JP2016183418A - Cu-Ni-Si-Co-BASED COPPER ALLOY FOR ELECTRONIC MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-Ni-Si-Co-based copper alloy with improved balance of conductivity, strength and flexure processability.SOLUTION: There is provided a copper alloy for electronic material containing Ni:1.0 to 2.5 mass%, Co:0.5 to 2.5 mass%, Si:0.3 to 1.2 mass% and the balance Cu with inevitable impurities, and having a ratio of the total mass concentration of Ni and Co to the mass concentration of Si, [Ni+Co]/Si, of 3.5≤[Ni+Co]/Si≤5.5, average particle diameter of second particles with particle diameter in a range of 1 to 50 nm on a cross section parallel to a rolling direction of 2 to 15 nm and average distance of the second particles each other of 10 to 50 nm.SELECTED DRAWING: None

Description

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

  Copper alloys for electronic materials used in various electronic parts such as connectors, switches, relays, pins, terminals, and lead frames are required to have both high strength and high conductivity (or thermal conductivity) as basic characteristics. Is done. In recent years, high integration and miniaturization / 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, the amount of precipitation hardening type copper alloys is increasing instead of conventional solid solution strengthened copper alloys such as phosphor bronze and brass as copper alloys for electronic materials. . 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, and bending workability, and are currently active in the industry. It is one of the alloys being developed. In this copper alloy, strength and electrical conductivity are improved by precipitating fine Ni—Si intermetallic compound particles in a copper matrix.

Recently, a Cu-Ni-Si-Co-based alloy obtained by adding Co to a Cu-Ni-Si-based copper alloy has attracted attention, and technical improvements are being promoted. In JP 2009-242890 A (Patent Document 1), in order to improve the strength, conductivity and spring limit value of the Cu—Ni—Si—Co alloy, the second phase having a particle diameter of 0.1 to 1 μm. An invention is described in which the number density of particles is controlled from 5 × 10 ⁵ to 1 × 10 ⁷ particles / mm ² .
As a method for producing the copper alloy described in the document,
-Step 1 of melt casting an ingot having a desired composition;
Hot rolling is performed after heating at −950 ° C. or higher and 1050 ° C. or lower for 1 hour or longer. The temperature at the end of hot rolling is 850 ° C. or higher, and the average cooling rate from 850 ° C. to 400 ° C. is 15 ° C./s or higher. Step 2 to perform,
-Cold rolling process 3;
Solution treatment is performed at −850 ° C. or more and 1050 ° C. or less, and the average cooling rate until the material temperature is reduced to 650 ° C. is reduced to 1 ° C./s or more and less than 15 ° C./s, and the temperature is decreased from 650 ° C. to 400 ° C. Step 4 for cooling at an average cooling rate of 15 ° C./s or more,
A first aging treatment step 5 performed at −425 ° C. or more and less than 475 ° C. for 1 to 24 hours;
-Cold rolling process 6;
A second aging treatment step 5 carried out at -100 ° C or higher and lower than 350 ° C for 1 to 48 hours;
A manufacturing method including sequentially performing the above is disclosed.

  In Japanese translations of PCT publication No. 2005-532477 (patent document 2), each annealing in the manufacturing process of a Cu-Ni-Si-Co-based alloy can be a stepwise annealing process, and typically in stepwise annealing. It is described that the first step is at a higher temperature than the second step, and stepped annealing can result in a better combination of strength and conductivity than annealing at a constant temperature.

JP 2009-242890 A JP 2005-532477 A

Although various improvements in the properties of Cu-Ni-Si-Co alloys have been proposed in this way, the optimum aging conditions have not been established, and there is still room for improvement in the precipitation state of the second phase particles. Has been. Japanese Patent Application Laid-Open No. 2009-242890 discloses that the number density of second phase particles having a particle size of 0.1 to 1 μm is 5 × 10 ⁵ to 1 × 10 ⁷ in order to improve strength, conductivity, and spring limit value. Although the invention controlled at / mm ² is described, the second phase particles of 50 nm or less are not mentioned at all. Although Patent Document 2 proposes stepwise annealing, the specific conditions are not shown at all.

