COPPER ALLOY FOR ELECTRICAL/ELECTRONIC DEVICE AND METHOD FOR PRODUCING THE SAME

Abstract

A copper alloy for an electrical and electronic device in accordance with the present invention is characterized in that the copper alloy for an electrical and electronic device includes: nickel (Ni) between 1.5 mass % and 5.0 mass %; silicon (Si) between 0.4 mass % and 1.5 mass %; and a remaining portion formed of Cu and an unavoidable impurity, wherein a mass ratio between Nickel (Ni) and Silicon (Si) as Ni/Si is not smaller than two and not larger than seven, an average crystalline grain diameter is not smaller than 2 μm and not larger than 20 μm, and a standard deviation of the crystalline grain diameter is not larger than 10 μm.

Description

TECHNICAL FIELD

The present invention relates to a copper alloy of a Cu—Ni—Si system for an electrical and electronic device, and to a method for producing the same. The copper alloy is suitable for a lead frame of an electrical and electronic device, a connector, a terminal, a relay, a switch, or the like.

BACKGROUND ART

Conventionally, there has been widely used a copper-based material with superior electrical and thermal conductivity such as phosphor bronze, red brass, brass, a Corson alloy, or the like for an electrical and electronic device. It has been required for a material to be applied to have further improved a strength, an electrical conductivity, an yield stress relaxation characteristic, a bending workability, a plating ability, a pressing workability, a heat resisting property, or the like, in accordance with a smaller size of an electrical and electronic device or a lighter weight in recent years. However, it is difficult to concurrently improve properties such as the strength and the bending workability or the strength and the electrical conductivity.

The Corson alloy is an alloy of a Cu—Ni—Si system that has a higher strength due to a precipitation of elements such as Ni and Si. With the alloy, it is able to satisfy characteristics required for an electrical and electronic device. However, the Corson alloy has insufficient bending workability under a severe condition in which properties concurrently need to be improved.

For instance, as a copper alloy with improved bending workability, there is proposed a substance that contains Ni between 2 and 4% (by mass), Si between 0.5 mass % and 1.0 mass %, Zn between 0.1 mass % and 1.0 mass %, Al, Mn, Cr, or the like, sulfur not more than 0.002 mass %, and a remaining portion comprised of Cu and an unavoidable impurity. A size of a precipitate is not bigger than 10 nm, and a distribution density of the precipitate is not lower than 1×10⁵ pieces per μm³, and a hardness Hv is not softer than 220 (refer to Japanese Patent Application Publication No. 06-184680). However, it is not able to obtain sufficient bending workability.

Moreover, there is proposed a copper alloy plate material that contains Ni between 4.0 mass % and 5.0 mass %, Si within a range for a ratio of Ni/Si between four and five, and a remaining portion formed of Cu and an unavoidable impurity. An average grain diameter of an Ni₂Si precipitate of the alloy plate material is between 3 nm and 10 nm, and an average space of Ni₂Si precipitate is not more than 25 nm after an accelerated aging and hardening (refer to Japanese Patent Application Publication No. 2005-089843 for instance). The alloy exhibits improved tensile strength and electrical conductivity.

Further, there is known a copper alloy that contains Ni between 0.4 mass % and 4.8 mass %, Si between 0.1 mass % and 1.2 mass %, Mg or the like approximately 0.3 mass %, and a remaining portion formed of Cu and an unavoidable impurity. An average crystalline grain diameter is not larger than 1 μm, and crystalline grains with a grain diameters smaller than 3 μm occupy an area not smaller than 90% (refer to Japanese Patent Application Publication No. 2006-089763). The copper alloy has improved tensile strength, electrical conductivity and workability.

Furthermore, Japanese Patent Application Publications No. 06-184680, No. 2005-089843 and No. 2006-089763 have disclosed a Corson alloy in which crystalline grains are minimized in order to improve strength. However, it has not been able to improve the electrical conductivity and the bending workability at the same time.

DISCLOSURE OF THE INVENTION

In view of the problems mentioned above, the present inventors have examined relations between components and compositions of a copper alloy, an average crystalline grain diameter, a standard deviation of a crystalline grain diameter, bending workability, or the like. As a result, it is found out that it becomes able to improve the bending workability without deteriorating strength and electrical conductivity by properly designing the relations. Moreover, further examinations are progressed with based on the findings, and the present invention is completed.

According to the present invention, it becomes able to provide a copper alloy for an electrical and electronic device and a method for producing the same as defined below.

1. According to a first aspect of the present invention, a copper alloy for an electrical and electronic device includes: Ni between 1.5 mass % and 5.0 mass %; Si between 0.4 mass % and 1.5 mass %; and a remaining portion formed of Cu and an unavoidable impurity, wherein a mass ratio of Ni/Si is not smaller than two and not larger than seven, an average crystalline grain diameter is not smaller than 2 μm and not larger than 20 μm, and a standard deviation of the crystalline grain diameter is not larger than 10 μm.

2. According to a second aspect of the present invention, in the copper alloy for the electrical and electronic device in the first aspect, the average crystalline grain diameter is within a range not larger than 15 μm, and the standard deviation of the crystalline grain diameter is not larger than 8 μm.

3. According to a third aspect of the present invention, in the copper alloy for the electrical and electronic device in the first aspect, the average crystalline grain diameter is within a range not larger than 10 μm, and the standard deviation of the crystalline grain diameter is not larger than 5 μm.

4. According to a fourth aspect of the present invention, the copper alloy for the electrical and electronic device in one of the first to the third aspects further includes at least one element between 0.005 mass % and 2.0 mass %, that is selected from a group of Mg, Sn and Zn, and a remaining portion formed of Cu and an unavoidable impurity.

5. According to a fifth aspect of the present invention, the copper alloy for the electrical and electronic device in one of the first to the fourth aspects further includes at least one element between 0.005 mass % and 2.0 mass %, that is selected from a group of Ag, Co, Cr, Fe, Mn, P, Ti and Zr, and a remaining portion formed of Cu and an unavoidable impurity.

6. According to a sixth aspect of the present invention, a method for producing a copper alloy for an electrical and electronic device comprises at least the following steps of: casting a copper alloy which includes: Ni between 1.5 mass % and 5.0 mass %; Si between 0.4 mass % and 1.5 mass %; and a remaining portion formed of Cu and an unavoidable impurity, wherein a mass ratio of Ni/Si is not smaller than two and not larger than seven, and performing thereafter a hot working and then performing a cold working (Step a); performing a process of a re-crystallization heat treatment after performing the above defined Step a, with a temperature rising rate of not slower than 10° C. per second, to an end point temperature between 700° C. and 950° C., with a retention time between five seconds and 300 seconds, and with a cooling rate till 300° C. as not slower than 20° C. per second (Step b); and performing a process of an aging precipitation after performing the above defined Step b (Process C).

