JP5380621B1 - Copper alloy sheet with excellent conductivity and stress relaxation properties - Google Patents

Abstract

A copper alloy plate having high strength, high conductivity, and excellent stress relaxation characteristics, a method for producing the copper alloy plate, a high-current electronic component and a heat dissipation electronic component using the copper alloy plate are provided.
One or two of Zr and Ti are contained in a total of 0.01 to 0.50% by mass, the balance is made of copper and unavoidable impurities, and has a 0.2% proof stress of 330 MPa or more. , A copper alloy plate having a thermal expansion / contraction ratio in the rolling direction of 50 ppm or less when heated at 250 ° C. for 30 minutes.
[Selection figure] None

Description

  TECHNICAL FIELD The present invention relates to a copper alloy plate and electronic parts for energization or heat dissipation, and in particular, electronic parts such as terminals, connectors, relays, switches, sockets, bus bars, lead frames, heat sinks, etc. mounted on electric machines / electronic devices, automobiles and the like. The present invention relates to a copper alloy plate used as a raw material, a manufacturing method thereof, and an electronic component using the copper alloy plate. Among these, copper alloys suitable for use in high current electronic parts such as high current connectors and terminals used in electric vehicles, hybrid cars, etc., or in heat dissipation electronic parts such as liquid crystal frames used in smartphones and tablet PCs. The present invention relates to a plate, a manufacturing method thereof, and an electronic component using the copper alloy plate.

  Electrical and electronic equipment, automobiles, etc. have built-in parts for conducting electricity or heat, such as terminals, connectors, switches, sockets, relays, bus bars, lead frames, heat sinks, etc. These parts are made of copper alloy. It is used. Here, electrical conductivity and thermal conductivity are in a proportional relationship.

  In recent years, with the miniaturization of electronic components, the cross-sectional area of the copper alloy in the current-carrying part tends to be small. When the cross-sectional area becomes small, heat generation from the copper alloy when energized increases. In addition, electronic parts used in fast-growing electric vehicles and hybrid electric vehicles include parts through which a remarkably high current flows, such as a connector of a battery unit, and heat generation of a copper alloy during energization is a problem. When the heat generation becomes excessive, the copper alloy is exposed to a high temperature environment.

  In an electrical contact of an electronic component such as a connector, a deflection is given to the copper alloy plate, and a contact force at the contact is obtained by a stress generated by the deflection. When a bent copper alloy is held at a high temperature for a long time, the stress, that is, the contact force is lowered due to the stress relaxation phenomenon, and the contact electric resistance is increased. In order to cope with this problem, the copper alloy is required to be more excellent in conductivity so that the amount of heat generation is reduced, and is also required to be superior in stress relaxation characteristics so that the contact force does not decrease even if heat is generated.

  On the other hand, for example, a heat radiating component called a liquid crystal frame is used for a liquid crystal of a smartphone or a tablet PC. Even in such a copper alloy plate for heat dissipation, when stress relaxation characteristics are enhanced, creep deformation of the heat sink due to external force is suppressed, and the protection against liquid crystal components, IC chips, etc. disposed around the heat sink is improved. , Etc. can be expected. For this reason, it is desired that the copper alloy plate for heat dissipation also has excellent stress relaxation characteristics.

  It is known that when Zr or Ti is added to Cu, the stress relaxation characteristics are improved (see, for example, Patent Document 1). Examples of materials having high electrical conductivity and relatively high strength and good stress relaxation characteristics include C15100 (0.1 mass% Zr-residual Cu), C15150 (0.02 mass% Zr-residual Cu), C18140 (0 .1 mass% Zr-0.3 mass% Cr-0.02 mass% Si-residual Cu), C18145 (0.1 mass% Zr-0.2 mass% Cr-0.2 mass% Zn-residual Cu) C18070 (0.1 mass% Ti-0.3 mass% Cr-0.02 mass% Si-residual Cu), C18080 (0.06 mass% Ti-0.5 mass% Cr-0.1 mass% Ag) Alloys such as -0.08 mass% Fe-0.06 mass% Si-residual Cu) are registered in CDA (Copper Development Association).

