JP5437520B1 - Cu-Co-Si-based copper alloy strip and method for producing the same - Google Patents

Abstract

Provided are a Cu—Co—Si based copper alloy strip excellent in workability while maintaining conductivity and strength, and a method for producing the same.
SOLUTION: Co: 0.5 to 3.0% by mass, Si: 0.1 to 1.0% by mass, Co / Si mass ratio: 3.0 to 5.0, the balance being copper and inevitable impurities, Rankford value The absolute value of the in-plane anisotropy Δr of r is 0.2 or less (provided that Δr = (r0 + r90-2 × r45) / 2), and is 0 °, 45 °, and 90 ° with respect to the rolling parallel direction. Cu-Co-Si-based copper alloy strips having r values of r0, r45, and r90, respectively.
[Selection figure] None

Description

  TECHNICAL FIELD The present invention relates to a Cu—Co—Si based copper alloy plate and a current carrying or heat radiating electronic component that can be suitably used for the production of electronic parts such as electronic materials. The present invention relates to a Cu—Co—Si based copper alloy plate used as a material for electronic components such as connectors, relays, switches, sockets, bus bars, lead frames, and heat sinks, and electronic components using the copper alloy plates. Among these, Cu— suitable for use in high current electronic parts such as connectors and terminals for high current used in electric vehicles, hybrid cars, etc., or for use in electronic parts for heat dissipation such as liquid crystal frames used in smartphones and tablet PCs. The present invention relates to a Co—Si based copper alloy plate and an electronic component using the copper alloy plate.

  Copper alloy strips having excellent strength and conductivity are widely used as materials for transmitting electricity or heat, such as terminals, connectors, switches, sockets, relays, bus bars, lead frames, and heat sinks of electronic devices. Here, electrical conductivity and thermal conductivity are in a proportional relationship. By the way, in recent years, high currents have been developed in connectors of electronic devices, and it is considered necessary to have good bendability, conductivity of 55% IACS or more, and proof stress of 600 MPa or more. Moreover, in order to ensure solderability, the connector material is required to have good plating properties and solder wettability.

  On the other hand, for example, a heat radiating component called a liquid crystal frame is used for a liquid crystal of a smartphone or a tablet PC. Even in such a copper alloy plate for heat dissipation, high thermal conductivity is progressing, and it is considered necessary to have good bendability and high strength. For this reason, it is considered that a copper alloy plate for heat dissipation needs to have a conductivity of 55% IACS or more and a proof stress of 550 MPa or more.

However, it is difficult to achieve a conductivity of 60% IACS or higher with Ni-Si copper alloys, and Co-Si copper alloys have been developed. Since the copper alloy containing Co-Si has a small amount of Co2Si, the conductivity can be made higher than that of the Ni-Si based copper alloy.
As this Co—Si based copper alloy, a copper alloy excellent in plating adhesion is disclosed by setting the size of inclusions to 2 μm or less and reducing coarse precipitates (Patent Document 1).

JP 2008-056977 A

By the way, although a Co—Si based copper alloy is excellent in electrical conductivity and strength, it is not suitable for processing such as drawing or overhanging, and cracks and shape defects are likely to occur during processing. For this reason, it is difficult to design a process when applying a Co-Si based copper alloy to a connector or a heat sink of an electronic device, or if the processing is difficult, use another alloy that lacks conductivity (thermal conductivity). There was a problem that necessary functions could not be obtained.
That is, the present invention has been made to solve the above-described problems, and an object thereof is to provide a Cu—Co—Si based copper alloy strip excellent in workability while maintaining conductivity and strength, and a method for producing the same. And Furthermore, another object of the present invention is to provide a method for producing the copper alloy plate and an electronic component suitable for high current use or heat dissipation use.

  The Cu—Co—Si based copper alloy strip of the present invention contains Co: 0.5 to 3.0 mass%, Si: 0.1 to 1.0 mass%, Co / Si mass ratio: 3.0 to 5.0, with the balance being copper. And the absolute value of the in-plane anisotropy Δr of the Rankford value r is 0.2 or less (where Δr = (r0 + r90-2 × r45) / 2), with respect to the rolling parallel direction. R values of 0 degrees, 45 degrees, and 90 degrees are r0, r45, and r90, respectively).

In the Cu—Co—Si based copper alloy strip of the present invention, the work hardening coefficient (n value) is preferably 0.04 or more.
The crystal grain size observed on the rolling surface is preferably 20 μm or less.
Containing 0.001 to 2.5 mass% in total of at least one selected from the group consisting of Ni, Cr, Mg, Mn, Ag, P, Sn, Zn, As, Sb, Be, B, Ti, Zr, Al, and Fe Is preferred.

