JP7234501B2 - Copper alloy - Google Patents

Description

The present invention relates to copper alloys suitable for electrical and electronic device parts such as home appliances, semiconductor parts such as lead frames, printed wiring boards, heat sinks, switch parts, busbars, connectors and the like.

Cu--Fe--P alloys containing Fe and P have been widely used as copper alloys for the various uses described above.
A Cu—Fe—P alloy is a precipitation-strengthened alloy in which an intermetallic compound such as Fe or Fe—P is precipitated in a copper matrix, and is excellent in strength, electrical conductivity, and thermal conductivity. , are widely used in a variety of applications.
In recent years, with the expansion of the use of Cu-Fe-P alloys and the reduction in the weight, thickness and size of electrical and electronic equipment, the strength of Cu-Fe-P alloys has been further increased. High electrical conductivity and good thermal conductivity are required.

Here, when producing parts for electric/electronic devices such as lead frames from a plate material of Cu--Fe--P alloy, it is common to process it into a multi-pin shape by stamping (press punching). be.
Recently, the number of pins has been increasing, and along with this, distortion tends to remain in the stamped product, and the shape of the pins tends to be uneven.

Therefore, a heat treatment for strain relief is sometimes performed on a multi-pin shaped product obtained by stamping.
However, when such a heat treatment is performed, the material is softened, the strength is lowered, and there is a possibility that the necessary strength cannot be secured. Moreover, in order to improve productivity, the heat treatment described above is required to be performed at a higher temperature in a shorter time.
Therefore, the Cu--Fe--P alloys are required to have heat resistance to ensure sufficient strength even after heat treatment.

Therefore, for example, Patent Documents 1 to 3 propose a Cu--Fe--P alloy in which fine precipitate particles are dispersed to improve heat resistance.
For example, Patent Document 1 proposes a Cu--Fe--P alloy in which the existence density of precipitated particles of Fe or Fe--P compounds with an equivalent circle diameter of 10 to 40 nm is 20/μm ^{2 or} more.

In Patent Document 2, in observation with a transmission electron microscope, the peak value in the histogram of the diameter of precipitate particles per 1 μm ² is within the range of 15 to 35 nm in diameter, and the precipitate particles with a diameter within this range are A Cu--Fe--P-based alloy has been proposed that exists at a frequency of 50% or more of the total frequency and has a half width of 25 nm or less.

In Patent Document 3, among the Fe-containing particles dispersed in the copper matrix, the ratio N of the number density N ₁ of particles having a diameter larger than 50 nm and the number density N ₂ of particles having a diameter of 50 nm or less A Cu--Fe--P alloy has been proposed in which ₂ / _N1 is 5 or more and the average particle spacing of particles having a diameter of 10 nm or more and 50 nm or less is 50 nm or more and 300 nm or less. In addition, in paragraph number 0029 of this patent document 3, "Since Fe particles with a diameter of 20 nm or less are sheared and absorbed by the grain boundary and re-dissolved, the pinning effect cannot be expected (recrystallization cannot be suppressed. , causing a decrease in strength).”

JP 2015-134955 A Republished WO2011/021245 JP 2012-107297 A

By the way, for example, when a semiconductor element is mounted on a component for an electric/electronic device such as a lead frame, a joining method using solder is applied. In a lead frame or the like made of a copper alloy, interdiffusion of Sn and Cu contained in a solder layer occurs due to heat history after mounting a semiconductor element, and an alloy layer is formed. In this alloy layer, voids may be generated due to the difference in diffusion rate between Sn and Cu, and peeling may occur at the interface starting from the voids. This resistance to delamination is called "solder weather resistance".

In recent years, automobiles have become increasingly electrified, and many semiconductor devices for in-vehicle use have come to be used. In automotive applications, the temperature of the operating environment can be high depending on where it is used.・There is a demand for parts for electronic devices.

However, in Cu—Fe—P alloys, as disclosed in the above-mentioned Patent Documents 1 to 3, proposals have been made to precipitate fine precipitate particles in order to improve heat resistance. , the weather resistance of the solder was not sufficiently considered. That is, in Patent Documents 1 to 3 described above, although the heat resistance is improved, the weather resistance of the solder is insufficient. Although it has been suggested that the addition of Zn improves the weather resistance of the solder, it was not possible to obtain sufficient weather resistance of the solder applicable to recent usage environments by adding Zn alone.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a Cu--Fe--P based copper alloy having excellent heat resistance and excellent solder weather resistance.

In order to solve this problem, the copper alloy of the present invention has Fe; 1.5% by mass or more and 2.7% by mass or less, P; % by mass or more and 0.5% by mass or less, one or both of Mg and Sn in total of 0.01% by mass or more and 0.5% by mass or less, and the balance being Cu and unavoidable impurities, and the unavoidable The content of C contained as impurities is less than 5 ppm by mass, the content of Cr is less than 7 ppm by mass, the content of Mo is less than 5 ppm by mass, the content of W is less than 1 ppm by mass, and the content of V is 1 The number ratio of precipitate particles with a particle size of 50 nm or more and less than 100 nm, which is less than mass ppm, the Nb content is less than 1 mass ppm, and the observed precipitate particles have a particle size of 5 nm or more and less than 100 nm. exceeds 5.0%, the number ratio of precipitate particles with a particle size of 5 nm or more and less than 15 nm exceeds 50%, and the number density of precipitate particles with a particle size of 50 nm or more and less than 100 nm is 2.0. /μm ² or more, the number density of precipitate particles with a particle diameter of 5 nm or more and less than 15 nm is 15 pieces/μm ² or more , and the electrical conductivity is 55% IACS or more .
The particle size of the precipitate particles in the present invention is the diameter of a circle having an area equal to the area of the precipitate particles (equivalent circle diameter) in observation of the structure.