JP 2011-1117055 A

  However, a copper alloy obtained by adding Zr or Ti to Cu (hereinafter referred to as a Cu-Zr-Ti alloy) has relatively good stress relaxation characteristics, but the level of the stress relaxation characteristics is a component that allows a large current to flow. However, it was not always sufficient as an application of a part or a part that dissipates a large amount of heat. For example, the copper alloy plate disclosed in Patent Document 1 includes 0.05 to 0.3% by mass of Zr, and Mg, Ti, Zn, Ga, Y, Nb, Mo, Ag, In, and Sn. The stress relaxation characteristics are improved by adding one or more of 0.01 to 0.3% by mass and adjusting the crystal grain size after intermediate annealing to 20 to 100 μm. The stress relaxation rate after holding for 1000 hours is at least 17.2%.

  Therefore, an object of the present invention is to provide a copper alloy plate having high strength, high conductivity, and excellent stress relaxation characteristics, and specifically, a Cu-Zr-Ti system having improved stress relaxation characteristics. It is an object to provide an alloy. Furthermore, another object of the present invention is to provide a method for producing the copper alloy plate and an electronic component suitable for large current use or heat radiation use.

  As a result of intensive studies, the inventor has adjusted Cu-Zr-Ti-based alloys to Cu-Zr- having high strength and high conductivity by adjusting the thermal expansion / contraction ratio in the rolling direction to a predetermined value. It has been found that the stress relaxation characteristics of the Ti-based alloy are improved.

  The present invention completed on the basis of the above knowledge, in one aspect, contains one or two of Zr and Ti in a total of 0.01 to 0.50 mass%, the balance consists of copper and inevitable impurities, It is a copper alloy sheet having a 0.2% proof stress of 330 MPa or more and a thermal expansion / contraction rate in the rolling direction of 50 ppm or less when heated at 250 ° C. for 30 minutes.

  In another aspect of the present invention, one or two of Zr and Ti are contained in a total amount of 0.01 to 0.50% by mass, and Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg , Si, P, Sn and B are contained in an amount of 1.0% by mass or less, the balance is made of copper and inevitable impurities, has a 0.2% proof stress of 330 MPa or more, and at 250 ° C. for 30 minutes. It is a copper alloy plate whose thermal expansion / contraction rate in the rolling direction when heated is 50 ppm or less.

  In another embodiment, the copper alloy plate according to the present invention has a conductivity of 70% IACS or more, and a stress relaxation rate after holding at 150 ° C. for 1000 hours is 15% or less.

  In another aspect of the present invention, the ingot is hot-rolled at a temperature of 800 to 1000 ° C. to a thickness of 3 to 30 mm, and then cold rolling and recrystallization annealing are repeated. A method for manufacturing a copper alloy sheet to be annealed, wherein (A) in the recrystallization annealing before the final cold rolling, the furnace temperature is set to 250 to 800 ° C., and the average grain size of the copper alloy sheet is set to 50 μm or less. (B) In the final cold rolling, the total workability is 25 to 99%, the rolling workability per pass is 20% or less, and (C) a straight annealing furnace is used in strain relief annealing, The above copper alloy, which includes passing the copper alloy plate and reducing the 0.2% proof stress by 10 to 50 MPa with an internal temperature of 300 to 700 ° C. and a tension applied to the copper alloy plate in the furnace of 1 to 5 MPa. It is a manufacturing method of a board.

  Another aspect of the present invention is an electronic component for large current using the copper alloy plate.

  In another aspect, the present invention is a heat dissipating electronic component using the copper alloy plate.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the copper alloy board which has high intensity | strength, high electroconductivity, and the outstanding stress relaxation characteristic, its manufacturing method, and an electronic component suitable for a large current use or a heat dissipation use. This copper alloy can be suitably used as a material for electronic parts such as terminals, connectors, switches, sockets, relays, bus bars, lead frames, etc., and particularly dissipates the material or the large amount of heat of electronic parts that carry a large current. Useful as a material for electronic components.