  The method for producing a Cu—Co—Si based copper alloy strip according to the present invention is a method for producing the Cu—Co—Si based copper alloy strip, which includes hot rolling, first annealing, and a workability of 10% or more. 1 cold rolling, solution treatment, and aging treatment are performed in this order, and the first annealing and the first cold rolling are repeated twice or more. The first annealing is performed before and after annealing. The tensile strength is reduced by 10 to 40%.

  In still another aspect, the present invention is an electronic component for large current using the Cu—Co—Si based copper alloy strip.

  In another aspect of the present invention, there is provided a heat dissipation electronic component using the Cu—Co—Si based copper alloy strip.

  According to the present invention, it is possible to provide a Cu—Co—Si based copper alloy strip excellent in workability while maintaining conductivity and strength, a manufacturing method thereof, and an electronic component suitable for high current use or heat dissipation use. Is possible. This copper alloy plate can be suitably used as a material for electronic parts such as terminals, connectors, switches, sockets, relays, bus bars, lead frames, etc., and particularly dissipates the material or large amount of heat of electronic parts that carry a large current. It is useful as a material for electronic parts.

  Hereinafter, the Cu—Co—Si based copper alloy strip according to the embodiment of the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

First, the reasons for limiting the composition of the copper alloy strip will be described.
<Co and Si>
Co and Si are subjected to an aging treatment to form precipitated particles of an intermetallic compound mainly composed of Co ₂ Si in which Co and Si are fine, and remarkably increase the strength of the alloy. Further, the conductivity is improved with the precipitation of Co ₂ Si in the aging treatment. However, when the Co concentration is less than 0.5%, or when the Si concentration is less than 0.1 (1/5 of Co%), the desired strength cannot be obtained even if the other component is added. Also, if the Co concentration exceeds 3.0%, or if the Si concentration exceeds 1.0 (1/3 of Co%)%, sufficient strength can be obtained, but the conductivity is lowered and further contributes to improvement of strength. Coarse Co—Si-based particles (crystallized product and precipitate) that are not formed are generated in the matrix phase, leading to a decrease in bending workability, etching property, and plating property. Therefore, the Co content is set to 0.5 to 3.0 mass%. Preferably, the Co content is 1.0 to 2.0 mass%. Similarly, the Si content is 0.1 to 1.0 mass%. Preferably, the Si content is 0.2 to 0.7 mass%.

When the mass ratio of Co / Si is 3.0 to 5.0, both strength and conductivity after precipitation hardening can be improved. If the Co / Si mass ratio is less than 3.0, the concentration of Si that does not precipitate as Co ₂ Si increases and the conductivity decreases. When the mass ratio of Co / Si exceeds 5, the concentration of Co that does not precipitate as Co ₂ Si increases and the conductivity decreases.

Furthermore, Ni, Cr, Mg, Mn, Ag, P, Sn, Zn, As, Sb, Be,
It is preferable to contain a total of 0.001 to 2.5 mass% of one or more selected from the group consisting of B, Ti, Zr, Al, and Fe. These elements contribute to an increase in strength by solid solution strengthening or precipitation strengthening. If the total amount of these elements is less than 0.001% by mass, the above effect may not be obtained. On the other hand, if the total amount of these elements exceeds 2.5% by mass, the electrical conductivity may be lowered or cracked by hot rolling.

  The thickness of the Cu—Co—Si based copper alloy strip of the present invention is not particularly limited, but may be 0.03 to 0.6 mm, for example.

<In-plane anisotropy Δr of Rankford value r>
Next, the rules that characterize the copper alloy strip will be described. The inventors of the present invention can obtain an alloy in which the in-plane anisotropy Δr of the Rankford value r is 0.2 or less by producing a Cu—Co—Si based copper alloy strip under predetermined conditions. all right. This is because annealing and rolling are repeated under the following conditions, the shape of crystal grains in the rolling direction and the plate thickness direction and how to introduce strain become uniform, and the reduction in the plate thickness direction during deformation is suppressed. This is probably because of this.
Here, r indicates a plastic strain value indicating whether the plate is easily deformed in the thickness direction or the plate width direction, and the higher r is, the better the deep drawability is.
Theoretically, r is obtained by the following equation.
r = ln (Wo / W) / ln (t0 / t)
Here, Wo and W are plate widths before and after deformation, and to and t are plate thicknesses before and after deformation. However, r varies depending on where the test piece is taken out, and the deep drawability may deteriorate depending on the plate surface direction. Therefore, in the present invention, attention is paid to the r value in-plane anisotropy Δr, and the smaller this value, the better the deep drawability in any direction, and the workability is greatly improved. In addition, when deep drawing is performed, if the ease of shrinkage of the material varies depending on the direction, the wall (ear) height of the flange portion becomes non-uniform, but the smaller the Δr, the smaller the ear height and the workability. Will improve.
Δr = (r0 + r90-2 × r45) / 2
It is represented by Here, r values obtained by subjecting the sample to tensile tests in directions of 0 °, 45 °, and 90 ° with respect to the rolling parallel direction are defined as r0, r45, and r90, respectively, and Δr is calculated from these values.

