TWI422692B - Cu-Co-Si based copper alloy for electronic materials and method for producing the same - Google Patents

Description

Cu-Co-Si copper alloy for electronic materials and manufacturing method thereof

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

For copper alloys for electronic materials used in various electronic equipment parts such as connectors, switches, relays, pins, terminals, lead frames, etc., it is required to have high strength and high electrical conductivity (or thermal conductivity). As a basic feature. In recent years, the electronic components have been highly integrated and miniaturized, and the thinning has progressed rapidly. Correspondingly, the requirements for copper alloys used in electronic component parts have gradually increased.

From the viewpoint of high strength and high electrical conductivity, as a copper alloy for electronic materials, the amount of precipitation hardening type copper alloy is gradually increased, and it is a solid solution strengthening type copper alloy represented by conventional phosphor bronze or brass. The precipitation hardening type copper alloy is obtained by subjecting the solution-treated supersaturated solid solution to aging treatment to uniformly disperse fine precipitates, thereby increasing the strength of the alloy, reducing the amount of solid solution elements in copper, and improving conductivity. . Therefore, a material excellent in mechanical properties such as strength and elastic properties, and excellent in electrical conductivity and thermal conductivity can be obtained.

Among the precipitation-hardened copper alloys, Cu-Ni-Si-based copper alloys, generally called corson alloys, are representative copper alloys having high electrical conductivity, strength, and bending workability. One of the alloys currently being developed in the industry. In the copper alloy, fine Ni-Si-based intermetallic compound particles are precipitated in a copper matrix to improve strength and electrical conductivity.

There have been attempts to improve the characteristics by adding Co to the Carson alloy.

Patent Document 1 discloses that Co forms a compound with Si in the same manner as Ni, and the mechanical strength is improved. When the Cu-Co-Si alloy is aged, compared with the Cu-Ni-Si alloy, Both the mechanical strength and the electrical conductivity are improved. If the cost is allowed, the Cu-Co-Si alloy may be selected, and the optimum addition amount when adding Co is 0.05 to 2.0% by weight.

Patent Document 2 describes that cobalt should be made 0.5 to 2.5% by mass. If the cobalt content is less than 0.5%, the precipitation of the second phase of the cobalt-containing telluride will be insufficient, and if it exceeds 2.5%, an excessive amount of the second phase particles will be precipitated, resulting in a decrease in workability. And the copper alloy will have undesired strong magnetic properties. Preferably, the cobalt content is from about 0.5% to about 1.5%, and in the most preferred form, the cobalt content is from about 0.7% to about 1.2%.

The copper alloy described in Patent Document 3 is mainly developed for use as a terminal for automotive and communication equipment, and a connector material, and has a high conductivity and a medium strength Cu with a Co concentration of 0.5 to 2.5 wt%. - Co-Si alloy. According to Patent Document 3, the reason why the Co concentration is in the above range is that if the amount of addition is less than 0.5% by mass, the desired strength cannot be obtained, and if Co exceeds 2.5% by mass, the strength can be increased, but the strength can be increased. The electrical conductivity is remarkably lowered, and the hot workability is also deteriorated, and Co is preferably from 0.5 to 2.0% by mass.

The copper alloy described in Patent Document 4 has been developed to achieve high strength, high electrical conductivity, and high bending workability, and has a Co concentration of 0.1 to 3.0% by weight. The reason why the Co concentration is limited to this range is described, because if the composition range is not reached, the above effect will not be obtained, and if it exceeds the composition range, the crystal phase will be formed during casting, and casting will be performed. The cause of the crack is not good.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 11-222641

[Patent Document 2] Japanese Patent Publication No. 2005-532477

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2008-248333

[Patent Document 4] Japanese Patent Laid-Open Publication No. 9-20943

As described above, it is known that the addition of Co contributes to the improvement of the characteristics of the copper alloy. However, as described in the above prior art document, if Co is made on the high concentration side, it will adversely affect the manufacturability and alloy characteristics. In the Cu-Co-Si alloy, the improvement in characteristics when a high concentration of Co is added has not been sufficiently studied. However, it is considered that Co can improve mechanical strength and electrical conductivity more than Ni, and in the Cu-Co-Si alloy, it is possible to obtain an improvement in characteristics by further increasing the Co concentration.

