JP5557761B2 - Cu-Ni-Si based copper alloy with excellent bending workability and stress relaxation resistance - Google Patents

Description

  The present invention is for electrical and electronic parts used for electrical and electronic parts such as terminals, connectors, and relays, semiconductor materials (lead frames, heat sinks), electrical circuit materials (junction blocks for automobiles, circuits for consumer electrical parts), etc. It relates to a copper alloy plate.

In the automotive field, many electrical and electronic parts have been installed to comply with environmental regulations, comfort and safety, and the terminals, connectors and relay parts used have been narrowed and miniaturized. . There are similar requirements in the field of information communications and consumer products. Cu-Ni-Si alloys, which can obtain high strength by precipitation hardening, are widely used in these applications as alloys having high strength, high heat resistance, high stress relaxation properties and relatively high electrical conductivity. It has been.
On the other hand, with the miniaturization of electrical and electronic parts, copper alloy plates for electrical and electronic parts are required to have excellent bending workability to withstand bending bending or 90 ° bending after notching as well as high strength and high conductivity. A lot is happening. Furthermore, along with the miniaturization of electrical and electronic parts, conventionally, strict bending work is usually performed with a bend line perpendicular to the rolling direction (so-called GW). The number of cases that are performed (so-called BW) is also increasing.

  Patent Documents 1 to 4 disclose means for improving bending workability or stress relaxation characteristics of Cu—Ni—Si based copper alloys. Patent Documents 1 and 2 disclose methods for improving the bending workability by controlling the crystal grain size of a Cu—Ni—Si based copper alloy. Similarly, Patent Document 3 discloses a method for improving stress relaxation resistance by controlling additive elements of a Cu-Ni-Si copper alloy, and Patent Document 4 discloses a method for improving bending workability by controlling crystal grain size. Has been.

JP 2008-196042 A JP 2008-266783 A Japanese Patent No. 4287878 JP-A-11-335756

As shown in Patent Documents 1 to 4, in a Cu-Ni-Si based copper alloy, conventional bending workability improvement is mainly performed by controlling the crystal grain state, and improvement of stress relaxation resistance is mainly controlled by additive elements. Has been done by. However, the improvement in bending workability due to grain refinement, on the other hand, leads to a decrease in stress relaxation resistance, and the improvement in stress relaxation resistance due to additive elements leads to a decrease in bending workability. is there.
Therefore, the technical problem to be solved by the present invention is an electrical and electronic device having both excellent bending workability and stress relaxation resistance in a Cu-Ni-Si based copper alloy capable of obtaining high strength by precipitation hardening. It is to provide a copper alloy sheet for parts.

As a result of various studies on the influence of the structure of the Cu-Ni-Si-based copper alloy sheet on the bending workability and stress relaxation resistance, the present inventors have mixed fine crystal grains and coarse crystal grains. Has been found to be able to have both excellent bending workability and stress relaxation resistance, and has arrived at the present invention based on that knowledge.
The copper alloy sheet for electric and electronic parts excellent in bending workability and stress relaxation resistance according to the present invention has Ni of 1.5 to 4.5 mass% and a mass ratio of Ni / Si of 4.0 to 5.0. A Cu-Ni-Si-based copper alloy sheet containing 0.01 to 1.3 mass% of Si and Sn with the balance being copper and inevitable impurities, and in a cross-section composed of a rolling direction and a plate thickness direction, is parallel to the rolling direction. The average crystal grain size in the direction is 5 to 20 μm, the maximum crystal grain size is 30 μm or more, and the minimum crystal grain size is 5 μm or less.

  In addition to Ni, Si, and Sn, the Cu-Ni-Si-based alloy includes (1) Mg: 0.005-0.2 mass%, Cr: 0.001-0.3 mass%, Mn: 0.01-0.5 mass%, Zn: one or more of 0.01-5.0 mass%, (2) B, C, P, Ca, V, Ga, Ge, Nb, Mo, Hf, One or two or more elements selected from the group consisting of Ta, Bi, and Pb are each element: 0.0001 to 0.1 mass%, and in the case of two or more elements, the total is 0.1% mass% or less, ( 3) One element or two or more elements selected from the group of Be, Al, Ti, Fe, Co, Zr, Ag, Cd, In, Sb, Te, and Au, each element: 0.001 to 0.9 mass %, In the case of 2 or more types, a total of 0.9 mass% or less can be contained. One or two or more of the above (1) to (3) can be appropriately combined. Furthermore, the content of S, which is an inevitable impurity, can be controlled to 0.005 mass% or less as necessary.

