COPPER ALLOY SHEET WITH SN COATING LAYER FOR A FITTING TYPE CONNECTION TERMINAL AND A FITTING TYPE CONNECTION TERMINAL

Abstract

A copper alloy sheet with a Sn coating layer comprises a base material made of CuNiSi system copper alloy. Formed on the base material is a Ni coating layer having an average thickness of 0.1 to 0.8 m. Formed on the Ni coating layer is a CuSn alloy coating layer having an average thickness of 0.4 to 1.0 m. Formed on the CuSn alloy coating layer is an Sn coating layer having average thickness of 0.1 to 0.8 m. A material surface is subject to reflow treatment and has arithmetic mean roughness Ra of 0.03 m or more and less than 0.15 m in both a direction parallel to the rolling direction and a direction perpendicular to the rolling direction. An exposure rate of the CuSn alloy coating layer to the material surface is 10 to 50%. A fitting type connection terminal requiring low insertion force can be obtained at a low cost.

Claims

1. A copper alloy sheet, comprising: a base material comprising CuNiSi system copper alloy; a Ni coating layer formed on the base material and having an average thickness of 0.1 to 0.8 m; a CuSn alloy coating layer formed on the Ni coating layer and having an average thickness of 0.4 to 1.0 m; and an Sn coating layer formed on the CuSn alloy coating layer and having an average thickness of 0.1 to 0.8 m; wherein the copper alloy sheet has a surface which has been subject to reflow treatment and has arithmetic mean roughness Ra of 0.03 m or more and less than 0.15 m in both a direction parallel to a rolling direction and a direction perpendicular to the rolling direction, and wherein an exposure rate of the CuSn alloy coating layer to the surface is 10 to 50%.

2. The copper alloy sheet according to claim 1, wherein the CuSn alloy coating layer is exposed to the surface and linearly extends in the direction parallel to the rolling direction.

3. The copper alloy sheet according to claim 2, wherein the base material has a surface buffed along the direction parallel to the rolling direction.

4. The copper alloy sheet according to claim 1, wherein the base material has a surface which has arithmetic mean roughness Ra in the direction parallel to the rolling direction of 0.05 m or more and less than 0.20 m and arithmetic mean roughness Ra in the direction perpendicular to the rolling direction of 0.07 m or more and less than 0.20 m.

5. The copper alloy sheet according to claim 1, wherein the CuNiSi system copper alloy includes Cu, 1 to 4% by mass of Ni and 0.2 to 0.9% by mass of Si such that a Ni/Si mass ratio is 3.5 to 5.5.

6. The copper alloy sheet according to claim 5, wherein the CuNiSi system copper alloy further includes at least one of Sn: 3% by mass or less, Mg: 0.5% by mass or less; Zn: 2% by mass or less; Mn: 0.5% by mass or less; Cr: 0.3% by mass or less; Zr: 0.1% by mass or less; P: 0.1% by mass or less; Fe: 0.3% by mass or less; and Co: 1.5% by mass or less.

7. The copper alloy sheet according to claim 6, wherein the CuNiSi system copper alloy includes Co, and wherein a total amount of Ni and Co in the CuNiSi system copper alloy is 1 to 4% by mass at (Ni+Co)/Si mass ratio of 3.5 to 5.5.

8. A fitting type connection terminal, comprising: the copper alloy sheet according to claim 1, wherein an insertion direction is set in the direction perpendicular to the rolling direction.

9. The fitting type connection terminal according to claim 8, wherein the CuSn alloy coating layer is exposed to the surface and linearly extends in the direction parallel to the rolling direction.

10. The fitting type connection terminal according to claim 8, wherein the base material has a surface buffed along the direction parallel to the rolling direction.

11. The fitting type connection terminal sheet according to claim 8, wherein the base material has a surface which has arithmetic mean roughness Ra in the direction parallel to the rolling direction of 0.05 m or more and less than 0.20 m and arithmetic mean roughness Ra in the direction perpendicular to the rolling direction of 0.07 m or more and less than 0.20 m.

12. The fitting type connection terminal according to claim 1, wherein the CuNiSi system copper alloy includes Cu, 1 to 4% by mass of Ni and 0.2 to 0.9% by mass of Si such that a Ni/Si mass ratio is 3.5 to 5.5.

13. The fitting type connection terminal according to claim 12, wherein the CuNiSi system copper alloy further includes at least one of Sn: 3% by mass or less, Mg: 0.5% by mass or less; Zn: 2% by mass or less; Mn: 0.5% by mass or less; Cr: 0.3% by mass or less; Zr: 0.1% by mass or less; P: 0.1% by mass or less; Fe: 0.3% by mass or less; and Co: 1.5% by mass or less.

