JP2015048518A - Copper alloy sheet excellent in stress relaxation characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy sheet having high strength, high conductivity and excellent stress relaxation characteristic.SOLUTION: The copper alloy sheet is a rolled material which contains 0.03 to 0.20 mass% of Zr and the balance copper with inevitable impurities and in which particles having a diameter of 2 μm or more observed in a rolling face after heating the rolled material at 950°C for 30 minutes and cooling it are present in an amount of 2000//mmor less.

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, etc. 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.

  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 is added to Cu, the stress relaxation property is improved (see, for example, Patent Document 1). This good stress relaxation characteristic is manifested by the uniform dispersion of Cu ₅ Zr fine precipitates.
Examples of practical materials having high electrical conductivity, relatively high strength, and good stress relaxation properties include alloys such as C15100 (0.1 mass% Zr-residual Cu) and C15150 (0.02 mass% Zr-residual Cu). And CDA (Copper Development Association).

JP 2011-1117055 A

However, although a copper alloy in which Zr is added to Cu (hereinafter referred to as a Cu-Zr alloy) has relatively good stress relaxation characteristics, the level of the stress relaxation characteristics is the use of a component that conducts a large current or is large. It was not necessarily sufficient as an application of parts that dissipate 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%.
Moreover, in the Cu-Zr alloy plate manufactured industrially, there also existed the subject that the dispersion | variation in the stress relaxation characteristic for every product was large.

  Therefore, an object of the present invention is to provide a copper alloy plate having high strength, high conductivity, and excellent stress relaxation characteristics. Specifically, a Cu-Zr alloy having improved stress relaxation characteristics is provided. The issue is to provide. Furthermore, an object of the present invention is to provide an electronic component suitable for high current use or heat dissipation use.

As a result of intensive studies, the present inventor has found that there is a correlation between specific compound particles contained in the Cu—Zr-based alloy and stress relaxation characteristics. That is, when the Cu—Zr alloy plate is heated at a high temperature and then cooled with water (solution treatment), precipitates such as Cu ₅ Zr are dissolved in the copper base, but some precipitates remain without being dissolved. When there are many non-solution-soluble precipitates, the stress relaxation characteristics deteriorated.
Many of the non-solution-soluble precipitates have a diameter exceeding several μm, and the composition thereof is Zr—C, Zr—S, Zr—O or the like. Non-solution-soluble precipitates were generated at the initial stage of alloy production, such as during the cooling process during ingot casting and during heating of the ingot before hot rolling. In addition, since it is thermally stable, once produced, it remains in the product without being decomposed.
The hot-rolled Cu—Zr alloy sheet is repeatedly processed into a product by cold rolling and heat treatment, and Cu ₅ Zr particles effective for stress relaxation properties are precipitated by heat treatment at a relatively low temperature.
The non-solution-soluble precipitate is considered to reduce the amount of Cu ₅ Zr deposited during heat treatment by consuming a part of Zr contained in the alloy. In general, since precipitates are likely to nucleate on the existing heterogeneous phase, the non-solution-soluble precipitates act as Cu ₅ Zr precipitation sites, thereby inhibiting the fine dispersion of Cu ₅ Zr. . Thus, it was speculated that the non-solution-soluble precipitate affects both the amount and form of the Cu ₅ Zr precipitate and degrades the stress relaxation characteristics.

The present invention completed on the basis of the above knowledge is, in one aspect, a rolled material containing 0.03 to 0.20% by mass of Zr, the balance being copper and inevitable impurities, and the rolled material is at 950 ° C. Provided is a copper alloy sheet characterized in that the number of particles having a diameter of 2 μm or more observed on the rolling surface is 2000 / mm ² or less after heating for 30 minutes and water cooling.
Moreover, this copper alloy plate contains at least 0.1% by mass in total of at least one of Ti, Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, Sn and B. Also good.
Further, it preferably has a tensile strength of 300 MPa or more and a conductivity of 75% IACS or more.
In any of the above-described copper alloy plates, the stress relaxation rate after being held at 150 ° C. for 1000 hours is preferably 15% or less.
From another aspect, the present invention provides a high-current electronic component using any of the copper alloy plates described above.
Furthermore, from another aspect, the present invention provides a heat dissipating electronic component using any of the above-described copper alloy plates.

  According to the present invention, it is possible to provide a copper alloy plate having high strength, high conductivity, and excellent stress relaxation characteristics, and an electronic component suitable for large current use or heat radiation 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, heat sinks, etc. It is useful as a material for electronic parts that dissipate heat.

