JP2009280919A - Cu-Ni-Si ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Cu-Ni-Si alloy which simultaneously achieves spring property and solder wettability at a high level. <P>SOLUTION: The Cu-Ni-Si alloy is a copper-based alloy which contains 1.0-4.5 mass% Ni, 0.3-1.5 mass% Si, and 0.05-0.3 mass% Mg and further contains 0.05-2.0 mass% in total of at least one kind of elements selected from among Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, and Be, the balance being Cu and unavoidable impurities. The alloy has a 0.2% proof strength of 500 MPa or higher, a difference between the 0.2% proof strength and its spring limit value of 100 MPa or smaller, and an oxide film thickness of 10 nm or smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a Cu-Ni-Si alloy used for manufacturing electronic parts such as various terminals, connectors, relays, and switches, and more particularly, Cu-Ni-Si that simultaneously realizes spring property and solder wettability at a high level. It relates to alloys.

  Conventionally, inexpensive materials such as various terminals, connectors, relays, and switches of electronic devices that are required to have electrical conductivity and springiness have been applied to inexpensive brass. Also, phosphor bronze has been applied to applications where springiness is important. Furthermore, white is used for applications where springiness and corrosion resistance are important. However, with the recent reduction in weight, thickness, and size of electronic devices and their components, the use of these materials does not sufficiently satisfy the required strength.

  In recent years, materials that require electrical conductivity and springiness, such as various terminals, connectors, relays, and switches of electronic devices, have been replaced with conventional solid solution strengthened alloys such as phosphor bronze and brass. From the viewpoint of conductivity, the amount of age-hardening type copper alloys used is increasing. Age-hardened copper alloys are made by subjecting a supersaturated solid solution that has undergone solution treatment to fine precipitation of fine particles to improve strength characteristics such as proof stress or spring limit value, and to reduce the amount of solid solution elements. It contributes to the improvement of the rate.

  Accordingly, age-hardening type copper alloys are used as materials that satisfy increasingly demanding requirements for electronic devices and their components that are lighter and stronger. Of the age-hardening copper alloys, Cu-Ni-Si alloy is a representative copper alloy that has both high strength and high conductivity, and has been put into practical use as a material for various terminals, connectors, relays, and switches of electronic equipment. (Patent Documents 1 and 2). Si in the Cu—Ni—Si alloy is an active element, and an active metal may be further added for the purpose of improving the properties of the alloy. In this copper alloy, fine Ni—Si intermetallic particles are precipitated, the strength and conductivity are increased, and a material excellent in bending workability and stress relaxation characteristics can be obtained.

  On the other hand, since the Cu—Ni—Si alloy contains the active element Si, a strong oxide film is generated in the aging treatment in the final process. For this reason, there exists a problem that solder wettability falls remarkably. In order to avoid this problem, it is necessary to remove the oxide film by performing chemical polishing and mechanical polishing after aging. The chemical polishing in this specification is pickling as described below.

In this chemical polishing / mechanical polishing step, first, chemical polishing is performed. The oxide film of Cu—Ni—Si alloy containing SiO ₂ is very stable against acid. For this reason, in chemical polishing, it is necessary to use a chemical polishing solution having extremely high corrosive power, such as a solution in which hydrogen peroxide is mixed with hydrofluoric acid or sulfuric acid. In this way, by using a chemical polishing liquid having an extremely strong corrosive force, not only an oxide film but also an unoxidized portion may be corroded, and uneven unevenness and discoloration may occur on the surface after chemical polishing. There is. Further, the corrosion does not proceed uniformly, and the oxide film may remain locally. Therefore, in order to remove surface irregularities, discoloration, and residual oxide film, mechanical polishing is performed using, for example, a buff after the chemical polishing.

JP 2001-181759 A JP 2001-207229 A

  However, the Cu-Ni-Si alloy that has been subjected to chemical polishing and mechanical polishing in sequence does not change the yield strength (stress that causes permanent deformation when the sample is pulled), but the spring limit value (when the sample is bent) There is a problem in that the stress that causes permanent deformation is reduced. This is because the spring limit value increased by the aging treatment is lowered again by the chemical polishing / mechanical polishing. Therefore, in the conventional electronic component, there is a Cu—Ni—Si alloy whose spring limit value is significantly lower than the proof stress, or a Cu—Ni—Si alloy with a thick oxide film even if it has a spring limit value of the proof stress level. It was used.

