WO2010016428A1 - Copper alloy material for electrical/electronic component - Google Patents

Abstract

A copper alloy material for electrical/electronic components, which is characterized by containing 0.7-2.5% by mass of Co, while containing Si in such an amount that the mass ratio between Co and Si (Co/Si) is not less than 3.5 but not more than 4.0, with the balance made up of Cu and unavoidable impurities.  The copper alloy material is also characterized by having a crystal grain size of 3-15 μm.

Description

Copper alloy material for electrical and electronic parts

The present invention relates to a copper alloy material for electric / electronic parts.

Up to now, parts for electrical and electronic devices (specifically connectors, terminals, relays, switches, etc.) include brass (C26000), phosphor bronze (C51910, C52120, C52100) and beryllium copper (C17200, C17530), Corson copper alloy (C70250) has been used. Here, “Cxxxx” is a type of copper alloy defined by CDA (Copper Development Association).
In recent years, the frequency of currents used in electric / electronic devices has increased, and metal materials used for parts for electric / electronic devices have been required to have higher conductivity. The so-called Corson-type copper alloy has high conductivity, but Cu—Co— added with Co and Si as a copper alloy that has both conductivity higher than the conventional Corson-type copper alloy and high tensile strength and bending resistance. Si-based alloys have been studied (for example, Patent Documents 1 and 2).

JP 2008-88512 A JP 2008-55977 A

While parts for electronic and electrical equipment are required to have high bending resistance as well as conductivity and tensile strength, Cu—Co—Si alloys described in Patent Documents 1 and 2 It cannot be said that the tensile strength, bending resistance, and conductivity (thermal conductivity) are all satisfied at a high level.
Patent Document 1 describes a bending test result under the condition of R / t = 1, where R is the inner bending radius of the material and t is the plate thickness. A bending test result in a 90-degree V bending test at 3 mm is described.
However, at this level, it seems that it will not be able to meet the bending resistance required in the future, and it is necessary to develop a copper alloy material for electrical and electronic parts that can pass even severe bending tests.
An object of the present invention is to provide a copper alloy material for electric / electronic parts that has high conductivity and high tensile strength and is excellent in bending resistance.

As a result of intensive studies, the present inventors have found that a copper alloy material containing a predetermined amount of Co and Si, having a mass ratio of Co and Si within a predetermined range, and having a crystal grain size within the predetermined range is highly conductive. And high tensile strength, it has been found to pass a strict bending test. The present invention has been made based on this finding.

According to the present invention, the following means are provided:
(1) Co is contained in an amount of 0.7 to 2.5% by mass, Si is contained in a mass ratio of Co to Si (Co / Si ratio) in the range of 3.5 to 4.0, and the balance is Cu and A copper alloy material for electric and electronic parts, characterized by comprising inevitable impurities and having a crystal grain size of 3 to 15 μm,
(2) 0.7 to 2.5 mass% of Co and 0.01 to 0.15 mass of at least one selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn, Mg and Zn %, And the mass ratio ((Co + X) / Si ratio) of Si to the total mass of at least one selected from the group consisting of Cr, Ni, Fe, Zr and Ti and Co with respect to Si is 3.5 or more. A copper alloy material for electrical and electronic parts, which is contained within a range of 4.0 or less and has a crystal grain size of 3 to 15 μm.

According to the present invention, it is possible to provide a copper alloy material for electric and electronic parts that has excellent conductivity and tensile strength and passes a strict bending test.
These and other features and advantages of the present invention will become more apparent from the following description.

A preferred embodiment of the alloy composition of the copper alloy material for electric / electronic parts of the present invention will be described in detail below. Here, the “copper alloy material” means a composition obtained by processing a composition as a copper alloy into a predetermined shape (for example, a plate, a strip, a foil, a bar, a wire, etc.). A preferable specific example of the copper alloy material will be described with a plate material and a strip material, but the shape of the copper alloy material is not limited to the plate material and the strip material.
First, the first copper alloy material for electric / electronic parts of the present invention will be described.
In the first copper alloy material for electric / electronic parts of the present invention, Co and Si are essential components. Co and Si in the copper alloy mainly form precipitates of Co ₂ Si intermetallic compounds. By setting the ratio of this precipitate within a specific range, it is possible to provide a copper alloy material for electric / electronic parts having high tensile strength and electrical conductivity.

