Terminal material for connectors and method for producing same

Abstract

A terminal material for connectors, which is obtained by sequentially laminating on a substrate that is formed of copper or a copper alloy, a nickel or nickel alloy layer, a copper-tin alloy layer and a tin layer in this order, and: the tin layer has an average thickness of from 0.2 m to 1.2 m (inclusive); the copper-tin alloy layer is a compound alloy layer that is mainly composed of Cu.sub.6Sn.sub.5, with some of the copper in the Cu.sub.6Sn.sub.5 being substituted by nickel, and has an average crystal grain diameter of from 0.2 m to 1.5 m (inclusive); a part of the copper-tin alloy layer is exposed from the surface of the tin layer, with the exposure area ratio being from 1% to 60% (inclusive); the nickel or nickel alloy layer has an average thickness of from 0.05 m to 1.0 m (inclusive) and an average crystal grain diameter of from 0.01 m to 0.5 m (inclusive).

Claims

1. A terminal material for connectors comprising a substrate made of copper or copper alloy and a nickel or nickel alloy layer, a copper-tin alloy layer and a tin layer layered on the substrate in this order, wherein the tin layer has an average thickness not less than 0.2 m and not more than 1.2 m, the copper-tin alloy layer is a compound alloy layer that is mainly composed of Cu.sub.6Sn.sub.5, with some of the copper in the Cu.sub.6Sn.sub.5 being substituted by nickel, the copper-tin alloy layer consists of a Cu.sub.3Sn alloy layer arranged on at least a part of the nickel or nickel alloy layer and the Cu.sub.6Sn.sub.5 alloy layer arranged on at least one of the Cu.sub.3Sn alloy layer and the nickel or nickel alloy layer, and has an average crystal grain diameter not less than 0.2 m and not more than 1.5 m, and a part thereof is exposed from a surface of the tin layer, an exposure area rate of the copper-tin alloy layer exposed from the surface of the tin layer is not less than 1% and not more than 60%, the nickel or nickel alloy layer has an average thickness not less than 0.05 m and not more than 1.0 m and an average crystal grain diameter not less than 0.01 m and not more than 0.5 m, with (a standard deviation of a crystal grain diameter)/(the average crystal grain diameter) being not more than 1.0, and has an arithmetic average roughness Ra at a surface being in contact with the copper-tin alloy layer not less than 0.005 m and not more than 0.5 m, and wherein a coefficient of kinetic friction at a surface thereof is not more than 0.3.

2. The terminal material for connectors according to claim 1, wherein a volume ratio of the Cu.sub.3Sn alloy layer to the Cu.sub.6Sn.sub.5 alloy layer is not more than 20%.

3. The terminal material for connectors according to claim 1, wherein when a slide test is performed with a sliding length 1.0 mm, a sliding speed 80 mm/min, a contact load 5 N, sliding a same material back-and-forth on surfaces of each other, the substrate is not exposed up to a sliding number of 20.

4. A method for producing the terminal material for connectors according to claim 1 by forming a nickel or nickel alloy plating layer, a copper plating layer and a tin plating layer on the substrate, and then performing a reflow treatment, wherein a thickness of the nickel or nickel alloy plating layer is not less than 0.05 m and not more than 1.0 m, a thickness of the copper plating layer is not less than 0.05 m and not more than 0.40 m, a thickness of the tin plating layer is not less than 0.5 m and not more than 1.5 m, and the reflow treatment comprises a heating step heating the plating layers to a peak temperature not lower than 240 C. and not higher than 300 C. at a heating rate not less than 20 C./second and not more than 75 C./second, a primary cooling step cooling for not less than 2 seconds and not more than 15 seconds at a cooling rate not less than 30 C./second after achieving the peak temperature, and a secondary cooling step cooling at a cooling rate not less than 100 C./second and not more than 300 C./second after the primary cooling step.

5. The terminal material for connectors according to claim 2, wherein the Cu.sub.6Sn.sub.5 alloy layer includes nickel at not less than 1 at % and not more than 25 at %.

6. A terminal material for connectors comprising a substrate made of copper or copper alloy and a nickel or nickel alloy layer, a copper-tin alloy layer and a tin layer layered on the substrate in this order, wherein the tin layer has an average thickness not less than 0.2 m and not more than 1.2 m, the copper-tin alloy layer is a compound alloy layer that is mainly composed of Cu.sub.6Sn.sub.5, with some of the copper in the Cu.sub.6Sn.sub.5 being substituted by nickel, and has an average crystal grain diameter not less than 0.2 m and not more than 1.5 m, and a part thereof is exposed from a surface of the tin layer, an exposure area rate of the copper-tin alloy layer exposed from the surface of the tin layer is not less than 1% and not more than 60%, the nickel or nickel alloy layer has an average thickness not less than 0.05 m and not more than 1.0 m and an average crystal grain diameter not less than 0.01 m and not more than 0.5 m, with (a standard deviation of a crystal grain diameter)/(the average crystal grain diameter) being not more than 1.0, and has an arithmetic average roughness Ra at a surface being in contact with the copper-tin alloy layer not less than 0.005 m and not more than 0.5 m, a ratio (an average height Rc of the copper-tin alloy layer)/(an average thickness of the copper-tin alloy layer) is not less than 0.7 and wherein a coefficient of kinetic friction at a surface thereof is not more than 0.3.

