JP7187989B2 - Copper alloys for electronic and electrical equipment, copper alloy sheets for electronic and electrical equipment, conductive parts and terminals for electronic and electrical equipment - Google Patents

Description

The present invention relates to a Cu--Zn based copper alloy for electronic and electrical equipment, which is used as a connector of a semiconductor device, other terminals, a movable conductive piece of an electromagnetic relay, and a conductive part for electronic and electrical equipment such as a lead frame. and a copper alloy sheet for electronic/electrical equipment, a conductive component for electronic/electrical equipment, and a terminal using the same.

Cu--Zn alloys have been widely used as the above-described electronic/electrical conductive parts from the viewpoint of strength, workability, cost balance, and the like.
In addition, in the electronic/electrical conductive parts made of the Cu—Zn alloy described above, the surface of the base material made of the Cu—Zn alloy may be plated with various metals depending on the intended use. For example, in the case of a terminal such as a connector, tin (Sn) plating is sometimes formed on the surface of a base material made of a Cu—Zn alloy in order to improve the reliability of contact with a mating conductive member.

Here, for example, a conductive component for electronic and electrical equipment such as a connector is generally made 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 of it is It is manufactured by bending the In this case, it is used so that it is brought into contact with the counterpart conductive member in the vicinity of the bent portion to obtain electrical connection with the counterpart conductive member, and the contact state with the counterpart conductive member is maintained by the springiness of the bent portion. .

In the copper alloy for electronic/electrical devices used in such conductive parts for electronic/electrical devices, as described above, bending is performed, and the springiness of the bent portion allows the contact with the mating conductive material in the vicinity of the bent portion. In the case of a connector or the like used to maintain the contact state between the two, excellent bending workability is required.
In addition, since stress corrosion cracking may occur in the conductive parts for electronic and electrical equipment described above, depending on the usage environment, copper alloys for electronic and electrical equipment used in conductive parts for electronic and electrical equipment is sometimes required to improve 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 Cu—Zn—Sn alloy has an average crystal grain size of 3 μm or less, and a structure without a second phase in which Sn is concentrated, thereby improving stress corrosion cracking resistance and bending workability. We are trying to achieve both
Further, Patent Document 2 describes that the addition of Ni and Si to a Cu—Zn alloy can improve stress corrosion cracking resistance.

JP 2007-056365 A JP 2007-182615 A

By the way, in the above-mentioned Patent Document 1, the composition range is strictly defined so as not to generate the second phase, and the cooling rate from the liquidus temperature to 600 ° C. at the time of casting is set to 270 ° C./min or more. . For this reason, when there is variation in the composition range and manufacturing conditions, a second phase in which Sn is concentrated is generated, and a Cu-Zn-Sn alloy that achieves both stress corrosion cracking resistance and bending workability is produced. It was difficult to stably produce it industrially.

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 precipitates, which increases the manufacturing cost. put away. In addition, depending on the manufacturing conditions, coarse precipitates may be formed, and there is a risk that these coarse precipitates may deteriorate bending workability.

As described above, it has been difficult to industrially stably produce a Cu—Zn alloy with excellent stress corrosion cracking resistance and bending workability by the conventionally proposed methods.
Therefore, it is strongly desired that the above-mentioned Cu--Zn-based alloys are capable of achieving both stress corrosion cracking resistance and bending workability, and that they can be stably produced.

The present invention has been made against the background of the circumstances described above. An object of the present invention is to provide an excellent copper alloy for electronic/electrical equipment, a copper alloy sheet for electronic/electrical equipment using the same, a conductive component and a terminal for electronic/electrical equipment.

