TW201502291A - Copper alloy sheet having outstanding electro-conductivity and stress release characteristics - Google Patents

Abstract

Provided are: a copper alloy sheet having high strength, high electro-conductivity and outstanding stress release characteristics; a method for producing copper alloy sheet; and high-current electronic components and heat-radiating electronic components using this copper alloy sheet. This copper steel sheet contains 0.01-0.50 mass% of a total of Zr and/or Ti, with the remainder being made up of copper and unavoidably impurities, has a yield strength of 0.2% at 330MPa or more, and when heated at 250 DEG C for 30 minutes, the thermal expansion rate in the rolling direction does not exceed 50ppm.

Description

Copper alloy sheet excellent in conductivity and stress relaxation characteristics

The present invention relates to a copper alloy plate and an electronic component for power supply or heat dissipation, and more particularly to a terminal, a connector, a relay, a switch, a socket, a bus bar, a lead frame, and a heat sink for mounting on a motor/electronic machine, an automobile, or the like. A copper alloy plate of a material such as a board or the like, a method for producing the same, and an electronic component using the copper alloy sheet. Among them, the use of a high-current electronic component such as a high-current connector or a terminal used in an electric vehicle, a hybrid electric vehicle, or the like, or a liquid crystal frame used in a smart phone or a tablet PC. A copper alloy sheet for use in heat dissipation electronic parts, a method for producing the same, and an electronic component using the copper alloy sheet.

In motors/electronic machines, automobiles, etc., terminals, connectors, switches, sockets, relays, bus bars, lead frames, heat sinks, etc. are used for conducting or conducting parts, and these parts are made of copper alloy. Here, there is a proportional relationship between electrical conductivity and thermal conductivity.

In recent years, with the miniaturization of electronic components, the cross-sectional area of the copper alloy in the current-carrying portion tends to decrease. If the sectional area is reduced, the heat generation from the copper alloy increases when energized. In addition, electronic components used in the development of a booming electric vehicle or a hybrid electric vehicle have components that flow very high current, such as a connector of a battery unit, and the heat generation of the copper alloy at the time of energization has always been a problem. If the heat becomes too large, the copper alloy is exposed to a high temperature environment.

The copper alloy plate is bent at an electrical contact of an electronic component such as a connector, and the contact force at the contact is obtained by the stress generated by the bending. When the copper alloy to which the bending is applied is maintained at a high temperature for a long period of time, the stress, that is, the contact force is lowered due to the stress relaxation phenomenon. This leads to an increase in contact resistance. In order to cope with this problem, it is required that the copper alloy is more excellent in electric conductivity to reduce the amount of heat generation, and the stress relaxation property is also required to be excellent so that the contact force does not decrease even if it is heated.

On the other hand, a liquid crystal such as a smart phone or a tablet uses a heat dissipating component called a liquid crystal frame. When the stress relaxation property is improved, the copper alloy sheet for heat dissipation can be expected to suppress the creep deformation of the heat dissipation plate due to an external force, and improve the protection of the liquid crystal component, the IC chip, and the like disposed around the heat dissipation plate. effect. Therefore, the copper alloy sheet for heat dissipation is also expected to have excellent stress relaxation characteristics.

It is known that when Zr or Ti is added to Cu, the stress relaxation property is improved (for example, refer to Patent Document 1). As a material having high conductivity and relatively high strength and good stress relaxation characteristics, the CDA (Copper Development Association) registers, for example, C15100 (0.1% by mass Zr-the rest of Cu) and C15150 (0.02% by mass). Zr-the remaining Cu), C18140 (0.1% by mass Zr-0.3% by mass Cr-0.02% by mass Si-the rest of Cu), C18145 (0.1% by mass Zr-0.2% by mass Cr-0.2% by mass Zn-the rest of Cu), C18070 ( 0.1% by mass Ti-0.3% by mass Cr-0.02% by mass Si-the rest of Cu), C18080 (0.06% by mass Ti-0.5% by mass Cr-0.1% by mass Ag-0.08% by mass Fe-0.06% by mass Si-the rest of Cu), etc. alloy.

