JP7512845B2 - Copper alloys, copper alloy plastic processing materials, electronic and electrical equipment parts, terminals, bus bars, lead frames, heat dissipation substrates - Google Patents

Description

The present invention relates to a copper alloy suitable for electronic and electrical equipment parts such as terminals, bus bars, lead frames, and heat dissipation substrates, a copper alloy plastic processing material made of this copper alloy, electronic and electrical equipment parts, terminals, bus bars, lead frames, and heat dissipation substrates.

2. Description of the Related Art Conventionally, highly conductive copper or copper alloys have been used for electronic and electric device components such as terminals, bus bars, lead frames, and heat dissipation substrates.
Here, as electronic devices, electric devices, and the like use larger currents, pure copper materials such as oxygen-free copper, which have excellent electrical conductivity, are used in electronic and electric device parts to reduce current density and diffuse heat due to Joule heating.
However, pure copper materials have insufficient heat resistance, which indicates the resistance to a decrease in hardness at high temperatures, and therefore have the problem of being unable to be used in high-temperature environments.
Therefore, Patent Document 1 discloses a copper rolled sheet containing Mg in the range of 0.005 mass% or more and less than 0.1 mass%.

The copper rolled sheet described in Patent Document 1 contains Mg in the range of 0.005 mass% or more and less than 0.1 mass%, with the remainder being Cu and unavoidable impurities. By dissolving Mg in the copper matrix, it was possible to improve heat resistance without significantly reducing electrical conductivity.

JP 2016-056414 A

Recently, in the copper material constituting the above-mentioned electronic and electric device parts, there is a demand for further improving the electrical conductivity in order to sufficiently suppress heat generation when a large current flows through it and to enable use in applications in which pure copper materials have been used. Furthermore, by sufficiently improving the electrical conductivity, it becomes possible to use the copper material satisfactorily in applications in which pure copper materials have been used in the past.
Furthermore, the above-mentioned electronic and electric device parts are often used in high-temperature environments such as engine compartments, and the copper material constituting the electronic and electric device parts needs to have improved heat resistance compared to conventional copper materials.

This invention was made in consideration of the above-mentioned circumstances, and aims to provide copper alloys, copper alloy plastic processing materials, electronic and electrical device parts, terminals, bus bars, lead frames, and heat dissipation substrates that have high electrical conductivity, strength, and excellent heat resistance, and that can simultaneously achieve both strength and stress relaxation resistance properties.

In order to solve this problem, the present inventors have conducted extensive research and have found that in order to achieve a good balance between high electrical conductivity and excellent heat resistance, it is necessary to add a small amount of Mg and to regulate the content of elements that form compounds with Mg. In other words, the inventors have found that by regulating the content of elements that form compounds with Mg and allowing the trace amount of Mg to exist in the copper alloy in an appropriate form, it is possible to improve electrical conductivity and heat resistance to a high level in a good balance compared to conventional levels.
Furthermore, it was found that strength can be improved by specifying the length ratio of low-angle grain boundaries and subgrain boundaries in the grain boundaries.

The present invention has been made based on the above-mentioned findings, and the copper alloy of the present invention has a composition in which the Mg content is in the range of more than 10 ppm by mass and less than 100 ppm by mass, with the balance being Cu and unavoidable impurities, and among the unavoidable impurities, the S content is 10 ppm by mass or less, the P content is 10 ppm by mass or less, the Se content is 5 ppm by mass or less, the Te content is 5 ppm by mass or less, the Sb content is 5 ppm by mass or less, the Bi content is 5 ppm by mass or less, and the As content is 5 ppm by mass or less. The content of S, P, Se, Te, Sb, Bi and As is 5 mass ppm or less, and the total content of S, P, Se, Te, Sb, Bi and As is 30 mass ppm or less. When the content of Mg is [Mg] and the total content of S, P, Se, Te, Sb, Bi and As is [S + P + Se + Te + Sb + Bi + As], the mass ratio [Mg] / [S + P + Se + Te + Sb + Bi + As] is in the range of 0.6 to 50. The electrical conductivity is 97% IACS or more, and the EBSD method is performed to obtain a value of 10,000 μm. The orientation difference of each crystal grain is analyzed for ² or more measurement areas, excluding measurement points where the CI value is 0.1 or less at measurement intervals of 0.25 μm, and the measurement points between which the orientation difference between adjacent measurement points is 15° or more are defined as crystal grain boundaries. The average grain size A is calculated by Area Fraction, and measurements are performed at measurement intervals of 1/10 or less of the average grain size A. Analysis is performed in a measurement area of 10,000 ^μm2 or more in multiple visual fields so that a total of 1,000 or more crystal grains are included, excluding measurement points where the CI value analyzed by data analysis software OIM is 0.1 or less. When the length of the low-angle grain boundary and subgrain boundary between measurement points where the orientation difference between adjacent measurement points is 2° to 15° is defined as _LLB , and the length of the high-angle grain boundary between measurement points where the orientation difference between adjacent measurement points exceeds 15° is defined as _LHB ,
_LLB /( _LLB + _LHB )>20%
The present invention is characterized in that the above relationship is satisfied.

In the copper alloy having this configuration, the contents of Mg and the elements S, P, Se, Te, Sb, Bi, and As which form compounds with Mg are specified as described above. Therefore, the trace amount of Mg added is dissolved in the copper matrix to improve the heat resistance without significantly decreasing the electrical conductivity. Specifically, the electrical conductivity can be made 97% IACS or more.
In addition, when the length of the low-angle grain boundary and the subgrain boundary is _LLB and the length of the high-angle grain boundary is _LHB , the relationship _LLB /( _LLB + _LHB )>20% is satisfied. This makes it possible to improve the strength (yield strength) by work hardening caused by the increase in dislocation density.

