TWI460905B - Copper alloy strips for charging the battery marking material - Google Patents

Description

Copper alloy strip for battery marking material for charging

The present invention relates to a copper alloy strip for use in a battery marking material for charging, and in particular to a marking material for connecting a high performance charging battery such as a Li ion battery.

A rechargeable battery such as a nickel-cadmium battery or a Li-ion battery is used in a portable electronic device such as a video camera or a laptop computer. In addition, the demand for electric vehicles or hybrid vehicles has also increased due to the trend of lowering the environmental load in recent years, and the development of Li-ion secondary batteries for vehicles has also been promoted. In order to ensure the necessary capacitance, the rechargeable battery is used by electrically connecting a plurality of cells of a single structure in a state in which a plurality of cells are in close proximity to each other. The metal lead material used for the connection of the battery is called a current collecting mark or a mark, and is connected to the battery. In many cases, it is fused with the electrode of the battery by resistance welding by heat generated by a resistor. When a plurality of batteries in which the electrodes are welded and sealed are housed in a compact case, when they are stored in a compact or complicated case, etc., when the case is taken out of the case and the battery is placed, it is necessary to perform the operation again. The bending recovery and bending process of the mark requires not only good weldability with the electrode material but also reversible bendability for the material used for marking.

A nickel plated stainless steel plate or a soft steel plate or a nickel plate is usually used in the battery electrode material. When a battery electrode and a mark composed of the material plates are connected by a resistance welding machine, the conductivity of copper is too high, so that an excessive current flows in the mark and causes a melt loss, so that it cannot be put into practical use. Use a nickel strip with relatively good fusion fusion for the previous marking material material. However, nickel is a rare metal, the price is very high and there is also a risk of instability in supply. Further, since the conductivity of nickel is relatively low at 21.5% IACS (measured value), there is a disadvantage that it is easier to generate heat during use in a high-capacity battery. Therefore, in order to reduce the cost and improve the performance of the battery, it is required to replace nickel with another metal material. At present, the price of the copper raw material metal is about one-third of that of nickel, which is attractive. However, even if various known copper alloys are used as the marking material, it is difficult to weld, and thus it is practically used. Further, although attempts have been made to improve the weldability by using a copper or a heat-resistant copper alloy base layer and a clad layer of a weld layer made of Ni or the like (JP-A-11-297300), the strength of copper is low and the above The heat-resistant copper alloy is also inferior in bending workability, and cannot meet the demand for miniaturization.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 11-297300

It is an object of the present invention to provide a copper alloy strip which is preferable for a battery connection marker which has good balance, good electrical conductivity, reversibility, and weldability.

The present invention has been found to be satisfactory in that a Cu-Zn-based copper alloy which is subjected to reflow-plated Sn is preferable for a battery marking material having good tensile strength, electrical conductivity, reversibility, and weldability. Specifically, it is as follows.

(1) A Sn-plated copper alloy strip for marking a battery for charging, comprising a copper alloy strip containing 2 to 12% by mass of Zn and containing 0.1 to 1.5% by mass of Sn, and the balance being composed of copper and unavoidable impurities. The aspect ratio of the crystal grain in the plate thickness direction and the rolling parallel direction is 0.1 or more, and is implemented as follows Reflow plating Sn: The thickness of the Sn layer after reflow is 0.10 to 1.60 μm, and the thickness of the Cu-Sn compound is 0.10 to 1.90 μm.

(2) The Sn-plated copper alloy strip according to the above (1), which is subjected to Ni/Cu base plating or Cu base plating.

(3) The copper alloy strip according to (1) or (2) above, which has a conductivity of 31 to 70% IACS.

(4) The copper alloy strip according to any one of the above (1) to (3), wherein the number of times of repeated bending in the 180° adhesion bending and bending recovery test is 2.5 or more.

(5) The copper alloy strip according to any one of the above (1) to (4), which has a tensile strength of 300 to 610 MPa.