14. The fitting type connection terminal according to claim 13, wherein the CuNiSi system copper alloy includes Co, and wherein a total amount of Ni and Co in the CuNiSi system copper alloy is 1 to 4% by mass at (Ni+Co)/Si mass ratio of 3.5 to 5.5.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a SEM composition image of a surface of a sample material of Embodiment No. 3;

[0028] FIG. 2 is a binarized composition image of the sample material; and

[0029] FIG. 3 is a conceptual illustration of a friction coefficient measurement apparatus.

DETAILED DESCRIPTION OF THE INVENTION

[0030] In the following, a copper alloy sheet with Sn coating layer of the present invention are described more concretely.

[CuNiSi System Copper Alloy Sheet] (Copper Alloy Composition)

[0031] As a base material of a copper alloy sheet with Sn coating layer of the present invention, a CuNiSi system copper alloy sheet generally known in the name of Corson alloy is used. A desirable composition is Ni: 1 to 4% by mass; Si: 0.2 to 0.9% by mass, and the balance consisting of Cu and inevitable impurities. If necessary, the composition may further contain any one or more of Sn: 3% by mass or less, Mg: 0.5% by mass or less, Zn: 2.0% by mass or less, Mn: 0.5% by mass or less, Cr: 0.3% by mass or less, Zr: 0.1% by mass or less, P: 0.1% by mass or less; Fe: 0.3% by mass or less; and Co: 1.5% by mass or less. The composition itself is known well and there are many compositions practically used as a fitting type connection terminal, for example, C64725 (Cu-2% Ni-0.5% Si-1% Zn-0.5% Sn), C64760 (Cu-1.8% Ni-0.4% Si-1.1% Zn-0.1% Sn), C64785 (Cu-3.2% Ni-0.7% Si-0.5% Sn-1% Zn), C70250 (Cu-3.0% Ni-0.65% Si-0.15% Mg), and C70350 (Cu-1.5% Ni-1.1% Co-0.6% Si) that are standardized by ASTM.

[0032] The above-mentioned composition will be briefly described in the following.

[0033] Ni and Si are elements which improve the strength by forming a precipitate of Ni.sub.2Si. The Ni content is 1 to 4% by mass and the Si content is desirably in the range of 0.2 to 0.9% by mass so as to give a Ni/Si mass ratio of 3.5 to 5.5 corresponding to the Ni content. If the Ni content is less than 1% by mass or the Si content is less than 0.2% by mass, the strength becomes insufficient. If the Ni content exceeds 4% by mass or the Si content exceeds 0.9% by mass, Ni or Si is crystallized or precipitated at the time of casting to lower the hot workability. In the case where the Ni/Si mass ratio is less than 3.5 or exceeds 5.5, the excess Ni or Si forms a solid solution to lower conductivity. The Ni content is preferably 1.7 to 3.9% by mass. The Ni/Si mass ratio is preferably 4.0 to 5.0.

[0034] Sn improves the strength characteristic and anti-stress relief characteristic by forming a solid solution in the structure, but if its content exceeds 3% by mass, the conductivity and bending processability are deteriorated. Consequently, in the case where Sn is added, the content is adjusted to 3% by mass or less and preferably 2.0% by mass or less.

[0035] Mg improves the strength characteristic by forming a solid solution in the structure, but if its content exceeds 0.5% by mass, the bending processability and conductivity are deteriorated. Consequently, in the case where Mg is added, the content is adjusted to 0.5% by mass or less and preferably 0.3% by mass or less.

[0036] Cr improves the hot workability, but if its content exceeds 0.3% by mass, a precipitate is produced to lower the bending processability. Consequently, in the case where Cr is added, the content is adjusted to 0.3% by mass or less and preferably 0.1% by mass or less.

[0037] Mn improves the hot workability, but if its content exceeds 0.5% by mass, the conductivity is reduced. Consequently, in the case where Mn is added, the content is adjusted to 0.5% by mass or less and preferably 0.3% by mass or less.

[0038] Zn improves the peeling resistance of the Sn plating, but if its content exceeds 2.0% by mass, the bending processability and conductivity are deteriorated. Consequently, in the case where Zn is added, the content is adjusted to 2.0% by mass or less and preferably 1.5% by mass or less.

[0039] Zr and Fe have an action of refining crystal grains, but if their contents exceed 0.1% by mass and 0.3% by mass, respectively, the bending processability is deteriorated. Consequently, in the case where Zr and Fe are added, the contents are adjusted to 0.1% by mass or less and 0.3% by mass or less, respectively, and preferably 0.05% by mass or less and 0.1% by mass or less, respectively.

