JP6522677B2 - Cu-Ni-Co-Si alloy for electronic parts - Google Patents

Description

  The present invention relates to a Cu-Ni-Co-Si alloy for electronic parts suitable for electronic parts, in particular, connectors, battery terminals, jacks, relays, switches, lead frames and the like.

  In recent years, the miniaturization of electronic components such as lead frames and connectors used for electric / electronic devices and in-vehicle components has progressed, and the tendency of narrowing the pitch and reducing the height of copper alloy members constituting the electronic components is remarkable. The smaller the connector is, the smaller the pin width is, and the smaller is the folded shape. Therefore, the copper alloy member to be used is required to have the strength and bending processability for obtaining the necessary spring property. In addition, from the viewpoint of suppressing heat generation due to high current, high conductivity of the copper alloy member is also required. To meet these requirements, Cu-Ni-Co-Si alloy has lower strength than Cu-Ni-Si alloy but high conductivity, and lower strength than Cu-Co-Si alloy. High in strength and balance between conductivity and conductivity, and used as a signal system terminal member.

  In order to secure the click feeling at the time of mounting, some members for signal system terminals are subjected to the same bending process as in the prior art after the plate thickness is reduced by tapping on both sides of the terminals beforehand. . A problem in this case is that bending distortion is impaired as compared to a state in which tapping is not applied because processing strain is introduced by adding tapping. Therefore, in addition to the balance of strength and conductivity which a Cu-Ni-Co-Si alloy has conventionally, maintaining bending workability is considered as a subject even if it adds striking processing.

  Under such background, Patent Document 1 discloses that bending workability is improved in addition to strength and conductivity by controlling the twin boundary frequency of Cu-Ni-Co-Si alloy and the area ratio of Cube orientation grains. It states that the improvement has been made. Specifically, 1.0 to 3.5% by mass of Ni, 0.5 to 2.0% by mass of Co, 0.3 to 1.5% by mass of Si, and Co / Ni mass ratio Is a copper alloy sheet having a ratio of 0.15 to 1.5, (Ni + Co) / Si mass ratio of 4 to 7 with the balance being Cu and unavoidable impurities, and the grain boundary character by EBSP measurement on the rolling surface A copper alloy sheet is disclosed in which the observation result of the crystal orientation is that the twin boundary density in all grain boundaries is 40% or more and the area ratio of Cube orientation crystal grains is 20% or more.

Patent Document 2 describes a technology in which the fatigue characteristics are improved by controlling the work hardening coefficient of the Cu-Ni-Si alloy. Specifically, 1.0 to 4.5% by mass in total of one or two selected from Ni and Co, 0.2 to 1.3% by mass of Si, (Ni + Co) / A copper alloy for electronic materials having Si (mass ratio) = 3.0 to 5.5 and the balance copper and unavoidable impurities, which is a half of the X-ray diffraction intensity peak from the {220} crystal plane of the rolled surface The valence width β {220} is the half value width of the X-ray diffraction intensity peak from the {220} crystal plane of pure copper standard powder, β ₀ {220}, and the following formula: 1.5 ≦ β {220} / A copper alloy for electronic materials is disclosed which satisfies β ₀ {220} ≦ 3 and has a work hardening coefficient (n value) of less than 0.04.

JP, 2011-231393, A JP 2012-224898 A

  The strength, conductivity and bending workability of Cu-Ni-Co-Si alloys have been improved from various points of view, but at the same time, miniaturization of electronic devices has also progressed, and more severe bending workability Is required. Other than notch bending and 180 degree close contact bending, a method is also adopted in which a material is beaten in a tapered shape (thickness reduction is performed) and then bending is applied. Although Patent Document 1 describes controlling the twin boundary frequency and the area ratio of Cube orientation grains, and Patent Document 2 controlling the work hardening index, it is possible to cope with bending to which tapping processing is applied by any measure. Is difficult.