(copper alloy)

The present invention relates to a Cu-Zn-Sn-based alloy. In addition to the Cu-Zn-Sn-based alloy, Cu-Zr, which is a preferred composition of the copper alloy having high strength and high electrical conductivity, is listed as a preferred composition in the paragraph "0021" of Patent Document 1. A system, a Cu-Cr system, a Cu-Be-Co alloy, or other Cu-Ni-Si system, Cu-Mg-P system, Cu-Ni-Sn system, Cu-Fe-P system, or the like. However, as a result of research by the present inventors, it has been found that although these copper alloys have high strength and high electrical conductivity, either of the weldability and the overflexibility are inferior and are not suitable for use as a mark.

It is known that the Cu-Zn-Sn-based alloy of the present invention manages the aspect ratio of the crystal grain size in addition to the appropriate Zn and Sn contents, and has properties as a marking material other than high strength and high electrical conductivity. And thus the best.

(A) Zn concentration

The alloy of the present invention contains 2 to 12% by mass (hereinafter referred to as %), preferably 2 to 9% of Zn, and the balance is a copper alloy composed of copper and unavoidable impurities. If the Zn concentration is less than 2%, the strength necessary as a mark is insufficient, and the conductivity becomes too high to cause the mark to be melted at the time of fusion, or the amount of heat generated by the current passing through the copper alloy strip is small. Since it is difficult to flow a current to the stainless steel plate or the soft steel plate on the battery electrode side, the weldability is deteriorated. When the Zn concentration exceeds 12%, Zn is vaporized at the time of welding, the material is embrittled, the weldability is deteriorated, and the electrical conductivity is lowered, so that it is difficult to achieve high performance of the battery. Further, in general, the price of Zn is one-half or less of the price of Cu, so it can be said that it is an additive element that is also effective for cost reduction.

(B) Sn concentration

Sn has the function of promoting work hardening of the pressure delay, contributing to the strength improvement. The copper alloy strip of the present invention is subjected to reflow soldering of Sn, so that the corner material produced in the step after the Sn plating is inevitably contains the Sn component. However, since the copper alloy strip of the present invention contains Sn in the above range, there is an advantage that the corner material after the Sn plating can be easily recovered and reused as the raw material of the copper alloy of the present invention. On the other hand, in the case where an additive element other than Sn is used to form a copper alloy composition containing no Sn in order to achieve strength improvement, it is necessary to carry out a refining step in order to recover the corner material after the Sn plating. However, in the case where the Sn concentration is low, when the corner material produced before the Sn plating is combined with the Sn-side material after the Sn plating as the scrap material for the copper alloy raw material of the present invention, the corner material after the Sn plating is used. Since the amount of use is limited, it is difficult to obtain a mass balance, and recycling and recycling are poor. On the other hand, if the Sn concentration is high, the amount of the corner material generated before the Sn plating is limited, so it is still difficult to obtain the quality. Balanced. Accordingly, the alloy of the present invention contains 0.1 to 1.5%, preferably 0.1 to 0.8%, and more preferably 0.2 to 0.6% of Sn. If the Sn concentration is less than 0.1%, the desired effect cannot be obtained, and if the Sn concentration exceeds 1.5%, the electrical conductivity is lowered.

(C) other elements

In order to improve the characteristics other than the strength of the existing high-strength, high-conductivity copper alloy, Mg, Fe, and Si are often added. However, caution is required in the case where the alloy of the present invention contains such elements for the following reasons.

When the copper alloy of the present invention contains Mg as the active metal, Mg is liable to vaporize at the time of welding and generate a spark to make welding difficult, and the material is embrittled. Therefore, the Mg concentration is preferably 0.3% or less, and more preferably 0.1% or less.

When the copper alloy of the present invention contains Fe, it reacts with the electrode material (welding rod) of the fusion splicer to corrode the fusion splicing rod, and the weldability and productivity are inferior. Further, since Fe is hardly dissolved in the copper matrix, even if the Fe content is minute, the Fe-rich phase is locally present in the parent phase, which causes the above problem. Therefore, the Fe concentration is preferably 0.05% or less.

In the case of a Carson alloy containing a precipitation type copper alloy of Si and Ni, spot resistance welding cannot be performed, and the weldability is inferior. Although the present invention is not limited by theory, it is considered that the Joule heat generated at the time of welding causes solid solution of the precipitate, and the electrical conductivity is rapidly lowered to make welding difficult.