  When spring parts such as connectors, relays, or switches are manufactured using a material with a low spring limit value, it is easy for permanent deformation (sagging) to occur in the movable part when the connector is inserted or pulled out. was there. When the sagging occurs, the contact pressure at the electrical contact decreases and the electrical resistance at the contact increases. On the other hand, when a spring component is manufactured using a material having a thick oxide film, the oxide film of the Cu—Ni—Si alloy is particularly strong, so that there is a problem that the solder wettability deteriorates remarkably. Accordingly, there has been a demand for the development of a Cu—Ni—Si alloy that realizes excellent spring properties by having a high spring limit value that does not cause the above-described sag and also has excellent solder wettability.

  Therefore, the present invention has been made in view of the above demands, and an object of the present invention is to provide a Cu—Ni—Si alloy that simultaneously realizes spring properties and solder wettability at a high level.

The Cu—Ni—Si alloy of the present invention contains 1.0 to 4.5% by mass of Ni, 0.3 to 1.5% by mass of Si, 0.05 to 0.3% by mass of Mg, Furthermore, it contains 0.05 to 2.0% by mass of one or more of Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, or Be, with the balance being Cu and inevitable impurities. The 0.2% proof stress is 500 MPa or more, the difference between the 0.2% proof stress and the spring limit value is 100 MPa or less, and the oxide film thickness is 10 nm or less.
As a result, sufficient strength can be satisfied even under recent demands for weight reduction of electronic devices and their components. The Cu—Ni—Si alloy of the present invention has a 0.2% yield strength of 500 MPa or more, and a difference between the 0.2% yield strength and the spring limit value is 100 MPa or less. For this reason, the spring limit value for the proof stress is remarkably high, as in the case of Cu-Ni-Si alloys that have been subjected to sequential chemical polishing and mechanical polishing after having sufficient proof strength to be used in electronic devices, etc. The spring property which was excellent by having a high spring limit value is not reduced. Furthermore, the Cu-Ni-Si alloy of this invention can implement | achieve the outstanding solder wettability because the oxide film thickness was 10 nm or less.

Further, another Cu-Ni-Si alloy of the present invention contains 1.0 to 4.5 mass% of Ni, 0.3 to 1.5 mass% of Si, and 0.05 to 0.3 mass% of Mg. And further containing one or more of Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, or Be in a total amount of 0.05 to 2.0 mass% with the balance being Cu and A copper-based alloy composed of inevitable impurities, characterized in that the absolute value of the residual stress on the surface is 100 MPa or less and the oxide film thickness is 10 nm or less.
As described above, the Cu—Ni—Si alloy of the present invention can satisfy sufficient strength by containing 1.0 to 4.5 mass% of Ni and 0.3 to 1.5 mass% of Si. In addition, excellent solder wettability can be realized by setting the oxide film thickness to 10 nm or less. By the way, as a result of investigating the cause of the decrease in the spring limit value of the Cu—Ni—Si alloy in the chemical polishing / mechanical polishing step after aging, the present inventors have found that the material remains on the outermost layer of the material by mechanical polishing after chemical polishing It was found that stress is generated and the spring limit value is lowered by the action of this residual stress. Based on this knowledge, in the Cu—Ni—Si alloy of the present invention, the absolute value of the residual stress on the surface is set to 100 MPa or less. Therefore, according to the present invention, it is possible to realize a spring property suitable for use in electronic devices and the like.

  According to the Cu—Ni—Si alloy of the present invention, the spring property and the solder wettability can be simultaneously realized at a high level. Therefore, the present invention is extremely promising in that it is possible to manufacture a Cu—Ni—Si alloy suitable for manufacturing various electronic components that can sufficiently meet the recent demands for weight reduction, thickness reduction, and size reduction. .

It is a figure which shows the measurement principle of a residual stress. It is a graph which shows the relationship between sputtering time and the detection intensity of oxygen. It is a figure which shows the bending test method. It is a graph which shows the relationship between (0.2% yield strength-spring limit value) and residual stress. It is a graph which shows the relationship between a permanent deformation amount and (0.2% yield strength-spring limit value).