In the present invention, the average crystalline grain diameter means an average value of the grain diameter of the individual crystals that exist in the texture of the copper alloy after the process to be solution heated and then to be recrystallized. Moreover, the standard deviation of the crystalline grain diameter means a value that is evaluated with based on the individual crystalline grain diameters. Further, the texture of the metal has a state obtained by performing the process of treating with heat (the process to be recrystallized), or by performing the processes of treating with heat, of aging, of annealing, or the like. It is able to observe the individual states by an optical microscope (OM), a scanning electron microscope (SEM), or the like.

The aspects and advantages in accordance with the present invention will be further clarified by the following description.

BEST MODE FOR CARRYING OUT THE INVENTION

In the copper alloy in accordance with the present invention there becomes to be improved in particular the bending workability by specifying properly the average crystalline grain diameter of the copper alloy of Cu—Ni—Si system and the standard deviation of the crystalline grains. And hence the alloy becomes useful for the application to an electrical and electronic device. Next, the functions in accordance with the component elements, the advantages and each of the contents that comprise the copper alloy for an electrical and electronic device in accordance with the present invention will be described in detail below.

Ni and Si contribute to an improvement of the strength by being precipitated as a chemical compound of Ni—Si. The reason that such Ni is designed to be specified between 1.5 mass % and 5.0 mass % and that Si is designed to be specified between 0.4 mass % and 1.5 mass % is that it is not able to obtain the strength as sufficiently if ether one is lower than each of the lower limits, respectively, or that the strength becomes to be saturated if ether one is higher than each of the upper limits respectively, and also that the electrical conductivity becomes to be decreased either. Moreover, a balance between the strength and the electrical conductivity becomes to be worsened drastically in a case where the ratio of Ni/Si is not within the range between two and seven. The substance is not applicable to an alloy for an electrical and electronic device that is required to have a strength as higher and an electrical conductivity as higher as well.

Further, regarding the copper alloy in accordance with the present invention it becomes able to improve a material property by being contained at least any one nature of the elements that is selected from Mg, Sn and Zn in addition to the above mentioned alloy contents. For example in a case of adding Mg, the same contributes to an improvement of the stress relaxation characteristic. Sn contributes to an improvement of the stress relaxation characteristic and an enhancement of the strength as well in a case of adding the same. Meanwhile, Zn contributes to an improvement of a plating wettability thereon in a case of adding the same. On the contrary thereto in a case where each of the contents of the elements is excessively lower, it is not able to obtain each of the advantages. Still further, in a case where each of the contents is excessively higher, such as regarding the Mg there becomes to be increased an amount of oxides at a period of a process of casting, and then it becomes more difficult to perform the process of casting. Still further, regarding Sn, there becomes to be a cause to occur a crack at a period of a process of hot working, due to segregation at a period of the process of casting. Still further, regarding Zn, it is not able to predict any further improvement of the plating adherence thereon. Furthermore, any one of the sample substance is not desirable due to an occurrence of a drastic decreasing of the individual electrical conductivities respectively. Here regarding the copper alloy in accordance with the present invention, it is able to produce simply by selecting properly such as a condition of a process of a hot rolling, a condition of a process of a cold rolling, a condition of a process of a treating with heat to be recrystallized, a condition of a process of a treating with heat for aging, a condition of a final rolling, or the like.

Moreover, it becomes able to further improve the material property by being contained as preferably at least any one nature of the elements that is selected from a group of Ag, Co, Cr, Fe, Mn, P, Ti and Zr in addition to the above mentioned alloy contents in the above mentioned alloy. For example in a case of adding any one of Ag, Co and Cr, each of the elements contributes to an improvement of the bending workability and the strength, due to an effect of suppressing the grain diameters from becoming rougher and larger at a period of a process of treating with heat to be crystallized, because of being formed a chemical compound. While, any one of Fe, Ti and Zr contributes to an improvement of the strength in a case of adding each of the same, because of being formed a chemical compound. Meanwhile, phosphorus contributes to suppress an amount of any of oxides at a period of a process of casting in a case of adding the same. Further, Mn contributes to an improvement of the workability of a hot working in a case of adding the same. On the contrary thereto in a case where each of the contents of the elements is excessively lower, it is not able to obtain each of the advantages. Still further, in a case where each of the contents is excessively higher, regarding Ag, there becomes to bring about a problem from a point of view of manufacturing cost on the production. Still further, regarding Co, it is not able to predict any further improvement of the material property, due to the further difficulty of performing the process of treating with heat as sufficiently in order to solution heat the same. Still further, Cr gives rise to a saturation of the effect of suppressing the crystalline grain diameter from rougher and larger. Still further, Fe gives rise to a decrease of the electrical conductivity. Still further, one of Ti and Zr gives rise to a further difficulty of casting, or the same becomes a cause for a crack to be occurred at the period of the process of hot working, due to an amount of any of oxides as excessively larger at a period of a process of casting. Still further, Mn gives rise to a decrease of the electrical conductivity either. Still further, phosphorus gives rise to a deterioration of the bending workability due to an increase of the precipitate. Furthermore, any one of the sample substances is not desirable due to an occurrence of a drastic decreasing of the individual electrical conductivities respectively. Here regarding the copper alloy in accordance with the present invention, it is able to produce simply by selecting properly such as a condition of a process of a hot rolling, a condition of a process of a cold rolling, a condition of a process of a treating with heat to be recrystallized, a condition of a process of a treating with heat for aging, a condition of a final rolling, or the like.

Next, regarding a method for producing the copper alloy for an electrical device and an electronic device that have the average crystalline grain diameter and the standard deviation of the crystalline grain diameter, a preferred embodiment will be described in detail below.

Here regarding a method for producing the copper alloy in accordance with the present embodiment, it is desirable to comprise the above defined Step a, Step b and Process C, and it is further preferable in particular to make use of the following processes from (1) to (10) in order.

(1) Process of casting a copper alloy which includes: Ni between 1.5 mass % and 5.0 mass %; Si between 0.4 mass % and 1.5 mass %; and a remaining portion formed of Cu and an unavoidable impurity, wherein a mass ratio between Ni and Si as Ni/Si is not smaller than two and not larger than seven.

