JP4143662B2 - Cu-Ni-Si alloy - Google Patents

Description

  The present invention relates to a Cu—Ni—Si based alloy suitable for use in various electronic components such as lead frames, connectors, pins, terminals, relays, and switches. The present invention also relates to a method for producing the alloy. Furthermore, this invention relates to the electronic component using this alloy.

  Copper alloys for electronic materials used for electronic parts and the like are required to satisfy both high strength and high conductivity (or thermal conductivity) as basic characteristics. In addition, bending workability, stress relaxation resistance, heat resistance, plating characteristics such as heat release, solder wettability, etching workability, press punchability, and corrosion resistance are also required.

  Against this background, in recent years, as a copper alloy for electronic materials, instead of the conventional solid solution strengthened copper alloys represented by phosphor bronze, brass, etc., solid solution strengthened copper alloys in strength, conductivity and stress relaxation characteristics The amount of age-hardening type copper alloys, which are superior to the above, is increasing. In the age-hardening type copper alloy, by aging the solution-treated supersaturated solid solution, fine precipitates are uniformly dispersed, the strength of the alloy is increased, and at the same time, the amount of solid solution elements in copper is reduced. The conductivity is improved.

  Of the age-hardening copper alloys, Cu-Ni-Si alloys are copper alloys having relatively high conductivity and strength, and are one of the alloys that are currently being actively developed in the industry. In this copper alloy, strength and electrical conductivity are increased by precipitation of fine Ni—Si intermetallic particles in the copper matrix.

For example, Japanese Patent Laid-Open No. 2002-266042 (Patent Document 1) discloses a Cu—Ni—Si based alloy that achieves both high strength and bending workability. In the production of the copper alloy, the sum of the cold rolling processing ratios before and after the aging treatment should be 40% or less, and in the solution treatment, the heating conditions are selected so that the grain size of the recrystallized grains is 5 to 15 μm. It is disclosed that the aging treatment should be performed at 440 to 500 ° C. for 30 to 300 minutes.
The copper alloy specifically disclosed in this document does not generate cracks by W-bending, and the tensile strength is 520 MPa at the highest conductivity of 53% IACS, and the highest tensile strength is 710 MPa. And the conductivity is 46% IACS (see Table 2 in the Examples).

Japanese Patent Laid-Open No. 2001-207229 (Patent Document 2) describes an example of an attempt to develop a Cu—Ni—Si alloy having good bending workability in addition to strength and conductivity. According to this document, the weight ratio between Ni and Si in the alloy is made closer to the concentration of Ni ₂ Si, which is an intermetallic compound, that is, the weight ratio between Ni and Si is set to Ni / Si = 3-7. It is described that a good conductivity can be obtained. Moreover, after adding any one or more of Fe and / or Zr, Cr, Ti, and Mo to the Cu—Ni—Si-based alloy and adjusting the components, Mg, Zn, Sn, Al, P, It is described that a material suitable as a copper alloy for electronic materials can be provided by containing Mn, Ag or Be.
The copper alloy specifically disclosed in this document does not generate cracks by bending at 90 ° (not 180 ° bending), and has a tensile strength of 640 MPa at 56% IACS, which has the highest conductivity. When the strength is 698 MPa, the conductivity is 44% IACS (see Table 1 in the Examples). Moreover, in the Example of this literature, the workability of the cold rolling performed before and after the aging treatment is 60% and 37.5% (97.5% in total), respectively.

Japanese Patent Laid-Open No. 61-194158 (Patent Document 3) discloses Cu-Ni- having a conductivity of 60% IACS or higher, high strength, excellent stiffness strength, repeated bendability, and high heat resistance. Si-based alloys are disclosed. This document contains Mn: 0.02 to 1.0 wt%, Zn: 0.1 to 5.0 wt%, Mg: 0.001 to 0.01 wt% as additive elements, and Cr, Ti, and Zr. It is described that one or more selected from among them should be contained in an amount of 0.001 to 0.01 wt%.
Examples of this document include tensile strength 51.0 kgf / mm ² (500 MPa), conductivity 67.0% IACS data and tensile strength 62.0 kgf / mm ² (593 MPa), conductivity 64.0%. IACS data and are disclosed (see Table 2).
The Cu—Ni—Si alloy is cold-rolled from 10 mm after hot rolling to 0.25 mm without recrystallization annealing. In this case, the rolling degree is remarkably high at 97.5%, and it is assumed that the bending workability is extremely deteriorated. In addition, although annealing at 450 ° C. is performed during and after cold rolling, in the case of a Cu—Ni—Si based alloy, although the precipitation reaction proceeds at this temperature, recrystallization does not proceed.

Japanese Patent Application Laid-Open No. 11-222641 (Patent Document 4) adds a specific amount of Sn, Mg, or Zn, restricts the S and O contents, and makes the grain size more than 1 μm and 25 μm or less. Discloses a Cu—Ni—Si alloy having excellent mechanical properties, conductivity, stress relaxation properties and bending workability. In addition, this document describes that recrystallization should be performed at 700 to 920 ° C. after cold working in order to adjust the crystal grain size to the above range.
In the examples of this document, a Cu—Ni—Si based alloy capable of 180 ° tight bending with a tensile strength of 610 to 710 MPa is disclosed. The conductivity of this alloy is 31-42% IACS, and the stress relaxation rate when heated at 150 ° C. for 1000 hours is 14-22%.

Japanese Patent No. 3520034 (Patent Document 5) contains a specific amount of Mg, Sn, Zn, and S, has a crystal grain size of more than 0.001 mm and 0.025 mm or less, and parallel to the final plastic working direction. The ratio (a / b) of the major axis a of the crystal grain in the cross section and the major axis b of the crystal grain in the cross section perpendicular to the final plastic working direction is 0.8 or more and 1.5 or less, and bending workability and stress relaxation characteristics are A Cu—Ni—Si based alloy characterized by being excellent is disclosed.
In the examples of this document, a Cu—Ni—Si based alloy having a tensile strength of 685 to 710 MPa, an electrical conductivity of 32 to 40% IACS, and capable of 180 ° contact bending is disclosed.