It is a figure explaining the test piece for thermal expansion-contraction rate measurement. It is a figure explaining the measurement principle of a stress relaxation rate. It is a figure explaining the measurement principle of a stress relaxation rate.

The present invention will be described below.
(Target characteristics)
The copper alloy plate according to the embodiment of the present invention has a conductivity of 70% IACS or more and a 0.2% proof stress of 330 MPa or more. If the electrical conductivity is 70% IASC or more, it can be said that the amount of heat generated when energized is equivalent to that of pure copper. In addition, if the 0.2% proof stress is 330 MPa or more, it can be said that the material has a strength necessary for a material for a component that conducts a large current or a material for a component that dissipates a large amount of heat.

  Regarding the stress relaxation characteristics of the copper alloy plate according to the embodiment of the present invention, the stress relaxation rate of the copper alloy plate (hereinafter referred to as “80% stress of 0.2% proof stress”) is maintained at 150 ° C. for 1000 hours. , Simply referred to as stress relaxation rate) is 15% or less, more preferably 10% or less. The stress relaxation rate of a normal Cu—Zr—Ti alloy is about 25 to 35%, but by reducing this to 15% or less, even if a large current is applied after processing into a connector, the contact force decreases. Increase in contact electrical resistance is unlikely to occur, and creep deformation is unlikely to occur even if heat and external force are applied simultaneously after processing into a heat sink.

(Alloy component concentration)
The copper alloy plate 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 two of Zr and Ti is less than 0.01% by mass, it becomes difficult to obtain a 0.2% proof stress of 330 MPa or more and a stress relaxation rate of 15% or less. If the total of one or two of Zr and Ti exceeds 0.5% by mass, it becomes difficult to produce an alloy due to hot rolling cracks or the like. When adding Zr, it is preferable to adjust the addition amount to 0.01 to 0.45 mass%, and when adding Ti, the addition amount is adjusted to 0.01 to 0.20 mass%. It is preferable. When the addition amount is less than the lower limit value, it is difficult to obtain the effect of improving the stress relaxation characteristics, and when the addition amount exceeds the upper limit value, conductivity and manufacturability may be deteriorated.

  Cu-Zr-Ti alloy contains at least one of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, Sn and B in order to improve strength and heat resistance. Can be made. However, if the amount added is too large, the electrical conductivity may be reduced to be less than 70% IACS, or the manufacturability of the alloy may be deteriorated. Therefore, the amount added is preferably 1.0% by mass or less in total. Is 0.5 mass% or less. Moreover, in order to acquire the effect by addition, it is preferable to make addition amount 0.001 mass% or more in total amount.

(Thermal expansion and contraction rate)
When heat is applied to a copper alloy plate, a very small dimensional change occurs. This ratio of dimensional change is referred to as “thermal expansion / contraction rate”. The present inventors have found that the stress relaxation rate can be remarkably improved by refining the metal structure of the Cu—Zr—Ti-based copper alloy sheet using the thermal expansion / contraction rate as an index.
In the present invention, a dimensional change rate in the rolling direction when heated at 250 ° C. for 30 minutes is used as the thermal expansion / contraction rate. By adjusting the absolute value of the thermal expansion / contraction rate (hereinafter simply referred to as the thermal expansion / contraction rate) to 50 ppm or less, preferably 30 ppm or less, the stress relaxation rate becomes 15% or less. The lower limit value of the thermal expansion / contraction rate is not limited in terms of the characteristics of the copper alloy sheet, but the thermal expansion / contraction rate is rarely 1 ppm or less.

