JP2007113093A - High-strength, high-electric conductivity, and heat-resistant copper alloy, and producing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength, high-electric conductivity, and heat-resistant copper alloy excellent in the heat resistance in addition to strength, electric conductivity, bending workability and bending property of foil, and to provide a producing method therefor. <P>SOLUTION: The high-strength, high electric conductivity, and heat resistant copper alloy contains, by mass ratio, 4-20% Ag as a whole, and further, contains 0.01-0.1% total content of additional elements of one or more selected from a group of Gd, Cr, Mg, Ti, Zr and the balance Cu with inevitable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-strength, high-conductivity copper alloy and a method for producing the same, and more particularly to a high-strength, high-conductivity copper alloy suitably used for electronic devices that require heat resistance such as terminals, connectors, switches, and the like, and a method for producing the same.

  Spring materials for electrical and electronic equipment such as terminals, connectors, switches, and relays are required to have excellent spring characteristics, bending workability, and electrical conductivity. Conventionally, phosphor bronze has been used. High-strength, high-conductivity alloys have been developed due to the demand for ultra-small size. In particular, in recent years, electronic parts have been highly integrated, and the amount of current flowing through the circuit of the electronic parts has also increased significantly. For this reason, a large amount of Joule heat is generated in the electronic component during use, and a considerable amount of heat is applied to the material of the component. Thus, copper alloys that are materials for electronic components are required to have high heat resistance in addition to the conventional high strength and high conductivity.

  On the other hand, rolled copper foil and electrolytic copper foil are mainly used as printed wiring boards often used in electronic circuits of electronic devices. In particular, a rolled copper foil having excellent flexibility is suitable as a flexible copper-clad laminate (flexible substrate). Furthermore, when the circuit requires strength and heat resistance, a copper alloy foil is used. These rolled copper foils and rolled copper alloy foils are also required to have high strength and high conductivity in the same manner as the copper alloy for spring materials due to the recent miniaturization of electronic components.

  In general, when a strengthening element is added to Cu to increase the strength, the electrical conductivity decreases, while on the other hand, increasing the Cu purity to increase the electrical conductivity has a relationship of decreasing the strength. Therefore, an alloy system (double phase alloy) in which the second phase is crystallized in the Cu matrix has been developed. In this alloy, the second phase is dispersed in a fiber shape by being strongly processed and has a strength equal to or higher than that of phosphor bronze and the parent phase is Cu. Therefore, the conductivity is 60% IACS (international annealed copper standard: High electrical conductivity exceeding the ratio of electrical conductivity to annealed standard annealed copper is obtained. As this multiphase alloy system, Cu—Cr, Cu—Fe, Cu—Nb, Cu—W, Cu—Ta, Cu—Ag, and the like are known (for example, see Patent Documents 1 to 8).

In the case of the above prior art, means such as drawing and rolling are used as a processing method for stretching the second phase into a fiber shape. For example, in Patent Documents 1 and 2 below, when a multi-phase alloy is rolled and manufactured, the second phase is sufficiently stretched in the rolling direction to become fibrous, and the rolling proceeds in the direction perpendicular to the rolling direction (the longitudinal direction of the rolled material). It also describes that the strength of the rolled material is also improved.
In general, a multiphase alloy is an alloy that is strengthened by using a composite law or increasing the area of a heterophase interface, and is strengthened by dispersing a second phase in a ribbon shape. Here, the second phase crystallized without dissolving in copper is formed by dispersing in a ribbon shape in the copper matrix by strong processing, so the area of the heterophase interface is increased and the material is strengthened Great effect. For this reason, as the second phase is more dispersed (if the volume fraction is the same, it is finely dispersed), the second phase is more easily stretched, and the degree of processing is increased, so that the strength is increased.

JP-A-6-192801 JP-A-6-279894 JP-A-9-104935 JP-A-9-235633 Japanese Patent Laid-Open No. 9-249925 JP-A-10-53824 Japanese Patent Laid-Open No. 10-140267 Japanese Patent Publication No. 48-34652

However, in the case of the conventional multiphase copper alloy, although the strength is increased by the second phase extending in a ribbon shape, there is a problem that the second phase has low heat resistance. For example, if a double-phase copper alloy material is cold-rolled and then annealed at 150 ° C. to 300 ° C. to ensure conductivity and bendability, the second phase becomes spherical and the strength is extremely reduced.
That is, the present invention has been made in order to solve the above-mentioned problems, and in addition to strength, conductivity, bending workability, and flexibility when formed into a foil, high strength and high conductivity heat resistance excellent in heat resistance. An object is to provide a copper alloy and a method for producing the same.

