JP6301734B2 - Copper alloy material and method for producing the same - Google Patents

Description

  The present invention is a copper alloy suitable for lead frames, relays, switches, sockets, etc., as well as connectors for in-vehicle components and peripheral infrastructure, solar power generation systems, etc., centering on EVs (Electric Vehicles) and HEVs (Hybrid Electric Vehicles). The present invention relates to a material and a manufacturing method thereof.

  Copper alloys are generally used in applications such as in-vehicle components such as EVs and HEVs, connectors for peripheral infrastructure, solar power generation systems, and other lead frames, relays, switches, sockets, and the like. In recent years, the circuit power supply has been increased due to higher voltage of the circuit power supply and downsizing of electronic equipment, and there is a concern about resistance heat generation during energization and a decrease in circuit connection reliability at the spring contact part. ing. In order to solve this problem, copper alloy materials require high conductivity to suppress resistance heat generation, and stress relaxation resistance characteristics to suppress spring sag and maintain circuit connection reliability when heat is generated. Is done. Moreover, in order to ensure the contact pressure of a spring contact, the one where intensity | strength is high is preferable.

  As alloy systems having medium strength and high conductivity, copper-chromium (Cu-Cr) -based copper alloys, copper-zirconium (Cu-Zr) -based copper alloys, copper-diluted titanium (Cu-diluted Ti) -based copper An alloy etc. are mentioned. The Cu—Cr based copper alloy can improve the stress relaxation resistance by adding elements. For example, in Patent Document 1, the stress relaxation resistance is improved by adding magnesium (Mg), zirconium (Zr), titanium (Ti), tin (Sn), silver (Ag), and silicon (Si). . Patent Document 2 shows that Cu-Zr copper alloys and Cu-diluted Ti copper alloys have good stress relaxation resistance.

  In order to improve the stress relaxation resistance, it is effective to perform a predetermined heat treatment step after the final processing step. In Patent Document 2, it is shown that when stress relief annealing is not performed, the stress relaxation resistance is reduced.

  Thus, conventionally, by selecting an appropriate alloy system and appropriately devising the manufacturing process, a copper alloy material having both high conductivity and stress relaxation resistance has been obtained.

Japanese Patent No. 5307305 Japanese Patent No. 5380621

  By the way, with the rapid development of EV and HEV technology and performance improvements in recent years, in-vehicle components and peripheral infrastructure, connectors for solar power generation systems, etc., mainly for these vehicles, other lead frames, relays, switches, sockets, etc. However, it is essential to maintain the connection reliability of the circuit and the system. For this reason, it is necessary to increase the initial contact pressure of the spring contact and maintain a large contact pressure even when heat is applied due to resistance heat generation or the like during energization. In view of these requirements, the copper alloy material is required to have higher strength in addition to high conductivity and excellent stress relaxation characteristics.

  In Patent Document 1, by adding an element to a Cu—Cr-based copper alloy, it has both high electrical conductivity (EC), tensile strength (TS), and stress relaxation resistance. Since the contact pressure of the spring contact is determined by 0.2% proof stress (YS: Yield Stress), it is desired that the material has not only TS but also high YS. In order to improve the stress relaxation resistance, a heat treatment step after the final processing step is necessary. At that time, TS and YS decrease, and YS has a larger strength decrease than TS. Conventionally, if sufficient heat treatment is performed to improve the stress relaxation resistance, YS decreases even if TS can be maintained high. On the other hand, if the heat treatment is insufficient, the stress relaxation resistance is improved. There was a problem of becoming insufficient.

  Further, the Cu—Zr copper alloy and Cu—diluted Ti copper alloy described in Patent Document 2 are alloy systems with relatively low strength, although they have high conductivity and stress relaxation resistance. Therefore, the actual situation is that the strength is usually increased by making the total processing rate of the final rolling larger than 50%. However, this method increases the strength of the material. However, there exists a problem that bending workability and electroconductivity fall. When the total processing rate is 50% or less, the 0.2% proof stress is a low value of less than 380 MPa, and there is a possibility that sufficient contact pressure cannot be obtained.