It is a figure which shows an example of the non-solution-soluble precipitate observed on a rolling surface after heating the copper alloy plate of this invention for 30 minutes at 950 degreeC, and water-cooling. 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 75% IACS or more and a tensile strength of 300 MPa or more. If the electrical conductivity is 75% IACS or higher, heat generation during energization is suppressed, and conduction of electricity and heat is promoted. In addition, if the tensile strength is 300 MPa or more, it can be said that the material has a strength necessary for a material for a part that conducts a large current or a material for a part that dissipates a large 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. By reducing the stress relaxation rate, even if a large current is applied after processing the connector, it is difficult for the contact electrical resistance to increase due to the decrease in contact force, and heat and external force are applied simultaneously after processing the heat sink. However, creep deformation hardly occurs.

(Alloy components)
The copper alloy plate according to the embodiment of the present invention contains 0.03 to 0.20% by mass, more preferably 0.05 to 0.15% by mass of Zr. When Zr is less than 0.03% by mass, it becomes difficult to obtain a tensile strength of 300 MPa or more and a stress relaxation rate of 15% or less. When Zr exceeds 0.20 mass%, it becomes difficult to obtain a conductivity of 75% IACS or more, and it becomes difficult to produce an alloy due to hot rolling cracks or the like.

  Cu-Zr alloy contains at least one of Ti, 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 addition amount is too large, the electrical conductivity may be reduced to be less than 75% IACS or the productivity of the alloy may be deteriorated. Therefore, the addition amount is preferably 0.1% by mass or less, more preferably Is 0.05 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.

(Non-solution precipitate)
Non-solution soluble precipitates can be observed by the following procedure.
(1) The Cu—Zr alloy plate is heated at 950 ° C. for 30 minutes and then immediately cooled with water.
(2) Electropolishing the rolled surface, dissolving the copper matrix, and exposing the precipitates to the surface.
(3) The size and number of precipitates are measured using a scanning electron microscope.
According to an experimental study by the present inventors, when the measurement object of the non-solution-soluble precipitate is a particle having a diameter of 2 μm or more, a good correlation is obtained with the stress relaxation characteristics. In addition, the diameter here is the diameter of the smallest circle containing particles.
By controlling the number of particles having a diameter of 2 μm or more to 2000 particles / mm ² or less, the stress relaxation rate is reduced. A more preferable number is 1000 / mm ² or less, and a more preferable number is 500 / mm ² or less.
In addition, non-solution-soluble precipitates are often collected and distributed at the time of production, and if this is stretched by rolling, it may cause surface scratches on the product. Such surface flaws are treated as defective in applications where appearance is required. Also from this point, it is required that there are fewer non-solution-soluble precipitates.

(Thickness)
The thickness of the product is preferably 0.1 to 3.0 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 is suitably used for applications of electronic parts such as terminals, connectors, relays, switches, sockets, bus bars, lead frames, heat sinks, etc. used in electric / electronic devices, automobiles, etc. In particular, applications of high-current electronic components such as connectors and terminals for large currents used in electric vehicles, hybrid vehicles, etc., or uses of electronic components for heat dissipation such as liquid crystal frames used in smartphones and tablet PCs Useful for.

(Production method)
Electro copper or the like is melted as a pure copper raw material, Zr and other alloy elements are added as required, and cast into an ingot having a thickness of about 20 to 300 mm. Next, 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, and then cold rolling and recrystallization annealing are repeated and finished to a predetermined product thickness by final cold rolling. Finally, strain relief annealing is applied.

  Non-solution-soluble precipitates are formed in the steps from melting to hot rolling, and hardly change in the subsequent steps. Therefore, in order to adjust the non-solution-soluble precipitate, it is necessary to optimize the process conditions from melting to hot rolling. For example, the higher the melting temperature, the slower the cooling rate at the time of casting, and the longer the heating time of the ingot before hot rolling, the larger the insoluble solution precipitates tend to increase.

The general conditions of the previous process after hot rolling will be described below.
In recrystallization annealing, part or all of the rolling structure is recrystallized. Further, by annealing under appropriate conditions, Zr precipitates and the conductivity of the alloy increases. 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 becomes difficult to adjust the tensile strength of the product to 300 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 degree of work of the final cold rolling is preferably 25 to 99%. Here, the working degree r (%) is given by r = (t ₀ −t) / t ₀ × 100 (t ₀ : plate thickness before rolling, t: plate thickness after rolling). If r is too small, it becomes difficult to adjust the tensile strength to 300 MPa or more. If r is too large, the edge of the rolled material may be broken.

  In strain relief annealing, it is preferable to adjust the tensile strength after strain relief annealing to a value 10 to 100 MPa lower than the value before strain relief annealing (final rolling rise). When using a batch furnace, the heating time is suitably adjusted in the range of 15 minutes to 30 hours at an in-furnace temperature of 100 to 500 ° C., and when using a continuous annealing furnace, the in-furnace temperature of 300 to 700 ° C. is 5 seconds. The heating time may be appropriately adjusted within a range of 10 minutes to 10 minutes. By performing the strain relief annealing, the stress relaxation rate is reduced. In addition to controlling the non-solution-dissolving precipitates, a stress relaxation rate of 15% or less can be obtained by performing this strain relief annealing.