(Thickness)
The thickness of the product is preferably 0.1 to 2.0 mm. If the thickness is too thin, the cross-sectional area of the current-carrying part will decrease and heat generation will increase during energization, making it unsuitable as a material for connectors that carry large currents, and because it will deform with a slight external force, It is also unsuitable as a material. On the other hand, if the thickness is too thick, bending becomes difficult. From such a viewpoint, a more preferable thickness is 0.2 to 1.5 mm. When the thickness is in the above range, the bending workability can be improved while suppressing heat generation during energization.

(Use)
The copper alloy plate according to the embodiment of the present invention can be suitably used for applications of electronic parts such as terminals, connectors, relays, switches, sockets, bus bars, lead frames, etc. used in electric / electronic devices, automobiles and the like. In particular, it is useful for applications of high current electronic components such as connectors and terminals for high current used in electric vehicles, hybrid vehicles, etc., or for heat dissipation electronic components such as liquid crystal frames used in smartphones and tablet PCs. is there.

(Production method)
After dissolving electrolytic copper or the like as a pure copper raw material and reducing the oxygen concentration by carbon deoxidation or the like, one or two of Zr and Ti, and other alloy elements are added as necessary, and the thickness is 30 to 300 mm. Cast into a moderate ingot. After this ingot is made into a plate having a thickness of about 3 to 30 mm by hot rolling at 800 to 1000 ° C., for example, cold rolling and recrystallization annealing are repeated, and finally finished to a predetermined product thickness by cold rolling. Apply strain relief annealing. Here, the means for adjusting the thermal expansion / contraction rate to the above range is not limited to a specific method, but for example, it is possible to control both conditions of final cold rolling and strain relief annealing as described later.

  In recrystallization annealing, part or all of the rolling structure is recrystallized. Further, by annealing under appropriate conditions, Zr, Ti, etc. are precipitated, and the electrical conductivity of the alloy is increased. In recrystallization annealing (final recrystallization annealing) before final 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 will be difficult to adjust the 0.2% yield strength of the product to 330 MPa or more.

  The conditions for the final recrystallization annealing are determined based on the target crystal grain size after annealing and the target product conductivity. Specifically, annealing may be performed by using a batch furnace or a continuous annealing furnace and setting the furnace temperature to 250 to 800 ° C. In a batch furnace, the heating time may be appropriately adjusted within the range of 30 minutes to 30 hours at a furnace temperature of 250 to 600 ° C. In a continuous annealing furnace, the heating time may be appropriately adjusted within a range of 5 seconds to 10 minutes at a furnace temperature of 450 to 800 ° C. Generally, when annealing is performed at a lower temperature for a longer time, higher conductivity can be obtained with the same crystal grain size.

In the final cold rolling, the material is repeatedly passed between a pair of rolling rolls to finish the target plate thickness. The total workability of final cold rolling and the workability per pass are controlled.
The total workability R (%) is given by R = (t ₀ −t) / t ₀ × 100 (t ₀ : plate thickness before final cold rolling, t: plate thickness after final cold rolling). Further, the processing degree r (%) per pass is a sheet thickness reduction rate when the rolling roll passes once, and r = (T ₀ −T) / T ₀ × 100 (T ₀ : rolling roll) Thickness before passing, T: Thickness after passing the rolling roll).
The total processing degree R is preferably 25 to 99%. If R is too small, it becomes difficult to adjust the 0.2% proof stress to 330 MPa or more. When R is too large, the edge of the rolled material may be broken.

  The processing degree r per pass is preferably 20% or less. If at least one of the passes in which r exceeds 20% is included, it is difficult to adjust the thermal expansion / contraction rate to 50 ppm or less even if strain relief annealing is performed under the conditions described later.

  The strain relief annealing of the present invention is performed using a continuous annealing furnace. In the case of a batch furnace, since the material is heated in a state of being wound in a coil shape, the material is deformed during the heating, and the material is warped. Therefore, the batch furnace is not suitable for the strain relief annealing of the present invention.

