JP2017066532A - Copper alloy sheet having excellent conductivity and stress relaxation properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy sheet having all of high strength, high conductivity and excellent stress relaxation properties, a method for producing a copper alloy sheet, and an electronic component for large current and an electronic component for heat radiation prepared with the copper alloy sheet.SOLUTION: A copper alloy sheet comprises Sn of 0.005-0.25 mass% with the balance being copper and inevitable impurities, and has 0.2% proof stress of 330 MPa or more and a thermal shrinkage of 50 ppm or less in rolling direction when heated at 200°C for 30 minutes.SELECTED DRAWING: 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 material for the above 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 and an electronic component using the copper alloy plate.

  Parts such as terminals, connectors, switches, sockets, relays, bus bars, lead frames, heat sinks, etc., that transmit electricity or heat are built into automobiles, electrical equipment, electronic devices, etc., and 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.

  A Cu—Sn alloy is known as a material having high conductivity and relatively high strength. For example, a copper alloy containing 0.10 to 0.15% by mass of Sn has been put into practical use as CDA (Copper Development Association) alloy number C14415. Moreover, Cu-Sn alloy has been used as a copper alloy foil for a negative current collector material of a secondary battery such as a flexible printed circuit board of a mobile phone or a lithium ion secondary battery. (Patent Documents 1 and 2).

JP 2003-286528 A JP 2011-142071 A

  The stress relaxation property of copper can be improved by adding an alloy element. However, since the addition of alloy elements decreases the electrical conductivity, the additive elements are required to have little influence on the decrease in electrical conductivity, and to exhibit a stress relaxation improving effect with a small amount of addition.

  An example of an element having a remarkable effect of improving stress relaxation is Zr. However, since Zr is extremely active, a part of Zr added during ingot melting is oxidized. When this Zr oxide is caught in an ingot, the surface of the product is damaged or the material being rolled is cut. Further, Zr forms precipitates in solid copper, and mechanical characteristics and stress relaxation characteristics change depending on the form of precipitation, so it is necessary to strictly adjust conditions for hot rolling and each heat treatment. From this, the manufacturing cost of the Cu—Zr alloy was very expensive.

  On the other hand, in the case of a Cu—Sn alloy, Sn does not easily form an oxide in molten copper as compared with Zr or the like, so that the ingot can be easily melted and the quality of the rolled material is good. Moreover, since Sn is stably dissolved in solid copper, product characteristics are stably expressed. Therefore, the Cu—Sn alloy can be manufactured at a low cost. However, although the stress relaxation property of the Cu—Sn alloy is superior to that of pure Cu, it has not been sufficient for the level required from the market in recent years.

  Accordingly, an object of the present invention is to provide a copper alloy plate having high strength, high conductivity, and excellent stress relaxation characteristics. Specifically, the Cu-Sn alloy is inexpensive and has excellent conductivity and strength. It is an object to improve the stress relaxation characteristics of the plate. Furthermore, another object of the present invention is to provide a method for producing the copper alloy plate and an electronic component suitable for high current use or heat dissipation use.

  As a result of intensive studies, the inventor of the Cu-Sn alloy has a 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 are improved.

  The present invention completed on the basis of the above knowledge, in one aspect, contains 0.005 to 0.25% by mass of Sn, the balance is made of copper and its inevitable impurities, and has a 0.2% proof stress of 330 MPa or more. And it is a copper alloy board characterized by the thermal expansion-contraction rate of the rolling direction at the time of heating for 30 minutes at 200 degreeC being 50 ppm or less.

  In one embodiment, the copper alloy plate according to the present invention contains 0.2% by mass or less of one or more of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, and B.

  In another embodiment, the copper alloy sheet according to the present invention has a conductivity of 80% IACS or more, and a stress relaxation rate after holding at 150 ° C. for 1000 hours is 50% 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, then cold rolling and recrystallization annealing are repeated, and after the final cold rolling, strain relief annealing is performed. (A) In the recrystallization annealing before the final cold rolling, the furnace crystal temperature is set to 250 to 800 ° C., and 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 workability per pass is 20% or less, and (C) In the straightening annealing, a continuous annealing furnace is used. A temperature of 300 to 700 ° C., a tension applied to the copper alloy plate in the furnace of 1 to 5 MPa, a copper alloy plate is passed, and a 0.2% proof stress is reduced by 10 to 50 MPa. It is a manufacturing method.

  In another aspect of the present invention, there is provided an electronic component for high current using the copper alloy plate.

  In another aspect of the present invention, there is provided 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 plate 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 large amount of heat of electronic parts that carry a large current. It is useful as a material for electronic parts.