In the copper alloy of the present invention, the Ag content is preferably within the range of 5 ppm by mass or more and 20 ppm by mass or less.
In this case, since the Ag content is within the above range, Ag segregates near the grain boundaries, grain boundary diffusion is suppressed, and the stress relaxation resistance can be further improved.

In the copper alloy of the present invention, it is preferable that the tensile strength in a direction parallel to the rolling direction is 200 MPa or more.
In this case, the tensile strength in the direction parallel to the rolling direction is sufficiently high, making the material particularly suitable for use as a material for electronic and electric device parts such as terminals, bus bars, lead frames, and heat dissipation substrates.

Furthermore, in the copper alloy of the present invention, it is preferable that the half-softening temperature is 200° C. or higher.
In this case, since the semi-softening temperature is set to 200° C. or higher, the heat resistance is sufficiently excellent and the material can be used stably even in a high-temperature environment.

The plastically worked copper alloy material of the present invention is characterized by being made of the above-mentioned copper alloy.
The copper alloy plastically worked material of this configuration is excellent in electrical conductivity, strength, and heat resistance because it is composed of the above-mentioned copper alloy, and is particularly suitable as a material for electronic and electric device parts such as terminals, bus bars, lead frames, and heat dissipation substrates used in large current applications and high temperature environments. Examples of the copper alloy plastically worked material of the present invention include plate strip material, cross-sectionally irregular strip material, bar material, wire material, and tube material. Cross-sectionally irregular strip material includes those having a cross-sectional shape in which the thickness varies in the width direction in a cross section perpendicular to the longitudinal direction.

Here, the plastically worked copper alloy material of the present invention may be a rolled plate having a thickness in the range of 0.1 mm to 10 mm.
In this case, since the thickness of the rolled plate is within the range of 0.1 mm or more and 10 mm or less, this copper alloy plastically worked material (rolled plate) can be subjected to punching and bending to form electronic/electrical device parts such as terminals, bus bars, lead frames, and heat dissipation substrates.

In the plastically worked copper alloy material of the present invention, it is preferable that the surface has a Sn-plated layer or an Ag-plated layer.
In this case, since the surface has a Sn plating layer or an Ag plating layer, it is particularly suitable as a material for electronic/electrical device parts such as terminals, bus bars, lead frames, heat dissipation substrates, etc. In the present invention, "Sn plating" includes pure Sn plating or Sn alloy plating, and "Ag plating" includes pure Ag plating or Ag alloy plating.

The electronic/electrical device part of the present invention is characterized in that it is made of the above-mentioned copper alloy plastically worked material. The electronic/electrical device part in the present invention includes terminals, bus bars, lead frames, heat dissipation substrates, etc.
The electronic/electrical device part having this configuration is manufactured using the above-mentioned plastically worked copper alloy material, and therefore can exhibit excellent characteristics even in large current applications and high temperature environments.

The terminal of the present invention is characterized by being made of the above-mentioned plastically worked copper alloy material.
The terminal having this configuration is manufactured using the above-mentioned copper alloy plastically processed material, and therefore can exhibit excellent characteristics even in large current applications and high temperature environments.

The bus bar of the present invention is characterized by being made of the above-mentioned plastically worked copper alloy material.
The busbar having this configuration is manufactured using the above-mentioned copper alloy plastically processed material, and therefore can exhibit excellent characteristics even in high current applications and high temperature environments.

The lead frame of the present invention is characterized in that it is made of the above-mentioned plastically worked copper alloy material.
The lead frame having this configuration is manufactured using the above-mentioned copper alloy plastically processed material, and therefore can exhibit excellent characteristics even in high current applications and high temperature environments.

The heat dissipation board of the present invention is characterized in that it is made of the above-mentioned copper alloy.
The heat dissipation board of this configuration is made of the above-mentioned copper alloy, and therefore can exhibit excellent characteristics even in large current applications and high temperature environments.

The present invention makes it possible to provide copper alloys, copper alloy plastic processing materials, electronic and electrical device parts, terminals, bus bars, lead frames, and heat dissipation substrates that have high electrical conductivity, strength, and excellent heat resistance, while also achieving both strength and stress relaxation resistance.

FIG. 1 is a flow diagram of a method for producing a copper alloy according to an embodiment of the present invention.

Hereinafter, a copper alloy according to one embodiment of the present invention will be described.
The copper alloy of this embodiment has a composition in which the Mg content is in the range of more than 10 ppm by mass and less than 100 ppm by mass, with the balance being Cu and inevitable impurities. Of the inevitable impurities, the S content is 10 ppm by mass or less, the P content is 10 ppm by mass or less, the Se content is 5 ppm by mass or less, the Te content is 5 ppm by mass or less, the Sb content is 5 ppm by mass or less, the Bi content is 5 ppm by mass or less, and the As content is 5 ppm by mass or less. The total content of S, P, Se, Te, Sb, Bi, and As is 30 ppm by mass or less.

If the content of Mg is defined as [Mg] and the total content of S, P, Se, Te, Sb, Bi, and As is defined as [S+P+Se+Te+Sb+Bi+As], the mass ratio thereof, [Mg]/[S+P+Se+Te+Sb+Bi+As], is within the range of 0.6 or more and 50 or less.
In the copper alloy of this embodiment, the Ag content may be within the range of 5 ppm by mass or more and 20 ppm by mass or less.