  In a continuous annealing furnace, the furnace temperature is set to 300 to 700 ° C., the heating time is appropriately adjusted in the range of 5 seconds to 10 minutes, and the 0.2% proof stress after the stress relief annealing is 0.2% before the stress relief annealing. The value is adjusted to a value 10-50 MPa lower than the proof stress, preferably 15-45 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 strain relief annealing under these conditions, the thermal expansion / contraction rate is reduced.

  If the 0.2% yield strength decrease is too small or too large, the reduction in thermal expansion / contraction due to strain relief annealing becomes insufficient, and it becomes difficult to adjust the thermal expansion / contraction to 50 ppm or less. Moreover, even if tension is too large, reduction of the thermal expansion / contraction rate due to strain relief annealing becomes insufficient, and it becomes difficult to adjust the thermal expansion / contraction rate to 50 ppm or less. On the other hand, if the tension is too small, the material in the passing plate of the annealing furnace may come into contact with the furnace wall, and the surface or edge of the material may be damaged.

  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.

  After adding the alloy element 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 formed into a plate having a thickness of 15 mm by hot rolling. After grinding and removing the oxide scale on the surface of the hot rolled plate, annealing and cold rolling were repeated, and the product was finished to a predetermined product thickness by the final cold rolling. Finally, strain relief annealing was performed using a continuous annealing furnace.

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

  In the final cold rolling, the total workability and the workability per pass were controlled.

  In strain relief annealing using a continuous annealing furnace, the furnace temperature was 500 ° C., the heating time was adjusted between 1 second and 15 minutes, and the amount of 0.2% proof stress reduction due to strain relief annealing was variously changed. In addition, various tensions were added to the material in the furnace. In some cases, strain relief annealing was not performed.

The following measurement was performed on the material in the process of manufacturing and the material after strain relief annealing.
(component)
The alloy element concentration of the material after strain relief annealing was analyzed by ICP-mass spectrometry.

(Average grain size after final recrystallization annealing)
After the cross section perpendicular to the rolling direction was finished to a mirror surface by mechanical polishing, crystal grain boundaries were revealed by etching. On this metal structure, the average crystal grain size was determined by measurement according to the cutting method of JIS H 0501 (1999).

(0.2% yield strength)
For the material after the final cold rolling and strain relief annealing, sample No. 13B specified in JIS Z2241 was taken so that the tensile direction was parallel to the rolling direction, and pulled in parallel with the rolling direction in accordance with JIS Z2241. Tests were performed to determine 0.2% yield strength.

(conductivity)
A test piece was taken from the material after strain relief annealing so that the longitudinal direction of the test piece was parallel to the rolling direction, and the conductivity at 20 ° C. was measured by a four-terminal method in accordance with JIS H0505.

(Thermal expansion and contraction rate)
A strip-shaped test piece having a width of 20 mm and a length of 210 mm was taken from the material after strain relief annealing so that the longitudinal direction of the test piece was parallel to the rolling direction, and L ₀ (= 200 mm) as shown in FIG. Two dents were engraved with an interval of. Thereafter, the test piece was heated at 250 ° C. for 30 minutes, and the dent interval (L) after heating was measured. Then, the absolute value of the value calculated by the formula of (L−L ₀ ) / L ₀ × 10 ⁶ was obtained as the thermal expansion / contraction rate (ppm).

(Stress relaxation rate)
A strip-shaped test piece having a width of 10 mm and a length of 100 mm was collected from the material after strain relief annealing so that the longitudinal direction of the test piece was parallel to the rolling direction. As shown in FIG. 2, with the position of l = 50 mm as the working point, the test piece was given a deflection of y ₀ and a stress (s) corresponding to 80% of the 0.2% proof stress in the rolling direction was applied. y ₀ was determined by the following equation.
y ₀ = (2/3) · l ² · s / (E · t)
Here, E is the Young's modulus in the rolling direction, and t is the thickness of the sample. After unloading after heating at 150 ° C. for 1000 hours, the amount of permanent deformation (height) y is measured as shown in FIG. 3, and the stress relaxation rate {[y (mm) / y ₀ (mm)] × 100 (%) } Was calculated.