In order to solve the above-mentioned problems, the inventors of the present invention conducted extensive experiments and studies, and found that stress corrosion resistance was improved by appropriately adjusting the aspect ratio of the crystal grain size of the parent phase in a Cu—Zn alloy. The inventors have found that the cracking property can be reliably and sufficiently improved, and that bending workability can be ensured 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 and 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 is Cu and unavoidable impurities, the S content is less than 20 ppm by mass, and the mother phase containing Cu and Zn is measured by the EBSD method to a thickness of ²⁰⁰ μm The measured area of is measured at a measurement interval of 0.03 μm step, and analyzed by data analysis software OIM except for the measurement points where the CI value is 0.1 or less. The area ratio of crystal grains whose aspect ratio b/a represented by the major axis a and the minor axis b is 0.1 or less is 40% or more of the entire measured area by area fraction, and 0.1. It is characterized by having a 2% proof stress of 300 MPa or more and less than 650 MPa.

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

The EBSD method means an electron beam reflection diffraction pattern (EBSD) method using a scanning electron microscope equipped with a backscattered electron diffraction image system, and OIM refers to a crystal using measurement data from EBSD. Data analysis software for analyzing orientation is Orientation Imaging Microscopy (OIM). Furthermore, the CI value is a confidence index, which is a numerical value representing the reliability of crystal orientation determination when analyzed using the analysis software OIM Analysis (Ver.7.3.1) of the EBSD equipment. (for example, "EBSD Reader: Using OIM (Revised 3rd Edition)" by Seiichi Suzuki, September 2009, published by TSL Solutions Co., Ltd.). Here, when the structure at the measurement point measured by EBSD and analyzed by OIM is a worked structure, the crystal pattern is not clear, so the reliability of crystal orientation determination is low, and the CI value is low. In particular, when the CI value is 0.1 or less, the structure at the measurement point is judged to be a processed structure.

Furthermore, in the present invention, the 0.2% proof stress is adjusted to 300 MPa or more and less than 650 MPa, so that the strength is high and the bending workability is excellent. Therefore, various shapes of conductive parts for electronic/electrical devices can be formed by bending.
In addition, 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. There is no need to strictly control cooling conditions and the like during casting, and industrially stable production is possible.

Here, the copper alloy for electronic and electrical devices of the present invention may contain either 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 within the ranges described above, the strength can be improved, and the stress relaxation resistance can be further improved. In addition, in electronic and electrical equipment parts, since the surface may be subjected to Sn plating or Ni plating, these Cu-Zn alloy scraps with Sn plating or Ni plating are used as raw materials. can be used, and recyclability will be improved.

The copper alloy for electronic and 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, by adding one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P as described above, various properties are improved. becomes possible. Therefore, the above elements may be appropriately selected and added according to the required properties.

Furthermore, in the copper alloy for electronic and electrical devices of the present invention, a W-shaped jig in which the ratio of the plate thickness t to the bending radius R, R / t, is 1, and a W-bending test is performed without cracks. preferably not occur.
According to the copper alloy for electronic/electrical equipment having such bending workability, the bending workability is particularly excellent, and it becomes possible to form various shapes of conductive parts for electronic/electrical equipment by bending.

A copper alloy sheet for electronic/electrical devices according to the present invention is characterized by being made of the rolled material of the above copper alloy for electronic/electrical devices and having a thickness in the range of 0.05 mm or more and 1.0 mm or less.
A copper alloy thin plate for electronic and electrical equipment having such a structure 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 sheet for electronic and electrical devices of the present invention, the surface may be plated with a metal.
In this case, since the surface of the copper alloy sheet for electronic/electrical equipment is metal-plated, suitable surface properties can be imparted according to the intended use. As 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 according to the present invention is characterized by comprising the copper alloy for electronic/electrical equipment described above.
Further, a terminal of the present invention is characterized by being made of the copper alloy for electronic/electrical devices described above.
Further, a conductive component for electronic/electrical equipment according to the present invention is characterized by comprising the copper alloy thin plate for electronic/electrical equipment described above.
Further, a terminal of the present invention is characterized by comprising the copper alloy thin plate for electronic/electrical equipment described above.

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

INDUSTRIAL APPLICABILITY According to the present invention, a copper alloy for electronic and electrical devices that can be industrially stably produced, has reliably and sufficiently excellent resistance to stress corrosion cracking, and has excellent bending workability, and use thereof It is possible to provide a copper alloy sheet for electronic/electrical equipment, a conductive component and a terminal for electronic/electrical equipment.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows the process example of the manufacturing method of the copper alloy for electronic/electrical devices of this invention.