  Then, this invention makes it a main subject to improve the bending workability of Cu-Ni-Co-Si alloy by an approach different from the past. Another object of the present invention is to provide a Cu-Ni-Co-Si alloy which is more excellent in bending workability than the conventional method.

  As a result of intensive investigations to solve the above problems, the present inventor believes that by simultaneously controlling the twin boundary frequency and the work hardening index, it may be able to withstand bending subjected to tapping. The In addition, I thought that controlling twin boundary frequency and work hardening index by new process is especially important.

  When this point was examined in more detail, it was found that the heat treatment at high temperature after hot rolling can control the twin boundary frequency, that is, the ratio of Σ3 corresponding grain boundaries to all grain boundaries. In addition, it has been found that the work hardening index (n value) can be controlled by applying a low temperature heat treatment before the solution treatment. It is considered preferable to increase the twin boundary frequency and reduce the work-hardening index in order to provide bending workability to which batting processing is added, but in the conventional method, if the former is increased, the latter is increased, the latter If you lower the former, the former will also go lower. On the other hand, new findings were obtained that it was possible to control both in a well-balanced manner by the process described above. Furthermore, it has been found that the mass ratio of Ni to Co (Ni / Co) influences twin boundary frequency and work hardening index. The present invention has been completed based on such findings.

  The Cu-Ni-Co-Si alloy for electronic parts of the present invention contains 3.0 to 5.0% by mass of Ni and 0.1 to 1.0% by mass of Co, and the mass ratio of Ni to Co (Ni / Co) is 3.5 to 30.0, Si is contained so that the mass ratio of (Ni + Co) / Si is 3 to 5, and the balance is composed of Cu and unavoidable impurities, and all crystal grains The proportion of Σ3 corresponding grain boundaries in the world is 10 to 40%, and the work hardening index is 0.01 to 0.07.

  The Cu-Ni-Co-Si alloy for electronic parts of the present invention further comprises a total of at least one selected from the group consisting of Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and Mn. 1.0 mass% can be contained.

  The Cu-Ni-Co-Si alloy for electronic parts of the present invention preferably has a 0.2% proof stress in a direction parallel to the rolling direction of 900 MPa or more, and a conductivity of 25% IACS or more.

  In the Cu-Ni-Co-Si alloy for electronic parts of the present invention, the bending axis is the same as the rolling direction, with bending radius (R) / plate thickness (t) = 5.0 after rolling at a working ratio of 20%. It is preferable that average roughness Ra of the bending part surface at the time of performing W bending test by (Badway) is 1.0 micrometer or less.

The method for producing a Cu-Ni-Co-Si alloy for electronic parts according to the present invention contains 3.0 to 5.0% by mass of Ni and 0.1 to 1.0% by mass of Co, and Ni relative to Co The mass ratio of (Ni / Co) is 3.5 to 30.0, the mass ratio of Si is (Ni + Co) / Si is 3 to 5, and the remainder is Cu and the unavoidable impurities A step of casting an ingot of a Ni-Co-Si alloy, a step of subjecting to homogenization annealing, a step of subjecting to hot rolling, a step of subjecting the first heat treatment at 850 to 900 ° C for 3 to 24 hours, and processing Cold rolling at a degree of 90% or more, second heat treatment at 450 to 650 ° C. for 1 to 10 hours, solution treatment, aging treatment, final cold rolling look including to carry out the step of applying in this order, occupied in the total grain boundaries That Σ3 proportion of coincidence boundary is 10-40%, and in which work hardening coefficient to produce a Cu-Ni-Co-Si alloy for electronic parts which is 0.01 to 0.07.

  In the method for producing a Cu-Ni-Co-Si alloy for electronic parts according to the present invention, the Cu-Ni-Co-Si alloy further comprises Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and At least one selected from the group consisting of Mn can be contained in total up to 1.0% by mass.

  The copper alloy product of the present invention comprises any of the above-mentioned Cu-Ni-Co-Si alloys.