[Patent Document 1] Japanese Laid-Open Patent Publication No. 2011-117055

However, a copper alloy in which Zr or Ti is added to Cu (hereinafter referred to as a Cu-Zr-Ti alloy) has relatively good stress relaxation characteristics, but the level of stress relaxation characteristics is used for a component that flows a large current or The use of parts that dissipate heat is not sufficient. For example, the copper alloy sheet disclosed in Patent Document 1 is added with 0.05 to 0.3% by mass of Zr, and 0.01 to 0.3% by mass of Mg, Ti, Zn, Ga, Y, Nb, Mo, Ag, In, and Sn are added. One or more, and further adjusting the crystal grain size after the intermediate annealing to 20 to 100 μm, thereby improving the stress relaxation property, but the stress relaxation rate after the embodiment is maintained at 150 ° C for 1000 hours is also the lowest. 17.2%.

Accordingly, an object of the present invention is to provide a copper alloy sheet having high strength, high electrical conductivity, and excellent stress relaxation characteristics. Specifically, the present invention provides a Cu-Zr-Ti with improved stress relaxation characteristics. Alloy. Furthermore, it is an object of the present invention to provide a method for producing the copper alloy sheet and an electronic component suitable for high current use or heat dissipation.

The inventors of the present invention have found that, for the Cu-Zr-Ti alloy, Cu-Zr-Ti having high strength and high conductivity is adjusted by adjusting the thermal expansion ratio of the rolling direction to a specific value. The stress relaxation properties of the alloy are improved.

The present invention, which is completed based on the above findings, is a copper alloy plate containing a total of 0.01 to 0.50% by mass of one or two of Zr and Ti, and the remainder consisting of copper and unavoidable impurities, The 0.2% guaranteed stress of 330 MPa or more is 50 ppm or less in the rolling direction when heated at 250 ° C for 30 minutes.

In another aspect, the present invention is a copper alloy sheet containing a total of 0.01 to 0.50% by mass of one or both of Zr and Ti, and containing 1.0% by mass or less of Ag, Fe, Co, Ni, Cr, One or more of Mn, Zn, Mg, Si, P, Sn, and B, the remainder consisting of copper and unavoidable impurities, having a 0.2% guaranteed stress of 330 MPa or more, and a thermal expansion ratio in the rolling direction when heated at 250 ° C for 30 minutes It is 50 ppm or less.

In another embodiment, the copper alloy sheet of the present invention has a conductivity of 70% IACS or more, and the stress relaxation rate after maintaining at 150 ° C for 1,000 hours is 15% or less.

In still another aspect, the invention is a method for manufacturing a copper alloy plate, which is characterized in that the ingot is hot-rolled to a thickness of 3 to 30 mm at 800 to 1000 ° C, and then subjected to cold rolling and recrystallization annealing, and finally cooled. After calendering, the relaxation annealing is performed. The manufacturing method comprises: (A) adjusting the average crystal grain size of the copper alloy sheet to 50 μm in the recrystallization annealing before the final cold rolling, setting the furnace temperature to 250 to 800 ° C. (B) In the final cold rolling, the total workability is set to 25 to 99%, and the rolling degree per pass is set to 20% or less; and (C) in the relaxation annealing, In the continuous annealing furnace, the temperature in the furnace is set to 300 to 700 ° C, and the tension applied to the copper alloy plate in the furnace is set to 1 to 5 MPa, and the copper alloy plate is passed, so that the 0.2% guaranteed stress is lowered by 10 to 50 MPa.

In another aspect, the present invention is a high current electronic component using the above copper alloy plate.

In another aspect, the present invention is an electronic component for heat dissipation using the above copper alloy sheet.

According to the present invention, it is possible to provide a copper alloy sheet having high strength, high electrical conductivity, and excellent stress relaxation characteristics, a method for producing the same, and an electronic component suitable for high current use or heat dissipation use. The copper alloy can be used as a raw material for electronic components such as terminals, connectors, switches, sockets, relays, bus bars, and lead frames, and is particularly useful as a raw material for discharging high-current electronic components or as a raw material for dissipating heat-reducing electronic components.

Fig. 1 is a view showing a test piece for measuring a thermal expansion ratio.

Fig. 2 is a view showing the principle of stress relaxation rate measurement.

Figure 3 is a diagram illustrating the principle of stress relaxation rate measurement.

Hereinafter, the present invention will be described.