According to the copper alloy having the above configuration, Fe; 1.5% by mass or more and 2.7% by mass or less, P; 5% by mass or less, one or both of Mg and Sn are contained in a total of 0.01% by mass or more and 0.5% by mass or less, and the balance is Cu and inevitable impurities. It can have excellent thermal conductivity as well as excellent thermal conductivity.
Further, in the copper alloy of the present invention, the content of C contained as the inevitable impurities is less than 5 ppm by mass, the content of Cr is less than 7 ppm by mass, the content of Mo is less than 5 ppm by mass, and the content of W is less than 1 ppm by mass, the content of V is less than 1 ppm by mass, and the content of Nb is less than 1 ppm by mass. Therefore, the generation of coarse Fe-based crystallized substances in the ingot can be suppressed, and the number of surface defects generated can be reduced.

Then, the precipitate particles having a particle size of 50 nm or more and less than 100 nm can suppress the flow of vacancies diffusing facing Cu in the alloy layer formed between the solder layer and the copper alloy, It is possible to suppress the generation of voids due to aggregation of the pores. In the alloy of the present invention, the number ratio to the total number of precipitate particles having an observed particle size of 5 nm or more and less than 100 nm exceeds 5.0%, and the number density is 2.0 particles/μm ² or more. Therefore, it becomes possible to improve the weather resistance of the solder.
In addition, the precipitate particles with a particle size of 5 nm or more and less than 15 nm have a number ratio of more than 50% to the total number of precipitate particles with a particle size of 5 nm or more and less than 100 nm, and a number density of 15 particles/μm ² or more. Therefore, it is possible to suppress the movement of mobile dislocations, delay recovery and recrystallization, and exert a pinning effect on grain boundaries, so that heat resistance can be sufficiently improved.
Therefore, according to the copper alloy of the present invention, it is possible to achieve both solder weather resistance and heat resistance.
Moreover, since the copper alloy of the present invention has a conductivity of 55% IACS or more, it can be applied to applications requiring high conductivity.

Here, the copper alloy of the present invention may contain Co; 0.005% by mass or more and 0.5% by mass or less.
In this case, Co dissolves in the mother phase and partly dissolves in the Fe-based and Fe—P-based precipitates, so that solid-solution strengthening and precipitation strengthening result in heat resistance and heat resistance while maintaining solder weather resistance. Strength can be improved.

Further, in the copper alloy of the present invention, Ni: 0.005 mass% to 0.5 mass%, Al: 0.005 mass% to 0.5 mass%, Si: 0.005 mass% or more Any one or more of 0.5% by mass or less may be contained.
In this case, the heat resistance can be further improved by containing Ni, Al, and Si.

Moreover, the copper alloy of the present invention preferably has a tensile strength of 400 MPa or more.
In this case, since the tensile strength is set to 400 MPa or more, it can be applied to applications requiring high strength.

Furthermore, the copper alloy of the present invention preferably has a Vickers hardness of 120 Hv or more.
In this case, since the Vickers hardness is set to 120 Hv or more, it is not easily deformed, and is particularly suitable as a component for electric/electronic equipment.

According to the present invention, it is possible to provide a Cu--Fe--P based copper alloy which is excellent in heat resistance and solder weather resistance.

1 is a flowchart of a method for producing a copper alloy according to this embodiment; FIG. 4 is a structure observation photograph of a copper alloy of Inventive Example 4 in Examples. (a) is an SEM photograph, and (b) is a binarization processing diagram.

A copper alloy that is one embodiment of the present invention will be described below. The copper alloy of this embodiment is used as a material for parts for electrical and electronic equipment such as lead frames and connectors.

The copper alloy of the present embodiment has Fe; 1.5 mass% or more and 2.7 mass% or less, P; 0.008 mass% or more and 0.20 mass% or less, Zn; 0.01 mass% or more and 0.5 The composition contains 0.01% by mass or more and 0.5% by mass or less of one or both of Mg and Sn in total, and the balance is Cu and unavoidable impurities.

Here, the copper alloy of the present embodiment may further contain Co; 0.005% by mass or more and 0.5% by mass or less.
Further, in the copper alloy of the present embodiment, Ni; 0.005 mass% or more and 0.5 mass% or less, Al; Any one or more of 0.5% by mass or less may be contained.

Furthermore, in the copper alloy of the present embodiment, the content of C contained as inevitable impurities is less than 5 ppm by mass, the content of Cr is less than 7 ppm by mass, the content of Mo is less than 5 ppm by mass, and the content of W may be less than 1 ppm by mass, the content of V may be less than 1 ppm by mass, and the content of Nb may be less than 1 ppm by mass.

In the copper alloy of the present embodiment, precipitate particles such as Fe and Fe—P are dispersed in the matrix. The parent phase is a phase other than precipitate particles such as Fe and Fe—P, and is mainly composed of Cu (the Cu content exceeds 97% by mass), and some Fe, Zn, It is a phase in which P, Sn, etc. are dissolved.