In addition, the copper alloy of this embodiment has a conductivity of 97% IACS or more.
In the copper alloy of this embodiment, the orientation difference of each crystal grain is analyzed by the EBSD method in a measurement area of ^10,000 μm2 or more, excluding measurement points where the CI value is 0.1 or less at a measurement interval of 0.25 μm, and the measurement points between which the orientation difference between adjacent measurement points is 15° or more are defined as crystal grain boundaries. The average grain size A is obtained by Area Fraction, and measurements are performed at measurement intervals of 1/10 or less of the average grain size A. Analysis is performed in a measurement area of ^10,000 μm2 or more in multiple visual fields so that a total of 1,000 or more crystal grains are included, excluding measurement points where the CI value analyzed by data analysis software OIM is 0.1 or less. When the length of the low-angle grain boundary and the subgrain boundary between measurement points where the orientation difference between adjacent measurement points is 2° to 15° is defined as _{LLB ,} and the length of the high-angle grain boundary between measurement points where the orientation difference between adjacent measurement points exceeds 15° is defined as _LHB , /( _LLB + _LHB )>20%.

In the copper alloy of this embodiment, the tensile strength in a direction parallel to the rolling direction is preferably 200 MPa or more.
In addition, in the copper alloy of this embodiment, the half-softening temperature is preferably 200° C. or higher.

Here, we will explain the reasons why the composition, structure, and various properties of the copper alloy of this embodiment are specified as described above.

(Mg)
Mg is an element that has the effect of improving the strength and heat resistance without significantly decreasing the electrical conductivity by dissolving in the copper matrix. Furthermore, dissolving Mg in the copper matrix improves the stress relaxation resistance.
If the Mg content is 10 ppm by mass or less, the effect of the Mg may not be sufficiently exhibited, whereas if the Mg content is 100 ppm by mass or more, the electrical conductivity may decrease.
For the above reasons, in this embodiment, the Mg content is set within the range of more than 10 ppm by mass and less than 100 ppm by mass.

In order to further improve the heat resistance and strength, the lower limit of the Mg content is preferably 20 ppm by mass or more, more preferably 30 ppm by mass or more, and even more preferably 40 ppm by mass or more.
In order to further suppress the decrease in electrical conductivity, the upper limit of the Mg content is preferably less than 90 ppm by mass, more preferably less than 80 ppm by mass, and even more preferably less than 70 ppm by mass.

(S, P, Se, Te, Sb, Bi, As)
The above-mentioned elements S, P, Se, Te, Sb, Bi, and As are generally elements that tend to be mixed into copper alloys. These elements tend to react with Mg to form compounds, which may reduce the solid solution effect of the trace amount of Mg added. For this reason, the contents of these elements need to be strictly controlled.
Therefore, in this embodiment, the S content is limited to 10 ppm by mass or less, the P content is limited to 10 ppm by mass or less, the Se content is limited to 5 ppm by mass or less, the Te content is limited to 5 ppm by mass or less, the Sb content is limited to 5 ppm by mass or less, the Bi content is limited to 5 ppm by mass or less, and the As content is limited to 5 ppm by mass or less.
Furthermore, the total content of S, P, Se, Te, Sb, Bi and As is limited to 30 mass ppm or less.

The S content is preferably 9 ppm by mass or less, and more preferably 8 ppm by mass or less.
The P content is preferably 6 mass ppm or less, and more preferably 3 mass ppm or less.
The Se content is preferably 4 mass ppm or less, and more preferably 2 mass ppm or less.
The content of Te is preferably 4 mass ppm or less, and more preferably 2 mass ppm or less.
The Sb content is preferably 4 mass ppm or less, and more preferably 2 mass ppm or less.
The Bi content is preferably 4 mass ppm or less, and more preferably 2 mass ppm or less.
The As content is preferably 4 mass ppm or less, and more preferably 2 mass ppm or less.
Furthermore, the total content of S, P, Se, Te, Sb, Bi and As is preferably 24 mass ppm or less, and more preferably 18 mass ppm or less.

([Mg]/[S+P+Se+Te+Sb+Bi+As])
As described above, elements such as S, P, Se, Te, Sb, Bi, and As tend to react with Mg to form compounds, and therefore in this embodiment, the form of Mg is controlled by defining the ratio of the Mg content to the total content of S, P, Se, Te, Sb, Bi, and As.
When the content of Mg is [Mg] and the total content of S, P, Se, Te, Sb, Bi and As is [S+P+Se+Te+Sb+Bi+As], if the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] exceeds 50, Mg is present in the copper in an excessive solid solution state, and the electrical conductivity may decrease. On the other hand, if the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] is less than 0.6, Mg is not sufficiently dissolved, and the heat resistance and stress relaxation resistance properties may not be sufficiently improved.
Therefore, in this embodiment, the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] is set within the range of 0.6 or more and 50 or less.

In order to further suppress the decrease in electrical conductivity, the upper limit of the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] is preferably set to 35 or less, and more preferably set to 25 or less.
In order to further improve the heat resistance and stress relaxation resistance, the lower limit of the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] is preferably set to 0.8 or more, and more preferably set to 1.0 or more.