In addition, as a recent study on improving characteristics of Cu—Ni—Si based alloys, Non-Patent Documents 1 and 2 report techniques for improving strength and bendability by paying attention to a precipitation-free zone (PFZ). The non-precipitation zone is a band-like region that is formed in the vicinity of a grain boundary by grain boundary reaction type precipitation (discontinuous precipitation) during aging and does not have fine precipitates. Since there are no fine precipitates that contribute to the strength, when no external force is applied, the precipitate-free zone preferentially undergoes plastic deformation, leading to a decrease in tensile strength and bending workability.
According to Non-Patent Document 1, the addition of P and Sn and two-stage aging are effective for suppressing the precipitation-free zone. Regarding the latter, it is described that the strength was greatly increased without impairing elongation by adding preliminary aging of 250 ° C. × 48 h before normal aging of 450 ° C. × 16 h. Specifically, a Cu—Ni—Si based alloy having a tensile strength of 770 to 900 MPa and a conductivity of 34 to 36% IACS is disclosed.
Non-Patent Document 2 describes that the width of PFZ increases as the aging time increases.
JP 2002-266042 A JP 2001-207229 A JP-A-61-194158 Japanese Patent Application Laid-Open No. 11-222641 Japanese Patent No. 3520034 Chihiro Watanabe, Masaru Miyakoshi, Fumiya Nishijima, Ryoichi Monzen: "Improvement of mechanical properties of Cu-4.0mass% Ni-0.95mass% Si-0.02mass% P alloy", copper and copper alloy, Japan Copper and Brass Association 2006, Vol. 45, No. 1, p. 16-22 Ito Goro, Suzuki Toshiaki, ▲ To ▼ Keihei, Yamamoto Yoshinori, Ito Nobuhide, “Effects of Ni, Si Content and Aging Conditions on the Bendability of Cu-Ni-Si Alloy Sheets”, Copper and Copper Alloy, Japan Copper and Brass Association, 2006, Vol. 45, No. 1, p. 71-75

  As described above, various methods have been developed for improving the properties of Cu-Ni-Si alloys, but until now the main method has been to improve the properties by adding other alloy elements. It was. However, in recent years, there has been a demand for reducing the amount of elements added to alloys due to recyclability problems.

In addition, with the recent progress of high integration, miniaturization, and thinning of electronic components, improvement in the electrical conductivity of Cu—Ni—Si based alloys is required. This is because the temperature rise of the component due to Joule heat increases as the cross-sectional area of the energized portion decreases.
ΔT = J ² · L ² / (2 ・ E ・ H ・ S ² )
Here, ΔT is the temperature rise, J is the current, E is the electrical conductivity, H is the thermal conductivity, and L and S are the length and the cross-sectional area of the current-carrying part, respectively. Since H is proportional to E, the temperature rise is inversely proportional to the square of conductivity.
On the other hand, when the cross-sectional area of a part is reduced, the spring force is reduced in applications such as connectors, and therefore, characteristics relating to the spring force such as tensile strength and stress relaxation resistance are also emphasized. Therefore, it is difficult to reduce the tensile strength and the stress relaxation resistance instead of improving the conductivity. Similarly, since the processing of parts becomes complicated with the miniaturization of parts, it is difficult to allow a decrease in bendability.

Accordingly, an object of the present invention is to provide a Cu—Ni—Si based alloy for electronic materials that does not contain other alloy elements as much as possible and has improved conductivity, strength, bendability and stress relaxation characteristics. That is.
Moreover, another subject of this invention is providing the manufacturing method of this Cu-Ni-Si type alloy.
Still another object of the present invention is to provide a rolled copper product and an electronic component using the Cu—Ni—Si based alloy.

  The present inventor has intensively studied to solve the above problems, and in the process of manufacturing a Cu-Ni-Si alloy with as few impurities as possible, specially in the temperature increase rate of the aging treatment, the maximum temperature of the material, and the aging time. Cu-Ni-Si that has excellent electrical conductivity, tensile strength, stress relaxation resistance and bendability by optimizing the solution treatment conditions and the rolling process degree before and after the aging treatment It has been found that a system alloy can be obtained.

In one aspect, the present invention completed on the basis of the above knowledge includes 1.2 to 3.5% by mass of Ni, and Si concentration of 1/6 to 1/4 (% by mass) with respect to the Ni concentration (mass%). It is a Cu—Ni—Si alloy characterized by containing Cu and the balance of Cu and impurities in a total amount of 0.05% by mass or less and having the following characteristics.
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less

Further, when Zn is added to the above alloy, the electrical conductivity is slightly lowered, but since the effect of improving the heat-resistant peelability of Sn plating is great, when the particularly good heat-resistant peelability of Sn plating is required, the alloy has a value of 0. Zn may be added up to 5 mass%.
Therefore, in another aspect of the present invention, Ni having a concentration (mass%) of 1/6 to 1/4 with respect to Ni and Ni concentration (mass%) of 1.2 to 3.5 mass%, 0.5 It is a Cu-Ni-Si based alloy characterized in that it contains Zn by mass or less, the balance is composed of Cu and impurities in a total amount of 0.05 mass% or less, and has the following characteristics.
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less (E) Heat release resistance: Sn plating heat release No plating peeling after test

In one embodiment, the copper alloy according to the present invention has an average grain size in the direction perpendicular to the rolling direction of the crystal grains in the metal structure of the cross section parallel to the rolling surface, and an average grain in the direction parallel to the rolling direction. When the diameter is b,
a = 1 to 15 μm, b / a = 1.05 to 1.67
Furthermore, the average width of the precipitation-free zone in the metal structure is 10 to 100 nm.

  Moreover, this invention is another one side. WHEREIN: It is a copper elongation product using the said copper alloy.

  Moreover, this invention is another one side. WHEREIN: It is electronic components, such as a lead frame using the said copper alloy, a connector, a pin, a terminal, a relay, a switch, and a foil material for secondary batteries.