  In view of the above circumstances, the problem of the present invention is that EVs, HEVs and other in-vehicle parts and connectors used in peripheral infrastructure, solar power generation systems, etc., other lead frames, relays, switches, sockets, etc. It is an object of the present invention to provide a copper alloy material having high electrical conductivity, stress relaxation resistance, and strength, and a method for producing the same.

  The present inventors conducted research on copper alloy materials suitable for the above-mentioned EV and HEV-based components, connectors for peripheral infrastructure, solar power generation systems, and other lead frames, relays, switches, sockets, and the like. . Cr is 0.10 to 0.50 mass%, Mg is 0.10 to 0.50 mass%, and at least one of Zr and Ti is 0.01 to 0.20 mass% in total, zinc (Zn) Of copper alloy material containing 0.01 to 0.50% by mass in total of at least one of iron (Fe), Sn, Ag, Si, and nickel (Ni), with the balance being Cu and inevitable impurities, In the heat treatment step after the final processing step, it has been found that by controlling the heat treatment conditions (temperature increase rate, ultimate temperature, heat treatment time, cooling rate, etc.) within an appropriate range, a decrease in YS due to heat treatment can be suppressed. As a result, the difference between TS and YS after heat treatment is reduced, and a copper alloy material having high YS can be obtained while having the same TS and stress relaxation resistance as the previous example, and high conductivity and stress relaxation characteristics. A material having strength can be obtained.

The above object of the present invention is achieved by the following means.
(1) 0.10 to 0.50% by mass of Cr, 0.01 to 0.50% by mass of Mg, and a total of 0.000 to 0.20% by mass of at least one of Zr and Ti 1st additive element group and 1 type chosen from the group which consists of 2nd additive element group which contains 0.00-0.50 mass% of at least 1 type in total among Zn, Fe, Sn, Ag, Si, and Ni And the balance is a copper alloy material consisting of Cu and inevitable impurities,
The initial load stress on the material surface is set to 80% of 0.2% proof stress, and the stress relaxation rate after being left at 150 ° C. for 1000 hours is 30% or less,
A copper alloy material having a difference in tensile strength and 0.2% proof stress of 15 MPa or less.
(2) A first additive element group containing at least one of Zr and Ti in a total amount of 0.01 to 0.20 mass%, and at least one of Zn, Fe, Sn, Ag, Si, and Ni in total 0 The copper alloy material according to (1), which contains at least one selected from the group consisting of a second additive element group containing 0.01 to 0.50 mass%.
(3) The copper alloy material according to (1) or (2), wherein the difference between the tensile strength and the 0.2% proof stress is 10 MPa or less.
(4) The copper alloy material according to any one of (1) to (3), wherein the electrical conductivity is 60% IACS or more.
(5) A method for producing a copper alloy material for producing the copper alloy material according to any one of (1) to (4),
(A) Melting and casting a copper alloy having a composition that gives the copper alloy material;
(B) Homogeneous heat treatment at 850-1050 ° C. for 0.5-12 hours,
(C) Hot working and cooling at 700-1000 ° C,
(D) cold working,
(E) After heat treatment at 350 to 650 ° C. for 10 minutes to 24 hours, cooling to 300 ° C. at a cooling rate of 2 ° C./min or less,
(F) Finish cold working with a processing rate of 10-50%,
(G) The temperature rising rate is 50 ° C./second or more, the cooling rate is 50 ° C./second or more, and the strain relief annealing is performed at 300 to 550 ° C. for 2 to 60 seconds.
The manufacturing method of the copper alloy material which has these in this order.
(6) An electrical / electronic component comprising the copper alloy material according to any one of (1) to (4).

