrially stable production is possible.

Here, the copper alloy for electronic / electrical devices of the present invention may contain one or two of Sn and Ni, and the total content of Sn and Ni may be 5 mass% or less.
In this case, by containing Sn and Ni in the above range, the strength can be improved and the stress relaxation resistance can be further improved. Further, in parts for electronic / electrical devices, Sn plating or Ni plating may be applied to the surface thereof, and thus Cu-Zn alloy scrap scraped with Sn plating or Ni is used as a raw material. Therefore, the recyclability is improved.

Further, the copper alloy for electronic / electrical devices of the present invention further contains one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag and P. The total content of these elements may be in the range of 0.001 mass% or more and 5 mass% or less.
In this case, various characteristics are improved by adding one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P as described above. It becomes possible. Therefore, the above-mentioned elements may be appropriately selected and added according to required characteristics.

Further, in the copper alloy for electronic / electrical equipment of the present invention, even if a W-bending test is performed using a W-type jig having a ratio of the plate thickness t to the bending radius R and R / t of 1, cracks are generated. It is preferable not to occur.
The copper alloy for electronic / electrical devices having such bending workability is particularly excellent in bending workability, and it becomes possible to form conductive parts for electronic / electrical devices of various shapes by bending.

The copper alloy thin plate for electronic / electrical equipment of the present invention is made of the rolled material of the above-mentioned copper alloy for electronic / electrical equipment, and is characterized by having a thickness in the range of 0.05 mm or more and 1.0 mm or less.
The copper alloy thin plate for electronic / electrical devices having such a configuration can be suitably used for connectors, other terminals, movable conductive pieces of electromagnetic relays, lead frames, and the like.

Here, in the copper alloy thin plate for electronic / electrical devices of the present invention, the surface may be metal-plated.
In this case, since the surface of the copper alloy thin plate for electronic / electrical equipment is metal-plated, surface characteristics suitable for the intended use can be imparted. As the metal plating, plating of Sn, Ni, Cu, Zn, Cr, Ag, Au and alloys thereof can be applied, and can be appropriately selected according to the intended use.

A conductive component for electronic / electrical equipment of the present invention is characterized by being made of the above-mentioned copper alloy for electronic / electrical equipment.
The terminal of the present invention is characterized by being made of the above-mentioned copper alloy for electronic / electrical devices.
Further, the conductive component for electronic / electrical equipment of the present invention is characterized by comprising the above-mentioned copper alloy thin plate for electronic / electrical equipment.
Further, the terminal of the present invention is characterized by being made of the above-mentioned copper alloy thin plate for electronic / electrical devices.

  According to the conductive parts and terminals for electronic / electrical devices having these configurations, since the stress corrosion cracking resistance is particularly excellent, stress corrosion cracking is suppressed over time or in a wet environment, so that the mating conductivity The contact pressure with the member can be maintained. Moreover, since it has excellent bending workability, it can be formed into various shapes.

  EFFECTS OF THE INVENTION According to the present invention, a copper alloy for electronic / electrical devices, which can be manufactured industrially stably, has excellent and reliable stress corrosion cracking resistance properties, and is excellent in bending workability, is used. It is possible to provide a thin copper alloy sheet for electronic / electrical equipment, a conductive component for electronic / electrical equipment, and a terminal.

It is a flow chart which shows the example of a process of the manufacturing method of the copper alloy for electronic and electric equipment of the present invention.

Below, the copper alloy for electronic and electric equipment which is one embodiment of the present invention is explained.
The copper alloy for electronic / electrical devices according to the present embodiment has a composition containing Zn in the range of more than 7 mass% and less than 36.5 mass% and the balance of Cu and unavoidable impurities.

  Further, in the copper alloy for electronic / electrical devices of the present embodiment, if necessary, any one or two of Sn and Ni are further contained, and the total content of Sn and Ni is set to 5 mass% or less. May be.

  Furthermore, in the copper alloy for electronic / electrical devices of the present embodiment, one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P, if necessary. Two or more kinds of elements may be contained, and the total content of these elements may be within the range of 0.001 mass% or more and 5 mass% or less.

  Further, in the copper alloy for electronic / electrical equipment of the present embodiment, the S content is preferably limited to less than 20 mass ppm.

  Here, the reason for defining the component composition as described above will be described below.