  The Cu-Ni-Si-based copper alloy plate according to the present invention has excellent bending workability and stress relaxation properties, and has strength characteristics and conductivity required as a copper alloy plate for electric and electronic parts. Yes.

It is a graph which shows the relationship between the work rate of the cold rolling after strain relief annealing, a stress relaxation rate, and a maximum crystal grain size.

Hereinafter, the composition and crystal grain form of the Cu—Ni—Si based copper alloy sheet according to the present invention and the manufacturing method will be specifically described.
[Composition of Cu-Ni-Si-based copper alloy sheet]
The basic composition of the Cu—Ni—Si based copper alloy sheet according to the present invention is substantially disclosed in Patent Document 1. It discloses similarly about subcomponents, such as Sn, Mg, Cr, Mn, Zn, and also other components, such as B-Pb and Be-Au.

・ Ni and Si
Ni and Si are elements that generate Ni ₂ Si precipitates in a Cu—Ni—Si based copper alloy plate and improve the strength of the alloy. The addition amount of Ni is 1.5 to 4.5 mass%, and the addition amount of Si is added in an amount corresponding to the addition amount of Ni so that the Ni / Si mass ratio is 4.0 to 5.0. If the amount of Ni added is less than 1.5 mass%, the strength is insufficient. When the amount of Ni added exceeds 4.5 mass%, Ni or Si crystallizes or precipitates during casting, resulting in a decrease in hot workability. Moreover, when the Ni / Si mass ratio is less than 4.0 and 5.0 or more, the conductivity is lowered due to the solid solution of Ni or Si that is excessive. The amount of Ni added is desirably 1.7 to 3.9 mass%.

・ Sn
Sn improves the strength characteristics and stress relaxation resistance characteristics by dissolving in the structure. For that purpose, it is necessary to add 0.01 mass% or more. On the other hand, when it exceeds 1.3 mass%, the electrical conductivity and the bending workability are lowered. Therefore, Sn content shall be 0.01-1.3 mass%. Desirably, it is 0.01 to 0.6 mass%, and more desirably 0.01 to 0.3 mass%.

・ Mg
Mg improves the strength characteristics by forming a solid solution in the structure. For that purpose, addition of 0.005 mass% or more is necessary. On the other hand, when it exceeds 0.2 mass%, bending workability and electrical conductivity will fall. Therefore, the Mg content is set to 0.005 to 0.2 mass%. Preferably it is 0.005-0.15 mass%, More preferably, it is 0.005-0.05 mass%.

・ Cr
Cr improves hot workability. For that purpose, addition of 0.001 mass% or more is necessary. On the other hand, if it exceeds 0.3 mass%, a crystallized product is generated and bending workability is lowered. Therefore, the Cr content is set to 0.001 to 0.3 mass%. Desirably, it is 0.001 to 0.1 mass%.
・ Mn
Mn improves hot workability. For that purpose, addition of 0.01 mass% or more is necessary. On the other hand, if it exceeds 0.5 mass%, the electrical conductivity decreases. Accordingly, the Mn content is set to 0.01 to 0.5 mass%. Desirably, it is 0.01-0.3 mass%.

・ Zn
Zn improves Sn plating peelability. For that purpose, addition of 0.01 mass% or more is necessary. On the other hand, if it exceeds 5 mass%, the electrical conductivity decreases. Therefore, the Mn content is set to 0.01 to 5 mass%. Desirably, it is 0.01-2 mass%, More desirably, it is 0.01-1.2 mass%.
・ S
S forms a compound with another solid solution element, thereby lowering the bending workability and lowering the stress relaxation characteristics. Therefore, the S content is preferably 0.005 mass% or less, and more preferably 0.002 mass% or less.