[0040] P is an element which contributes mainly to the improvement of soundness (deacidification and molten metal flow) for an ingot. Consequently, in the case of improving the soundness for an ingot, P is added. If P is added in a content of 0.1% or more, a NiP intermetallic compound is easily precipitated, agglomerated, and coarsened to cause cracking at the time of hot working and lowering of the workability. Consequently, in the case where P is added, the content is adjusted to 0.1% by mass or less and preferably 0.03% by mass or less.

[0041] Co is an element for producing a NiCoSi type precipitate to further improve the strength of the copper alloy. However, if the content of Co exceeds 1.5% by mass, the precipitation amount of the compound in an ingot is increased and it tends to cause cracking of an ingot, heat cracking at the time of hot rolling, and heat stretching cracking. Consequently, the Co content is adjusted to 1.5% by mass or less. In the case where Co is added, the Co content is preferably 0.05% by mass or more. It is preferable that the composition is determined so as to adjust the total content of Ni and Co to 1 to 4% by mass and the (Ni+Co)/Si mass ratio to 3.5 to 5.5 and preferably 4.0 to 5.0.

(Method for Producing Copper Alloy Sheet)

[0042] A CuNiSi system copper alloy sheet according to the present invention can be produced according to a conventional method by carrying out steps of melting/casting, soaking, hot rolling, quenching after hot rolling, cold rolling, recrystallizing accompanied with solubilization, cold rolling, and aging. In the cold rolling, unlike the invention described in JP-A No. 2006-183068, there is no need to use surface-roughened work rolls and rolls with normal surface roughness may be used. In order to increase the strength, if necessary, steps of recrystallizing accompanied with solubilization, aging, and cold rolling may be selected. Further, in order to obtain a good spring property, low temperature annealing may be carried out at the last.

[0043] Since a CuNiSi system copper alloy contains a relatively large amount of Si and a stiff oxide film containing Si oxide is formed on the surface, a grinding step for removing an oxide film on the surface is carried out after the recrystallization treatment, aging treatment, and low temperature annealing. A rotating buff is preferably used for this grinding step and is commonly used. A rotating buff is arranged in a manner that its rotary shaft is perpendicular to the rolling direction and the buff is pushed against the surface of the CuNiSi system copper alloy sheet which is continuously moved in the longitudinal direction.

[0044] The CuNiSi system copper alloy sheet obtained by the above-mentioned method is not at all different from a common CuNiSi system copper alloy sheet. Similarly, regarding the surface roughness, the arithmetic mean roughness Ra in the direction parallel to the rolling direction is 0.05 m or more and less than 0.20 m and more generally 0.07 m or more and 0.15 m or less and the arithmetic mean roughness Ra in the direction perpendicular to the rolling direction is 0.07 m or more and less than 0.20 m and more generally 0.10 m or more and 0.17 m or less.

[Ni, Cu, and Sn Plating Layers]

[0045] Ni plating, Cu plating, and Sn plating are carried out in this order on the surface of the CuNiSi system copper alloy sheet produced by the above-mentioned steps and subsequently, reflow treatment is carried out.

[0046] Since the average thickness of the Ni plating layer is not changed even after reflow treatment, the Ni plating layer may be formed to have an average thickness in the range of 0.1 to 0.8 m. The Cu plating layer and the Sn plating layer may be formed to respectively have a proper average thickness in a manner that the Cu plating layer disappears after the reflow treatment, the CuSn alloy coating layer with an average thickness of 0.4 to 1.0 m is formed and the Sn coating layer with an average thickness of 0.1 to 0.8 m remains. Plating baths and plating conditions for the Ni plating, Cu plating, and Sn plating may be those as described in JP-A No. 2004-68026.

[0047] The reflow treatment condition may be the Sn melting temperature to 600 C. for 3 to 30 seconds, preferably 400 to 600 C. for 3 to 7 seconds. The cooling subsequent to the reflow treatment is water cooling. This is common as the reflow treatment condition and the cooling condition after the reflow treatment.

[Surface Coating Layer after Reflow Treatment]

(Ni Coating Layer)

[0048] The Ni layer in the surface coating layer is effective for suppressing diffusion of Cu of the base material in the Sn coating layer under a high temperature environment. However, if the average thickness of the Ni coating layer is less than 0.1 min, the diffusion suppression effect is slight and Cu oxide is formed in the surface of the Sn coating layer to increase the contact resistance. On the other hand, if the average thickness of the Ni coating layer exceeds 0.8 m, cracks are formed by bending and the processability of forming a connection terminal is reduced. Consequently, the average thickness of the Ni coating layer is adjusted to 0.1 to 0.8 m and preferably 0.1 to 0.6 m.