In addition, in another aspect of the present invention, in the method for producing a Cu—Ni—Si alloy including sequentially performing the steps of solution treatment, cold rolling, aging treatment, and cold rolling, each step is performed as follows. The process for producing a Cu—Ni—Si based alloy is characterized in that it is carried out under the following conditions.
(Solution Treatment) The average crystal grain size is adjusted to a range of 1 to 15 μm.
(Aging treatment) The maximum temperature of the material during the heat treatment is set to 550 ° C. or lower, and the material is held in a temperature range of 450 to 550 ° C. for 5 to 15 hours. Moreover, the average temperature increase rate of the material in each temperature area of 200-250 degreeC, 250-300 degreeC, and 300-350 degreeC in a temperature rising process shall be 50 degrees C / h or less.
(Cold rolling) The total of the rolling degree in cold rolling before aging and the rolling degree in cold rolling after aging is made 5 to 40%.

  According to the present invention, no alloying elements other than Ni and Si are added, or no alloying elements other than Ni, Si and Zn are added, and improved conductivity, strength, bendability and stress relaxation. It is possible to provide a Cu—Ni—Si based alloy for electronic materials having characteristics.

Alloy composition In the copper alloy according to the present invention, the Si concentration (mass%) is in the range of 1/6 to 1/4 of the Ni concentration (mass%). This is because good conductivity (for example, 55% IACS or more) cannot be obtained if Si is out of this range. A preferable Si range is 1 / 5.5 to 1 / 4.2 of Ni, and a more preferable Si range is 1 / 5.2 to 1 / 4.5 of Ni.

  Ni is 1.2 to 3.5% by mass. When Ni is less than 1.2% by mass, good tensile strength (for example, 550 MPa or more) cannot be obtained. If Ni exceeds 3.5% by mass, good bending workability cannot be obtained (for example, cracking occurs in 180-degree contact bending). A preferable Ni concentration is 1.4 to 2.5% by mass, and a more preferable range of Ni is 1.5 to 2.0% by mass.

  Conventionally, the main characteristic is to improve the alloy characteristics by adding various alloy elements to the Cu—Ni—Si based alloy. However, other alloy elements (also referred to as impurities in the present invention) are used in accordance with the object of the present invention. ) As much as possible. Further, when other alloy elements are significantly contained, sufficient conductivity tends not to be obtained, and a Cu—Ni—Si alloy having strength, conductivity, bendability and stress relaxation characteristics is obtained. Proved to be difficult. Therefore, in the present invention, the total amount of impurities is controlled to 0.05% by mass or less, preferably 0.02% by mass or less, more preferably 0.01% by mass or less. Therefore, in a preferred embodiment of the present invention, alloy elements other than Ni and Si are not present in the Cu—Ni—Si based alloy except for inevitable impurities.

  However, since Zn has a relatively small effect on conductivity and has a large effect on improving the heat-resistant peelability of Sn plating, Zn may be added when particularly good heat-resistant peelability of Sn plating is required. . The decrease in conductivity per 0.1% by mass of Zn is about 0.5% IACS. However, when Zn exceeds 0.5% by mass, it becomes difficult to obtain sufficient electrical conductivity (for example, 55% IACS or more). When Zn is less than 0.05% by mass, the effect of improving the heat-resistant peelability of Sn plating is improved. Is hardly recognized. Therefore, a preferable Zn concentration is 0.05 to 0.5% by mass, and a more preferable Zn concentration is 0.1 to 0.3% by mass.

When the average grain size in the direction perpendicular to the rolling direction of the crystal grains is a, and the average grain size in the direction parallel to the rolling direction is b,
a = 1 to 15 μm, b / a = 1.05 to 1.67
And When a is less than 1 μm, a good stress relaxation rate cannot be obtained (for example, more than 30%). Further, Ni ₂ Si that precipitates during aging is insufficient, and good tensile strength cannot be obtained. On the other hand, when a exceeds 15 μm, good bending workability cannot be obtained (for example, cracking occurs in 180-degree contact bending). Preferably, a = 2 to 10 μm, and more preferably a = 2 to 5 μm when importance is attached to bendability, and more preferably 5 to 10 μm when importance is given to strength and stress relaxation resistance.
When b / a is less than 1.05, good tensile strength cannot be obtained (for example, less than 550 MPa). On the other hand, if b / a exceeds 1.67, good bendability cannot be obtained (for example, cracking occurs in 180-degree contact bending). Preferably it is b / a = 1.10-1.40, More preferably, it is b / a = 1.20-1.30.

  Moreover, in the metal structure of a cross section parallel to the rolling surface, the average width of the precipitation-free zone in the metal structure is 10 to 100 nm. If the width of the precipitation-free zone is increased, sufficient bendability, stress relaxation resistance and tensile strength cannot be obtained. When the width of the precipitation-free zone exceeds 100 nm, good bendability cannot be obtained (for example, cracking occurs by 180-degree contact bending), and good stress relaxation rate cannot be obtained (for example, more than 30%). The width of the precipitation-free zone is preferably as narrow as possible. However, if it is attempted to suppress this to less than 10 nm, good conductivity (for example, 55% IACS or more) can be obtained even if the characteristic aging treatment of the present invention described later is performed. I can't. Therefore, the preferable average width of the precipitation-free zone for improving the electrical conductivity, bending workability and stress relaxation resistance in a balanced manner is 20 to 90 nm, and the more preferable average width of the precipitation-free zone is 30 to 80 nm.

  In addition, by adjusting to the said structure | tissue, the fine Ni-Si type | system | group intermetallic compound particle | grains which have a particle size of nm order which contributes to an intensity | strength raise | generate also with high frequency.