(Ag: 5 mass ppm or more and 20 mass ppm or less)
Ag is hardly able to dissolve in the Cu matrix at temperatures below 250°C, which is the temperature range used for typical electronic and electrical equipment. Therefore, a small amount of Ag added to copper segregates near the grain boundaries. This prevents the movement of atoms at the grain boundaries and suppresses grain boundary diffusion, improving heat resistance and stress relaxation resistance.
When the Ag content is 5 ppm by mass or more, the effect of the composition can be sufficiently exhibited, whereas when the Ag content is 20 ppm by mass or less, the electrical conductivity is ensured and an increase in the manufacturing cost can be suppressed.
For the above reasons, in this embodiment, the Ag content is set within the range of 5 ppm by mass or more and 20 ppm by mass or less.

In order to further improve the heat resistance and stress relaxation resistance, the lower limit of the Ag content is preferably 6 mass ppm or more, more preferably 7 mass ppm or more, and more preferably 8 mass ppm or more. In order to reliably suppress the decrease in electrical conductivity and the increase in cost, the upper limit of the Ag content is preferably 18 mass ppm or less, more preferably 16 mass ppm or less, and more preferably 14 mass ppm or less.
In addition, when Ag is not intentionally contained but is contained as an impurity, the Ag content may be less than 5 ppm by mass.

(Other unavoidable impurities)
Examples of inevitable impurities other than the above-mentioned elements include Al, B, Ba, Be, Ca, Cd, Cr, Sc, rare earth elements, V, Nb, Ta, Mo, Ni, W, Mn, Re, Ru, Sr, Ti, Os, Co, Rh, Ir, Pb, Pd, Pt, Au, Zn, Zr, Hf, Hg, Ga, In, Ge, Y, Tl, N, Si, Sn, Li, etc. These inevitable impurities may be contained to the extent that they do not affect the characteristics.
Here, since these unavoidable impurities may reduce electrical conductivity, the total amount is preferably 0.1 mass% or less, more preferably 0.05 mass% or less, even more preferably 0.03 mass% or less, and further preferably 0.01 mass% or less.
The upper limit of the content of each of these unavoidable impurities is preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, and even more preferably 2 ppm by mass or less.

(Low angle grain boundary and subgrain boundary length ratio: _LLB /( _LLB + _LHB ))
Since low-angle grain boundaries and subgrain boundaries are regions with a high density of dislocations introduced during processing, by controlling the structure so that the length ratio _LLB /( _LLB + _LHB ) of low-angle grain boundaries and subgrain boundaries among all grain boundaries exceeds 20%, it is possible to improve strength (yield strength) through work hardening caused by an increase in dislocation density.

In addition, the low angle grain boundary and subgrain boundary length ratio _LLB /( _LLB + _LHB ) is preferably 25% or more, and more preferably 30% or more, even within the above range. On the other hand, if the low angle grain boundary and subgrain boundary length ratio _LLB /( _LLB + _LHB ) is too high, high-speed diffusion of atoms through dislocations is likely to occur, and recrystallization and the associated softening in a high-temperature environment are likely to occur, which may impair heat resistance. Therefore, the low angle grain boundary and subgrain boundary length ratio _LLB /( _LLB + _LHB ) is preferably 80% or less, and more preferably 70% or less.

(Conductivity: 97% IACS or higher)
In the copper alloy of this embodiment, the electrical conductivity is set to 97% IACS or more. By setting the electrical conductivity to 97% IACS or more, heat generation during energization can be suppressed, and the copper alloy can be favorably used as a substitute for pure copper material for electronic and electric device parts such as terminals, bus bars, lead frames, and heat dissipation substrates.
The electrical conductivity is preferably 97.5% IACS or more, more preferably 98.0% IACS or more, even more preferably 98.5% IACS or more, and even more preferably 99.0% IACS or more.

(Tensile strength in a direction parallel to the rolling direction: 200 MPa or more)
In the copper alloy of this embodiment, when the tensile strength in the direction parallel to the rolling direction is 200 MPa or more, the alloy is particularly suitable as a material for electronic and electric device parts such as terminals, bus bars, lead frames, etc. Although there is no particular upper limit for the tensile strength in the direction parallel to the rolling direction, it is preferable that the tensile strength in the direction parallel to the rolling direction is 500 MPa or less in order to avoid a decrease in productivity due to the coil winding tendency when using a coil-wound strip material.
The lower limit of the tensile strength in the direction parallel to the rolling direction is more preferably 275 MPa or more, and even more preferably 300 MPa or more.

(Semi-softening temperature: 200°C or higher)
In the copper alloy of this embodiment, when the semi-softening temperature is high, the softening phenomenon due to recovery and recrystallization of the copper material is unlikely to occur even at high temperatures, making it possible to apply the alloy to current-carrying members used in high-temperature environments.
For this reason, in this embodiment, it is preferable that the semi-softening temperature in the 1-hour heat treatment is equal to or higher than 200° C. In this embodiment, the semi-softening temperature was evaluated by measuring the Vickers hardness.
The semi-softening temperature in the 1-hour heat treatment is more preferably 225° C. or higher, even more preferably 250° C. or higher, and even more preferably 275° C. or higher.

Next, the method for producing the copper alloy according to this embodiment will be described with reference to the flow diagram shown in FIG.

(Melting and casting process S01)
First, the copper raw material is melted, and the above-mentioned elements are added to the molten copper obtained to adjust the composition, thereby producing a molten copper alloy. In addition, the various elements can be added in the form of single elements or master alloys. In addition, raw materials containing the above-mentioned elements may be melted together with the copper raw material. In addition, recycled materials and scrap materials of this alloy may be used.
Here, the copper raw material is preferably so-called 4NCu having a purity of 99.99 mass% or more, or so-called 5NCu having a purity of 99.999 mass% or more.

