JP4418028B2 - Cu-Ni-Si alloy for electronic materials - Google Patents

Description

  The present invention relates to a precipitation hardening type copper alloy, and more particularly to a Cu—Ni—Si—Cr alloy suitable for use in various electronic device parts.

  Copper alloys for electronic materials used in various electronic equipment components such as lead frames, connectors, pins, terminals, relays, switches, etc., have both high strength and high conductivity (or thermal conductivity) as basic characteristics. Required. In recent years, high integration, miniaturization, and thinning of electronic components have been rapidly progressing, and the level of demand for copper alloys used in electronic device components has been increased accordingly.

  From the viewpoint of high strength and high conductivity, in recent years, the amount of precipitation hardening type copper alloys has increased in place of conventional solid solution strengthened copper alloys such as phosphor bronze and brass as copper alloys for electronic materials. ing. In precipitation-hardened copper alloys, by aging the supersaturated solid solution that has undergone solution treatment, fine precipitates are uniformly dispersed, increasing the strength of the alloy and reducing the amount of solid solution elements in the copper. Electrical conductivity is improved. For this reason, a material excellent in mechanical properties such as strength and spring property and having good electrical conductivity and thermal conductivity can be obtained.

  Among precipitation hardening copper alloys, Cu-Ni-Si copper alloys, commonly called Corson alloys, are representative copper alloys that have relatively high electrical conductivity, strength, stress relaxation characteristics and bending workability. Is one of the alloys that is currently under active development. In this copper alloy, strength and conductivity can be improved by precipitating fine Ni—Si intermetallic compound particles in a copper matrix.

The precipitate of Ni—Si-based intermetallic compound particles is generally configured with a stoichiometric composition. For example, in Patent Document 1, the mass ratio of Ni and Si in an alloy is set to the mass composition of Ni ₂ Si, which is an intermetallic compound. It is described that good electrical conductivity can be obtained by approaching the ratio (Ni atomic weight × 2: Si atomic weight × 1), that is, by setting the weight concentration ratio of Ni and Si to Ni / Si = 3-7. Has been.

However, as described in Patent Document 1, characteristics can be obtained by bringing the mass ratio of Ni and Si close to the mass composition ratio of Ni ₂ Si, which is an intermetallic compound (Ni atomic weight × 2: Si atomic weight × 1). Although improvement can be achieved, in reality, there is some decrease in conductivity due to excess Si.
Therefore, it is conceivable to increase the conductivity by adding an element that forms a compound with Si, such as Cr, and combining it with excess Si. Cr is one of the elements, and there is a Cr-containing Cu—Ni—Si alloy.

Examples of Cu—Ni—Si based alloys to which Cr is added as an alloy element include those described in Patent Document 2 and Patent Document 3.
In Patent Document 2, Ni: 1.5 to 4.0% by weight, Si: 0.35 to 1.0% by weight, and optionally at least one metal selected from the group of Zr, Cr, Sn: 0 When heating (or cooling) a Corson alloy consisting of 0.05 to 1.0% by weight, the balance being Cu and inevitable impurities, in the temperature range of 400 to 800 ° C., the tensile thermal strain of the Corson alloy is 1 × 10 ^The Corson alloy heat treatment method is characterized in that the Corson alloy is heated (or cooled) to be ^-4 or less. According to this method, it is said that ingot cracking during heat treatment can be prevented.

  In Patent Document 3, Ni: 2 to 5% by weight, Si: 0.5 to 1.5% by weight, Zn: 0.1 to 2% by weight, Mn: 0.01 to 0.1% by weight, Cr: 0.001 to 0.1 wt%, Al: 0.001 to 0.15 wt%, Co: 0.05 to 2 wt%, the content of S as an impurity component is regulated to 15 ppm or less, and the balance Describes a high-strength copper alloy having excellent bending workability, characterized by comprising Cu and inevitable impurities. According to this invention, Cr is said to be an element that strengthens the grain boundary of the ingot and enhances hot workability. Further, when Cr is contained exceeding 0.1% by weight, the molten metal is oxidized and castability is deteriorated. In addition, it is described that the copper alloy is melt cast by coating charcoal in the atmosphere in a kryptor furnace.