(target characteristics)

The copper alloy sheet according to the embodiment of the present invention has a conductivity of 70% IACS or more and a 0.2% guaranteed stress of 330 MPa or more. If the conductivity is 70% IACS or more, it is considered that the amount of heat generated at the time of energization is equivalent to pure copper. In addition, when the 0.2% proof stress is 330 MPa or more, it is considered to have the strength required as a raw material of a component that flows a large current or a material that disperses heat.

The stress relaxation property of the copper alloy sheet according to the embodiment of the present invention is applied When the stress of 80% of the stress is maintained at 150 ° C for 1000 hours, the stress relaxation rate of the copper alloy sheet (hereinafter simply referred to as stress relaxation rate) is 15% or less, more preferably 10% or less. In general, the Cu-Zr-Ti alloy has a stress relaxation rate of about 25 to 35%. When the stress relaxation rate is 15% or less, even if a large current flows after processing into a connector, it is difficult to generate a contact force. The decrease in the contact resistance is reduced, and even if it is subjected to heat and external force after being processed into a heat dissipation plate, it is difficult to cause creep deformation.

(alloy concentration)

The copper alloy sheet according to the embodiment of the present invention contains one or two of Zr and Ti in a total amount of 0.01 to 0.50% by mass (more preferably 0.02 to 0.20% by mass). When the total of one or both of Zr and Ti is less than 0.01% by mass, it is difficult to obtain a 0.2% proof stress of 330 MPa or more and a stress relaxation ratio of 15% or less. When the total of one or both of Zr and Ti exceeds 0.5% by mass, it is difficult to produce an alloy due to thermal rolling cracking or the like. When Zr is added, the amount of addition is preferably adjusted to 0.01 to 0.45% by mass, and when Ti is added, the amount of addition is preferably adjusted to 0.01 to 0.20% by mass. When the amount added is less than the lower limit, it is difficult to obtain an effect of improving stress relaxation characteristics, and when the amount added exceeds the upper limit, conductivity or manufacturability may be deteriorated.

In order to improve strength or heat resistance, the Cu-Zr-Ti alloy may contain one or more of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, Sn, and B. However, when the amount of addition is too large, the electrical conductivity is lowered to less than 70% IACS, or the manufacturability of the alloy is deteriorated. Therefore, the amount of addition is 1.0% by mass or less, more preferably 0.5% by mass or less. . Moreover, in order to obtain the effect by addition, it is preferable to add 0.001 mass % or more in total amount.

(thermal expansion rate)

If the copper alloy sheet is heated, a very small dimensional change will result. The ratio of the dimensional change is referred to as "thermal expansion ratio". The present inventors have found that the metal structure of the Cu-Zr-Ti-based copper alloy sheet can be tempered by the thermal expansion rate index, and the stress relaxation rate can be remarkably improved.

In the present invention, the dimensional change rate in the rolling direction when heated at 250 ° C for 30 minutes is used. For thermal expansion rate. The absolute value of the thermal expansion coefficient (hereinafter simply referred to as the thermal expansion ratio) is adjusted to 50 ppm or less, preferably 30 ppm or less, and the stress relaxation ratio is 15% or less. The lower limit of the thermal expansion ratio is not limited in terms of the characteristics of the copper alloy sheet, but the thermal expansion ratio is preferably 1 ppm or less.

(thickness)

The thickness of the product is preferably from 0.1 to 2.0 mm. When the thickness is too small, the cross-sectional area of the energized portion is reduced, and the heat generation during energization is increased. Therefore, it is not suitable as a material for a connector that flows a large current, and is deformed by a small external force, so that it is not suitable as a heat sink or the like. Raw materials. On the other hand, if the thickness is too thick, bending processing becomes difficult. From the above point of view, the thickness is preferably 0.2 to 1.5 mm. When the thickness is in the above range, heat generation during energization can be suppressed, and bending workability can be improved.

(use)

The copper alloy sheet according to the embodiment of the present invention can be applied to electronic parts such as terminals, connectors, relays, switches, sockets, bus bars, and lead frames used in motors, electronic equipment, automobiles, and the like, and can be used particularly for electric vehicles. Uses for high-current electronic components such as connectors or terminals for high-current use in hybrid electric vehicles, and applications for heat-dissipating electronic components such as liquid crystal frames used in smart phones or tablet personal computers.