During melting, in order to suppress oxidation of Mg and to reduce the hydrogen concentration, it is preferable to carry out atmospheric melting in an inert gas atmosphere (e.g., Ar gas) with a low vapor pressure of H ₂ O, and to keep the holding time during melting to a minimum.
The molten copper alloy having the adjusted composition is then poured into a mold to produce an ingot. When mass production is taken into consideration, it is preferable to use a continuous casting method or a semi-continuous casting method.

(Homogenization/solution process S02)
Next, a heat treatment is performed to homogenize and dissolve the obtained ingot. In the ingot, intermetallic compounds mainly composed of Cu and Mg may be present due to the segregation and concentration of Mg during the solidification process. In order to eliminate or reduce these segregations and intermetallic compounds, the ingot is heated to 300°C or higher and 1080°C or lower, thereby homogenizing Mg in the ingot or dissolving Mg in the parent phase. The homogenization/solution process S02 is preferably performed in a non-oxidizing or reducing atmosphere.

Here, if the heating temperature is less than 300°C, the solution treatment is incomplete, and there is a risk that a large amount of intermetallic compounds mainly composed of Cu and Mg will remain in the parent phase. On the other hand, if the heating temperature exceeds 1080°C, a part of the copper material will become liquid, and there is a risk that the structure and surface state will become non-uniform. Therefore, the heating temperature is set in the range of 300°C to 1080°C.
In order to improve the efficiency of the rough rolling and to homogenize the structure, hot working may be performed after the homogenization/solution treatment step S02. In this case, the processing method is not particularly limited, and for example, rolling, drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, the hot working temperature is preferably in the range of 300°C to 1080°C.

(Rough processing step S03)
In order to process the steel into a predetermined shape, rough processing is performed. The temperature conditions in the rough processing step S03 are not particularly limited, but in order to suppress recrystallization or to improve dimensional accuracy, it is preferable to set the temperature within the range of -200°C to 200°C, which is cold or warm rolling, and room temperature is particularly preferable. The processing rate is preferably 20% or more, and more preferably 30% or more. The processing method is not particularly limited, and for example, rolling, drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted.

(Intermediate heat treatment step S04)
After the rough processing step S03, a heat treatment is carried out to form a recrystallized structure. Note that the intermediate heat treatment step S04 and the upper pre-processing step S05 described later may be repeatedly carried out.
Here, since the intermediate heat treatment step S04 is substantially the last recrystallization heat treatment, the grain size of the recrystallized structure obtained in this step is almost equal to the final grain size. Therefore, in the intermediate heat treatment step S04, it is preferable to select the heat treatment conditions appropriately so that the average grain size becomes 5 μm or more. For example, it is preferable to hold at 700° C. for about 1 to 120 seconds.

(Upper processing step S05)
In order to process the copper material after the intermediate heat treatment step S04 into a predetermined shape, the copper material is subjected to upper pre-processing. The temperature conditions in this upper pre-processing step S05 are not particularly limited, but in order to suppress recrystallization during processing or to suppress softening, it is preferable to set the temperature within the range of -200°C to 200°C, which is cold or warm processing, and room temperature is particularly preferable.
The processing rate is appropriately selected so as to approximate the final shape, but in order to increase the length ratio of the low-angle grain boundaries and subgrain boundaries in the upper pre-processing step S05 and improve the strength by work hardening, the processing rate is preferably 10% or more. In order to further improve the strength, the processing rate is more preferably 15% or more, and even more preferably 20% or more. On the other hand, in order to suppress deterioration of bending workability due to an excessive increase in the low-angle grain boundaries and subgrain boundaries, the processing rate is preferably 95% or less, and more preferably 90% or less. In addition, the processing rate is generally the reduction rate of area in rolling or wire drawing.

(Mechanical surface treatment step S06)
After the upper pre-processing step S05, a mechanical surface treatment is performed. The mechanical surface treatment is a treatment for applying a compressive stress to the vicinity of the surface after the desired shape is almost obtained, and has the effect of improving the stress relaxation resistance characteristic.
As the mechanical surface treatment, various commonly used methods can be used, such as shot peening, blasting, lapping, polishing, buffing, grinder polishing, sandpaper polishing, tension leveler treatment, and light rolling with a low reduction rate per pass (a reduction rate per pass of 1 to 10%, repeated three or more times).
By subjecting a copper alloy containing Mg to this mechanical surface treatment, the stress relaxation resistance is significantly improved.

(Finishing heat treatment step S07)
Next, the plastically worked material obtained by the mechanical surface treatment step S06 may be subjected to a finish heat treatment in order to remove segregation of contained elements to grain boundaries and residual strain.
At this time, if the heat treatment temperature is too high, the low angle grain boundary and subgrain boundary length ratio _LLB /( _LLB + _LHB ) will be significantly reduced, so the heat treatment temperature is preferably in the range of 100°C to 800°C. In addition, in this finish heat treatment step S07, it is necessary to set the heat treatment conditions so as to avoid a significant reduction in strength due to recrystallization. For example, it is preferable to hold at 450°C for about 0.1 to 10 seconds, and at 250°C for 1 minute to 100 hours. This heat treatment is preferably performed in a non-oxidizing atmosphere or a reducing atmosphere. There is no particular limitation on the heat treatment method, but short-term heat treatment using a continuous annealing furnace is preferable in terms of the effect of reducing manufacturing costs.
Furthermore, the above-mentioned upper pre-processing step S05, the mechanical surface treatment step S06, and the finish heat treatment step S07 may be repeatedly performed.