(2) Process of performing a hot working and then of performing a cold working.

(3) Process of treating with heat to be recrystallized;

(3-1) Temperature rising rate: it is desirable to design the temperature rising rate as not slower than 10° C. per second to an end point temperature, or it is further preferable to be designed as not slower than 10° C. per second but not faster than 100° C. per second.

(3-2) End point temperature: it is desirable to be designed between 700° C. and 950° C.

(3-3) Retention time: it is desirable to be designed for between five seconds and 300 seconds.

(3-4) Cooling rate: it is desirable to be designed as not slower than 20° C. per second till 300° C. for instance, or it is further preferable to be designed as not slower than 20° C. per second but not faster than 200° C. per second.

(4) Process of aging precipitation:

(4-1) Condition of temperature rising: it is desirable for an end point temperature to be between 300° C. and 600° C., for an amount of time for treating to be between 0.5 hour and ten hours, for a temperature rising rate at the period to be as within a range between 2° C. and 25° C. per minute from a room temperature till reaching to the maximum temperature.

(4-2) Condition of cooling: it is desirable at the period of falling the temperature to be performed within a range between 1 and 2° C. per minute for the temperature as not lower than 300° C. at an inside of a furnace.

(5) Process of annealing for reducing distortion: it is desirable to perform a heating with a temperature at between 250° C. and 400° C. and with an amount of time for between 0.5 hour and five hours, or it is desirable to perform a heating with a temperature at between 600° C. and 800° C. and with an amount of time for between five seconds and 60 seconds as well.

Thus, it becomes able to obtain as efficiently the copper alloy that has the above desirable properties. Furthermore, it is further preferable to install a process for performing a cold working into between the above mentioned Process (4) and Process (5), that has a rate of rolling as not higher than 30% (including zero percent).

Next, an average crystalline grain diameter of the copper alloy in accordance with the present invention and a standard deviation of the crystalline grain diameter will be described in detail below. Here regarding the copper alloy in accordance with the present invention, the average crystalline grain diameter is designed to be as not smaller than 2 μm and not larger than 20 μm. And, it is desirable to be as not larger than 15 μm, or it is further preferable to be as not larger than 10 μm. Here in a case where the average crystalline grain diameter is excessively smaller, there is observed a remaining of the texture to be worked at the last process, and then thereby there may be occurred a deterioration of bending workability as drastically. Moreover, in a case where the average crystalline grain diameter is excessively larger on the contrary thereto, there becomes easier to be occurred a crack thereon at a period of bending work, and then thereby there becomes to be occurred a deterioration of bending workability. Here the standard deviation of the average crystalline grain diameter is designed to be as not larger than 10 μm. On the contrary thereto in a case where the deviation is excessively larger, there becomes to be a state where the grains individually having the larger grain diameters and the grains individually having the smaller grain diameters are coexisting together. And then in a case where any one of the grains individually having the larger grain diameters exists at around a top of the bended part, there may be occurred a crack on a bended surface, or there may be occurred a peeling of the plating off from a part at around a corrugation as largely wrinkled that may be created at around the grain having the larger grain diameter at a period of bending.

Thus, the copper alloy for an electrical and electronic device in accordance with the present invention becomes to be superior in the strength, the electrical conductivity and in the processing characteristics for the bending in particular. And then it becomes able to apply the same as preferred to the usage for the electrical device and for the electronic device, such as a lead frame, a connector, a terminal, a relay, a switch, or the like. Moreover, by making use of the method for producing the same in accordance with the present invention, it becomes able to produce further efficiently the above mentioned copper alloy for an electrical and electronic device that has the above mentioned superior properties. Furthermore, it becomes able to apply the method as preferred to a mass production as well.

EXAMPLES

Next, the present invention will be described in further detail below, in reference to the following examples, however, the present invention will not be limited to any one of the examples.

Example 1

There is performed an ingot of the copper alloys that individually have the compositions as shown in the following Table 1, and then there is obtained each of the ingots that are casted and individually have a dimension of 110 mm by 160 mm by 30 mm. Moreover, for each of the ingots there are performed the following processes of: maintaining at a temperature of 1000° C. with an amount of time of 30 minutes approximately; performing a work thereon by making use of a hot rolling till obtaining the thickness to be as 12 mm from the initial thickness of 30 mm; performing a quenching rapidly by a water cooling; facing to become approximately 10 mm for the thickness in order to remove a surface oxide film layer; and performing a cold rolling to obtain the thickness of 0.15 mm, 0.20 mm or 0.25 mm as corresponding properly to each of the testing requirements respectively. And hence there are assumed each of the substances as an intermediate sample.

And then for each of the above mentioned intermediate samples there are performed the following processes of: performing a treatment with heat to be recrystallized at each of the temperature as shown in Table 2 with maintaining the individual temperatures for between five seconds and 300 seconds; and then performing a cooling rapidly by making use of the water cooling or by an oil cooling. Moreover, there is designed for a temperature rising rate from a room temperature till reaching to the maximum temperature to be within a range of not slower than 10° C. per second. Further, there is designed for a cooling rate to be within a range of not slower than 20° C. per second for the temperature as not lower than 300° C.

And then thereafter for each of the above mentioned samples of copper alloy there are performed the following processes of: removing a surface oxide film layer; performing a cold rolling as not more than 30% (including zero percent) as required respectively; and then performing a treatment with heat to be aging precipitated at a temperature between 450° C. and 550° C. with an amount of time for 120 minutes approximately. Still further, there is designed for a temperature rising rate from a room temperature till reaching to the maximum temperature to be within a range between 2° C. per minute and 25° C. per minute. Still further, there is performed thereafter a cooling process with controlling a cooling rate to be within a range between 1° C. per minute and 2° C. per minute at an inside of a furnace for the temperature as not lower than 300° C. which influences a state of the precipitation. And then thereafter for each of the samples there are performed the following processes of: performing another cold rolling as not more than 30% (including zero percent); and then performing an annealing for reducing a distortion, by performing a heating with a temperature at between 250° C. and 400° C. and with an amount of time for between 0.5 hour and five hours, or by performing a heating with a temperature at between 600° C. and 800° C. and with an amount of time for between five seconds and 60 seconds.

Furthermore, there is performed each of the following characteristic evaluations regarding each of the copper alloy materials for an electrical and electronic device as the samples (samples of copper alloy) that are individually obtained in the above mentioned manner.