  An electronic component of the present invention comprises any of the above-described Cu-Ni-Co-Si alloys.

  According to the present invention, it is possible to obtain a Cu-Ni-Co-Si alloy excellent in three characteristics of strength, conductivity and bending workability. Such a copper alloy can be particularly suitably used for an electronic component such as a connector or a battery terminal manufactured by applying a bending process after tapping, and can contribute to the improvement of the reliability of the electronic component.

(Ni concentration)
Ni has the effect of improving the strength and conductivity of a copper alloy sheet material by forming a Ni-Co-Si-based precipitate together with Co and Si described later. When the Ni content is too low, it is difficult to sufficiently exhibit this effect. Therefore, the Ni content is 3.0% by mass or more, preferably 3.3% by mass or more, and still more preferably 3.6% by mass or more. On the other hand, when the Ni content is too large, not only the strength improvement effect is saturated but also the conductivity is lowered. In addition, coarse precipitates are easily formed, which causes cracking during bending. Therefore, the Ni content is 5.0% by mass or less, preferably 4.7% by mass or less, and more preferably 4.4% by mass or less.

(Co concentration)
Co has the effect of improving the strength and conductivity of the copper alloy sheet by forming a Ni-Co-Si-based precipitate together with Ni and Si. If the Co content is too low, it will be difficult to fully exhibit this effect. Therefore, the Co content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.3% by mass or more. On the other hand, since the melting point of Co is higher than that of Ni, when the Co content is too large, complete solid solution is difficult, and the undissolved part does not contribute to the strength. Therefore, the Co content is preferably 1.0% by mass or less, preferably 0.9% by mass or less, and more preferably 0.8% by mass or less.

(Si concentration)
Si forms a Ni-Co-Si-based precipitate together with Ni and Co. However, Ni, Co and Si in the alloy do not necessarily all become precipitates by the aging treatment, and exist to some extent in a solid solution state in the Cu matrix. Ni, Co and Si in the solid solution state slightly improve the strength of the copper alloy sheet, but the effect is smaller than in the precipitation state, and it also causes the conductivity to be lowered. Therefore, it is generally preferable that the content of Si be as close as possible to the composition ratio of the precipitate (Ni + Co) ₂ Si. That is, the mass ratio of (Ni + Co) / Si is generally adjusted in the range of 3 to 5 with a center at about 4.2, and the mass ratio of (Ni + Co) / Si in this range is Si Add to make The mass ratio of (Ni + Co) / Si is preferably 3.7 to 4.7.

(Mass ratio of Ni to Co (Ni / Co))
By adjusting Ni / Co, both strength and conductivity are achieved. If the ratio of Ni is increased (the ratio of Co is decreased), the strength increases and the conductivity decreases. On the other hand, if the ratio of Co is increased (the ratio of Ni is decreased), the strength decreases and the conductivity increases. In order to set the 0.2% proof stress in the direction parallel to the rolling direction to 900 MPa or more and to set the conductivity to 25% IACS or more, Ni / Co is 3.5 to 30.0, preferably 5.0 It is good to adjust to be 12.0.

(Additive element)
If necessary, at least one of Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and Mn may be added. For example, Sn and Mg have an effect of improving stress relaxation resistance, Zn has an effect of improving the solderability and castability of a copper alloy sheet, and Fe, Cr, Mn, Ti, Zr, Al etc have strengths. It has an action to improve. In addition, P has a deoxidizing effect, and B has a refining effect on the cast structure, and has an effect of improving hot workability. However, when the amount of these additive elements is too large, the productivity and the conductivity are largely impaired. Then, the additive element can be made to be 0 to 1.0% by mass in total. Further, in consideration of the balance of strength, conductivity and bending workability, it is preferable to contain one or more of the above elements in a total amount of 0.01 to 0.7% by mass.