As described above, the present inventors have found that the cause of the decrease in the spring limit value is the generation of residual stress due to mechanical polishing after chemical polishing. Next, based on this finding, the present inventors have found that a state of low residual stress after aging can be realized by preventing formation of an oxide film on the surface of the Cu-Ni-Si alloy during aging and omitting mechanical polishing. Got. Moreover, even if the residual stress once increased in the chemical polishing / mechanical polishing process, it was also found that a state in which the residual stress is low can be realized by performing a process for reducing the residual stress in the subsequent process. Therefore, as a result of further diligent research based on the above knowledge, the present inventors, as a specific manufacturing method of Cu-Ni-Si alloy,
(1) An aging treatment is performed by appropriately selecting the dew point (water vapor concentration), temperature and holding time in an atmosphere containing a large amount of hydrogen, and the formation of an oxide film on the Cu-Ni-Si alloy surface is prevented during aging. Embodiment,
(2) A mode in which an aging treatment is performed by appropriately selecting a temperature and a holding time in a high vacuum atmosphere, and an oxide film is prevented from being formed on the surface of the Cu-Ni-Si alloy during aging,
(3) After Cu plating is applied to the surface of the Cu-Ni-Si alloy, an aging treatment is performed by appropriately selecting the temperature and holding time, and then a Cu plating layer (including a surface oxide layer of Cu plating) is obtained by chemical polishing. An aspect of removing
(4) An aging treatment is performed by appropriately selecting a temperature and a holding time, and then an oxide film is removed by a chemical polishing / mechanical polishing process. Then, a dew point (water vapor concentration), a temperature, and an atmosphere containing a large amount of hydrogen It has been found that it is effective to appropriately select a holding time and then adopt a mode in which strain relief annealing is performed to remove residual stress. Hereinafter, the manufacturing method of the Cu-Ni-Si alloy of this invention is demonstrated about each of said (1)-(4).

  In the method for producing a Cu—Ni—Si alloy of the present invention, cold rolling is performed after the solution treatment, the hydrogen concentration is 50 vol% or more, the balance is made of an inert gas, the dew point is −40 ° C. or less, and 350 to 650 An aging treatment is performed by holding at 10 ° C. for 10 seconds to 15 hours. The present invention embodies the above aspect (1). In the manufacturing method of the Cu-Ni-Si alloy of the present invention, mechanical polishing is not performed. For this reason, unlike conventional Cu-Ni-Si alloys that have been sequentially subjected to chemical polishing and mechanical polishing, the spring limit value is not lowered due to the occurrence of residual stress due to mechanical polishing, and a high spring limit value is obtained. By having it, an excellent spring property can be realized. Moreover, in the manufacturing method of the Cu-Ni-Si alloy of this invention, aging is performed by selecting an appropriate dew point (water vapor concentration), temperature, and holding time in an atmosphere containing a large amount of hydrogen. For this reason, formation of an oxide film on the surface of the Cu—Ni—Si alloy is prevented during aging, and excellent solder wettability can be realized.

Another manufacturing method of the Cu-Ni-Si-alloys of the present invention performs a cold rolling after the solution treatment, at a pressure of ¹⁰ -2 Pa or less, the aging by holding 10 seconds to 15 hours at 300 to 650 ° C. It is characterized by processing. The present invention embodies the above aspect (2). In the manufacturing method of the Cu-Ni-Si alloy of this invention, since mechanical polishing is not given, the outstanding spring property is realizable as above-mentioned. Moreover, in the manufacturing method of the Cu-Ni-Si alloy of this invention, aging treatment is performed by appropriately selecting the temperature and holding time in a high vacuum atmosphere. For this reason, formation of an oxide film on the surface of the Cu—Ni—Si alloy is prevented during aging, and excellent solder wettability can be realized.

  Another method for producing the Cu—Ni—Si alloy of the present invention is to perform cold rolling after the solution treatment, apply Cu plating with a thickness of 0.5 to 10 μm on the surface, and then apply 10 to 300 to 650 ° C. An aging treatment is performed by holding for 2 seconds to 15 hours, and then the Cu plating layer is removed by chemical polishing. The present invention embodies the above aspect (3). In the manufacturing method of the Cu-Ni-Si alloy of this invention, since mechanical polishing is not given, the outstanding spring property is realizable as above-mentioned. Moreover, in the manufacturing method of the Cu-Ni-Si alloy of the present invention, the Cu-Ni-Si alloy surface is subjected to Cu plating having a thickness that can be easily removed in a later step, and then the temperature and holding time are appropriately selected. An aging treatment is performed, and then the Cu plating layer (including the surface oxide layer of Cu plating) is removed by chemical polishing. For this reason, even if an oxide film is formed on the Cu plating layer in the aging treatment, the oxide film can also be reliably removed by removing the Cu plating layer by chemical polishing thereafter. Thus, since the oxide film is removed on the Cu—Ni—Si alloy surface after aging, excellent solder wettability can be realized.