Patent Document 4 is cited from the viewpoint of a compound of Cr and Si. In Patent Document 4, Cr: 0.1 to 0.25% by weight, Si: 0.005 to 0.1% by weight, Zn: 0.1 to 0.5% by weight, Sn: 0.05 to 0. In a copper alloy containing 5% by weight and having a Cr to Si weight ratio of 3 to 25 and the balance being Cu and inevitable impurities, a CrSi compound having a size of 0.05 μm to 10 μm is 1 × in the copper matrix. Copper alloy for electronic equipment excellent in etching workability and punching workability which exists at a number density of 10 ^{3 to} 5 × 10 ⁵ pieces / mm ² and has a Cr compound (other than CrSi compound) having a size of 10 μm or less Is described with respect to the hot working temperature of the ingot and the aging heat treatment temperature. According to this method, it is said that both etching processability and press punchability can be suitably used.

JP 2001-207229 A Japanese Patent No. 2862942 Japanese Patent No. 3049137 JP-A-2005-113180

The demand for dramatic improvement in material characteristics in recent rapid integration and downsizing / thinning of electronic parts is the same for the Cr-containing Cu—Ni—Si alloy which is the alloy system of the present invention.
However, in Patent Document 1, Cr is not added, and in reality, some decrease in conductivity is observed due to excessive Ni and Si, and the characteristics have not been dramatically improved. In Patent Document 2 and Patent Document 3, Cr is added to the Cu—Ni—Si-based alloy. However, Patent Document 2 aims to enhance the solid solution by adding, and Patent Document 3 aims to improve hot workability. Therefore, there is no description regarding the Cr—Si compound which is the key of the present invention. Therefore, the solution means of the problem to be solved by the present invention is not easily assumed from these patent documents.

Patent Document 4 describes that etching processability and punching processability are improved by controlling the number density and size of the CrSi compound, but considering the formation of the Ni-Si compound because Ni is not added. However, it is sufficient to consider only the conditions for forming the Cr—Si compound, and it does not easily assume the solution of the problem to be solved by the present invention.
Accordingly, an object of the present invention is to provide a Corson alloy having a high strength and high conductivity by dramatically improving the characteristics by better exhibiting the effect of Cr addition in the Cu-Ni-Si alloy. is there.

  As a result of intensive studies to solve the above problems, the present inventors have found the following inventions. In a Cu-Ni-Si-based alloy, the composition is such that Si is excessive with respect to Ni, and Ni silicide corresponding to Ni addition is surely precipitated to increase the strength, while the compound with Cr added with excess Si is added. To increase the conductivity. An important point of the present invention is to control the growth of the Cr—Si compound so that the combination of Cr and Si grows too much and the Si to be combined with Ni is not insufficient. Specifically, the present inventor has focused on the composition, size, and number density of the Cr—Si compound, and found out that the effect can be better achieved by controlling the temperature and cooling rate of the heat treatment process. It was.