(D) Characteristics of alloy strips

The conductivity of the alloy strip of the present invention (JIS H 0505) is usually 31~ 70% IACS, preferably 35 to 70% IACS, further preferably 40 to 60% IACS, and if it is in this range, it can be suitably used as a marking material. If it is less than 31% IACS, it is easier to generate heat when the battery is used. On the other hand, when it exceeds 70% IACS, melting occurs at the time of resistance welding, or a sufficient current does not flow in the metal plate on the battery electrode side, and the weldability is lowered.

Regarding the reverse bending property of the alloy strip of the present invention, when the bending is restored after 180° U-bending or close-fitting bending, and the first cycle is performed, the number of times of repeated bending until the sample having a width of at least 10 mm is broken is usually 2.5. The number of times or more is preferably 3.0 or more, and more preferably 3.5 or more. If it is less than 2.5 times, it is likely to be damaged during the operation of accommodating the battery in the casing, and the production efficiency is lowered.

When the tensile strength (JIS Z 2241) of the alloy strip of the present invention is usually 300 to 610 MPa, preferably 390 to 600 MPa, and more preferably 390 to 540 MPa, it can be preferably used as a marking material. In the case of more than 610 MPa, the repeated bending is generally poor. Moreover, when the tensile strength is less than 300 MPa, the vibration resistance standard required for the mark for Li ion batteries is generally not satisfied.

The thickness of the alloy strip of the present invention is not particularly limited, but is preferably 0.03 to 1.00 mm, more preferably 0.12 to 0.6 mm, for example, 0.15 mm, and if it is this thickness, it satisfies the strength as a marking material for charging battery connection, Fusion.

(E-1) Cu substrate reflow solder plating Sn

The copper alloy strip of the present invention is subjected to reflow soldering of 0.20 to 3.50 μm (the total thickness of the Sn layer and the Cu-Sn compound layer after the reflow treatment) to achieve excellent weldability. The reflow-plated Sn is formed on a copper alloy base material, and a Sn-plated layer is formed on the Cu-based plating layer by electroplating or the like, and is formed by reflow processing. By the reflow treatment, the copper alloy base material and the Cu-based plating layer react with the Sn-plated layer to form a Cu-Sn compound layer (Cu is formed by diffusion of the Sn-plated layer, so it is also called a diffusion layer), and the plating layer is formed. The structure forms a pure Sn layer, a Cu-Sn compound layer, a Cu plating layer, and a base material layer from the surface side (see FIG. 1). Further, the Cu-plated layer can be completely converted into a Cu-Sn compound after reflow, and can also remain. Further, in the present invention, the influence of the thickness of the Cu-plated layer on the weldability is hardly observed, and the thickness of the Cu-based plating layer before the reflow process is not particularly limited, but is preferably 0.05 to 3.0 μm, more preferably 0.1~1.0μm. Further, Cu substrate plating may not be performed.

(E-2) Ni/Cu substrate reflow solder plating Sn

Since the total thickness of the Cu-Sn compound layer and the pure Sn layer after reflow is related to the weldability, it is also possible to perform Ni plating before performing the above-described Cu plating for the purpose of improving the heat resistance of the plating.

Ni/Cu substrate reflow soldering is performed on the base material, and a Ni plating layer, a Cu plating layer, and a Sn plating layer are sequentially formed by electroplating, and then reflow processing is performed. By this reflow treatment, Cu between the plating layers reacts with Sn to form a Cu-Sn compound layer. On the other hand, the Ni plating layer remains in a state (thickness) which is almost just completed plating. The structure of the plating layer after the reflow treatment forms a Sn plating layer, a Cu-Sn compound layer, and a Ni plating layer from the surface side. The thickness of the Ni base plating layer is not particularly limited, but is preferably 0.1 to 0.8 μm, more preferably 0.1 to 0.3 μm. Other plating conditions are equivalent to (E-1).