Alloy Characteristics The copper alloy according to the present invention has the following characteristics in one embodiment.
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by 180-degree contact bending (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less (illustratively 15-30%)

In a preferred embodiment, the copper alloy according to the present invention has the following characteristics.
(A) Conductivity: 56-60% IACS
(B) Tensile strength: 600 to 660 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 25% or less (illustratively 15-25%)

In another preferred embodiment, the copper alloy according to the present invention has the following characteristics.
(A) Conductivity: 60-62% IACS
(B) Tensile strength: 600 to 610 MPa
(C) Bendability: No cracks are generated by 180-degree contact bending (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 25% or less (exemplarily 20 to 25%)

In another embodiment, the copper alloy according to the present invention to which Zn is added can simultaneously achieve the following characteristics.
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by 180-degree contact bending (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less (illustratively 15-30%)
(E) Heat-resistant peelability: No plating peeling is observed after Sn plating heat-resistant peeling test

In a preferred embodiment, the copper alloy according to the present invention to which Zn is added can simultaneously achieve the following characteristics.
(A) Conductivity: 56-60% IACS
(B) Tensile strength: 600 to 660 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 25% or less (illustratively 15-25%)
(E) Heat-resistant peelability: No plating peeling is observed after Sn plating heat-resistant peeling test

In another preferred embodiment, the copper alloy according to the present invention added with Zn can simultaneously achieve the following characteristics.
(A) Conductivity: 56-60% IACS
(B) Tensile strength: 640 to 660 MPa
(C) Bendability: No cracking occurs due to 180-degree contact bending (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 20% or less (illustratively 15-20%)
(E) Heat-resistant peelability: No plating peeling is observed after Sn plating heat-resistant peeling test

The “Sn plating heat-resistant peeling test” refers to a method for evaluating Sn plating peeling of a test piece in the following manner.
A 0.3 μm thick Cu base plating and a 1 μm thick Sn plating are applied to the test piece and heated at 300 ° C. for 20 seconds as a reflow treatment.
Then, 90 ° bending and bending back with a bending radius of 0.5 mm in the WAY (direction in which the bending axis is perpendicular to the rolling direction) and bending back (90 ° bending is performed once and again) are performed on the inner surface of the bending inner part. Adhesive tape (masking tape for plating, substrate: polyester, adhesive strength: 3.49 N / cm (180 ° peel), example: # 851A manufactured by Sumitomo 3M) is applied and peeled off.
The inner surface of the bending inner surface is observed with an optical microscope (magnification 20 times), and the presence or absence of plating peeling is evaluated.

  As far as the inventor knows, the present invention has the same composition as the copper alloy according to the present invention and has characteristics comparable to the copper alloy according to the present invention, that is, conductivity, strength, bending workability and stress relaxation characteristics. No example has been achieved in a balanced manner to this level.

Manufacturing method In a general manufacturing process of a Cu—Ni—Si based copper alloy, first, an atmospheric melting furnace is used to melt raw materials such as electrolytic copper, Ni and Si under a charcoal coating, and this molten metal is cast into an ingot. . Thereafter, hot rolling is performed, and cold rolling and heat treatment are repeated to finish a strip or foil having a desired thickness and characteristics (for example, a thickness of 0.08 to 0.64 mm). Heat treatment includes solution treatment and aging treatment. In the solution treatment, heating is performed at a high temperature of about 700 to about 1000 ° C., and a coarse Ni—Si compound generated during casting or the like is dissolved in the Cu matrix, and at the same time, the Cu matrix is recrystallized. The solution treatment may be combined with hot rolling. In the aging treatment, heating is performed for 1 hour or more in a temperature range of about 350 to about 550 ° C., and Ni and Si compounds dissolved in the solution treatment are precipitated as fine particles. This aging treatment increases strength and conductivity. In order to obtain higher strength, cold rolling may be performed before and / or after aging. Moreover, when performing cold rolling after aging, strain relief annealing (low temperature annealing) may be performed after cold rolling.

In the aging treatment, when the heating temperature is kept constant and the heating time is changed, the conductivity increases monotonously with time. On the other hand, the tensile strength generally reaches a maximum at a certain time and then decreases with time. Even when the temperature is changed at a constant time, the conductivity increases monotonously with the temperature rise, and the tensile strength decreases after showing the maximum value. Aging performed under conditions where the tensile strength is maximized is called peak aging, and aging performed in a region where the tensile strength decreases with time or temperature is called overaging.
In order to increase the electrical conductivity of the Cu-Ni-Si alloy, overaging may be performed. That is, if an appropriate aging time and temperature are selected, good conductivity (for example, about 60% IACS) can be obtained relatively easily. However, the tensile strength decreases (for example, up to about 500 MPa), and not only that, but also stress relaxation resistance and bendability deteriorate. After that, if cold rolling with a high degree of work is performed, the tensile strength is recovered to about 600 MPa, but the bendability is remarkably deteriorated due to work strain, and the improvement of stress relaxation resistance cannot be expected. The conventional highly conductive Cu—Ni—Si based alloy disclosed in Patent Document 3 and the like was basically a technology to which this overaging was applied.

  The present inventor has conducted studies to improve the electrical conductivity, strength, bendability and stress relaxation resistance in a well-balanced manner. Excellent electrical conductivity, tensile strength and stress resistance by applying special conditions to temperature rate, maximum material temperature and aging time, and further optimizing solution treatment conditions and rolling degree before and after aging treatment It has been found that a Cu—Ni—Si based alloy having both relaxation properties and bendability can be obtained.

  Therefore, in order to produce the copper alloy according to the present invention, a series of characteristic flows is necessary in the steps after the solution treatment, that is, cold rolling (intermediate rolling), aging treatment, and cold rolling (final rolling). It becomes. In particular, it is important to apply a characteristic aging treatment.