On the other hand, if the Co concentration is further increased, it is necessary to carry out a solution treatment at a higher temperature, and in this case, the recrystallized grains are easily coarsened. Further, the second phase particles such as crystals and precipitates precipitated in the previous stage of the solution treatment step become obstacles and hinder the growth of the crystal grains. Therefore, the heterogeneity of the recrystallized grains in the alloy will become large, and the problem that the variation in the mechanical properties of the alloy becomes large will occur.

Therefore, one of the problems of the present invention is to provide a Cu-Co-Si-based alloy which has high conductivity, high strength, and high bending workability and which has a high mechanical concentration and a high concentration of Co. Further, another object of the present invention is to provide a method for producing such a Cu-Co-Si alloy.

The present inventors conducted intensive studies on a method for reducing the deviation of recrystallized grains, and obtained the following findings: in the production of a Cu-Co-Si-based alloy containing a high concentration of Co, in advance of the solution treatment step, fine The second phase particles are precipitated in the copper matrix phase at equal intervals as much as possible, whereby the crystal grains are subjected to a solution treatment at a relatively high temperature, and the crystal grains are pinned by the second phase particles. It does not become too large, and the pinning effect acts uniformly on the entire copper matrix, so that the size of the grown recrystallized grains can also be uniformized. Further, as a result, it is known that a Cu-Co-Si-based alloy having a small variation in mechanical properties can be obtained.

One aspect of the present invention completed in the light of the above findings is a copper alloy for an electronic material containing Co: 0.5 to 4.0% by mass, Si: 0.1 to 1.2% by mass, and the balance being Cu and inevitable impurities. The average crystal grain size is 15 to 30 μm, and the average difference between the maximum crystal grain size and the minimum crystal grain size per 0.5 mm ² of the observation field is 10 μm or less.

In one embodiment, the copper alloy of the present invention is a copper alloy for an electronic material containing Co: 0.5 to 4.0% by mass and Si: 0.1 to 1.2% by mass, and satisfying any one of the following (1) to (4). Composition conditions:

(1) further containing a maximum of 0.5% by mass of Cr;

(2) further containing one or two or more elements selected from the group consisting of Mg, Mn, Ag, and P in a total amount of 0.5% by mass;

(3) further containing an element of one or two selected from the group consisting of Sn and Zn in a total amount of 2.0% by mass in total;

(4) further containing one or two or more elements selected from the group consisting of As, Sb, Be, B, Ti, Zr, Al, and Fe in a total amount of 2.0% by mass in total;

Further, the remainder is composed of Cu and unavoidable impurities, and the average crystal grain size is 15 to 30 μm, and the average difference between the maximum crystal grain size and the minimum crystal grain size of 0.5 mm ² per observation field is 10 μm or less.

Further, in another aspect, the present invention provides a method for producing a copper alloy comprising the steps of: step 1: performing melt casting on an ingot having a desired composition; and step 2, at 950 ° C to 1050 ° C After heating for 1 hour or more, hot rolling is performed, the temperature at the end of hot rolling is set to 850 ° C or higher, and the average cooling rate from 850 ° C to 400 ° C is set to 15 ° C / s or more for cooling; Step 3, Cold rolling with a processing degree of 85% or more; step 4, aging treatment at 350 to 500 ° C for 1 to 24 hours; step 5, solution treatment at 950 to 1050 ° C, reducing the material temperature from 850 ° C to 400 The average cooling rate at ° C is set at 15 ° C / s or more for cooling; step 6, for random cold rolling; step 7, for aging treatment; step 8, for random cold rolling.

According to still another aspect of the invention, there is provided a copper-clad product comprising the copper alloy.

According to still another aspect of the present invention, an electronic device component including the copper alloy is provided.

According to the present invention, a Cu-Co-Si alloy having a mechanical and electrical property which is preferable as a copper alloy for an electronic material and having uniform mechanical properties can be obtained.

(addition of Co and Si)

Co and Si can form an intermetallic compound by performing appropriate heat treatment, and can achieve high strength without deteriorating the electrical conductivity.