  The copper alloy material of the present invention has high conductivity, stress relaxation resistance, and strength, and when used as a spring contact, can ensure a high contact pressure in the initial stage. In addition, the amount of heat generated during energization is small, and even if heat is generated, the contact pressure can be maintained because the spring settling is small. For this reason, it is suitable for in-vehicle components centering on EV and HEV, peripheral infrastructure, connectors for solar power generation systems, and other lead frames, relays, switches, sockets, and the like.

  A preferred embodiment of the copper alloy material of the present invention will be described in detail. Here, the “copper alloy material” means that a copper alloy material (before processing and having a predetermined alloy composition) is processed into a predetermined shape (for example, plate, strip, foil, etc.). Below, although a board | plate material and a strip are demonstrated as embodiment, the shape is not limited to this.

  The copper alloy material of the present invention has an initial load stress on the material surface of 80% of 0.2% proof stress and a stress relaxation ratio (SRR: Stress Relaxation Ratio) of 30% or less when left at 150 ° C. for 1000 hours. It is. Moreover, the copper alloy material of the present invention preferably has a difference between the tensile strength (TS) and the 0.2% proof stress (YS) of 15 MPa or less.

  As described above, the stress relaxation rate of the copper alloy material of the present invention is preferably 30% or less, more preferably 20% or less, and further preferably 15% or less. If the stress relaxation rate is too large, it is not preferable because the terminal contact pressure cannot be maintained when a thermal load is applied to the terminal due to resistance heat generation during energization. Moreover, 400 MPa or more is preferable, as for the tensile strength (TS) of the copper alloy material of this invention, 450 MPa or more is more preferable, and 500 MPa or more is further more preferable. Further, the difference between the TS and YS is preferably 15 MPa or less as described above, and more preferably 10 MPa or less. If the difference between TS and YS exceeds 15 MPa, YS becomes low, which is not preferable from the viewpoint that the terminal contact pressure cannot be secured. The structure of the copper alloy material of the present invention will be described in more detail below.

(Alloy components)
<Cr>
By precipitating Cr in the copper alloy matrix, Cr can improve strength and stress relaxation resistance without impairing electrical conductivity. In the present invention, Cr is contained in an amount of 0.10 to 0.50 mass%, preferably 0.15 to 0.40 mass%, and more preferably 0.20 to 0.35 mass%. When the amount of Cr is less than 0.10% by mass, the amount of Cr or a compound containing Cr in the copper matrix decreases, so that desired strength and stress relaxation resistance cannot be obtained. On the other hand, when it exceeds 0.50% by mass, problems such as a decrease in conductivity, a decrease in strength due to generation of coarse compounds in the copper matrix, and an adverse effect on workability occur.

<Mg>
Mg acts as a solid solution element in the copper matrix with the above-mentioned content, thereby improving strength and stress relaxation resistance. In the present invention, Mg may be contained in an amount of 0.01 to 0.50% by mass, preferably 0.05 to 0.40% by mass, and more preferably 0.10 to 0.30% by mass. When the content is less than 0.01% by mass, the effect of improving the characteristics cannot be sufficiently obtained. When the content is more than 0.50% by mass, problems such as a decrease in conductivity and an adverse effect on workability occur. Since Mg improves the stress relaxation resistance by acting as a solid solution element in the copper matrix phase, it is not preferable to simultaneously add an element that forms a compound with Mg and precipitates like P.

<Ti, Zr>
In the present invention, Ti and Zr, which are first additive elements which can be added as optional additional components, can be improved in strength and stress relaxation resistance by being precipitated in the copper matrix. In this aspect of the present invention, at least one of Ti and Zr is 0.01 to 0.20% by mass in total, preferably 0.05 to 0.15% by mass, and more preferably 0.10 to 0.15. You may make it contain the mass%. When the content is less than 0.01% by mass, the effect of the addition is not sufficient. When the content exceeds 0.20% by mass, problems such as a decrease in conductivity and an adverse effect on workability occur.