In this manner, the copper alloy (plastically worked copper alloy material) according to the present embodiment is produced. The plastically worked copper alloy material produced by rolling is called a rolled copper alloy sheet.
Here, when the thickness of the plastically worked copper alloy material is 0.1 mm or more, it is suitable for use as a conductor in large current applications. Also, when the thickness of the plastically worked copper alloy material is 10.0 mm or less, an increase in the load of a press machine can be suppressed, productivity per unit time can be ensured, and manufacturing costs can be reduced.
For this reason, the sheet thickness of the plastically worked copper alloy material (rolled copper alloy material) is preferably within a range of 0.1 mm to 10.0 mm.
The lower limit of the sheet thickness of the plastically worked copper alloy material (rolled copper alloy material) is preferably 0.5 mm or more, more preferably 1.0 mm or more, while the upper limit of the sheet thickness of the plastically worked copper alloy material (rolled copper alloy material) is preferably less than 9.0 mm, more preferably less than 8.0 mm.

In the copper alloy of this embodiment configured as described above, the Mg content is in the range of more than 10 mass ppm and less than 100 mass ppm, the S content, which is an element that forms a compound with Mg, is 10 mass ppm or less, the P content is 10 mass ppm or less, the Se content is 5 mass ppm or less, the Te content is 5 mass ppm or less, the Sb content is 5 mass ppm or less, the Bi content is 5 mass ppm or less, the As content is 5 mass ppm or less, and further, the total content of S, P, Se, Te, Sb, Bi, and As is limited to 30 mass ppm or less, so that the trace amount of added Mg can be dissolved in the copper matrix, and the heat resistance can be improved without significantly decreasing the electrical conductivity.

Furthermore, when the content of Mg is [Mg] and the total content of S, P, Se, Te, Sb, Bi, and As is [S+P+Se+Te+Sb+Bi+As], the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] is set within the range of 0.6 or more and 50 or less, so it is possible to sufficiently improve the heat resistance without reducing the electrical conductivity due to excessive Mg dissolving in the material.
Therefore, according to the copper alloy of this embodiment, the electrical conductivity can be made 97% IACS or more, and it is possible to achieve both high electrical conductivity and excellent heat resistance.

In addition, when the length of the low-angle grain boundary and the subgrain boundary is _LLB and the length of the high-angle grain boundary is _LHB , the relationship _LLB /( _LLB + _LHB )>20% is satisfied. This makes it possible to improve the strength (yield strength) by work hardening caused by the increase in dislocation density.
Therefore, it is particularly suitable as a material for electronic and electric device components such as terminals, bus bars, lead frames, and heat dissipation substrates.

In this embodiment, when the Ag content is within the range of 5 ppm by mass or more and 20 ppm by mass or less, Ag segregates near the grain boundaries, suppressing grain boundary diffusion and improving stress relaxation resistance.

Furthermore, in this embodiment, when the tensile strength in the direction parallel to the rolling direction is 200 MPa or more, the tensile strength in the direction parallel to the rolling direction is sufficiently high, and the material is particularly suitable as a material for electronic and electric device components such as terminals, bus bars, lead frames, and heat dissipation substrates.
Furthermore, in this embodiment, when the semi-softening temperature is set to 200° C. or higher, the heat resistance is sufficiently excellent and the material can be stably used even in a high-temperature environment.

The copper alloy plastically processed material of this embodiment is made of the copper alloy described above, and therefore has excellent electrical conductivity, strength, heat resistance, and stress relaxation resistance properties, and is particularly suitable as a material for electronic and electric device components such as terminals, bus bars, lead frames, and heat dissipation substrates.
Furthermore, when the plastically worked copper alloy material of this embodiment is made into a rolled plate having a thickness in the range of 0.1 mm to 10 mm, the plastically worked copper alloy material (rolled plate) can be punched or bent to relatively easily form electronic/electrical device parts such as terminals, bus bars, lead frames, and heat dissipation substrates.
In addition, when a Sn plating layer or an Ag plating layer is formed on the surface of the copper alloy plastically worked material of this embodiment, it is particularly suitable as a material for electronic and electric device parts such as terminals, bus bars, lead frames, and heat dissipation substrates.

Furthermore, the electronic/electrical device components (terminals, bus bars, lead frames, heat dissipation substrates, etc.) of this embodiment are made of the above-mentioned copper alloy plastic processing material, so they can exhibit excellent characteristics even in high current applications and high temperature environments.

The copper alloy, the copper alloy plastically worked material, and the electronic/electrical device parts (terminals, bus bars, lead frames, heat dissipation substrates, etc.) according to the embodiments of the present invention have been described above. However, the present invention is not limited thereto, and appropriate modifications can be made without departing from the technical spirit of the invention.
For example, in the above-described embodiment, an example of a manufacturing method of a copper alloy (copper alloy plastically worked material) has been described, but the manufacturing method of the copper alloy is not limited to that described in the embodiment, and the copper alloy may be manufactured by appropriately selecting an existing manufacturing method.

The results of confirmation experiments carried out to confirm the effects of the present invention will be described below.
A raw material made of pure copper having a purity of 99.999 mass% or more, which was produced by a zone melting refining method, was placed in a high-purity graphite crucible and melted by high-frequency induction in an atmospheric furnace filled with an Ar gas atmosphere.