(Zn: more than 7 mass% and less than 36.5 mass%)
Zn is a basic alloying element in the copper alloy targeted in this embodiment, and is an element effective in improving strength and springiness. Since Zn is cheaper than Cu, it is effective in reducing the material cost of the copper alloy.
Here, if the Zn content is 7 mass% or less, the effect of reducing the material cost cannot be sufficiently obtained. On the other hand, when the content of Zn is 36.5 mass% or more, the corrosion resistance decreases and the cold rolling property also decreases.
Therefore, in the present embodiment, the content of Zn is set within the range of more than 7 mass% and less than 36.5 mass%.
The lower limit of the Zn content is preferably more than 8 mass%. Further, the upper limit of the Zn content is preferably 35 mass% or less, more preferably 25 mass% or less, further preferably 20 mass% or less, and further preferably less than 18 mass%, It is optimal that the content be 15 mass% or less.

(A total content of one or two of Sn and Ni: 5 mass% or less)
Studies by the present inventors have revealed that the addition of Sn and Ni has the effect of improving strength, and that addition of these also contributes to improvement of stress relaxation resistance. Therefore, it may be added if necessary.
Here, if the total content of Sn and Ni exceeds 5 mass%, the hot workability and the cold rollability may be deteriorated, and cracks may occur in the hot rolling or the cold rolling. The conductivity will also decrease.
Therefore, in the present embodiment, when any one or two kinds of Sn and Ni are contained, it is preferable that the total content of one or two kinds of Sn and Ni is 5 mass% or less.
The lower limit of the total content of one or two of Sn and Ni is preferably 0.1 mass% or more, and more preferably 0.3 mass% or more. Moreover, the upper limit of the total content of one or two of Sn and Ni is preferably 3 mass% or less, and more preferably 2 mass% or less.

(Total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, P: 0.001 mass% or more and 5 mass% or less)
Elements such as Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P have the effect of improving various characteristics of the copper alloy for electronic / electrical devices. Therefore, it may be appropriately selected and added depending on the required characteristics.
Here, when the total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P is less than 0.001 mass%, the action of these elements There is a possibility that the effect cannot be fully achieved. On the other hand, if the total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P exceeds 5 mass%, not only will the cost be increased. , There is a risk of reducing the conductivity.
Therefore, in the present embodiment, when one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag and P are contained, Co, Mn, It is preferable that the total content of one or more selected from Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P be within the range of 0.001 mass% or more and 5 mass% or less.

Here, one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag and P form coarse compounds with Cu, Zn and other elements. May occur. When one or more compounds having a particle size of 0.1 μm or more per 1 μm ² exist when SEM observation or the like is performed, this compound becomes a starting point of breakage, and bending workability may be deteriorated. Therefore, it is preferable that these additional elements be solid-dissolved in the mother phase containing Cu and Zn.
The upper limit of the total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P is preferably 3 mass% or less, and 2 mass. It is more preferable that the content is not more than%. Further, the lower limit of the total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P is preferably 0.002 mass% or more. ..

(S: less than 20 massppm)
S reacts with Zn in each process such as melting / casting and heat treatment to form ZnS. When ZnS is generated, residual stress is likely to occur in the vicinity of ZnS, and since it acts as a local battery, stress corrosion cracking resistance may deteriorate.
Therefore, in order to further improve the stress corrosion cracking resistance, the S content is preferably less than 20 massppm.
The upper limit of the S content is more preferably 15 massppm or less, and even more preferably 10 massppm or less. Further, the lower limit of the S content is not particularly specified, but it is preferable to set it to 0.1 ppm or more, and to set it to 0.5 ppm or more, because setting it to less than 0.1 ppm substantially increases the cost. More preferably, it is more preferably 1 ppm or more.

  The balance of the above elements may be basically Cu and inevitable impurities. Here, the unavoidable impurities include (Mg), (Al), (Mn), (Si), (Co), (Cr), (Ag), Ca, Sr, Ba, Sc, Y, Hf, and V. , Nb, Ta, Mo, W, Re, Ru, Os, Se, Te, Rh, Ir, Pd, Pt, (Au), Cd, Ga, In, Li, Ge, As, Sb, (Ti), Tl , Pb, Bi, (S), O, C, Be, N, H, Hg, B, (Zr), (Ni), (Sn), Fe, (P), and rare earths. The total amount of these unavoidable impurities is preferably 0.1 mass% or less.