  In addition, in consideration of the balance of stress relaxation resistance, strength, solderability, castability, improvement of hot workability, etc., Zn is 0.1 mass in a range not exceeding the total amount for each additive element. % And 1.0% by mass or less, Sn and Cr can be contained 0.1% by mass or more and 0.8% by mass or less, and Fe, Mg and Mn are 0.01% by mass or more And 0.5 mass% or less can be contained, B, P, Zr, Ti, and Al can be contained 0.01 mass% or more and 0.2 mass% or less.

(Percentage of Σ3 corresponding grain boundaries in total grain boundaries)
According to the corresponding grain boundary theory, the 33 corresponding grain boundary refers to a twin boundary. Since the twin boundaries have good atomic consistency between the boundaries, nonuniform deformation is less likely to occur near the boundaries, and cracks and wrinkles originating from the vicinity of the boundaries are less likely to occur during bending, so the higher the ratio, the more bending. Processability becomes good.

  The ratio of Σ3 corresponding grain boundaries to total grain boundaries can be measured by the EBSD (Electron Back Scatter Diffraction Pattern) method. More specifically, after analyzing the crystal orientation by the EBSD method, it is possible to determine the difference in orientation between adjacent crystal orientations and to determine the ratio of random grain boundaries and each corresponding grain boundary (grain boundary character distribution). The ratio of Σ3 corresponding grain boundaries to total grain boundaries can be calculated by (sum of lengths of corresponding grain boundaries 33) / (sum of lengths of crystal grain boundaries) × 100.

  In the present invention, in the crystal orientation analysis in EBSD measurement for the material surface (rolled surface), the ratio of Σ3 corresponding grain boundaries to all grain boundaries is 10 to 40%. When this ratio is less than 10% or more than 40%, bending workability after being subjected particularly to a tapping process is deteriorated. In this respect, the ratio is preferably 15 to 35%, more preferably 20 to 30%.

  In the measurement of the proportion of Σ3 corresponding grain boundaries in all grain boundaries, the area of 400 μm × 400 μm per field of view is measured in five fields of view for the stability of the measurement results, and occupied in all grain boundaries in each field of view The proportion of Σ3 corresponding grain boundaries is determined, and the average value of the five fields of view is calculated and used as the measured value.

The following can be adopted as measurement conditions in EBSD measurement.
(A) SEM conditions-Beam conditions: acceleration voltage 15 kV, irradiation current amount 5 × 10 ^-8 A
・ Working distance: 25 mm
・ Viewing field: 400 μm × 400 μm
-Observation surface: rolled surface-Pre-treatment of observation surface: Electropolishing in a solution of phosphoric acid 67% + sulfuric acid 10% + water under conditions of 15V x 60 seconds to reveal the structure (b) EBSD condition-Measurement program : OIM Data Collection
-Data analysis program: OIM Analysis (Ver. 5.3)
・ Step width: 0.5μm

(Work hardening index (n value))
When a test piece is pulled in a tensile test and a load is applied, each part of the test piece extends uniformly (uniform elongation) in a plastic deformation area until the maximum load point is reached beyond the elastic limit. In the plastic deformation area which uniform elongation is generated between the true stress sigma _t and the true strain epsilon _t, relationship is established in the following equation (1), which is referred to n-th power hardening law.
σ _t = Kε _t ⁿ (1)
Here, in the formula (1), n is a work hardening index (Hajime Sudo, “Materials testing method”, Uchida Rohtsurusha, 1976, p. 34), 0 ≦ n ≦ 1. Take.