A copper alloy for electronic and electrical devices, which is one embodiment of the present invention, will be described below.
The copper alloy for electronic and electrical devices according to the present embodiment has a composition containing Zn in a range of more than 7 mass% and less than 36.5 mass%, with the balance being Cu and unavoidable impurities.

In addition, the copper alloy for electronic and electrical devices according to the present embodiment further contains either one or two of Sn and Ni, and the total content of Sn and Ni is 5 mass% or less. may be

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

Moreover, in the copper alloy for electronic and electrical devices of the present embodiment, the S content is preferably limited to less than 20 ppm by mass.

Here, the reasons for specifying 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. Moreover, 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 material cost reduction effect cannot be sufficiently obtained. On the other hand, when the Zn content is 36.5 mass % or more, the corrosion resistance is lowered and the cold rollability is also lowered.
Therefore, in the present embodiment, the content of Zn is within the range of more than 7 mass% and less than 36.5 mass%.
In addition, the lower limit of the Zn content is preferably more than 8 mass%. In addition, the upper limit of the Zn content is preferably 35 mass% or less, more preferably 25 mass% or less, more preferably 20 mass% or less, and further preferably less than 18 mass%. It is optimal to make it 15 mass% or less.

(Total content of either one or two of Sn and Ni: 5 mass% or less)
The inventors' research has revealed that the addition of Sn and Ni is effective in improving the strength, and that the addition of these also contributes to the improvement of the stress relaxation resistance. Therefore, it may be added as necessary.
Here, if the total content of Sn and Ni exceeds 5 mass%, the hot workability and cold rollability may deteriorate, and cracks may occur during hot rolling or cold rolling. The electrical conductivity also decreases.
Therefore, in the present embodiment, when one or both of Sn and Ni are contained, the total content of either one or two of Sn and Ni is preferably 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, more preferably 0.3 mass % or more. Also, the upper limit of the total content of one or two of Sn and Ni is preferably 3 mass % or less, more preferably 2 mass % or less.

(Total content of one or more selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and 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 properties of copper alloys for electronic and electrical devices. Therefore, it may be appropriately selected and added according to the required properties.
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 sufficiently achieved. On the other hand, when 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 does the cost increase, , may reduce conductivity.
Therefore, in the present embodiment, when containing one or more elements selected from Co, Mn, Mg, Ti, Al, Si, Cr, Zr, Au, Ag and P, Co, Mn, The total content of one or more selected from Mg, Ti, Al, Si, Cr, Zr, Au, Ag, and P is preferably in 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 There is a risk of If 1 or more compounds with a particle size of 0.1 μm or more are present per 1 μm ² in SEM observation, etc., this compound may act as a starting point for fracture, which may reduce bending workability. Therefore, these additive elements are preferably dissolved in the mother phase containing Cu and Zn.
In addition, 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 % or less is more preferable. In addition, 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 ppm by mass)
S reacts with Zn in each process such as melting/casting and heat treatment to form ZnS. When ZnS is generated, residual stress tends to occur in the vicinity of ZnS, and since it acts as a local battery, there is a possibility that stress corrosion cracking resistance will be deteriorated.
Therefore, in order to further improve the stress corrosion cracking resistance, the S content is preferably less than 20 ppm by mass.
The upper limit of the S content is more preferably 15 ppm by mass or less, more preferably 10 ppm by mass or less. The lower limit of the S content is not particularly defined, but if it is less than 0.1 ppm, it substantially increases the cost, so it is preferably 0.1 ppm or more, and preferably 0.5 ppm or more. More preferably, it is more preferably 1 ppm or more.

The balance of each of the above elements should basically be Cu and unavoidable impurities. Here, the unavoidable impurities include (Mg), (Al), (Mn), (Si), (Co), (Cr), (Ag), Ca, Sr, Ba, Sc, Y, Hf, 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), rare earth elements, and the like. The total amount of these unavoidable impurities is desirably 0.1 mass % or less.