As the conditions for producing the Cu—Co—Si copper alloy strip, the ingot is subjected to hot rolling, first annealing, first cold rolling with a workability of 10% or more, solution treatment, and aging treatment in this order. And the first annealing and the first cold rolling are repeated twice or more, and the first annealing is performed under the condition that the tensile strength is reduced by 10 to 40% before and after annealing. | Δr | ≦ 0 .2 alloy strip is obtained.
Note that final cold rolling may be performed between the solution treatment and the aging treatment.
By performing the first annealing and the first cold rolling under the above-mentioned conditions, as described above, the shape of the crystal grains in the rolling direction, the plate thickness direction, and the plate width direction and the way of introducing strain become uniform. Since the decrease in the thickness direction during deformation is suppressed, Δr is considered to be 0.2 or less.
If the number of repetitions of the first annealing and the first cold rolling is less than 2, the above-described effect cannot be obtained, and | Δr |> 0.2.
In the first annealing, when the tensile strength decreases by less than 20% before and after annealing, the above-described effect cannot be obtained, and | Δr |> 0.2. On the other hand, if the tensile strength exceeds 40% before and after annealing, the crystal grain size becomes too large and rough skin occurs during drawing. The first annealing is preferably performed under conditions where the tensile strength decreases by 15 to 30% before and after annealing.
When the workability of the first cold rolling is less than 10%, the above effect cannot be obtained, and | Δr |> 0.2. In addition, the upper limit of the workability of the first cold rolling is, for example, 97%. When the workability exceeds 97%, the workability of the second cold rolling becomes less than 10%. The workability of the first cold rolling is preferably 15 to 50%.

Cold rolling (initial cold rolling) may be performed between the hot rolling and the first annealing, and the working degree can be set to 0 to 98%.
Other conditions can be made equivalent to the manufacturing conditions of a normal Cu—Co—Si based copper alloy strip.

When the work hardening coefficient (n value) is 0.04 or more, the absolute value of Δr can be surely made 0.2 or less, and the workability of the copper alloy strip is improved, which is preferable.
Here, when a test piece is pulled and a load is applied in a tensile test, each part of the test piece extends uniformly (uniform elongation) in the plastic deformation region exceeding the elastic limit and reaching the maximum load point. In the plastic deformation region where the uniform elongation occurs, there is an equation 1 between the true stress σ _t and the true strain ε _t.
σ _t = Kε _t ⁿ
This relationship is established, and this is called the n-th power hardening rule. “N” is defined as a work hardening coefficient (Kazuto Sudo: Material Testing Method, Uchida Otsukurakusha, (1976), p. 34). n takes a value of 0 ≦ n ≦ 1, and the larger the value of n, the greater the degree of work hardening. When a part that has undergone local deformation is work hardened, the deformation is transferred to other parts, and constriction is less likely to occur. . For this reason, the material with a large n value exhibits uniform elongation, the workability such as deep drawability becomes good, and the surface roughness after processing can be suppressed.
It is preferable that the crystal grain size observed on the rolled surface is 20 μm or less because the workability of the copper alloy strip is improved and the rough surface of the surface after processing can be suppressed.

Using copper as a raw material, copper alloys having the compositions shown in Tables 1 and 2 were melted using an atmospheric melting furnace and cast into ingots. This ingot was hot-rolled at 850 to 1000 ° C., and was appropriately chamfered to a thickness of 10 mm. Thereafter, initial cold rolling was performed under the conditions shown in Tables 1 and 2 (some samples were not subjected to initial cold rolling).
Next, the first annealing and the first cold rolling were repeated twice or three times under the conditions shown in Tables 1 and 2, respectively. Furthermore, solution treatment is performed at 850 to 1000 ° C. for 5 to 100 seconds, followed by final cold rolling at a workability of 0 to 20%, and further aging treatment (5 hours at a temperature at which the strength is maximum). A sample with a thickness of 0.2 mm was manufactured.
Each sample was evaluated as follows.

<Tensile strength (TS)>
The tensile strength (TS) in the direction parallel to the rolling direction was measured by a tensile tester according to JIS-Z2241.