Then, in the copper alloy for electronic / electrical equipment of the present embodiment, the mother phase containing Cu and Zn was measured by the EBSD method at 200 μm ² or more with the plane orthogonal to the rolling width direction as the observation plane. When the area is measured at a measurement interval of 0.03 μm and the major axis of the crystal grain size is a and the minor axis is b, the area ratio of the crystal grain with an aspect ratio b / a of 0.1 or less to the measured area is , Area fraction is 40% or more.

(aspect ratio)
By controlling the area ratio of the crystal grains having the aspect ratio b / a of 0.1 or less with respect to the measured area to 40% or more by Area fraction, stress corrosion cracking resistance is maintained while maintaining stress relaxation resistance. The characteristics can be improved.
In a material that has been subjected to rolling or the like, stress corrosion cracking generally propagates along grain boundaries in a direction perpendicular to the longitudinal direction. The major axis a of the crystal grains coincides with the longitudinal direction of the material, and the minor axis b coincides with the vertical direction. For this reason, when the area of the crystal grains having an aspect ratio b / a of 0.1 or less is 40% or more in the area fraction, the grain boundaries substantially along the vertical direction of the material are reduced. This makes it possible to suppress stress corrosion cracking.
Here, the area ratio of the crystal grains having the aspect ratio b / a of 0.1 or less to the measured area is preferably 50% or more, and more preferably 55% or more. The upper limit is not particularly specified, but if the area ratio of the crystal grains having an aspect ratio b / a of 0.1 or less exceeds 80% in area fraction, the substantial rolling cost increases, so the upper limit is set to 80% or less. Preferably. It is more preferably 75% or less.

  Further, in the copper alloy for electronic / electrical equipment of the present embodiment, the 0.2% proof stress is adjusted within the range of 300 MPa or more and less than 650 MPa.

(0.2% proof stress)
In the copper alloy for electronic / electrical devices according to the present embodiment, the strength is improved by work hardening by plastic working. When the contribution of strength due to this work hardening increases, a work structure is substantially formed, and thus workability such as ductility and bending workability deteriorates. Therefore, by setting the 0.2% proof stress to 300 MPa or more and less than 650 MPa, the area ratio to the measured area of the crystal grains having an aspect ratio b / a of 0.1 or less is controlled to 40% or more by Area fraction. The strength and bending workability can be improved.
The lower limit of the 0.2% proof stress is preferably 320 MPa or more, and more preferably 350 MPa or more. More preferably, it is 400 MPa or more.

  Next, a preferred example of the method for manufacturing the copper alloy for electronic / electrical devices of the above-described embodiment will be described with reference to the flowchart shown in FIG.

[Melting / casting process: S01]
First, a molten copper alloy having the above-described composition is prepared. As the copper raw material, it is desirable to use 4NCu (oxygen-free copper or the like) having a purity of 99.99 mass% or more, but scrap may be used as the raw material. In addition, an atmospheric atmosphere furnace may be used for melting, but a vacuum furnace, an inert gas atmosphere, or a reducing atmosphere atmosphere reducing atmosphere may be used to suppress the oxidation of the additional element.
Then, the ingot is obtained by casting the molten copper alloy with the adjusted components by an appropriate casting method, for example, a batch casting method such as die casting, or a continuous casting method, a semi-continuous casting method, a horizontal continuous casting method, or the like. ..

[Homogenization heat treatment step: S02]
Then, if necessary, homogenization heat treatment is performed to eliminate segregation of the ingot and homogenize the ingot structure, or to form a solid solution with inclusions and precipitates. The conditions for this homogenization heat treatment are not particularly limited, but heating at a temperature of 600 ° C. or more and 1000 ° C. or less for 1 hour or more and 24 hours or less is usually sufficient. If the heat treatment temperature is less than 600 ° C. or the heat treatment time is less than 1 hour, a sufficient homogenizing effect or solution effect may not be obtained. On the other hand, if the heat treatment temperature exceeds 1000 ° C., the segregation site may be partially dissolved, and if the heat treatment time exceeds 24 hours, the cost will only increase. The cooling conditions after the heat treatment may be appropriately determined, but usually water quenching may be performed. After the heat treatment, chamfering is performed if necessary.