In the copper alloy of the present embodiment, the number ratio of precipitate particles having a particle size of 50 nm or more and less than 100 nm is 5.0% for the observed precipitate particles having a particle size of 5 nm or more and less than 100 nm. In addition, the number ratio of precipitate particles having a particle size of 5 nm or more and less than 15 nm exceeds 50%.
In addition, the number density of the precipitate particles having a particle size of 50 nm or more and less than 100 nm is 2.0 pieces/μm ² or more, and the number density of the precipitate particles having a particle size of 5 nm or more and less than 15 nm is 15 pieces/μm ² or more. It is

The particle size of the precipitate particles was defined as the diameter of a circle having an area equal to the area of the precipitate particles (equivalent circle diameter) in the observation of the structure.
When calculating the number ratio of precipitate particles, precipitate particles having a particle size of less than 5 nm are difficult to observe, and have a substantial effect on improving solder weather resistance and heat resistance. Therefore, it was excluded from the evaluation of precipitate particles. In addition, precipitate particles with a particle size of 100 nm or more have substantially no effect on the improvement of solder weather resistance and heat resistance, and can cause surface defects. was excluded from the scope of

Moreover, in the copper alloy of the present embodiment, it is preferable that the electrical conductivity is set to 55%IACS or more.
Furthermore, it is preferable that the copper alloy of the present embodiment has a tensile strength of 400 MPa or more.
Moreover, it is preferable that the copper alloy of the present embodiment has a Vickers hardness of 120 Hv or more.

Here, the reason why the component composition, the distribution of precipitate particles, and various properties are defined as described above will be explained below.

(Fe)
Fe forms a solid solution in the matrix phase and forms precipitate particles of Fe or Fe—P. By dispersing the Fe or Fe—P precipitate particles in the matrix phase, the strength, hardness and heat resistance are improved without lowering the electrical conductivity.
Here, if the Fe content is less than 1.5% by mass, the effect of improving the strength, etc. is not sufficient. On the other hand, if the Fe content exceeds 2.7% by mass, large crystallized substances may be formed, impairing the cleanness of the surface. Furthermore, there is a risk of causing a decrease in electrical conductivity and workability.
Therefore, in this embodiment, the Fe content is set to 1.5% by mass or more and 2.7% by mass or less.
In order to ensure the above effects, the lower limit of the Fe content is preferably 1.8% by mass or more, more preferably 2.1% by mass or more. In order to reliably suppress the formation of large crystallized substances, the upper limit of the Fe content is preferably 2.6% by mass or less, more preferably 2.4% by mass or less.

(P)
P is an element having a deoxidizing action. In addition, as described above, Fe—P precipitate particles are formed together with Fe, and the strength, hardness, and heat resistance are improved without lowering the electrical conductivity.
Here, if the P content is less than 0.008% by mass, the effect of improving the strength, etc. is not sufficient. On the other hand, when the P content exceeds 0.20% by mass, the electrical conductivity and workability are lowered.
Therefore, in this embodiment, the P content is set to 0.008% by mass or more and 0.20% by mass or less.
In order to ensure the above effects, the lower limit of the P content is preferably 0.01% by mass or more, and more preferably 0.02% by mass or more. Also, in order to reliably suppress deterioration in electrical conductivity and workability, the upper limit of the P content is preferably 0.15% by mass or less, more preferably 0.12% by mass or less.

(Zn)
Zn is an element that acts to improve solder wettability and solder weather resistance.
Here, if the Zn content is less than 0.01% by mass, the effect of improving solder wettability and solder weather resistance cannot be sufficiently achieved. On the other hand, even if the Zn content exceeds 0.5% by mass, the effect is saturated.
Therefore, in this embodiment, the Zn content is set to 0.01% by mass or more and 0.5% by mass or less.
In order to ensure the above effects, the lower limit of the Zn content is preferably 0.03% by mass or more, more preferably 0.05% by mass or more. Also, the upper limit of the Zn content is preferably 0.35% by mass or less, more preferably 0.20% by mass or less.

(Mg, Sn)
Mg and Sn are elements that improve heat resistance and strength while maintaining solder weather resistance by forming a solid solution in the matrix.
Here, if the total content of one or both of Mg and Sn is less than 0.01% by mass, the above effects cannot be sufficiently exhibited. On the other hand, if the total content of one or both of Mg and Sn exceeds 0.5% by mass, the electrical conductivity will significantly decrease.
Therefore, in this embodiment, the total content of one or both of Mg and Sn is set to 0.01% by mass or more and 0.5% by mass or less.
In order to ensure the above effects, the lower limit of the total content of one or both of Mg and Sn is preferably 0.02% by mass or more, and 0.03% by mass or more. more preferably. Further, in order to further suppress the decrease in conductivity, the upper limit of the total content of one or both of Mg and Sn is preferably 0.3% by mass or less, and is 0.2% by mass or less. is more preferred. More preferably, it is 0.1 mass or less.

(Co)
Co dissolves in the matrix phase to strengthen the solid solution, and partly dissolves in the Fe-based precipitates or Fe—P-based precipitates to act as precipitation strengthening, thereby maintaining the weather resistance of the solder. It has the effect of improving heat resistance and strength. Also, part of it may be added as appropriate depending on the required characteristics.
Here, if the Co content is less than 0.005% by mass, the above effects cannot be sufficiently achieved. If the Co content exceeds 0.5% by mass, the electrical conductivity is significantly lowered.
Therefore, in this embodiment, when Co is added, it is set to 0.005% by mass or more and 0.5% by mass or less.
When Co is added, the lower limit is preferably 0.01% by mass or more, more preferably 0.02% by mass or more. Furthermore, it is preferable to set the upper limit of the Co content to 0.2% by mass or less.

(Ni, Al, Si)
Ni, Al, and Si have the effect of further improving the heat resistance. Therefore, it may be added as appropriate depending on the required properties.
Here, when the Ni content is less than 0.005% by mass, the Al content is less than 0.005% by mass, or the Si content is less than 0.005% by mass, the above effects are sufficiently obtained. can't make it work. On the other hand, when the Ni content exceeds 0.5% by mass, the Al content exceeds 0.5% by mass, or the Si content exceeds 0.5% by mass, the conductivity is significantly reduced. will decline.
Therefore, in the present embodiment, when Ni, Al, and Si are added, the Ni content is 0.005% by mass or more and 0.5% by mass or less, and the Al content is 0.005% by mass or more and 0.5% by mass or less. .5 mass % or less, and the Si content is set to 0.005 mass % or more and 0.5 mass % or less.
When adding Ni, Al, and Si, the lower limit of the Ni content is preferably 0.01% by mass or more, and the lower limit of the Al content is preferably 0.01% by mass or more. Preferably, the lower limit of the Si content is set at 0.01% by mass or more. Furthermore, the upper limit of the Ni content is preferably 0.1% by mass or less, the upper limit of the Al content is preferably 0.1% by mass or less, and the upper limit of the Si content is 0.1% by mass. % or less is preferable.