In the copper alloy material for electric / electronic parts of the present invention, Co is 0.7 to 2.5% by mass, preferably 0.8 to 2.2% by mass, more preferably 0.9 to 1.7% by mass. is there. By setting it within this range, a copper alloy material for electric and electronic parts having high tensile strength and electrical conductivity can be obtained.
In the present invention, if the amount of Co is too small, the precipitate of Co ₂ Si intermetallic compound decreases, and a copper alloy material for electric / electronic parts with high tensile strength and electrical conductivity cannot be obtained. If the amount of Co is too large, the effect is saturated. As for Si, it is preferable to add an amount corresponding to Co so as to maintain the stoichiometric ratio of the Co ₂ Si intermetallic compound. When the amount of Si is not appropriate, it is the same as when the amount of Co is not appropriate. That is, if the amount of Si is too small, the precipitate of the Co ₂ Si intermetallic compound decreases, and a copper alloy material for electric / electronic parts with high tensile strength and electrical conductivity cannot be obtained. If the amount of Si is too large, the effect is saturated.

From the stoichiometric ratio of the Co ₂ Si intermetallic compound, the optimum mass ratio of Co to Si (Co / Si) is Co / Si≈4.2. However, in the copper alloy material of the present invention, Co to Si The mass ratio (Co / Si) is set in the range of 3.5 or more and 4.0 or less. Preferably, the value of Co / Si is in the range of 3.70 to 3.95 in terms of mass ratio. By setting the mass ratio of Co and Si (Co / Si ratio) within this range, a copper alloy material for electrical and electronic parts excellent in both tensile strength and bending can be obtained. If the mass ratio of Co to Si (Co / Si ratio) is too small, Si becomes excessive, so that part of Si that does not form an intermetallic compound with Co is dissolved, resulting in a low electrical conductivity. If the mass ratio of Co to Si (Co / Si ratio) is too large, Co becomes excessive, so that a part of Co that does not form an intermetallic compound with Si is dissolved and the conductivity is lowered.
When the amount of Co and the amount of Si exceed a predetermined amount, an alloy material cannot be obtained unless the solution temperature is increased. Therefore, at a temperature higher than the usual solution temperature (about 1000 ° C.). When heat treatment is performed, problems such as inability to maintain the product shape occur.
In the first copper alloy material for electric / electronic parts of the present invention, Si is determined so that the mass ratio of Co to Si (Co / Si) is in the range of 3.5 or more and 4.0 or less. Si is preferably 0.2 to 0.7% by mass.

Next, the second copper alloy material of the present invention will be described.
In the second copper alloy material of the present invention, Co is 0.7 to 2.5% by mass, and at least one selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn, Mg and Zn is 0. Si in the total mass of at least one (X) selected from the group consisting of Cr, Ni, Fe, Zr, and Ti and Co containing 0.01 to 0.15% by mass, the balance being Cu and inevitable impurities The mass ratio ((Co + X) / Si ratio) is within the range of 3.5 or more and 4.0 or less.
The addition amount of at least one selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn, Mg and Zn is preferably 0.05 to 0.15% by mass. When the addition amount is too small, the effect of the addition is small, and when the addition amount is too large, the strength is lowered and the conductivity is lowered by the solid solution of the added element.
About Cr, Ni, Fe, Zr and Ti, precipitates are formed with both or one of Co and Si, or alone, and the effect of reducing the crystal grain size is brought about. At least one (X) selected from the group consisting of Cr, Ni, Fe, Zr and Ti is substituted for a part of Co to form a (Co, X) ₂ Si compound and to improve the strength. .
On the other hand, Al, Sn, Mg, and Zn are characterized by solid solution in the copper matrix and strengthening. When Al, Sn, Mg and Zn are dissolved, the alloy material is strengthened and the stress relaxation resistance is improved. Further, by simultaneously adding Sn and Mg, the stress relaxation resistance is synergistically improved. When the addition ratio of Sn and Mg is Sn / Mg ≧ 1, the stress relaxation characteristics are further improved.