(Production method)

Electrolytic copper or the like which is a pure copper raw material is melted, and after reducing the oxygen concentration by carbon deoxidation or the like, one or two kinds of Zr and Ti and, if necessary, other alloying elements are added, and an ingot having a thickness of about 30 to 300 mm is cast. The ingot is formed into a plate having a thickness of about 3 to 30 mm by hot rolling, for example, at 800 to 1000 ° C, and then subjected to cold rolling and recrystallization annealing, and finally processed into a specific product thickness by final cold rolling, and finally implemented. Relaxation annealing. Here, the means for adjusting the thermal expansion ratio to the above range is not limited to a specific method, and for example, two conditions of final cold rolling and relaxation annealing can be controlled in the following manner.

In the recrystallization annealing, part or all of the rolled structure is recrystallized. Further, by annealing under appropriate conditions, Zr, Ti, and the like are precipitated, and the electrical conductivity of the alloy increases. In the final recrystallization annealing (final recrystallization annealing) before cold rolling, the average crystal grain size of the copper alloy sheet is adjusted to 50 μm or less. If the average crystal grain size is too large, it is difficult to adjust the 0.2% proof stress of the product to 330 MPa or more.

The conditions for the final recrystallization annealing are determined based on the target crystal size after annealing and the target product conductivity. Specifically, as long as a batch furnace or a continuous annealing furnace is used, the furnace temperature may be set to 250 to 800 ° C for annealing. In the batch furnace, the heating time can be appropriately adjusted in the range of 30 to 30 hours in the furnace at 250 to 600 °C. In the continuous annealing furnace, the heating time may be appropriately adjusted in the range of 5 to 10 minutes in the furnace at 450 to 800 °C. In general, if annealing is performed at a lower temperature and for a longer period of time, a higher electrical conductivity can be obtained with the same crystal grain size.

Finally, the cold rolling is carried out, and the material is repeatedly passed between a pair of calender rolls to be gradually processed into a target sheet thickness. Control the total processing degree of the final cold rolling and the degree of processing per pass.

The total degree of work R (%) can be obtained from R = (t _{0 -} t) / t ₀ × 100 (t ₀ : plate thickness before final cold rolling, t: plate thickness after final cold rolling). Further, the degree of processing r (%) per pass means the plate thickness reduction rate when passing through the calender roll once, and can be obtained by r = (T _{0 -} T) / T ₀ × 100 (T ₀ : before passing through the calender roll The thickness, T: obtained by rolling the thickness of the roll).

The total workability R is preferably set to 25 to 99%. If R is too small, it is difficult to adjust the 0.2% proof stress to 330 MPa or more. If R is too large, there is a case where the edge of the rolled material is broken.

Preferably, the degree of processing r per pass is 20% or less. When the pass of r exceeds 20% is included in all the passes, it is difficult to adjust the thermal expansion ratio to 50 ppm or less even if the relaxation annealing is performed under the following conditions.

The relaxation annealing of the present invention is carried out using a continuous annealing furnace. In the case of a batch furnace, since the material is heated in a state of being wound into a coil, the heating process is performed. The material will deform and cause warpage in the material. Therefore, the batch furnace is not suitable for the relaxation annealing of the present invention.

In the continuous annealing furnace, the furnace temperature is set to 300-700 ° C, and the heating time is appropriately adjusted in the range of 5 seconds to 10 minutes, and the 0.2% guaranteed stress after the relaxation annealing is adjusted to 0.2 before the relaxation annealing. % guarantees a low stress value of 10 to 50 MPa, preferably a value of 15 to 45 MPa lower. Further, the tension applied to the material in the continuous annealing furnace is adjusted to 1 to 5 MPa, more preferably 1 to 4 MPa. By performing the relaxation annealing under this condition, the thermal expansion ratio is lowered.

When the reduction amount of the 0.2% proof stress is too small or too large, the decrease in the thermal expansion ratio due to the relaxation annealing is insufficient, and it is difficult to adjust the thermal expansion ratio to 50 ppm or less. Moreover, when the tension is too large, the thermal expansion rate due to the relaxation annealing is also insufficient, and it is difficult to adjust the thermal expansion ratio to 50 ppm or less. On the other hand, if the tension is too small, the material may contact the furnace wall during the annealing process to cause damage to the surface or edge of the material.