Other additive elements Each element of B, C, P, Ca, V, Ga, Ge, Nb, Mo, Hf, Ta, Bi, and Pb has an effect of improving press punchability. If these elements are less than 0.0001 mass%, they are not effective, and if they exceed 0.1 mass%, the hot workability decreases. Each element of Be, Al, Ti, Fe, Co, Zr, Ag, Cd, In, Sb, Te, and Au has an action of improving press punchability. Moreover, strength characteristics are improved by coexistence with Ni ₂ Si precipitates. Ti and Zr have the effect of further improving hot workability. These elements are ineffective at less than 0.001 mass%, and hot and cold workability deteriorates when they exceed 0.9 mass%. Therefore, when adding the above elements, B, C, P, Ca, V, Ga, Ge, Nb, Mo, Hf, Ta, Bi, and Pb each element 0.0001 to 0.1 mass% (two or more kinds) In the case of adding 0.1 mass% or less in total, Be, Al, Ti, Fe, Co, Zr, Ag, Cd, In, Sb, Te, and Au, each element is 0.001 to 0.9 mass% (2 In the case of adding seeds or more, the total is 0.9 mass% or less), and the total of both is 1 mass% or less.

[Grain state]
As described above, the bending workability required for the terminal copper alloy is generally better as the average crystal grain size is smaller. This is because the grain boundary area decreases as the crystal grain size increases, and segregation of solid solution elements and stress concentration are likely to occur at the grain boundaries. On the other hand, the stress relaxation resistance required for the terminal copper alloy generally decreases as the crystal grain size decreases. This is thought to be because the crystal grain boundary promotes the disappearance and movement of dislocations existing in the structure.
In order to have both the above-mentioned bending workability and stress relaxation resistance, there are mainly fine grains that suppress intergranular cracking in copper alloys, and there are some coarse grains that improve stress relaxation resistance. It is effective to make it. Specifically, in the cross-sectional structure composed of the rolling direction and the plate thickness direction of the copper alloy, the average crystal grain size may be 5 to 20 μm, the maximum crystal grain size is 30 μm or more, and the minimum crystal grain size is 5 μm or less.

When the maximum crystal grain size is small, good stress relaxation characteristics cannot be obtained. When the minimum crystal grain size is large, bending workability decreases. The maximum crystal grain size is desirably 35 μm or more, and more desirably 40 μm or more. In the manufacturing method described later, about 80 μm is the upper limit for manufacturing. The minimum crystal grain size is desirably 4 μm or less, and more desirably 3 μm or less. In the manufacturing method described later, about 1 μm is the lower limit for manufacturing.
Further, the average crystal grain size is set to 5 to 20 μm in order to make coarse crystal grains and fine crystal grains in a good mixed state. When the average grain size is high, the bending workability is lowered, and when it is low, the stress relaxation property is lowered. Preferably it is 5-15 micrometers, More preferably, it is 5-10 micrometers.

[Production method]
In the Cu—Ni—Si based copper alloy plate of the composition of the present invention, the conventional standard manufacturing method (see, for example, Patent Document 4) is as follows: melting / casting → soaking treatment → hot rolling → rapid cooling after hot rolling → cooling Cold rolling → recrystallization treatment with solution treatment → cold rolling → precipitation treatment. In addition, a process performed in the order of precipitation treatment → cold rolling after recrystallization treatment with solution treatment is also effective for increasing the strength. In some cases, low-temperature annealing is finally performed in order to obtain better spring properties.
In order to obtain a Cu-Ni-Si based copper alloy sheet having a crystal grain structure defined in the present invention, performing strain relief annealing to remove dislocations during recrystallization treatment with hot rolling and solution treatment, Furthermore, the processing rate of the cold working before the recrystallization process accompanied by solution treatment is controlled to a predetermined value. That is, melting / casting → uniform heat treatment → hot rolling → rapid cooling after hot rolling → cold rolling → strain relief annealing → cold rolling → recrystallization with solution treatment → cold rolling → precipitation treatment.

The technical characteristic part of the manufacturing method is in a series of steps of recrystallization treatment with strain relief annealing → cold rolling → solution treatment. By performing recrystallization treatment (annealing) accompanied by solution treatment, the crystal structure defined in the present invention is almost completed (the grain size is slightly changed by subsequent cold working). Therefore, it is necessary to accumulate a strain corresponding to 5 to 35% in the cold working rate before recrystallization annealing accompanied by solution treatment. Is what you do.
Subsequently, each step will be described in more detail.