(Inevitable impurities C, Cr, Mo, W, V, Nb)
C, Cr, Mo, W, V, and Nb are contained in the above copper alloy as unavoidable impurities. Here, when the contents of C, Cr, Mo, W, V, and Nb are large, the surface defects of the copper alloy described above are greatly increased. These surface defects are caused by iron alloy particles containing at least one of Cr, Mo, W, V, and Nb, and Fe and C.

Generally, when the above copper alloy is melted and cast, the Fe element exists in a dissolved state in a liquid phase containing Cu as a main component. However, when C, Cr, Mo, W, V, and Nb are present in a certain amount or more, the molten copper alloy has a liquid phase containing Cu as the main component and a liquid phase containing Fe as the main component, and C and Cr, Mo, W, and V , and a liquid phase containing at least one of Nb, resulting in coarse crystallized substances containing at least one of Cr, Mo, W, V, and Nb and Fe and C. will be present in the ingot. It is considered that the iron alloy particles are then exposed on the surface of the copper alloy by rolling the ingot, and the surface defects described above are generated. In addition, due to the iron alloy particles, shape defects occur when press working, etching or silver plating is performed.

Therefore, by reducing C, Cr, Mo, W, V, and Nb, it is possible to suppress surface defects and product shape defects caused by iron alloy particles. In particular, in the present embodiment, the number of precipitate particles having a particle size of 50 nm or more and less than 100 nm is ensured, and coarse precipitate particles may occur and surface defects may occur. , W, V, and Nb to suppress the occurrence of coarse crystallized substances, thereby suppressing the number of surface defects.

Therefore, in the present embodiment, in order to suppress the generation of coarse crystallized substances, the content of C, which is an inevitable impurity, is less than 5 ppm by mass, the content of Cr is less than 7 mass ppm, and the content of Mo is The content of W may be limited to less than 5 ppm by mass, the content of W to less than 1 ppm by mass, the content of V to less than 1 ppm by mass, and the content of Nb to less than 1 ppm by mass.
In order to further suppress the generation of coarse crystallized substances, the content of C, which is an unavoidable impurity, is preferably less than 4 ppm by mass. More preferably 3 mass ppm or less, more preferably 2 mass ppm or less. The Mo content is desirably less than 1 ppm by mass, more preferably less than 0.6 ppm by mass. In addition, the Cr content is less than 5 mass ppm, the W content is less than 0.6 mass ppm, the V content is less than 0.6 mass ppm, and the Nb content is less than 0.6 mass ppm. is preferred.

In addition, the above elements and inevitable impurities other than C, Cr, Mo, W, V, and Nb include Ca, Sr, Ba, rare earth elements, Zr, Be, Ti, H, Li, B, N, O, F , Na, S, Cl, K, Mn, Ga, Ge, As, Se, Br, Rb, Tc, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, I, Cs, Hf, Ta, Re , Os, Ir, Pt, Au, Hg, Tl, Pb, Bi and the like.

(Precipitate particles having a particle size of 50 nm or more and less than 100 nm)
For example, when used in a high-temperature environment such as 175°C for a long time, Cu diffusion in the solder layer is faster than in the copper alloy, so the Kirkendall effect causes fine particles with a grain size of less than 15 nm to form at the interface between the copper alloy and the solder layer. fine precipitate particles agglomerate. These fine precipitate particles impede the flow of vacancies diffusing counter to Cu diffusing from the copper alloy toward the solder layer, resulting in a retardation of vacancy diffusion. As a result, vacancies agglomerate in the vicinity of the interface over time, causing large voids and detachment, thereby deteriorating the weather resistance of the solder.

Here, precipitate particles with a particle size of 50 nm or more and less than 100 nm do not impede the flow of pores. In addition, the number of fine precipitate particles can be reduced by absorbing surrounding fine precipitate particles having a particle size of less than 15 nm due to Ostwald growth during the precipitation heat treatment. As a result, it is possible to suppress the generation of voids due to aggregation of pores, and to improve the weather resistance of the solder.
Based on the above, in the present embodiment, the number ratio of precipitate particles having a particle size of 50 nm or more and less than 100 nm is set to more than 5.0%, and the number density is set to 2.0 pieces/μm ² or more.
In order to achieve the above effects, the number ratio of precipitate particles having a particle size of 50 nm or more and less than 100 nm is preferably 7.5% or more, more preferably 10.0% or more. . In addition, the number density of precipitate particles having a particle size of 50 nm or more and less than 100 nm is preferably 2.5/μm ² or more, more preferably 3.0/μm ^{2 or} more.

(Precipitate particles having a particle size of 5 nm or more and less than 15 nm)
Precipitate particles with a particle size of 5 nm or more and less than 15 nm hinder mobile dislocations, have the effect of delaying recovery and recrystallization, and have the effect of pinning grain boundaries, greatly improving heat resistance. .
Based on the above, in the present embodiment, the number ratio of precipitate particles having a particle size of 5 nm or more and less than 15 nm is set to more than 50%, and the number density is set to 15 pieces/μm ² or more.
In order to achieve the above effects, the number ratio of precipitate particles having a particle size of 5 nm or more and less than 15 nm is preferably 55% or more, more preferably 60% or more. In addition, the number density of precipitate particles having a particle size of 5 nm or more and less than 15 nm is preferably 20 particles/μm ² or more, more preferably 25 particles/μm ^{2 or} more.