  As a result of various studies, the present inventors have found that the above problem can be solved by stretching the second phase crystallized in the Cu matrix, preferably in a ribbon shape, having a predetermined alloy composition. In particular, the present inventors have found that when a specific element is present in the second phase, the spheroidization of the second phase due to heat treatment can be suppressed and the heat resistance can be further improved.

In order to achieve the above object, the high-strength, high-conductivity heat-resistant copper alloy of the present invention contains Ag in a mass ratio of 4% or more and 20% or less as a whole, and a group of Gd, Cr, Mg, Ti, Zr. One or more additive elements selected from the group consisting of 0.01% to 0.1% in total amount, the balance being made of Cu and inevitable impurities.
A rolled material of a two-phase alloy composed of a Cu matrix and a second phase containing Ag, and when viewed from the thickness direction of the rolled material, the thickness of the second phase is 1 μm or less and adjacent It is preferable to have a layered structure in which the interval between the second phases is 1 μm or less, and it is preferable that 50% by mass or more of the additive element is distributed in the second phase. It is preferable to satisfy MBR / t ≦ 1 in the W bending test.

  The manufacturing method of the high-strength, high-conductivity heat-resistant copper alloy of the present invention contains Ag in a mass ratio of 4% or more and 20% or less as a whole, and one or more selected from the group of Gd, Cr, Mg, Ti, Zr After adding and totaling 0.01% or more and 0.1% or less of the additive elements of the above, with the balance being a copper alloy consisting of Cu and inevitable impurities, at least cold working and heat treatment after the cold working are performed. At least once, the heat treatment is performed at 350 ° C. to 550 ° C. for 0.5 to 20 hours, and the total degree of cold working is 90% or more.

  According to the present invention, a copper alloy excellent in heat resistance can be obtained in addition to strength, conductivity, bending workability, and flexibility when formed into a foil.

  Hereinafter, embodiments of a high-strength, high-conductivity heat-resistant copper alloy (hereinafter referred to as “copper alloy” as appropriate) according to the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

<Composition>
The copper alloy according to the present invention contains Ag in a mass ratio of 4% or more and 20% or less as a whole, and further contains one or more additive elements selected from the group of Gd, Cr, Mg, Ti, and Zr in a total amount of 0.2%. The content is 01% or more and 0.1% or less, and the balance is made of Cu and inevitable impurities.

[Ag]
When Ag is contained in an amount of 4% or more, it is crystallized as an Ag phase (second phase) in the Cu matrix, and high strength can be obtained. When the content of Ag is less than 4%, the number of Ag crystallized substances is drastically reduced, so that the effect of composite strengthening by the Ag phase is small. On the other hand, if the content exceeds 20%, the heat resistance and hot workability deteriorate, and the effect of increasing the strength is saturated. Further, if the content exceeds 20%, the amount of Ag crystallized at the Cu grain boundary during heat treatment or hot working becomes very large. descend.
In addition, content of Ag shows the value in the whole alloy which match | combined Cu mother phase and Ag phase.
In the Ag phase, Ag is crystallized from a molten alloy containing Cu and a predetermined chemical component during casting. The Ag phase contains 50% or more of Ag. The Ag phase is crystallized, for example, in a needle shape in the Cu matrix, but the crystallization form is not limited to this. In addition, although Cu mother phase contains 90% or more of Cu, for example, it is not restricted to this.
The Ag phase can be observed as a composition different from the parent phase by a BSE (backscattered electron) image of an SEM (scanning electron microscope) after polishing the cross section of the rolled structure after the final process. If the structure is difficult to observe, etching or electropolishing may be performed.