2 is a copper alloy strip of the present invention having a structure of a pure Sn layer, a Cu-Sn compound layer, and a copper alloy base material layer from the bottom, and is disposed on an Fe plate on which an upper surface is provided with a Ni plating layer. And subject to the cross section after the fusion Sheet (FE-SEM image). The fused portion (X of Fig. 2) is as follows, that is, the pure Sn layer remaining in the surrounding R (right) and L (left) becomes thin or disappears, and the Cu-Sn compound layer existing under the copper alloy strip The Ni plating layer on the surface of the battery electrode is directly fused (see Fig. 2). The present invention is not limited by theory, but regarding the fusion mechanism of the copper alloy strip of the present invention, first, a Sn-plated pure Sn layer (melting point 230 ° C) exists between the surface of the marked copper alloy and the Ni surface of the surface of the battery electrode. The Joule heat generated by the resistance welding is melted, and the molten Sn is moved from the pressurizing portion to the non-pressurizing portion under the pressure of the welding electrode rod. Therefore, it is considered that the Cu-Sn compound layer (melting point of 800 ° C or more) existing in the inner layer is more likely to be in contact with Ni as an active new surface than the pure Sn layer, and further, by heating and pressurizing the components (Cu- The Sn compound and the Ni element are mutually diffused and firmly bonded. Therefore, it can be said that in the mark after welding, the Cu-Sn compound layer on the surface of the alloy strip reacts with the Ni layer on the surface of the battery electrode to be fused, and in order to achieve excellent weldability, there must be a Cu-Sn of reflow-plated Sn. Compound layer.

Further, in order to investigate the effect of the above mechanism and the addition of Zn, in order to protect the new surface of the Cu-Sn compound layer before the welding step, it is preferable to use the inside of the Sn plating as long as possible without growing the diffusion layer to the surface layer. There is a surface pure Sn layer. Further, since the copper alloy of the invention of the present application contains Zn, the diffusion rate of Cu is low, and the pure Sn layer can exist for a long time.

The copper alloy of the present invention is subjected to reflow plating Sn having a thickness of 0.20 to 3.50 μm. The reflow-plated Sn of a thickness of 0.20 to 3.50 μm means the following plating: the total thickness of the Sn layer remaining after the reflow process and the Cu-Sn compound layer formed by the reflow process is 0.20 to 3.50 μm. The thickness of the Sn layer is 0.10 ~1.60 μm, preferably 0.30 to 1.20 μm, further preferably 0.50 to 1.00 μm. The thickness of the Cu-Sn compound layer is from 0.10 to 1.90 μm, preferably from 0.20 to 1.50 μm, and more preferably from 0.40 to 0.90 μm.

When the thickness of the Sn layer is less than 0.10 μm, it is difficult to obtain a new surface of the Cu-Sn compound layer when it is welded to the battery electrode plate, and the weldability is inferior. Further, the plurality of batteries that are fused with the mark become a battery pack composed of a plurality of batteries, and the mark portion is further welded to the base (through hole structure), and if the Sn layer is thin, solder wettability when soldered to the base Also worse. On the other hand, when it exceeds 1.60 μm, a large amount of Sn is melted at the time of welding, so that it is difficult to fuse the Cu-Sn compound layer and the Ni-plated battery electrode or the Ni battery electrode under the specific conditions generally employed.

If the thickness of the Cu-Sn compound layer is less than 0.10 μm, it is difficult to form a uniform fusion with the electrode surface, so that it is difficult to obtain the target fusion strength. On the other hand, when the thickness of the Cu-Sn compound layer exceeds 1.90 μm, the thickness of the Sn plating tends to be uneven, which causes an obstacle in production. Further, since the thickness of the plating Sn becomes uneven, it becomes difficult to fuse the Cu-Sn compound layer and the Ni-plated battery electrode or the Ni battery electrode under the specific conditions generally employed.

In order to form a Sn-plated Sn of 0.20 to 3.50 μm, Cu is usually plated on the copper alloy in a thickness of 0.05 to 3.0 μm, preferably 0.1 to 1.0 μm. Thereafter, Sn is plated so as to have a thickness of 0.20 to 3.00 μm, preferably 0.23 to 2.60 μm, and then subjected to a reflow process. The usual reflow treatment is performed by inserting a sample into a heating furnace having a temperature of 300 to 600 ° C and a nitrogen (1 vol% or less) environment for 5 to 15 seconds, followed by water cooling.

