JP5619389B2 - Copper alloy material - Google Patents

Description

  The present invention relates to a copper alloy material suitably used for electrical and electronic parts.

Until now, brass (C2) has been used for connectors, terminals, relays, switches, etc. for electronic and electrical equipment.
6000), phosphor bronze (C51910, C52120, C52100), beryllium copper (C17200, C17530), corson copper (C70250), and the like have been used.

In recent years, the frequency of currents used in electronic and electrical equipment in which these are used has increased, and high conductivity has been required for materials. Therefore, originally, brass and phosphor bronze have low conductivity, and Corson copper shows medium conductivity (conductivity of about 40% IACS) as a connector material, but higher conductivity is required. It is also well known that beryllium copper is expensive. On the other hand, pure copper (C11000), tin-containing copper (C14410), and the like, which have high conductivity, have a drawback of low strength. Therefore, there is a demand for a copper alloy having tensile strength and bending workability equivalent to those of electrical conductivity exceeding conventional Corson copper.
Here, “Cxxxx” means CDA (Copper Development As
sociation), and% IACS is a unit indicating conductivity of a material, and “IACS” is “International Annealed”.
Abbreviation for “Copper Standard”.

In particular, in recent electronic device parts, there are many connectors and terminals that have been subjected to complicated and severe bending as the device is downsized. This is because the size of the connector is downsized as the size is reduced, but in order to maintain the reliability of the contact, it is desired to have a contact length as long as possible. Connectors and terminals having such a design concept are often referred to as bellows (bellows) bending connectors or bellows bending terminals. In other words, there is a high demand for installing and installing terminals and connectors bent in a complicated manner in small parts. On the other hand, the material of the connector and terminal used with size reduction becomes thinner. This is also progressing from the viewpoint of weight reduction and resource saving. Thin materials are required to have higher strength than thick materials in order to maintain the same contact pressure.

As a method for increasing the strength of the copper alloy material, there are various strengthening methods such as solid solution strengthening, work strengthening, and precipitation strengthening. In copper alloy materials, conductivity and strength are generally in a reciprocal relationship, but it is known that precipitation strengthening is promising as a method of increasing strength without reducing the conductivity of copper alloy materials. This precipitation strengthening is a high temperature heat treatment of an alloy added with an element that causes precipitation, so that these elements are dissolved in the copper matrix phase, and then heat treated at a temperature lower than the temperature at which the solid solution is formed. This is a technique for precipitating the deposited elements. For example, beryllium copper, corson copper, etc. employ the strengthening method.

By the way, in the copper alloy material, in addition to the relationship between conductivity and strength, the relationship between bending workability and strength is also in an opposite relationship. In order to increase the strength, it is considered effective to increase the final cold rolling rate, but when the cold rolling rate is increased, the bending workability tends to be remarkably deteriorated.
Until now, beryllium copper, corson copper, titanium copper and the like have been considered to have a good balance between bending workability and strength as precipitation-type copper alloys. However, for beryllium copper, beryllium, which is an additive element, is regarded as an environmentally hazardous substance, and an alternative material is required. Corson copper and titanium copper generally do not have a conductivity of 50% IACS or higher. Applications requiring high conductivity of 50% IACS or higher include, for example, battery terminals and relay contacts to which a high current is applied. In general, a material having high conductivity has excellent heat conduction characteristics, so that a material such as a CPU (integrated arithmetic element) socket or heat sink that requires heat dissipation also has high conductivity. Particularly in recent hybrid vehicles and CPUs that perform high-speed processing, materials having high conductivity and high strength are required.

From such a background, cobalt (C) is added in consideration of strength, bending workability, and conductivity (thermal conductivity).
A copper alloy using an intermetallic compound composed of o) and silicon (Si) is attracting attention. C
A copper alloy that essentially contains o and Si is known as follows.