[Form of Ag phase]
Double-phase alloys utilize strengthening (elastic effect) based on the composite law of Ag phase, which is stronger than Cu matrix, or strengthening (plastic effect) by increasing the area of the heterophase interface (between Cu matrix and Ag phase). is doing. When the multiphase alloy is strongly processed, the Ag phase as the second phase is finely dispersed in the form of fibers or ribbons, and the area of the heterogeneous interface is increased to strengthen the multiphase alloy.
For this reason, the more the second phase is dispersed in the Cu matrix (finely dispersed if the volume fraction is the same), the easier the second phase is stretched, and the higher the workability, the higher the strength. Can be achieved.

For this reason, the rolled material has a high degree of workability. When viewed from the thickness direction of the rolled material, the thickness of the Ag phase is 1 μm or less and the distance between adjacent Ag phases is 1 μm or less. It preferably has a layered structure.
With such a structure, a high-strength alloy having a 0.2% proof stress of 700 MPa or more is obtained by the fibrous or ribbon-like Ag phase. Furthermore, when the workability is 99.5% or more in this alloy, the thickness of the Ag phase when viewed from the thickness direction of the rolled material is about 100 nm, and a high strength with a 0.2% proof stress exceeding 1 GPa is obtained. .
The Ag phase may be “fibrous” or “ribbon” in terms of obtaining high strength, but if the Ag phase is ribbon, the Ag phase is less likely to be sheared and has heat resistance. While improving, bending workability improves rather than a fibrous phase.

Here, the fibrous form means that the Ag phase is stretched in the rolling direction, but is hardly stretched in the direction perpendicular to the rolling direction (assuming that rolling proceeds in the longitudinal direction of the rolled material). The one that is in the shape. The ribbon shape means that the Ag phase is stretched in the rolling direction and is also stretched in the direction perpendicular to the rolling direction to show a tongue-like shape. When the ribbon-shaped Ag phase is included, bending workability when the material is bent in the direction perpendicular to the rolling direction is improved.
As a form in which the Ag phase is stretched also in the direction perpendicular to the rolling to form a ribbon, for example, when the structure is observed from the direction perpendicular to the rolling, the length of each Ag phase (length in the direction perpendicular to the rolling / The aspect ratio represented by (the length in the thickness direction) is 10 or more.

[Additive elements]
The additive elements (Gd, Cr, Mg, Ti, and Zr) are dissolved in the Ag phase to improve heat resistance. It is necessary to contain at least 0.01% and no more than 0.1% of one or more of the above additive elements. When the total content is less than 0.01%, the additive elements are not sufficiently dissolved in the Ag phase, and the effect of improving heat resistance is reduced. On the other hand, if the total amount exceeds 0.1%, the electrical conductivity of the alloy is remarkably lowered.
Here, the additive element is preferably distributed in the Ag phase by 50 mass% or more. When the distribution amount of the additive element to the Ag phase is less than 50%, the purity of the Ag phase is high, so the effect of improving the heat resistance is reduced, and the distribution amount of the additive element to the Cu matrix is increased. The conductivity tends to decrease.
In addition, the ratio by which an additional element is distributed to Ag phase can be calculated | required as follows, for example. First, the cross section of the ingot is mechanically polished, SDS (scanning electron microscope) equipped with EDS (energy dispersive X-ray analysis) or WDS (wavelength dispersive X-ray analysis), or FE-SEM (electrolytic emission scanning electron) Using a microscope), X-ray analysis of the crystallized product and the mother phase is performed. Thereby, the concentration analysis of the additive element contained in each of the Cu matrix and the Ag phase is performed. Here, the concentration of each phase is obtained in advance with reference to the peak value of a standard sample not containing an additive element. In order to perform highly accurate analysis, WDS is preferable to EDS, and it is preferable to use a field emission electron beam source such as FE-SEM. However, wet analysis is desirable for accurate quantitative analysis.
Actually, for the ingot in a predetermined field of view, the ratio of the additive element concentration in the matrix and the additive element concentration in the Ag phase is obtained, and (the concentration of the additive element in the Ag phase / the concentration of the additive element in the Cu matrix). It suffices if the relationship (density) ≧ 1.