In the second copper alloy material of the present invention, the mass ratio ((Co + X) / Si ratio) of Si to the total mass of at least one selected from the group consisting of Cr, Ni, Fe, Zr and Ti and Co (Co) Is 3.5 or more and 4.0 or less. Preferably, the value of (Co + X) / Si ratio is in the range of 3.70 to 3.95 in terms of mass ratio. By setting the (Co + X) / Si ratio within this range, it is possible to obtain a copper alloy material for electrical and electronic parts that is excellent in both tensile strength and bending. If the (Co + X) / Si ratio is too small, Si becomes excessive, so that part of Si that does not form an intermetallic compound with Co and X is dissolved, and the conductivity is lowered. When the (Co + X) / Si ratio is too large, Co or X becomes excessive, so that a part of Co or X that does not form an intermetallic compound with Si is dissolved, and the conductivity is lowered.
In the second copper alloy material for electric / electronic parts of the present invention, the mass ratio of Si to the total mass of at least one (X) selected from the group consisting of Cr, Ni, Fe, Zr and Ti and Co (( The amount of Si is determined so that the (Co + X) / Si ratio) is in the range of 3.5 to 4.0, but Si is preferably 0.2 to 0.7 mass%.
In the first and second copper alloy materials of the present invention, as long as it is less than 5 ppm by mass of elements such as H, O, and S as unavoidable impurities, the copper alloy for electric / electronic parts is not impaired. A material can be obtained.

In the copper alloy material of the present invention, it is important that the crystal grain size is 3 to 15 μm. In the present invention, the crystal grain size refers to a value measured by JIS H 0501 (cutting method). By setting the crystal grain size within the range of 3 to 15 μm, it is possible to obtain a copper alloy material for electric / electronic parts having excellent bending resistance. When the crystal grain size is less than 3 μm, the remaining of the processed structure is confirmed, which adversely affects the bending resistance. On the other hand, when the grain size is larger than 15 μm, bending and cracking at the crystal grain boundaries become remarkable, resulting in a decrease in bending resistance. The crystal grain size is preferably 4 to 10 μm. In order to achieve a crystal grain size of 3 to 15 μm, the range of heat treatment conditions and rolling conditions in each step up to the final recrystallization heat treatment, where the blending amount of elements such as Co and Si is within a specific range. Is within a specific range, or the heat history management conditions (temperature increase rate, holding temperature and time) of the recrystallization heat treatment are within a specific range.

There is a preferable range in the relationship between the amount of Co added and the temperature at which the recrystallization treatment is performed. For example, when the amount of Co added is 0.7 to 1.0% by mass, the recrystallization treatment temperature is preferably in the range of 850 to 900 ° C., and the amount of Co added is 1.0 to 2.5% by mass. In this case, the recrystallization treatment temperature is preferably in the range of 900 to 1025 ° C. The upper limit temperature is more preferably 1000 ° C. By performing the recrystallization process within this temperature range, the recrystallization process can be performed reliably and deformation of the alloy material can be prevented.

Next, the preferable manufacturing method of the copper alloy material of this invention is the following aspects, for example. The outline of the main manufacturing method of the copper alloy material of the present invention is as follows: melting → casting → hot rolling → facing → cold rolling → solution recrystallization heat treatment → rapid cooling → aging heat treatment → final cold rolling → low temperature annealing. is there. Aging heat treatment and final cold rolling may be performed in reverse order. The final low-temperature annealing may be omitted.
<Melting casting>
Cu, Co, Si, etc., which are the raw materials for copper alloys, are melted and poured into a mold and cast while cooling at a cooling rate of 10 to 30 K / sec (K is “Kelvin” indicating absolute temperature; the same applies hereinafter). To obtain a copper alloy ingot. Here, a case where the width is 160 mm, the thickness is 30 mm, and the length is 180 mm is described.
<Hot rolling / facing / cold rolling>
Thereafter, the ingot is held at a temperature of 900 to 1000 ° C. for 30 to 60 minutes, and thereafter processed by hot rolling to a thickness of 8 to 15 mm (reduction rate of 50 to 73%), and then rapidly cooled with water (rapid cooling) In order to remove the oxide film on the surface, the rolled surface is chamfered about 1 mm on one side and then processed to a thickness of about 0.1 to 0.3 mm by cold rolling. . The rolling reduction is 95% or more (preferably 99.5% or less).
<Recrystallization heat treatment>
After that, for the purpose of solution and recrystallization, recrystallization heat treatment is performed for a certain time (here 30 seconds) in a salt bath (salt bath furnace) maintained at a temperature of 800 to 1025 ° C., and quenching is performed by water cooling. Do. During the recrystallization heat treatment, the temperature rise rate is adjusted by sandwiching the sample between stainless steel plates having different thicknesses. A preferable temperature increase rate at this time is 10 to 300 K / sec at a temperature of 300 ° C. or higher. A preferable cooling rate is 30 to 200 K / sec.
<Aging heat treatment>
Next, an aging heat treatment is performed at a temperature of 400 to 600 ° C. for 30 to 300 minutes for the purpose of aging precipitation. At that time, the rate of temperature rise from room temperature to the maximum temperature is in the range of 3 to 25 K / min. When the temperature is lowered, the temperature rises to 300 ° C, which is sufficiently lower than the temperature range considered to affect precipitation. Performs cooling in the furnace within the range of 1 to 2 K / min.
<Finish rolling>
The copper alloy material after the aging heat treatment is further cold-rolled at a processing rate of 20% to obtain a finished rolled material. Note that finish rolling may or may not be performed.
<Strain relief annealing>
After finishing the aging heat treatment (finished rolling is after finishing rolling), if necessary, strain relief annealing is performed.