In Patent Document 1, in order to improve hot workability, in addition to Co and Si, Zn (zinc), Mg
A copper alloy that essentially contains (magnesium) and S (sulfur) is disclosed.
Patent Document 2 discloses an alloy containing Mg, Zn, and Sn (tin) in addition to Co and Si.
Patent Document 3 discloses an alloy containing Sn and Zn in addition to Co and Si.
Patent Document 4 describes that a Cu—Co—Si alloy, which is a precipitation-strengthened alloy for lead frames, is disclosed.
Patent Document 5 discloses a Cu—Co—Si based alloy in which the size of inclusions to be precipitated is 2 μm or less.
Patent Document 6 discloses a Cu—Co—Si based alloy in which a Co ₂ Si compound is precipitated.

JP-A-61-87838 JP-A 63-307232 Japanese Patent Laid-Open No. 02-129326 Japanese Patent Laid-Open No. 02-277735 JP 2008-88512 A JP 2008-55977 A

However, none of the techniques described in each patent document satisfies all of strength, bending workability, and conductivity (thermal conductivity) at a high level. Further, it is not intended to suppress the variation in characteristics.
Patent Document 1 aims to improve hot workability, and there is no description about strength and conductivity.
In Patent Document 2, there is no description that recrystallization treatment is performed, and it is considered that bending workability is poor.
Patent Document 3 shows a comparatively low value of conductivity of 30% IACS or less in the embodiment.
Patent Document 4 describes a precipitation strengthened alloy, but does not describe a specific compound or its size. Moreover, there is no description that the recrystallization process is performed, and the bending workability is considered to be poor.
In Patent Document 5 and Patent Document 6, when the inner bending radius of the material is R and the thickness is t, R
Although there is an example in which bending workability is evaluated under the condition of / t = 1, Patent Document 5 and Patent Document 6 do not have a specific description of the metal structure, and are not intended to suppress variation in characteristics. That is, it is considered that the bending workability required in the future cannot be sufficiently handled.

Therefore, the present invention provides a copper alloy material in which the value of the crystal grain size of the Cu-Co-Si-based copper alloy is controlled within a predetermined range in order to satisfy all of high conductivity, high strength, and good bending workability. The purpose is to provide.

The present invention is characterized by the following matters.
(1) Containing 0.7 to 2.5% by mass of Co (cobalt) as an additive element;
Incorporated within a range of a mass ratio of silicon) to Si in the Co (Co / Si) is 3 to 5, the balance being a copper alloy material is copper and inevitable impurities, the arithmetic mean of the crystal grain size of 3 ~ 2
A copper alloy material characterized in that 0 μm, a standard deviation is 8 μm or less, and the standard deviation is smaller than the arithmetic mean.
(2) It contains 0.7 to 2.5% by mass of Co (cobalt) as an additive element, and further Si (
Silicon) in a range where the mass ratio of Co to Si (Co / Si) is 3 or more and 5 or less, and further 0.01 to 1.0 mass% of Cr (chromium) or 0 of Ni (nickel). .0
1 to 1.0 wt%, or Ti a (titanium) containing 0.01 to 0.1 wt%, the balance being a copper alloy material is copper and inevitable impurities, the arithmetic mean of the crystal grain size of 3 A copper alloy material having a standard deviation of ˜20 μm and a standard deviation of 8 μm or less, and the standard deviation being smaller than the arithmetic mean.

According to the present invention, it is possible to provide a copper alloy material that is excellent in strength, conductivity, and bending workability, has small variations in characteristics, and is suitable for electrical and electronic equipment applications.

A preferred embodiment of the copper alloy material of the present invention will be described in detail. Here, “copper alloy material” means that a copper alloy material (which means a copper alloy material having no concept of shape here) has a predetermined shape (eg, plate, strip, foil, bar, wire, etc.) It means what has been processed. Further, the “base copper alloy” means a copper alloy not including the concept of shape.
In addition, although a board | plate material and a strip are demonstrated as a preferable specific example of copper alloy material, the shape of a copper alloy material is not restricted to a board | plate material or a strip.