Another method for producing the Cu-Ni-Si alloy of the present invention is to perform cold rolling after the solution treatment, apply an aging treatment by holding at 300 to 650 ° C for 10 seconds to 15 hours, and then perform the aging treatment. Is removed by chemical polishing and mechanical polishing, and further, H ₂ concentration is 50 vol% or more, dew point is −40 ° C. or less, and held at 400 to 650 ° C. for 5 seconds to 2 minutes to remove strain annealing. It is characterized by giving. The present invention embodies the above aspect (4). In the method for producing a Cu—Ni—Si alloy of the present invention, an aging treatment is performed by appropriately selecting a temperature and a holding time, and then an oxide film is removed by performing chemical polishing and mechanical polishing. This mechanical polishing generates a residual stress in the outermost layer of the material, and the spring limit value is lowered by the action of the residual stress. Therefore, strain relief annealing is performed to remove residual stress after mechanical polishing. Thus, even if the residual stress once increases in the chemical polishing / mechanical polishing step, a state in which the residual stress is low can be realized by performing a process for reducing the residual stress in the subsequent steps. Therefore, excellent spring properties can be realized by having a high spring limit value. Furthermore, the surface of the Cu-Ni-Si alloy during strain relief annealing is performed by appropriately selecting the dew point (water vapor concentration), temperature and holding time in an atmosphere containing a large amount of hydrogen. It is possible to suppress the oxidation of the solder and to obtain excellent solder wettability.

Next, the reasons for limiting the component composition and production conditions of the present invention will be specifically described.
Ni and Si concentrations Ni and Si are formed by aging treatment, whereby Ni and Si form fine intermetallic compound precipitates mainly composed of Ni ₂ Si, while significantly increasing the strength of the alloy. Maintain high electrical conductivity. However, when the Ni content is less than 1.0 mass% and the Si content is less than 0.3 mass%, the desired strength cannot be obtained even when the other component is added, and the Ni content is 4%. When the amount exceeds 5 mass% or the Si content exceeds 1.5 mass%, sufficient strength can be obtained, but the desired electrical conductivity is lowered, and further, it does not contribute to the improvement of strength. Ni—Si-based particles (crystallized substances and precipitates) are generated in the matrix phase, and bending workability, etching properties and plating properties are reduced. Therefore, the Ni content was determined to be 1.0 to 4.5 mass%, and the Si content was determined to be 0.3 to 1.5 mass%.

Mg concentration Mg has the effect of greatly improving the stress relaxation properties and the hot workability, but if it is less than 0.05% by mass, the effect cannot be obtained, and if it exceeds 0.3% by mass, the castability is increased. (Deterioration of casting surface quality) Since hot workability and plating heat-resistant peelability are reduced, the Mg content is determined to be 0.05 to 0.3% by mass.

Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, or Be
Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, or Be has an effect of improving the strength and heat resistance of the Cu—Ni—Si alloy. Of these, Zn also has an effect of improving the heat resistance of the solder joint, and Fe has an effect of refining the structure. Further, Ti, Zr, Al, and Mn have an effect of improving the hot rolling property. This is because these elements have a strong affinity with sulfur and form a compound with sulfur, thereby reducing the segregation of sulfur to the ingot grain boundaries, which is the cause of hot rolling cracks. If the total content of Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, Ag, or Be is less than 0.05% by mass, the above effect cannot be obtained, and the phase content is 2 If it exceeds 0.0% by mass, the electrical conductivity is remarkably lowered. Therefore, these contents are set to 0.05 to 2.0% by mass in total.

When the oxide film thickness exceeds 10 nm, the solder wettability decreases. Therefore, the oxide film thickness is limited to 10 nm or less.

0.2% proof stress 0.2% proof stress is required to be 500 MPa or more in the connector design. In order to obtain sufficient spring strength, 600 MPa or more is desirable.

In order to obtain spring characteristics commensurate with the 0.2% yield strength of the spring limit value alloy, the spring limit value needs to be (0.2% yield strength−100) MPa or more. Since the connector is designed based on the proof stress of the material, if the spring limit value is less than (0.2% proof stress−100) MPa, the above sag occurs, and a desired contact pressure cannot be obtained. In the invention, there is no case where the spring limit value greatly exceeds (0.2% proof stress + 100) MPa.

In order to obtain a spring limit value of residual stress (0.2% yield strength−100) MPa or more, the absolute value of the residual stress on the surface needs to be 100 MPa or less.

Solution treatment conditions The solution treatment conditions are not particularly limited. In order to obtain a high-strength material by aging treatment, it is necessary to sufficiently dissolve Ni—Si. It is desirable to heat at a temperature that completely dissolves therein. This temperature is 750 ° C to 850 ° C. In order to obtain higher strength, it is important not to make the crystal grains coarse during heating. Furthermore, as a cooling method after the solution treatment, it is desirable to employ air cooling or water mist spray cooling with a sufficiently high cooling rate so that Ni—Si does not precipitate in the cooling process.

