TWI395824B - Cu-Ni-Si alloy for electronic materials - Google Patents

Description

Cu-Ni-Si alloy for electronic materials

The present invention relates to a precipitation hardening type copper alloy, and more particularly to a Cu-Ni-Si-Cr alloy which can be preferably used for various electronic machine parts.

For copper alloys for electronic materials used in various electronic machine parts such as lead frames, connectors, pins, terminals, relays, switches, etc., as their basic characteristics, it is required to achieve high strength and high electrical conductivity (or thermal conductivity) at the same time. ). In recent years, the high integration, miniaturization, and thinning of electronic components have been rapidly progressing, and accordingly, the level of requirements for copper alloys used in electronic machine parts has been increasing.

From the viewpoint of high strength and high electrical conductivity, in recent years, as a copper alloy for electronic materials, the amount of precipitation hardening type copper alloy is increasing to replace the previous solid solution strengthening represented by phosphor bronze, brass, and the like. Type copper alloy. In the precipitation hardening type copper alloy, by subjecting the solution-treated supersaturated solid solution to aging treatment, the fine precipitates are uniformly dispersed, thereby increasing the strength of the alloy and reducing the amount of solid solution elements in the copper. Improve electrical conductivity. Therefore, a material excellent in mechanical properties such as strength and elasticity and excellent in electrical conductivity and thermal conductivity can be obtained.

Among the precipitation-hardened copper alloys, Cu-Ni-Si-based copper alloys, which are generally called Carson-based alloys, are typical copper alloys having relatively high electrical conductivity, strength, stress relaxation properties, and bending workability. One of the alloys currently being actively developed in the industry. In the copper alloy, by making a fine Ni-Si system The intermetallic compound particles are precipitated into the copper matrix to achieve an increase in strength and electrical conductivity.

The precipitate of the Ni-Si-based intermetallic compound particles is generally composed of a stoichiometric composition. For example, Patent Document 1 discloses that the mass ratio of Ni to Si in the alloy is close to Ni ₂ as an intermetallic compound. The mass composition ratio of Si (atomic amount of Ni × 2: atomic weight of Si × 1), that is, by setting the weight concentration ratio of Ni to Si to be Ni/Si = 3 to 7, good electrical conductivity is obtained.

However, as described in Patent Document 1, by making the mass ratio of Ni to Si close to the mass composition ratio of Ni ₂ Si as an intermetallic compound (atomic amount of Ni × 2: atomic weight of Si × 1), it is possible to realize The improvement of the characteristics, but in reality, it can be found that the conductivity is reduced to some extent due to the excess Si.

Therefore, it is considered that an element such as Cr which forms a compound with Si can be added to be combined with excess Si to thereby increase the conductivity. Cr is one of the elements, and a Cr-containing Cu-Ni-Si alloy can be formed.

The Cu-Ni-Si-based alloy to which Cr is added as an alloying element is described in Patent Document 2 and Patent Document 3.

Patent Document 2 describes a heat treatment method for a Carson alloy, which is characterized in that at least Ni: 1.5 to 4.0% by weight, Si: 0.35 to 1.0% by weight, and at least a group selected from the group consisting of Zr, Cr, and Sn 1 kind of metal: 0.05~1.0% by weight, the remaining part is heated (or cooled) by the Carson alloy composed of Cu and unavoidable impurities, in the temperature range of 400~800 °C, so as to pull the above-mentioned Carson alloy The above-mentioned Carson alloy is heated (or cooled) in such a manner that the heat expansion shape becomes 1 × 10 ^-4 or less. According to this method, the ingot rupture at the time of heat treatment can be prevented.

Patent Document 3 describes a high tensile copper alloy excellent in bending workability, which is characterized by containing Ni: 2 to 5% by weight, Si: 0.5 to 1.5% by weight, Zn: 0.1 to 2% by weight, and Mn: 0.01 to 0.1% by weight, Cr: 0.001 to 0.1% by weight, Al: 0.001 to 0.15% by weight, Co: 0.05 to 2% by weight, and the content of S as an impurity component is limited to 15 ppm or less, and the balance is Cu and inevitably The composition of impurities. According to the invention, Cr strengthens the grain boundary of the ingot, and is an element which improves hot workability. Further, when the content of Cr exceeds 0.1% by weight, the molten metal is oxidized, resulting in deterioration of castability. Further, it is described that the copper alloy is used in a Kripto furnace, and the charcoal is coated in the atmosphere to be melt-cast.