The copper alloy material of the present invention contains 0.7 to 2.5 mass% of Co (cobalt) as an essential additive element, Si (silicon), and the mass ratio of Co to Si (Co / Si) is 3 or more. It is a copper alloy material contained in a range of 5 or less. This material can have a conductivity of 60% IACS or more and a tensile strength of 570 MPa or more, and can satisfy the demand for high conductivity and high strength. The electrical conductivity of the copper alloy material of the present invention is preferably 50% IACS or more. More preferably, it is 55% IACS or more, more preferably 60% IACS or more, and the higher the better, but the upper limit is usually about 75% IACS from the viewpoint of having an appropriate tensile strength. The tensile strength of the copper alloy material of the present invention is preferably 550 MPa or more. More preferably 60
The upper limit is preferably 0 MPa or higher, more preferably 750 MPa or higher, and the higher the better, but the upper limit is usually about 900 MPa from the viewpoint of combining moderate conductivity.
In addition, it is useful for further improving the bending workability that the arithmetic average of the crystal grain size of the base copper alloy is 3 to 20 μm and the standard deviation is 8 μm or less. The standard deviation is preferably as small as possible, and the standard deviation of the crystal grain size is more preferably smaller than the arithmetic average of the crystal grain size. The arithmetic mean and standard deviation of the crystal grain size of the base copper alloy are in the above range,
Bending stress (strain applied) can be sufficiently dispersed. In order to further improve the bending workability, the value obtained by subtracting the standard deviation from the arithmetic mean of the crystal grain size of the base copper alloy is 0 μm.
The value obtained by dividing the standard deviation by the arithmetic mean is more preferably 0.6 or less, and further preferably 0.4 or less. It is practical that the lower limit of the value obtained by dividing the standard deviation by the arithmetic average is 0.2 or more. When the value is smaller than this value, the characteristics are improved, but actual manufacturing tends to be difficult.
Here, the measurement parameter when calculating the arithmetic mean and standard deviation of the crystal grain size of the copper alloy of the base material is 1
It is preferable to set it to 00 or more, and it is more preferable that the measurement parameters of the arithmetic mean and the standard deviation are the same value.

Regarding bending workability, when the tensile strength is 570 MPa or more and 650 MPa or less, R /
When the value of t is 0.5 or less and the tensile strength is more than 650 MPa and 700 MPa or less, R /
When the value of t is 1.0 or less and the tensile strength exceeds 700 MPa, the value of R / t is preferably 1.5 or less. 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)”. Then, a 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 thickness (t) at that time This is the value normalized by. In general, the smaller the R / t, the better the bending workability. In the copper alloy material for electric and electronic parts of the present invention, the tensile strength and bending workability (R / t
) Having the above-mentioned relationship is preferable. Further, the lower limit of the bending workability (R / t) is zero.

Hereinafter, additive elements other than Co and Si will be described.
Fe, Cr, and Ni are elements that contribute to strength improvement by forming a compound with Si by substitution with Co. Fe, Ni, and Cr are substituted with a part of Co to form a (Co, χ) ₂ Si compound (χ
Forms Fe, Ni, Cr) and has the function of improving the strength. At least one of these elements (each element, a combination of any two kinds of elements may be any of the three kinds) may be in the range of 0.01 to 1.0 mass% in total. If it is 0.01% by mass or more, the effect is remarkably exhibited. If the total is 1.0% by mass or less, crystallization occurs during casting, or an intermetallic compound that does not contribute to strength is formed. There is no influence such as a decrease in conductivity. In addition,
Even if these elements are added in combination or added alone, almost the same effect is observed, but when Ni is added, a remarkable strength improvement effect is exhibited. The addition amount of Fe, Ni, and Cr is preferably 0.05 to 0.9% by mass in total of at least one or more of these elements. Zr and Ti also have almost the same effect as Fe, Ni and Cr, but Zr and Ti are easy to oxidize, and if added in a large amount, cracking may occur in the material being manufactured.
About the addition amount of Zr and Ti, it is preferable to set it as the range of 0.01-0.1 mass% in total of at least 1 sort (s) or 2 or more types of these elements.