Various 0.1 mass% master alloys made from high purity copper of 6N or more (purity 99.9999 mass%) and pure metals with a purity of 2N or more (purity 99 mass%) were added to the obtained molten copper to adjust the composition, and the molten copper was poured into a mold made of insulating material (isowool) to produce ingots with the composition shown in Tables 1 and 2. The size of the ingot was approximately 30 mm thick x 60 mm wide x 150 to 200 mm long.

The obtained ingot was heated in an Ar gas atmosphere at 900° C. for 1 hour to dissolve the Mg, and the surface was ground to remove the oxide film, and then cut to a predetermined size.
The thickness was then adjusted appropriately to the final thickness and cut. Each cut sample was roughly rolled under the conditions shown in Tables 3 and 4, and then intermediate heat treatment was performed under conditions that would result in a crystal grain size of about 30 μm due to recrystallization.

Next, upper pre-rolling (upper pre-processing step) was carried out under the conditions shown in Tables 3 and 4.
These samples were then subjected to a mechanical surface treatment process according to the methods described in Tables 3 and 4.
The sandpaper polishing was carried out using #320 abrasive paper.
The lapping process was carried out using alumina-based abrasive grains and a cast iron lap.
The shot peening treatment was carried out using stainless steel shots having a diameter of 0.1 mm at a projection speed of 5 m/sec for a projection time of 10 sec.
Thereafter, a final heat treatment was carried out under the conditions shown in Tables 3 and 4, and strip materials having the thickness and width of approximately 60 mm shown in Tables 3 and 4 were produced.

The resulting strips were evaluated for the following items:

(Composition Analysis)
Measurement samples were taken from the resulting ingot, and Mg was measured by inductively coupled plasma atomic emission spectrometry, and other elements were measured using a glow discharge mass spectrometer (GD-MS). Measurements were performed at two locations, the center and the end in the width direction, and the content of the sample with the greater content was recorded. As a result, it was confirmed that the composition was as shown in Tables 1 and 2.

(conductivity)
A test piece with a width of 10 mm and a length of 60 mm was taken from the strip material for property evaluation, and the electrical resistance was measured by a four-terminal method. The dimensions of the test piece were measured using a micrometer, and the volume of the test piece was calculated. The electrical conductivity was calculated from the measured electrical resistance value and volume. The test piece was taken so that its longitudinal direction was parallel to the rolling direction of the strip material for property evaluation. The evaluation results are shown in Tables 3 and 4.

(Low angle grain boundary and subgrain boundary length ratio)
The rolled surface, i.e., the ND (normal direction) surface, was used as the observation surface, and the length ratios of the low-angle grain boundaries and the subgrain boundaries were determined as follows using an EBSD measuring device and OIM analysis software.
After mechanical polishing using water-resistant polishing paper and diamond abrasive grains, finish polishing was performed using colloidal silica solution.Then, using an EBSD measuring device (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX/TSL (now AMETEK)) and analysis software (OIM Data Analysis ver.7.3.1 manufactured by EDAX/TSL (now AMETEK)), the accelerating voltage of the electron beam was 15 kV, the measurement area was 10,000 μm ² or more, and the measurement points with CI value of 0.1 or less were excluded at the measurement interval of 0.25 μm, and the measurement points with the orientation difference between adjacent measurement points of 15° or more were regarded as grain boundaries, and the average grain size A was obtained by Area Fraction using data analysis software OIM. Thereafter, measurements were made at intervals of one-tenth or less of the average grain size A, and an analysis was performed over a measurement area of ^10,000 μm2 or more in multiple visual fields so that a total of 1,000 or more crystal grains were included, excluding measurement points for which the CI value analyzed by the data analysis software OIM was 0.1 or less. Measurement points between which the orientation difference between adjacent measurement points was 2° or more and 15° or less were defined as low-angle grain boundaries and subgrain boundaries, with their length defined as _LLB , and measurement points between which the orientation difference was more than 15° were defined as high-angle grain boundaries and their length defined as _LHB , thereby determining the length ratio _LLB /( _LLB + _LHB ) of the low-angle grain boundaries and subgrain boundaries among all grain boundaries.

(Stress relaxation resistance)
The stress relaxation resistance test was conducted in accordance with the Japan Copper and Brass Association technical standard JCBA-T309:2004, in which stress was applied using a method conforming to the cantilever screw method, and the residual stress rate was measured after holding for 1000 hours at a temperature of 150° C. The evaluation results are shown in Tables 3 and 4.
The test method was to cut test pieces (width 10 mm) from each strip material for property evaluation in a direction parallel to the rolling direction, set the initial deflection displacement to 2 mm, and adjust the span length so that the surface maximum stress of the test piece was 80% of the yield strength. The above surface maximum stress is determined by the following formula.
Maximum surface stress ( ^MPa ) = _1.5Etδ0 / _Ls2
however,
E: Young's modulus (MPa)
t: thickness of sample (mm)
δ ₀ : Initial deflection displacement (mm)
_Ls : span length (mm)
It is.
Residual stress rate was measured from bending tendency after holding at 150° C. for 1000 hours, and stress relaxation resistance was evaluated. The residual stress rate was calculated using the following formula.
Residual stress rate (%) = (1 - δ _t /δ ₀ ) x 100
however,
_δt : Permanent deflection displacement (mm) after 1000 hours at 150°C - Permanent deflection displacement (mm) after 24 hours at room temperature
δ ₀ : Initial deflection displacement (mm)
It is.