-Soaking, hot rolling and rapid cooling Soaking is carried out at 850 ° C or more for 10 minutes or more, followed by hot rolling. The cooling rate from the start of hot rolling to 700 ° C. is 20 ° C./min or more including during hot rolling. This is because when the cooling rate to 700 ° C. is slower than this, coarse precipitate particles are generated and the precipitation of fine precipitate particles having a strengthening action is inhibited. After the hot rolling is completed, it is quickly cooled by water cooling or the like to suppress the generation of precipitated particles.
-Cold rolling Cold rolling after hot rolling is performed appropriately in consideration of the final sheet thickness and the subsequent cold working rate. The rolling rate is arbitrary.

・ Strain relief annealing Strain relief annealing is performed in order to control the recrystallized structure after recrystallization with solution to an appropriate state. Optimum strain relief annealing conditions are affected by the Ni and Si contents in the copper alloy, and are lower when the Ni and Si contents are low, and higher when the Ni and Si contents are high. As a guide, it is preferable to select a condition in which the hardness after strain relief annealing is 75% or less of the hardness before annealing. Specifically, the annealing temperature is 500 to 750 ° C., and the annealing time is 20 to 20000 seconds. When the annealing temperature is low or the annealing time is short, a desired recrystallized structure cannot be obtained after a recrystallization process with subsequent solution treatment. When the annealing temperature is high or the annealing time is long, the energy consumption becomes excessive and the production cost increases.

-Cold rolling By applying a certain strain to the copper alloy plate before the recrystallization treatment with solution treatment, a copper alloy plate having a desired crystal structure is obtained after the recrystallization treatment with solution treatment. The cold working rate is 5 to 35%. When the cold working rate is low, the desired recrystallized structure cannot be obtained in both cases.

・ Recrystallization treatment with solution treatment The purpose of the recrystallization treatment with solution treatment is to form a recrystallized structure in which Ni and Si are dissolved in order to age-harden Ni-Si and bending workability is improved. It is to be. Optimal recrystallization treatment conditions are affected by the Ni and Si contents in the copper alloy, and the temperature is lower when the Ni and Si contents are low, and higher when the Ni and Si contents are high. Specifically, it is selected from the conditions of holding at 600 to 950 ° C., preferably 650 to 900 ° C. for 3 minutes or less. More specific heat treatment conditions are shown in the examples. If the recrystallization treatment conditions are lower or shorter than this, the solid solution amount of Ni and Si is reduced and the strength characteristics are lowered. When the annealing conditions are higher than this or for a long time, the recrystallized grains are coarse and uniform, and a desired recrystallized structure cannot be obtained.

・ Cold rolling Cold rolling after recrystallization treatment with solution treatment is performed at a processing rate of 50% or less. When the cold rolling processing rate exceeds 50%, as described in Patent Document 1, bending workability is deteriorated. This cold rolling introduces nucleation sites for precipitates.
Precipitation treatment The precipitation treatment is performed at 350 to 500 ° C. for 30 minutes to 24 hours. When the holding temperature is lower than 350 ° C., the precipitation of Ni ₂ Si becomes insufficient. When holding temperature exceeds 500 degreeC, the intensity | strength of a copper alloy plate will fall and a required intensity | strength characteristic will not be acquired. Further, if the holding time is less than 30 minutes, Ni ₂ Si is not sufficiently precipitated, and if it exceeds 24 hours, productivity is hindered.

  In the manufacturing method described above, cold rolling between hot rolling and strain relief annealing is repeatedly performed with heat treatment accompanied by softening, final cold rolling is performed after precipitation treatment, and finally low temperature annealing is performed. It can also be implemented. When cold rolling is performed after the precipitation treatment, the processing rate is preferably 50% or less in combination with the cold rolling processing rate before the precipitation treatment.

A Cu—Ni—Si based copper alloy having the composition shown in Table 1 was melted and cast in the kryptor furnace in the atmosphere and covered with charcoal. The ingot was subjected to soaking treatment under the condition of 950 ° C. × 1 hour, followed by hot rolling at 700 ° C. or more, followed by rapid water cooling to obtain a sample having a thickness of 20 mm.
Next, both sides of the plate are faced by 1 mm and then cold rolled, and under the conditions shown in Table 2, strain relief annealing, cold rolling, recrystallization treatment with solution treatment, and final cold rolling are performed. A copper alloy plate having a thickness of 0.2 mm was obtained. Subsequently, a precipitation treatment at 450 ° C. × 2 hours was performed.