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 80% IACS or more and a 0.2% proof stress of 330 MPa or more. If the electrical conductivity is 80% IACS or higher, it can be said that the amount of heat generated during energization 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 50% or less, more preferably 40% or less, and still more preferably 30% or less. The stress relaxation rate of a normal Cu-Sn alloy plate is about 70 to 80%. By making this 50% or less, contact with a decrease in contact force even when a large current is applied after processing into a connector. Electrical resistance is unlikely to increase, 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 Sn concentration is 0.005 to 0.25% by mass, preferably 0.05 to 0.20% by mass. If Sn exceeds 0.25% by mass, it will be difficult to obtain a conductivity of 80% IACS or more, and if Sn is less than 0.005%, it will be difficult to obtain a 0.2% proof stress of 330 MPa or more.

  In order to improve strength and heat resistance, the Cu—Sn alloy can contain one or more of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P and B. . However, if the addition amount is too large, the electrical conductivity decreases and falls below 80% IACS, or the manufacturability deteriorates. Therefore, the addition amount is 0.2% by mass or less, more preferably 0.1% by mass. % Or less, more preferably 0.05% by 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—Sn based 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 200 ° C. for 30 minutes is used as the thermal expansion / contraction rate. By adjusting the absolute value of this thermal expansion / contraction rate (hereinafter simply referred to as thermal expansion / contraction rate) to 50 ppm or less, preferably 30 ppm or less, the stress relaxation rate becomes 50% 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 melting electrolytic copper or the like as a pure copper raw material, Sn and other alloy elements are added as necessary, and cast into an ingot having a thickness of about 30 to 300 mm. 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 ratio to the above-described 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. 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 final recrystallization annealing are determined based on the target crystal grain size after annealing. 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.

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 850 ° 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.

  The annealing before the final cold rolling (final recrystallization annealing) was performed using a batch furnace when the thickness during annealing exceeded 2 mm, and a continuous annealing furnace when the thickness was 2 mm or less. In the case of a batch furnace, the heating time was 5 hours, the furnace temperature was adjusted in the range of 250 to 700 ° C., and the crystal grain size after annealing was changed. In the case of a continuous annealing furnace, the furnace temperature was set to 700 ° C., and the heating time was appropriately adjusted between 5 seconds and 15 minutes to change the crystal grain size after annealing.

  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. Then, it heated at 200 degreeC for 30 minutes, and measured the dent space | interval (L) after a heating. 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 24, the Sn concentration is adjusted to 0.005 to 0.25%, and the crystal grain size is adjusted to 50 μm or less in the recrystallization annealing before the final cold rolling, and the final cold In rolling, the total workability is adjusted to 25 to 99%, the workability per pass is adjusted to 20% or less, and in strain relief annealing, the material is passed through a continuous annealing furnace with a tension of 1 to 5 MPa and 0.2. % Proof stress was reduced by 10-50 MPa. As a result, the thermal expansion / contraction rate was 50 ppm or less, and a conductivity of 80% IACS or more, a 0.2% proof stress of 330 MPa or more, and a stress relaxation rate of 50% 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 50%.

  In Comparative Examples 2-3, although strain relief annealing was performed, since the material tension in the furnace exceeded 5 MPa, the thermal expansion / contraction rate exceeded 50 ppm and the stress relaxation rate exceeded 50%.

  In Comparative Example 4, the amount of decrease in 0.2% yield strength in strain relief annealing was excessive, and in Comparative Example 5, the amount of decrease in 0.2% yield strength in strain relief annealing was excessive. For this reason, the thermal expansion / contraction rate exceeded 50 ppm and the stress relaxation rate exceeded 50%.

  In Comparative Examples 6 and 7, 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 50%.

  In Comparative Example 8, the total degree of work in the final cold rolling was less than 25%, and in Comparative Example 9, 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 10, since the Sn concentration was less than 0.005% by mass, the 0.2% proof stress after strain relief annealing was less than 330 MPa. In Comparative Example 11, since the Sn concentration exceeded 0.25% by mass, the conductivity was less than 80% IACS.

Claims (6)

  The content of Sn is 0.005 to 0.25% by mass, the balance is copper and its inevitable impurities, has a 0.2% proof stress of 330 MPa or more, and heat in the rolling direction when heated at 200 ° C. for 30 minutes. A copper alloy plate characterized by having an expansion / contraction rate of 50 ppm or less.   2. The copper alloy sheet according to claim 1, comprising 0.2% by mass or less of one or more of Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P and B.   3. The copper alloy sheet according to claim 1, wherein the copper alloy sheet has a conductivity of 80% IACS or more and a stress relaxation rate after holding at 150 ° C. for 1000 hours is 50% or less. 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 The method for producing a copper alloy sheet according to any one of claims 1 to 3, further comprising: reducing 2% proof stress by 10 to 50 MPa.   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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