JP2010242121A - Cu-Zn-Sn ALLOY PLATE AND TIN-PLATED Cu-Zn-Sn ALLOY STRIP - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Cu-Zn-Sn alloy plate and a tin-plated Cu-Zn-Sn alloy strip having not only excellent pressing processability, but also excellent strength, electrical conductivity, and bending processability. <P>SOLUTION: The Cu-Zn-Sn alloy plate contains 2-12 mass% of Zn, 0.1-1.0 mass% of Sn, and Cu and unavoidable impurities as the remainder, wherein, when the crystal orientation is measured to a depth of 5 μm from the surface of the plate by an X-ray diffraction method, the pole density of shear texture corresponding to a region of α=0±10° (α: an axis perpendicular to the rotation axis of a diffraction goniometer defined in the Schultz method) in a ä111} pole figure is 2-8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Cu—Zn—Sn alloy plate and a Cu—Zn—Sn alloy Sn plating strip suitable for conductive spring materials such as connectors, terminals, relays, and switches.

Terminals, connectors, and the like are formed into a desired shape by pressing a Cu-based alloy plate, but with the miniaturization of electronic components, dimensional accuracy after punching becomes more important than ever. In press working, die wear progresses as the number of punches increases, and burrs increase, so that the maintenance frequency of the die increases as the accuracy of parts increases. Conventionally, such sagging and burrs have often been dealt with by mold adjustment. However, with improvement in dimensional accuracy, a Cu-based material with small sagging and low burrs is required.
Against this background, techniques have been developed that improve press workability by methods such as adjusting the texture and surface structure of Cu-based materials and uniformly dispersing fine compounds. For example, a predetermined processing with a copper-based alloy containing 0.01 to 30 wt% of at least one element selected from Sn, Ni, P, Zn, Si, Fe, Co, Mg, Ti, Cr, Zr, and Al. Disclosed is a technique for cold rolling at a rate of Z% and then performing low temperature annealing at a temperature lower than the recrystallization temperature to adjust the surface X-ray intensity ratio SND to SND = I {220} ÷ I {200} ≧ 10 ing. (Patent Document 1)
Further, a copper-based alloy is disclosed in which the sum of the diffraction intensities of {111} and {222} in the X-ray diffraction intensity of the material cross section is at least twice the {200} diffraction intensity (Patent Document 2). Furthermore, a lead frame for a semiconductor device is disclosed in which Pd is formed in a layer on a copper alloy member containing 5-35 wt% Zn and 0.1-3 wt% Sn (Patent Document 3).

JP 2002-180165 A JP 2001-152303 A JP 11-36027 A

However, if the texture or surface structure is excessively adjusted for the purpose of improving press workability, material properties such as strength, conductivity, and bending workability are deteriorated.
Accordingly, the present invention has been made to solve the above-described problems, and has a Cu-Zn-Sn alloy plate and a Cu-Zn-Sn system that are excellent not only in press workability but also in strength and bending workability. The purpose is to provide an alloy Sn plating strip.

  In order to achieve the above object, the Cu—Zn—Sn alloy plate of the present invention contains 2 to 12% by mass of Zn and 0.1 to 1.0% by mass of Sn, with the balance being Cu and inevitable. It consists of impurities, and when the crystal orientation from the plate surface to a depth of 5 μm is measured by X-ray diffraction method, α = 0 ± 10 ° on the {111} positive pole figure (where α: for diffraction specified in the Schulz method) The pole density of the shear texture corresponding to the region of the axis perpendicular to the rotation axis of the goniometer is 2-8.

The thickness of the surface oxide layer having an oxygen concentration of 1% by mass or more is preferably 0.5 μm or less.
Furthermore, it is preferable to contain 0.005-0.5 mass% in total of at least 1 type or more chosen from the group of Ni, Mg, Fe, P, Mn, and Cr.

  The Cu-Zn-Sn-based alloy Sn plating strip of the present invention is obtained by subjecting the surface of the Cu-Zn-Sn-based alloy plate to Sn plating having a thickness of 0.3 to 2 μm, but is not limited thereto. is not. For example, the Cu-Zn-Sn alloy plate has a Cu layer, a Cu-Sn alloy layer and a Sn layer formed in this order on a Sn plating material, and the Cu-Zn-Sn alloy plate has a Ni layer. The Sn plating material in which each plating layer of a layer, a Cu-Sn alloy layer, and a Sn layer is formed in this order is also included.

  According to the present invention, a Cu—Zn—Sn alloy plate and a Cu—Zn—Sn alloy Sn plating strip excellent not only in press workability but also in strength and bending workability can be obtained.