The reason why the heat resistance is improved when the Ag phase contains an additive element is considered as follows. Generally, when a metal exceeds a predetermined temperature (recrystallization temperature) by heat treatment, it recrystallizes and softens rapidly. Therefore, heat resistance can be improved by raising the recrystallization temperature of the metal. Further, the recrystallization temperature rises due to the presence of impurities and the metal becoming an alloy at a predetermined ratio. Therefore, it is considered that when the additive element is contained in the Ag phase, the recrystallization temperature of the Ag phase rises and the heat resistance is improved.
In addition, when a certain amount or more of the additive element is added, the additive element precipitates in the form of a simple substance or a compound in the heat treatment during the cold working of the material or in the heat treatment after the cold working. At the same time, the recrystallization temperature increases.
Furthermore, the Ag phase in the multiphase alloy is subjected to shearing or tensile stress by cold working, and finally becomes a ribbon having a length on the order of several hundred nanometers. In this case, a portion of the Ag phase that is intensively subjected to shearing stress or tensile stress becomes extremely unstable and may be divided when exposed to high heat. On the other hand, when the additive element is dissolved in the Ag phase, the Ag phase is strengthened, and a stable form is maintained against shearing stress and tensile stress, which is considered to be a thermally stable structure.

[Inevitable impurities]
The content of inevitable impurities in the copper alloy need not be as clean as oxygen-free copper C1011 standardized in JIS H2123. For example, you may contain the component of the range normally mixed from a furnace material, a raw material, etc. The copper alloy may contain a total of 0.01% or less of one element selected from the group of Y, Yb, Nd, In, Pd, and Te. In addition, bending properties, conductivity, and strength are less likely to be impaired. In particular, when Y, Yb, or Nd is contained in the above range in the copper alloy, the heat resistance is increased.

<Method for producing copper alloy>
The method for producing a high-strength, high-conductivity heat-resistant copper alloy of the present invention has a step of performing cold working and heat treatment after the cold working at least once after the copper alloy having the above composition is melt-cast.
The heat treatment is performed at 350 ° C. to 550 ° C. for 0.5 to 20 hours. When the heat treatment is performed, the additive element dissolved in the Ag phase is precipitated in the Ag phase to further strengthen the Ag phase and further improve the heat resistance. Further, when heat treatment is performed in the above temperature range, the electrical conductivity is recovered to a value of about 50% or more. That is, as the degree of cold working, which will be described later, increases, the decrease in conductivity increases, but the conductivity can be recovered by setting the heat treatment conditions in the above range.
When the heat treatment temperature is less than 350 ° C., precipitation strengthening of the Ag phase by the additive element becomes insufficient, and the electrical conductivity is not recovered. Further, when the heat treatment temperature exceeds 550 ° C., the electrical conductivity is greatly recovered, but the material is softened and the heat resistance is lowered.

  The total degree of cold working is 90% or more. In the production method of the present invention, due to the characteristics of the multiphase alloy, the strength tends to increase as the workability increases. If the total workability is 90% or more, a strength of about 700 MPa or more can be secured. it can. The total workability is the workability from chamfering to the end of cold rolling.

  Conventionally, a rolled material of a copper-based multiphase alloy has a thermal expansion coefficient equivalent to that of a semiconductor element, and thus has been used as a heat dissipation component such as a heat sink or a heat spreader. However, although it has high strength and high conductivity, if heat treatment is performed to ensure bendability, the strength is extremely lowered, so that conventional materials cannot be used for spring materials such as terminals. As described above, according to the present invention, not only can a copper alloy having both good conductivity and strength be obtained, but also because it has excellent heat resistance, it can be used as a spring material for terminals and the like for electronic devices. It can make a significant contribution to industrialization, such as reducing the weight, making it super lightweight, and improving performance. When the copper alloy of the present invention is used as a foil, it can be applied to, for example, a printed wiring board, particularly a flexible copper-clad laminate.

  In addition, this invention is not limited to the said embodiment. Moreover, as long as there exists an effect of this invention, the copper alloy in the said embodiment may contain another component.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.

1. Manufacture of a sample About each Example and the comparative example, electrolytic copper was melted | dissolved in vacuum and the element of the predetermined composition shown in Table 1 was added, respectively, and the ingot was cast. After the ingot was homogenized and annealed, it was cold-rolled at the total workability shown in Table 2 and then heat-treated to obtain a test piece having a plate thickness of 1.5 mm. The heat treatment was performed at a predetermined temperature at which the second phase was not divided.
In addition, the total processing degree of each Example: 99.7%, and heat treatment temperature: 450 ° C. × 1 h.