(Aging treatment)
As the aging conditions, the rate of temperature rise, the maximum temperature reached by the material, the time during which the material is held at a temperature of 450 to 550 ° C., and the rate of temperature rise of the material are specified.
(A) Rate of temperature rise: When the temperature of the material is raised gradually, fine precipitation nuclei are formed in the crystal grains during the temperature rise process, and subsequent grain boundary reaction type precipitation, that is, growth of no precipitation zone is suppressed. Therefore, even if aging is performed for a long time in order to obtain a high conductivity, the precipitation-free zone does not grow so much, and therefore mechanical properties (strength, bending, stress relaxation, etc.) do not deteriorate. That is, conventionally, when the aging time is shortened to suppress the precipitation-free zone in order to improve the mechanical characteristics, high conductivity cannot be obtained. In addition, when the aging time was increased to improve the conductivity, no precipitate zone grew and good mechanical properties could not be obtained. It can be said that the present invention has a great significance in satisfying such conflicting characteristics. In addition, about the said mechanism estimated by this invention, this invention is not limited.
Specifically, it is necessary to set the average temperature rising rate of the material in each temperature section of 200 to 250 ° C., 250 to 300 ° C., and 300 to 350 ° C. to 50 ° C./h or less. From the viewpoint of production efficiency, the average heating rate is preferably 10 ° C./h or more. Typically, the average heating rate is 20 to 40 ° C./h.
Here, even by the addition of the 250 ° C. × 48 h preliminary heat treatment described in Non-Patent Document 1, a certain degree of precipitation-free zone suppression effect can be obtained, but the production efficiency is significantly lowered by the addition of the preliminary heat treatment. The method of temperature increase rate control of the present invention is an industrially extremely effective method that hardly reduces the production efficiency.

(A) Maximum material temperature: 550 ° C. or less. This is because when the temperature exceeds 550 ° C., the width of the precipitation-free zone becomes wide (for example, exceeds 100 nm), no matter how the heating rate is controlled. Preferably it is 530 degrees C or less, More preferably, it is 500 degrees C or less. On the other hand, if the maximum temperature reached is less than 450 ° C., good conductivity cannot be obtained. Therefore, the maximum temperature reached is preferably 450 ° C. or higher, more preferably 480 ° C. or higher.

(C) Holding time at 450 to 550 ° C .: 5 to 15 hours. When heating for less than 5 hours, the width of the precipitation-free zone becomes narrow (for example, less than 10 nm), but sufficient conductivity cannot be obtained even if the rate of temperature increase is suppressed. When it exceeds 15 hours, the width of the precipitation-free zone becomes wide (for example, it exceeds 100 nm). A more preferable time considering production efficiency is 6 to 10 hours.

(Solution treatment)
In the solution treatment, the average crystal grain size is adjusted to a range of 1 to 15 μm. Since the average crystal grain size after solution treatment is substantially equal to a in the product stage defined above, if the average crystal grain size here is less than 1 μm, a obtained from the metal structure of the product is less than 1 μm. When the average crystal grain size here exceeds 15 μm, a exceeds 15 μm. A more preferable average crystal grain size is 2 to 10 μm, and a = 2 to 10 μm is obtained.
The heating temperature and heating conditions of the solution treatment for obtaining the crystal grain size are well known and can be appropriately set by those skilled in the art. For example, the material may be set at an appropriate temperature of 700 to 800 ° C. The crystal grain size is obtained by holding for an appropriate time of 5 to 600 seconds and then quickly cooling with air or water.

(Cold rolling)
The total of the degree of intermediate rolling and the degree of final rolling is 5 to 40%. When the total workability is less than 5%, b / a obtained from the metal structure of the product is less than 1.05, and when the total workability exceeds 40%, b / a exceeds 1.67. A more preferable total processing degree is 10 to 25%, and b / a = 1.10 to 1.40 is obtained. It should be noted that there is no problem even if the rolling degree of one of the intermediate rolling and the final rolling is zero.
The working degree R is defined by an equation of R (%) = (to-t) / to × 100 (to: thickness before rolling, t: thickness after rolling). “Total R _sum (%) of degree of processing” is R _sum (%) = (to−t ₁ ) / when the thickness is changed from t ₀ to t _{1 in} the intermediate rolling and from t ₁ to t ₂ in the final rolling. to × 100 + (t ₁ −t ₂ ) / t ₁ × 100.

(Strain relief annealing)
After the final cold rolling, strain relief annealing may be performed for the purpose of improving the spring limit value and the like. The strain relief annealing may be performed at a low temperature for a long time (eg, 300 ° C. × 30 minutes) or at a high temperature for a short time (eg, 500 ° C. × 30 seconds). If the temperature is too high or the time is too long, the drop in tensile strength will increase. It is preferable to select the conditions by setting the amount of decrease in tensile strength to 10 to 50 MPa.

  Even if the copper alloy according to the present invention is subjected to a surface treatment such as tin plating or gold plating, the effect of the present invention is maintained.

Therefore, in a preferred embodiment of the method for producing a copper alloy according to the present invention,
-Ni of 1.2 to 3.5 mass%, Si of 1/6 to 1/4 concentration (mass%) relative to Ni concentration (mass%), and 0.5 mass% or less of Zn as an optional component A step of melt casting an ingot composed of impurities with a balance of Cu and a total amount of 0.05% by mass or less,
-A hot rolling process;
-A cold rolling process;
-A solution treatment step for adjusting the average crystal grain size in the range of 1 to 15 µm;
A cold rolling process performed at a working degree of 0 to 40%;
-The maximum temperature of the material during the heat treatment is set to 550 ° C or lower, the material is held in the temperature range of 450 to 550 ° C for 5 to 15 hours, and 200 to 250 ° C, 250 to 300 ° C and 300 to 350 ° C in the temperature rising process. An aging treatment step in which the average temperature rising rate of the material in each temperature section is 50 ° C./h or less
A cold rolling step performed at a working degree of 0 to 40% (however, the total working degree with the cold rolling performed before the aging treatment is 5 to 40%);
-Optional strain relief annealing process;
Are performed in this order.

  A person skilled in the art will understand that steps such as grinding, polishing, and shot blast pickling for removing oxide scale on the surface can be appropriately performed between the above steps.

  The Cu—Ni—Si based alloy of the present invention can be processed into various copper products, such as plates, strips, tubes, bars and wires, and the Cu—Ni—Si based copper alloy according to the present invention is a connector, It can be particularly suitably used as a conductive spring material such as terminals, relays and switches, and as a lead frame material for semiconductor devices such as transistors and integrated circuits.

  Hereinafter, examples for better understanding of the present invention and its advantages will be described, but the present invention is not limited thereto.