Cold rolling performed between the cold rolling solution treatment and the aging treatment is performed in order to obtain higher strength. The degree of work in cold rolling is not particularly limited, but as the degree of work increases, the strength increases, but the bendability decreases, so it is necessary to design the degree of work according to the application. The normal workability used industrially in Cu-Ni-Si alloys is in the range of 10-70%. The degree of processing (R) is defined by the following equation.
R = (t ₀ −t) / t ₀ × 100 (%) (t ₀ : thickness before rolling, t: thickness after rolling)

In order to improve the aging temperature, the aging time strength, and the conductivity, it is important to perform an aging treatment for 10 seconds to 15 hours in a temperature range of 300 to 650 ° C. The aging temperature is the atmospheric temperature inside the heating furnace, and the aging time is the time that the material stays in the heating furnace. Since the Ni—Si solid solution amount in Cu decreases as the temperature decreases, the precipitation amount of Ni—Si grains increases as aging at a low temperature, and higher strength and conductivity can be obtained. However, since the time required for the aging treatment becomes longer, the manufacturing cost becomes higher. On the other hand, since the deposition rate of Ni—Si grains increases as the temperature increases, the predetermined conductivity and strength can be obtained in a shorter time as the temperature increases. However, there is a risk that the reached values of conductivity and strength are lowered. Therefore, it is desirable to appropriately select the aging temperature and aging time according to the manufacturing cost and the target characteristics.

If the aging temperature is less than 300 ° C., the aging treatment takes an extremely long time, which is not preferable in terms of production economy. On the other hand, when the aging temperature exceeds 650 ° C., the amount of Ni—Si grains precipitated decreases, and the strength and conductivity are hardly improved, which is not preferable. An aging time of less than 10 seconds is not preferable because Ni—Si grains are not sufficiently precipitated and strength and conductivity are not improved. On the other hand, if the aging time exceeds 15 hours, not only is the production cost high, but when a relatively high aging temperature is selected, the precipitates become coarse and the strength decreases, which is not preferable. Below, the aging conditions suitable about the case where a batch annealing furnace is used are shown.
Batch annealing furnace: 400 ° C to 500 ° C, 1 hour to 15 hours

Means for Suppressing Formation of Oxide Film Means for setting the oxide film thickness to 10 nm or less will be described in detail in the following cases (1) to (4).

  (1) An aging treatment is performed in an inert gas mixed with hydrogen. In order to control the oxide film thickness to 10 nm or less, it is necessary to set the hydrogen concentration to 50 vol% or more and to set the dew point to −40 ° C. or less. Nitrogen or argon can be used as the inert gas. The gas pressure is not limited, but usually a pressure slightly higher than atmospheric pressure is employed.

(2) Aging is performed in a high vacuum atmosphere. In order to control the oxide film thickness to 10 nm or less, the pressure needs to be 10 ⁻² Pa or less.

  (3) Cu plating is applied to the material surface before aging. Cu is less likely to be oxidized than Cu-Ni-Si alloys, and the oxide film can be easily removed by chemical polishing together with the plated Cu itself. After Cu plating, an aging treatment is performed in a conventional atmosphere such as an inert gas, and finally an oxide film formed on the Cu plating by chemical polishing is dissolved and removed together with the Cu plating layer. Cu plating can be performed under general production conditions using a bath of copper sulfate or the like. However, the thickness of the plating needs to be controlled to 0.5 to 10 μm. When the plating thickness is less than 0.5 μm, an oxide film may be formed on the base material of the Cu—Ni—Si alloy. If chemical polishing is performed until the oxide film is removed, unevenness and discoloration are likely to occur on the surface, and mechanical polishing cannot be omitted. On the other hand, when the thickness of the Cu plating exceeds 10 μm, the manufacturing cost is not only high, but it is difficult to remove the Cu plating layer by chemical polishing. As the chemical polishing liquid, for example, a solution obtained by mixing a small amount of hydrogen peroxide with sulfuric acid can be used.