2. Sample Evaluation (1) Confirmation of Ag Phase For each example and comparative example, the ingot cross section was mechanically polished and crystallized material was observed with an optical microscope, or SEM (scanning electron microscope) or FE-SEM (electrolysis) A BSE image of the crystallized product was taken using an emission scanning electron microscope. This confirmed the two-phase alloy.
Also, the cross section of the ingot is mechanically polished, SDS (scanning electron microscope) equipped with EDS (energy dispersive X-ray analysis), WDS (wavelength dispersive X-ray analysis), or FE-SEM (electrolytic emission scanning). The crystallized product was subjected to elemental analysis using an electron microscope. A point analysis of the crystallized product was performed, or an elemental map of the parent phase and the crystallized product was obtained. This confirmed the Ag phase.

(2) Measurement of tensile strength According to JIS Z2241, the tensile test was done about the rolling parallel direction of the sample of each Example and the comparative example, and tensile strength (0.2% yield strength (YS)) was measured. The sample was produced according to the above JIS. If the tensile strength is 700 MPa or more, it can be determined that the tensile strength is excellent.
(3) Measurement of conductivity The conductivity of the sample was determined by the four probe method. If the conductivity is 50% IACS or more, it can be determined that the conductivity is excellent.
When the tensile strength was 700 MPa or more and the electrical conductivity was 50% IACS or more, it was judged that the copper alloy was excellent in both strength and conductivity.
(4) Bending workability Each sample was subjected to a W bending test in accordance with JIS H3110 and H3130, and a minimum bending radius (MBR) of a 10 mm wide sample (t: sample thickness) extending in the direction perpendicular to the rolling direction and the rolling parallel direction, respectively. Asked. And bending workability was evaluated according to the following criteria.
○: MBR / t ≦ 1 x: MBR / t> 1 (5) Heat resistance Annealing temperature at which the strength when each sample is annealed for 1 hour is half the strength of a sample that is not annealed Was determined as the semi-softening temperature. If the semi-softening temperature is 400 ° C. or higher, it can be determined that the heat resistance is excellent.

(6) Evaluation of Flexibility of Foil The test pieces of the respective Examples and Comparative Examples were further cold-rolled to obtain a foil having a plate thickness of 0.050 mm (50 μm). The flexibility of this foil was evaluated by the MIT flexibility test. The test conditions were a bending radius of 2.0 mm, a bending load of 500 g, a bending angle of 135 ° to the left and right, the number of times of bending until the sample broke, and the following criteria were evaluated.
○: The number of times of bending is greater than the reference example (usually more than 100 times)
-: The number of bendings is the same as the reference example ×: The number of bendings is less than the reference example

  The results obtained for the rolled sheets are shown in Tables 1 and 2, and the results obtained for the foils are shown in Tables 3 and 4. In addition, "-" in each table | surface represents not having added the component.

表１から明らかなように、各実施例の場合、強度、導電性、曲げ加工性、及び耐熱性に共に優れていた。又、表３の各実施例の箔の場合も、強度、導電性、屈曲性がいずれも優れ、性能上のバランスのよい銅合金を得ることができた。
なお、同じ実施例について表１と表３の強度を比較すると、箔にすることで強度を更に向上できることが判明した。

As is clear from Table 1, in each case, the strength, conductivity, bending workability, and heat resistance were all excellent. Moreover, also in the case of the foil of each Example of Table 3, the strength, the electroconductivity, and the flexibility were all excellent, and the copper alloy with the balance on performance was able to be obtained.
In addition, when the intensity | strength of Table 1 and Table 3 was compared about the same Example, it became clear that intensity | strength can further be improved by using foil.