That is, the present invention contains (1) Ni: 1.0-4.5 mass%, Si: 0.50-1.2 mass%, Cr: 0.003-0.3 mass% (provided that Ni The weight ratio of Si and Si is 3 ≦ Ni / Si ≦ 5.5.), A copper alloy for electronic materials composed of the balance Cu and inevitable impurities, and the size dispersed in the material is 0.1 μm A copper alloy for electronic materials having an atomic concentration ratio of Cr to Si in the dispersed particles of 1 to 10 ⁶ / mm ² with a dispersion density of 1 × 10 ⁶ pieces / mm ² or less of a Cr—Si compound of ˜5 μm.
(2) The copper alloy for electronic materials according to claim 1, wherein the dispersion density of the Cr—Si compound having a size of 0.1 μm to 5 μm is higher than 1 × 10 ⁴ pieces / mm ² .
(3) The copper alloy for electronic materials according to (1) or (2), further containing 0.05 to 2.0% by mass of one or more selected from Sn and Zn.
(4) Further, 0.001 to 2.0% by mass of one or more selected from Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al, Co, and Fe The copper alloy for electronic materials according to any one of (1) to (3).
(5) A rolled copper product using the copper alloy according to any one of (1) to (4).
(6) Electronic device parts using the copper alloy according to any one of (1) to (4).
It is.

  According to the present invention, since the effect of addition of Cr, which is an alloy element, is better exhibited, a Corson-based copper alloy for electronic materials with significantly improved strength and electrical conductivity can be obtained.

Addition amounts of Ni and Si Ni and Si form Ni silicide (Ni ₂ Si or the like) as an intermetallic compound by performing an appropriate heat treatment, and can increase the strength without deteriorating conductivity. As described above, the mass ratio of Si and Ni is preferably 3 ≦ Ni / Si ≦ 5.5 close to the stoichiometric composition, and more preferably 3.5 ≦ Ni / Si ≦ 5.0.

  However, even if Ni / Si has a ratio within the above range, the desired strength cannot be obtained if the amount of Si added is less than 0.5% by mass. The rate is remarkably lowered, and further, a liquid phase is generated at the segregation part and the hot workability is lowered. Therefore, Si may be 0.5 to 1.2% by mass, and preferably 0.5 to 0.8% by mass. The addition amount of Ni may be set so as to satisfy the above-mentioned preferable ratio according to the addition amount of Si, and Ni: 2.5 to 4.5% by mass is preferable in order to balance the addition amount of Si, preferably Ni: 3.2 to 4.2% by mass, more preferably Ni: 3.5 to 4.0% by mass.

Addition amount of Cr In a normal Cu—Ni—Si based alloy, when the Ni—Si concentration is increased, the total number of precipitated particles increases, so that the strength can be increased by precipitation strengthening. On the other hand, as the additive concentration increases, the amount of solid solution that does not contribute to precipitation also increases, so the conductivity decreases, and eventually the peak intensity of aging precipitation increases, but the conductivity that becomes the peak intensity decreases. However, when Cr is added to the Cu—Ni—Si based alloy in an amount of 0.003 to 0.3% by mass, preferably 0.01 to 0.1% by mass, Cu having the same Ni—Si concentration in the final characteristics. The electrical conductivity can be increased without impairing the strength as compared with the -Ni-Si alloy, and the hot workability is improved and the yield is increased.

The composition of particles precipitated when Cr is added to a Cu—Ni—Si based alloy tends to precipitate single particles of bcc structure mainly composed of Cr, but also a compound with Si. Cr can easily precipitate chromium silicide (Cr ₃ Si, etc.), which is a compound with Si, in a copper matrix by appropriate heat treatment, so it combines solution treatment, cold rolling, and aging treatment. Thus, a solid solution Si component that did not precipitate as Ni ₂ Si or the like in the process of creating alloy characteristics can be precipitated as a Cr—Si compound. For this reason, the fall of the electrical conductivity by solid solution Si can be suppressed, and the raise of electrical conductivity can be aimed at without impairing intensity | strength.