  Then, this invention makes it a subject to provide the Cu-Ni-Si-Co type | system | group alloy by which the balance of electroconductivity, intensity | strength, and bending workability was improved by improving the precipitation state of a 2nd phase particle. To do.

  As a result of intensive studies on the relationship between the distribution of ultrafine second phase particles of about 1 to 50 nm at a magnification of 1 million and alloy properties using a transmission electron microscope (TEM), the present inventor It was found that the fine particle size of the second phase particles and the distance between the second phase particles significantly affect the alloy properties. And by controlling the average particle diameter of the second phase particles and the average distance between the second phase particles by an appropriate aging treatment, the conductivity, strength, and bending workability in the Cu-Ni-Si-Co-based alloy are controlled. It was found that the balance was improved.

  In one aspect, the present invention completed based on the above knowledge is as follows: Ni: 1.0 to 2.5 mass%, Co: 0.5 to 2.5 mass%, Si: 0.3 to 1.2 mass% The balance consists of Cu and inevitable impurities, the ratio of the total mass concentration of Ni and Co to the mass concentration of Si [Ni + Co] / Si is 3.5 ≦ [Ni + Co] /Si≦5.5, Electrons in which the average particle size of the second phase particles in the range of 1 to 50 nm in the cross section parallel to the rolling direction is 2 to 15 nm, and the average distance between the second phase particles is 10 to 50 nm It is a copper alloy for materials.

  In one embodiment, the copper alloy for electronic materials according to the present invention has an average crystal grain size of 3 to 30 μm in a cross section parallel to the rolling direction.

  In yet another embodiment, the copper alloy according to the present invention is further selected from the group of Cr, Sn, Zn, P, Mg, Mn, Ag, As, Sb, Be, B, Ti, Zr, Al, and Fe. At least one kind is contained in a maximum of 2.0% by mass in total.

  In yet another embodiment, the copper alloy according to the present invention has a 0.2% yield strength (YS) of 750 to 950 MPa.

In yet another embodiment, the copper alloy according to the present invention has any of the following characteristics (1) to (3).
(1) 0.2% yield strength (YS) is 750 to 800 MPa, and conductivity is 50 to 55% IACS.
(2) 0.2% yield strength (YS) is 800 to 850 MPa, and conductivity is 45 to 50% IACS.
(3) 0.2% proof stress (YS) is 850 to 900 MPa and conductivity is 40 to 45% IACS.

  In another aspect, the present invention is a copper drawn product made of the copper alloy according to the present invention.

  In still another aspect, the present invention is an electronic component including the copper alloy according to the present invention.

  According to the present invention, there is provided a Cu—Ni—Si—Co based alloy having an improved balance of strength, conductivity, and bending workability.

Invention Example No. manufactured by one-stage aging treatment 1-18 and Comparative Example No. It is the figure which plotted the relationship between electrical conductivity (EC) and 0.2% yield strength (YS) about 32-43. Invention Example No. manufactured by two-stage aging treatment 19-25 and Comparative Example No. It is the figure which plotted the relationship between electrical conductivity (EC) and 0.2% yield strength (YS) about 44-45. Invention Example No. manufactured by three-stage aging treatment 26-31 and Comparative Example No. It is the figure which plotted the relationship between electrical conductivity (EC) and 0.2% yield strength (YS) about 46-47. The boundary line of the favorable conditions for aging treatment was graphed with the x-axis being the material holding temperature (° C.) and the y-axis being the holding time (h) at the holding temperature.