Then, in the copper alloy for electronic and electrical devices of the present embodiment, the mother phase containing Cu and Zn is measured by the EBSD method with a surface orthogonal to the width direction of the rolling as an observation surface of 200 μm ² or more. The area is measured in steps of 0.03 μm, and the major axis of the crystal grain is a, and the minor axis is b. , Area fraction is 40% or more.

(aspect ratio)
By controlling the area ratio of the crystal grains with the aspect ratio b / a of 0.1 or less to the measured area to be 40% or more by area fraction, stress corrosion cracking resistance is prevented while maintaining the stress relaxation resistance. characteristics can be improved.
In a material that has undergone rolling or the like, stress corrosion cracking generally progresses 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. Therefore, the area of crystal grains with an aspect ratio b/a of 0.1 or less is the area fraction. This makes it possible to suppress stress corrosion cracking.
Here, the ratio of the area of the crystal grains having an aspect ratio b/a of 0.1 or less to the measured area is preferably 50% or more, more preferably 55% or more. Although the upper limit is not particularly defined, if the area fraction of crystal grains with an aspect ratio b / a of 0.1 or less exceeds 80% in area fraction, the substantial rolling cost will increase, so it is set to 80% or less. is preferred. More preferably, it is 75% or less.

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

Next, a preferred example of the method for producing a copper alloy for electronic/electrical devices according to the embodiment as described above will be described with reference to the flow chart shown in FIG.

[Melting/casting process: S01]
First, a molten copper alloy having the composition described above is melted. As the copper raw material, it is desirable to use 4NCu (oxygen-free copper, etc.) with a purity of 99.99 mass % or more, but scrap may be used as the raw material. For the melting, an air atmosphere furnace may be used, but a vacuum furnace, an inert gas atmosphere or a reducing atmosphere furnace may be used in order to suppress the oxidation of the additive element.
Next, the molten copper alloy whose composition has been adjusted is cast by an appropriate casting method, for example, a batch type casting method such as die casting, or a continuous casting method, a semi-continuous casting method, a horizontal continuous casting method, or the like to obtain an ingot. .

[Homogenization heat treatment step: S02]
Thereafter, if necessary, a homogenization heat treatment is performed to eliminate segregation in the ingot to homogenize the ingot structure, or to dissolve inclusions and precipitates. The conditions for this homogenization heat treatment are not particularly limited, but generally, the heating may be performed at a temperature of 600° C. or higher and 1000° C. or lower for 1 hour or longer and 24 hours or shorter. If the heat treatment temperature is less than 600° C. or the heat treatment time is less than 1 hour, a sufficient homogenization effect or solutionizing effect may not be obtained. On the other hand, if the heat treatment temperature exceeds 1000° C., the segregation sites may be partially dissolved, and if the heat treatment time exceeds 24 hours, the cost only increases. The cooling conditions after the heat treatment may be appropriately determined, but usually water quenching is sufficient. In addition, after heat treatment, chamfering is performed as needed.

[Hot working step: S03]
Then, the ingot may be subjected to hot working in order to improve the efficiency of rough working and homogenize the structure. The conditions for this hot working are not particularly limited, but it is usually preferred that the starting temperature is 600° C. or higher and 1000° C. or lower, the finishing temperature is 550° C. or higher and 850° C. or lower, and the working ratio is 50% or higher. The heating of the ingot to the hot working start temperature may also serve as the homogenization heat treatment step S02. The cooling conditions after hot working may be appropriately determined, but usually water quenching is sufficient. In addition, after hot working, chamfering is performed as needed. The method of hot working is not particularly limited, but if the final shape is a plate or strip, hot rolling may be applied. When the final shape is a wire or 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 step: S04]
Next, the ingot homogenized in the homogenization 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. Although the temperature condition in this rough plastic working step S04 is not particularly limited, it is preferably less than 200.degree. The working ratio of the intermediate plastic working is also not particularly limited, but is usually about 10 to 99%. The processing method is not particularly limited, but when the final shape is a plate or strip, rolling may be applied. Further, when the final shape is a wire or bar, 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, a solution heat treatment is performed to reduce the segregation of Zn in the matrix phase and dissolve inclusions and precipitates. Usually, it is carried out at a temperature of 600° C. or more and 1000° C. or less for 0.1 second or more and 24 hours or less. When the heat treatment is performed at a high temperature, the heat treatment is performed for a short time, and when the heat treatment is performed at a low temperature, the heat treatment is performed for a long time. After the solution heat treatment, it is preferable to cool to 300° C. or lower at a cooling rate of 1° C./min or more. More preferably, it is 10°C/min or more. For thorough solution treatment, the rough plastic working step S04 and the solution heat treatment step S05 may be repeated.