<Zn, Fe, Sn, Ag, Si, Ni>
As a preferred embodiment of the present invention, by adding the second additive element Zn, Fe, Sn, Ag, Si, Ni as an optional additive component, material characteristics such as strength, stress relaxation resistance, pressability, and plating property can be obtained. Can be improved. In this case, a total of at least one of Zn, Fe, Sn, Ag, and Si is 0.01 to 0.50 mass%, preferably 0.05 to 0.40 mass%, and more preferably 0.10 to 0 .30% by mass may be contained. If the content is less than 0.01% by mass, the effect of the addition of the second additive element is not sufficient, and if it is more than 0.50% by mass, the conductivity is lowered, the workability is adversely affected, and the raw material cost is increased. Problems can arise.

(Production method)
Next, a preferable example of the method for producing a copper alloy material of the present invention will be described. The copper alloy material of the present invention is usually produced by sequentially performing melt casting, homogenizing heat treatment, hot working, cold working, heat treatment, finishing, and strain relief annealing. Further, chamfering may be performed after hot working and before cold working. Although this manufacturing method has the same number of steps as the conventional method, the material characteristics can be improved by appropriately adjusting each process condition. In the production method of the present invention, it is important to finally perform finishing and strain relief annealing, and cold processing and heat treatment, which are the previous steps, may be performed a plurality of times. In addition, by performing solution heat treatment before the heat treatment step, it is possible to make the compound precipitated in the copper parent phase by hot working a solid solution, and to easily obtain the effect of the additive component in the finally obtained material. it can.

<Melting casting>
A copper alloy material is melted and cast in a melting furnace and cooled to obtain an ingot having a predetermined component. Melt casting can be performed by a known method.

<Homogenization heat treatment>
The homogenization heat treatment is performed in order to solidify the compound contained in the ingot in the copper matrix and to homogenize the ingot components. Thereby, the effect of the added component can be sufficiently obtained, and the variation in characteristics in the material can be reduced. In the present invention, a homogenization heat treatment is preferably performed at a temperature of 850 to 1050 ° C. for 0.5 to 12 hours, more preferably 900 to 1050 ° C., and still more preferably 950 to 1050 ° C.

<Hot processing>
The ingot immediately after the homogenization heat treatment is hot-worked (preferably 700-1000 ° C hot rolling, etc.) to reduce the plate thickness, and then cooled. Cooling is performed by water cooling, for example. If the cooling rate is too slow, some of the additive elements will precipitate during cooling, and the target final characteristics will not be obtained.

<Chamfer>
The oxide film formed on the surface of the material after hot working is removed by chamfering. The chamfering step may be performed arbitrarily. The chamfering can be performed by a known method.

<Cold processing>
The material after chamfering is cold processed (cold rolling or the like) to reduce the plate thickness.

<Heat treatment>
The material after cold working is preferably subjected to aging precipitation heat treatment at 350 to 650 ° C. for 10 minutes to 24 hours, more preferably at 400 to 600 ° C. for 1 to 10 hours. By this heat treatment, fine precipitates are precipitated in the copper matrix, and the strength, conductivity, and stress relaxation resistance are improved. When processing at a low temperature for a short time, the amount of precipitation is small, and the particle diameter of the precipitated compound is too fine, so that improvement in strength, conductivity, and stress relaxation resistance cannot be expected. In addition, when the treatment is performed at a high temperature for a long time, the deposited compound becomes coarse and the conductivity is improved, but the strength and stress relaxation resistance cannot be improved. The cooling rate to 300 ° C. after the aging heat treatment is preferably 2 ° C./min or less. By setting the cooling rate to 300 ° C. in this range, the strength, conductivity, and stress relaxation resistance can be further improved.

<Finishing cold working>
The material after the heat treatment is preferably subjected to finish cold working (cold rolling or the like) at a working rate of 10 to 50%, more preferably 10 to 40%. Finishing improves the strength and reduces the difference between TS and YS. However, the conductivity and stress relaxation resistance are reduced. When the finishing rate is less than 10%, a sufficient improvement in strength cannot be expected, and the difference between TS and YS becomes large. When the total processing rate is greater than 50%, the conductivity, stress relaxation resistance, and bending workability are remarkably lowered, and it is difficult to achieve both recovery of these characteristics and maintenance of strength in the subsequent strain relief annealing process. Become.