  At this time, if the Si concentration in the Cr particles is low, Si remains in the parent phase, and thus the conductivity is reduced. On the other hand, if the Si concentration in the Cr particles is high, the Si concentration for precipitating the Ni—Si particles is reduced. Therefore, the strength decreases. Furthermore, when the Si concentration in Cr is high, coarse Cr—Si compounds increase, and bending, fatigue strength, and the like deteriorate. Furthermore, even if the cooling rate after solution heat treatment is slowed down or the aging heat treatment time is excessively extended, the Cr concentration of the Cr-Si compound is increased and the Si concentration forming the Ni-Si compound is reduced, contributing to strengthening. Ni-Si compound to be used is insufficient. This is because the diffusion rate of Si and Cr in Cu is faster than that of Ni, so that the Cr—Si compound is easily coarsened, and the precipitation rate of the Cr—Si compound is 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 solution treatment and avoiding conditions that are higher in temperature and longer than the aging conditions that provide maximum strength. Therefore, the Cr concentration is set to 0.003 mass% or more and 0.3 mass%, and the atomic concentration ratio of Cr to Si in the Cr—Si compound is set to 1 to 5.

  In addition, Cr preferentially precipitates at the crystal grain boundaries during the cooling process during melt casting, so that the grain boundaries can be strengthened, cracks during hot working are less likely to occur, and yield reduction can be suppressed. That is, Cr that has precipitated at the grain boundaries during melt casting re-dissolves by solution treatment or the like, but produces silicide during subsequent aging precipitation. In a normal Cu—Ni—Si based alloy, Si that does not contribute to aging precipitation suppresses the increase in conductivity while being dissolved in the matrix, but the silicide forming element Cr is not added. By adding and precipitating silicide further, the amount of solid solution Si can be reduced as compared with the conventional Cu-Ni-Si alloy, and the conductivity can be increased without impairing the strength.

The size of the Cr—Si compound and the dispersion density The size of the Cr—Si compound affects the bending workability, fatigue strength, etc., which exceeds 5 μm, or the dispersion of the Cr—Si compound of 0.1 to 5 μm. When the density exceeds 1 × 10 ⁶ pieces / mm ² , bending workability and fatigue strength are remarkably deteriorated. Furthermore, since the number density affects the excess or deficiency of the Si concentration in the matrix, desired strength characteristics cannot be obtained in a state where a large number of large particles are dispersed. Therefore, the upper limit of the dispersion density may be 1 × 10 ⁶ pieces / mm ² or less, preferably 5 × 10 ⁵ pieces / mm ² or less, more preferably 1 × 10 ⁵ pieces / mm ² or less. Moreover, since the improvement effect by the addition of Cr in the case of 1 × 10 ⁴ pieces / mm ² or less is small, it is desirable to exceed this.

Sn and Zn
By adding 0.05% to 2.0% by mass of one or more selected from Sn and Zn to the Cu—Ni—Si based alloy according to the present invention in a total amount, the strength and conductivity are not significantly impaired. Stress relaxation characteristics can be improved. If the amount added is less than 0.05% by mass, the effect is insufficient, and if it exceeds 2.0% by mass, the manufacturability such as castability and hot workability, and the electrical conductivity of the product are impaired, so 0.05-2. It is preferable to add 0% by mass.

Other additive elements Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al, Co, and Fe show various effects, but complement each other, strength, The Cu-Ni-Si alloy according to the present invention has an effect of improving not only electrical conductivity but also productivity such as bending workability, plating workability and improvement of hot workability by refining the ingot structure. Depending on the properties for which one or more of these are required, the total amount can be added as 2.0% by mass or less as appropriate. If the total amount of these elements is less than 0.001% by mass, the desired effect cannot be obtained. If the total amount exceeds 2.0% by mass, the decrease in conductivity and the deterioration of manufacturability become significant. It is preferable to set it as 0.001-2.0 mass% by weight, and it is more preferable to set it as 0.01-1.0 mass%.
In addition, elements not specifically described in the present specification may be added as long as the characteristics of the Cu—Ni—Si alloy according to the present invention are not adversely affected.

  Next, the manufacturing method of the present invention will be described. The Cu—Ni—Si based alloy according to the present invention is obtained by a conventional method for producing a Cu—Ni—Si based alloy, except for the conditions of solution treatment and aging treatment for controlling the Ni—Si compound and the Cr—Si compound. Although it is possible to manufacture and a person skilled in the art can select an optimal manufacturing method according to the composition and required characteristics, it is considered that no special explanation is required. A method will be described.