In materials that satisfy the n-th hardening law, the true strain at the highest load point of the stress-strain curve and the work hardening coefficient coincide, so in the present invention, the true strain at the highest load point is the work hardening index (n value) Toru (Kazuto Sudo, "Materials testing method", Uchida Rohtsurusha, 1976, p. 35). Specifically, a tensile test in a direction parallel to the rolling direction is performed according to JIS Z2241 (2011) by the same method as that for measuring the 0.2% proof stress described later to obtain a stress-strain curve. The true strain ε _t is calculated by substituting the nominal strain ε at the highest load point read from the obtained stress-strain curve into the following equation (2).
ε _t = ln (1 + ε) (2)

  In order to obtain a Cu-Ni-Co-Si alloy excellent in strength, conductivity and bending workability, it is possible to control the ratio of Σ3 corresponding grain boundaries to all grain boundaries and to set n value to a predetermined range. is important. In the case of a Cu-Ni-Co-Si alloy in which Ni / Co satisfies 3.5 to 30.0, work hardening occurs by tapping and the strength increases. At this time, since the strength is in a trade-off relationship with the bending processability, the bending processability is deteriorated due to the increase in strength. In order to suppress the increase in strength due to tapping, it is preferable to control so that the work hardening index becomes small. Specifically, the work hardening index (n value) in the direction parallel to the rolling direction is 0.01 to 0.07. The n value is preferably 0.01 to 0.06, more preferably 0.01 to 0.05.

(0.2% proof stress)
The 0.2% proof stress in the direction parallel to the rolling direction is measured in accordance with JIS Z 2241 (2011) (Metal material tensile test method). In one embodiment, in the Cu-Ni-Co-Si alloy according to the present invention, 0.2% proof stress in a direction parallel to the rolling direction can achieve 900 MPa or more. Preferably it is 950 MPa or more, More preferably, it is 1000 MPa or more. The upper limit value of the 0.2% proof stress is not particularly limited, but in order to achieve a conductivity of 25% IACS or more, it is 1100 MPa or less, and typically 1050 MPa or less.

(conductivity)
Measure according to the 4-terminal method in accordance with JIS H0505 (1975). In one embodiment, the conductivity of the Cu-Ni-Co-Si alloy according to the present invention can achieve 25% IACS or more. It is preferably 30% IACS or more, more preferably 35% IACS or more. The upper limit value of the conductivity is not particularly limited, but is 45% IACS or less, and typically 40% IACS or less in order to obtain a 0.2% proof stress of 900 MPa or more.

(Bendability)
The Cu-Ni-Co-Si alloy according to the present invention can have excellent bending workability. In one embodiment of the Cu-Ni-Co-Si alloy according to the present invention, after applying rolling with a working degree of 20% simulating tapping, according to JIS H3130 (2012), the W bending test is performed in the bending direction in the bending direction. When (R) / plate thickness (t) = 5.0, the average roughness Ra of the outer peripheral surface of the bent portion is 1.0 μm or less. Average roughness Ra is calculated in accordance with JIS B 0601 (2013). The fact that the average roughness Ra of the bent portion is small even after bending means that harmful cracks that may cause breakage are less likely to enter the bent portion. Generally, the average roughness Ra of the surface of the Cu-Ni-Co-Si alloy according to the present invention before the bending test is 0.2 μm or less.
From the viewpoint of preventing the occurrence of cracks described above, the average roughness of the surface of the bent portion is preferably 0.8 μm or less, and particularly preferably 0.6 μm or less. On the other hand, although there is no particularly preferred lower limit value, the average roughness of the surface of the bent portion is typically 0.1 μm or more, more typically 0.2 μm or more.

(Use)
The Cu-Ni-Co-Si alloy according to the invention can be processed into various copper products, such as plates, strips, tubes, bars and wires. The Cu-Ni-Co-Si alloy according to the present invention is suitably used as a conductive material or a spring material in electronic parts such as switches, connectors, jacks, terminals (particularly battery terminals), relays, but not limited thereto. be able to. These electronic components can be used, for example, as in-vehicle components or components for electric and electronic devices.

(Production method)
The example of the suitable manufacturing method of the Cu-Ni-Co-Si alloy which concerns on this invention is demonstrated for every process.

<Ingot casting>
Raw materials such as electric copper, Ni, Co, Si and the like are melted using an atmospheric melting furnace to obtain a molten metal having a desired composition as described above. Then, the molten metal is cast into an ingot. The additive elements other than Ni, Co and Si may be at least one selected from the group consisting of Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and Mn in total in a total of 0 to 1. It is added to contain 0% by mass.