When Co and Si are added in an amount of less than 0.5% by mass of Co and less than 0.1% by mass of Si, the desired strength cannot be obtained. Conversely, if Co: exceeds 4.0% by mass and Si: exceeds 1.2% by mass. In addition, although high strength can be achieved, the electrical conductivity is remarkably lowered, and the hot workability is deteriorated. Therefore, the addition amount of Co and Si is Co: 0.5 to 4.0% by mass and Si: 0.1 to 1.2% by mass. In the Cu-Co-Si system, since higher strength is required than the Cu-Ni-Si system and the Cu-Ni-Si-Co system, Co is preferably a high concentration, and is preferably 2.5% or more, more preferably 3.2% or more. . That is, the addition amount of Co and Si is preferably Co: 2.5 to 4.0% by mass, Si: 0.5 to 1.0% by mass, more preferably Co: 3.2 to 4.0% by mass, and Si: 0.65 to 1.0% by mass.

(addition amount of Cr)

Cr is preferentially precipitated in the crystal grain boundary during the cooling process during melt casting, so that the grain boundary can be strengthened, and cracks are less likely to occur during hot working, thereby suppressing a decrease in yield. In other words, Cr which is precipitated at the grain boundary during the melt casting is re-dissolved by a solution treatment or the like, and when precipitated in the subsequent aging, a precipitated particle of a bcc structure containing Cr as a main component or a compound of Si is generated. In the conventional Cu-Ni-Si alloy, the amount of Si added does not contribute to the precipitation of Si, which inhibits the increase in conductivity in a state of being dissolved in the matrix phase, but is added as a deuteration. The Cr of the material forming element further precipitates the bismuth compound, thereby reducing the amount of solid solution Si and improving the conductivity without impairing the strength. However, when the Cr concentration exceeds 0.5% by mass, the coarse second phase particles are easily formed, which may impair the product characteristics. Therefore, in the Cu-Co-Si alloy of the present invention, 0.5% by mass of Cr can be added at the maximum. However, if it is less than 0.03 mass%, it is preferably added in an amount of 0.03 to 0.5% by mass, more preferably 0.09 to 0.3% by mass, because the effect is small.

(addition amount of Mg, Mn, Ag, and P)

When a small amount of Mg, Mn, Ag, and P is added, product characteristics such as strength and stress relaxation characteristics are improved without impairing electrical conductivity. The effect of addition is mainly achieved by solid-solving the Mg, Mn, Ag, and P in the matrix phase, but further effects can be exerted by including the Mg, Mn, Ag, and P in the second phase particles. However, if the total concentration of Mg, Mn, Ag, and P exceeds 0.5%, the property improvement effect will be saturated, and the manufacturability will be impaired. Therefore, in the Cu-Co-Si-based alloy of the present invention, one or two or more selected from the group consisting of Mg, Mn, Ag, and P may be added in a total amount of 0.5% by mass. However, if it is less than 0.01% by mass, since the effect is small, it is preferably added in a total amount of 0.01 to 0.5% by mass, more preferably 0.04 to 0.2% by mass in total.

(addition amount of Sn and Zn)

When Sn and Zn are added in a small amount, product characteristics such as strength, stress relaxation property, and plating property can be improved without impairing electrical conductivity. The effect of addition is mainly exerted by dissolving the above Sn and Zn in the matrix phase. However, if the total of Sn and Zn exceeds 2.0% by mass, the property improvement effect will be saturated and the manufacturability will be impaired. Therefore, in the Cu-Co-Si-based alloy of the present invention, a total of 2.0% by mass or less of one or two selected from the group consisting of Sn and Zn can be added. However, if it is less than 0.05% by mass, since the effect is small, it is preferably added in an amount of 0.05 to 2.0% by mass in total, more preferably 0.5 to 1.0% by mass in total.