Addition amounts of Ni, Co, and Si Ni, Co, and Si form an intermetallic compound by performing an appropriate heat treatment, and can increase the strength without deteriorating conductivity.
When the addition amounts of Ni, Co and Si are less than Ni: 1.0% by mass, Co: less than 0.5% by mass, and Si: less than 0.3% by mass, the desired strength cannot be obtained. If it exceeds 2.5% by mass, Co: more than 2.5% by mass, and Si: more than 1.2% by mass, the strength can be increased, but the electrical conductivity is remarkably lowered, and the hot workability is further deteriorated. Therefore, the addition amounts of Ni, Co, and Si were set to Ni: 1.0 to 2.5 mass%, Co: 0.5 to 2.5 mass%, and Si: 0.3 to 1.2 mass%. The addition amounts of Ni, Co and Si are preferably Ni: 1.5 to 2.0 mass%, Co: 0.7 to 2.0 mass%, and Si: 0.5 to 1.0 mass%.

Moreover, if the ratio [Ni + Co] / Si of the total mass concentration of Ni and Co with respect to the mass concentration of Si is too low, that is, if the ratio of Si to Ni and Co is too high, the conductivity will be increased by solute Si. In the annealing process, an oxide film of SiO ₂ is formed on the material surface layer and the solderability is deteriorated. On the other hand, if the ratio of Ni and Co to Si is too high, the Si required for silicide formation is insufficient and it is difficult to obtain high strength.
Therefore, the [Ni + Co] / Si ratio in the alloy composition is preferably controlled in the range of 3.5 ≦ [Ni + Co] /Si≦5.5, and the range of 4.0 ≦ [Ni + Co] /Si≦5.0. More preferably, it is controlled.

The added amount Cr of Cr preferentially precipitates at the grain boundaries in 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 is re-dissolved by solution treatment or the like, but during subsequent aging precipitation, precipitated particles having a bcc structure mainly composed of Cr or a compound with Si are generated. 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 further depositing silicide, the amount of dissolved Si can be reduced, and the conductivity can be increased without impairing the strength. However, if the Cr concentration exceeds 0.5% by mass, especially 2.0% by mass, coarse second-phase particles are easily formed, which impairs product characteristics. Therefore, Cr can be added up to 2.0 mass% at maximum in the Cu—Ni—Si—Co alloy according to the present invention. However, since the effect is small if it is less than 0.03 mass%, it is preferable to add 0.03-0.5 mass%, more preferably 0.09-0.3 mass%.

Addition amounts of Mg, Mn, Ag and P Mg, Mn, Ag and P improve the product properties such as strength and stress relaxation characteristics without adding a small amount of addition by adding a small amount. The effect of addition is exhibited mainly by solid solution in the matrix phase, but further effects can be exhibited by inclusion in the second phase particles. However, if the total concentration of Mg, Mn, Ag, and P exceeds 0.5% by mass, particularly 2.0% by mass, the effect of improving characteristics is saturated and manufacturability is impaired. Therefore, in the Cu—Ni—Si—Co alloy according to the present invention, a total of one or more selected from Mg, Mn, Ag and P is 2.0% by mass in total, preferably 1. 5% by mass can be added. However, since the effect is small if it is less than 0.01% by mass, it is preferable to add 0.01 to 1.0% by mass in total, more preferably 0.04 to 0.5% by mass in total.

Even in the addition amounts Sn and Zn of Sn and Zn, the addition of a small amount improves product properties such as strength, stress relaxation properties, and plating properties without impairing electrical conductivity. The effect of addition is exhibited mainly by solid solution in the matrix. However, if the total amount of Sn and Zn exceeds 2.0% by mass, the effect of improving characteristics is saturated and manufacturability is impaired. Therefore, one or two selected from Sn and Zn can be added to the Cu—Ni—Si—Co-based alloy according to the present invention in a maximum of 2.0 mass% in total. However, since the effect is small if it is less than 0.05% by mass, it is preferable to add 0.05 to 2.0% by mass in total, and more preferably 0.5 to 1.0% by mass in total.