Using test pieces cut out from each Cu-Ni-Si-based copper alloy plate, 0.2% proof stress measurement, electrical conductivity measurement, W bending test, crystal structure observation and measurement, and stress relaxation characteristic test by tensile test are as follows. I went there. The results are shown in Table 3.
-Tensile test Using a JIS No. 5 test piece with the rolling direction as the longitudinal direction, a tensile test based on JIS Z2241 was performed to obtain 0.2% yield strength. In this example, 0.2% proof stress was determined to be 550 N / mm ² or more.

-Conductivity measurement Using a test piece of width 10mm x length 300mm with the rolling direction as the longitudinal direction, in accordance with the nonferrous metal material conductivity measurement method shown in JIS H0505, the electrical resistance was measured by a double bridge type electrical resistance measurement device The conductivity was calculated by the average cross-sectional area method. In this example, the electrical conductivity was 35% IACS or higher.
W bending test In accordance with the W bending test shown in JCBA T307, D. (Parallel to the rolling direction) and T.W. D. Using a test piece having a width of 10 mm and a length of 30 mm with each direction (perpendicular to the rolling direction) as the longitudinal direction, a W-bending test was performed with a bending radius R = 0.05 mm. After the W-bending test, the surface of the outer side of the bending was observed using an optical microscope at a magnification of 50 times to determine the presence or absence of cracks. In the case where there was no crack, it was rated as ○ (pass), and in the case where there was a crack, it was marked as x (fail).

・ Measurement of average crystal grain size, maximum and minimum crystal grain size After obtaining a cross section (observation surface) consisting of rolling direction and plate thickness direction using cold embedding resin, 2400th water-resistant abrasive paper, 1 μm diamond spray Finish polishing was performed with a buff coated with. Further, an observation sample was obtained by corroding the grain boundary with chromic acid and ferric chloride. For tissue observation, a tissue photograph was obtained at a magnification of 400 times using an optical microscope. The average crystal grain size was measured by using a cutting method in a direction parallel to the rolling direction and setting the total cutting length to 1000 μm at the center of the plate thickness. Further, in the same measurement, the site with the longest distance between cuts was set as the maximum crystal grain size, and the site with the shortest distance between cuts was set as the minimum crystal grain size.

-Stress relaxation rate measurement test The stress relaxation measurement was performed using a cantilever beam method conforming to the Japan Electronic Materials Manufacturers Association standard EMAS01011. The test piece used was a strip having a width of 10 mm and a length of 60 mm with the direction perpendicular to the rolling direction as the longitudinal direction. Using the test piece, the span length was set from the following formula (1) so that the load stress was 80% of the 0.2% proof stress, and the test piece was fixed to the jig.
d = τ × l ² /(1.5×α×t) (1)
Where d: initial deflection displacement [mm], τ: load stress [N / mm ² ], l: span length [mm], α: deflection coefficient [N / mm ² ], t: plate thickness [mm] is there.
After heating the specimen at 150 ° C x 1000 hr with the test piece fixed to the jig, the load stress was unloaded from the jig, the deflection displacement [mm] after unloading was measured, and the stress relaxation rate from the following formula (2) Was measured.
SRR = 100 × (δ / d) (2)
However, SRR: Stress relaxation rate [%], δ: Deflection displacement after unloading [mm].
In this example, a stress relaxation rate of 15% or less was accepted.

No. of Tables 1-3. Examples 1 to 19 are examples in which the composition and process were changed within the technical scope of the present invention. No. As for the copper alloy plates 1 to 19, the crystal grain structure satisfies the provisions of the present invention, and is excellent in 0.2% proof stress, electrical conductivity, bending workability, and stress relaxation resistance.
On the other hand, no. 20 to 27 are comparative examples in which the composition deviates from the definition of the present invention.
No. No. 20 has a composition in which the amount of Ni and Si added is excessive, and cracks occurred during hot rolling, making it impossible to produce a test material.
No. 21 is a composition having a high Ni / Si ratio and a low electrical conductivity. Also, bending workability is not good. This is presumably because the work hardening rate increased due to an increase in the amount of Ni solid solution.