(As, Sb, Be, B, Ti, Zr, Al, and Fe)

For As, Sb, Be, B, Ti, Zr, Al, and Fe, the amount of addition is adjusted according to the required product characteristics, thereby improving products such as conductivity, strength, stress relaxation characteristics, and plating properties. characteristic. The effect of addition is mainly achieved by dissolving the above As, Sb, Be, B, Ti, Zr, Al, and Fe in the matrix phase, but the second phase particles may contain the above-mentioned As, Sb, and Be, B, Ti, Zr, Al, and Fe, or the formation of a second phase particle of a new composition exerts a further effect. However, if the total of the elements exceeds 2.0% by mass, the property improving effect will be saturated and the manufacturability may be impaired. Therefore, in the Cu-Co-Si-based alloy of the present invention, one or two or more selected from the group consisting of As, Sb, Be, B, Ti, Zr, Al, and Fe may be added in a total amount of 2.0% by mass. However, if it is less than 0.001% by mass, since the effect is small, it is preferably added in an amount of 0.001 to 2.0% by mass in total, and more preferably 0.05 to 1.0% by mass in total.

When the total amount of Mg, Mn, Ag, P, Sn, Zn, As, Sb, Be, B, Ti, Zr, Al, and Fe added exceeds 3.0%, the productivity is easily impaired. The total amount is 2.0% by mass or less, more preferably 1.5% by mass or less.

(crystal size)

The crystal grains have an effect on the strength, and the intensity is proportional to the -1/2 power of the crystal grain size, that is, the Hall-Petch equation generally holds. Further, the coarse crystal grains deteriorate the bending workability and become a cause of surface roughness during bending. Therefore, as for the copper alloy, in general, the refinement of the crystal grains can improve the strength, which is preferable. Specifically, it is preferably 30 μm or less, more preferably 23 μm or less.

On the other hand, since the Cu-Co-Si-based alloy of the present invention is a precipitation-strengthening type alloy, it is necessary to pay attention to the precipitation state of the second-phase particles. The second phase particles which are precipitated in the crystal grains during the aging treatment contribute to the improvement of the strength, but the second phase particles which are precipitated out of the crystal grain boundaries hardly contribute to the improvement of the strength. Therefore, in order to increase the strength, it is preferred to precipitate the second phase particles in the crystal grains. When the crystal grain size becomes small, the grain boundary area becomes large, so that the second phase particles are preferentially precipitated at the grain boundary during the aging treatment. In order to precipitate the second phase particles out of the crystal grains, the crystal grains must have a certain size. Specifically, it is preferably 15 μm or more, and more preferably 18 μm or more.

In the present invention, the average crystal grain size is controlled in the range of 15 to 30 μm. The average crystal grain size is preferably from 18 to 23 μm. By controlling the average crystal grain size within such a range, the two effects of the strength improving effect by the refinement of the crystal grains and the strength improving effect by precipitation hardening can be obtained in a balanced manner. Moreover, if it is the crystal grain size of this range, the outstanding bending workability and stress relaxation characteristic can be acquired.

In the present invention, the crystal grain size refers to the diameter of the smallest circle surrounding each crystal grain when the cross section parallel to the thickness direction of the rolling direction is observed by a microscope, and the average crystal grain size means the average value thereof.

In the present invention, the average difference between the maximum crystal grain size and the minimum crystal grain size per observation field of 0.5 mm ² is 10 μm or less, preferably 7 μm or less. The average of the difference is preferably 0 μm, but since it is practically difficult to achieve, the actual minimum value of the lower limit is set to 3 μm, and typically 3 to 7 μm is preferable. Here, the maximum crystal grain size refers to the largest crystal grain size observed in an observation field of 0.5 mm ² ; the so-called minimum crystal grain size refers to the smallest crystal grain observed in the same field of view. path. In the present invention, the difference between the maximum crystal grain size and the minimum crystal grain size is obtained in the observation field at a plurality of points, and the average value thereof is taken as the average of the difference between the maximum crystal grain size and the minimum crystal grain size.

The difference between the maximum crystal grain size and the minimum crystal grain size is small, which means that the crystal grain size is uniform, and the deviation of the mechanical properties of each measurement site in the same material can be reduced. As a result, the quality stability of the copper-clad product or the electronic machine part obtained by processing the copper alloy of the present invention is improved.