A. Electrical Conductivity:

There is performed a measurement of a specific resistance by making use of a four terminal method in a constant temperature bath which is maintained at 20° C. (±0.5° C.), and then thereby there is calculated the electrical conductivity. Moreover, there is assumed to be as 100 mm regarding a distance between each of the terminals.

B. 0.2% Yield Strength and Tensile Strength:

There is performed a measurement for the test pieces for the number five as pursuant to JIS 22201, with two pieces that are pursuant to JIS 22241, that are cut out in a direction as parallel to a rolling. And then there is calculated each of the average values respectively. Moreover, there is made use of the offset method regarding the 0.2% yield strength, meanwhile, there is evaluated regarding the tensile strength with making use of the numerical value for which the maximum tensile force is divided by an original cross sectional area.

C. Average Crystalline Grain Diameter and the Distribution Thereof (Standard Deviation):

At first there is performed a finishing for each of the test pieces to have individual mirror finished surfaces for individual cut faces thereon that are in a right angle to the rolling direction, by making use of a wet polishing and then by making use of a buffing. And then thereafter there is performed a corrosion on the polished surfaces for a several seconds with making use of a weak acid. Moreover, there is performed taking some photographs by making use of an optical microscope (OM) at a magnifying power between 50 times and 600 times and of a scanning electron microscope (SEM) at a magnifying power between 400 times and 5000 times. And hence there is performed a measurement for a grain diameter on the individual cut faces by making use of a crosscut method as pursuant to JIS H0501. And then thereby there becomes to be calculated an average grain diameter. Further, there is evaluated a standard deviation of the grain diameters by performing the measurement for each of the grain diameters as one by one. Still further, there is assumed a population parameter of the measurements as to be 200 in the case of evaluating the standard deviation of the grain diameters. Furthermore, there is performed a measurement of a grain diameter in a sample that is before performing the rolling (that corresponds to the time when the process of treating with heat to be recrystallized is finished) regarding the grain cannot help but become to be flat after performing the rolling in accordance with the above mentioned measurement of the grain diameters.

D. Evaluation of Bending Workability (R/t (GW), R/t (BW)):

At first there is performed removing of an oxide film layer on a surface of the individual samples after performing the above mentioned processes, that have individual board thickness (t) of approximately 0.25 millimeter and have individual board widths (w) of approximately ten millimeters. And then thereafter there is performed a bending for each to have individual angles at each inner side of the bending as ninety degrees respectively, for the samples with the bending in parallel to the rolling direction (a GW hereinafter), and for the other samples with the bending in a right angle to the rolling direction (a BW hereinafter). Moreover, there is performed an evaluation regarding the method of the evaluation of the bending by making use of a calculation of a ratio as R/t for which a bend radius as an R that is the minimal limit value of which there is not occurred any one of the above mentioned minute cracks thereon is divided by the board thickness (t). Further, there is performed a judgment regarding an observation to confirm whether or not there is any crack thereon, by making use of the OM at the magnifying power between 50 times and 600 times, or by making use of the SEM at the magnifying power between 400 times and 2000 times. When the value of R/t decreases, the bending workability is improved.

E. Adherence of the Plating Layer:

At first there is performed a plating of bright tin to have a thickness of approximately 1 μm on each of the test pieces that individually have the dimensions of 30 mm by 10 mm. And then thereafter there is performed a keeping warm of each of the test pieces in an atmosphere at a temperature of approximately 150° C. with an amount of time for 1000 hours. Moreover, there is performed thereafter a bending thereon with an angle to be 180 degrees and then the same is bended again to be an initial form respectively. Further, there is performed an observation by visually regarding a state of an adherence between the bended part and the plating of tin thereon. Furthermore, there is performed a further observation whether or not there is existed any peeling thereon by making use of the OM at the magnifying power between 50 times and 200 times as required. Here there is judged for a test piece that has an area ratio of peeling at the bending part as from zero percent but smaller than 10% to be assumed as EXCELLENT, or for a test piece that has the same as not smaller than 10% but smaller than 30% to be assumed as GOOD, or for a test piece that has the same as not smaller than 30% but smaller than 50% to be assumed as ACCEPTABLE, or for a test piece that has the same as not smaller than 50% to be assumed as NO GOOD.

F. Stress Relaxation Characteristic:

There is performed a measurement under the conditions that there is maintained each of the test pieces with an amount of time for 1000 hours in a constant temperature bath of 150° C. approximately, and that there is set a load stress for a surface maximum stress thereon to have a value as an 80% of each of the yield strengths respectively, by adopting a cantilever block method that is pursuant to the standard specification of Electronic Material Association of Japan (EMAS-3003).

Here regarding each of the results in accordance with the above mentioned measurements, there is shown in Table 1 for each of the alloy compositions regarding each of the intermediate samples, and there is shown in Table 2 through Table 4 for each of the results of the characteristic evaluations regarding each of the above mentioned alloy test pieces in accordance with the copper alloy samples.