Addition amounts of As, Sb, Be, B, Ti, Zr, Al, and Fe As, Sb, Be, B, Ti, Zr, Al, and Fe are also adjusted according to required product characteristics. This improves product properties such as conductivity, strength, stress relaxation properties, and plating properties. The effect of addition is exhibited mainly by solid solution in the parent phase, but it can also be exhibited by forming the second phase particles having a new composition or contained in the second phase particles. However, if the total amount of these elements exceeds 2.0% by mass, the effect of improving characteristics is saturated and manufacturability is impaired. Therefore, in the Cu—Ni—Si—Co alloy according to the present invention, a total of one or more selected from As, Sb, Be, B, Ti, Zr, Al and Fe is 2.0 at the maximum. Mass% can be added. However, since the effect is small if it is less than 0.001% by mass, it is preferable to add 0.001-2.0% by mass in total, more preferably 0.05-1.0% by mass in total.

  Manufacturability is likely to be impaired when the total amount of Cr, Sn, Zn, P, Mg, Mn, Ag, As, Sb, Be, B, Ti, Zr, Al, and Fe exceeds 2.0% by mass. Therefore, preferably the total of these is 2.0% by mass or less, more preferably 1.5% by mass or less.

(Second phase particles)
In the present invention, the second phase particle mainly refers to silicide, but is not limited to this. Crystallized substances generated in the solidification process of melt casting and precipitates generated in the subsequent cooling process, after hot rolling It refers to precipitates generated in the cooling process, precipitates generated in the cooling process after solution treatment, and precipitates generated in the aging process.

  In the present invention, attention is focused on second phase particles having a particle diameter in the range of 1 to 50 nm in a cross section parallel to the rolling direction, and the average particle diameter and the average distance between the particles are defined. By controlling the particle diameter of such ultrafine second phase particles and the distance between the second phase particles, the alloy characteristics are improved.

Specifically, the average particle diameter of the second phase particles having a particle diameter in the range of 1 to 50 nm in a cross section parallel to the rolling direction tends to fail to obtain sufficient strength, and conversely is too small. There is a tendency that sufficient conductivity cannot be obtained. Therefore, the average particle size is preferably controlled to 2 to 15 nm, more preferably 5 to 10 nm.
It is also important to control not only the average particle diameter but also the average distance between the second phase particles. When the average distance between the second phase particles is reduced, high strength is obtained, and the average distance between the second phase particles is preferably 50 nm or less, and more preferably 30 nm or less. The lower limit is 10 nm from the amount of additive element that can be precipitated and the diameter of the precipitate.

In the present invention, the average particle size of the second phase particles is measured by the following procedure. Photographed with a transmission electron microscope at a magnification of 1,000,000 so that 100 or more second phase particles of 1 to 50 nm are contained, the major axis of each particle was measured, and the value obtained by dividing the total by the number of particles was the average particle size. To do. The major axis means the length of a line segment connecting two farthest points on the particle outline in each second phase particle in the observation field.
In the present invention, the average distance between the second phase particles is measured by the following procedure. Photographed with a transmission electron microscope so that 100 or more second phase particles of 1 to 50 nm are included at 1 million times, and (observation area × sample thickness) ÷ number of second phase particles in observation field is 1/3 power Is required.

(Crystal grain size)
The crystal grains affect the strength, and the Hall Petch rule that the strength is proportional to the −1/2 power of the crystal grains generally holds, so that the crystal grains are preferably smaller. However, in the precipitation strengthening type alloy, it is necessary to pay attention to the precipitation state of the second phase particles. In the aging treatment, the second phase particles precipitated in the crystal grains contribute to the strength improvement, but the second phase particles precipitated in the crystal grain boundaries hardly contribute to the strength improvement. Therefore, the smaller the crystal grain, the higher the rate of grain boundary reaction in the precipitation reaction, so the grain boundary precipitation that does not contribute to strength improvement becomes dominant, and when the crystal grain size is less than 3 μm, the desired strength can be obtained. Can not. On the other hand, coarse crystal grains reduce bending workability.
Therefore, from the viewpoint of obtaining desired strength and bending workability, it is preferable that the average crystal grain size in a cross section parallel to the rolling direction is 3 to 30 μm. Furthermore, the average crystal grain size is more preferably controlled to 10 to 25 μm from the viewpoint of achieving both high strength and good bending workability.