(F) aspect ratio of crystal grains

If the aspect ratio of the crystal grains is adjusted, the reversibility of the bendability can be further improved. The aspect ratio b/a of the crystal grain in the plate thickness direction b and the rolling parallel direction a in the final product is 0.1 or more, preferably 0.17 to 0.75, more preferably 0.30 to 0.70. Figure 3 is a schematic view of the crystal grains observed in the cross section of the sample.

When the aspect ratio b/a of the crystal grain in the plate thickness direction and the rolling parallel direction is less than 0.1, the strength of the material is high, but the strain is locally concentrated at the time of repeated bending, and the shear band is easily formed, and the repeated bending property is inferior. When b/a exceeds 0.80, although the reverse bending property is good, since it is produced at a low degree of workability, the strength is low, and there is a flaw in the use as a marking material due to vibration or impact.

The average crystal grain size of the present invention is preferably 12 μm or less, and more preferably 7 μm or less. If it is 12 μm or less, an increase in strength is expected, which is preferable.

(G) Manufacturing method

The manufacturing process of the copper alloy of the present invention is basically the same as that of a normal alloy strip, and after melt casting, homogenization annealing, hot rolling, and surface cutting, it is repeatedly produced by repeatedly performing cold rolling and annealing.

The reverse bending property can be further improved by adjusting the following manufacturing conditions.

The end temperature of the hot rolling is preferably from 600 to 750 ° C, and the degree of cold rolling after the final annealing of the product is usually from 10 to 70%, preferably from 10 to 60%. If these are outside the above range, the aspect ratio of the crystal grains is outside the preferred range of the present invention, and the repeated bending property is deteriorated, and the strength is also insufficient.

The intermediate annealing temperature is preferably 5 to 20 seconds at 680 to 780 ° C. If the annealing condition is outside the above range, the aspect ratio is in the present invention. Outside the range, the repeated bending property is deteriorated.

(H) welding conditions

The copper alloy strip of the present invention may be welded to any material, preferably a metal plate having a nickel-plated layer on the surface, and for example, a nickel-plated stainless steel plate or a soft steel plate may be used. Nickel plate. Furthermore, nickel plating is not required in the case where a nickel plate is used for the electrode. The thickness of the electrode material is usually 0.1 to 0.3 mm, which can be varied depending on the actual rechargeable battery, and is not particularly limited.

The welding of the marking material is performed by heat generation from the resistance between the marking plate and the electrode, and the welding quality is affected by the welding current, the energization time, and the pressing pressure. The welding current varies depending on the material and surface state of the welded member and the electrode pressing pressure. Further, in consideration of various elements such as prevention of fusion of the electrodes of the fusion splicer, it is possible to appropriately adjust the current, the pressing pressure of the electrodes, and the like within a range that is normally performed.

[Examples]

The conditions for the measurement performed in the examples are as follows.

[Measurement of Plating Thickness by Electrolytic Thickness Gauge]

The thickness of the Sn-plated layer, the Cu-Sn compound layer, and the Ni-plated layer was measured for the sample after reflow according to JIS H8501 using a CT-1 type electrolytic film thickness meter (manufactured by Electric Co., Ltd.). For the electrolyte solution on which the Sn layer and the Cu-Sn compound layer were plated, an electrolyte R-50 (trade name) manufactured by Kocour Co., Ltd. was used. Further, an electrolyte solution R-54 (trade name) manufactured by Kocour Co., Ltd. was used for the Ni plating layer.

[Conductivity]

For each copper alloy sheet, % IACS was calculated from the volume resistivity obtained by the four-terminal method using a double bridge device in accordance with JIS H0505. When the conductivity is 40% or more, the conductivity is evaluated as "good" ○, and if it is 31% or more and less than 40%, it is evaluated as "in specification" △, and when it is less than 31%, it is evaluated as " Bad" ×.

[Tensile Strength]

For each copper alloy sheet, a tensile test was performed in a direction parallel to the rolling direction, and tensile strength was determined in accordance with JIS Z2241.

[reverse bending]

Four final test pieces having a thickness of 0.15 mm, a width of 10 mm, and a length of 40 mm were prepared in parallel with the direction of the longitudinal direction, and the direction perpendicular to the longitudinal direction of the test piece was used as a bending axis, and 180° tight bending was performed. , restore the bend. In this way, the bending was repeated until the sample was broken, and the number of average fractures (repetitive bending) of the four samples was determined. When the average number of ruptures is 2.5 or more, the reversal bending property is evaluated as "good" ○, and if it is 1.5 or more and less than 2.5 times, it is evaluated as "in specification" Δ, and evaluated when it is less than 1.5 times. It is "bad" ×.