  First, using an air melting furnace, raw materials such as electrolytic copper, Ni, Si, and Cr are melted to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. Thereafter, hot rolling is performed, and cold rolling and heat treatment are repeated to finish a strip or foil having a desired thickness and characteristics. Heat treatment includes solution treatment and aging treatment. In the solution treatment, heating is performed at a high temperature of 700 to 1000 ° C. to solid-dissolve the Ni—Si compound or Cr—Si compound in the Cu matrix, and at the same time, the Cu matrix is recrystallized. The solution treatment may be combined with hot rolling.

  In this solution treatment, the cooling rate is important as well as the heating temperature. Conventionally, since the cooling rate after heating has not been controlled, a water tank is provided on the exit side of the heating furnace for water cooling or air cooling in an air atmosphere has been adopted. In this case, the cooling rate easily fluctuates depending on the heating temperature setting, and the conventional cooling rate fluctuates in the range of 1 ° C./second or less to 10 ° C./second or more. Therefore, it is difficult to control the characteristics of the alloy system as in the present invention example.

  The cooling rate is desirably in the range of 1 ° C./second to 10 ° C./second. In the aging treatment, heating is performed for 1 hour or more in a temperature range of 350 to 550 ° C., typically 3 to 24 hours, and Ni and Si compounds and Cr and Si compounds dissolved in the solution treatment are precipitated as fine particles. . This aging treatment increases strength and conductivity. In order to obtain higher strength, cold rolling may be performed before and / or after aging. Moreover, when performing cold rolling after aging, strain relief annealing (low temperature annealing) may be performed after cold rolling.

  In one embodiment, the Cu—Ni—Si based copper alloy according to the present invention can have a 0.2% yield strength of 780 MPa or more and a conductivity of 45% IACS or more, and further a 0.2% yield strength of 860 MPa. In addition, the electrical conductivity can be 43% IACS or higher, and the 0.2% proof stress can be 890 MPa or higher and the electrical conductivity can be 40% IACS or higher.

  The Cu—Ni—Si based alloy according to the present invention can be processed into various copper products, such as plates, strips, tubes, bars and wires, and the Cu—Ni—Si based copper alloy according to the present invention is It can be used for electronic equipment parts such as lead frames, connectors, pins, terminals, relays, switches, and secondary battery foil materials that require both high strength and high electrical conductivity (or thermal conductivity). it can.

  Specific examples of the present invention are shown below, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention.

  As shown in Table 1, 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 in which some contents of Ni, Si, and Cr are changed. Have Moreover, the copper alloy used for a comparative example is a Cu-Ni-Si type | system | group alloy with a parameter outside the range of this invention, respectively.

  Copper alloys having various component compositions shown in Table 1 were melted at 1300 ° C. in a high-frequency melting furnace and cast into an ingot having a thickness of 30 mm. Next, the ingot was heated at 1000 ° C., then hot-rolled to a plate thickness of 10 mm, and quickly cooled. After surface chamfering to a thickness of 8 mm for removing scale on the surface, a plate having a thickness of 0.2 mm was formed by cold rolling. Next, the solution treatment was held in an Ar gas atmosphere at 800 to 900 ° C. for 120 seconds in accordance with the addition amounts of Ni and Cr, and then cooled to room temperature by changing the cooling rate. The cooling rate was controlled by changing the flow rate of the gas blown to the heated sample, and the cooling time was measured by measuring the time to cool the sample from the highest temperature reached to 400 ° C. The furnace cooling rate when the gas was not blown was 5 ° C./s, and the cooling rate was 1 ° C./s when the temperature was lowered while controlling the heating output as an example of further decreasing the cooling rate. Thereafter, the sample was cold-rolled to 0.1 mm, and finally subjected to aging treatment in an inert atmosphere at 400 to 550 ° C. for 1 to 12 hours according to the amount added to produce a sample.