[Examples]

In the following, the embodiments and the comparative examples of the present invention are shown together, but the embodiments are provided to better understand the present invention and its advantages, and are not intended to limit the present invention.

After the alloying element was added to the molten copper, it was cast into an ingot having a thickness of 200 mm. The ingot was heated at 950 ° C for 3 hours, and a plate having a thickness of 15 mm was formed by hot rolling. After the scale of the surface of the hot rolled sheet is ground and removed, it is repeatedly annealed and cold rolled, and finally processed into a specific product thickness by cold rolling. Finally, a continuous annealing furnace is used for the relaxation annealing.

In the final recrystallization annealing, a batch furnace was used, and the heating time was set to 5 hours and the temperature in the furnace was adjusted in the range of 250 to 700 ° C to change the crystal grain size and electrical conductivity after annealing.

The total degree of processing and the degree of processing per pass are controlled in the final cold rolling.

In the relaxation annealing using a continuous annealing furnace, the furnace temperature is set to 500 ° C and the heating time is adjusted between 1 second and 15 minutes, and the 0.2% guaranteed stress generated by the relaxation annealing is used. The amount of reduction produces various changes. Moreover, various changes are made in the tension applied to the material in the furnace. Further, in some cases, the relaxation annealing was not performed.

The materials in the middle of manufacture and the material after the relaxation annealing were measured as follows.

(ingredient)

The alloying element concentration of the material after the relaxation annealing was analyzed by ICP-mass spectrometry.

(Average crystal grain size after final recrystallization annealing)

After the cross section orthogonal to the rolling direction is processed into a mirror surface by mechanical polishing, grain boundaries are formed by etching. The metal structure was measured in accordance with the cutting method of JIS H 0501 (1999), and the average crystal grain size was determined.

(0.2% guaranteed stress)

For the material after the final cold rolling and the relaxation annealing, the test piece No. 13B specified in JIS Z2241 is collected in parallel with the direction of rolling and the direction of rolling, and the tensile test is performed in parallel with the rolling direction in accordance with JIS Z2241 to obtain 0.2. % guarantees stress.

(Conductivity)

The test piece was collected from the material after the relaxation annealing in such a manner that the longitudinal direction of the test piece was parallel to the rolling direction, and the electrical conductivity of 20 ° C was measured by a four-terminal method in accordance with JIS H0505.

(thermal expansion rate)

The test piece with a width of 20 mm and a length of 210 mm is taken from the material after the relaxation of the test piece in the direction of the longitudinal direction of the test piece in parallel with the rolling direction, and is printed at intervals of L ₀ (=200 mm) as shown in FIG. Two dents. Thereafter, the test piece was heated at 250 ° C for 30 minutes, and the pit interval (L) after heating was measured. Then, the absolute value of the value calculated by the equation of (LL ₀ ) / L ₀ × 10 ⁶ was obtained as the thermal expansion ratio (ppm).

(stress relaxation rate)

A test piece of a short strip shape having a width of 10 mm and a length of 100 mm was collected from the material after the relaxation annealing in such a manner that the longitudinal direction of the test piece was parallel to the rolling direction. As shown in Fig. 2, a position of l = 50 mm was used as an action point, and the test piece was subjected to bending of y ₀ so that the load corresponds to a stress (s) of 0.2% of the stress in the rolling direction of 80%. y _{0 is} obtained by the following formula.

y ₀ =(2/3)‧l ² ‧s/(E‧t)

Here, E is the Young's modulus of the rolling direction, and t is the thickness of the sample. After heating at 150 ° C for 1000 hours, the load was removed, and the amount of permanent deformation (height) y was measured as in Fig. 3, and the stress relaxation rate {[y(mm) / y ₀ (mm)] × 100 (%)} was calculated.

The evaluation results are shown in Table 1. The final cold rolling is performed in multiple passes, showing the maximum of the processing degrees of the passes. Further, the description of "<10 μm" in the crystal grain size after the final recrystallization annealing includes the case where the calendered structure is completely recrystallized, the average crystal grain size thereof is less than 10 μm, and the case where only one part of the calendered structure is recrystallized. These two situations.