(CuSn Alloy Coating Layer)

[0049] Since the CuSn alloy coating layer in the surface coating layer is hard, exposure of this coating layer to the surface and existence under the Sn coating layer increase the hardness of the surface and are effective for reducing the insertion force at the time of terminal insertion. Further, the CuSn alloy coating layer is effective for suppressing diffusion of Ni of the Ni coating layer in the Sn coating layer. However, if the average thickness of the CuSn alloy coating layer is less than 0.4 m, diffusion of Ni in a high temperature environment cannot be suppressed and diffusion of Ni in the surface of the Sn coating layer is promoted. Accordingly, the Ni coating layer is broken and Cu of the base material is diffused in the surface of Sn coating layer through the broken Ni coating layer to increase the contact resistance, and the interface between the base material and the surface coating layer becomes brittle to cause separation of the surface coating layer. On the other hand, if the average thickness of the CuSn alloy coating layer exceeds 1.0 m, cracks are formed by bending and the processability of forming a connection terminal is reduced. Consequently, the average thickness of the CuSn alloy coating layer is adjusted to 0.4 to 1.0 m and preferably 0.4 to 0.8 m.

(Sn Coating Layer)

[0050] If the Sn coating layer becomes thick, the insertion force is increased and therefore, the average thickness of the Sn coating layer is preferably 0.8 m or less. On the other hand, if the average thickness of the Sn coating layer is less than 0.1 m, the Cu oxide amount in the material surface due to heat diffusion such as high temperature oxidation is increased and thus the contact resistance tends to be increased and the corrosion resistance is deteriorated. Consequently, the average thickness of the Sn coating layer is adjusted to 0.1 to 0.8 m.

(Exposure Rate of CuSn Alloy Coating Layer to Material Surface)

[0051] If reflow treatment is carried out on a copper alloy sheet as a base material after being subjected to the surface plating with Ni, Cu, and Sn in this order according to the invention described in JP A No. 2004-68026, the surface coating layer composed of the Ni coating layer, the CuSn alloy coating layer, and the Sn coating layer is formed on the surface of the base material. It is generally supposed that the Sn coating layer covers the entire surface of the surface coating layer and thus the CuSn alloy coating layer is not exposed to the material surface in the case where the surface roughness of the base material is a normal value (unlike that of the invention described in JP A No. 2006-183068, the surface roughness is not made intentionally large).

[0052] However, in the case where a CuNiSi system copper alloy sheet is used as a base material, even if the surface roughness of the base material is a normal value, the CuSn alloy coating layer may be exposed to the material surface and still more, in the case where the CuSn alloy coating layer is exposed, the layer is exposed so as to linearly extend in the rolling direction. The reason for occurrence of such a phenomenon has not been made clear, but the inventors of the present invention presume that the fine unevenness (traces by rolling and ground traces by buffing) formed on the surface of the sheet or an oxide film mainly containing Si oxide remaining unevenly without being removed by the buffing results in increase of the production amount and growing speed of the CuSn alloy at the time of reflow treatment or local decrease of the barrier effect of the Ni plating layer and as a result, the CuSn alloy coating layer formation is locally promoted and the layer is exposed linearly to the material surface, since the CuSn alloy coating layer is exposed linearly along the rolling direction.

[0053] The exposure rate of the CuSn alloy coating layer to the material surface is the area rate of the CuSn alloy coating layer exposed to the material surface per unit surface area represented by percentage, and it is adjusted to 10 to 50% in the present invention. The Sn coating layer remains in the remaining 50 to 90% of the material surface. If the exposure rate of the CuSn alloy coating layer to the material surface is less than 10%, decrease of the friction coefficient is insufficient so that the effect of decreasing the insertion force of a terminal cannot be caused sufficiently. On the other hand, if the exposure rate of the CuSn alloy coating layer to the material surface exceeds 50%, the Cu oxide amount in the material surface due to time passage or corrosion is increased and it tends to increase the contact resistance and make it difficult to keep the electric characteristics (low contact resistance) after a long duration at a high temperature.

[0054] The exposure rate of the CuSn alloy coating layer to the material surface is higher as the average thickness of the Sn coating layer is smaller and is lower as it is larger. For keeping the exposure rate within the range of 10 to 50%, the average thickness of the Sn coating layer is preferably in the range of 0.1 to 0.8 m.