  (4) After performing an aging treatment in a conventional atmosphere such as an inert gas, the oxide film formed by the aging is removed by chemical polishing and mechanical polishing. Among these polishing processes, residual stress is generated in the outermost layer of the material in the mechanical polishing process, and the spring limit value is lowered by the action of the residual stress. However, the strain relief annealing is performed in the next process to remove the residual stress and improve the spring limit value. The strain relief annealing is performed by continuous annealing at a temperature of 400 to 650 ° C. for 5 seconds to 2 minutes. If the temperature is less than 400 ° C., the residual stress is not removed, and if it exceeds 650 ° C., the strength and conductivity are remarkably lowered. Further, if the time is less than 5 seconds, the residual stress is not removed, and if it exceeds 2 minutes, the 0.2% proof stress is remarkably lowered. In order to control the oxide film thickness generated by strain relief annealing to 10 nm or less, it is necessary to set the hydrogen concentration to 50 vol% or more and the dew point to −40 ° C. or less. Nitrogen or argon can be used as the inert gas. The pressure of the gas is not limited, but usually a pressure slightly higher than atmospheric pressure can be employed.

Next, examples of the present invention will be described.
A Cu—Ni—Si alloy having an Ni concentration of 2.5% by mass, an Si concentration of 0.55% by mass and an Mg concentration of 0.16% by mass using electrolytic copper or oxygen-free copper as a raw material and using a high-frequency vacuum melting furnace An ingot (thickness 150 mm) was produced. This ingot was processed to 10 mm by hot rolling, repeated cold rolling and annealing, and further processed to a thickness of 0.2 mm by final cold rolling. Thereafter, a solution treatment was performed at 780 ° C. to finish the crystal grain size to about 10 μm, and then processed to a thickness of 0.15 mm by cold rolling. Using this 0.15 mm material, an aging treatment was performed under various conditions, and the residual stress, oxide film thickness, solder wettability, and spring limit value (spring property) were evaluated. Further, a comprehensive evaluation was conducted as to whether or not both the spring limit value and the solder wettability showed excellent results. Each evaluation method is shown below.

The residual stress generated in the direction parallel to the rolling direction with respect to the (113) plane was determined by the residual stress X-ray diffraction method. The principle and calculation formula of stress measurement are shown below.

・ Residual Stress Measurement Principle As shown in FIG. 1, when the angle ψ between the sample surface normal N and the lattice surface normal N ′ is changed and the change in the diffraction angle (2θ) is investigated, the residual stress σ is expressed by the following equation: Can be requested.

In the above equation, K (stress constant) is a constant determined by the material and the diffraction angle. A 2θ / sin ² ψ diagram is drawn from the measured value, then the gradient is obtained by the least square method, and K is multiplied to obtain the residual stress.

Oxide film thickness The oxide film thickness was measured by Auger electron spectroscopy. Oxygen intensity measurement and surface Ar sputtering were performed alternately to obtain the graph shown in FIG. In this figure, the sputtering time when the detected oxygen intensity is an intermediate value between the maximum value on the surface and the value at the non-oxidized part was determined, and this time was regarded as the time required for sputtering of the oxide film. The oxide film thickness was obtained by multiplying the above time by the sputtering rate of the SiO ₂ film.

Solder wettability In accordance with JIS-0053 (1996), the time at which wetting begins was measured by the meniscograph method. The measurement conditions are as follows. The sample was degreased using acetone as a pretreatment. Next, chemical polishing was performed using a 10 vol% sulfuric acid aqueous solution. The solder used was 60% Pb-40% Sn, and the measurement temperature was 235 ° C. GX5 manufactured by Asahi Chemical Laboratory was used for the flux. The immersion depth was 2 mm, the immersion time was 10 seconds, the immersion speed was 15 mm / second, and the sample width was 10 mm. Evaluation criteria were good (◯) when the time until wetting started was 1 second or less, and bad (x) when it exceeded 1 second.

The yield strength in the direction parallel to the rolling direction was measured by a 0.2% yield strength and spring limit value tensile tester. Further, the spring limit value in the direction parallel to the rolling direction was measured by a moment type test specified in JIS-H3130. As the evaluation criteria for the spring property, those having a spring limit value of (yield strength −100 (MPa)) or more were evaluated as good (◯), and those less than (yield strength −100 (MPa)) were evaluated as poor (×).

In order to evaluate the performance as a deflection test electronic component material, as shown in FIG. 3, one end of a test piece was fixed, and a load f was applied to a position at a distance l from the fixed end to give a deflection f. After removing the load, the amount of permanent deformation δ of the sample was measured. The sample was prepared so that the width W of the sample was 10 mm and the longitudinal direction of the sample was parallel to the rolling direction. Further, l = 10 mm and f = 5 mm. The stress generated on the sample surface at this time is expressed by the cantilever equation σ = 6P · l / (W · t ² ) (t: thickness of the sample)
It was about 550 MPa when it calculated using.