It is a schematic diagram which shows the extreme density of the shear texture of the copper alloy plate of this invention and the conventional copper alloy rolling plate.

  Hereinafter, a Cu—Zn—Sn alloy plate according to an embodiment of the present invention will be described.

(composition)
[Zn and Sn]
The concentration of Zn in the alloy plate is 2 to 12% by mass, and the concentration of Sn is 0.1 to 1.0% by mass. Zn improves the strength of the alloy plate and decreases the degree of delamination under Sn plating heating. Moreover, Sn has the effect | action which accelerates | stimulates the work hardening in the case of rolling.
When Zn is less than 2%, the hardness of the alloy plate decreases. If Zn exceeds 12%, the Zn content of the oxide film on the surface of the alloy plate increases (Zn rich), and when the alloy plate is processed into a male terminal and mounted in the through hole of the printed circuit board, lead-free solder wets up Deteriorates. When Sn is less than 0.1%, desired work-hardening characteristics cannot be obtained, and when Sn exceeds 1.0%, bending workability and conductivity are deteriorated.
[Other additive elements]
In order to improve the strength, heat resistance, stress relaxation resistance, etc. in the alloy plate, at least one selected from the group of Ni, Mg, P, Fe, Mn and Cr is added in a total amount of 0.005 to 0.00. You may contain 5 mass%. If the total amount of these elements is less than 0.005%, the desired properties cannot be obtained. If the total amount exceeds 0.5% by mass, the desired properties can be obtained, but the conductivity and bending workability are reduced. There are things to do.

(Extreme density of shear texture)
Normally, in cold rolling, crystal lattice rotation proceeds with plastic deformation of the material and a texture is formed, but there is a difference in the texture formed in the surface layer region of the material in contact with the roll and the center of the material during rolling. (Jojo et al., Journal of the Japan Institute of Metals, p33, 36, 1972, edited by Isao Gokyu, “Advances in Metal Plastic Processing”, p499, Corona, 1978). This is because the material is deformed by the biaxial stress that combines the compressive stress in the plate thickness direction and the tensile stress in the rolling direction at the center of the material, whereas the frictional force with the roll is at the material surface layer. This is because the material undergoes shear deformation due to the influence, which is called a surface texture (shear texture) and is distinguished from a rolling texture. According to the above-mentioned document, it has been found that, for example, in an Al plate, a surface texture is formed on both sides of the plate by 30% of the plate thickness under optimum conditions, and the internal structure is rapidly changed by a thin transition layer.

As a result of positively introducing a surface texture (shear texture) in the Cu—Zn—Sn alloy plate, the present inventors have lower burrs and better press workability than conventional Cu alloy plates. I found out that The surface texture is a texture having a {111} orientation as a main component, and a normal rolling texture is a texture having a {110} orientation as a main component. In the uniaxial tensile test of a single crystal, it is known that the {111} orientation has a smaller elongation at break than the {110} orientation. It is considered that there is a difference in elongation in each direction.
In addition, as a method of positively introducing a surface texture (shear texture) into a Cu—Zn—Sn alloy sheet, the present inventors changed the rolling conditions at the time of final cold rolling, and changed the surface texture and rolling. The correlation of conditions was investigated. As a result, by controlling the rolling speed and the viscosity of the rolling oil, a surface texture that has been conventionally formed only in the vicinity of the surface has been successfully formed to a depth of about 10 to 20% of the plate thickness.

In the present invention, when the crystal orientation from the plate surface to a depth of 5 μm is measured by the X-ray diffraction method, α = 0 ± 10 ° on the {111} positive pole figure (where α: for diffraction specified in the Schulz method) The pole density of the shear texture corresponding to the region of the axis perpendicular to the rotation axis of the goniometer is controlled to 2-8.
Here, the reason from the surface of the plate to a depth of 5 μm is that when the relationship between the surface texture and press workability was investigated using the Cu—Zn—Sn-based copper alloy rolled plate of the present invention, it was 5 μm or more. Since a significant difference occurred in press workability when the surface texture was formed, this depth was used as the measurement target.
Further, since the {111} orientation corresponding to the shear texture of the copper alloy of the present invention is a region of α = 0 ± 10 ° in the {111} positive electrode diagram, this region was used as an object for measuring the extreme density.