In the copper alloy sheets of Inventive Examples 1 to 25, the total concentration of Zr and Ti was adjusted to 0.01 to 0.50% by mass, and in the recrystallization annealing before the final cold rolling, the crystal grain size was adjusted to 50 μm or less in the final cold rolling. The total processing degree is adjusted to 25~99%, and the processing degree per pass is adjusted to be less than 20%. In the relaxation annealing, the material is passed through the continuous annealing furnace at a tension of 1~5MPa to reduce the 0.2% guaranteed stress. 10~50MPa. As a result, the thermal expansion ratio was 50 ppm or less, and a conductivity of 70% IACS or more, a 0.2% proof stress of 330 MPa or more, and a stress relaxation ratio of 15% or less were obtained.

In Comparative Example 1, the relaxation annealing was not performed, the thermal expansion ratio exceeded 50 ppm, and the stress relaxation rate exceeded 30%. In Comparative Examples 2 to 4, although the relaxation annealing was performed, since the material tension in the furnace exceeded 5 MPa, the thermal expansion ratio exceeded 50 ppm, and the stress relaxation ratio exceeded 15%.

In Comparative Examples 5 and 6, 0.2% of the relaxation annealing was used to ensure that the amount of decrease in stress was too small. In Comparative Examples 7 and 8, 0.2% of the relaxation annealing was used to ensure that the amount of reduction was excessive. Therefore, the thermal expansion ratio exceeds 50 ppm, and the stress relaxation rate exceeds 15%. In Comparative Examples 9 and 10, since the degree of processing per pass of the final cold rolling exceeded 20%, the thermal expansion ratio exceeded 50 ppm, and the stress relaxation rate exceeded 15%.

In Comparative Example 11, since the total degree of processing in the final cold rolling was less than 25%, in Comparative Example 12, since the crystal grain size of the recrystallization annealing before the final cold rolling was more than 50 μm, after the relaxation annealing The 0.2% guaranteed stress is less than 330 MPa.

In Comparative Example 13, since the total concentration of Zr and Ti was less than 0.01% by mass, the 0.2% proof stress after the relaxation annealing was less than 330 MPa, and the stress relaxation rate exceeded 15%.

Claims (6)

A copper alloy plate containing a total of 0.01 to 0.50% by mass of one or two of Zr and Ti, the remainder being composed of copper and unavoidable impurities, having a 0.2% guaranteed stress of 330 MPa or more, and calendering at 250 ° C for 30 minutes The thermal expansion rate in the direction is 50 ppm or less. A copper alloy plate containing one or two of Zr and Ti in a total amount of 0.01 to 0.50% by mass, and containing 1.0% by mass or less of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, One or more of Sn and B, the remainder consists of copper and unavoidable impurities, and has a 0.2% guaranteed stress of 330 MPa or more. When heated at 250 ° C for 30 minutes, the thermal expansion ratio in the rolling direction is 50 ppm or less. A copper alloy sheet according to claim 1 or 2, which has a conductivity of 70% IACS or more, and a stress relaxation ratio of 15% or less after maintaining at 150 ° C for 1,000 hours. The invention relates to a method for manufacturing a copper alloy plate, which is a method for manufacturing a copper alloy plate according to any one of claims 1 to 3, which is characterized in that the ingot is hot-rolled to a thickness of 3 to 30 mm at 800 to 1000 ° C, and then repeatedly cooled. Calendering and recrystallization annealing, and after final cold rolling, relaxation annealing; the manufacturing method comprises: (A) in the recrystallization annealing before the final cold rolling, the furnace temperature is set to 250 ~ 800 ° C, The average crystal grain size of the copper alloy plate is adjusted to 50 μm or less; (B) in the final cold rolling, the total workability is set to 25 to 99%, and the rolling work degree per pass is set to 20% or less; And (C) in the relaxation annealing, using a continuous annealing furnace, the furnace temperature is set to 300 to 700 ° C, and the tension applied to the copper alloy plate in the furnace is set to 1 to 5 MPa, and the copper alloy plate is passed. , to reduce the 0.2% guaranteed stress by 10~50MPa. A high-current electronic component using a copper alloy plate according to any one of claims 1 to 3. An electronic component for heat dissipation, which is used in any one of claims 1 to 3 Copper alloy plate.