(Strength, conductivity and bendability)
In one embodiment, the Cu—Ni—Si—Co alloy according to the present invention has a 0.2% yield strength (YS) of 750 to 950 MPa. In a typical embodiment, the Cu—Ni—Si—Co based alloy according to the present invention may have a 0.2% proof stress (YS) of 750 to 800 MPa and a conductivity of 50 to 55% IACS. In another exemplary embodiment, the 0.2% proof stress (YS) can be 800-850 MPa and the conductivity can be 45-50% IACS. In yet another exemplary embodiment, The 0.2% proof stress (YS) can be 850 to 900 MPa and the conductivity can be 40 to 45% IACS.

(Production method)
Next, a method for producing a copper alloy according to the present invention will be described.
The copper alloy according to the present invention can be manufactured by adopting the manufacturing process of the Corson alloy except that some processes are devised.

In a general manufacturing process of a Corson copper alloy, first, an atmospheric melting furnace is used to melt raw materials such as electrolytic copper, Ni, Si, Co, etc. 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 about 850 to about 1000 ° C., so that the second phase particles are dissolved in the Cu matrix, and at the same time, the Cu matrix is recrystallized. The solution treatment may be combined with hot rolling. In the aging treatment, the second phase particles heated in a temperature range of about 350 to about 550 ° C. for 1 hour or more and solid-dissolved by the solution treatment are precipitated as fine particles of nanometer order. 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.
Between the above steps, grinding, polishing, shot blast pickling and the like for removing oxide scale on the surface are appropriately performed.

  It is necessary to pay attention to the following points when manufacturing the copper alloy according to the present invention with respect to the conventional manufacturing process.

  First, coarse crystallized products are inevitably generated during the solidification process during casting, and coarse precipitates are inevitably generated during the cooling process, so it is necessary to dissolve these second-phase particles in the matrix during the subsequent steps. There is. It is desirable to perform hot rolling after holding at 950 ° C. to 1050 ° C. for 1 hour or longer, and cool rapidly after the hot rolling is finished.

  After hot rolling, cold rolling and solution treatment are performed in this order. In the solution treatment, it is important to reduce the number of coarse second-phase particles by sufficient solid solution and to prevent coarsening of crystal grains. Specifically, the solution treatment temperature is set to 850 ° C. to 1050 ° C., and the second phase particles are dissolved. It is preferable that the cooling after the solution treatment is also fast, and specifically, it is desirable to set it to 10 ° C./sec or more.

  In addition, the appropriate time during which the material temperature is maintained at the maximum temperature is different depending on the Ni, Co and Si concentrations and the maximum temperature, but in order to prevent grain growth due to recrystallization and subsequent crystal grain growth. Typically, the time during which the material temperature is maintained at the maximum temperature is controlled to 480 seconds or less, preferably 240 seconds or less, and more preferably 120 seconds or less. However, since the number of coarse second-phase particles may not be reduced if the time during which the material temperature is maintained at the maximum temperature is too short, it is preferably 10 seconds or more, and 30 seconds or more. More preferably.