(conductivity)
In the copper alloy of this embodiment, when the electrical conductivity is 55% IACS or more, it is particularly suitable as a material for parts for electrical and electronic equipment such as lead frames and connectors.
The electrical conductivity of the copper alloy of the present embodiment is preferably 57%IACS or higher, more preferably 60%IACS or higher.

(tensile strength)
When the copper alloy of the present embodiment has a tensile strength of 400 MPa or more, it is excellent in strength and is particularly suitable as a material for parts for electrical and electronic equipment such as lead frames and connectors. In addition, in this embodiment, the tensile strength when a tensile test is performed in a direction parallel to the rolling direction is set to 400 MPa or more.
The tensile strength of the copper alloy of this embodiment is preferably 420 MPa or more, more preferably 450 MPa or more.

(Vickers hardness)
When the copper alloy of the present embodiment has a Vickers hardness of 120 Hv or more, it is not easily deformed and is particularly suitable as a material for parts for electrical and electronic equipment such as lead frames and connectors.
The Vickers hardness of the copper alloy of this embodiment is preferably 130 Hv or higher, more preferably 140 Hv or higher.

Next, an example of the method for producing a copper alloy according to the present embodiment having such a configuration will be described with reference to the flowchart shown in FIG.

(Melting/casting step S01)
First, the above elements are added to the molten copper obtained by melting the copper raw material to adjust the composition, thereby producing the molten copper alloy. For addition of various elements, simple elements, master alloys, or the like can be used. Also, a raw material containing the above elements may be melted together with the copper raw material. Recycled materials and scrap materials of the present alloy may also be used. Here, the molten copper is preferably so-called 4NCu with a purity of 99.99% by mass or more, or so-called 5NCu with a purity of 99.999% by mass or more.
Then, an ingot is produced by injecting the molten copper alloy with the adjusted composition into the mold. In addition, when considering mass production, it is preferable to use a continuous casting method or a semi-continuous casting method.

(Homogenization step S02)
Next, heat treatment is performed to homogenize the obtained ingot. It is preferable to hold the ingot at 850° C. or higher and 1050° C. or lower for 1 hour or more.
Although there is no upper limit for the holding time in the homogenization step S02, it is preferably 24 hours or less in consideration of cost and production efficiency.
Moreover, the cooling rate in the homogenization step S02 is not particularly limited, and air cooling or water cooling may be performed.

(Hot working step S03)
Next, hot working is performed as necessary. Further, the hot working step S03 may also serve as the homogenizing step S02. In this hot working step S03, the steel is sufficiently solutionized in order to control the grain size of precipitates in the subsequent steps.
After holding at 850° C. or higher and 1050° C. or lower for 1 hour or more, hot working is performed at 550° C. or higher and 1050° C. or lower.
Then, the electrical conductivity after the hot working step S03 is set to 40%IACS or less, preferably 35%IACS or less, more preferably 30%IACS or less.
In order to obtain such conductivity, the hot working end temperature is set to 600° C. or higher, and then air cooling or water cooling is selected.
In addition, in this hot working step S03, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be employed. In addition, in this embodiment, rolling processing shall be performed.

(Rough processing step S04)
After the hot working step S03, cold rough working is performed as necessary. The processing rate at this time is preferably in the range of 10% or more and 95% or less.
In this rough processing step S04, the processing method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be employed. In addition, in this embodiment, rolling processing shall be performed.

(Solution heat treatment step S05)
A solution heat treatment step S05 is performed after the rough processing step S04. This solution heat treatment step S05 is an important step for controlling the grain size of subsequent precipitates. Here, the heat treatment temperature is 800° C. or more and less than 1000° C., and the holding time at the heat treatment temperature is 1 minute or more and less than 24 hours. The heat treatment temperature is preferably 850°C or higher and lower than 1000°C, more preferably 900°C or higher and lower than 1000°C.
After the heat treatment, water cooling may be performed to maintain the solution state. Alternatively, it may be cooled to 500° C. or lower at a cooling rate of 400° C./min. In order to confirm that the solution treatment has been performed reliably, the conductivity of the solution heat treatment S05 should be 35%IACS or less, preferably 30%IACS or less, and more preferably 25%IACS or less.

(First cold working step S06)
Cold working is implemented after the solution heat treatment step S05. It is preferable that the processing rate at this time is within the range of 10% or more and 95% or less.
In addition, in this first cold working step S06, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, in this embodiment, rolling processing shall be performed.

(First precipitation heat treatment step S07)
Next, heat treatment is performed at 550° C. or more and less than 800° C. for 1 second or more and less than 1 hour. This first precipitation heat treatment step S07 improves the number density of precipitate particles having a particle size of 50 nm or more.
Then, the electrical conductivity after the first precipitation heat treatment step S07 is within the range of 20%IACS or more and 40%IACS or less, preferably 25%IACS or more and 40%IACS or less, more preferably 25%IACS or more and 37%IACS or less. , more preferably 25% IACS or more and 35% IACS or less.
In order to obtain such electrical conductivity, it is preferable to appropriately set the rate of temperature increase and the rate of temperature decrease in the first precipitation heat treatment step S07.

(Second cold working step S08)
Cold working is performed after the first precipitation heat treatment step S07. It is preferable that the processing rate at this time is within the range of 10% or more and 95% or less.
In addition, in the second cold working step S08, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, in this embodiment, rolling processing shall be performed.