(Mechanical properties)
A No. 13B test piece specified in JIS Z 2241 was taken from the strip material for property evaluation, and the tensile strength was measured by the offset method of JIS Z 2241. The test piece was taken in a direction parallel to the rolling direction. The evaluation results are shown in Tables 3 and 4.

(Vickers hardness)
In accordance with the micro Vickers hardness test method specified in JIS-Z2244, the Vickers hardness was measured on the surface of the strip material for property evaluation, i.e., the ND surface (Normal Direction), with a test load of 0.98 N. The evaluation results are shown in Tables 3 and 4.

(half-softening temperature)
The semi-softening temperature was evaluated by obtaining an isochronal softening curve based on Vickers hardness after one hour of heat treatment in accordance with JCBA T325:2013 of the Japan Copper and Brass Association. The Vickers hardness was measured on the rolled surface. The evaluation results are shown in Tables 3 and 4.

In Comparative Example 1, the Mg content was lower than the range of the present invention, and therefore the half-softening temperature was low and the heat resistance was insufficient. Also, the residual stress rate was low and the stress relaxation resistance characteristics were insufficient.
In Comparative Example 2, the Mg content exceeded the range of the present invention, resulting in low electrical conductivity.
In Comparative Example 3, the total content of S, P, Se, Te, Sb, Bi, and As exceeded 30 mass ppm, the residual stress rate was low, and the stress relaxation resistance was insufficient. In addition, the semi-softening temperature was low, and the heat resistance was insufficient.
In Comparative Example 4, the mass ratio [Mg]/[S+P+Se+Te+Sb+Bi+As] was less than 0.6, the residual stress rate was low, and the stress relaxation resistance was insufficient. In addition, the semi-softening temperature was low, and the heat resistance was insufficient.
In Comparative Example 5, the low angle grain boundary and subgrain boundary length ratio _LLB /( _LLB + _LHB ) was lower than the range of the present invention, and therefore the tensile strength and hardness were low.

In contrast, it was confirmed that in Examples 1 to 24 of the present invention, the electrical conductivity, strength, heat resistance, and stress relaxation resistance were improved in a well-balanced manner.
From the above, it was confirmed that the present invention can provide a copper alloy having high electrical conductivity, strength, and excellent heat resistance, and also capable of achieving both strength and stress relaxation resistance.

Claims (12)

The composition has a Mg content in the range of more than 10 ppm by mass and less than 100 ppm by mass, with the balance being Cu and unavoidable impurities, and among the unavoidable impurities, the S content is 10 ppm by mass or less, the P content is 10 ppm by mass or less, the Se content is 5 ppm by mass or less, the Te content is 5 ppm by mass or less, the Sb content is 5 ppm by mass or less, the Bi content is 5 ppm by mass or less, and the As content is 5 ppm by mass or less, and the total content of S, P, Se, Te, Sb, Bi, and As is 30 ppm by mass or less,
When the content of Mg is [Mg] and the total content of S, P, Se, Te, Sb, Bi and As is [S+P+Se+Te+Sb+Bi+As], the mass ratio thereof, [Mg]/[S+P+Se+Te+Sb+Bi+As], is within a range of 0.6 or more and 50 or less,
The electrical conductivity is 97% IACS or more.
By the EBSD method, the orientation difference of each crystal grain is analyzed in a measurement area of ^10,000 μm2 or more, excluding measurement points where the CI value is 0.1 or less at measurement intervals of 0.25 μm, and the measurement points between which the orientation difference between adjacent measurement points is 15° or more are defined as crystal grain boundaries. The average grain size A is calculated by Area Fraction, and measurements are performed at measurement intervals of 1/10 or less of the average grain size A. Analysis is performed in a measurement area of 10,000 ^μm2 or more in multiple visual fields so that a total of 1,000 or more crystal grains are included, excluding measurement points where the CI value analyzed by data analysis software OIM is 0.1 or less. When the length of the low-angle grain boundary and subgrain boundary between measurement points where the orientation difference between adjacent measurement points is 2° to 15° is defined as _LLB , and the length of the high-angle grain boundary between measurement points where the orientation difference between adjacent measurement points exceeds 15° is defined as _LHB ,
_LLB /( _LLB + _LHB )>20%
A copper alloy characterized in that: The copper alloy according to claim 1, characterized in that the Ag content is in the range of 5 mass ppm to 20 mass ppm. The copper alloy according to claim 1 or 2, characterized in that the tensile strength in the direction parallel to the rolling direction is 200 MPa or more. The copper alloy according to any one of claims 1 to 3, characterized in that the half-softening temperature is 200°C or higher. A copper alloy plastic processing material comprising the copper alloy according to any one of claims 1 to 4. The copper alloy plastically processed material according to claim 5, characterized in that it is a rolled plate having a thickness in the range of 0.1 mm to 10 mm. The copper alloy plastically processed material according to claim 5 or 6, characterized in that it has a Sn-plated layer or an Ag-plated layer on its surface. A component for electronic/electrical equipment, comprising a plastically worked copper alloy material according to any one of claims 5 to 7. A terminal made of a plastically processed copper alloy material according to any one of claims 5 to 7. A busbar made of a copper alloy plastically processed material according to any one of claims 5 to 7. A lead frame made of the copper alloy plastic processing material described in any one of claims 5 to 7. A heat dissipation substrate made using the copper alloy described in any one of claims 1 to 4.

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