As described above, the extreme density of the shear texture is measured. And when the rolled plate whose shear texture has an extreme density of 2 to 8 is punched and pressed, it has been found that fewer burrs are generated after punching than the conventional material.
If the extreme density of the shear texture having a depth of 5 μm from the plate surface is less than 2, the shear texture is not sufficiently formed, so that the burr becomes high and the press workability is not improved. On the other hand, it is industrially difficult for the polar density of the shear texture to exceed 8, and the upper limit of the polar density was set to 8.
In addition, when the pole density is in the range of 2 or more and 3 or less, the press workability improves as the pole texture of the shear texture increases (the burr decreases), but when the pole density exceeds 3, the press workability is increased. The degree of improvement is slowed down, and when the pole density exceeds 5, no difference in press workability is observed. Further, in order to obtain a high pole density exceeding 5, it is necessary to use a rolling oil having a high viscosity and increase the rolling speed, and the surface roughness of the material tends to increase. On the other hand, when the pole density exceeds 4.5, wrinkles are generated in the bent portion. Therefore, the pole density is preferably 2.2 or more and 5 or less, and more preferably 2.5 or more and 4.5 or less.

  In the case of a conventional rolled copper alloy plate, the portion having a high extreme density of the shear texture is limited to the extreme surface of the plate, so that press workability is not sufficient. FIG. 1 schematically shows the extreme density of the shear texture of the copper alloy plate of the present invention and a conventional copper alloy plate. Also in conventional copper alloy rolling, the pole density of the shear texture on the pole surface of the plate is 2 or more, but the pole density rapidly decreases as it goes inside, and the pole density is 2 at a depth of 5 μm from the plate surface. Less than.

As a method of controlling the extreme density of the shear texture from the plate surface to a depth of 5 μm to 2 to 8, recrystallization annealing is performed at an annealing temperature according to the alloy composition, and the roll and copper alloy at the time of final cold rolling A method for increasing the frictional force with the rolling material is mentioned. Specifically, at the time of final cold rolling, 1) increase the viscosity of the rolling oil, 2) increase the roughness of the rolling roll, and 3) increase the rolling speed (reducing the roll diameter). It is done.
Usually, the viscosity of the rolling oil at the time of cold rolling is about 0.03 to 0.06 cm ² / s, and the viscosity of the rolling oil at the time of the final cold rolling is set to 0.06 cm ² / s or more, thereby shearing The extreme density of the texture can be 2-8.

(Surface oxide layer)
In the copper alloy sheet of the present invention, the thickness of the surface oxide layer having an oxygen concentration of 1% by mass or more is preferably 0.5 μm or less. Usually, the oxygen concentration of the parent phase is about 0.001 to 0.01% by mass, and the portion where the oxygen concentration is 1% by mass or more contains sufficient oxygen and functions as a layer that affects press workability. It is.
As a result of examining the phenomenon that causes a difference in press workability even in a sample produced under the same rolling conditions, the inventors have found that the surface oxide layer formed by annealing performed before the sample is processed into a plate or a strip is thick. Then, the knowledge that press workability deteriorates was obtained. And by controlling the atmosphere, temperature, and time during annealing, the thickness of the surface oxide layer was optimized, and the press workability was improved.
If the thickness of the surface oxide layer having an oxygen concentration of 1% by mass or more exceeds 0.5 μm, the mold may be worn to increase the clearance, increase the burrs, and decrease the press workability. This is thought to be because the surface oxide layer is harder than the Cu base material and causes wear of the mold. The thinner the surface oxide layer, the less frequent the friction between the mold steel and the oxide layer during material punching. , The press workability is improved.
In addition, it is preferable that the oxygen concentration in the annealing atmosphere is 0.2% or less because the thickness of the surface oxide layer is reduced.

(Manufacturing)
The copper alloy plate of the present invention can be produced, for example, as follows. First, an ingot is prepared by melting a composition in which electrolytic copper or oxygen-free copper is used as a main raw material and adding the above chemical components and the like in a melting furnace. For example, the ingot is processed in the order of homogenization annealing, hot rolling, face milling, cold rolling, recrystallization annealing, and final cold rolling to obtain a rolled sheet. When performing Sn plating, after removing the rolling oil adhering to a rolled sheet by electrolytic degreasing, it pickles with, for example, 10% sulfuric acid aqueous solution, and Sn plating is performed.

  The copper alloy plate of the present invention can be in various forms such as strips and foils. By processing the copper alloy strip of the present invention, it can be applied to electrical parts such as connectors, pins, terminals, relays and switches. The connector can be applied to all known forms and structures, but is usually used as a male terminal of a connector composed of a male (jack, plug) and a female (socket, receptacle).

<Example>
EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.