(Second precipitation heat treatment step S09)
Next, heat treatment is performed at 550° C. or more and less than 900° C. for 1 hour or more and less than 24 hours. This second precipitation heat treatment step S09 further improves the number density of precipitate particles having a particle size of 50 nm or more.
Then, the electrical conductivity after the second precipitation heat treatment step S09 is within the range of 20%IACS or more and 40%IACS or less, preferably 25%IACS or more and 40%IACS or less, more preferably 25%IACS or more and 37%IACS or less. , more preferably 25% IACS or more and 35% IACS or less.
In order to achieve such electrical conductivity, it is preferable to appropriately set the rate of temperature increase and the rate of temperature decrease in the second precipitation heat treatment step S09.

(Third cold working step S10)
After the second precipitation heat treatment step S09, the third cold working step S10 is performed. The processing rate at this time is preferably in the range of 10% or more and 95% or less.
In addition, in the third cold working step S10, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, in this embodiment, rolling processing shall be performed.

(Third precipitation heat treatment step S11)
Next, a heat treatment is performed at a temperature of 450° C. or higher and 600° C. or lower for more than 1 hour and 24 hours or less. It is preferable to shorten the holding time when heat-treating at a high temperature, and lengthen the holding time when heat-treating at a low temperature. This third precipitation heat treatment step S11 increases the number of precipitate particles having a particle size of 5 nm or more and less than 15 nm.
Then, it is preferable to set the conditions of the third precipitation heat treatment step S11 so that the electrical conductivity of the final product is 55% IACS or more in consideration of the conditions of the subsequent steps.
The temperature increase rate and temperature decrease rate in the third precipitation heat treatment step S11 may be appropriately set, but it is preferable that the temperature increase rate is 1°C/min or more and the temperature decrease rate is 0.1°C/min or more up to 300°C.

(Fourth cold working step S12)
Cold working is performed after the third precipitation heat treatment step S11. It is preferable that the processing rate at this time is within the range of 1% or more and 95% or less.
In addition, in the fourth cold working step S12, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, in this embodiment, rolling processing shall be performed.

(Fourth precipitation heat treatment step S13)
Next, heat treatment is performed at 450° C. or higher and 800° C. or lower for 1 second or longer and 24 hours or shorter. It is preferable to shorten the holding time when heat-treating at a high temperature, and lengthen the holding time when heat-treating at a low temperature. In the fourth precipitation heat treatment step S13, the number ratio and density of precipitate particles having a diameter of 50 nm or more are increased by Ostwald growth, and the number ratio and density of fine precipitate particles are decreased.
For this reason, it is preferable to set the conditions of the fourth precipitation heat treatment step S13 so that the electrical conductivity of the final product is 55% IACS or more in consideration of the conditions of subsequent steps. More preferably 60% IACS or more, still more preferably 62% IACS or more.

(Finishing process S14)
Finishing is performed after the fourth precipitation heat treatment step S13. It is preferable that the processing rate at this time is within the range of 10% or more and 95% or less.
In the finishing step S14, the working method is not particularly limited, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be adopted. In addition, in this embodiment, rolling processing shall be performed.

(Strain removal heat treatment step S15)
Next, if necessary, strain removal heat treatment is performed at 200° C. or more and less than 700° C. for 1 second or more and less than 24 hours for the purpose of removing the residual strain generated in the finishing step S14. It is preferable to shorten the holding time when heat-treating at a high temperature, and lengthen the holding time when heat-treating at a low temperature.

The copper alloy of the present embodiment is produced through the steps described above. In the present embodiment, since rolling is performed as the processing method in the finishing step S14, a copper alloy strip having a predetermined thickness is manufactured.

According to the copper alloy of the present embodiment configured as described above, Fe; 1.5% by mass or more and 2.7% by mass or less, P; a composition containing 0.01% by mass or more and 0.5% by mass or less, a total of 0.01% by mass or more and 0.5% by mass or less of one or both of Mg and Sn, and the balance being Cu and unavoidable impurities Therefore, it is possible to have excellent strength and electrical conductivity as well as good thermal conductivity.

Then, the precipitate particles with a particle size of 50 nm or more and less than 100 nm have a number ratio of more than 5.0% with respect to the observed precipitate particles with a particle size of 5 nm or more and less than 100 nm, and the number density is 2.0 / Since the thickness is set to 2 μm ² or more, the flow of vacancies diffusing at the interface between the solder layer and the copper alloy is not hindered, and the formation of voids due to aggregation of the vacancies can be suppressed. Therefore, it becomes possible to improve solder weather resistance.

In addition, the precipitate particles with a particle size of 5 nm or more and less than 15 nm have a number ratio of more than 50% with respect to the observed precipitate particles with a particle size of 5 nm or more and less than 100 nm, and the number density is 15 particles / μm ² or more. As a result, recovery and recrystallization can be delayed, and a grain boundary pinning effect can be obtained, so that heat resistance can be sufficiently improved.

Further, in the copper alloy of the present embodiment, when Co is further contained in the range of 0.005% by mass or more and 0.5% by mass or less, Co dissolves in the matrix phase, and Co Part of it dissolves in the Fe-based and Fe—P-based precipitates, so that solid-solution strengthening and precipitation strengthening can improve heat resistance and strength while maintaining solder weather resistance.

Further, in the copper alloy of the present embodiment, Ni; When any one or two or more of above 0.5% by mass or less are contained, it is possible to further improve the heat resistance.

Furthermore, in the copper alloy of the present embodiment, the content of C contained as inevitable impurities is less than 5 ppm by mass, the content of Cr is less than 7 ppm by mass, the content of Mo is less than 5 ppm by mass, and the content of W is is less than 1 ppm by mass, the content of V is less than 1 ppm by mass, and the content of Nb is less than 1 ppm by mass, the elements that promote liquid phase separation in the melting/casting step S01 are reduced. It is possible to suppress the formation of coarse Fe-based crystallized substances in the ingot and reduce the number of surface defects that occur.