(Maximum Width of Sn Coating Layer in Direction Perpendicular to Rolling Direction)

[0055] In consideration of the size of a contact part of a recent miniaturized connection terminal, if the width of the Sn coating layer observed on the material surface is 200 m or more in the direction perpendicular to the rolling direction, the effect of decreasing the insertion force is difficult to be obtained. Consequently, in the copper alloy sheet with Sn coating layer of the present invention, the maximum width of the Sn coating layer in the direction perpendicular to the rolling direction is preferably 200 m or less. The maximum width of the Sn coating layer in the direction perpendicular to the rolling direction is larger as the average thickness of the Sn coating layer is smaller and smaller as it is thicker. For keeping the maximum width of 200 m or less, the average thickness of the Sn coating layer is preferably in the range of 0.1 to 0.8 m.

(Arithmetic Mean Roughness Ra of Material Surface)

[0056] In the case where the copper alloy sheet with Sn coating layer of the present invention is produced by carrying out Ni plating, Cu plating, and Sn plating in this order on the above-mentioned CuNiSi system copper alloy sheet as a base material, and subsequently carrying out reflow treatment for forming the above-mentioned Ni coating layer, CuSn alloy coating layer, and Sn coating layer on the surface of the base material, the surface roughness of the material surface is adjusted to keep the arithmetic mean roughness Ra approximately within the range of 0.03 m or more and less than 0.15 m in both a direction parallel to the rolling direction and a direction perpendicular to the rolling direction. The surface roughness is almost same as the surface roughness of the copper alloy sheet with Sn coating layer obtained in the case of applying the invention described in JP A No. 2004-68026 to a copper alloy sheet other than a CuNiSi system copper alloy sheet.

[Fitting Type Connection Terminal]

[0057] Because of exposure of the CuSn alloy coating layer linearly in the direction parallel to the rolling direction, the copper alloy sheet with Sn coating layer of the present invention has lower friction coefficient measured in the direction perpendicular to the rolling direction than that measured in the direction parallel to the rolling direction. Consequently, the fitting type connection terminal is preferably press-punched and formed in a manner that the insertion direction is the direction perpendicular to the rolling direction of the copper alloy sheet with Sn coating layer.

Embodiment 1

[0058] A CuNiSi system copper alloy sheet with a thickness of 0.25 mm was produced by carrying out steps of melting/casting, soaking, hot rolling, quenching after hot rolling, cold rolling, recrystallizing accompanied with solubilization, cold rolling, and aging for a CuNiSi system copper alloy containing Ni: 1.8% by mass, Si: 0.4% by mass, Zn: 1.0% by mass, Sn: 0.2% by mass, Mn: 0.05% by mass, Mg: 0.04% by mass, and the balance consisting of Cu and inevitable impurities. After the recrystallization treatment accompanied with solubilization and aging treatment, grinding by a rotating buff was carried out. The rotating buff was arranged in a manner that the rotary shaft was perpendicular to the rolling direction and the buff was pushed against the surface of the copper alloy sheet moving continuously in the longitudinal direction.

[0059] The surface roughness of the produced CuNiSi system copper alloy sheet (base material) was measured as follows. The material of the rotating buff, the number of abrasive grain, and the rotating speed of the rotating buff were changed to adjust the surface roughness (Ra) of copper alloy sheets (base materials) of Nos. 1 to 13.

[Measurement of Surface Roughness of Copper Alloy Sheet]

[0060] The surface roughness of each copper alloy sheet was measured by a contact type surface roughness measurement meter (Surfcom 1400, manufactured by Tokyo Seimitsu Co., Ltd.) according to JIS B0601-1994. The surface roughness measurement condition was a cutoff value of 0.8 mm; a standard length of 0.8 mm; an evaluation length of 4.0 mm; a measurement speed of 0.3 mm/s; and a stylus tip radius of 5 m R. The surface roughness measurement direction was the direction parallel to the rolling direction (//) and the direction perpendicular to the rolling direction ().

[0061] Then, Ni plating, Cu plating, and Sn plating were carried out in this order for the surface of each copper alloy sheet under the following conditions and subsequently reflow treatment was carried out to give sample materials (copper alloy sheets with Sn coating layer) of Nos. 1 to 13 as shown in Table 1. Ni plating was omitted for No. 13.

[0062] Ni plating was carried out by using a plating bath containing 240 g/L of NiSO.sub.4/6H.sub.2O, 30 g/L of NiCl.sub.2/6H.sub.2O, and 30 g/L of H.sub.3BO.sub.4 under the condition of a bath temperature of 45 C. and a current density of 5 Adm.sup.2.

[0063] Cu plating was carried out by using a plating bath containing 250 g/L of CuSO.sub.4, 80 g/L of H.sub.2SO.sub.4, and 10 g/L of a brightener under the condition of a bath temperature of 30 C. and a current density of 5 Adm.sup.2.