<Strain relief annealing>
By performing strain relief annealing on the finished material, the strength decreases and the difference between TS and YS increases. However, conductivity, stress relaxation resistance and bending workability are improved. In the present invention, strain relief annealing is performed at a temperature of 300 to 550 ° C. for 2 to 60 seconds. The temperature is more preferably in the range of 350 to 500 ° C. The time is more preferably in the range of 3 to 20 s. At this time, the heating rate and the cooling rate are preferably 50 ° C./s or more, and more preferably 100 ° C./s or more. When treated at a low temperature for a short time, the strength, conductivity, stress relaxation resistance and bending workability hardly change. Moreover, when it processes for a long time at high temperature, intensity | strength will fall remarkably and the difference of TS and YS will also become large. When the temperature increase rate and the cooling rate do not satisfy the specified range, even if target values are obtained with TS, EC, and SRR, the difference between TS and YS becomes large.

  The copper alloy material of the present invention has high electrical conductivity, stress relaxation resistance, and strength, and includes EV, HEV and other in-vehicle components, peripheral infrastructure, connectors for solar power generation systems, other lead frames, relays, Suitable for switches, sockets and the like.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

  The raw copper alloy material was melted and cast to produce an ingot, which was subjected to hot working immediately after homogenization heat treatment and water cooled. After cooling with water, the oxide film of the material was removed by chamfering, followed by cold working, heat treatment was performed at 350 to 650 ° C. for 10 minutes to 24 hours, and the cooling rate to 300 ° C. was set to 2 ° C./min. A copper alloy material was obtained by performing finish rolling and strain relief annealing after cooling. By keeping the conditions of each step within a specified range, a sample of the invention example having a target material structure was obtained. As a comparative example, materials with different ingot components and manufacturing methods were produced.

  In addition, after each heat treatment and rolling, acid cleaning and surface polishing were performed according to the state of oxidation and roughness of the material surface.

  The following evaluation was performed on the specimens thus produced.

(Difference between TS, TS and YS)
(Tensile strength: TS)
A test piece cut out so that the tensile direction was parallel to the rolling direction was subjected to a tensile test in accordance with JIS Z2241, and the tensile strength was determined. The test was performed 3 times, and the average value was shown as the test result.
(0.2% proof stress: YS)
A test piece cut out so that the tensile direction was parallel to the rolling direction was subjected to a tensile test in accordance with JIS Z2241 to obtain a 0.2% yield strength. The test was performed 3 times, and the average value was shown as the test result.
(Conductivity: EC)
In a constant temperature bath maintained at 20 ° C. (± 0.5 ° C.), the specific resistance was measured by the four probe method, and the conductivity was calculated. In addition, the distance between terminals was 100 mm.

(Stress relaxation rate: SRR)
In accordance with the Japan Copper and Brass Association JCBA T309: 2004 “Stress relaxation test method by bending copper and copper alloy sheet strips”, the initial load stress on the material surface is reduced to 0 by the cantilever method (using a cantilever block type jig). Measured under the condition of 80% of 2% proof stress and holding at 150 ° C. for 1000 hours. The test piece was a strip having a width of 10 mm, and the parallel direction of rolling and the length direction of the test piece were matched. The calculation method of the stress relaxation rate is based on the calculation method described in Japanese Patent No. 5307305. That is, the position of the tip of the test piece when an initial stress of 80% of the proof stress is applied to the test piece held in a cantilever manner before the heat treatment is at a height of δ ₀ from the reference position. This is held in a thermostatic bath at 150 ° C. for 1000 hours (the test piece is heat-treated with initial stress applied), and the position of the tip of the test piece after removing the load is a high distance H _t from the reference position. There is. Further, the position of the tip of the test piece when the above heat treatment is performed on the test piece when no stress is applied is at a height H ₁ from the reference position. From these relationships, the stress relaxation rate (%) was calculated as (H _t −H ₁ ) / (δ ₀ −H ₁ ) × 100.