[welding property]

Using a tandem spot welder (for example, a transistor-type resistance welding power supply MDB-4000B (product name) manufactured by Miyachi Corporation and an air-driven head ZH-32 (product name)), a pressing force of 20 N, a welding current of 3.0 kA, and a welding time Under the condition of 10 msec, a soft steel plate (JIS G3101 specification) having a thickness of 3.0 μm and a thickness of 0.3 mm was applied to the copper alloy test piece of the present invention at two points (the electrode spacing was in the range of 10 to 50 mm). , The welding can be performed in the same manner without special problems). The tensile test was carried out by a precision load measuring machine (MODEL-1310VR: product name) manufactured by Aikoh Engineering Co., Ltd. (test speed: 10 mm/min), and the welding strength was measured. When the welding strength is 35 N or more, the weldability is judged to be "best" (A), and if the weld strength is less than 35 N and 25 N or more, it is evaluated as "better" (B), and if the weld strength is less than 25 N and When it is 20N or more, it is evaluated as "good" (C). If the welding strength is less than 20N, it is evaluated as "poor" (D). When it is impossible to weld or unpredictable manufacturing, it is evaluated as "unsmeltable" ( E).

[Ease of recycling]

When the material after the reflow is not refined and is easily recovered and reused as a raw material of the copper alloy, it is judged as "good". ○ In the case where the composition of the copper alloy must be refined for use as a raw material or after the plating of Sn When there is a limitation in the recycling of the corner material, it is evaluated as "partially defective" △, and if it is necessary to refine, it is evaluated as "poor" ×. Further, in the case of Sn plating of Ni/Cu substrate, although Ni is contained in the plating layer, the thickness of Ni plating which is usually performed is thin, so that it can be recovered and reused without refining.

[Aspective ratio of crystal grains]

According to the cutting method of JIS H0501, the crystal grain size of the cross section parallel to the rolling direction and the cross section perpendicular to each other was measured and calculated for each copper alloy sheet. In the cross section parallel to the rolling direction shown in FIG. 3, the crystal grain size in the direction parallel to the rolling surface is measured, and the measured value in the parallel direction is the long diameter a, and the measured value in the thickness direction is the short diameter. b.

(sample preparation)

The electrolytic copper is melted in a high-frequency induction furnace, and the surface of the molten metal is coated with charcoal, and an alloying element is added to adjust the molten liquid to a desired composition. In addition, the composition of the alloying elements other than copper is described in Tables 1 and 2 below. The remainder of the alloy is copper. The casting was carried out at a casting temperature of 1200 ° C, and the obtained ingot was heated at 850 ° C for 3 hours, and then rolled to a thickness of 8 mm by hot rolling, and the hot rolling end temperature was adjusted to 650 ° C or higher. The surface oxide is removed by surface cutting. Thereafter, the film was processed to a thickness of 1.5 mm by cold rolling, and annealed at 700 ° C for 12 seconds, and then appropriately cold-rolled until a specific thickness was reached, and final annealing was performed at 680 ° C for 10 seconds. The annealed copper alloy sheet was cold rolled and processed into a 0.15 mm plate. The intermediate annealing and the final annealing are carried out in a continuous line in an ammonia decomposition gas atmosphere.

A copper alloy strip having different tensile strengths is obtained by changing the degree of processing of cold rolling after final annealing. In general, when the degree of work becomes high, the tensile strength and the 0.2% proof strength increase, the elongation decreases, and the repeated bending property decreases. Moreover, when the degree of work becomes high, the aspect ratio of the crystal grains is lowered. On the other hand, if the degree of processing is low, the tensile strength of the product becomes low and the aspect ratio is still large.