Sn, Zn, Mg, and Mn are characterized by solid solution in the copper matrix and strengthening. If the added amount is 0.01% by mass or more in total of at least one or more of these elements, the effect is obtained, and if it is 1.0% by mass or less, the conductivity is not hindered. A preferred addition amount is 0.05 to
0.2% by mass. Examples of the inevitable impurities in the copper alloy material of the present invention include H, C, O, and S, as in the copper alloy material of the first or second embodiment.

Zn has the effect of improving solder adhesion, and Mn has the effect of improving hot workability. Addition of Sn and Mg is effective in improving the stress relaxation resistance. Although the effect can be seen even when individual Sn and Mg are added, it is an element that exhibits the effect synergistically when added simultaneously. The amount of addition is at least one of these elements or a total of two or more of these elements.
If it is 1% by mass or more, the effect is obtained, and if it is 1.0% by mass or less, conductivity is not hindered, and conductivity of 50% IACS or more is ensured. On the other hand, regarding the addition ratio of Sn and Mg, S
In the case of n / Mg ≧ 1, the stress relaxation resistance is further improved.

Next, an example of the process for producing the copper alloy material of the present invention will be described.
<Melting casting>
Copper, cobalt, silicon, etc., which are raw materials for the copper alloy, are melted and poured into a mold, and 10-30
Casting is performed while cooling at a cooling rate of K / second (K is “Kelvin” indicating absolute temperature; the same applies hereinafter) to obtain a copper alloy ingot. Here, the width is 160 mm, the thickness is 30 mm, and the length is 180 mm.
<Hot rolling / facing / cold rolling>
Thereafter, this ingot is held at a temperature of 900 to 1000 ° C. for 30 to 60 minutes, and thereafter processed by hot rolling until the thickness becomes 12 mm, and then rapidly quenched with water cooling (rapid cooling), on the surface In order to remove the oxide film, the rolled surface is chamfered about 1 mm on one side and about 10 m
Then, it is processed to a thickness of about 0.1 to 0.3 mm by cold rolling.
<Recrystallization heat treatment>
Then, 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 with 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 1 at a temperature of 300 ° C. or higher.
0 to 300 K / sec. Moreover, a preferable cooling rate is 30 to 200 K / sec.

<Aging heat treatment>
Next, an aging heat treatment was performed at a temperature of 525 ° C. for 120 minutes for the purpose of aging precipitation. In this case, 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 is sufficiently lower than 300 ° C., which is sufficiently lower than the temperature range considered to affect precipitation. Performs cooling in the furnace within a range of 1 to 2 K / min.
<Finish rolling (if necessary)>
The copper alloy material after the aging heat treatment is subjected to final cold rolling at a processing rate of 0% to 40% (the upper limit is preferably 20%) to obtain a finished rolled material. Note that finish rolling may or may not be performed. A processing rate of 0% means that finish rolling is not performed.
<Strain relief annealing>
After finishing the aging heat treatment (finished rolling is after finishing rolling), if necessary, strain relief annealing is performed.
<Repeating process>
The recrystallization heat treatment and the aging heat treatment may be repeated twice or more under the above conditions.

Basically, the crystal grain size and its distribution (standard deviation) by recrystallization heat treatment and aging heat treatment
Is determined. In order to change the grain size and distribution of crystal grains, it is effective to control the rate of temperature rise, the holding temperature at the time of heat treatment, and the cooling rate in recrystallization heat treatment and aging heat treatment.

In addition, the temperature increase rate, the holding temperature during heat treatment, and the cooling rate are also related to the amounts of addition of Co and Si, which are essential additive elements in the copper alloy material of the present invention, so the amounts of Co and Si are adjusted. Also, the grain size and distribution thereof can be changed. In addition, Cu, Co
By adding an element other than Si, precipitates other than crystal grains can be dispersed in the copper alloy, and the grain size and distribution thereof can be changed by the action.