Further, from the viewpoint of the compound of Cr and Si, Patent Document 4 can be cited. Patent Document 4 contains Cr: 0.1 to 0.25 wt%, Si: 0.005 to 0.1 wt%, Zn: 0.1 to 0.5 wt%, Sn: 0.05 to 0.5 wt%, and a weight ratio of Cr to Si of 3 to 25 And the remaining portion is composed of Cu and unavoidable impurities, and in the copper mother phase, CrSi having a size of 0.05 μm to 10 μm exists at a number density of 1 × 10 ³ to 5 × 10 ⁵ /mm ² The copper alloy for electronic equipment having excellent etching workability and press workability in which the size of the compound and the Cr compound (other than the CrSi compound) is 10 μm or less is described as the hot working temperature and the aging heat treatment temperature of the ingot. According to this method, both etching workability and press punchability can be preferably used.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-207229 [Patent Document 2] Japanese Patent No. 2862942 [Patent Document 3] Japanese Patent No. 3049137 [Patent Document 4] Japanese Patent Laid-Open Publication No. 2005-113180

The Cr-containing Cu-Ni-Si alloy of the alloy of the present invention is also in conformity with the recent demand for rapid improvement in the material properties of the electronic components, such as rapid integration, miniaturization, and thinning.

However, in Patent Document 1, Cr is not added, and in reality, it is found that the conductivity is lowered to some extent due to excessive Ni and Si, and the characteristic is not improved. In Patent Document 2 and Patent Document 3, Cr is added to the Cu-Ni-Si alloy, but the purpose of adding Cr in Patent Document 2 is to achieve solid solution strengthening, and the purpose of Patent Document 3 is to improve heat. The processability has not been found to be related to the Cr-Si compound which is the key to the present invention. Therefore, the means for solving the problems to be solved by the present invention cannot be easily considered from the patent documents.

Patent Document 4 describes that the etching processability and the press formability are improved by controlling the number density and size of the CrSi compound. However, since no Ni is added, it is not necessary to consider the formation of the Ni-Si compound and only the Cr-Si compound is considered. The conditions for formation may be sufficient, and the means for solving the problem to be solved by the present invention cannot be easily considered.

In view of the above, it is an object of the present invention to provide a Cassson-based alloy which exhibits a high-strength and high-conductivity by improving the Cr addition effect in a Cu-Ni-Si-based alloy.

The present inventors conducted intensive studies to solve the above problems, and as a result, found the following invention. In the Cu-Ni-Si-based alloy, Si is set to an excessive composition with respect to Ni, and Ni-deposited in accordance with the amount of addition of Ni is surely precipitated to achieve high strength, and on the other hand, excess Si and added The Cr reaction produces a compound to achieve high conductivity. Further, the key point of the present invention is to control the growth of the Cr-Si compound in such a manner as to avoid excessive growth of the combination of Cr and Si, and to prevent the Si compounded by Ni from becoming insufficient. Specifically, the present inventors focused on the composition, size, and number density of the Cr-Si compound, and found that the effect can be better exhibited by controlling the temperature and the cooling rate of the heat treatment step.

That is, the present invention is a copper alloy for an electronic material containing Ni: 1.0 to 4.5% by mass, Si: 0.50 to 1.2% by mass, and Cr: 0.003 to 0.3% by mass (wherein the weight ratio of Ni to Si is 3≦Ni/Si≦5.5), and the remainder consists of Cu and unavoidable impurities. For Cr-Si compounds with a size of 0.1 μm~5 μm dispersed in the material, the Cr in the dispersed particles is relatively The atomic concentration ratio of Si is 1 to 5, and the dispersion density thereof is 1 × 10 ⁶ /mm ² or less.