(Production method)

In the general process of the Caston copper alloy, first, an atmospheric melting furnace is used to melt the raw materials of electrolytic copper, Si, Co, and the like to obtain a molten liquid having a desired composition. Next, the melt is cast into an ingot. Then, hot calendering is carried out, and cold calendering and heat treatment are repeated to be finished into a strip or foil having a desired thickness and characteristics. Solid solution treatment and aging treatment in heat treatment. In the solution treatment, heating is carried out at a high temperature of about 700 to about 1000 ° C to dissolve the second phase particles in the Cu matrix and recrystallize the Cu matrix. Hot rolling is also used as a solution treatment. In the aging treatment, the temperature is heated in a temperature range of about 350 to about 550 ° C for 1 hour or more, and the second phase particles which have been solid-solved in the solution treatment are precipitated in the form of fine particles of a nanometer order. In this aging treatment, the strength and electrical conductivity will increase. In order to obtain higher strength, cold rolling is sometimes performed before and/or after aging treatment. Further, in the case where cold rolling is performed after the aging treatment, strain relief annealing (low temperature annealing) may be performed after cold rolling.

Between the above steps, grinding, polishing, shot blasting, and the like for removing rust scale on the surface are appropriately performed.

The copper alloy of the present invention is basically also subjected to the above-described process, but in order to control the deviation of the average crystal grain size and the crystal grain size within the range specified by the present invention, as described above, it is important that the solution treatment step is preceded by The fine second phase particles are preliminarily precipitated in the copper matrix phase at equal intervals and in the same manner. In order to obtain the copper alloy of the present invention, it is particularly necessary to carry out the production while paying attention to the following points.

First, coarse crystals are inevitably produced during the solidification process during casting, and coarse precipitates are inevitably generated during the cooling process during casting. Therefore, in the subsequent steps, the crystals must be crystallized. Solid solution in the parent phase. When the temperature is 950 ° C to 1050 ° C for 1 hour or more and then hot rolling, and the temperature at the end of hot rolling is 850 ° C or higher, even if Co is added and Cr is added, the above The crystals can also be dissolved in the parent phase. Temperature conditions above 950 ° C are higher temperature settings than in the case of other Carson alloys. If the holding temperature before hot rolling is less than 950 ° C, the solid solution will be insufficient, and if it exceeds 1050 ° C, there is a possibility that the material will melt. Moreover, when the temperature at the end of hot rolling is less than 850 ° C, it is difficult to obtain high strength because the elements which have been solid-solved are precipitated again. Therefore, in order to obtain high strength, it is preferred to terminate the hot rolling at 850 ° C and rapidly cool it.

At this time, if the cooling rate is slow, the Si-based compound containing Co or Cr will be precipitated again. When the heat treatment (aging treatment) for improving the strength is carried out by using such a composition, the precipitates precipitated during the cooling process are the core and grow into coarse precipitates which do not contribute to the improvement of strength, so that high strength cannot be obtained. Therefore, it is necessary to increase the cooling rate as much as possible, specifically, at 15 ° C / s or more. However, at a temperature of about 400 ° C, the precipitation of the second phase particles is remarkable, so that the cooling rate of less than 400 ° C does not become a problem. Therefore, in the present invention, the average cooling rate of the material temperature from 850 ° C to 400 ° C is set to 15 ° C / s or more, preferably 20 ° C / s or more for cooling. The so-called "average cooling rate from 850 ° C to 400 ° C" refers to the measurement of the cooling time of the material temperature from 850 ° C to 650 ° C, and by "(850-400) ( ° C) / cooling time ( The value calculated by s)" (°C/s).

As a method of speeding up cooling, water cooling is most effective. However, since the cooling rate varies depending on the temperature of the water used for water cooling, the cooling can be further accelerated by performing water temperature management. When the water temperature is 25 ° C or more, the desired cooling rate may not be obtained, and therefore it is preferably kept at 25 ° C or lower. When the material is placed in a tank in which water is stored and water-cooled, since the temperature of the water rises and it is likely to become 25 ° C or more, it is preferable to spray in a mist form (shower or mist). The fixed water temperature (below 25 ° C) cools the material or keeps the constant low temperature water flowing in the water tank to prevent the water temperature from rising. Further, by adding a water-cooling nozzle or increasing the amount of water per unit time, the cooling rate can also be increased.