An aging treatment is performed after the solution treatment step. In producing the copper alloy according to the present invention, it is desirable to strictly control the conditions of the aging treatment. This is because the aging treatment has the greatest influence on the control of the distribution state of the second phase particles. Specific aging treatment conditions will be described below.
First, when the material temperature reaches the holding temperature from 300 ° C., if the temperature rises too high, the number of second phase particles tends to decrease because the number of precipitation sites is small, and the interparticle distance between the second phase particles tends to increase. . On the other hand, if it is too low, the second phase particles become larger during the temperature rise. Therefore, it is 10 to 160 ° C./h, preferably 10 to 100 ° C./h, more preferably 10 to 50 ° C./h. The temperature increase rate is given by (holding temperature−300 ° C.) / (Time required for the material temperature to rise from 300 ° C. to the holding temperature).
Next, when the retention temperature (° C.) of the material is x and the retention time (h) at the retention temperature is y, the following formula: 5.0 × 10 ¹⁴ × exp (−0.0745x) ≦ y ≦ 2. The holding temperature and holding time are set so as to satisfy 0 × 10 ¹⁷ × exp (−0.0745x). When y> 2.0 × 10 ¹⁷ × exp (−0.0745x), the second phase particles tend to grow too much and the average particle size tends to exceed 15 nm, and 5.0 × 10 ¹⁴ × exp (− When 0.0745x)> y, the growth of the second phase particles is insufficient and the average particle size tends to be less than 2 nm.
The aging treatment is preferably performed at a holding temperature and a holding time so as to satisfy the following formula: 8.0 × 10 ¹⁵ × exp (−0.0745x) ≦ y ≦ 5.0 × 10 ¹⁶ × exp (−0.0745x) Set. When the aging treatment is carried out under the conditions, the average particle diameter of the second phase particles tends to fall within 5 to 9 nm.
In FIG. 4, the above equation is represented in a graph with the x axis as the material holding temperature (° C.) and the y axis as the holding time (h) at the holding temperature.
Finally, an improvement in conductivity can be expected by lowering the rate of temperature drop when the material temperature decreases from the holding temperature to 300 ° C. However, when too low, strength will fall. Therefore, 5 to 100 ° C./h, preferably 5 to 50 ° C./h, more preferably 5 to 25 ° C./h. The temperature lowering rate is given by (holding temperature−300 ° C.) / (Time required for the material temperature to drop from the holding temperature to 300 ° C. after the start of temperature lowering).

In the aging treatment, better characteristics can be obtained by performing multi-stage aging.
As detailed conditions, after performing the first stage aging treatment under the above conditions, the temperature difference between the stages is 20 ° C. to 150 ° C., the holding time of each stage is 1 to 30 hours, and the multi-stage aging is performed toward the low temperature side. Is preferably performed.

  The temperature difference between the stages was set to 20 ° C. to 150 ° C. The reason is that if the temperature difference is less than 20 ° C., the second phase particles grow too much and the strength decreases, while if the temperature difference exceeds 150 ° C., precipitation occurs. This is because the speed is too slow and the effect is small. The temperature difference between the stages is preferably 30 to 120 ° C, more preferably 40 to 100 ° C. For example, when the first aging treatment is performed at 460 ° C., the second aging treatment can be performed at 310 to 440 ° C., which is a holding temperature lower by 20 to 150 ° C. The same applies to the third and subsequent stages. In addition, since the distribution state of the second phase particles hardly changes even when the aging treatment is performed at a holding temperature of less than 300 ° C., it is not necessary to set the number of stages of the aging treatment more than necessary. A suitable number of stages is two or three, and three is more preferable.

  The reason why the holding time of each stage is set to 1 to 30 h is that, if the holding time is less than 1 h, the effect cannot be obtained, while if it exceeds 30 h, the aging time becomes too long and the manufacturing cost increases. The holding time is preferably 2 to 20 hours, more preferably 5 to 15 hours.

  Although the temperature decreasing rate when the material temperature decreases from the holding temperature to 300 ° C. is described above, even when multi-stage aging is performed, it is preferable to perform at the same temperature decreasing rate when the material temperature is 300 ° C. or higher. . In the case of multi-stage aging, the temperature lowering rate is (first stage holding temperature−300 ° C.) / (The time required for the material temperature to drop from the holding temperature to 300 ° C. after starting the temperature lowering after the end of the first stage−each Retention time in the stage). That is, the temperature drop rate is calculated by subtracting the holding time in each stage from the temperature drop time.