(2) A copper alloy for an electronic material according to (1), wherein a dispersion density of a Cr-Si compound having a size of from 0.1 μm to 5 μm is higher than 1 × 10 ⁴ /mm ² .

(3) The copper alloy for an electronic material according to (1) or (2), which further contains 0.05 to 2.0% by mass of one or more selected from the group consisting of Sn and Zn.

(4) The copper alloy for an electronic material according to (1) or (2), which further contains 0.001 to 2.0% by mass selected from the group consisting of Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al One or two or more of Co and Fe.

(5) A copper-extended product which uses the copper alloy of (1) or (2).

(6) An electronic machine part using the copper alloy of (1) or (2).

According to the present invention, the effect of adding the alloying element Cr can be better exhibited, so that a Cassson-based copper alloy for an electronic material having remarkably improved strength and electrical conductivity can be obtained.

Ni and Si addition amount

Ni and Si are formed by forming an Ni hydride (Ni ₂ Si or the like) as an intermetallic compound by performing appropriate heat treatment to achieve high strength without deteriorating conductivity. The quality of Si and Ni is preferably 3 ≦ Ni / Si ≦ 5.5 which is close to the stoichiometric composition as described above, and more preferably 3.5 ≦ Ni / Si ≦ 5.0.

However, even if Ni/Si has a ratio of the above range, if the Si addition amount is less than 0.5% by mass, the required strength cannot be obtained, and if it exceeds 1.2% by mass, the strength can be increased, but the conductivity is remarkable. When it is lowered, the liquid phase is further generated by the segregation portion, resulting in a decrease in hot workability and thus is not preferable. Therefore, Si: 0.5 to 1.2% by mass may be used, and preferably 0.5 to 0.8% by mass. The Ni addition amount may be set so as to satisfy the above-described preferable ratio according to the amount of addition of Si, and may be balanced with the amount of Si added, and may be Ni: 2.5 to 4.5% by mass, preferably Ni: 3.2 to 4.2% by mass. More preferably Ni: 3.5~4.0 quality%.

Cr addition amount

In the conventional Cu-Ni-Si alloy, when the concentration of Ni-Si is increased, the total number of precipitated particles is increased, so that the strength by precipitation strengthening can be increased. On the other hand, as the concentration of the addition increases, the amount of solid solution which does not contribute to precipitation increases, so that the electrical conductivity decreases, and as a result, the peak intensity of the aging precipitation increases, but the peak intensity of the electrical conductivity decreases. However, when 0.003 to 0.3% by mass of Cr, preferably 0.01 to 0.1% by mass of Cr is added to the above Cu-Ni-Si-based alloy, Cu- having the same Ni-Si concentration is used in the final characteristics. Compared with the Ni-Si alloy, the electrical conductivity can be increased without impairing the strength, and the hot workability can be further improved to improve the material utilization rate.

When the composition of the particles precipitated in the Cr-Ni-Si-based alloy is precipitated, the precipitated particles of the bcc structure containing Cr as a main component are easily precipitated, but the compound with Si is also likely to be precipitated. By performing appropriate heat treatment, Cr can be easily precipitated in a copper mother phase, that is, a chrome telluride (Cr ₃ Si or the like) which is a compound of Si. Therefore, in combination with alloying properties, solution treatment, cold aging, and aging treatment are employed. In the step, undissolved solid solution Si as Ni ₂ Si or the like can be analyzed as a Cr—Si compound. Therefore, the decrease in the electrical conductivity due to the solid solution Si can be suppressed, and the increase in the electrical conductivity can be achieved without impairing the strength.

At this time, if the Si concentration in the Cr particles is low, Si remains in the matrix phase, and thus the conductivity is lowered. On the other hand, if the Si concentration in the Cr particles is high, the Ni-Si particles are precipitated. The Si concentration will decrease and the strength will decrease. Further, when the Si concentration in Cr is high, coarse The Cr-Si compound increases, and the bending, fatigue strength, and the like deteriorate. Further, even if the cooling rate after solutionization is slowed down or the aging heat treatment time is excessively extended, the Cr-Si compound is coarsened to lower the Si concentration of the Ni-Si-forming compound, thereby causing the Ni-Si compound to be strengthened. insufficient. The reason for this is that Si in Cu diffuses faster than Cr to Ni, so that the Cr-Si compound is easily coarsened, and the precipitation rate of the Cr-Si compound becomes faster than the precipitation rate of the Ni-Si compound.