  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.

For each inventive example and each comparative example, a copper alloy plate was produced under the conditions shown in Table 1. Specifically, it is as follows.
Electrolytic copper was dissolved in a graphite crucible, and Zr and other alloying elements were added as required. Thereafter, the molten metal was held at 1200 ° C. or 1300 ° C. for 10 minutes.
Thereafter, the molten metal was cast into a cast iron mold to produce an ingot having a thickness of 30 mm, a width of 60 mm, and a length of 100 mm. In order to change the cooling rate at that time, when 5 minutes passed immediately after casting, one was put into the water tank together with the mold, and one was air-cooled to room temperature.
Next, the ingot was heated at 950 ° C. for 3 hours or 10 hours, and then hot-rolled to a thickness of 15 mm.
After grinding and removing the oxide scale on the surface of the plate after hot rolling, annealing and cold rolling were repeated and finished to a predetermined product thickness by final cold rolling. Finally, strain relief annealing was performed.

In the annealing before final cold rolling (final recrystallization annealing), the material was heated at 400 ° C. for 3 hours.
In the final cold rolling, the degree of processing was changed variously.
In the strain relief annealing, the heating time of the material was set to 30 minutes, the heating temperature of the material was adjusted in the range of 200 to 400 ° C., and the tensile strength in the rolling direction was reduced by about 30 MPa.

The following measurements were performed on the material (product) after strain relief annealing.
(component)
The alloy element concentration was analyzed by ICP-mass spectrometry.

(Non-solution precipitate)
The sample was heated at 950 ° C. for 30 minutes and then immediately put into a water bath. Next, electrolytic polishing of the rolled surface was performed. In electropolishing, the anode was a sample and the cathode was a stainless steel plate, and current was passed in phosphoric acid at a voltage of 11 V for 1 minute. A secondary electron image of the precipitate was observed on the surface after electropolishing using a scanning electron microscope. FIG. 1 shows an observation example of non-solution-soluble precipitates.

(Tensile strength)
A No. 13B test piece defined in JIS Z2241 was taken so that the tensile direction was parallel to the rolling direction, and a tensile test was performed in parallel with the rolling direction in accordance with JIS Z2241, to determine the tensile strength.

(conductivity)
The test piece was sampled 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.

(Stress relaxation rate)
A strip-shaped test piece having a width of 10 mm and a length of 100 mm was collected so that the longitudinal direction of the test piece was parallel to the rolling direction. As shown in FIG. 2, a stress corresponding to 80% of the 0.2% proof stress (measured in accordance with JIS Z2241) in the rolling direction is applied to the test piece with the position of l = 50 mm as the working point, giving y ₀ deflection (S) was loaded. 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.
(Surface damage)
The presence or absence of surface flaws was observed with a 10 × field of view using an optical microscope. The observation area was 0.05 m ² .

Table 1 shows the evaluation results.
In the inventive examples, the number of insoluble precipitates having a diameter of 2 μm or more was 2000 / mm ² or less, and a stress relaxation rate of 15% or less was obtained. In the comparative example, the number of insoluble precipitates having a diameter of 2 μm or more exceeded 2000 pieces / mm ² , and the stress relaxation rate exceeded 15%.
Further, when the number of non-solution soluble precipitates was less than 500 pieces / mm ² , no surface scratch was observed.
Table 2 shows data obtained by evaluating the characteristics of the invention examples 1 to 5 and the comparative examples 1 to 3 in Table 1 before the strain relief annealing (final final cold rolling) by the above method. Although a stress relaxation rate of 15% or less has not been obtained, the stress relaxation rate is clearly reduced by reducing non-solution-soluble precipitates.

Claims (6)

The diameter is observed on the rolling surface after containing 0.03 to 0.20% by mass of Zr and the balance being copper and inevitable impurities, and heating the rolled material at 950 ° C. for 30 minutes and water cooling. A copper alloy plate, wherein the number of particles of 2 μm or more is 2000 / mm ² or less.   2. The copper alloy according to claim 1, comprising at least 0.1% by mass in total of at least one of Ti, Ag, Fe, Co, Ni, Cr, Mn, Zn, Mg, Si, P, Sn and B. Board.   The copper alloy sheet according to claim 1 or 2, which has a tensile strength of 300 MPa or more and a conductivity of 75% IACS or more.   The copper alloy sheet according to any one of claims 1 to 3, wherein a stress relaxation rate after holding at 150 ° C for 1000 hours is 15% or less.   The electronic component for large currents using the copper alloy plate of any one of Claims 1-4.   The electronic component for thermal radiation using the copper alloy plate of any one of Claims 1-4.