<Homogenized annealing and hot rolling>
It is desirable to solidify and segregate and crystallize out of the ingot during the production of the ingot, so as to make it as small as possible in the matrix and to eliminate it as much as possible in the homogenization annealing. This is because it is effective in preventing bending and cracking. Specifically, after ingot casting, it is preferable to carry out hot rolling after heating to 900 to 1050 ° C. and homogenizing annealing for 3 hours to 24 hours. In hot rolling, it is preferable to make the path from the original thickness to the entire rolling reduction to 90% be 700 ° C. or more. Thereafter, it is rapidly cooled to room temperature by water cooling.

<First heat treatment>
After hot rolling, the first heat treatment at high temperature is performed. By re-solidifying coarse precipitates precipitated during hot rolling, the stacking fault energy can be reduced, and the proportion of 33 corresponding grain boundaries in the solution treatment described later can be increased. The conditions for the first heat treatment are typically from 3 hours to 24 hours at 850 to 900 ° C., preferably from 7 hours to 20 hours at 850 to 900 ° C., more preferably from 7 hours to 20 hours at 860 to 890 ° C. Water cooling after heating. When this step is not performed, the proportion of Σ3 corresponding grain boundaries in all grain boundaries is low even if the solution treatment and the subsequent steps are properly performed. Moreover, it becomes low similarly, even if it carries out 1st heat processing at less than 850 degreeC. On the other hand, when the first heat treatment is performed at a temperature exceeding 900 ° C., although the proportion of Σ3 corresponding grain boundaries becomes high, the crystal grain diameter becomes large, so the bending workability is lowered.

<Cold rolling and second heat treatment>
After the first heat treatment, cold rolling is performed at a working degree (rolling reduction) of 90% or more, preferably 93% or more, and then a second heat treatment at a low temperature is performed. Although the mechanism has not been elucidated, by adding a second heat treatment at a low temperature, the work hardening index can be reduced while maintaining the ratio of Σ3 corresponding grain boundaries to all grain boundaries. The conditions for the second heat treatment are typically 450 to 650 ° C. for 1 hour to 10 hours, preferably 500 to 600 ° C. for 1 hour to 10 hours, and more preferably 500 to 600 ° C. for 3 to 8 hours, Water cooling after heating. If this step is not performed, the work hardening index will be large even if the solution treatment and the subsequent steps are properly performed. Moreover, also when not performing 2nd heat processing on appropriate conditions, it becomes large similarly. The work hardening index also increases when the degree of working of cold rolling before the second heat treatment is too small. The degree of processing (%) is defined by {((thickness before rolling−thickness after rolling) / thickness before rolling) × 100}.

<Solution treatment>
Thereafter, solution treatment is performed. Specifically, it is heated to 800 to 1000 ° C., heated for 30 seconds to 10 minutes, and water cooled after heating.

<Aging treatment>
Aging treatment is performed following solution treatment. Heating at a material temperature of 400 to 550 ° C. for 5 to 25 hours is preferable, and heating at a material temperature of 430 to 520 ° C. for 10 to 20 hours is more preferable. The aging treatment is preferably performed in an inert atmosphere of Ar, N ₂ , H ₂ or the like in order to suppress the generation of an oxide film.

<Final cold rolling>
A final cold rolling is performed following the aging treatment. The final cold working can increase the strength, but the rolling reduction is 5 to 40%, preferably 10 to 35%, in order to obtain a good balance of strength and bendability as intended in the present invention. It is desirable to

<Strain relief annealing>
After the final cold rolling, strain relief annealing is performed. It is preferable to heat at a material temperature of 300 to 600 ° C. for 1 second to 3600 seconds, and a material temperature of 300 to 400 ° C. for 1500 seconds to 3600 seconds, a material temperature of 400 to 500 ° C. for 500 seconds to 1500 seconds, a material temperature of 500 to 600 It is more preferable to heat at 1 ° C for 1 second to 500 seconds.