The characteristics of strength and conductivity were evaluated for each alloy thus obtained. The strength was determined by performing a tensile test in the rolling parallel direction to measure 0.2% yield strength (YS; MPa), and the conductivity (EC;% IACS) was determined by volume resistivity measurement using a W bridge.
The bendability was evaluated by performing 90 ° bending using a W-shaped mold under the condition that the ratio of the sample plate thickness to the bending radius was 1. In the evaluation, the surface of the bent portion was observed with an optical microscope, and when the crack was not observed, it was judged that there was no problem in practical use, and the case where the crack was recognized was made x. In the fatigue test, a swing stress was applied according to JIS Z 2273, and the stress (MPa) at which the number of repetitions until breakage was 10 ⁷ was obtained.

The observation of the Cr—Si compound is based on the FE-AES observation after electropolishing the plate surface of the material, and the particles having a size of 0.1 μm or more are actually targeted at many locations. Sputtering with Ar ⁺ is performed to measure the Auger spectrum of each particle, and when the detected element is converted into weight concentration as a semi-quantitative value by the sensitivity coefficient method, the particles in which Cr and Si are detected are targeted. did. The “composition”, “size”, and “dispersion density” of the Cr—Si compound are the average composition of the 0.1 to 5 μm size Cr-Si particles analyzed at a number of locations under FE-AES observation, the diameter of the minimum circle, It was set as the average number in the observation visual field.
Tables 1 and 2 show the results.

In Invention Examples 1 to 25, the dispersion density of 1 × 10 ⁶ or less and the Cr-Si compound appropriate cooling rate, because Cr / Si is in the range of 1 to 5, and satisfactory characteristics were obtained.
On the other hand, in Comparative Examples 1 to 3, since the cooling rate was slow, the Cr—Si compound grew too much to obtain sufficient strength, and the bending workability was also poor.
In Comparative Examples 4 and 5, since the cooling rate was fast, it did not grow and excessive Si was dissolved in the alloy, resulting in poor strength and electrical conductivity. In Comparative Examples 6 and 7, since the aging temperature was high, the Cr—Si compound grew too much to obtain sufficient strength, and the bending workability was also poor. In Comparative Examples 8 and 9, since the Cr concentration was too high, the Cr—Si compound grew too much to obtain sufficient strength, and the bending workability was also poor.

Claims (6)

Ni: 1.0-4.5 mass%, Si: 0.50-1.2 mass%, Cr: 0.003-0.3 mass% (however, the weight ratio of Ni and Si is 3 ≦ Ni / Si ≦ 5.5), a copper alloy for electronic materials composed of the balance Cu and inevitable impurities, and a Cr—Si compound having a size of 0.1 μm to 5 μm dispersed in the material A copper alloy for electronic materials having an atomic concentration ratio of Cr to Si in the dispersed particles of 1 to 5 and a dispersion density of 1 × 10 ⁶ pieces / mm ² or less. The copper alloy for electronic materials according to claim 1, wherein the dispersion density of the Cr—Si compound having a size of 0.1 μm to 5 μm is higher than 1 × 10 ⁴ pieces / mm ² .   Furthermore, the copper alloy for electronic materials of Claim 1 or 2 which contains 0.05-2.0 mass% of 1 type, or 2 or more types selected from Sn and Zn.   Furthermore, 0.001-2.0 mass% of 1 type (s) or 2 or more types selected from Mg, Mn, Ag, P, As, Sb, Be, B, Ti, Zr, Al, Co, and Fe is contained. The copper alloy for electronic materials as described in any one of 1-3.   The copper-stretched product using the copper alloy as described in any one of Claims 1-4.   The electronic device component using the copper alloy as described in any one of Claims 1-4.