[Hot working step: S03]
Then, hot working may be performed on the ingot in order to increase the efficiency of roughing and make the structure uniform. The conditions of this hot working are not particularly limited, but normally, it is preferable that the starting temperature is 600 ° C or more and 1000 ° C or less, the ending temperature is 550 ° C or more and 850 ° C or less, and the working rate is 50% or more. The ingot heating up to the hot working start temperature may also serve as the above-described homogenizing heat treatment step S02. The cooling conditions after the hot working may be appropriately determined, but usually water quenching may be performed. After the hot working, chamfering is performed if necessary. The working method of hot working is not particularly limited, but when the final shape is a plate or strip, hot rolling may be applied. Further, when the final shape is a wire or a bar, extrusion or groove rolling may be applied, and when the final shape is a bulk shape, forging or pressing may be applied.

[Rough plastic working process: S04]
Next, the ingot homogenized in the homogenizing heat treatment step S02 or the hot-worked material subjected to the hot working step S03 such as hot rolling is subjected to rough plastic working. The temperature condition in this rough plastic working step S04 is not particularly limited, but it is preferably set to less than 200 ° C. The working ratio of the intermediate plastic working is not particularly limited, but is usually about 10 to 99%. The processing method is not particularly limited, but if the final shape is a plate or strip, rolling may be applied. Further, when the final shape is a wire or rod, extrusion or groove rolling can be applied, and when the final shape is a bulk shape, forging or pressing can be applied.

[Solution heat treatment step: S05]
After the rough plastic working step S04, solution heat treatment for reducing segregation of Zn in the mother phase and for forming solid solution of inclusions and precipitates is performed. Usually, it is carried out at a temperature of 600 ° C. or higher and 1000 ° C. or lower for 0.1 second or longer and 24 hours or shorter. When heat treatment is performed at a high temperature, it is performed for a short time, and when heat treatment is performed at a low temperature, it is performed for a long time. After the solution heat treatment, it is preferable to cool to 300 ° C. or less at a cooling rate of 1 ° C./min or more. More preferably, it is 10 ° C./minute or more. The rough plastic working step S04 and the solution heat treatment step S05 may be repeated for thorough solution treatment.

[Intermediate plastic working process: S06]
Next, after the solution heat treatment step S05, intermediate plastic working is performed. The temperature condition in this intermediate plastic working step S06 is not particularly limited, but it is preferably less than 200 ° C. The working ratio of the intermediate plastic working is not particularly limited, but is usually about 10 to 99%. The processing method is not particularly limited, but if the final shape is a plate or strip, rolling may be applied. Further, when the final shape is a wire or rod, extrusion or groove rolling can be applied, and when the final shape is a bulk shape, forging or pressing can be applied.

[Intermediate heat treatment step: S07]
After the cold or warm intermediate plastic working step S06, an intermediate heat treatment for recrystallization treatment is performed. This intermediate heat treatment may be carried out under the condition of holding at a temperature of 300 ° C. to 800 ° C. for 1 second to 24 hours. When the above-mentioned additional elements are added, heat treatment conditions may be appropriately selected so that a compound is not formed by precipitation. Further, since the crystal grain size affects the stress corrosion cracking resistance to some extent, it is desirable to measure the recrystallized grains by the intermediate heat treatment and appropriately select the heating temperature and the heating time. That is, when the heat treatment temperature is high, the heat treatment time is short, and when the heat treatment temperature is low, the heat treatment time is long. Since the intermediate heat treatment and the subsequent cooling affect the final average crystal grain size, these conditions are selected so that the average crystal grain size of the matrix phase is in the range of 0.5 μm or more and 20 μm or less. Is preferable, and it is more preferable to select the thickness within the range of 1 μm or more and 15 μm or less.

As a specific method of the intermediate heat treatment, a batch type heating furnace may be used, or a continuous annealing line may be used for continuous heating. When using a batch-type heating furnace, it is desirable to heat at a temperature of 300 ° C. or higher and 600 ° C. or lower for 1 hour or longer and 24 hours or shorter, and when a continuous annealing line is used, a heating ultimate temperature of 500 ° C. or higher and 900 ° C. It is preferable that the temperature is within the following range and the temperature is kept within the range for 1 second or more and 5 minutes or less. The atmosphere for the intermediate heat treatment is preferably a non-oxidizing atmosphere (nitrogen gas atmosphere, inert gas atmosphere, reducing atmosphere).
The cooling conditions after the intermediate heat treatment are not particularly limited, but usually, cooling may be performed at a cooling rate of about 2000 ° C./sec to 100 ° C./hour.
The intermediate plastic working step S06 and the intermediate heat treatment step S07 may be repeated a plurality of times if necessary.