The bending workability can be evaluated by right angle bending (R / t = 0) in a 90 ° W bending test under the condition that the yield stress (YS) value is 600 MPa or more and the conductivity is 60% IACS or more. it can. Here, R / t means the result of a W-bending test at a bending angle of 90 ° in accordance with the Japan Copper and Brass Association technical standard “Evaluation method for bending workability of copper and copper alloy sheet strip (JBMA T307)”. To do. The plate material cut in the vertical direction of rolling is subjected to a bending test under the condition of a predetermined bending radius (R), and the limit R at which the crack does not occur at the apex is obtained, and the plate thickness (t) at that time is specified. Thus, R / t can be obtained. Generally, the smaller the R / t, the better the bending workability.
The copper alloy material of the present invention is excellent in conductivity and tensile strength, and can pass a bending test under severe conditions.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Invention Examples No. 1 to 13 and Comparative Example Nos. 14 to 40)
An alloy containing the components shown in Table 1 and the balance consisting of Cu and inevitable impurities is melted in a high-frequency melting furnace and cast at a cooling rate of 10 to 30 K / sec. A 180 mm ingot was obtained. The cooling rate was set so that no cracks or the like occurred in the ingot.
The obtained ingot was held at a temperature of 1000 ° C. for 30 minutes and hot rolled to produce a hot rolled sheet having a thickness t = 12 mm. The both surfaces were each 1 mm chamfered to a plate thickness t = 10 mm, and then finished to a plate thickness t = 0.25 mm by cold rolling. Thereafter, recrystallization heat treatment was performed at a temperature of 870 to 1000 ° C.
The recrystallization heat treatment was performed by increasing the temperature as the amount of Co added was increased. Specifically, when the addition amount of Co is 0.9% by mass, 870 ° C., when the addition amount of Co is 1.2% by mass, 915 ° C., and when the addition amount of Co is 1.4% by mass, 940 ° C., 965 ° C. when Co addition amount is 1.65% by mass, 980 ° C. when Co addition amount is 1.9% by mass, 1000 ° C. when Co addition amount is 2.4% by mass It was. Note that when an additive other than Co and Si was included (Alloy Nos. 4 and 7 to 11), the temperature of the recrystallization heat treatment was the same as that when no additive other than Co and Si was included. Further, Comparative Example No. For 37 to 40, the recrystallization heat treatment temperatures were 940 ° C., 1050 ° C., 775 ° C., and 790 ° C., respectively, in order to change the crystal grain size.
And the following process was performed with respect to the material after recrystallization heat processing, and the test material corresponded to the final product was produced. The plate thickness of the test material was t = 0.2 mm.
Process: Recrystallization heat treatment-Aging heat treatment (temperature of 525 ° C for 2 hours)-Cold working (20%)

The following items were measured for this specimen. The composition table and crystal grain size of the copper alloy are shown in Table 1, and the evaluation results of the tensile strength and bending characteristics of the copper alloy material are shown in Table 2.
a. Crystal grain size:
After the cross section perpendicular to the rolling direction of the test piece is polished to a mirror surface by wet polishing and buffing, the polished surface is corroded for several seconds with a solution of chromic acid: water = 1: 1, and then magnification is 200 to 400 times with an optical microscope. Alternatively, a photograph was taken at a magnification of 500 to 2000 using a secondary electron image of a scanning electron microscope (SEM), and the crystal grain size was measured according to the cutting method of JIS H0501. And the arithmetic mean was calculated | required by setting the measurement parameter to 200, and this value was made into the value of the arithmetic mean of a crystal grain diameter. The results are shown in Table 1.