[Intermediate plastic working step: S06]
Next, intermediate plastic working is applied after the solution heat treatment step S05. Although the temperature condition in this intermediate plastic working step S06 is not particularly limited, it is preferably less than 200.degree. The working ratio of the intermediate plastic working is also not particularly limited, but is usually about 10 to 99%. The processing method is not particularly limited, but when the final shape is a plate or strip, rolling may be applied. Further, when the final shape is a wire or bar, 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 is performed for recrystallization. This intermediate heat treatment is usually carried out at a temperature of 300° C. to 800° C. for 1 second to 24 hours. When the additive element described above is added, the heat treatment conditions may be appropriately selected so as not to form a compound due to precipitation. Furthermore, since the grain size affects the resistance to stress corrosion cracking to some extent, it is desirable to measure the recrystallized grains in the intermediate heat treatment and appropriately select the heating temperature and heating time conditions. That is, when the heat treatment temperature is high, the heat treatment time is shortened, and when the heat treatment temperature is low, the heat treatment time is lengthened. Since the intermediate heat treatment and subsequent cooling affect the final average crystal grain size, these conditions are selected so that the average crystal grain size of the matrix is in the range of 0.5 μm or more and 20 μm or less. It is more preferable to select the thickness within the range of 1 μm or more and 15 μm or less.

As a specific technique for 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. It is preferable to keep the temperature within that range for about 1 second or more and 5 minutes or less. Moreover, the atmosphere of 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 the cooling rate is about 2000° C./second to 100° C./hour.
Note that the intermediate plastic working step S06 and the intermediate heat treatment step S07 may be repeated multiple times as necessary.

[Finish plastic working step: S08]
After the intermediate heat treatment step S07, finish machining is performed up to the final dimensions and final shape. 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, or the like may be applied depending on the form of the final product. The working rate of the finish plastic working is an important process for achieving an area fraction of 40% or more of the crystal grains having an aspect ratio b/a of 0.1 or less with respect to the measured area. If the processing ratio is 70% or less, the area ratio of the crystal grains with the aspect ratio b/a of 0.1 or less to the measured area does not sufficiently increase. Moreover, when the processing rate is 98% or more, the rolling cost increases. For this reason, it is preferable that the processing rate is in the range of more than 70% and 98%. More preferably, it is 75% or more and less than 98%. In order to reliably increase the area ratio of crystal grains with 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.

[Finish heat treatment step: S09]
After finish plastic working, a finish heat treatment step S09 is performed for the purpose of improving stress corrosion cracking resistance and bending workability by removing residual strain. This finishing heat treatment is desirably performed at a temperature in the range of 200° C. or higher and 800° C. or lower for 1 second or longer and 24 hours or shorter. If the temperature of the finish heat treatment is less than 200°C or the time of the finish heat treatment is less than 1 second, there is a risk that a sufficient strain relief effect will not be obtained. Moreover, the time for finishing heat treatment exceeding 24 hours only leads to an increase in cost.