The items actually examined by the inventors will be described below.
[Examination of conventional manufacturing methods]
After an aging treatment at 430 ° C. for 8 hours in an Ar gas atmosphere having a dew point of −10 ° C., the surface was mechanically polished. In this polishing, the polishing amount was variously changed. After polishing, 0.2% yield strength, spring limit value, surface residual stress, oxide film thickness and solder wettability were measured. Further, the amount of permanent deformation when a predetermined deflection was given to the sample by the method of FIG. 3 was measured. These results are shown in Table 1.

  In the table, the larger the number, the greater the amount of mechanical polishing. It can be seen that the greater the mechanical polishing, the greater the compressive residual stress generated on the sample surface. As shown in FIG. 4, when the residual stress increases, the spring limit value decreases and the spring property gradually deteriorates. When the residual stress exceeds 100 MPa, the difference between the 0.2% proof stress and the spring limit value exceeds 100 MPa. As shown in FIG. 5, when the difference between the 0.2% proof stress and the spring limit value exceeds 100 MPa, permanent deformation occurs when a predetermined deflection is applied to the sample. The amount of permanent deformation increases as the difference between the 0.2% proof stress and the spring limit value increases. Such permanent deformation is not preferable because it causes a decrease in contact pressure at the connector contact.

  On the other hand, the greater the amount of mechanical polishing, the smaller the oxide film thickness. When the oxide film thickness was 10 nm or less, good solder wettability was achieved. Sex was not realized. From the above, Conventional Examples 1 to 9 shown in Table 1 are not compatible with a high level of spring limit value and solder wettability, and excellent results are not obtained in comprehensive evaluation.

[Study on the production method according to claim 3 of the present invention]
An invention example relating to the manufacturing method according to claim 3 of the present invention will be described. For each of Invention Examples 10 to 12 and Comparative Examples 13 to 15, the results shown in Table 3 were obtained under the aging treatment conditions shown in Table 2. In addition, about each invention example and each comparative example, surface treatments, such as chemical polishing and mechanical polishing, are not performed after aging.

  As shown in Table 2, for Invention Examples 10 to 12, the dew point in the annealing furnace was set to -40 ° C. or lower, and an aging treatment was performed. As apparent from Table 3, the invention examples 10 to 12 did not oxidize on the surface, achieved good solder wettability, and had good spring properties. Therefore, excellent results were obtained in the comprehensive evaluation for each of the inventive examples. On the other hand, Comparative Examples 13-15 performed the aging process by making the dew point in an annealing furnace higher than -40 degreeC. About Comparative Examples 13-15, although the spring property was favorable from having obtained the high spring limit value, since the surface oxidized, favorable solder wettability was not obtained. Therefore, excellent results were not obtained in the comprehensive evaluation for each comparative example.

[Study on the production method according to claim 4 of the present invention]
The Example regarding the manufacturing method of Claim 4 of this invention is demonstrated. The results shown in Table 5 were obtained under the aging treatment conditions shown in Table 4 for each of Invention Examples 16 to 18 and Comparative Examples 19 to 21. In addition, about each invention example and each comparative example, surface treatments, such as chemical polishing and mechanical polishing, are not given after aging.

As shown in Table 4, Invention Examples 16 to 18 are obtained by performing an aging treatment with the degree of vacuum in the annealing furnace being 10 ⁻² Pa or less. As can be seen from Table 5, Invention Example 16 exhibited good solder wettability with Invention Examples 17 and 18 although it caused slight surface oxidation, and also had good spring properties. Therefore, excellent results were obtained in the comprehensive evaluation for each of the inventive examples. On the other hand, Comparative Examples 19-21 perform aging annealing by making the vacuum degree in an annealing furnace higher than 10 ^<-2 > Pa. In Comparative Examples 19 to 21, although the spring property was good, the surface was oxidized, so that good solder wettability could not be realized. Therefore, excellent results were not obtained in the comprehensive evaluation for each comparative example.

[Study on the production method according to claim 5 of the present invention]
The Example regarding the manufacturing method of Claim 5 of this invention is demonstrated. For each of Invention Examples 22 to 24 and Comparative Examples 25 and 26, the results shown in Table 7 were obtained under the plating treatment conditions, aging treatment conditions, and surface treatment conditions shown in Table 6.