Therefore, the composition, size, and density of the Cr-Si compound can be controlled by controlling the cooling rate after solutionization to avoid the conditions of higher temperature and longer aging conditions. Therefore, the Cr concentration is set to 0.003 mass% to 0.3 mass%, and the atomic concentration ratio of Cr to Si in the Cr-Si compound is set to 1 to 5.

Further, since Cr is preferentially precipitated to the grain boundary during the cooling process during the melt casting, the grain boundary can be strengthened, and cracking during hot working is hard to occur, and the material utilization rate can be suppressed from being lowered. That is, Cr precipitated to the grain boundary during the melt casting can be re-dissolved in the solution treatment or the like, and a telluride is formed in the subsequent aging precipitation. In the usual Cu-Ni-Si alloy, the amount of Si added does not contribute to the precipitation of Si, which is still dissolved in the matrix phase and suppresses the increase in conductivity, but by adding the Cr of the telluride forming element, The telluride is further precipitated, so that the amount of solid solution Si can be reduced as compared with the conventional Cu-Ni-Si alloy, so that the electrical conductivity can be increased without impairing the strength.

Size and dispersion density of Cr-Si compounds

The size of the Cr-Si compound affects bending workability, fatigue strength, and the like. When the size of the Cr-Si compound is 5 μm or more, or 0.1 to 5 μm, the dispersion density of the Cr-Si compound exceeds 1 × 10 ⁶ / At mm ² , the bending workability or the fatigue strength is remarkably deteriorated. Further, the number density affects the excessive or insufficient concentration of Si in the mother phase, so that the desired strength characteristics cannot be obtained in a state where a large amount of particles are dispersed in a large amount. Therefore, the upper limit of the dispersion density may be 1 × 10 ⁶ /mm ² or less, preferably 5 × 10 ⁵ / mm ² or less, more preferably 1 × 10 ⁵ / mm ² or less. Further, in the case of 1 × 10 ⁴ /mm ² or less, the effect of improving by Cr addition is small, and therefore it is desirable to exceed 1 × 10 ⁴ /mm ² .

Sn and Zn

In the Cu-Ni-Si-based alloy of the present invention, one or two or more selected from the group consisting of Sn and Zn are added in a total amount of 0.05 to 2.0% by mass, whereby stress relaxation characteristics and the like can be improved without impairing too much. Large strength and electrical conductivity. When the amount is less than 0.05% by mass, the effect is insufficient. When the amount is more than 2.0% by mass, the manufacturability such as castability and hot workability and the electrical conductivity of the product are impaired. Therefore, it is preferably added in an amount of 0.05 to 2.0% by mass.

Other added elements

By adding specific amounts of Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al, Co, and Fe, various effects can be exhibited, and by complementing the feet, not only the strength and conductivity can be improved. Moreover, the manufacturability such as bending workability, electroplating property, or improvement in hot workability by refinement of the ingot structure can be improved, and therefore, in the Cu-Ni-Si alloy of the present invention, One or two or more of these elements are added in an amount of 2.0% by mass or less based on the total amount. For the added amount, if the total amount of the elements is less than 0.001% by mass, the desired effect cannot be obtained, and When the amount is more than 2.0% by mass, the decrease in electrical conductivity or deterioration in manufacturability is remarkable. Therefore, the total amount is preferably 0.001 to 2.0% by mass, more preferably 0.01 to 1.0% by mass.

Further, elements not specifically described in the present specification may be added within a range that does not adversely affect the characteristics of the Cu-Ni-Si alloy of the present invention.

Next, the manufacturing method of the present invention will be described. The Cu-Ni-Si alloy of the present invention can be produced by a conventional method for producing a Cu-Ni-Si alloy, in addition to the conditions for controlling the solution treatment and aging treatment of the Ni-Si compound and the Cr-Si compound. The manufacturer should be able to select the optimum manufacturing method according to the composition and the characteristics sought, and therefore, the general manufacturing method to be exemplified will be described below.