Using a high frequency induction furnace, 2 kg of electrolytic copper was dissolved in a graphite crucible having an inner diameter of 60 mm and a depth of 200 mm. After covering the surface of the molten metal with a piece of charcoal, a predetermined amount of Ni, Si, and Zn as necessary were added, and the molten metal temperature was adjusted to 1200 ° C. Next, the molten metal was cast into a mold to produce an ingot having a width of 60 mm and a thickness of 30 mm. Concerning elements other than Ni, Si and Zn, that is, impurities, the concentration in the ingot was determined by semi-quantitative analysis of all elements by glow discharge-mass spectrometry, and the total amount was about 0.01% by mass. As elements having relatively high concentrations, there were Fe (0.005% by mass), S (0.001% by mass), and C (0.001% by mass).
The ingot was heated at 950 ° C. for 3 hours, and then hot-rolled to a thickness of 8 mm, and the oxidized scale on the surface was ground and removed with a grinder. Then, processing and heat treatment were performed in the order of cold rolling, solution treatment, cold rolling (intermediate rolling), aging treatment, cold rolling (final rolling), and strain relief annealing. The degree of processing in each rolling and the plate thickness during heat treatment were adjusted so that the plate thickness after final rolling was 0.25 mm. After solution treatment, after aging treatment and after stress relief annealing, in order to remove the surface oxide film generated by heat treatment, pickling with 10% sulfuric acid-1% by weight hydrogen peroxide solution and machine using # 1200 emery paper Polishing was performed sequentially.

In the solution treatment, the sample was inserted into an electric furnace adjusted to a predetermined temperature for a predetermined time, then immediately removed from the electric furnace and air-cooled.
In the aging treatment, the sample was heated under various temperature conditions using an electric furnace. During the aging treatment, the sample was contacted with a thermocouple, and the change in the sample temperature was measured.
In strain relief annealing, the sample was inserted into an electric furnace at 300 ° C. for 30 minutes, then taken out of the electric furnace and air-cooled. When the final rolling was not performed, this strain relief annealing was not performed.

The following evaluation was performed about the obtained sample.
(1) Crystal grain shape The structure of the cross section parallel to the rolling surface of the sample after solution treatment and the sample after strain relief annealing (after final rolling for those not subjected to strain relief annealing) (hereinafter referred to as product) Was observed. The rolled surface was finished to a mirror surface by mechanical polishing and electrolytic polishing, and then crystal grain boundaries were revealed by etching, and a structure photograph was taken. As the etching solution, an aqueous solution in which ammonia water and hydrogen peroxide water were mixed was used, and an optical microscope or a scanning electron microscope was appropriately used for taking a structure photograph. On the other hand, when the crystal grain size is small and it is difficult to discriminate the crystal grain boundary by etching, an orientation map image is taken by an EBSP (Electron Backscattering Pattern) method using a mirror-finished sample after electropolishing, and the crystal grain shape is used. Was measured.
On the structure photograph, three straight lines were arbitrarily drawn in the direction perpendicular to the rolling direction, and the number of crystal grains cut by the straight line was determined. A value obtained by dividing the length of the straight line by the number of crystal grains was defined as a. Similarly, three straight lines are drawn in the direction parallel to the rolling direction, the number of crystal grains cut by the straight line is obtained, and the value obtained by dividing the length of the straight line by the number of crystal grains is defined as b.
For the sample after solution treatment, the value of (a + b) / 2 was determined and this was used as the average crystal grain size. For the product, the value of b / a was determined.

(2) Width of precipitation-free zone For the cross section parallel to the rolling surface, the vicinity of the crystal grain boundary of the product was observed with a transmission electron microscope at a magnification of about 100,000 times, and the average width of the precipitation-free zone (any 30 locations) The average value was determined.
(3) Electrical conductivity The electrical conductivity of the product was measured by a four-terminal method in accordance with JIS H 0505.
(4) Tensile strength About the product, a JIS13B test piece was prepared using a press so that the tensile direction was parallel to the rolling direction. The test piece was subjected to a tensile test according to JIS-Z2241, and the tensile strength was determined.
(5) Bending workability A strip-shaped sample having a width of 10 mm is taken from the product, and in accordance with JIS Z 2248, Good Way (GW, the direction in which the bending axis is perpendicular to the rolling direction) and Bad Way (BW, the bending axis is rolled). 180 ° contact bending test in a direction parallel to the direction). About the sample after a bending, the presence or absence of the crack was observed from the surface and cross section of the bending part, and the case where a crack was not observed was evaluated as (circle) and the case where a crack was recognized as x. A crack having a depth exceeding 10 μm was regarded as a crack.
(6) Stress relaxation rate A strip-shaped test piece having a width of 10 mm and a length of 100 mm was collected from the product so that the longitudinal direction of the test piece was parallel to the rolling direction. As shown in FIG. 1-A, with the position of l = 25 mm as the working point, the specimen is given a deflection of yo, corresponding to 80% of 0.2% yield strength (rolling direction, measured according to JIS-Z2241). Stress (σo) was applied. yo was determined by the following equation.
yo = (2/3) · l ² · σo / (E · t)
Here, E is Young's modulus, and t is the thickness of the sample. After unloading after heating at 150 ° C. for 1000 hours, the amount of permanent deformation (height y) was measured as shown in FIG. 1-B, and the value of y / yo × 100 was calculated as the stress relaxation rate (%).
(7) Sn plating heat-resistant peeling test After performing alkaline degreasing and pickling with 10% sulfuric acid, after applying Cu underplating with a thickness of 0.3 μm, Sn plating with a thickness of 1 μm is applied, and 300 is used as a reflow treatment. Heat at 20 ° C. for 20 seconds. The plating conditions are as follows.
(Cu base plating)
-Plating bath composition: copper sulfate 200 g / L, sulfuric acid 60 g / L
・ Plating bath temperature: 25 ℃
・ Current density: 5 A / dm ²
(Sn plating)
-Plating bath composition: stannous oxide 41 g / L, phenolsulfonic acid 268 g / L, surfactant 5 g / L
・ Plating bath temperature: 50 ℃
・ Current density: 9A / dm ²
A strip test piece having a width of 10 mm was taken from the sample after reflow and heated in the atmosphere at a temperature of 150 ° C. for 1000 hours. Thereafter, 90 ° bending and bending back (one round-trip of 90 ° bending) with a bending radius of 0.5 mm were performed on Good Way (GW, the direction in which the bending axis is orthogonal to the rolling direction), and further adhered to the inner surface of the bending A tape (# 851A manufactured by Sumitomo 3M) was applied and peeled off. And the bending inner peripheral part surface was observed with the optical microscope (magnification 20 times), and the presence or absence of plating peeling was investigated. A case where no plating peeling was observed was evaluated as ◯. The case where the plating peeled in a planar shape was evaluated as x. The case where the plating peeled off locally was evaluated as Δ. In practical applications, there is no problem even if the level is Δ.