Moreover, in the copper alloy of the present embodiment, when the electrical conductivity is 55% IACS or more, it can be applied to applications requiring high electrical conductivity.
Furthermore, when the copper alloy of the present embodiment has a tensile strength of 400 MPa or more, it can be applied to applications requiring high strength.
In addition, when the copper alloy of the present embodiment has a Vickers hardness of 120 Hv or more, it is not easily deformed and is particularly suitable as a component for electrical and electronic equipment.

Although the copper alloy that is the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately modified without departing from the technical idea of the invention.
In the above-described embodiment, an example of a method for producing a copper alloy has been described, but the method for producing a copper alloy is not limited to the one described in the embodiment, and can be produced by appropriately selecting an existing production method. may

For example, in the present embodiment, rolling is performed as a processing method to obtain a copper alloy sheet material made of the copper alloy of the present invention. can obtain a copper alloy wire rod made of the copper alloy of the present invention, and when forging, pressing, etc. are performed as a processing method, copper alloy members of various shapes made of the copper alloy of the present invention can be obtained. be able to.

The results of confirmatory experiments conducted to confirm the effects of the present invention will be described below.

First, in the melting and casting process, a copper raw material made of oxygen-free copper (ASTM B152 C10100) with a purity of 99.99% by mass or more is prepared, charged into an alumina crucible, and subjected to a high frequency in an Ar gas atmosphere. Melted in a melting furnace. Fe, P, Zn, Mg, Al, Si, Co and Ni were added to the obtained molten copper. These elements were added using a Cu master alloy.
As a result, molten copper alloys having the chemical compositions shown in Tables 1 and 2 were melted and poured into carbon molds to produce ingots. The size of the ingot was about 25 mm thick×about 70 mm wide×about 100 mm long.

Next, as a hot rolling step, the obtained ingot is heat treated for 4 hours at the hot rolling start temperature shown in Tables 3 and 4, and then hot worked until the thickness becomes 12 mm. bottom. In addition, reheating was appropriately performed as necessary so that the hot rolling end temperature was 800° C. or higher. After completion of hot rolling, water cooling was performed.
Chamfering was performed to remove the oxide film formed on the surface after hot rolling, and the electrical conductivity after hot rolling was measured by an eddy current method. Tables 3 and 4 show the measured conductivities.
Next, as a rough rolling step, the obtained hot rolled material was cold rolled to a thickness of 8 mm.

Thereafter, heat treatment was performed at 950° C. for 2 hours as a solution treatment, and water cooling was performed after the heat treatment. After the solution treatment, the surface was polished, and the electrical conductivity was measured by the eddy current method. The obtained conductivity is shown in Tables 3 and 4.
Next, as the first cold rolling step, cold rolling was performed until the thickness became 4 mm.

After that, as the first precipitation heat treatment step, an electric furnace was used to hold the heat treatment temperature shown in Tables 3 and 4 for a predetermined time between 1 hour and 4 hours, followed by air cooling, furnace cooling, or water cooling.
Polishing was performed to remove the surface oxide film formed after the heat treatment. After that, the electrical conductivity after the first precipitation heat treatment step was measured by an eddy current method. Tables 3 and 4 show the measured conductivities.

Next, as a second cold rolling step, cold rolling was performed until the thickness became 2 mm.

Next, as a second precipitation heat treatment step, an electric furnace was used to maintain the heat treatment temperatures shown in Tables 3 and 4 for a predetermined time between 1 hour and 4 hours, followed by air cooling, furnace cooling, or water cooling.
Polishing was performed to remove the oxide film formed on the surface after the heat treatment, and the electrical conductivity after the second precipitation heat treatment step was measured by an eddy current method. Tables 3 and 4 show the measured conductivities.

Next, as a third cold rolling step, cold rolling was carried out until the thickness became within the range of 0.4 mm or more and 0.8 mm or less.
Next, as a third precipitation heat treatment step, an electric furnace was used and the heat treatment temperatures shown in Tables 3 and 4 were maintained for a predetermined time between 1 hour and 24 hours. After the heat treatment, it was air-cooled or water-cooled.
After that, the electrical conductivity after the third precipitation heat treatment step was measured by the four-probe method. Tables 3 and 4 show the measured conductivities.

Next, as a fourth cold rolling step, cold rolling was performed until the thickness reached 0.3 mm.
Next, as a fourth precipitation heat treatment step, heat treatment was performed for a predetermined time of less than 1 minute at the temperatures shown in Tables 3 and 4 using a salt bath furnace. The electrical conductivity after the fourth precipitation heat treatment step was measured by the four-probe method. Tables 3 and 4 show the measured conductivities.

Next, as a finish rolling step, cold rolling was performed until the thickness became 0.15 mm, and a sample for evaluation measurement was obtained.

After that, as shown in the table, some samples were subjected to strain removal heat treatment for 1 minute at the temperatures shown in Tables 3 and 4 using a salt bath furnace, and after the surface was polished, samples for evaluation measurement and

The obtained samples were evaluated as described below.