[0064] Sn plating was carried out by using a plating bath containing 50 g/L of SnSO.sub.4, 80 g/L of H.sub.2SO.sub.4, 30 g/L of cresolsulfonic acid, and 10 g/L of a brightener under the condition of a bath temperature of 15 C. and a current density of 3 Adm.sup.2.

[0065] The reflow treatment was carried out under the condition of 450 C.12 seconds and water cooling was carried out immediately.

[0066] The surface roughness of each sample material, the exposure rate of the CuSn alloy coating layer to the material surface, and the average thickness of each coating layer were measured as follows. Further, measurement of dynamic friction coefficient, measurement of contact resistance after leaving at a high temperature, a corrosion resistance test, and a bending processability test were carried out for each sample material as follows. The results are shown in Table 1.

[Measurement of Surface Roughness of Copper Alloy Sheet with Sn Coating Layer]

[0067] The surface roughness of the copper alloy sheet with Sn coating layer was measured by the method described in the [Measurement of surface roughness of copper alloy sheet] by measuring the arithmetic mean roughness Ra in the direction parallel to the rolling direction (//) and the direction perpendicular to the rolling direction ().

[Measurement of Exposure Rate of Material of CuSn Alloy Coating Layer to Material Surface]

[0068] The surface of each sample material was observed by a SEM (scanning electric microscope) and surface composition images (200) obtained at arbitrary 3 viewing fields were binarized. Then, the average value of the exposure rate of the CuSn alloy coating layer to the material surface in the 3 viewing fields was measured by image analysis. Simultaneously, the maximum width of the Sn coating layer in the direction perpendicular to the rolling direction was measured from the binarized composition images. FIG. 1 shows the surface composition image of the sample material of No. 3 and FIG. 2 shows the composition image after the binarization of No. 3. In FIGS. 1 and 2, the vertical direction is the direction parallel to the rolling direction and the CuSn alloy coating layer (portions look black) is exposed linearly in the direction parallel to the rolling direction. Sample materials of Nos. 1, 2 and 4 to 12 also showed linear exposure of the CuSn alloy coating layer in the direction parallel to the rolling direction. Only the sample material of No. 13 did not show exposure of the CuSn alloy coating layer.

[Measurement of Average Thickness of Sn Coating Layer]

[0069] Using a fluorescent X-ray film thickness meter (SFT 3200, manufactured by Seiko Instruments Inc.), the total of the thickness of the Sn coating layer and the thickness of the Sn component contained in the CuSn alloy coating layer was measured. Thereafter, each sample material was immersed in an aqueous solution containing p-nitrophenol and sodium hydroxide for 10 minutes to remove the Sn coating layer. Again, the thickness of the Sn component contained in the CuSn alloy coating layer was measured by using the fluorescent X-ray film thickness meter. As the measurement condition, a monolayer calibration curve of Sn/base material was used as a calibration curve and the collimator diameter was set at 0.5 mm. The average thickness of the Sn coating layer was calculated by subtracting the thickness of the Sn component contained in the CuSn alloy coating layer from the total of the obtained thickness of the Sn coating layer and the thickness of the Sn component contained in the CuSn alloy coating layer.

[Measurement of Average Thickness of CuSn Alloy Coating Layer]

[0070] The average thickness of CuSn alloy coating layer was measured by using the fluorescent X-ray film thickness meter after each sample material was immersed in the above-mentioned peeling solution to remove the Sn coating layer.

[Measurement of Average Thickness of Ni Coating Layer]

[0071] Using a fluorescent X-ray film thickness meter (SFT 3200, manufactured by Seiko Instruments Inc.), the average thickness was measured. As the measurement condition, a bilayer calibration curve of Sn/Ni/base material was used as a calibration curve and the collimator diameter was set at 0.5 mm.

[Measurement of Dynamic Friction Coefficient]

[0072] The evaluation was done by simulating the shape of an indent part of an electric contact in a fitting type connection part and using the apparatus illustrated in FIG. 3. First, a male specimen 1 of a sheet material cut out of each sample material was fixed on a horizontal stand 2 and a female specimen 3 of a spherically processed material (inner diameter 1.5 mm) of the sample material of No. 13 was put thereon, and both the coating layers were brought into contact with each other. Then, a load (weight 4) of 3.0 N was applied to the female specimen 3 to hold the male specimen 1 and the male specimen 1 was pulled horizontally (sliding speed was 80 mm/min) by using a transverse type load measurement apparatus (Model 2152, manufactured by Aikoh Engineering Co., Ltd.) to measure the maximum friction force F (unit: N) to the sliding distance of 5 mm. The friction coefficient was calculated according to the following formula (1). The reference number 5 shows a load cell and the arrow shows the sliding direction.