  Table 1 shows the evaluation results. In the final cold rolling, a plurality of passes were performed, and the maximum value in the degree of processing of each pass is shown. In addition, the expression “<10 μm” in the crystal grain size after the final recrystallization annealing indicates that all of the rolling structure is recrystallized and the average crystal grain size is less than 10 μm, and that only a part of the rolling structure is recrystallized. Both cases of crystallization are included.

  In the copper alloy plates of Invention Examples 1 to 25, the total concentration of Zr and Ti is adjusted to 0.01 to 0.50 mass%, and the crystal grain size is adjusted to 50 μm or less in the recrystallization annealing before the final cold rolling. In the final cold rolling, the total workability is adjusted to 25 to 99%, the workability per pass is adjusted to 20% or less, and the material is passed through the continuous annealing furnace with a tension of 1 to 5 MPa in strain relief annealing. The 0.2% proof stress was reduced by 10 to 50 MPa. As a result, the thermal expansion / contraction rate 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 rate of 15% or less were obtained.

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

  In Comparative Examples 5 and 6, the 0.2% yield strength decrease in strain relief annealing was excessively small, and in Comparative Examples 7 and 8, the 0.2% yield strength decrease in strain relief annealing was excessive. For this reason, the thermal expansion / contraction rate exceeded 50 ppm and the stress relaxation rate exceeded 15%. In Comparative Examples 9 and 10, since the degree of processing per pass in the final cold rolling exceeded 20%, the thermal expansion / contraction rate exceeded 50 ppm, and the stress relaxation rate exceeded 15%.

  In Comparative Example 11, the total work degree in the final cold rolling was less than 25%, and in Comparative Example 12, the crystal grain size after recrystallization annealing before the final cold rolling exceeded 50 μm. The 0.2% proof stress was 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 strain relief annealing was less than 330 MPa, and the stress relaxation rate exceeded 15%.

Claims (6)

  One or two of Zr and Ti are contained in a total of 0.01 to 0.50% by mass, the balance is made of copper and inevitable impurities, has a 0.2% proof stress of 330 MPa or more, and at 250 ° C. A copper alloy sheet characterized by having a thermal expansion / contraction ratio in the rolling direction of 50 ppm or less when heated for 30 minutes.   One or two of Zr and Ti are contained in a total of 0.01 to 0.50% by mass, and further Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, Sn, and B One or more of them are contained in an amount of 1.0% by mass or less, the balance is made of copper and inevitable impurities, has a 0.2% proof stress of 330 MPa or more, and heat stretch in the rolling direction when heated at 250 ° C. for 30 minutes. A copper alloy sheet characterized in that the rate is 50 ppm or less.   3. The copper alloy sheet according to claim 1, wherein the copper alloy sheet has a conductivity of 70% IACS or more and a stress relaxation rate of 15% or less after holding at 150 ° C. for 1000 hours. In the method of manufacturing a copper alloy plate, after ingot is hot rolled at 800 to 1000 ° C. to a thickness of 3 to 30 mm, cold rolling and recrystallization annealing are repeated, and after final cold rolling, strain relief annealing is performed. There,
(A) In the recrystallization annealing before the final cold rolling, the furnace temperature is 250 to 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 25 to 99%, the rolling work per pass is 20% or less,
(C) In the strain relief annealing, using a continuous annealing furnace, the furnace temperature is 300 to 700 ° C., the tension applied to the copper alloy sheet in the furnace is 1 to 5 MPa, and the copper alloy sheet is passed through, 0 .2% yield strength is reduced by 10-50 MPa,
The manufacturing method of the copper alloy plate of any one of Claims 1-3 containing this.   The electronic component for large currents using the copper alloy plate of any one of Claims 1-3.   The electronic component for thermal radiation using the copper alloy plate of any one of Claims 1-3.

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