(Observation of precipitate particles)
Observation of precipitate particles was carried out by the following method. The surface perpendicular to the rolling direction of the sample for evaluation measurement, that is, the RD surface is mechanically polished and mirror-finished, and then using IM-4000 manufactured by Hitachi High Technologies, the surface is accelerated at 4.0 kV by Ar ions. After ion milling with voltage, a field emission scanning electron microscope (SU8220, manufactured by Hitachi High-Technologies Corporation) was used.
For the precipitate particle size of 20 nm or more and less than 100 nm, the observation magnification is 30,000 times the field of view (about 13 μm ² ), and for the precipitate particle size of 5 nm or more and less than 20 nm, the observation magnification is the field of view of 100,000 times (about 1 μm ² ). From the observed SEM photograph, image processing was performed to add contrast only to the precipitates.
From the contrasted image, the equivalent circle diameter was calculated from the area of the precipitate using the image analysis software "Win ROOF". When determining the precipitate distribution, for precipitate particle sizes of 20 nm or more and less than 100 nm, a field of view of 30,000 times (about 13 μm ² ) is used for 3 or more fields of view, and for precipitate particle sizes of 5 nm or less and less than 20 nm, observation magnification is increased. Three or more fields of view (approximately 1 μm ² ) were used at a magnification of 100,000 times. FIG. 2 shows an SEM photograph of Inventive Example 4 observed at a magnification of 100,000 (FIG. 2(a)) and an image (FIG. 2(b)) in which only the precipitates are contrasted using the photograph. .

(tensile strength)
A No. 13B test piece was taken from the sample according to JIS Z 2241, and the tensile strength was measured. The test piece was taken so that the tensile direction was parallel to the rolling direction. Tables 5 and 6 show the evaluation results.

(conductivity)
A test piece having a width of 10 mm and a length of 100 mm was taken from the sample for evaluation measurement, and the electric resistance was determined by the four-probe method. Also, the dimensions of the test piece were measured using a micrometer, and the volume of the test piece was calculated. Then, the electrical conductivity was measured from the measured electrical resistivity and the calculated volume. The test piece was taken so that its longitudinal direction was parallel to the rolling direction. Tables 5 and 6 show the measurement results.

(Vickers hardness)
The Vickers hardness was measured with a test load of 0.98 N according to the micro Vickers hardness test method specified in JIS Z 2244. Tables 5 and 6 show the evaluation results.

(Heat-resistant)
The Vickers hardness of the sample before the heat resistance test is Hv _RT , and the hardness measured at room temperature after being heat-treated at 450° C. for 1 minute as a heat resistance test and then rapidly cooled is Hv 450 _{° C.} , Hv _450° C./Hv. A sample with _{an RT} of 90% or more was marked with “◯”, and a sample with RT of less than 90% was marked with “×”. Tables 5 and 6 show the evaluation results.

(solder weather resistance)
Five strip-shaped (width 10 mm, length 50 mm) test pieces taken from the sample were prepared and immersed in a Sn-40 mass% Pb solder bath heated to 200 ° C. for 5 seconds, so that solder was applied to the surface of the test piece. formed a layer. Then, after heat treatment was performed at 175° C. for 500 hours, the test piece was bent by 180°, and it was confirmed whether or not the solder peeled off from the bent portion. "A" indicates that no peeling was observed in any of the 5 pieces, "B" indicates that 1 to 2 peels occurred, and "C" indicates that 3 or more peels occurred. Tables 5 and 6 show the evaluation results.

In Comparative Example 1 in which the number ratio of precipitate particles with a particle size of 50 nm or more and less than 100 nm was 0.7% and the number density was 0.9/μm ² , the weather resistance of the solder was judged to be "C". . It is presumed that the number of precipitate particles with a particle size of 50 nm or more and less than 100 nm was small, and the generation of voids could not be suppressed.
In Comparative Example 2, in which the number ratio of precipitate particles having a particle size of 5 nm or more and less than 15 nm was 42% and the number density was 11.0/μm ² , the heat resistance was insufficient. The solder weather resistance was not evaluated.
In Comparative Example 3 in which the Sn content was 0.61% by mass, the electrical conductivity was as low as 51%IACS. Therefore, heat resistance and solder weather resistance were not evaluated.

On the other hand, it was confirmed that the inventive examples are excellent in heat resistance and solder weather resistance. It was also excellent in tensile strength, electrical conductivity and Vickers hardness.
From the above, it was confirmed that according to the present invention, a Cu--Fe--P-based copper alloy having excellent heat resistance and excellent solder weather resistance can be provided.

Claims (5)

Fe; 1.5 mass% or more and 2.7 mass% or less, P; 0.008 mass% or more and 0.20 mass% or less, Zn; 0.01 mass% or more and 0.5 mass% or less, among Mg and Sn Contains one or both of 0.01% by mass or more and 0.5% by mass or less in total, and the balance is Cu and inevitable impurities,
The content of C contained as the inevitable impurities is less than 5 ppm by mass, the content of Cr is less than 7 ppm by mass, the content of Mo is less than 5 ppm by mass, the content of W is less than 1 ppm by mass, and the content of V is less than 1 mass ppm, and the content of Nb is less than 1 mass ppm,
For the observed precipitate particles with a particle size of 5 nm or more and less than 100 nm, the number ratio of the precipitate particles with a particle size of 50 nm or more and less than 100 nm exceeds 5.0%, and the precipitates with a particle size of 5 nm or more and less than 15 nm the number ratio of particles exceeds 50%,
The number density of precipitate particles with a particle size of 50 nm or more and less than 100 nm is 2.0/μm ² or more, and the number density of precipitate particles with a particle size of 5 nm or more and less than 15 nm is 15/μm ² or more. cage,
A copper alloy characterized by having an electrical conductivity of 55% IACS or higher . 2. The copper alloy according to claim 1, further comprising Co; 0.005% by mass or more and 0.5% by mass or less. Furthermore, Ni; 0.005 mass% or more and 0.5 mass% or less, Al; 0.005 mass% or more and 0.5 mass% or less, Si; 3. The copper alloy according to claim 1 or 2, containing one or more. 4. The copper alloy according to any one of claims 1 to 3, having a tensile strength of 400 MPa or more. 5. The copper alloy according to any one of claims 1 to 4, having a Vickers hardness of 120 Hv or more.

Images