On the other hand, in the case of the comparative example 1 which does not contain an additive element, heat resistance was remarkably inferior.
In the case of Comparative Examples 2 and 3 in which the Ag content was less than 4%, a two-phase alloy was not obtained, and the strength was greatly reduced. In the case of Comparative Example 3, the total content of additive elements exceeded 0.1%, and the electrical conductivity of the alloy also decreased.
In the case of Comparative Examples 4 and 5 in which the Ag content exceeded 20%, the bending workability was greatly reduced. In each of Comparative Examples 4 and 5, since Gd and Ti were added, the heat resistance did not decrease. Moreover, in the case of the comparative example 5, since the total content of the additive element exceeded 0.1%, the electrical conductivity of the alloy also decreased.

In the case of Comparative Examples 6 to 10 in which the total content of additive elements exceeded 0.1%, the electrical conductivity of the alloy was significantly reduced. Moreover, in the case of Comparative Examples 7-10, bending workability also fell. This is thought to be because the oxide and inclusions of the additive element were produced in the alloy due to the high content of the additive element, and this was the starting point for cracking during bending.
In the case of Comparative Example 11 in which the Ag content is less than 4% and the total content of the additive elements is less than 0.01%, a two-phase alloy cannot be obtained and the strength is greatly reduced, and the heat resistance Also declined.
In the case of Comparative Example 12 in which the Ag content exceeds 20% and the total content of the additive elements is less than 0.01%, the bending workability is greatly reduced and the heat resistance is also reduced.

  In the case of Comparative Examples 13 to 16 in which the total workability during alloy production was less than 90%, the strength was significantly reduced. In the case of Comparative Example 14, the conductivity was recovered because the heat treatment was performed before the processing. However, in the case of Comparative Example 15 where the heat treatment temperature was less than 350 ° C., no recovery of conductivity was observed. On the other hand, in the case of Comparative Example 16 in which the heat treatment temperature exceeded 550 ° C., the electrical conductivity was greatly recovered, but the material was softened and the heat resistance was inferior. This is considered because the precipitation form of the additive element in the Ag phase became coarse.

In the case of Comparative Example 17, in which the total degree of work during the manufacture of the alloy was 90% or more but was not heat-treated before working, the conductivity was poor.
In the case of Comparative Example 18 in which the total degree of work at the time of manufacturing the alloy is 90% or more but the heat treatment temperature before work is less than 350 ° C., the bending workability is inferior. This is presumably because the additive element in the Ag phase was finely precipitated by the low-temperature heat treatment, and the Ag phase was strengthened more than the parent phase.
Although the total degree of processing at the time of manufacturing the alloy was 90% or more, in the case of Comparative Example 19 in which the heat treatment temperature before processing exceeded 550 ° C., the heat resistance was poor. This is presumably because the additive element in the Ag phase was coarsely precipitated and the effect of improving the high-temperature strength of the Ag phase disappeared.

Claims (5)

Contains Ag in a mass ratio of 4% or more and 20% or less as a whole, and further contains one or more additive elements selected from the group of Gd, Cr, Mg, Ti, and Zr in a total amount of 0.01% or more and 0.1% or less. A high-strength, high-conductivity heat-resistant copper alloy that contains Cu and inevitable impurities. A rolled material of a two-phase alloy composed of a Cu matrix and a second phase containing Ag, and when viewed from the thickness direction of the rolled material, the thickness of the second phase is 1 μm or less and adjacent The high-strength, high-conductivity heat-resistant copper alloy according to claim 1, which has a layered structure in which the interval between the second phases is 1 µm or less. The high-strength, high-conductivity heat-resistant copper alloy according to claim 2, wherein the additive element is distributed in the second phase by 50 mass% or more. The high-strength, high-conductivity heat-resistant copper alloy according to any one of claims 1 to 3, which satisfies MBR / t ≦ 1 in a W bending test. Contains Ag in a mass ratio of 4% or more and 20% or less as a whole, and further contains one or more additive elements selected from the group of Gd, Cr, Mg, Ti, and Zr in a total amount of 0.01% or more and 0.1% or less. A copper alloy manufacturing method comprising, after melting and casting a copper alloy containing Cu and inevitable impurities, and performing cold working and heat treatment after the cold working at least once. The high-strength, high-conductivity heat-resistant copper alloy according to any one of claims 1 to 4, wherein the heat treatment is performed at 350 ° C to 550 ° C for 0.5 to 20 hours, and the total degree of cold working is 90% or more. Method.