[Finishing plastic working process: S08]
After the intermediate heat treatment step S07, finish processing is performed to final dimensions and final shapes. The processing method is not particularly limited, but if the final product form is a plate or strip, rolling (cold rolling) may be applied. In addition, forging, pressing, groove rolling, etc. may be applied depending on the final product form. The processing ratio of the finish plastic working is an important step in that the area ratio of the crystal grains having an aspect ratio b / a of 0.1 or less to the measured area is 40% or more in the area fraction. When the processing rate is 70% or less, the area ratio of the crystal grains having the aspect ratio b / a of 0.1 or less to the measured area does not sufficiently increase. Further, if the processing rate is 98% or more, the rolling cost increases. Therefore, the processing rate is preferably more than 70% and 98%. It is more preferably 75% or more and less than 98%. In order to reliably increase the area ratio of the crystal grains having an aspect ratio b / a of 0.1 or less to the measured area, it is preferable to apply a tension of 1 MPa or more in the rolling direction.

[Finishing heat treatment step: S09]
After the finish plastic working, the finish heat treatment step S09 is performed for the purpose of improving the stress corrosion cracking resistance property by removing the residual strain and improving the bending workability. This finishing heat treatment is preferably performed at a temperature within the range of 200 ° C. or higher and 800 ° C. or lower for 1 second or more and 24 hours or less. If the temperature of the finishing heat treatment is less than 200 ° C. or the time of the finishing heat treatment is less than 1 second, the effect of sufficient strain relief may not be obtained, while if the temperature of the finishing heat treatment exceeds 800 ° C., recrystallization may occur. In addition, the finish heat treatment time of more than 24 hours only increases the cost.

Here, in the finishing heat treatment step S09, when the heat treatment temperature is high, the heat treatment time is short, and when the heat treatment temperature is low, the heat treatment time is long.
In this finishing heat treatment step S09, when the Vickers hardness Hv_CR at room temperature after the finishing plastic working step S08 and the Vickers hardness at room temperature after the finishing heat treatment step S09 are Hv_HT, the hardness difference ΔHv = Hv_CR-Hv_HT is By setting the aspect ratio b / a to 5 Hv or more, the 0.2% proof stress falls within the range of 300 MPa or more and less than 650 MPa without reducing the area ratio to the measured area of the crystal grains having an aspect ratio b / a of 0.1 or less. Furthermore, the ductility and bending workability are improved.
Here, when the value of ΔHv = Hv_CR-Hv_HT is less than 5Hv, bending workability may be deteriorated. On the other hand, when the value of ΔHv = Hv_CR-Hv_HT exceeds 30Hv, the area ratio of the crystal grains having the aspect ratio b / a of 0.1 or less may be less than 40%, and the stress corrosion cracking resistance is It may deteriorate.
The lower limit of ΔHv = Hv_CR-Hv_HT is preferably 7Hv or more. The upper limit of ΔHv = Hv_CR-Hv_HT is preferably less than 25Hv, more preferably less than 20Hv.

As described above, the copper alloy for electronic / electrical devices according to the present embodiment can be obtained. In this copper alloy for electronic / electrical devices, cracks do not occur even if a W-bending test is performed using a W-type jig having a ratio of plate thickness t to bending radius R and R / t of 1.
When rolling is applied as a processing method, a copper alloy thin plate (strip) for electronic / electrical equipment having a plate thickness of 0.05 mm or more and 1.0 mm or less can be obtained. Although such a thin plate may be used as it is for a conductive component for electronic / electrical equipment, one or both surfaces of the plate may be metal-plated with a film thickness of about 0.1 to 10 μm and provided with a metal plating. As a copper alloy strip, it is usually used for conductive parts for electronic and electric devices such as connectors and other terminals. The metal plating method in this case is not particularly limited. Moreover, you may perform a reflow process after electrolytic plating depending on the case.

In the copper alloy for electronic / electrical devices according to the present embodiment configured as described above, the area ratio to the measured area of the crystal grains in which the aspect ratio b / a of the matrix phase is 0.1 or less is Area fraction. Since it is 40% or more, the stress corrosion cracking resistance is surely and sufficiently excellent.
Furthermore, in the copper alloy for electronic / electrical devices of the present embodiment, the 0.2% proof stress is adjusted to 300 MPa or more and less than 650 MPa, and since it has excellent mechanical properties and excellent bending workability, for example, an electromagnetic relay It is suitable for conductive parts that require particularly high strength, such as the movable conductive piece or the spring part of the terminal.
In addition, in the copper alloy for electronic / electrical devices according to the present embodiment, as described above, by controlling the aspect ratio of the crystal grains of the matrix phase and controlling the 0.2% proof stress, stress corrosion cracking resistance can be improved. Since both properties and bending workability are compatible with each other, it is not necessary to strictly control the component composition, the cooling conditions at the time of casting, and the like, and industrially stable production is possible.