The copper alloy material of the present invention is required to have an arithmetic average crystal grain size of 3 μm to 20 μm and a standard deviation of 8 μm or less in order to satisfy all of high conductivity, high strength, and good bending workability. . The standard deviation is preferably as small as possible, and the standard deviation of the crystal grain size is more preferably smaller than the arithmetic average of the crystal grain size. When the arithmetic mean and standard deviation of the crystal grain size of the copper alloy as the base material are within the above ranges, the bending stress (strain applied) can be sufficiently dispersed.
Therefore, the above-described additive elements and production conditions (particularly conditions for recrystallization heat treatment and aging heat treatment) are appropriately adjusted so as to satisfy the arithmetic average and standard deviation conditions of the crystal grain size. In particular, when the arithmetic average of the crystal grain size is less than 3 μm, an unrecrystallized region remains and directly leads to deterioration of the bending characteristics. Therefore, the standard deviation of the crystal grain size is smaller than the arithmetic average of the crystal grain size. It is preferable that the thickness is 3 μm or more.
In order to further improve the bending workability, the value obtained by subtracting the standard deviation from the arithmetic mean of the crystal grain size of the base copper alloy is preferably larger than 0 μm, and the standard deviation is divided by the arithmetic mean. The value is more preferably 0.6 or less, and further preferably 0.4 or less. It is practically practical that the lower limit of the value obtained by dividing the standard deviation by the arithmetic average is 0.2 or more.

Here, the temperature increase rate in the recrystallization heat treatment will be described. If the rate of temperature rise is too slow, the heat treatment will be over, resulting in coarsening of precipitates and crystallized materials, and there is a risk that strength will be reduced. Moreover, there is a possibility that crystal grain coarsening occurs due to overheating. On the other hand, when the rate of temperature rise is too fast, the number of precipitates generated to prevent coarsening of the crystal grains decreases, and there is a risk that the crystal grains become coarse. For this reason, a preferable temperature increase rate becomes as above.

As for the recrystallization heat treatment temperature, adjust the addition amount of Co. When the addition amount of Co is less than 1% by mass, the holding temperature at the recrystallization heat treatment is set to 850 ° C. or more and less than 900 ° C., and when the addition amount of Co is 1% by mass or more, the holding temperature at the recrystallization heat treatment is set to 900 ℃ or more on the 1 000 ℃ shall be the less than. If the holding temperature during the recrystallization heat treatment is lower than this range, there is a risk that the strength will be insufficient.If the holding temperature during the recrystallization heat treatment is higher than this range, the bending property may be deteriorated due to grain coarsening. This is because the copper alloy material may be deformed.

EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to them.

Example 1
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, which is cast at a cooling rate of 10 to 30 K / sec, and is 160 mm wide and 30 mm thick.
An ingot with a length of 180 mm was obtained. In addition, the cooling temperature was performed on the conditions which a crack etc. do not generate | occur | produce in an ingot.
The obtained ingot is held at a temperature of 1000 ° C. for 30 minutes, hot rolled to produce a hot-rolled sheet having a thickness t = 12 mm, both sides thereof are each 1 mm chamfered to a thickness t = 10 mm, The sheet thickness t was finished to 0.3 mm by cold rolling, and then recrystallization heat treatment was performed at a temperature in the range of 800 to 1025 ° C. The recrystallization heat treatment temperature was changed as shown in Table 1 according to the amount of Co added. And the following two processes were given with respect to the material after recrystallization heat processing, and the test material equivalent to a final product was created. In addition, although the value at the time of implementing the process A was described in each example of Table 1-Table 2, even when the process B was implemented about each example, a result became a result similar to the case where the process A was implemented. It was.
Step A: Recrystallization heat treatment-Aging heat treatment (temperature of 525 ° C for 2 hours)-Cold working (0 to 40%)
)
* After this, if necessary, strain relief annealing was performed at a temperature of 300 to 400 ° C. for 1 to 2 hours.
Step B: Recrystallization heat treatment-cold working (0 to 40%)-aging heat treatment (temperature of 525 ° C for 2 hours)