  It will be understood by those skilled in the art that processes such as grinding, polishing, shot blasting and pickling for removing oxide scale on the surface can be appropriately performed between the above-described processes.

  Examples of the present invention are given below together with comparative examples, which are provided to better understand the present invention and its advantages, and are not intended to be limiting.

  A copper alloy containing each element shown in Table 1 and the balance being copper and impurities was melted at 1300 ° C. in a high frequency melting furnace and cast into an ingot of 30 mm thickness. Then, after heating this ingot at 980 ° C. for 5 hours, it was hot-rolled to a plate thickness of 0.93 to 10 mm, and was rapidly cooled after the completion of hot rolling. Next, the first heat treatment was performed under the conditions shown in Table 1 and immediately water cooled. Thereafter, cold rolling shown in Table 1 was performed to obtain a plate having a thickness of 0.117 mm. Then, the second heat treatment and solution treatment under the conditions shown in Table 1 were performed. Then, the plate thickness was made into 0.1 mm by the aging treatment for 15 hours at 450 degreeC, and rolling with a working degree of 15%, and strain relief annealing for 1000 seconds was implemented at 450 degreeC.

The following evaluation was performed about the produced test piece.
(A) Ratio of Σ3 corresponding grain boundary occupying in all grain boundaries After electropolishing the plate surface (rolled surface) of each test piece, EBSD measurement was performed. The total grain boundary length and the length of Σ3 corresponding grain boundary were determined, and the ratio was calculated.
(B) Work hardening index (n value)
A tensile test was conducted in a direction parallel to the rolling direction to obtain a stress-strain curve, and the n value was determined by the method described above.
(Iii) 0.2% proof stress JIS 13B test pieces were prepared, and 0.2% proof stress in a direction parallel to the rolling direction was measured using a tensile tester according to the measurement method described above.
(D) Conductivity In accordance with JIS H0505 (1975), the conductivity (EC:% IACS) was measured by the four-terminal method.
(E) Average roughness of the surface of the bent portion after rolling at a working ratio of 20% After rolling each test piece at a working ratio of 20% (plate thickness 0.08 mm) to simulate striking work, JIS H 3130 (2012 According to the above, W bending test was conducted at Badway (the bending axis is in the same direction as the rolling direction), R / t = 5.0, and the outer peripheral surface of the bending portion of this test piece was observed. As an observation method, the outer peripheral surface of the bent portion was photographed using a confocal microscope HD100 manufactured by Lasertec Corporation, and the average roughness Ra (based on JIS B 0601 (2013)) was measured and compared using the attached software. In addition, when the sample surface before bending was observed using a confocal microscope, the unevenness | corrugation was not able to be confirmed, but average roughness Ra was 0.2 micrometer or less in all. The case where the surface average roughness Ra after bending was 1.0 μm or less was evaluated as ○, and the case where Ra exceeded 1.0 μm was evaluated as x.

  As shown in Tables 1 and 2, each of Inventive Examples 1 to 20 contains each element in a predetermined amount, and is manufactured under the condition satisfying the predetermined range, so that the Σ3 corresponding grain boundary occupied in all grain boundaries. When the ratio was 10 to 40%, the work hardening index was 0.01 to 0.07, and the 0.2% proof stress, conductivity and bending workability became good.

On the other hand, in Comparative Examples 1 to 3, if the temperature condition of the first heat treatment is out of the predetermined range, or the first heat treatment is not performed, the ratio of the Σ3 corresponding grain boundary is within the predetermined range. As a result, bending workability deteriorated.
In Comparative Example 4, the degree of working of cold rolling after the first heat treatment is small, and in Comparative Examples 5 and 6, the second heat treatment is performed under temperature conditions outside the predetermined range, and in Comparative Example 7, the second heat treatment is not performed. As a result, in any of Comparative Examples 4 to 7, the work hardening index was out of the predetermined range, and the bending workability deteriorated.