First, an electric melting furnace is used to melt raw materials such as copper, Ni, Si, and Cr to obtain a molten metal having a desired composition. The molten metal is then cast into an ingot. Thereafter, hot rolling is performed, and cold rolling and heat treatment are repeatedly performed to form a strip or foil having a desired thickness and characteristics. The heat treatment has a solution treatment and an aging treatment. In the solution treatment, heating is performed at a high temperature of 700 to 1000 ° C to dissolve the Ni-Si-based compound and the Cr-Si-based compound in the Cu mother phase, and the Cu mother phase is recrystallized. The solution treatment may also be used by hot rolling.

In the solution treatment, the cooling rate is also as important as the heating temperature. Since the cooling rate after heating has not been previously controlled, a water tank is provided on the exit side of the heating furnace to perform water cooling, or air cooling in an atmospheric atmosphere. At this time, the cooling rate is easily caused by the setting of the heating temperature. The previous cooling rate varies from 1 ° C / sec to 10 ° C / sec. Therefore, it is difficult to carry out the control of the characteristics of the alloy system as exemplified in the present invention.

The cooling rate is desirably in the range of 1 ° C / sec to 10 ° C / sec. In the aging treatment, heating is carried out for more than 1 h in a temperature range of 350 to 550 ° C, typically for 3 to 24 h, so that the compound of Ni and Si which are solid solution in the solution treatment and the compound of Cr and Si Precipitated into fine particles. With this aging treatment, the strength and electrical conductivity increase. In order to obtain higher strength, cold rolling is sometimes performed before and/or after aging. Further, when cold rolling is performed after aging, stress reduction annealing (low temperature annealing) may be performed after cold rolling.

In one embodiment, the Cu-Ni-Si-based copper alloy of the present invention can have a guaranteed stress of 780 MPa or more and a conductivity of 45% IACS or more, and a 0.2% proof stress of 860 MPa or more. The conductivity is 43% IACS or more, and the 0.2% proof stress is 890 MPa or more and the conductivity is 40% IACS or more.

The Cu-Ni-Si alloy of the present invention can be processed into various copper-stretching products such as plates, strips, tubes, rods and wires. Further, the Cu-Ni-Si-based copper alloy of the present invention can be used for simultaneously requiring high strength and Electronic equipment parts such as lead frames, connectors, pins, terminals, relays, switches, and foils for secondary batteries with high electrical conductivity (or thermal conductivity).

[Examples]

The specific examples of the invention are shown below, but are provided to further understand the invention and its advantages, and are not intended to limit the invention.

The copper alloy used in the examples of the present invention has a composition in which Sn, Zn, Mg, Mn, Co, and Ag are appropriately added to a copper alloy having a change in the contents of Ni, Si, and Cr as shown in Table 1. Further, the copper alloys used in the comparative examples were each a Cu-Ni-Si alloy having parameters outside the range of the present invention.

A copper alloy having various compositions described in Table 1 was cast at a temperature of 1300 ° C by a high-frequency melting furnace, and cast into an ingot having a thickness of 30 mm. Then, the ingot was heated at a temperature of 1000 ° C, and then hot rolled to a thickness of 10 mm, and then rapidly cooled. In order to remove the scale of the surface, plane cutting was performed to a thickness of 8 mm, followed by cold rolling into a plate having a thickness of 0.2 mm. Then, the solution treatment was carried out in an Ar gas atmosphere, and the amount of Ni and Cr added was maintained at a temperature of 800 to 900 ° C for 120 seconds, and then the cooling rate was changed to be cooled to room temperature. The cooling rate is controlled by changing the flow rate of the gas to be sprayed to the sample after heating, and the time until the highest temperature of the sample is cooled to 400 ° C is measured as the cooling rate. The furnace cooling rate when the gas was not blown was 5 ° C / s, and as an example of the retarding cooling rate, the cooling rate when the temperature was lowered while controlling the heating output was set to 1 ° C / s. Thereafter, the mixture was cold-rolled to a thickness of 0.1 mm, and finally, an aging treatment was carried out for 1 to 12 hours in an inert atmosphere at a temperature of 400 to 550 ° C depending on the amount of addition to prepare a sample.