Cold rolling is performed after hot rolling. In order to uniformly precipitate the precipitate, the cold rolling is performed to increase the strain at the deposition position, and it is preferable to carry out cold rolling at a rolling reduction ratio of 70% or more, and more preferably to perform cold rolling at a rolling reduction ratio of 85% or more. Calendering. If the solution treatment is carried out shortly after hot rolling without performing cold rolling, the precipitates will not be uniformly deposited. The combination of hot rolling and subsequent cold rolling can also be suitably repeated.

The first aging treatment is performed after cold rolling. If the second phase particles remain before the step is carried out, the second phase particles will further grow when the step is carried out, and thus the second phase particles initially precipitated in this step will have a difference in particle size. However, in the present invention, since the second phase particles are substantially eliminated in the step of the preceding stage, the fine second phase particles can be uniformly precipitated in a uniform size.

However, if the aging temperature of the first aging treatment is too low, the amount of precipitation of the second phase particles which bring the pinning effect is reduced, and only the pinning effect by the solution treatment can be partially obtained, and thus the crystallization is performed. The size of the grains becomes uneven. On the other hand, if the aging temperature is too high, the second phase particles will become coarse, and the second phase particles will be unevenly precipitated, so that the size of the second phase particles will become uneven. Further, the longer the aging time, the more the second phase particles grow, and therefore it is necessary to set an appropriate aging time.

The first aging treatment is carried out at 350 to 500 ° C for 1 to 24 hours, preferably at 350 ° C or higher and less than 400 ° C for the first aging treatment for 12 to 24 hours, and at 400 ° C or higher and less than 450 ° C for 6 The first aging treatment of ～12 hours, the first aging treatment at 450 ° C or higher and less than 500 ° C for 3 to 6 hours, whereby the fine second phase particles can be uniformly precipitated in the matrix phase. In the case of such a structure, the growth of the recrystallized grains generated in the solution treatment in the next step can be similarly pinned, and a uniform composition having a small variation in crystal grain size can be obtained.

The solution treatment is carried out after the first aging treatment. Here, while the second phase particles are solid-solved, fine and uniform recrystallized grains are grown. Therefore, the solution temperature must be set to 950 ° C to 1050 ° C. Here, the recrystallized grains are first grown, and then the second phase particles precipitated in the first aging treatment are solid-solved, so that the growth of the recrystallized grains can be controlled by the pinning effect. However, since the pinning effect disappears after solid solution of the second phase particles, if the solution treatment is continuously performed for a long period of time, the recrystallized grains become large. Therefore, the time for the appropriate solution treatment is 60 seconds to 300 seconds, preferably 120 to 180 seconds at 950 ° C or higher and less than 1000 ° C; and 1000 ° C or higher and less than 1050 ° C is 30 seconds to 180 seconds, preferably 60 seconds to 120 seconds.

Even in the cooling process after solution treatment, in order to avoid precipitation of the second phase particles, the average cooling rate of the material temperature from 850 ° C to 400 ° C should be above 15 ° C / s, preferably above 20 ° C / s .

A second aging treatment is performed after the solution treatment. The conditions of the second aging treatment may be conditions which are conventionally used for the miniaturization of precipitates, but care must be taken to set the temperature and time so that the precipitates are not coarsened. One of the conditions for aging treatment is as follows: a temperature range of 350 to 550 ° C for 1 to 24 hours, more preferably 400 to 500 ° C for a temperature range of 1 to 24 hours. Furthermore, the cooling rate after the aging treatment hardly affects the size of the precipitate. In the case of the second aging treatment, the precipitation position is increased, and the precipitation position is used to promote age hardening, thereby achieving strength improvement. In the case of the second aging treatment, the precipitate is used to promote work hardening, thereby achieving strength improvement. Cold rolling may also be performed before and/or after the second aging treatment.

The Cu-Co-Si alloy of the present invention can be processed into various copper-exposed products, for example, can be processed into sheets, strips, tubes, rods and wires, and the Cu-Co-Si-based copper alloy of the present invention can be used for a lead frame. , electronic components such as connectors, pins, terminals, relays, switches, and foils for secondary batteries.