The obtained copper alloy strip was pickled with a 10 mass% sulfuric acid-1 mass% hydrogen peroxide solution to remove the surface oxide film. Electrolytic degreasing with a sample as a cathode in an aqueous alkali solution (current density: 7.5 A/dm ² . Degreaser: sodium hydroxide 10 g/L, sodium carbonate 30 g/L, sodium metasilicate 5 g/L, and the remainder) Water. Temperature: 80 ° C. Time 60 seconds). Acid washing was carried out using a 10% by mass aqueous sulfuric acid solution. After performing Cu plating (plating bath composition: sulfuric acid 60 g/L, copper sulfate 200 g/L, and the remaining portion of water. plating bath temperature: 25 ° C. current density: 5.0 A/dm ² ), further performing Sn plating (plating) Bath composition: stannous sulfate 40g / L, sulfuric acid 60g / L, cresol sulfonic acid 40g / L, gelatin 2g / L, β-naphthol 1g / L, and the remaining part of the water. Bath temperature: 20 ° C. Current Density: 1.5 A/dm ² ). Among them, the thickness of the Sn plating is adjusted by the electrodeposition time (the thickness of the Sn layer before the reflow process is about 1 μm when the electrodeposition time is 2 minutes). As a reflow treatment, a sample was inserted into a heating furnace adjusted to a temperature of 400 ° C and nitrogen gas (oxygen 1 vol% or less) for 5 to 30 seconds, and water-cooled. The test results are shown in Table 1.

Further, in Examples 7 and 10, Ni plating was performed before Cu plating under the following conditions. The composition of the plating bath is: nickel sulfate 250g/L, nickel chloride 45g/L, boric acid 30g/L. Bath temperature: 50 ° C. Current density: 5A/dm ² . Among them, the thickness of the Ni plating was set to 0.30 μm by adjusting the electrodeposition time.

Further, in Example 11, the preparation was carried out under the same conditions as in Example 9 except that Cu was not plated.

Examples 1 to 25 in Table 1 are within the scope of the present invention, and therefore are alloy strips having good tensile strength, electrical conductivity, reversibility of bending, weldability, and ease of recycling. In Example 11 in which Cu was not plated, the copper alloy base material was reacted with the Sn-plated layer by a reflow process to form a Cu-Sn compound layer having a thickness of 0.70 μm. Further, in Examples 22 to 25, the Zn concentration was about 10%, and the Sn concentration was about 0.5%, which was slightly higher, so the conductivity was relatively low at about 32% IACS. In Example 3, the cold rolling degree after the final annealing was more than 70%, and the aspect ratio was lowered within the range of the present invention, but the over-bending property was within the specification. In Example 18, the degree of processing was less than 10% and the aspect ratio was 0.78, but no significant decrease in strength was observed. The processing degree is 15% In Example 19, the aspect ratio was 0.71, and sufficient strength was maintained.

In Comparative Example 26, since commercially available pure copper was used, the tensile strength was inferior, and since the electrical conductivity was extremely high, the amount of heat generated during welding was small and it was impossible to weld. Further, it is necessary to carry out a refining step to recover and reuse the Sn-coated corner material as a raw material, so that the recycling property is also inferior.

In Comparative Examples 27 and 28, the Ni plate used previously was not plated with Sn, and the recycling property of the Ni plate itself was good, but the conductivity was inferior, so that the performance of the battery could not be improved. Further, in the case where Sn is plated, the recycling property is poor. Further, in Comparative Example 27, the degree of processing was low, so that the aspect ratio was relatively high, and the strength was lower than that of Comparative Example 28.

In Comparative Examples 29 to 31, the Zn-free Carson-based alloy copper alloy was not welded, and Comparative Example 29 did not contain Sn. Therefore, the strength was lower than that of Comparative Example 30, and the recovery and recyclability were inferior, and Comparative Example 31 was pulled. The tensile strength is increased, resulting in poor reversibility.

In Comparative Example 32, since Zn and Sn were not contained and Mg was contained, the strength was not lowered but the fusion could not be performed, and the recycling property was also inferior.

Comparative Example 33 contained no Zn and the Sn concentration exceeded the upper limit of the present invention, and the electrical conductivity was low, and the repeated bending property was also poor.

In Comparative Example 34, an example of a precipitation hardening type copper alloy containing a small amount of Zn and containing no Fe and a small amount of P was used. Although the strength was not lowered, the welded rod was corroded and could not be welded, and the recycling property was also inferior.