  In Comparative Examples 8 and 9, the strength was reduced in Comparative Example 8 due to the content of Ni, and in Comparative Example 9, test pieces could not be produced.

In Comparative Examples 10 and 11, the bending workability and the ratio of the Σ3 corresponding grain boundary in Comparative Example 10 and the conductivity and bending workability in Comparative Example 11 were deteriorated due to the content of Co. In Comparative Examples 12 and 13, since the ratio of Ni / Co was outside the predetermined range, the bending workability and the ratio of the Σ3 corresponding grain boundary were deteriorated. In Comparative Examples 14 and 15, the strength or the conductivity decreased due to the ratio (Ni + Co) / Si being too small or too large. In Comparative Example 16, the conductivity decreased due to the addition of the additive element in excess of the predetermined amount.
Comparative Example 17 was produced according to the process described in Patent Document 1 and Comparative Example 18 according to the process described in Patent Document 2, but the proportion of Σ3 corresponding grain boundaries became higher than 40%, and the bending workability deteriorated.

Claims (8)

  3.0 to 5.0% by mass of Ni and 0.1 to 1.0% by mass of Co, and the mass ratio of Ni to Co (Ni / Co) is 3.5 to 30.0, Si is contained such that the mass ratio of (Ni + Co) / Si is 3 to 5, the balance is Cu and unavoidable impurities, and the ratio of Σ3 corresponding grain boundaries to all grain boundaries is 10 to 40%. And the Cu-Ni-Co-Si alloy for electronic components whose work-hardening index is 0.01-0.07.   The Cu-Ni according to claim 1, further comprising at most 1.0 mass% in total of at least one selected from the group consisting of Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and Mn. Co-Si alloy.   The Cu-Ni-Co-Si alloy according to claim 1 or 2, wherein 0.2% proof stress in a direction parallel to the rolling direction is 900 MPa or more and conductivity is 25% IACS or more.   The average roughness of the surface of the bending portion when the bending axis is subjected to W bending test in the same direction as the rolling direction as bending radius (R) / plate thickness (t) = 5.0 after rolling at a working ratio of 20% The Cu-Ni-Co-Si alloy according to any one of claims 1 to 3, wherein the thickness Ra is 1.0 μm or less. 3.0 to 5.0% by mass of Ni and 0.1 to 1.0% by mass of Co, and the mass ratio of Ni to Co (Ni / Co) is 3.5 to 30.0, A process of casting an ingot of a Cu-Ni-Co-Si alloy containing Si at a mass ratio of (Ni + Co) / Si of 3 to 5 and the balance being Cu and unavoidable impurities, and homogenization annealing Applying, hot rolling, first heat treatment at 850 to 900 ° C. for 3 to 24 hours, cold rolling at a working degree of 90% or more, and 450 to 650 ° C. seen containing a step of performing a second heat treatment of 10 hours, a step of performing solution heat treatment, a step of performing an aging treatment, and a step of subjecting the final cold rolling to be performed in this order,
Producing a Cu-Ni-Co-Si alloy for electronic parts, wherein the proportion of Σ3 corresponding grain boundaries in total grain boundaries is 10 to 40%, and the work hardening index is 0.01 to 0.07 . The manufacturing method of the Cu-Ni-Co-Si alloy for electronic components.   The Cu-Ni-Co-Si alloy further contains at most 1.0 mass% in total of at least one selected from the group consisting of Fe, Mg, Sn, Zn, B, P, Cr, Zr, Ti, Al and Mn. The manufacturing method of the Cu-Ni-Co-Si alloy according to claim 5.   A copper alloy product comprising the Cu-Ni-Co-Si alloy according to any one of claims 1 to 4.   The electronic component provided with the Cu-Ni-Co-Si alloy as described in any one of Claims 1-4.