  Table 1 summarizes the alloy components of the produced ingots. Alloy No. 1 to 14 are within the scope of the present invention. 15-24 are outside the scope of the present invention.

  Table 2 shows the inventive examples in which the production method is within the scope of the present invention and the components are also within the scope of the present invention, and the comparative examples in which the components are outside the scope of the present invention. Inventive examples are all copper alloy materials with TS ≧ 400 MPa, EC ≧ 60% IACS, SRR ≦ 30%, and the difference between TS and YS is 15 MPa or less, and have high conductivity, stress relaxation resistance, and strength. is there. On the other hand, in the comparative example in which the addition amount of the alloy component does not satisfy the range defined in the present invention, any of strength, conductivity, stress relaxation resistance, and workability was inferior.

  Table 3 shows the invention examples in which the components are within the scope of the present invention and the production method is also within the scope of the present invention, and the comparative examples in which the production methods are outside the scope of the present invention. Inventive examples are all copper alloy materials with TS ≧ 400 MPa, EC ≧ 60% IACS, SRR ≦ 30%, and the difference between TS and YS is 15 MPa or less, and have high conductivity, stress relaxation resistance, and strength. is there. On the other hand, the comparative example whose manufacturing conditions are outside the scope of the present invention resulted in inferior strength, conductivity, or stress relaxation resistance.

  Since the copper alloy material within the scope of the present invention can have high conductivity, stress relaxation resistance, and strength, it is possible to combine EV, HEV-centered components, connectors for peripheral infrastructure, solar power generation system, etc. Suitable for lead frames, relays, switches, sockets and the like.

Claims (6)

1st addition which contains 0.10 to 0.50 mass% of Cr, 0.01 to 0.50 mass% of Mg, and contains 0.00 to 0.20 mass% of at least one of Zr and Ti in total Containing one element selected from the group consisting of the element group and the second additive element group containing at least one of Zn, Fe, Sn, Ag, Si, and Ni in a total amount of 0.00 to 0.50% by mass, and the balance Is a copper alloy material consisting of Cu and inevitable impurities,
The initial load stress on the material surface is set to 80% of 0.2% proof stress, and the stress relaxation rate when left at 1000C for 1000 hours is 30% or less,
A copper alloy material characterized in that the difference between tensile strength and 0.2% proof stress is 15 MPa or less.   A first additive element group containing at least one of Zr and Ti in a total amount of 0.01 to 0.20 mass%, and at least one of Zn, Fe, Sn, Ag, Si, and Ni in a total of 0.01 to The copper alloy material according to claim 1, comprising at least one selected from the group consisting of a second additive element group containing 0.50% by mass.   The copper alloy material according to claim 1 or 2, wherein a difference between the tensile strength and the 0.2% proof stress is 10 MPa or less.   The copper alloy material according to any one of claims 1 to 3, wherein the conductivity is 60% IACS or more. It is a manufacturing method of the copper alloy material which manufactures the copper alloy material of any one of Claims 1-4,
(A) Melting and casting a copper alloy having a composition that gives the copper alloy material;
(B) Homogeneous heat treatment at 850-1050 ° C. for 0.5-12 hours,
(C) Hot working and cooling at 700-1000 ° C,
(D) cold working,
(E) After heat treatment at 350 to 650 ° C. for 10 minutes to 24 hours, cooling to 300 ° C. at a cooling rate of 2 ° C./min or less,
(F) Finish cold working with a processing rate of 10-50%,
(G) The temperature rising rate is 50 ° C./second or more, the cooling rate is 50 ° C./second or more, and the strain relief annealing is performed at 300 to 550 ° C. for 2 to 60 seconds.
In this order, the manufacturing method of the copper alloy material characterized by the above-mentioned.   An electrical / electronic component comprising the copper alloy material according to claim 1.