  As shown in Table 6, Invention Examples 22 to 24 are obtained by performing aging treatment after applying Cu plating to the final rolled material, and finally removing Cu plating on the surface by chemical polishing. For this reason, as can be seen from Table 7, good spring properties and solder wettability could be realized. Therefore, excellent results were obtained in the comprehensive evaluation for each of the inventive examples. On the other hand, Comparative Example 25 was subjected to 0.2 μm Cu plating, and since the Cu plating layer was thin, the surface of the base material was oxidized, and good solder wettability could not be realized. Further, Comparative Example 26 is an aspect in which the current manufacturing method is adopted, and since a high spring limit value is not obtained because the material surface is mechanically polished after aging annealing, a good spring property was not realized. Therefore, excellent results were not obtained in the comprehensive evaluation for each comparative example.

[Examination of the production method according to claim 6 of the present invention]
The Example regarding the manufacturing method of Claim 6 of this invention is demonstrated. For each of Invention Examples 27 to 29 and Comparative Examples 30 to 32, the results shown in Table 9 were obtained under the aging treatment conditions, surface treatment conditions and strain relief annealing conditions shown in Table 8.

  As shown in Table 8, Invention Examples 27 to 29 are obtained by performing chemical polishing / mechanical polishing after aging annealing and then performing strain relief annealing. As is apparent from Table 9, in Invention Examples 27 to 29, the spring limit value was recovered by removing the residual stress generated in the outermost layer of the material by mechanical polishing, so that good spring properties were realized. Further, in these inventive examples 27 to 29, since the surface oxide film of the material was removed by chemical polishing, good solder wettability could also be realized. Therefore, excellent results were obtained in the comprehensive evaluation for each of the inventive examples. On the other hand, in Comparative Example 30, since the residence time in the furnace was short, residual stress remained on the surface, the spring limit value was not recovered, and excellent spring properties could not be obtained. In Comparative Example 31, the residence time in the furnace was long, so the spring limit value recovered to the proof stress level, but the proof stress itself decreased. Further, Comparative Example 32 is an aspect in which the current manufacturing method is adopted, and a high spring limit value cannot be obtained because the material surface is subjected to mechanical polishing after aging annealing, so that good spring properties were not realized. Therefore, excellent results were not obtained in the comprehensive evaluation for each comparative example.

Claims (6)

Ni 1.0-4.5 mass%, Si 0.3-1.5 mass%, Mg 0.05-0.3 mass%, Zn, Sn, Fe, Ti, Zr, A copper-based alloy containing 0.05 to 2.0% by mass in total of one or more of Cr, Al, P, Mn, Ag, or Be, with the balance being Cu and inevitable impurities. A Cu-Ni-Si alloy having a 2% yield strength of 500 MPa or more, a difference between a 0.2% yield strength and a spring limit value of 100 MPa or less, and an oxide film thickness of 10 nm or less. Ni 1.0-4.5 mass%, Si 0.3-1.5 mass%, Mg 0.05-0.3 mass%, Zn, Sn, Fe, Ti, Zr, A copper-based alloy containing 0.05 to 2.0% by mass in total of one or more of Cr, Al, P, Mn, Ag, or Be, with the balance being Cu and inevitable impurities. A Cu-Ni-Si alloy having a 2% proof stress of 500 MPa or more, an absolute value of residual stress on the surface of 100 MPa or less, and an oxide film thickness of 10 nm or less. Cold rolling after solution treatment is performed, and the hydrogen concentration is 50 vol% or more, the balance is made of inert gas, the dew point is -40 ° C. or less, and it is held for 10 seconds to 15 hours in an atmosphere of 350 to 650 ° C. The Cu-Ni-Si alloy according to claim 1 or 2, wherein an aging treatment is performed by the method. Subjected to cold rolling after solution heat treatment, a pressure is 10 -2 ^Pa or less, according to claim 1 or characterized by applying aging treatment by holding for 10 seconds to 15 hours in an atmosphere is 300 to 650 ° C. 2. Cu—Ni—Si alloy according to 2. After the solution treatment, cold rolling is performed, Cu plating with a thickness of 0.5 to 10 μm is applied to the surface, and then an aging treatment is performed by holding in an atmosphere of 300 to 650 ° C. for 10 seconds to 15 hours. The Cu-plated layer is then removed by chemical polishing, and the Cu-Ni-Si alloy according to claim 1 or 2. Cold rolling after solution treatment, aging treatment is performed by holding at 300 to 650 ° C. for 10 seconds to 15 hours, and then the surface oxide layer generated during the aging treatment is removed by chemical polishing and mechanical polishing, Furthermore, strain relief annealing is performed by holding for 5 seconds to 2 minutes in an atmosphere having an H ₂ concentration of 50 vol% or more, a dew point of -40 ° C or less, and 400 to 650 ° C. Cu-Ni-Si alloy as described.

Images