Here, in the finishing heat treatment step S09, when the heat treatment temperature is high, the heat treatment time is shortened, and when the heat treatment temperature is low, the heat treatment time is lengthened.
Then, in the 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 The 0.2% proof stress is within the range of 300 MPa or more and less than 650 MPa without reducing the area ratio of the crystal grains with an aspect ratio b / a of 0.1 or less to the measured area by setting it to 5 Hv or more, Furthermore, it aims to improve ductility and bending workability.
Here, if the value of ΔHv=Hv_CR-Hv_HT is less than 5Hv, there is a risk that the bending workability will deteriorate. On the other hand, when the value of ΔHv=Hv_CR-Hv_HT exceeds 30Hv, the area ratio of crystal grains with an aspect ratio b/a of 0.1 or less may be less than 40%, and stress corrosion cracking resistance is poor. It may deteriorate.
The lower limit of ΔHv=Hv_CR-Hv_HT is preferably 7Hv or more. Also, the upper limit of ΔHv=Hv_CR-Hv_HT is preferably less than 25 Hv, more preferably less than 20 Hv.

As described above, the copper alloy for electronic/electrical devices according to the present embodiment can be obtained. In this copper alloy for electronic and electrical devices, cracks do not occur even when a W-shaped jig having a ratio of thickness t to bending radius R (R/t) of 1 is used to conduct a W-bending test.
Moreover, when rolling is applied as the processing method, a copper alloy thin plate (strip) for electronic and electrical equipment having a thickness of 0.05 mm or more and 1.0 mm or less can be obtained. Such a thin plate may be used as it is for conductive parts for electronic and electrical equipment, but one or both sides of the plate surface is plated with a metal plate having a thickness of about 0.1 to 10 μm. As a copper alloy strip, it is usually used for conductive parts for electronic and electrical equipment such as connectors and other terminals. The method of metal plating in this case is not particularly limited. In some cases, reflow treatment may be performed after electroplating.

In the copper alloy for electronic and electrical devices according to the present embodiment configured as described above, the area ratio of crystal grains having an aspect ratio b/a of 0.1 or less in the mother phase to the measured area is defined as Area fraction and 40% or more, the stress corrosion cracking resistance is reliably and sufficiently excellent.
Furthermore, in the copper alloy for electronic and electrical devices of the present embodiment, the 0.2% proof stress is adjusted to 300 MPa or more and less than 650 MPa, and has excellent mechanical properties and excellent bending workability. It is suitable for conductive parts that require particularly high strength, such as movable conductive pieces or spring portions of terminals.
In addition, in the copper alloy for electronic and electrical devices of the present embodiment, as described above, by controlling the aspect ratio of the crystal grains of the parent phase and controlling the 0.2% proof stress, stress corrosion cracking resistance Since both properties and bending workability are achieved, there is no need to strictly control the composition, cooling conditions during casting, etc., and industrially stable production is possible.

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

Furthermore, the copper alloy for electronic and electrical devices of 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 properties can be improved.

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

Since the copper alloy sheet for electronic/electrical devices according to the present embodiment is made of the rolled material of the copper alloy for electronic/electrical devices described above, it has excellent stress relaxation resistance, stress corrosion cracking resistance, and bending workability. , connectors, other terminals, movable conductive pieces of electromagnetic relays, lead frames, and the like.
In addition, when the surface is plated with a metal, it is possible to obtain surface properties suitable for the intended use, so various metal platings may be applied depending on the intended use.

The conductive member for electronic/electrical equipment of the present embodiment is made of the copper alloy thin plate for electronic/electrical equipment described above, and is brought into contact with the counterpart conductive member to obtain electrical connection with the counterpart conductive member. In addition, when at least a part of the plate surface is subjected to bending and the springiness of the bent portion is used to maintain contact with the mating conductive material, copper for electronic and electrical equipment Since the alloy is particularly excellent in stress corrosion cracking resistance, stress corrosion cracking over time or in a wet environment is also suppressed, so 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 modified as appropriate without departing from the technical idea of the invention.
For example, although an example of the production method has been described, it is not limited to this, and the finally obtained copper alloy for electronic and electrical devices has a composition within the scope of the present invention, and contains Cu and Zn. The aspect ratio and 0.2% proof stress of the mother phase containing should be set within the scope of the present invention.