b. Yield stress (YS):
Two test pieces of JIS Z2201-5 cut out parallel to the rolling direction of the specimen were measured according to JIS Z2241, and the average value was obtained. The yield strength when the permanent elongation was 0.2% was calculated from the formula (1) by the offset method as the yield stress. The results are shown in Table 2.
σ _0.2 = F _0.2 / A ₀ formula (1)
here,
σ: Yield strength calculated by the offset method (N / mm ² ),
F: Using an extensometer, obtain a relationship diagram between the force and the amount of elongation, and draw a parallel line from the point on the elongation axis corresponding to the specified permanent elongation (ε%) to the straight line portion at the beginning of the test. The force shown by the points that intersect the figure

c. conductivity:
Using the four-terminal method, the conductivity was measured for two of each test piece in a thermostatic chamber controlled at 20 ° C. (± 1 ° C.), and the average value (% IACS) is shown in Table 2. At this time, the distance between terminals was set to 100 mm.

d. Bending workability A:
(1) W-bending A test piece having a thickness t = 0.20 (mm), a width w = 10 (mm), and a length l = 35 (mm) was cut out from the specimen in accordance with JIS Z2248 and polished. After lightly polishing the surface of the test piece with powder and removing the oxide film, a 90 ° W bend in which the inner radius of the bend is R = 0 (mm) is applied to a bend parallel to the rolling direction (Good-way). The bending was performed in two directions: bending (hereinafter referred to as GW bending) and bending perpendicular to the rolling direction (Bad-way bending: hereinafter referred to as BW bending). The value of R / t at this time is 0.
(2) 180 ° bending As with W bending, a pinch of twice the prescribed inner radius (here R = 0.1 mm) is applied according to JIS Z2248, and both ends of the test piece are pressed against each other to bend 180 °. And the same evaluation as the 90 ° W bending was performed. Since the values of R / t at this time are R = 0.1 (mm) and t = 0.2 (mm), R / t = (0.1 / 0.2) = 0.5 is there.
(3) Evaluation of presence / absence of cracks in the bent portion Visual observation with a 50 × optical microscope and observation of the bent portion with a scanning electron microscope (SEM) were conducted to investigate the presence / absence of cracks. For both 90 ° W bending and 180 ° bending, it was evaluated as ○ when there was no crack on the test surface of at least one of GW bending and BW bending, and × when there was a crack in both. In addition, when either 90 ° W bending or 180 ° bending was cracked in both GW bending and BW bending, the overall evaluation was x. The results are shown in Tables 1 and 2.

e. Bending workability B
Using a strip-shaped sample having a width of 10 mm, the test was carried out in accordance with the W bending test defined in JIS Z 2248. The bending direction was set to Good Way and Bad Way, and the bending radius was R / thickness t = 1.0. For the test piece after bending, from the surface and cross section of the bent part, the presence or absence of cracks was observed with an optical microscope. If no cracks occurred on Good Way and Bad Way, ○, both Good Way and Bad Way, or one of them The case where cracking occurred was evaluated as x. The results are shown in Table 2.

As shown in Tables 1 and 2, all of the examples of the present invention exhibited a high conductivity of 60% IACS or more, and the yield stress (YS) was 600 MPa or more. In addition, the R / t value was 0 at 90 ° bending, and the R / t value was 0.5 or less at 180 ° bending, showing excellent results even under severe bending test conditions. On the other hand, in the comparative example, the conductivity is less than 60% IACS, the yield stress (YS) is less than 600 MPa, the R / t value does not satisfy 0 at 90 ° bending, or at 180 ° bending. One or more of whether the value of R / t does not satisfy 0.5 or less. Note that, as in Alloy Nos. 15 to 18, the conductivity is as high as 60% IACS or more, and the yield stress (YS) may be 600 MPa or more, but R / t = 1.0 W Although it passed in the bending test, the value of R / t was 0, or the value of R / t was 0.5 after bending at 180 °, and it failed.

While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

This application claims priority based on Japanese Patent Application No. 2008-202469 filed in Japan on August 5, 2008, which is hereby incorporated herein by reference. Capture as part.

Claims (2)

Co is contained in an amount of 0.7 to 2.5% by mass, Si is contained in a mass ratio of Co to Si (Co / Si ratio) in the range of 3.5 to 4.0, and the balance is made up of Cu and inevitable impurities. A copper alloy material for electrical and electronic parts, characterized in that the crystal grain size is 3 to 15 μm. Including 0.7 to 2.5% by mass of Co and 0.01 to 0.15% by mass of at least one selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn, Mg and Zn, The mass ratio ((Co + X) / Si ratio) of Si to the total mass of Si and at least one selected from the group consisting of Cr, Ni, Fe, Zr and Ti with respect to Si is 3.5 or more and 4.0. A copper alloy material for electric and electronic parts, which falls within the following range and has a crystal grain size of 3 to 15 μm.