  After the aging treatment, cold rolling is performed as necessary. The rolling degree is preferably 10 to 40%. After cold rolling, strain relief annealing is performed as necessary. The annealing temperature is preferably 300 to 600 ° C. and 5 seconds to 1 hour.

  The Cu—Ni—Si—Co based alloy of the present invention can be processed into various copper products, such as plates, strips, tubes, bars and wires, and the Cu—Ni—Si—Co based copper according to the present invention. The alloy can be used for electronic components such as lead frames, connectors, pins, terminals, relays, switches, and secondary battery foils.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

<Example 1>
A Cu—Ni—Si—Co based copper alloy having a composition of Ni, Co and Si having a mass concentration shown in Table 1 and having the balance consisting of Cu and unavoidable impurities in an Ar atmosphere using a high frequency melting furnace It was melted at 1300 ° C. and cast into an ingot having a thickness of 30 mm.
Next, this ingot was heated to 1000 ° C. and held for 3 hours, and then hot-rolled to a plate thickness of 10 mm. The material temperature at the end of hot rolling was 850 ° C. Then, it cooled with water.
Next, the first cold rolling was performed at a workability of 95% or more.
Next, in the solution treatment, when the Ni + Co concentration is 1.0 mass% or more and less than 2.0 mass%, the material temperature is 850 ° C., the heating time is 100 seconds, and the Ni + Co concentration is 2.0 mass% or more and 3.0 mass%. Less than mass%, material temperature is 900 ° C, heating time is 100 seconds, Ni + Co concentration is 3.0 mass% or more and less than 4.0 mass%, heating temperature is 950 ° C, heating time is 100 seconds. After that, it was cooled with water.
Next, an aging treatment was performed under the conditions described in Table 1.
Next, the second cold rolling was performed under the condition of a reduction rate of 20%, and a plate thickness of 0.08 mm was obtained.
Finally, strain relief annealing was carried out under conditions of a material temperature of 350 ° C. and a heating time of 30 seconds to obtain test pieces.

Various characteristics of the test pieces thus obtained were evaluated as follows.
(1) 0.2% yield strength (YS) and tensile strength (TS)
As for strength, a tensile test in the rolling parallel direction was performed according to JIS Z2241, and 0.2% yield strength (YS: MPa) and tensile strength (TS; MPa) were measured.
(2) Conductivity (EC)
The conductivity (EC;% IACS) was determined by volume resistivity measurement using a double bridge.
(3) Average crystal grain size (GS)
The test piece was resin-filled so that the observation surface had a cross section in the thickness direction parallel to the rolling direction, the observation surface was mirror-finished by mechanical polishing, and subsequently a mass concentration of 36% with respect to 100 parts by volume of water. In a solution mixed with 10 parts by volume of hydrochloric acid, ferric chloride having a weight of 5% with respect to the weight of the solution was dissolved. The sample was immersed in the resulting solution for 10 seconds to reveal the metal structure. Next, this metal structure was magnified 200 times with an optical microscope, and a photograph was taken in the range of an observation visual field of 0.5 mm ² . Subsequently, the average of the maximum diameter in the rolling direction and the maximum diameter in the thickness direction of each crystal grain is obtained for each crystal based on the photograph, the average value is calculated for each observation field, and further 15 observation fields Was the average crystal grain size.
(4) Bending workability As for the bending workability, the ratio of the sample plate thickness to the bending radius is 1 using a W-shaped mold as a W-bending test of Badway (the bending axis is the same direction as the rolling direction). 90 ° bending was performed under the conditions. Subsequently, the surface of the bent portion was observed with an optical microscope, and when no crack was observed, it was judged that there was no problem in practical use.
(5) Average particle diameter and average distance of second phase particles having a particle diameter in the range of 1 to 50 nm A sample for observation having a thickness of 10 to 100 nm by a twin jet electrolytic polishing apparatus using a part of each test piece Was measured using a transmission electron microscope (HITACHI-H-9000) according to the method described above. The average value of 10 fields of view was taken as the measured value.
In this embodiment, an electropolishing method generally used in the preparation of a transmission electron microscope sample is used, but measurement may be performed by forming a thin film by FIB (Focused Ion Beam).