TABLE 1
INTERMEDIATE	Ni	Si	Ag	Co	Cr	Fe	Mn	Mg	P	Sn	Ti	Zn	Zr
SAMPLES	mass %	Ni/Si
1	2.308	0.559	—	—	—	—	—	—	—	—	—	—	—	4.1
2	3.765	0.918	—	—	—	—	—	—	—	—	—	—	—	4.1
3	2.308	0.559	—	—	—	—	—	0.100	—	—	—	—	—	4.1
4	2.308	0.559	—	—	—	—	—	—	—	0.150	—	—	—	4.1
5	2.308	0.559	—	—	—	—	—	—	—	—	—	0.450	—	4.1
6	2.308	0.562	—	—	—	—	—	0.160	—	0.162	—	—	—	4.1
7	2.318	0.558	—	—	—	—	—	—	—	0.166	—	0.458	—	4.2
8	2.303	0.550	—	—	—	—	—	0.169	—	—	—	0.455	—	4.2
9	2.310	0.561	—	—	—	—	—	0.157	—	0.154	—	0.452	—	4.1
10	3.757	0.920	—	—	—	—	—	0.155	—	0.156	—	0.454	—	4.1
11	2.308	0.790	—	—	—	—	—	0.151	—	0.152	—	0.445	—	2.8
12	2.310	0.430	—	—	—	—	—	0.157	—	0.155	—	0.456	—	5.4
13	3.770	1.150	—	—	—	—	—	0.156	—	0.155	—	0.458	—	3.3
14	3.765	0.610	—	—	—	—	—	0.155	—	0.161	—	0.451	—	6.2
15	2.314	0.565	0.118	—	—	—	—	0.164	—	0.153	—	0.457	—	4.1
16	2.310	0.607	—	0.310	—	—	—	0.168	—	0.167	—	0.463	—	3.8
17	2.305	0.553	—	—	0.162	—	—	0.158	—	0.170	—	0.461	—	4.2
18	2.310	0.552	—	—	—	0.313	—	0.152	—	0.168	—	0.456	—	4.2
19	2.306	0.563	—	—	—	—	0.202	0.169	—	2.100	—	0.455	—	4.1
20	2.319	0.550	—	—	—	—	—	0.151	0.089	0.168	—	0.466	—	4.2
21	2.302	0.567	—	—	—	—	—	0.161	—	0.152	0.250	0.468	—	4.1
22	2.303	0.552	—	—	—	—	—	0.168	—	0.153	—	0.466	0.300	4.2
23	2.310	0.561	—	—	—	—	—	0.004	—	—	—	—	—	4.1
24	2.305	0.557	—	—	—	—	—	—	—	0.003	—	—	—	4.1
25	2.302	0.555	—	—	—	—	—	—	—	—	—	0.002	—	4.1
26	2.320	0.557	—	—	—	—	—	2.500	—	—	—	—	—	4.2
27	2.302	0.558	—	—	—	—	—	—	—	2.200	—	—	—	4.1
28	2.308	0.559	—	—	—	—	—	—	—	—	—	2.500	—	4.1
INTERMEDIATE	Ni	Si	Ag	Co	Cr	Fe	Mn	Mg	P	Sn	Ti	Zn	Zr
SAMPLES	mass %
29	1.210	0.313	—	—	—	—	—	—	—	—	—	—	—
30	6.000	1.500	—	—	—	—	—	—	—	—	—	—	—
31	2.311	0.310	—	—	—	—	—	0.161	—	0.152	—	0.451	—
32	2.303	1.300	—	—	—	—	—	0.164	—	0.152	—	0.457	—
33	1.100	0.575	—	—	—	—	—	0.163	—	0.153	—	0.461	—
34	5.085	0.580	—	—	—	—	—	0.161	—	0.159	—	0.458	—
35	3.750	0.520	—	—	—	—	—	0.161	—	0.152	—	0.451	—
36	3.768	1.950	—	—	—	—	—	0.161	—	0.159	—	0.458	—
37	2.314	0.570	0.002	—	—	—	—	0.164	—	0.153	—	0.457	—
38	2.310	0.600	—	0.003	—	—	—	0.168	—	0.167	—	0.463	—
39	2.311	0.566	—	—	0.001	—	—	0.164	—	0.151	—	0.454	—
40	2.311	0.540	—	—	—	0.001	—	0.165	—	0.163	—	0.467	—
41	2.311	0.575	—	—	—	—	0.001	0.168	—	0.169	—	0.463	—
42	2.305	0.614	—	—	—	—	—	0.168	0.001	0.151	—	0.488	—
43	2.319	0.559	—	—	—	—	—	0.152	—	0.151	0.002	0.477	—
44	2.320	0.573	—	—	—	—	—	0.154	—	0.155	—	0.455	0.001
45	2.323	0.561	2.825	—	—	—	—	0.163	—	0.169	—	0.468	—
46	2.250	0.614	—	3.001	—	—	—	0.160	—	0.168	—	0.466	—
47	2.307	0.562	—	—	2.406	—	—	0.160	—	0.157	—	0.454	—
48	2.319	0.559	—	—	—	3.014	—	0.159	—	0.168	—	0.468	—
49	2.309	0.562	—	—	—	—	2.108	0.159	—	0.151	—	0.468	—
50	2.312	0.555	—	—	—	—	—	0.160	2.210	0.151	—	0.454	—
51	2.313	0.554	—	—	—	—	—	0.160	—	0.151	3.207	0.468	—
52	2.307	0.562	—		—	—	—	0.160	—	0.151	—	0.468	2.516

TABLE 2
COPPER		N	RECRYSTALLIZATION	TENSILE	0.2% YIELD	ELECTRICAL
ALLOY	INTERMEDIATE	CONCENTRATION	TEMPERATURE	STRENGTH	STRENGTH	CONDUCTIVITY
SAMPLES	SAMPLES	(mass %)	(° C.)	(MPa)	(MPa)	(% IACS)
1	1	2.308	800	750	595	44
2	2	3.765	875	850	685	38
3	3	2.308	800	735	600	41
4	4	2.308	800	745	605	39
5	5	2.308	800	730	610	41
6	6	2.308	800	758	610	41
7	7	2.318	800	782	615	40
8	8	2.303	800	755	613	42
9	9	2.310	800	762	620	39
10	10	3.757	800	850	685	38
11	1	2.308	960	770	650	39
12	2	3.765	690	767	685	42
13	23	2.310	800	742	595	44
14	24	2.305	800	755	585	44
15	25	2.302	800	752	592	44
16	26	2.320	UNABLE TO CAST DUE TO FREQUENT OCCURRENCE OF OXIDE)
17	27	2.302	800	749	596	15
18	28	2.308	800	751	597	28
		AVERAGE				STRESS
	COPPER	CRYSTALLINE	DEVIATION OF			RELAXATION
	ALLOY	GRAIN	GRAIN	R/t	R/t	CHARACTERISTIC	PLATING
	SAMPLES	DIAMETER (μm)	DIAMETER (μm)	(GW)	(BW)	(%)	ADHERENCE
	1	12.5	4.4	0.0	0.0	25	GOOD
	2	11.2	4.3	1.3	0.8	22	GOOD
	3	14.5	6.0	0.0	0.0	16	GOOD
	4	13.6	5.0	0.0	0.0	20	GOOD
	5	14.2	5.5	0.0	0.0	24	GOOD
	6	11.8	4.0	0.0	0.0	24	GOOD
	7	11.7	4.1	0.0	0.0	19	EXCELLENT
	8	11.9	4.0	0.0	0.0	19	EXCELLENT
	9	11.5	4.0	0.0	0.0	16	EXCELLENT
	10	10.9	4.1	1.3	0.8	16	EXCELLENT
	11	153.6	35.0	0.8	0.5	8	NO GOOD
	12	NOT RECRYSTALLIZED	1.2	1.5	8	ACCEPTABLE
	13	12.2	4.4	0.0	0.0	25	GOOD
	14	12.3	4.3	0.0	0.0	25	GOOD
	15	12.7	4.4	0.0	0.0	25	GOOD
	16	UNABLE TO CAST DUE TO FREQUENT OCCURRENCE OF OXIDE)
	17	11.5	3.9	0.0	0.0	15	GOOD
	18	11.2	3.8	0.0	0.0	22	EXCELLENT

Here in accordance with Table 2, for the samples of the copper alloy 1 and 2 there are added Ni and Si as the contents in the copper alloy respectively. While, for the samples of the copper alloy 3 through 5 there is added any one nature of the elements of Mg, Sn and Zn in addition to Ni and Si respectively. Moreover, for the samples of the copper alloy 6 through 10 there are added at least any two natures of the elements of Mg, Sn and Zn in addition to Ni and Si respectively. Further, in the samples of the copper alloy 11 and 12 there is remained a part that the crystalline grain diameter becomes to be excessively larger due to the temperature to be recrystallized as excessively higher, or that is not recrystallized due to the temperature to be recrystallized as excessively lower. Furthermore, in the samples of the copper alloy 13 through 18 the amount of addition of any one of Mg, Sn and Zn is not within the range of the specification.