  In addition, in the copper alloy for electronic / electrical devices according to the present embodiment, when one or two kinds of Sn and Ni are contained and the total content of Sn and Ni is 5 mass% or less, the strength is Can be further improved, and the stress relaxation resistance can be further improved.

  Furthermore, the copper alloy for electronic / electrical devices according to the present embodiment contains one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P. However, when the total content of these elements is in the range of 0.001 mass% or more and 5 mass% or less, various characteristics can be improved.

  Further, in the copper alloy for electronic / electrical equipment according to the present embodiment, a W-shaped jig having a ratio of plate thickness t to bending radius R and R / t of 1 is used to perform W bending test. Since cracks do not occur, bending workability is particularly excellent, and it becomes possible to form conductive parts for electronic / electrical devices of various shapes by bending work.

The copper alloy thin plate for electronic / electrical equipment according to the present embodiment is made of a rolled material of the above-mentioned copper alloy for electronic / electrical equipment, and therefore has excellent stress relaxation resistance, stress corrosion cracking resistance, and bending workability. , A connector, other terminals, a movable conductive piece of an electromagnetic relay, a lead frame, and the like.
Further, when the surface is metal-plated, it is possible to obtain surface characteristics suitable for the intended use, and therefore various kinds of metal plating may be applied according to the intended use.

  A conductive member for electronic / electrical device according to the present embodiment, which is made of the above copper alloy thin plate for electronic / electrical device, and which is brought into contact with a mating conductive member to obtain an electrical connection with the mating conductive member. In addition, if at least a part of the plate surface is bent and the spring property of the bent part is maintained so as to maintain contact with the mating conductive material, copper for electronic / electrical equipment may be used. Since the alloy is particularly excellent in stress corrosion cracking resistance, stress corrosion cracking is suppressed over time or in a humid environment, so that the contact pressure with the mating conductive member can be maintained.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately modified without departing from the technical idea of the invention.
For example, although an example of the manufacturing method has been described, the present invention is not limited to this, and the finally obtained copper alloy for electronic / electrical devices has a composition within the scope of the present invention, and Cu and Zn. The aspect ratio and the 0.2% proof stress of the mother phase containing γ may be set within the range of the present invention.

  The results of confirmation experiments conducted to confirm the effects of the present invention are shown below as examples of the present invention together with comparative examples. The following examples are for explaining the effects of the present invention, and the configurations, processes, and conditions described in the examples do not limit the technical scope of the present invention.

First, a raw material made of Cu-40 mass% Zn master alloy and oxygen-free copper having a purity of 99.99 mass% or more (ASTM B152 C10100) was prepared, and this was charged in a high-purity graphite crucible, and in a N ₂ gas atmosphere. It melted using the electric furnace. Various additive elements were added to the copper alloy melt to melt the alloy melt having the component composition shown in Table 1, and the melt was poured into a carbon mold to produce an ingot. The size of the ingot was about 40 mm in thickness, about 70 mm in width, and about 100 mm in length.
Subsequently, as a homogenization treatment, each ingot was water-quenched after being held at a temperature shown in Table 2 for a predetermined time in an N ₂ gas atmosphere.

  Next, hot rolling was performed. Reheating is performed so that the hot rolling start temperature becomes the temperature shown in Table 2 so that the width direction of the ingot becomes the rolling direction, and the rolling end temperature is 600 ° C. or higher while performing appropriate reheating. I tried to be. After the hot rolling was finished, water quenching was performed, cutting and surface grinding were performed, and then a hot rolled material having a thickness of about 20 mm × a width of about 160 mm × a length of about 100 mm was produced.