The results are shown in Table 2. The results of each test piece will be described below.
No. 1 to 31 are invention examples, and the aging treatment conditions performed after the solution treatment were appropriate, and therefore, the balance of strength, conductivity, and bending workability was excellent. It can also be seen that this balance was further improved by increasing the number of stages of aging treatment.
On the other hand, no. No. 32 had a lower Ni concentration, Si concentration, and Co concentration, so the balance of characteristics was inferior to that of the inventive example.
No. In No. 33, since the temperature during the aging treatment was low, the growth of the second phase particles was insufficient and the average particle size was 2 nm or less. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 34, the time was short with respect to the temperature during the aging treatment, so that the growth of the second phase particles was insufficient, and the average particle size was 2 nm or less. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 35, since the time was long with respect to the temperature at the aging treatment, the second phase particles grew too much, and the average particle diameter exceeded 15 nm and the interparticle distance exceeded 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. 36 and no. In No. 37, since the temperature during the aging treatment was high, the second phase particles grew too much, resulting in an average particle diameter exceeding 15 nm and an interparticle distance exceeding 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 38, the rate of temperature increase during the aging treatment was too low, so the second phase particles grew too much during the temperature increase, and the average particle size exceeded 15 nm and the interparticle distance exceeded 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 39, the temperature increase rate during the aging treatment was too high, so the number of precipitation sites was reduced, and the interparticle distance was more than 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 40, the temperature drop rate during the aging treatment was too high, so that the second phase particles did not precipitate during the temperature drop, and the inter-particle distance exceeded 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. In No. 41, since the temperature lowering rate during the aging treatment was too low, the second phase particles grew during the temperature lowering, and the average particle diameter exceeded 15 nm and the interparticle distance exceeded 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. 42 and no. No. 43 was inferior in the balance of characteristics as compared with the inventive examples because the Ni concentration or the Co concentration was too high.
No. 44 is No. 44. This is an example in which a second stage aging treatment is added to 33, but the temperature during the first stage aging treatment is low and the time is short, so that the growth of the second phase particles is insufficient and the average particle size is less than 2 nm. It became. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. 45 is No. 45. In this example, the second aging treatment was added to 37, but the temperature during the first aging treatment was high and the time was long, so the second phase particles grew too much and the average particle diameter exceeded 15 nm. The inter-particle distance was over 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. 46 is No. 46. This is an example in which the second and third aging treatments are added to 33, but the temperature during the first aging treatment is low and the time is short, so the growth of the second phase particles is insufficient and the particle size is small. Was less than 2 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.
No. 47 is No. 47. In this example, the second and third aging treatments were added to 37, but the temperature during the first aging treatment was high and the time was long, so the second phase particles grew too much and the average particle size Was over 15 nm, and the inter-particle distance was over 50 nm. Therefore, the balance of characteristics was inferior compared to the inventive examples.

<Example 2>
No. of Example 1 about Cu-Ni-Si-Co type copper alloy which contains Ni, Co, Si, and other elements of mass concentration of Table 3, and has the composition which the remainder consists of Cu and an unavoidable impurity . The test piece was manufactured by the manufacturing method similar to 29. About the obtained test piece, the characteristic evaluation was performed similarly to Example 1. The results are shown in Table 4. It can be seen that the effects of the present invention can be obtained even when various elements are added.

Claims (1)

  The invention described herein.