According to the result shown in Table 2, it is able to judge that both of the samples of the copper alloy 11 and 12 as the comparative samples in which each of the crystalline grain diameters becomes to be excessively larger are not sufficient on a practical use due to the plating adherence thereon, the stress relaxation characteristic and the bending workability as inferior thereto.

Moreover, it is found out on the contrary thereto that each of the copper alloys in accordance with the present invention (the samples of the copper alloy 1 through 10, and 13 through 15) has the characteristics of alloy as sufficient on the practical use regarding each of the items of the evaluation. Further, it is found out as shown in the results of the copper alloy samples 7, 8, 9 and 10 in particular that there becomes to be improved the plating adherence thereon and also there becomes to be contributed on the improvement of the tensile strength in the case where Zn is designed to be added as the further alloy content. Still further, it is found out as shown in the results of the copper alloy samples 6, 8, 9 and 10 that there becomes to be improved the stress relaxation characteristic in the case where Mg is designed to be added. Still further, it is found out as shown in the results of the copper alloy samples 6, 7, 9 and 10 that there becomes to be improved the stress relaxation characteristic as well in the case where Sn is designed to be added, and then the characteristic is remarkable in particular regarding the copper alloy samples 9 and 10 for which Mg is designed to be added together at the same time. Still further, it is found out as shown in the results of the copper alloy samples 9 and 10 that there becomes to be improved in total of the tensile strength, the stress relaxation characteristic and the plating adherence thereon due to the addition of Mg, Sn and Zn together at the same time. Still further, it is found out that the improvement and then the advantages due to the above mentioned any additions of Mg, Sn and Zn will not be appeared in a case where the amount of any of the additions is excessively smaller (refer to the copper alloy samples 13 through 15).

Further, in a case when Mg, Sn and Zn is added excessively, it is found out that it is difficult for casting in the case of MG (refer to the copper alloy sample 16), and electrical conductivity drastically decreases in the case of Sn and Zn (refer to the copper alloy samples 17 and 18).

TABLE 3
COPPER		N	RECRYSTALLIZATION	TENSILE	0.2% YIELD	ELECTRICAL
ALLOY	INTERMEDIATE	CONCENTRATION	TEMPERATURE	STRENGTH	STRENGTH	CONDUCTIVITY
SAMPLES	SAMPLES	(mass %)	(° C.)	(MPa)	(MPa)	(% IACS)
19	1	2.308	800	750	595	44
20	2	3.765	875	850	885	38
21	9	2.310	800	762	829	39
22	10	3.757	875	855	692	38
23	11	2.308	800	715	585	38
24	12	2.310	800	701	565	40
25	13	3.770	875	812	635	32
26	14	3.763	875	792	625	39
27	29	1.210	800	580	500	48
28	30	5.000	875	870	695	30
29	31	2.311	800	677	546	39
30	32	2.303	800	855	635	32
31	33	1.100	800	585	495	40
32	34	5.085	800	775	686	26
33	35	3.750	875	752	615	34
34	36	3.768	875	783	665	30
		AVERAGE				STRESS
	COPPER	CRYSTALLINE	DEVIATION OF			RELAXATION
	ALLOY	GRAIIN	GRAIN	R/t	R/t	CHARACTERISTIC	PLATING
	SAMPLES	DIAMETER (μm)	DIAMETER (μm)	(GW)	(BW)	(%)	ADHERENCE
	19	12.5	4.4	0.0	0.0	25	GOOD
	20	11.2	4.3	1.3	0.8	22	GOOD
	21	11.5	4.0	0.0	0.0	16	EXCELLENT
	22	10.9	4.1	1.3	0.8	16	EXCELLENT
	23	11.5	4.1	0.0	0.0	16	EXCELLENT
	24	12.7	4.2	0.0	0.0	16	EXCELLENT
	25	10.9	4.2	1.3	0.8	16	EXCELLENT
	26	10.6	4.1	1.3	0.8	16	EXCELLENT
	27	50.0	12.0	0.0	0.0	30	GOOD
	28	8.0	3.0	1.3	1.0	22	GOOD
	29	13.5	4.6	0.0	0.0	16	EXCELLENT
	30	10.5	4.1	0.0	0.0	16	EXCELLENT
	31	50.2	15.5	0.2	0.2	18	EXCELLENT
	32	0.0	1.2	0.2	0.2	16	EXCELLENT
	33	13.3	4.6	1.3	0.8	16	EXCELLENT
	34	10.2	4.1	1.3	0.8	16	EXCELLENT

Here in accordance with Table 3, there are shown for the case where the ratio of Ni/Si is 4.1 as the copper alloy samples 19 through 22, meanwhile, there are shown for the case where the ratio of Ni/Si is between two and seven as the copper alloy samples 23 through 26. Moreover, in order to compare and refer with making use of the above mentioned classification in accordance with Table 3, the table further includes some of the results as shown in Table 2 as well. Further, there are shown regarding Comparative samples as the copper alloy samples 27 through 34, in which either one of the contents of Ni and Si or the mass ratio is not within the range of the specification.