Friction coefficient=F/3.0(1)

[0073] The friction coefficient was measured for the male specimen 1 in the moving direction parallel to the rolling direction (//) and in the moving direction perpendicular to the rolling direction ().

[Measurement of Contact Resistance after Leaving at High Temperature]

[0074] After each sample material was heated at 160 C. for 120 hours in atmospheric air, the contact resistance was measured by a 4-terminal method under the condition of an open voltage of 20 mV, an electric current of 10 mA, and no-sliding.

[Evaluation of Bending Processability]

[0075] A specimen was cut out in a manner that the rolling direction was the longitudinal direction. Using a W bending test tool defined in JIS H3110, the specimen was subjected to bending processing at a load of 9.8103 N in a manner that the bending line is in the direction perpendicular to the rolling direction. Thereafter, the cross sectional observation was performed. The bending processability was evaluated according to the following criteria: a case where no crack formed in the bent part after the test was propagated to the copper alloy base material was evaluated as and a case where cracks were propagated to the copper alloy base material and cracks were formed in the copper alloy base material was evaluated as x.

[Evaluation of Corrosion Resistance]

[0076] According to JIS 22371, each sample material was subjected to a salt water spraying test using an aqueous 5% NaCl solution at 35 C. for 6 hours. The corrosion resistance was evaluated as follows: a case where no corrosion was observed by appearance observation after the salt water spraying was evaluated as and a case where corrosion was observed was evaluated as x.

TABLE-US-00001 TABLE 1 Contact Exposure Max- resistance Base rate of imum after Material material Surface CuSn width leaving surface surface coating layer alloy of Sn Dynamic at high roughness roughness thickness (m) coating coating friction temper- Bending Ra (m) Ra (m) CuSn layer layer coefficient ature Corrosion process- No. / / / / Ni alloy Sn (%) (m) / / (m) resistance ability Embodiments 1 0.08 0.06 0.12 0.07 0.15 0.5 0.2 35 78 0.37 0.44 80 of 2 0.07 0.06 0.13 0.07 0.6 0.5 0.2 33 83 0.38 0.45 70 Invention 3 0.07 0.05 0.11 0.08 0.3 0.4 0.2 30 92 0.39 0.45 80 4 0.13 0.09 0.15 0.09 0.3 0.8 0.2 38 62 0.36 0.43 70 5 0.11 0.07 0.14 0.10 0.3 0.5 0.1 36 75 0.37 0.43 80 6 0.05 0.04 0.14 0.09 0.3 0.5 0.6 15 180 0.39 0.45 75 Comparative 7 0.07 0.04 0.11 0.08 0.05 0.5 0.2 34 81 0.38 0.43 120 Examples 8 0.06 0.04 0.14 0.11 1.0 0.5 0.2 35 79 0.38 0.44 70 x 9 0.05 0.03 0.09 0.06 0.3 0.3 0.2 25 152 0.40 0.45 250 10 0.10 0.05 0.12 0.08 0.3 1.2 0.2 39 65 0.36 0.42 50 x 11 0.16 0.09 0.21 0.12 0.3 0.5 0.05 60 49 0.34 0.41 150 x 12 0.03 0.02 0.11 0.07 0.3 0.5 0.8 5 305 0.46 0.47 70 13 0.06 0.05 0.11 0.08 0.0 0.4 0.8 0 0.54 0.56 120

[0077] Although the sample materials of Nos. 1 to 12 merely had the surface roughness (arithmetic mean roughness Ra) of the CuNiSi system copper alloy sheet as a base material in a normal level or in a slightly high level (the value of No. 11 in the direction parallel to the rolling direction), the CuSn alloy coating layer was exposed at a predetermined area rate to the material surface only by carrying out reflow treatment under the normal condition after plating with Ni, Cu, and Sn.

[0078] The sample materials of Nos. 1 to 6 having the surface roughness (arithmetic mean roughness Ra) after the reflow treatment, the average thickness of the Ni coating layer, the CuSn alloy coating layer, and the Sn coating layer, and the exposure rate of the CuSn alloy coating layer to the material surface within the defined ranges of the present invention had considerably small dynamic friction coefficients (particularly in the direction perpendicular to the rolling direction) as compared with those of the sample material of No. 12 having the Sn coating layer covering almost entire material surface and of the sample material of No. 13 having the Sn coating layer covering the entire material surface and at the same time, the sample materials of Nos. 1 to 6 were excellent in the contact resistance after leaving at a high temperature, corrosion resistance, and bending processability.