[Examples]

The embodiments and comparative examples of the present invention are shown below, but the present invention is provided to further understand the present invention and its advantages, and does not limit the present invention.

In a high-frequency melting furnace, a copper alloy having the composition described in Table 1 (Example) and Table 2 (Comparative Example) was melted at 1300 ° C to cast an ingot having a thickness of 30 mm. Next, the ingot was heated to 1000 ° C, and then hot rolled to a thickness of 10 mm, and the rising temperature (temperature at which hot rolling was completed) was set to 900 ° C. After the end of the hot rolling, the average cooling rate when the material temperature was lowered from 850 ° C to 400 ° C was set to 18 ° C / s, water-cooled, and then placed in the air to be cooled. Next, in order to remove the scale on the surface, surface cutting was performed until the thickness was 9 mm, and then a plate having a thickness of 0.15 mm was formed by cold rolling. Then, after performing the first aging treatment for 3 to 12 hours at various aging temperatures (several comparative examples are not subjected to the effect treatment), the solution treatment is performed at various solid solution temperatures for 120 seconds, and then the material temperature is immediately from 850. The average cooling rate when the temperature was lowered to 400 ° C was set to 18 ° C / s, and water-cooled, and then placed in the air to be cooled. Subsequently, cold rolling was carried out to 0.10 mm, and a second aging treatment was performed at 450 ° C for 3 hours in an inert atmosphere, and cold rolling was performed to 0.08 mm to prepare a test piece.

The various characteristics of each test piece obtained in the above manner were evaluated in the following manner.

(1) Average crystal grain size

The crystal grain size is such that the observation surface is parallel to the cross section in the thickness direction of the rolling direction, and the sample is embedded in the resin, and the observation surface is mirror-polished by mechanical polishing, and then mixed with water of 100 parts by volume. A solution of 10 parts by volume of 36% hydrochloric acid was dissolved in 5% by weight of ferric chloride. The sample was immersed in the solution prepared in the above manner for 10 seconds to cause metal structure to appear. Next, the metal structure was magnified 100 times by an optical microscope, and an observation field of 0.5 mm ² was taken as a photograph, and the diameter of all the smallest circles surrounding each crystal grain was determined, and the average value was calculated for each observation field, and 15 points were obtained. The average value of the visual field was observed as the average crystal grain size.

(2) Average of the difference between the maximum crystal grain size and the minimum crystal grain size

Regarding the crystal grain size measured when the average crystal grain size is obtained, the difference between the maximum value and the minimum value is obtained for each field of view, and the average value of the observation fields at 15 points is taken as the maximum crystal grain size - the minimum crystal grain size. The average of the differences.

(3) Intensity

Regarding the strength, a tensile test in the parallel direction of rolling was performed, and a safety limit stress (YS: MPa) of 0.2% was measured. The deviation of the strength of the measurement site is the difference between the maximum intensity and the minimum intensity at 30 points, and the average intensity is the average of 30 points.

(4) Conductivity

The conductivity (EC: % IACS) was determined by measurement of the volume resistivity of the double bridge. The deviation of the conductivity of the measurement site is the difference between the maximum intensity and the minimum intensity at 30, and the average conductivity is the average of the 30 points.

(5) Stress relaxation characteristics

As for the stress relaxation characteristics, as shown in Fig. 1, on the test pieces processed to a thickness of 10 mm × 100 mm and a thickness of t = 0.08 mm, the puncture distance l is 25 mm, and the load stress at the height y ₀ is 0.2%. The height is limited by 80% of the stress, and the bending stress is applied. The permanent deformation amount (height) y shown in Fig. 2 after heating at 150 ° C for 1000 hours is measured to calculate the stress relaxation rate {[l-(y). -y ₁ )(mm)/(y ₀ -y ₁ )(mm)]×100(%)}. Furthermore, y ₁ is the initial warpage height before the load stress. The deviation of the stress relaxation rate at the measurement site was the difference between the maximum strength and the minimum strength at 30 points, and the average stress relaxation rate was the average value at the 30 points.