No. 22 is a composition having a low Ni / Si ratio and a low electrical conductivity. Also, bending workability is not good. This is no. It is presumed that the work hardening rate increased due to an increase in the amount of Si solid solution as in the case of No. 21.
No. 23 is a composition to which Sn is not added, and has low stress relaxation resistance.
No. 24 is a composition in which Sn is added excessively, and its electrical conductivity and bending workability are low.
No. 25 is a composition in which Mg is added excessively, and its electrical conductivity and bending workability are low.
No. No. 26 is a composition in which Zn is added excessively and has a low electrical conductivity.
No. 27 is a composition in which a large amount of S is present in the component, and the bending workability is low.

No. 28 to 37 are comparative examples in which the definition of the crystal structure deviates from the definition of the present invention.
No. Since 28 and 29 do not perform strain relief annealing, the maximum crystal grain size or the minimum crystal grain size does not satisfy the provisions of the present invention. No. with small maximum crystal grain size No. 28 cannot secure good stress relaxation resistance and has a large minimum crystal grain size. No. 29 has low bending workability.
No. 30 to 32 have a small maximum crystal grain size and low stress relaxation resistance.
No. In No. 33, the rolled structure remains, and the strength characteristics, bending workability, and stress relaxation resistance are deteriorated.
No. No. 34 has a large average crystal grain size and minimum crystal grain size and low bending workability.
No. 35 to 37 have a small maximum crystal grain size and low stress relaxation resistance.

FIG. 17-19 (Examples) and No. About 35-37 (comparative example), the horizontal axis shows the cold work rate [%], and the vertical axis shows the maximum crystal grain size [μm] and the stress relaxation rate [%]. No. 17-19 and no. 35-37 are the same in both composition and manufacturing process except the processing rate of cold rolling before recrystallization treatment with solution treatment.
As shown in FIG. 1, when the processing rate of cold rolling was changed in the range of 0 to 80%, the maximum crystal grain size was determined as Example No. with processing rates of 10, 20, and 30%. It is large at 17 to 19, satisfying the definition of the present invention, and the stress relaxation rate is improved accordingly. Note that the smaller the value of the stress relaxation rate, the better the characteristics.
No. 15, 16 (Examples) and No. 31 and 32 (comparative example) are the same in composition and manufacturing process except for the cold rolling processing rate before recrystallization treatment with solution treatment, but the same tendency appears here.

Claims (7)

Ni containing 1.5 to 4.5 mass%, Ni / Si mass ratio of 4.0 to 5.0, Si and Sn containing 0.01 to 1.3 mass%, with the balance being copper and inevitable impurities It is a Cu-Ni-Si based copper alloy plate, and in the cross section composed of the rolling direction and the plate thickness direction, the average crystal grain size in the direction parallel to the rolling direction is 5-20 μm, the maximum crystal grain size is 30 μm or more, and the minimum crystal grain size A copper alloy plate for electric and electronic parts having excellent stress relaxation resistance and bending workability, characterized by being 5 μm or less. The copper alloy plate for electrical and electronic parts excellent in stress relaxation resistance and bending workability according to claim 1, further comprising 0.005 to 0.2 mass% of Mg. Furthermore, 0.001-0.3 mass% of Cr or / and 0.01-0.5 mass% of Mn are included, It is excellent in the stress relaxation resistance and bending workability described in Claim 1 or 2 characterized by the above-mentioned. Copper alloy sheet for electrical and electronic parts. Furthermore, 0.01-5.0 mass% of Zn is contained, The copper alloy plate for electrical and electronic components excellent in the stress relaxation resistance and bending workability as described in any one of Claims 1-3 characterized by the above-mentioned. 5. The copper alloy plate for electrical and electronic parts excellent in stress relaxation resistance and bending workability according to any one of claims 1 to 4, wherein the S content is 0.005 mass% or less. Further, one or more elements selected from the group consisting of B, C, P, Ca, V, Ga, Ge, Nb, Mo, Hf, Ta, Bi, and Pb are used as each element: 0.0001 to The electrical and electronic component excellent in stress relaxation resistance and bending workability according to any one of claims 1 to 5, characterized by containing 0.1 mass% or less in total in the case of 2 mass% or less. Copper alloy plate. Furthermore, one or two or more elements selected from the group consisting of Be, Al, Ti, Fe, Co, Zr, Ag, Cd, In, Sb, Te, and Au are used. 9 mass%, in the case of 2 or more types, a total of 0.9 mass% or less is contained, The copper for electrical and electronic parts excellent in stress relaxation resistance and bending workability according to any one of claims 1 to 6 Alloy plate.

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