Then, rough plastic working and solution heat treatment were performed.
Specifically, after cold rolling at a rolling ratio of about 20% or more, solution heat treatment was performed at a temperature shown in Table 2 for a predetermined time from 1 hour to 4 hours, and water quenching was performed.
After the solution heat treatment, cutting and surface grinding were performed, cold working was performed at a rolling rate of 70% or more, and intermediate heat treatment was performed at a temperature shown in Table 2 for 1 minute to 4 hours. After the intermediate heat treatment, cutting was performed and surface grinding was performed to remove the oxide film. Also, the crystal grain size was measured from the sample after the intermediate heat treatment, and it was confirmed that the average grain size was in the range of 3 to 10 μm in all of the present invention examples and comparative examples.

The average crystal grain size after the intermediate heat treatment was examined as follows.
A surface orthogonal to the width direction of rolling, that is, a TD (Transverse Direction) surface is used as an observation surface, mirror polishing and etching are performed, and then an optical microscope is used to photograph the rolling direction to be horizontal to the photograph. Observation was performed in a field of view of 1000 times (about 300 × 200 μm ² ). Then, according to the cutting method of JIS H 0501, draw five line segments each having a predetermined length in the vertical and horizontal directions of the photograph, count the number of crystal grains completely cut, and calculate the average value of the cut length. It was calculated as an average crystal grain size.

Then, finish rolling was carried out at the rolling ratios shown in Table 2.
Finally, after finishing heat treatment at a temperature shown in Table 2 for 1 minute to 4 hours, after water quenching, cutting and surface polishing, a strip for characteristic evaluation having a thickness of 0.25 mm and a width of about 160 mm. Was produced.
At this time, the hardness Hv_CR of the rolling surface before the finishing heat treatment, that is, the ND surface (Normal Direction) and the hardness Hv_HT of the ND surface after the finishing heat treatment were measured, and the hardness difference ΔHv = Hv_CR-Hv_HT was calculated. The Vickers hardness was measured by a test load of 1.96 N (= 0.2 kgf) or 0.98 N (= 0.1 kgf) according to the micro hardness test method defined in JIS-Z2248. The hardness difference ΔHv is shown in Table 2.

  With respect to these strips for property evaluation, the structure was observed and the aspect ratio of the matrix phase was evaluated. In addition, electrical conductivity, mechanical properties (proof stress), stress corrosion cracking resistance properties, and bending workability were evaluated. The test method and measurement method for each evaluation item are as follows, and the results are shown in Table 3.

〔aspect ratio〕
A surface orthogonal to the rolling width direction, that is, a TD surface (Transverse direction) is used as an observation surface, mechanical polishing is performed using water-resistant polishing paper and diamond abrasive grains, and then final polishing is performed using a colloidal silica solution. It was Then, an EBSD measurement device (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX / TSL (current AMETEK), and analysis software (manufactured by EDAX / TSL (current AMETEK) OIM Data Analysis ver.7.3). According to 1), each crystal grain (including twin) except the measurement point where the accelerating voltage of the electron beam is 20 kV, the measurement interval is 0.03 μm step, the measurement area is 200 μm ² or more, and the CI value is 0.1 or less. When the orientation difference between adjacent measurement points is 15 ° or more as a grain boundary and the major axis of the crystal grain size of each crystal grain is a and the minor axis is b, The Area Fraction of the aspect ratio represented by b / a was measured. Further, in the measurement of the aspect ratio, the grain size on EBSD was measured with a grain tolerance angle of 5 ° and a minimum grain size of 2 pixels.

〔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.

[Mechanical properties]
A No. 13B test piece specified in JIS Z 2201 was sampled from the characteristic evaluation strip, and 0.2% proof stress σ _0.2 was measured by the offset method of JIS Z 2241. The test pieces were taken so that the tensile direction of the tensile test was parallel to the rolling direction of the characteristic evaluation strip.

[Stress corrosion cracking resistance]
The stress corrosion cracking resistance characteristic is D. H. The investigation was conducted according to the stress corrosion cracking test method of THOMPSON (Materials, Res. And Stds. 1 (1961), P108-111). That is, a test piece having a width of 10 mm and a length of 60 mm is taken in parallel with the rolling direction, the center portion in the length direction is bent with a radius of curvature R: 2 mm, and the both ends are tied together to be restrained in a loop shape to reduce stress. After applying and holding for 24 hours at room temperature, once restraint was removed, initial displacement amount δ ₀ was measured, both ends were restrained again, and this was stored in a volume of 10 L storing 1 L of about 5% ammonia water. In a desiccator, the test piece constrained in a loop in a vapor phase is arranged and kept at 25 ° C. When the Zn content is 7 mass% or more and 15 mass% or less, after 96 hours, the Zn content is 15 mass%. When it was more than 36.5 mass% and less than 36.5 mass%, the loop-shaped restraint was removed after 24 hours, and the displacement amount δ ₁ of the test piece was measured. The residual stress rate (%) was calculated from the following equation using the measured initial displacement amount δ ₀ and displacement amount δ ₁ .
Residual stress rate (%) = (1-δ ₁ / δ ₀ ) × 100
When measured at n = 5, the average residual stress rate was evaluated as "⊚" when it was 80% or more, "○" when it was 50% or more and less than 80%, and "x" when it was less than 50%.