Hereinafter, the results of confirmatory experiments conducted to confirm the effects of the present invention will be shown as examples of the present invention together with comparative examples. The following examples are intended to illustrate 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 consisting of a Cu-40 mass% Zn mother alloy and oxygen-free copper (ASTM B152 C10100) with a purity of 99.99 mass% or more is prepared, charged into a high-purity graphite crucible, and placed in a _N gas atmosphere. Melted using an electric furnace. Various additive elements were added to the molten copper alloy to produce a molten alloy having the composition shown in Table 1, and the alloy was poured into a carbon mold to produce an ingot. The size of the ingot was about 40 mm thick×about 70 mm wide×about 100 mm long.
Subsequently, each ingot was subjected to water quenching after being held at the temperature shown in Table 2 for a predetermined time in an N ₂ gas atmosphere as a homogenization treatment.

Next, hot rolling was performed. Reheating is performed so that the hot rolling start temperature is the temperature shown in Table 2, and the width direction of the ingot is aligned with the rolling direction, and the rolling end temperature is set to 600 ° C. or higher while reheating as appropriate. I made it so that After completion of hot rolling, water quenching was performed, and after cutting and surface grinding, a hot rolled material having a thickness of about 20 mm, a width of about 160 mm, and a length of about 100 mm was produced.

After that, rough plastic working and solution heat treatment were performed.
Specifically, after performing cold rolling at a rolling reduction of about 20% or more, solution heat treatment was performed at the temperature shown in Table 2 for a predetermined period of time between 1 hour and 4 hours, followed by water quenching.
After solution heat treatment, cutting and surface grinding were performed, cold working was performed at a rolling reduction of 70% or more, and intermediate heat treatment was performed at the 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 layer. Also, the crystal grain size was measured from the samples after the intermediate heat treatment, and it was confirmed that the average grain size was within the range of 3 to 10 μm in all the inventive examples and comparative examples.

The average crystal grain size after the intermediate heat treatment was examined as follows.
The surface perpendicular to the width direction of rolling, that is, the TD (Transverse Direction) surface is used as an observation surface, mirror-polished and etched, and then photographed with an optical microscope so that the rolling direction is horizontal in the photograph. Observation was performed with a 1000-fold field of view (approximately 300×200 μm ² ). Then, according to the cutting method of JIS H 0501, the grain size is determined by drawing five vertical and horizontal line segments each of a predetermined length in the photograph, counting the number of completely cut grains, and calculating the average value of the cut length. It was calculated as the average crystal grain size.

After that, finish rolling was performed at the rolling rate shown in Table 2.
Finally, after performing a finish heat treatment at the temperature shown in Table 2 for 1 minute to 4 hours, water quenching, cutting and surface polishing, the strip for characteristic evaluation having a thickness of 0.25 mm and a width of about 160 mm was applied. produced.
At this time, the hardness Hv_CR of the rolled surface before the finish heat treatment, that is, the ND surface (Normal Direction) and the hardness Hv_HT of the ND surface after the finish heat treatment were measured, and the hardness difference ΔHv=Hv_CR−Hv_HT was calculated. The Vickers hardness was measured under a test load of 1.96 N (=0.2 kgf) or 0.98 N (=0.1 kgf) according to the microhardness test method specified in JIS-Z2248. Table 2 shows the hardness difference ΔHv.

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

〔aspect ratio〕
With the surface orthogonal to the width direction of rolling, that is, the TD surface (transverse direction) as the observation surface, mechanical polishing was performed using water-resistant abrasive paper and diamond abrasive grains, and then final polishing was performed using a colloidal silica solution. rice field. Then, an EBSD measurement device (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX/TSL (currently AMETEK)) and analysis software (manufactured by EDAX/TSL (currently AMETEK) OIM Data Analysis ver.7.3 According to .1), each crystal grain (including twins) except for measurement points with a CI value of 0.1 or less at an electron beam acceleration voltage of 20 kV, a measurement area of ²⁰⁰ μm or more at a measurement interval of 0.03 μm step When the orientation difference is analyzed and the measurement points where the orientation difference between adjacent measurement points is 15 ° or more is defined as the grain boundary, 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. In the measurement of the aspect ratio, the grain size on the 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 taken from the strip material for characteristic evaluation, and the electrical resistance was determined by the four-probe method. Also, the dimensions of the test piece were measured using a micrometer, and the volume of the test piece was calculated. Then, the electrical conductivity was calculated from the measured electrical resistance value and volume. The test piece was taken so that its longitudinal direction was parallel to the rolling direction of the strip for characteristic evaluation.