1. Preparation of Sample After melting electrolytic copper in a high frequency induction furnace and coating the surface of the molten metal with charcoal, Zn (3 mass%) and Sn (0.2 mass%) were added to adjust the molten metal to a desired alloy composition. Thereafter, casting was performed at a casting temperature of 1200 ° C., and the obtained ingot was heated at 850 ° C. for 3 hours, and then hot-rolled to a plate thickness of 8 mm, and the oxide scale generated on the surface was removed by chamfering. Thereafter, the processing proceeded in the order of cold rolling, recrystallization annealing, and cold rolling, and finally finished into a 0.64 mm rolled plate. Recrystallization annealing was performed in ammonia decomposition gas, and the annealing time was 30 minutes. Table 1 shows recrystallization annealing conditions, final cold rolling conditions (rolling speed and rolling oil viscosity), and obtained material properties. The extreme density of the shear texture was adjusted by changing the recrystallization conditions and the final cold rolling conditions.

2. Measurement of polar density of shear texture Using an X-ray diffractometer (RINT2500, manufactured by Rigaku Corporation), {111} positive electrode points of each sample were measured by a reflection method to produce {111} positive electrode dot diagrams. However, in the reflection method, measurement becomes difficult when the incident angle of the X-ray with respect to the sample surface becomes shallow. Therefore, the angle ranges that can be actually measured are 0 ° ≦ α ≦ 75 ° and 0 ° ≦ β ≦ 360 on the positive electrode diagram. ° (where α is an axis perpendicular to the rotational axis of the diffraction goniometer defined in the Schulz method, β is an axis parallel to the rotational axis).
In the measurement, the X-ray intensity at 16 × 73 = 1168 points was measured by scanning the angle range described above with α and β rotation intervals Δα and Δβ set to 5 °. At this time, the strength of the texture on the positive point diagram was normalized by assuming that the texture has no texture (that is, the crystal orientation is random) as 1. Assuming that the crystal orientation was random, {111} positive electrode point measurement of a copper powder sample was performed, and this was set to 1.
As the X-ray irradiation conditions, a Co tube was used, the tube voltage was set to 30 kV, the tube current was set to 100 mA, and the conditions were set so that the X-rays penetrated to a depth of 5 μm from the plate surface.
As described above, the polar density of the crystal orientation in the range of α = 0 ° ± 10 ° on the {111} positive electrode diagram corresponding to the shear texture is measured, and the maximum value of the polar density in this range is It was defined as the extreme density of the shear texture.

3. Burr Height For each sample, a die clearance was set to 10%, a lead having a length of 30 mm and a width of 0.5 mm was punched at a punching speed of 250 spm, and a cross section of the punched material was photographed with a confocal microscope. In the photographed image, the height difference between the highest part on the punching end surface side and the lowest part was regarded as the burr height.
If the burr height was 15 μm or less, it was judged that the burr was low and good.

4). Bending workability The bending workability of each sample was evaluated according to the Japan Copper and Brass Association (JBMA) technical standard T307 (1999). The bending radius was r = 0.3, and Good Way bending was performed.
Corresponding to the five grades A to E of the technical standard, the following criteria were used.
○: A (good) of the technical standard △: B (small wrinkle) and C (large wrinkle) of the technical standard
×: D (small crack) and E (large crack) of the same technical standard

5). Tensile strength Each sample was subjected to a tensile test in accordance with JISZ2241 in a direction parallel to the rolling direction to determine the tensile strength. If the tensile strength is 450 MPa or more, it is good as a spring material.

  The obtained results are shown in Table 1.

As is clear from Table 1, in Invention Examples 1 to 9, burrs due to press working were low and bending workability was good. Therefore, the press workability was excellent and the tensile strength was high. However, in the case of Invention Example 9 in which the thickness of the surface oxide layer having an oxygen concentration of 1% by mass or more exceeded 0.5 μm, the burrs were higher than those of the other Invention Examples, but there was no practical problem.
On the other hand, in the case of Comparative Example 1 in which the rolling speed during the final cold rolling was less than 170 mpm, the extreme density of the shear texture was less than 2, the burr was high, and the press workability was deteriorated.
Also in the case of Comparative Example 2 in which the viscosity of the rolling oil at the time of final cold rolling is less than 0.06 cm ² / s, the extreme density of the shear texture is less than 2, the burr is high, and the press workability is deteriorated. .