(6) Bending workability

The bending workability is evaluated by the surface roughness of the bent portion. The W bending test of the Badway (the bending axis and the rolling direction are the same direction) was carried out in accordance with JIS H 3130, and the surface of the curved portion was analyzed by a conjugated focal laser microscope to obtain Ra (μm) defined in JIS B 0601. The deviation of the bending roughness of the measurement portion is the difference between the maximum Ra and the minimum Ra at 30 points, and the average bending roughness is the average value of Ra at 30 points.

The alloy of No. 1 to 6 is an alloy having a low Co concentration (0.7 and 2.0% by mass). In the example of the present invention, the average strength is small due to a low Co concentration, but the variation in various characteristics is small.

The alloy of No. 7 to 36 is an alloy having a high Co concentration (3.0% by mass or more), and is an embodiment of the present invention, and any of them has strength and electrical conductivity suitable for an electronic material, and variations in characteristics are also small.

The alloy of No. 37 to 44 was not subjected to the first aging treatment, and the crystal grain size was coarsened during the solution treatment, so that the strength and the bending workability were deteriorated.

The alloy of No. 45 to 48 was not subjected to the first aging treatment, and the solid solution temperature was low. The second phase particles are not sufficiently solid-solved, and since the crystal grains are too small, the strength and stress relaxation characteristics are deteriorated.

In the alloy of No. 49 to 54, since the aging temperature of the first aging treatment is too low and the second phase particles are small, the crystal grain size is coarsened during the solution treatment, and the strength and the bending workability are deteriorated. Further, the variation in crystal grain size is large. As a result, the variation in characteristics becomes large.

In the alloy of No. 55 to 56, since the amount of addition of Co is too large, strength and electrical conductivity are deteriorated.

In the alloy of No. 57 to 64, since the aging temperature of the first aging treatment is too high and the second phase particles are unevenly grown, the crystal grain size is uneven. As a result, the variation in characteristics becomes large.

l. . . Punctuation distance

t. . . thickness

y. . . Permanent deformation (height)

y ₀ . . . height

Figure 1 is an explanatory diagram of the stress relaxation test method.

Fig. 2 is an explanatory view of the amount of permanent deformation of the stress relaxation test method.

Claims (5)

A copper alloy for electronic materials containing Co: 0.5 to 4.0% by mass, Si: 0.1 to 1.2% by mass, and the balance being composed of Cu and unavoidable impurities, and an average crystal grain size of 15 to 30 μm per observation field The average difference between the maximum crystal grain size and the minimum crystal grain size of 0.5 mm ² is 10 μm or less. A copper alloy for an electronic material containing Co: 0.5 to 4.0% by mass and Si: 0.1 to 1.2% by mass, and satisfying the following composition conditions of any one of the following (1) to (4): (1) further containing a maximum of 0.5 And (2) further containing a total of 0.5% by mass or more of one or more elements selected from the group consisting of Mg, Mn, Ag, and P; and (3) further containing a total of 2.0% by mass in total. One or two elements of Sn and Zn; (4) further containing one or more elements selected from the group consisting of As, Sb, Be, B, Ti, Zr, Al, and Fe in a total amount of 2.0% by mass in total The remainder is composed of Cu and unavoidable impurities, and the average crystal grain size is 15 to 30 μm, and the average difference between the maximum crystal grain size and the minimum crystal grain size of 0.5 mm ² per observation field is 10 μm or less. A copper alloy manufacturing method for manufacturing a copper alloy according to claim 1 or 2, comprising the steps of: step 1, melting and casting an ingot having a desired composition; and step 2; After heating at 950 ° C to 1050 ° C for 1 hour or more, hot rolling is performed, and the temperature at the end of hot rolling is set to 850 ° C or higher, and the average cooling rate from 850 ° C to 400 ° C is set at 15 ° C / s or more for cooling. Step 3, performing cold rolling with a processing degree of 70% or more; Step 4, performing aging treatment at 350 to 500 ° C for 1 to 24 hours; Step 5, performing solution treatment at 950 to 1050 ° C, the material temperature is self-treated The average cooling rate at 850 ° C down to 400 ° C is set at 15 ° C / s for cooling; step 6, for random cold rolling; step 7, for aging treatment; step 8, for random cold rolling. A copper-strength product having a copper alloy having the first or second patent application scope. An electronic machine part having a copper alloy having the first or second patent application scope.