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

[Stress corrosion cracking resistance]
The stress corrosion cracking resistance is measured by D.I. H. It was investigated according to the stress corrosion cracking test method of THOMPSON (Materials, Res. and Stds. 1 (1961), P108-111). That is, a test piece with a width of 10 mm and a length of 60 mm was taken parallel to the rolling direction, and the center part in the length direction was bent with a radius of curvature R: 2 mm. After holding it at room temperature for 24 hours, after removing the constraint, the initial amount of displacement δ ₀ was measured, both ends were constrained again, and this was placed in a volume of 10 L in which 1 L of about 5% ammonia water was stored. desiccator, place the test piece restrained in a loop shape in the gas phase, hold at 25 ° C., and after 96 hours when the Zn content is 7 mass% or more and 15 mass% or less, the Zn content is 15 mass% When the content was more than 36.5 mass% and less than 36.5 mass%, after 24 hours, the loop _- shaped restraint was released and the displacement δ1 of the test piece was measured. Using the measured initial displacement _δ0 and displacement δ1, the residual stress _ratio (%) was calculated from the following equation.
Residual stress rate (%) = ( ₁ -δ1/δ0) _x 100
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%.

[Bendability]
Bending was performed according to four test methods of JCBA (Japan Copper and Brass Association Technical Standard) T307-2007. W-bent so that the bending axis is perpendicular to the rolling direction. A plurality of test pieces of width 10 mm × length 30 mm × thickness 0.25 mm were taken from the strip for characteristic evaluation, and a W-shaped jig with 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 in which the ratio of radii R (R/t) was 1.
A cracking test was performed on each of the three samples, and the samples in which cracks were not observed in the four fields of view of each sample were evaluated as "○", and those in which cracks were observed in one or more fields of view were evaluated as "×".

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 grains with 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, Inventive Examples 1-18 were excellent in stress corrosion cracking resistance and bending workability. Moreover, it was excellent also in electrical conductivity and yield strength.
From the above, it was confirmed that, according to the examples of the present invention, it is possible to provide a copper alloy for electronic and electrical devices that is reliably and sufficiently excellent in stress corrosion cracking resistance and excellent in bending workability. rice field.

Claims (10)

Zn is contained in a range of more than 7 mass% and less than 36.5 mass%, the balance is Cu and unavoidable impurities, and the S content is less than 20 mass ppm,
Using the surface perpendicular to the width direction of the rolling as an observation surface, the mother phase containing Cu and Zn is measured by the EBSD method in a measurement area of 200 μm ² or more at a measurement interval of 0.03 μm step, and data analysis software OIM When the analysis was performed excluding the measurement points where the CI value analyzed by the method was 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 twins) was 0.1. The area ratio of the crystal grains that is 1 or less is 40% or more of the entire measured area in terms of Area fraction,
A copper alloy for electronic and electrical devices, characterized by having a 0.2% proof stress of 300 MPa or more and less than 650 MPa. 2. The copper alloy for electronic and electrical devices according to claim 1, further comprising either one or two of Sn and Ni, wherein the total content of Sn and Ni is 5 mass % or less. Furthermore, 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. Cracks do not occur even when a W-bending test is performed using a W-shaped jig in which the ratio of the plate thickness t to the bending radius R (R/t) is 1. The copper alloy for electronic and electrical devices according to any one of the items. An electronic device comprising a rolled material of the copper alloy for electronic and electrical devices according to any one of claims 1 to 4 and having a thickness in the range of 0.05 mm or more and 1.0 mm or less. Copper alloy sheet for electrical equipment. In the copper alloy sheet for electronic and electrical equipment according to claim 5,
A copper alloy sheet for electronic/electrical equipment, characterized by having a metal-plated surface. 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 equipment according to any one of claims 1 to 4. 7. 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 equipment according to claim 5 or 6.

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