Here there are compared between the samples that individually contain Ni having the concentration as similar to therebetween. As comparing between the copper alloy samples 23 (Example) and of the number as 30 (Comparative example), or between the copper alloy samples 25 (Example) and of the number as 34 (Comparative example) for instance, the individual samples in accordance with Comparative example are inferior thereto in the tensile strength, in the 0.2% yield strength and in the electrical conductivity respectively. Moreover, as comparing and referring between the copper alloy samples 24 (Example) and of the number as 29 (Comparative example), or between the copper alloy samples 26 (Example) and of the number as 33 (Comparative example), the individual samples in accordance with Comparative example have the ratio of Ni/Si as larger than 7.0, and also each of the samples is inferior thereto in the tensile strength and in the 0.2% yield strength either respectively. Further, in the case where the concentration of Ni becomes to be lower than 1.5 mass % as given in accordance with the copper alloy samples 27 and 31 for example (for both as Comparative examples), there is occurred the deterioration of the tensile strength as drastically even in the case where the ratio of Ni/Si is maintained properly. And hence in accordance with the above mentioned results therefrom, it is found out that there is a tendency to occur both of the decreasing of the electrical conductivity and the deterioration of the strength in the case where the content of Ni or the ratio of Ni/Si is not within the range of the specification.

TABLE 4
COPPER		N	RECRYSTALLIZATION	TENSILE	0.2% YIELD	ELECTRICAL
ALLOY	INTERMEDIATE	CONCENTRATION	TEMPERATURE	STRENGTH	STRENGTH	CONDUCTIVITY
SAMPLES	SAMPLES	(mass %)	(° C.)	(MPa)	(MPa)	(% IACS)
35	9	2.310	800	789	710	39
36	15	2.314	800	790	715	41
37	16	2.310	800	792	725	39
38	17	2.305	800	785	723	39
39	18	2.310	800	792	722	39
40	19	2.306	800	795	735	39
41	20	2.318	800	793	724	39
42	21	2.302	800	794	728	39
43	22	2.303	800	788	725	38
44	37	2.314	800	781	711	39
45	38	2.310	800	779	712	39
46	39	2.311	800	779	708	39
47	40	2.311	800	782	709	39
48	41	2.311	800	777	708	39
49	42	2.305	800	781	709	39
50	43	2.319	800	782	711	39
51	44	2.320	800	778	711	39
52	45	2.323	800	792	718	42
53	46	2.250	UNABLE TO PROCESS NOT WORKING
			(DUE TO OCCURRENCE OF CRACKING)
54	47	2.307	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)
55	48	2.319	800	795	730	23
56	49	2.309	800	796	735	25
57	50	2.312	800	855	692	25
58	51	2.313	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)
59	52	2.307	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)
		AVERAGE				STRESS
	COPPER	CRYSTALLINE	DEVIATION OF			RELAXATION
	ALLOY	GRAIN	GRAIN	R/t	R/t	CHARACTERISTIC	PLATING
	SAMPLES	DIAMETER (μm)	DIAMETER (μm)	(GW)	(BW)	(%)	ADHERENCE
	35	11.5	4.0	0.3	0.3	16	EXCELLENT
	36	8.5	3.8	0.3	0.3	16	EXCELLENT
	37	4.8	1.8	0.2	0.2	16	EXCELLENT
	38	10.9	4.1	0.2	0.2	16	EXCELLENT
	39	10.9	4.1	0.3	0.3	16	EXCELLENT
	40	10.6	4.1	0.3	0.3	16	EXCELLENT
	41	10.3	3.8	0.3	0.3	16	EXCELLENT
	42	8.8	2.9	0.2	0.2	16	EXCELLENT
	43	8.5	2.6	0.2	0.2	16	EXCELLENT
	44	11.6	4.1	0.3	0.3	16	EXCELLENT
	45	11.4	3.9	0.3	0.3	16	EXCELLENT
	46	11.5	3.9	0.3	0.3	16	EXCELLENT
	47	11.3	4.1	0.3	0.3	16	EXCELLENT
	48	11.7	4.1	0.3	0.3	16	EXCELLENT
	49	11.2	4.1	0.3	0.3	16	EXCELLENT
	50	11.7	4.2	0.3	0.3	16	EXCELLENT
	51	11.8	4.1	0.3	0.3	16	EXCELLENT
	52	10.9	4.1	0.3	0.3	16	EXCELLENT
	53	UNABLE TO PROCESS NOT WORKING (DUE TO OCCURRENCE OF CRACKING)
	54	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)
	55	10.9	4.0	0.3	0.3	16	EXCELLENT
	56	10.9	3.9	0.3	0.3	16	EXCELLENT
	57	10.2	3.3	0.6	0.8	16	EXCELLENT
	58	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)
	59	UNABLE TO CAST (DUE TO FREQUENT OCCURRENCE OF OXIDE)

Here the results are shown in Table 4 with comparing between the copper alloy sample 35 (Example), for which there is not performed any addition of any one element that is selected from Ag, Co, Cr, Fe, Mn, P, Ti and Zr, and the copper alloy samples 36 through 43 (Examples) for which there is performed the addition of any one of the above mentioned elements that is selected within the range of the specification, and the copper alloy samples 44 through 51 (Comparative examples) for which there is performed the addition of any one of the above mentioned elements that is selected with the amount as less than the range of the specification. And hence in accordance with the results with the comparison therebetween, it is found out that there becomes to be improved the tensile strength and the 0.2% yield strength due to a function caused by the addition of the above selected any one of the elements in accordance with the copper alloy samples 36 through 43 (for instance, such as there is precipitated the chemical compound of the above selected any one of the elements with Ni or with Si, or the like). And in particular regarding the copper alloy samples 37, 38, 42 and 43, it is considered that there becomes able to be controlled the characteristic of the growth of the crystalline grains due to the addition of Co, Cr, Ti and Zr. As a result, it is found out that there becomes to be further improved the bending workability. Moreover, in the case where the amount of addition of the above mentioned any one of the elements that is selected is excessively lower on the contrary thereto, it is found out that it is not able to obtain any one of the above mentioned improvements and the advantages (refer to the copper alloy samples 44 through 51).

Further, in accordance with the copper alloy samples 52 through 59, it is designed to have individually the amount of addition of the above mentioned any one of the elements that is selected as excessively larger (as Reference examples). And hence in accordance with such as the copper alloy sample 53 for instance, it is not able to perform the hot working due to the occurrence of the cracks thereon. Still further, in accordance with the copper alloy samples 54, 58 and 59, it is not able to obtain any one of samples due to the occurrence of the oxides to be generated as a large amount at the period of the process of the casting. Furthermore, in accordance with the copper alloy samples 52, 55, 56 and 57, there becomes to be decreased the electrical conductivity as drastically or there becomes to be deteriorated the bending workability, because there becomes to be increased the precipitation due to the increasing of the amount of the additions.