[Bending workability]
Bending was performed in accordance with 4 test methods of JCBA (Japan Copper and Brass Association technical standard) T307-2007. W-bending was performed so that the bending axis was orthogonal to the rolling direction. A plurality of test pieces having a width of 10 mm, a length of 30 mm, and a thickness of 0.25 mm were sampled from the characteristic evaluation strip, and a W-shaped jig having a bending angle of 90 degrees and a bending radius of 0.25 mm (plate thickness t and bending). A W-bending test was performed using a W-shaped jig whose ratio of radius R and R / t was 1.
A cracking test was performed on each of three samples, and those in which cracks were not observed in four visual fields of each sample were evaluated as “◯”, and those in which cracks were observed in one visual field or more were evaluated as “x”.

In Comparative Example 1 in which the Zn content was 39.8 mass%, the stress corrosion cracking resistance was insufficient. Therefore, bending workability was not evaluated.
In Comparative Example 2 in which the 0.2% proof stress was 706 MPa, the stress corrosion cracking resistance was good, but the bending workability was insufficient.
In Comparative Examples 3 and 4 in which the proportion of crystal grains having an aspect ratio of 0.1 or less was less than 40%, the stress corrosion cracking resistance was insufficient. Therefore, bending workability was not evaluated.

On the other hand, in Inventive Examples 1-18, the stress corrosion cracking resistance and bending workability were excellent. Moreover, it was also excellent in conductivity and proof stress.
From the above, according to the present invention example, it is confirmed that it is possible to provide a copper alloy for electronic / electrical devices, which is surely and sufficiently excellent in stress corrosion cracking resistance, and which is also excellent in bending workability. It was

Claims (10)

Zn is contained in the range of more than 7 mass% and less than 36.5 mass%, the balance being Cu and inevitable impurities,
Using a plane orthogonal to the width direction of rolling as an observation plane, a mother phase containing Cu and Zn was measured by the EBSD method over a measurement area of 200 μm ² or more at a measurement interval of 0.03 μm, and data analysis software OIM was used. When the analysis is performed excluding the measurement points having a CI value of 0.1 or less, the aspect ratio b / a represented by the major axis a and the minor axis b of the crystal grain size (including twin) is 0. The area ratio of the crystal grains of 1 or less is 40% or more of the entire area measured by Area fraction, and
A 0.2% proof stress of 300 MPa or more and less than 650 MPa, a copper alloy for electronic and electric devices.   The copper alloy for electronic / electrical devices according to claim 1, further comprising any one or two of Sn and Ni, wherein the total content of Sn and Ni is 5 mass% or less.   Further, it contains one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag and P, and the total content of these elements is 0.001 mass% or more and 5 mass. % Or less, and the copper alloy for electronic / electrical devices according to claim 1 or 2, characterized in that   4. A crack does not occur even if a W bending test is carried out using a W type jig having a ratio of the plate thickness t to the bending radius R and R / t of 1. 4. The copper alloy for electronic / electrical devices according to any one of claims.   An electronic device comprising the rolled material of the copper alloy for electronic / electrical device according to any one of claims 1 to 4, and having a thickness of 0.05 mm or more and 1.0 mm or less. Copper alloy sheet for electrical equipment. The copper alloy thin plate for electronic / electrical devices according to claim 5,
Copper alloy thin plate for electronic and electrical equipment, whose surface is plated with metal.   A conductive component for electronic / electrical equipment, comprising the copper alloy for electronic / electrical equipment according to any one of claims 1 to 4.   A terminal comprising the copper alloy for electronic / electrical devices according to claim 1.   A conductive component for electronic / electrical equipment, comprising the copper alloy thin plate for electronic / electrical equipment according to claim 5 or 6.   A terminal comprising the copper alloy thin plate for electronic / electrical device according to claim 5 or 6.

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