<R value>
A plate with a tensile tester in accordance with JIS-Z2241 in the direction of 0 °, 45 °, 90 ° with respect to the rolling parallel direction and an elongation of 5% (2.5% if the elongation at break is 5% or less) The width and length are measured, the plate width before and after the tensile test is set to W ₀ and W, the length before and after the tensile test is set to L ₀ and L, respectively, and r value = ln (Wo / W) / ln (WL / W _The r value was calculated by ₀ Lo). The r values of 0 degrees, 45 degrees, and 90 degrees with respect to the rolling parallel direction were defined as r0, r45, and r90, respectively.
<Δr value>
<N value> calculated by Δr = (r0 + r90−2 × r45) / 2
When a tensile test is performed in a direction parallel to the rolling direction according to JIS-Z2241, using a tensile tester, the true stress σ _t and the true strain ε _t are obtained in the plastic deformation region.
σ _t = Kε _t ⁿ
I asked for it.

<Crystal grain size observed on rolling surface (average grain size (GS))>
About the rolling surface of the obtained sample, the average crystal grain size was measured by the cutting method of JIS H0501.
<Conductivity (% IACS)>
The conductivity (% IACS) of the obtained sample was measured by the 4-terminal method.
<Drawing workability>
Using an Eriksen tester, a cup was prepared under the conditions of blank diameter: φ64 mm, punch (punch) diameter: φ33 mm, sheet pressure: 3.0 kN, and lubricant: grease.
This cup is placed on a glass plate with the open end side down, and the gap between the recesses and the glass plate between the ears is measured with a reading microscope, and the gap between the four ears generated in the cup is measured. The average value was calculated as ear height.
Further, the appearance of the cup was visually observed to determine the presence or absence of rough skin.
Drawing workability was evaluated according to the following criteria.
○: Ear height is 0.5mm or less and there is no rough skin ×: Ear height exceeds 0.5mm and rough skin occurs

  The obtained results are shown in Table 1. In each example, TS was 550 MPa or more and conductivity was 55% IACS or more.

  As is clear from Tables 1 and 2, the first annealing and the first cold rolling with a workability of 10% or more are repeated twice or more, and the first annealing is 20-40% in tensile strength before and after annealing. In the case of each example manufactured as a decreasing condition, | Δr | ≦ 0.2, and drawing workability was improved.

On the other hand, in the case of Comparative Examples 1 to 4 in which the first annealing was performed so that the tensile strength decreased by more than 40% before and after annealing, | Δr |> 0.2 and the drawability was inferior.
In the case of Comparative Example 5 in which the first annealing and the first cold rolling were repeated only once, | Δr |> 0.2, and the drawing workability was inferior.
Also in the case of Comparative Example 6 in which the first annealing and the first cold rolling were not performed, | Δr |> 0.2, and the drawability was inferior.
Also in the case of Comparative Example 7 in which the workability of the first cold rolling was less than 10%, | Δr |> 0.2, and the drawability was inferior.

Claims (7)

Co: 0.5-3.0% by mass, Si: 0.1-1.0% by mass, Co / Si mass ratio: 3.0-5.0, with the balance consisting of copper and inevitable impurities,
The absolute value of the in-plane anisotropy Δr of the Rankford value r is 0.2 or less (provided that Δr = (r0 + r90-2 × r45) / 2, and 0 degrees, 45 degrees with respect to the rolling parallel direction, Cu-Co-Si-based copper alloy strips having r values of 90 degrees as r0, r45, and r90, respectively. 2. The Cu—Co—Si copper alloy strip according to claim 1, wherein the work hardening coefficient (n value) is 0.04 or more. The Cu-Co-Si-based copper alloy strip according to claim 1 or 2, wherein the crystal grain size observed on the rolled surface is 20 µm or less. Claims containing 0.001 to 2.5% by mass in total of at least one selected from the group consisting of Ni, Cr, Mg, Mn, Ag, P, Sn, Zn, As, Sb, Be, B, Ti, Zr, Al and Fe. Item 3. A Cu—Co—Si copper alloy strip according to item 1 or 2. It is a manufacturing method of the Cu-Co-Si system copper alloy strip according to any one of claims 1 to 4,
Hot rolling, first annealing, first cold rolling with a workability of 10% or more, solution treatment, aging treatment are performed in this order, and the first annealing and the first cold rolling Repeat twice or more,
The first annealing is a method for producing a Cu—Co—Si based copper alloy strip in which the tensile strength is reduced by 10 to 40% before and after annealing.   The electronic component for large currents using the Cu-Co-Si type copper alloy strip of any one of Claims 1-4.   A heat dissipating electronic component using the Cu-Co-Si-based copper alloy strip according to any one of claims 1 to 4.