TABLE 5
			RE-	TEMPERATURE		TEMPERATURE
COPPER		N	CRYSTALLIZATION	RISING	RETENTION	FALLING	ROLLING
ALLOY	INTERMEDIATE	CONCENTRATION	TEMPERATURE	RATE	TIME	RATE	RATE
SAMPLES	SAMPLES	(mass %)	(° C.)	(° C./S)	(S)	(° C./S)	(%)
60	9	2.310	800	50	120	30	5
61	9	2.310	800	50	15	30	5
62	9	2.310	800	35	85	30	5
63	9	2.310	800	50	100	50	5
64	9	2.310	800	50	280	50	5
65	9	2.310	800	50	120	50	5
66	15	2.314	800	50	120	30	5
67	15	2.310	800	50	120	30	5
68	9	2.310	800	50	1	30	5
69	9	2.310	800	5	100	30	5
71	9	2.310	800	9	100	30	5
71	9	2.310	800	25	100	7	5
72	9	2.310	800	50	310	30	5
73	9	2.310	800	50	450	30	5
74	9	2.310	800	55	150	1	5
					AVERAGE
	COPPER	TENSILE	0.2% YIELD	ELECTRICAL	CRYSTALLINE	DEVIATION OF
	ALLOY	STRENGTH	STRENGTH	CONDUCTIVITY	GRAIN	GRAIN	R/t	R/t
	SAMPLES	(MPa)	(MPa)	(% IACS)	DIAMETER (μm)	DIAMETER (μm)	(GW)	(BW)
	60	788	745	39	11.5	6.1	0.3	0.3
	61	782	744	40	11.8	6.2	0.3	0.3
	62	792	755	38	11.5	6.6	0.3	0.3
	63	783	742	39	11.7	6.1	0.3	0.3
	64	792	750	38	16.0	8.5	0.4	0.4
	65	795	752	38	17.5	7.5	0.4	0.4
	66	785	748	39	8.5	3.8	0.2	0.2
	67	792	748	39	4.8	1.8	0.2	0.2
	68	762	721	41	10.2	8.5	0.3	0.3
	69	792	755	39	21.0	13.5	0.7	0.7
	71	788	755	39	18.3	10.2	0.6	0.6
	71	782	753	39	18.5	9.2	0.5	0.5
	72	788	755	38	15.1	10.4	0.6	0.6
	73	792	756	38	22.0	14.2	0.7	0.7
	74	794	753	38	25.0	10.6	0.8	0.8

There are shown in Table 5 regarding the examples in the case of changing the temperature rising rate at the period of the process of treating with heat to be recrystallized, the end point temperature (temperature to be recrystallized), the retention time and the cooling (temperature falling) rate. And hence in accordance with such as the copper alloy samples 69 through 74 (Comparative examples) for instance, there are obtained the individual bending workability as inferior due to such as the average crystalline grain diameter becoming to be larger, or the like, because the amount of time for the process becomes to be longer in the temperature range at which the grain becomes to be grown. Moreover, in accordance with the copper alloy sample 68 (Comparative example), there are worsened the tensile strength and the 0.2% yield strength, for which the retention time is excessively shorter. Furthermore, the copper alloy samples 60 through 67 (Examples) on the contrary thereto, that there are performed the process individually by making use of the temperature rising rate, the retention time and the temperature falling rate within the specification of the method for producing the copper alloy in accordance with the present invention, it is found out that it becomes able to obtain each of the characteristics of alloy for each of Examples to be as excellent regarding each of the items of the evaluation.

INDUSTRIAL APPLICABILITY

The copper alloy for an electrical and electronic device in accordance with the present invention becomes to be applicable as preferred to the usage for the electrical device and for the electronic device, such as a lead frame, a connector, a terminal, a relay, a switch, or the like. Moreover, the method for producing the same in accordance with the present invention becomes to be preferable as the method by which it becomes able to produce further efficiently the above mentioned copper alloy for an electrical and electronic device.

Thus, there is described as above regarding the present invention in reference to the embodiment, however, the present invention will not be limited to every detail of the description as far as a particular designation, and it should be interpreted widely without departing from the spirit and scope of the present invention as disclosed in the attached claims.

Furthermore, the present invention claims the priority based on Japanese Patent Application No. 2007-080266, filed in Japan on the twenty-sixth day of March 2007, and on Japanese Patent Application No. 2008-079256, that is filed in Japan on the twenty-fifth day of March 2008, and the entire contents of which are expressly incorporated herein by reference.

Claims

1. A copper alloy for an electrical and electronic device, comprising:

Ni between 1.5 mass % and 5.0 mass %;

Si between 0.4 mass % and 1.5 mass %; and

a remaining portion formed of Cu and an unavoidable impurity,

wherein said copper alloy has a mass ratio of Ni/Si not smaller than two and not larger than seven, an average crystalline grain diameter not smaller than 2 μm and not larger than 20 μm, and a standard deviation of a crystalline grain diameter not larger than 10 μm.

2. The copper alloy for the electrical and electronic device according to claim 1, wherein said average crystalline grain diameter is within a range not larger than 15 μm, and said standard deviation of the crystalline grain diameter is not larger than 8 μm.

3. The copper alloy for the electrical and electronic device according to claim 1, wherein said average crystalline grain diameter is within a range not larger than 10 μm, and said standard deviation of the crystalline grain diameter is not larger than 5 μm.

4. The copper alloy for the electrical and electronic device according to claim 1, further comprising at least between 0.005 mass % and 2.0 mass % of one selected from the group consisting of Mg, Sn and Zn, said remaining portion being formed of Cu and the unavoidable impurity.

5. The copper alloy for the electrical and electronic device according to claim 1, further comprising at least between 0.005 mass % and 2.0 mass % of one selected from the group consisting of Ag, Co, Cr, Fe, Mn, P, Ti and Zr, said remaining portion being formed of Cu and the unavoidable impurity.

6. A method for producing a copper alloy for an electrical and electronic device, comprising at least a step a, a step b, and a step c as follows:

the step a of casting a copper alloy including Ni between 1.5 mass % and 5.0 mass %; Si between 0.4 mass % and 1.5 mass %; and a remaining portion formed of Cu and an unavoidable impurity, said copper alloy having a mass ratio of Ni/Si not smaller than two and not larger than seven, and performing hot working and cold working;

the step b of performing a re-crystallization heat treatment with a temperature rising rate of not slower than 10° C. per second, at an end point temperature between 700° C. and 950° C., for a retention time between five seconds and 300 seconds, and with a cooling rate not slower than 20° C. per second till 300° C. after the step a; and

the step b of performing an aging precipitation after the step b.