The properties of each alloy obtained in this manner were evaluated for strength and electrical conductivity. For the strength, a tensile test in the parallel direction of the rolling was performed to determine a 0.2% proof stress (YS; MPa), and the electrical conductivity (EC; % IACS) was determined by measuring the volume resistivity of the W bridge.

The evaluation of the bendability was carried out by using a W-shaped mold and performing a 90° bending process under the condition that the ratio of the sample thickness to the bending radius was 1. In the evaluation, the surface of the bent portion was observed with an optical microscope, and the case where no crack was observed was judged to be practically no problem, and ○ was marked, and the case where the crack was observed was indicated as ×. In the fatigue test, an alternating stress was applied in accordance with JIS Z 2273, and the stress (MPa) of the number of times of repetition until the fracture was determined was 10 ⁷ times.

The observation of the Cr-Si compound is carried out by electrolytically grinding the surface of the material, and by using FE-AES observation, particles having a size of 0.1 μm or more are used as targets, and splashing is performed by using Ar ⁺ to remove the actual The element (C, O) adsorbed on the surface layer is measured, and then the Auger spectrum of each particle is measured, and when the detected element is converted into a weight concentration by the sensitivity coefficient method as a semi-quantitative value, Cr is detected. The object with Si is the object. The "composition", "size", and "dispersion density" of the Cr-Si compound are defined as the average composition and minimum of Cr-Si particles having a size of 0.1 to 5 μm obtained by analyzing FE-AES. The diameter of the circle and the average number of observation fields.

The results are shown in Tables 1 and 2.

In Inventive Examples 1 to 25, the dispersion density of the Cr-Si compound was 1 × 10 ⁶ or less and the Cr/Si was in the range of 1 to 5 by an appropriate cooling rate, so that good characteristics were obtained.

On the other hand, in Comparative Examples 1 to 3, since the cooling rate was slow, the Cr-Si compound was excessively grown, and sufficient strength could not be obtained, and the bending workability was also poor.

In Comparative Examples 4 and 5, since the cooling rate was fast, the Cr-Si compound did not grow, and excess Si dissolved in the alloy, and the strength and electrical conductivity deteriorated. In Comparative Examples 6 and 7, since the aging temperature was high, the Cr-Si compound was excessively grown, and sufficient strength could not be obtained, and the bending workability was also poor. In Comparative Examples 8 and 9, since the concentration of Cr was too high, the Cr-Si compound was excessively grown, and sufficient strength could not be obtained, and the bending workability was also poor.

Claims (6)

A copper alloy for electronic materials, which contains Ni: 1.0 to 4.5% by mass, Si: 0.50 to 1.2% by mass, Cr: 0.003 to 0.3% by mass, and a mass ratio of Ni to Si of 3 ≦ Ni / Si ≦ 5.5, and the balance Partly consists of Cu and unavoidable impurities. For a Cr-Si compound having a size of 0.1 μm to 5 μm dispersed in the material, the atomic concentration ratio of Cr to Si in the dispersed particles is 1 to 5, The dispersion density is 1 × 10 ⁶ /mm ² or less. A copper alloy for an electronic material according to the first aspect of the invention, wherein a dispersion density of a Cr-Si compound having a size of 0.1 μm to 5 μm is higher than 1 × 10 ⁴ /mm ² . The copper alloy for an electronic material according to the first or second aspect of the invention, which further contains 0.05 to 2.0% by mass of one or more selected from the group consisting of Sn and Zn. The copper alloy for electronic materials according to any one of claims 1 to 2, further comprising 0.001 to 2.0% by mass selected from the group consisting of Mg, Mn, Ag, P, As, Sb, Be, B, Ti One or two or more kinds of Zr, Al, Co, and Fe. A copper-extended product which uses the copper alloy of claim 1 or 2. An electronic machine part using the copper alloy of claim 1 or 2.