In Comparative Examples 35 and 36, the Zn concentration was less than 2%, so the strength was relatively low, and the electrical conductivity was too high to cause poor fusion. Further, in Comparative Example 35, since the Sn concentration was low, the recycling property was also inferior.

In Comparative Example 37, the Sn concentration was less than 0.1%, so the strength was lower, the electrical conductivity was too high, and the weldability was poor, and the recyclability was also poor.

The Zn amount and the Sn concentration of Comparative Examples 38, 40 and 41 were within the scope of the present invention, but the thickness of the pure Sn layer in the Sn plating was small and the fusion was poor. On the other hand, in Comparative Example 39, the thickness of the pure Sn layer was large, and when a large amount of Sn was melted at the time of fusion, it was impossible to weld.

The Zn concentration and the Sn concentration of Comparative Example 42 were within the range of the present invention, but the thickness of the Cu-Sn compound layer was small, the tensile strength was small, and the fusion was poor.

The Zn concentration and the Sn concentration of Comparative Example 43 and the layer thickness after reflow are within the scope of the present invention, and the tensile strength is increased, but the workability is high and the aspect ratio of the crystal grains is outside the range of the present invention, so the strength Although high, but the reverse bending is poor.

In Comparative Example 44, since the Sn concentration was more than 0.8%, the electrical conductivity was low, and the repeated bending property and the recycling property were inferior.

In Comparative Examples 45 to 48, the Zn concentration was more than 12%, so that the electrical conductivity was low, and Zn was vaporized during welding, and brittleness of the welded portion was caused, resulting in poor welding or inability to weld. Further, Comparative Example 48 is a general commercial brass having a high Zn concentration, and the degree of processing is relatively low, so that the aspect ratio is relatively high, but the strength is ensured because it is a material which is easy to work harden. However, since Sn is not contained, recycling is poor.

As described above, the present invention has an object of achieving an excellent balance in all items of tensile strength, electrical conductivity, reversibility, and weldability, but this effect cannot be achieved by the comparative example.

[Industrial availability]

The copper alloy strip of the present invention has good balance strength, electrical conductivity, reverse bending property and weldability, and can be preferably used for a battery marking material for charging, and is preferably used in detail. Connect a marking material for a high-performance rechargeable battery such as a Li-ion battery.

1‧‧‧Pure Sn layer

2‧‧‧Cu-Sn compound layer

3‧‧‧ parent metal layer

L‧‧‧The left side of the fusion site

X‧‧‧fused parts

R‧‧‧The right side of the fusion site

10‧‧‧rolling surface

20‧‧‧ plate thickness direction

30‧‧‧Rolling direction (rolling parallel)

a‧‧‧Long Trail

b‧‧‧Short Trail

Fig. 1A is a cross-sectional photograph (FE-SEM image) of the vicinity of the surface before the welding step of the copper alloy strip (Cu-8Zn-0.3Sn) of the present invention.

Fig. 1B is a schematic view of the photograph of Fig. 1A.

Fig. 2 is a cross-sectional photograph of the copper alloy strip of Fig. 1A and a battery electrode (Ni-plated mild steel). The upper portion of the center X is pressed by the electrode rod for welding to perform resistance welding.

Fig. 3 is a schematic view showing crystal grains observed in a cross section of a sample of a copper alloy strip of the present invention.

Claims (4)

A Sn-plated copper alloy strip for marking a battery for charging is a copper alloy strip containing 2 to 12% by mass of Zn and containing 0.1 to 1.5% by mass of Sn, and the balance being composed of copper and unavoidable impurities. The aspect ratio of the crystal grains in the direction parallel to the rolling direction is 0.1 or more, and the number of times of repeated bending in the 180° adhesion bending and bending recovery test is 2.5 or more, and the following reflow plating is performed: Sn after reflowing The thickness of the layer is 0.10 to 1.60 μm, and the thickness of the Cu-Sn compound is 0.10 to 1.90 μm. For example, the Sn-plated copper alloy strip of claim 1 is subjected to Ni/Cu substrate plating or Cu substrate plating. For example, the copper alloy strip of claim 1 or 2 has a conductivity of 31 to 70% IACS. For example, the copper alloy strip of claim 1 or 2 has a tensile strength of 300 to 610 MPa.