The following property investigation was conducted on this specimen. Table 1 shows the evaluation results of the characteristics of the copper alloy material as an alloy, and Table 2 shows the evaluation results of the strength and bending characteristics of the copper alloy material. In Table 2,
For some of the examples in Table 1, the alloy composition (No. 101, 102) and / or manufacturing method (No.
. The evaluation results when 203 to 208) are outside the scope of the present invention are shown together with the evaluation including some bending workability in the examples shown in Table 1. The plate thickness of the copper alloy material is t = 0.
It was 25 mm (processing rate of cold working = 20%).
a. Tensile strength:
JIS Z2201-13B test piece cut out from the direction parallel to the rolling of the test piece
Three samples were measured according to Z2241, and the average value was shown.
b. Conductivity measurement:
Using a four-terminal method, the electrical conductivity of two test pieces was measured in a thermostat controlled at 20 ° C. (± 1 ° C.), and the average value (% IACS) is shown in Tables 1-2. It was. At this time, the distance between terminals was set to 100 mm.
c. Bending workability:
GW (Good-way) bending, in which a specimen cut into a width of 10 mm and a length of 35 mm parallel to the rolling direction is bent so that the axis of bending is perpendicular to the rolling direction, and a width of 1 perpendicular to the rolling direction
The specimens cut out to 0 mm and 35 mm in length were evaluated for BW (Bad-way) bending in which the bending axis was parallel to the rolling direction.
Respectively, it is 90 in 21 levels (0.025mm unit) of bending radius R = 0-0.5 (mm).
Bending was performed, and the presence or absence of cracks in the bent part was observed 50 times with an optical microscope and 200 times with a scanning electron microscope (SEM). R of R / t in the table is the minimum bending radius at which no bending crack was confirmed, and t indicates the plate thickness. The smaller this value, the better the bending workability.
d. Crystal grain size (arithmetic mean):
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. In the table, “average grain size” is indicated.
e. Crystal grain size deviation:
The grain size was measured one by one by the same method as the above grain size measurement, and the standard deviation of the grain size was determined with the measurement parameter being 200.

As shown in Tables 1 and 2, the examples of the present invention satisfy all of the strength, conductivity, and bending workability in a well-balanced manner. Specifically, the electrical conductivity is 60% IACS or more, the tensile strength is 570 MPa or more and 650 MPa or less, the R / t value is 0.5 or less, and the tensile strength is 650 MP.
The value of R / t is 1.5 or less when the value of R / t is 1.0 or less and the tensile strength exceeds 700 MPa at a pressure of 700 MPa or less. In contrast, the comparative example did not satisfy the above values.

Claims (2)

Co (cobalt) is contained as an additive element in an amount of 0.7 to 2.5% by mass, and Si (silicon) is further contained in a range where the mass ratio of Co to Si (Co / Si) is 3 or more and 5 or less, and the balance Is a copper alloy material which is copper and inevitable impurities,
Crystal grain arithmetic mean of the diameter of 3 to 20 [mu] m, and the standard deviation is 8μm or less, the copper alloy material characterized in that the standard deviation is smaller than the arithmetic mean. Co (cobalt) is contained as an additive element in an amount of 0.7 to 2.5 mass%, and Si (silicon) is further contained in a range where the mass ratio of Co to Si (Co / Si) is 3 or more and 5 or less,
Furthermore, Cr (chromium) is 0.01 to 1.0 mass%, or Ni (nickel) is 0.01
-1.0 mass%, or a copper alloy material containing 0.01-0.1 mass% Ti (titanium), the balance being copper and inevitable impurities,
Crystal grain arithmetic mean of the diameter of 3 to 20 [mu] m, and the standard deviation is 8μm or less, the copper alloy material characterized in that the standard deviation is smaller than the arithmetic mean.