Test example 1
Explain the effect of manufacturing conditions on the microstructure and properties of products. The component of the sample was a Cu-1.60 mass% Ni-0.35 mass% Si alloy, and it was processed into a product by changing the solution treatment conditions, the aging treatment conditions, and the rolling conditions.
(Representative invention example and conventional example)
FIG. 2 is a temperature chart of a typical aging treatment, the broken line indicates the temperature of the atmosphere in contact with the sample, and the solid line indicates the sample temperature.
In (a), after inserting material in the electric furnace which adjusted temperature to 200 degreeC and hold | maintaining for 1 hour, the furnace temperature is raised to 350 degreeC over 200 hours from 200 degreeC. Next, after raising the furnace temperature to 500 ° C. over 1 hour and holding it for 8 hours, it is taken out from the electric furnace and air-cooled.
In (b), after inserting the material into an electric furnace whose temperature was adjusted to 200 ° C. and holding it for 1 hour, the furnace temperature was raised from 200 ° C. to 250 ° C. over 3 hours and then raised to 300 ° C. over 2 hours. The temperature is raised to 350 ° C. over 1 hour. Next, after raising the furnace temperature to 490 ° C. over 1 hour and holding it for 10 hours, it is taken out from the electric furnace and air-cooled.
(C) shows a case where the material is inserted into an electric furnace whose temperature is adjusted to 500 ° C., and is taken out from the electric furnace after 9 hours and air-cooled. This corresponds to a conventional heat treatment procedure.

  For each aging pattern in FIG. 2, the average rate of temperature increase at 200 → 250 ° C., 250 → 300 ° C. and 300 → 350 ° C., the highest temperature reached of the material, and the holding time in the temperature range of 450 to 550 ° C. were determined. Moreover, it processed into the product on the solution treatment conditions and rolling conditions of this invention, and investigated the structure | tissue and the characteristic. The results are shown in Table 1. 1-3. (A), (b), and (c) in FIG. Corresponding to 1, 2, and 3.

No. manufactured under the conditions of the present invention. 1 and 2 satisfy the metal structure and characteristics of the product defined by the present invention.
No. which is a conventional example. The temperature increase rate of No. 3 is larger than the range of the present invention. Same as 1. Since the precipitation-free zone greatly exceeded 100 nm, the tensile strength was less than 550 MPa, cracks were generated by 180-degree contact bending, and the stress relaxation rate exceeded 30%.
No. 4 is also a conventional example. In order to make the tensile strength of No. 3 higher than 550 MPa, the degree of rolling is increased. In addition to the high degree of processing, the precipitation-free zone exceeded 100 nm, and therefore, 180 degree contact bending caused severe cracking at a level at which the sample broke, and stress relaxation exceeded 30%.
No. 5 is a conventional general Cu-Ni-Si alloy. We perform peak aging and create properties that prioritize tensile strength. The bendability and stress relaxation resistance are good, but the conductivity is less than 50% IACS.

(Temperature increase rate during aging)
No. Table 2 shows data obtained when the heating rate during aging was changed with respect to 1. It can be seen that the width of the precipitation-free zone is reduced by slowing the heating rate. When the width of the precipitation-free zone is reduced, the tensile strength, bendability, and stress relaxation resistance are improved. Comparative Example No. In 9.10, the rate of temperature rise exceeded 50 ° C./h in any temperature section, so the width of the precipitation-free zone exceeded 100 nm, the tensile strength was less than 550 MPa, and cracking occurred at 180 ° contact bending. The stress relaxation rate exceeded 30%.

(Maximum temperature at aging and holding time at 450-550 ° C)
No. Table 3 shows data when the maximum temperature achieved by aging and the holding time at 450 to 550 ° C. were changed.
When the holding time at 450 to 550 ° C. becomes longer, the conductivity increases, but the precipitation-free zone becomes wider. Comparative Example No. with an aging time of less than 5 hours In No. 11, the precipitation-free zone is less than 10 nm, and the conductivity does not reach 55% IACS. Comparative Example No. with an aging time exceeding 15 hours In No. 14, the width of the precipitation-free zone exceeded 100 nm, the tensile strength was less than 550 MPa, cracking occurred at 180 ° contact bending, and the stress relaxation rate exceeded 30%.
As the maximum temperature reaches higher, the conductivity increases, but the width of the precipitation-free zone becomes wider. Comparative Example No. aging time exceeded 550 ° C. In No. 16, the width of the precipitation-free zone exceeded 100 nm, the tensile strength was less than 550 MPa, cracking occurred at 180 ° contact bending, and the stress relaxation rate exceeded 30%.

(Rolling degree)
No. Table 4 shows data when the rolling degree is changed with respect to 1. As the degree of processing increases, b / a obtained from the metal structure of the product increases, and the tensile strength increases. The total of the intermediate rolling degree and the final rolling degree is less than 5%. The b / a of 17 is less than 1.05, and the tensile strength is less than 550 MPa. The total of the intermediate rolling workability and the final rolling workability exceeded 40%. The b / a of No. 23 was larger than 1.67, the tensile strength exceeded 700 MPa, and cracking occurred in 180-degree contact bending.