In Comparative Example 3 where the recrystallization annealing temperature was less than 380 ° C., the extreme density of the shear texture was less than 2, the burr was high, and the press workability was deteriorated. This is because, since the recrystallization annealing temperature is low, sufficient recrystallization does not occur, and a desired shear texture cannot be obtained due to the influence of the rolling texture formed before the recrystallization annealing.
In the case of Comparative Example 4 in which the recrystallization annealing temperature exceeded 430 ° C., the extreme density of the shear texture was 2 or more, but the recrystallization annealing temperature was too high, so that the crystal grain size was coarsened and the tensile strength was increased. Decreased.
The appropriate recrystallization temperature range varies depending on the composition of the copper alloy plate, and is not limited to the temperature range of 380 to 430 ° C. applied to the inventive examples.

After electrolytic copper was melted in a high frequency induction furnace and the surface of the molten metal was coated with charcoal, an alloy element was added so as to have the composition shown in Table 2, and the molten metal was adjusted to a desired alloy composition. Thereafter, casting was performed at a casting temperature of 1200 ° C., and the obtained ingot was heated at 850 ° C. for 3 hours, and then hot-rolled to a plate thickness of 8 mm, and the oxide scale generated on the surface was removed by chamfering. Thereafter, the processing proceeded in the order of cold rolling, recrystallization annealing, and cold rolling, and finally finished into a 0.64 mm rolled plate. The recrystallization annealing was performed in ammonia decomposition gas, the oxygen concentration was 0.1%, and the annealing temperature shown in Table 3 was performed for 30 minutes. The rolling speed of finish rolling was 200 mpm, and rolling oil having a viscosity of 0.1 cm ² / s was used.

About the obtained sample, evaluation similar to Example 1 was performed, and also the following solder wettability evaluation was performed.
<Solder wetting>
The following test simulated the solder wetting of lead-free solder when terminals were mounted in through holes on the printed circuit board.
First, each copper rolled plate obtained in Example 2 was subjected to Sn plating of 1.2 μm, and then pressed into a strip shape having a plate width of 0.64 mm and a length of 30 mm, and a press fracture surface was generated on the end surface. After that, it was exposed to an atmosphere having a relative humidity of 85% and a temperature of 85 ° C. for 24 hours (aging treatment). Next, the strip plate was dipped in a lead-free solder (Sn-3% Ag-0.5% Cu) at 250 ° C. for 10 seconds and then pulled up. When the sample is immersed in lead-free solder, the solder rises from the immersion interface as the solder gets wet with the sample. Therefore, the solder wet area ratio (S) can be calculated by the following formula.
S (%) = (total area of the solder adhesion part after immersion) / (initial area of the solder immersion part during immersion) × 100
When S exceeds 100%, it indicates that a solder wetting phenomenon has occurred. When S is 110% or more, the above-mentioned solder wetting property is improved. Therefore, the solder wettability was evaluated according to the following criteria.
○: S ≧ 110%
X: S <110%

  The obtained results are shown in Table 3.

As shown in Table 3, in Invention Examples 10 to 25, the press workability was excellent, the tensile strength was high, and the solder wettability was also good.
On the other hand, in the case of the comparative example 5 whose Zn density | concentration is less than 2 mass%, tensile strength fell. In the case of Comparative Example 6 in which the Zn concentration exceeded 12% by mass, both the press workability and the strength were good, but the solder wettability deteriorated. In the case of Comparative Example 7 in which the Sn concentration was less than 0.1% by mass, the work hardening during rolling was insufficient, and the tensile strength was reduced. In the case of Comparative Example 8 in which the Sn concentration exceeded 1.0 mass%, the bending workability was lowered.

Claims (4)

It contains 2 to 12% by mass of Zn and 0.1 to 1.0% by mass of Sn, the balance is made of Cu and inevitable impurities, and the crystal orientation from the plate surface to a depth of 5 μm is measured by X-ray diffraction method. Then, the polar density of the shear texture corresponding to the region of α = 0 ± 10 ° (where α is an axis perpendicular to the rotational axis of the diffraction goniometer defined in the Schulz method) on the {111} positive electrode diagram is 2 Cu-Zn-Sn alloy plate which is ~ 8. The Cu-Zn-Sn alloy plate according to claim 1, wherein the thickness of the surface oxide layer having an oxygen concentration of 1% by mass or more is 0.5 µm or less. The Cu-Zn-Sn alloy plate according to claim 1 or 2, further comprising 0.005 to 0.5 mass% in total of at least one selected from the group consisting of Ni, Mg, Fe, P, Mn and Cr. . A Cu-Zn-Sn-based alloy Sn-plated strip obtained by performing Sn plating with a thickness of 0.3 to 2 µm on the surface of the Cu-Zn-Sn alloy plate according to any one of claims 1 to 3.

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