[0079] On the other hand, both of the sample material of No. 7 with a small average thickness of the Ni coating layer and the sample material of No. 9 with a small average thickness of the CuSn alloy coating layer had high contact resistance values after leaving at a high temperature. Both of the sample material of No. 8 with a large average thickness of the Ni coating layer and the sample material of No. 10 with a large average thickness of the CuSn alloy coating layer were inferior in the bending processability. The sample material of No. 11 with a small average thickness of the Sn coating layer also had too high an exposure rate of the CuSn alloy coating layer to the material surface and a small dynamic friction coefficient (particularly in the direction perpendicular to the rolling direction), and had high contact resistance after leaving at a high temperature and was inferior in corrosion resistance. The sample material of No. 12 with a relatively large average thickness of the Sn coating layer had too low an exposure rate of the CuSn alloy coating layer to the material surface, a large dynamic friction coefficient (particularly in the direction perpendicular to the rolling direction), and a large maximum width of the Sn layer in the direction perpendicular to the rolling direction. The sample material of No. 13 having the CuSn alloy coating layer which was not exposed to the material surface had a large dynamic friction coefficient (particularly in the direction perpendicular to the rolling direction) and also had an increased contact resistance after leaving at a high temperature since it had no Ni coating layer.

Embodiment 2

[0080] CuNiSi system copper alloy sheets with a thickness of 0.25 mm were produced from CuNiSi system copper alloys with various compositions as shown in Nos. 14 to 21 of Table 2 by carrying out the same steps (including grinding by a rotating buff) as those of Embodiment 1. After the surface roughness of each of the produced CuNiSi system copper alloy sheets (base material) was measured by the same method as that in Embodiment 1, Ni plating, Cu plating, and Sn plating were carried out in this order under the same conditions as those in Embodiment 1 and subsequently reflow treatment was carried out to obtain sample materials (copper alloy sheets with Sn coating layer) of Nos. 14 to 21.

[0081] The surface roughness of each sample, the exposure rate of the CuSn alloy coating layer to the material surface, and the average thickness of each coating layer were measured in the same manner as that in Embodiment 1. Measurement of dynamic friction coefficient, measurement of contact resistance after leaving at a high temperature, the corrosion resistance test, and the bending processability test were carried out for each sample material in the same manner as that in Embodiment 1. The results are shown in Table 3.

TABLE-US-00002 TABLE 2 Alloy composition (% by mass) No. Cu Ni Si Sn Mg Zn Mn Cr Co 14 Balance 2.47 0.53 15 Balance 2.58 0.55 0.05 0.49 16 Balance 1.77 0.37 0.10 1.02 0.08 17 Balance 2.51 0.56 0.15 0.16 1.12 18 Balance 1.75 0.37 19 Balance 1.03 0.23 0.06 0.014 0.09 20 Balance 3.22 0.72 1.50 0.005 0.06 21 Balance 1.20 0.56 0.12 0.01 0.55 0.04 0.04 1.20

TABLE-US-00003 TABLE 3 Contact Exposure Max- resistance Base rate of imum after Material material Surface CuSn width leaving surface surface coating layer alloy of Sn Dynamic at high roughness roughness thickness (m) coating coating friction temper- Bending Ra (m) Ra (m) CuSn layer layer coefficient ature Corrosion process- No. / / / / Ni alloy Sn (%) (m) / / (m) resistance ability Embodiments 14 0.08 0.06 0.13 0.07 0.5 0.4 0.3 38 65 0.36 0.43 60 of 15 0.07 0.06 0.11 0.05 0.3 0.5 0.3 43 80 0.35 0.42 75 Invention 16 0.07 0.06 0.12 0.06 0.4 0.4 0.2 30 78 0.37 0.45 70 17 0.10 0.08 0.14 0.09 0.3 0.4 0.2 39 63 0.35 0.42 80 18 0.11 0.08 0.16 0.08 0.4 0.5 0.3 27 55 0.38 0.44 70 19 0.09 0.06 0.13 0.08 0.3 0.5 0.2 35 60 0.36 0.43 70 20 0.06 0.05 0.11 0.06 0.2 0.5 0.3 20 100 0.39 0.45 80 21 0.10 0.08 0.16 0.08 0.3 0.5 0.3 46 75 0.34 0.43 80

[0082] As shown in Table 3, although the sample materials of Nos. 14 to 21 (copper alloy sheets with Sn coating layer) had the surface roughness (arithmetic mean roughness Ra) of the base material in a normal level, the CuSn alloy coating layer was exposed at a predetermined area rate to the material surface only by carrying out reflow treatment under the normal condition after plating with Ni, Cu, and Sn. In the case of the sample materials of Nos. 14 to 21, dynamic friction coefficients as small as those of the sample materials of Nos. 1 to 6 were obtained and the sample materials were excellent in contact resistance after leaving at a high temperature, corrosion resistance, and bending processability.