(Grain size after solution treatment)
No. Table 5 shows data when the crystal grain size after solution treatment was changed with respect to 2. As the crystal grain size after the solution treatment increases, a obtained from the metal structure of the product increases and the stress relaxation rate decreases. The crystal grain size after solution treatment is less than 1 μm. 24a was less than 1 μm, the stress relaxation rate exceeded 30%, and the tensile strength was less than 550 MPa due to insufficient solution. No. in which the crystal grain size after solution treatment exceeded 15 μm. 29 of a exceeded 15 micrometers, and the crack generate | occur | produced by 180 degree | times adhesion bending.

Test example 2
The influence of alloy components on the microstructure and properties of products will be explained. Various examples of Cu—Ni—Si based alloys are shown in the above-mentioned Invention No. The product was processed under the same production conditions as in 1. In addition, when the solution treatment was performed under the condition of 750 ° C. × 60 seconds, although the crystal grain size was slightly changed depending on the components, all the crystal grain sizes were within the preferable range of the present invention.

(Influence of Ni concentration / Si concentration ratio)
Table 6 shows data obtained when Ni was fixed at 1.60% by mass and the Si concentration was changed. No. 1 and no. 5 is the same as the sample of Table 1. Here, no. 5 is a conventional alloy having a conductivity of less than 55% IACS, and its production conditions are different from those of other alloys.
When the Ni concentration / Si concentration ratio is out of the range of 4 to 6, the conductivity is less than 55% IACS. Further, when the Ni concentration / Si concentration ratio decreases, the tensile strength increases. This is because the precipitation amount of Ni ₂ Si increases due to the increase of the Si concentration.
The Sn plating heat release resistance evaluation result of the alloy of the present invention was Δ (point-like peeling). On the other hand, no. The evaluation results of 5 and 34 are x. This is because solute Si reduces the heat-resistant peelability. That is, no. In No. 5, since the precipitation amount of Ni ₂ Si is small, no. In 34, since Si was excessively added to Ni, solute Si increased.

(Influence of Ni)
Table 7 shows data obtained by changing the Ni concentration while maintaining the Ni concentration / Si concentration ratio within the range of the present invention. When the Ni concentration was less than 1.2% by mass, In 35, the tensile strength was less than 550 MPa. No. with Ni concentration exceeding 3.5 mass%. In No. 41, the tensile strength exceeded 700 MPa, and cracking occurred in 180 ° contact bending.

(Influence of Zn)
As an effect of Zn addition, no. Table 8 shows the data obtained when various concentrations of Zn were added to 1. By adding 0.05% by mass or more of Zn, the Sn plating heat-resistant peelability evaluation result was “good” (no peeling). On the other hand, the conductivity decreased as Zn increased, but a conductivity of 55% IACS or higher was obtained in the range where Zn was 0.5% by mass or less.

(Influence of impurities)
As impurities, no. Table 9 shows data obtained by increasing 43 impurities. The total amount of impurities is changed by adding Sn assuming that Sn-plated copper material is mixed, and adding Mg assuming that the deoxidizing element remains at the time of dissolution. When the impurity content exceeds 0.05% by mass, the conductivity is less than 55% IACS.

It is a figure explaining a stress relaxation test method. It is a figure which shows the temperature chart ((a) and (b) is an invention example, (c) is a prior art example) of an aging treatment.

Claims (6)

1.2 to 3.5% by mass of Ni, Si containing 1/6 to 1/4 of the concentration (% by mass) with respect to the Ni concentration (% by mass), the balance being Cu and 0.05% by mass in total A Cu—Ni—Si alloy composed of the following impurities and having the following characteristics:
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less 1.2 to 3.5% by mass of Ni, Si concentration of 1/6 to 1/4 (% by mass) with respect to Ni concentration (% by mass), 0.5% by mass or less of Zn, the balance being A Cu—Ni—Si based alloy comprising Cu and impurities in a total amount of 0.05% by mass or less and having the following characteristics:
(A) Conductivity: 55-62% IACS
(B) Tensile strength: 550 to 700 MPa
(C) Bendability: No cracks are generated by close contact bending at 180 degrees (D) Stress relaxation resistance: Stress relaxation rate when heated at 150 ° C. for 1000 hours is 30% or less (E) Heat release resistance: Sn plating heat release No plating peeling after test 1.2 to 3.5% by mass of Ni, Si concentration of 1/6 to 1/4 (% by mass) with respect to Ni concentration (% by mass), 0.5% by mass or less of Zn as an optional component The balance is composed of Cu and impurities of 0.05% by mass or less in total, and in the metal structure of the cross section parallel to the rolling surface, the average grain size in the direction perpendicular to the rolling direction of the crystal grains is a, the rolling direction When the average particle size in the parallel direction is b,
a = 1 to 15 μm, b / a = 1.05 to 1.67
And a Cu—Ni—Si based alloy in which the average width of the precipitation-free zone in the metal structure is 10 to 100 nm.   The copper-stretched product using the Cu-Ni-Si type alloy as described in any one of Claims 1-3.   The electronic component using the Cu-Ni-Si type alloy as described in any one of Claims 1-3. 2. A method for producing a Cu—Ni—Si based alloy comprising sequentially performing steps of solution treatment, cold rolling, aging treatment, and cold rolling, wherein each step is performed under the following conditions. The manufacturing method of the Cu-Ni-Si type alloy as described in any one of -3.
(Solution Treatment) The average crystal grain size is adjusted to a range of 1 to 15 μm.
(Aging treatment) The maximum temperature of the material during the heat treatment is set to 550 ° C. or lower, and the material is held in a temperature range of 450 to 550 ° C. for 5 to 15 hours. Moreover, the average temperature increase rate of the material in each temperature area of 200-250 degreeC, 250-300 degreeC, and 300-350 degreeC in a temperature rising process shall be 50 degrees C / h or less.
(Cold rolling) The total of the rolling degree in cold rolling before aging and the rolling degree in cold rolling after aging is made 5 to 40%.

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