7. A method for producing the terminal material for connectors according to claim 6 by forming a nickel or nickel alloy plating layer, a copper plating layer and a tin plating layer on the substrate, and then performing a reflow treatment, wherein a thickness of the nickel or nickel alloy plating layer is not less than 0.05 m and not more than 1.0 m, a thickness of the copper plating layer is not less than 0.05 m and not more than 0.40 m, a thickness of the tin plating layer is not less than 0.5 m and not more than 1.5 m, and the reflow treatment comprises a heating step heating the plating layers to a peak temperature not lower than 240 C. and not higher than 300 C. at a heating rate not less than 20 C./second and not more than 75 C./second, a primary cooling step cooling for not less than 2 seconds and not more than 15 seconds at a cooling rate not less than 30 C./second after achieving the peak temperature, and a secondary cooling step cooling at a cooling rate not less than 100 C./second and not more than 300 C./second after the primary cooling step.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 It is a microscopic photograph of a cross section of a terminal material for connectors of Example 22.

(2) FIG. 2 It is a microscopic photograph of a cross section of a terminal material for connectors of Comparative Example 7.

(3) FIG. 3 It is a microscopic photograph of a surface of a test piece of a female terminal of Example 22 after a slide test.

(4) FIG. 4 It is a microscopic photograph of a surface of a test piece of a female terminal of Comparative Example 10 after a slide test.

(5) FIG. 5 It is a frontal view schematically showing equipment for measuring a coefficient of kinetic friction.

DESCRIPTION OF EMBODIMENTS

(6) A terminal material for connectors of an embodiment of the present invention will be explained.

(7) In a terminal material for connectors of the present invention, a nickel or nickel alloy layer, a copper-tin alloy layer, and a tin layer are layered in this order on a substrate made of copper or copper alloy.

(8) The substrate is enough to be made of copper or copper alloy, and composition thereof is not specifically limited.

(9) The nickel or nickel alloy layer is a layer made of pure nickel, nickel alloy such as nickel cobalt (NiCo), nickel tungsten (NiW), or the like.

(10) The nickel or nickel alloy layer has an average thickness of not less than 0.05 m and not more than 1.0 m, an average crystal grain diameter of not less than 0.01 m and not more than 0.5 m, a ratio of (a standard deviation crystal grain diameters)/(an average crystal grain diameter) of 1.0 or less, and arithmetic average roughness Ra of a surface being in contact with the copper-tin alloy layer of not less than 0.005 m and not more than 0.5 m.

(11) The copper-tin alloy layer is a compound alloy layer that is mainly composed of Cu.sub.6Sn.sub.5, with some of the copper in the Cu.sub.6Sn.sub.5 being substituted by nickel, and has an average crystal grain diameter of not less than 0.2 m and not more than 1.5 m; a part of the copper-tin alloy layer is exposed from a surface of the tin layer.

(12) The copper-tin alloy layer consists of a Cu.sub.3Sn alloy layer arranged on at least a part of the nickel or nickel alloy layer, and a Cu.sub.6Sn.sub.5 alloy layer arranged on at least one of the Cu.sub.3Sn alloy layer and the nickel or nickel alloy layer. In other words, between the Cu.sub.6Sn.sub.5 alloy layer and the nickel or nickel alloy layer, Cu.sub.3Sn alloy layers partially exists. Therefore, the Cu.sub.6Sn.sub.5 alloy layer is formed over the Cu.sub.3Sn alloy layer on the nickel or nickel alloy layer and the nickel or nickel alloy layer where the Cu.sub.3Sn alloy layers does not exist. In this case, a volume ratio of the Cu.sub.3Sn alloy layer with respect to the Cu.sub.6Sn.sub.5 alloy layer is 20% or less. This Cu.sub.6Sn.sub.5 alloy layer includes nickel at not less than 1 at % and not more than 25 at %.

(13) The copper-tin alloy layer is formed by forming a nickel or nickel alloy plating layer, a copper plating layer and a tin plating layer on the substrate in this order and subsequently performing a reflow treatment, as described below.

(14) An interface between the copper-tin alloy layer is formed to be steep and uneven, and a part of the copper-tin alloy layer is exposed from the surface of the tin layer: removing the tin layer so that the copper-tin alloy layer appears at a surface by melting for measurement, a ratio (an average height Rc of the copper-tin alloy layer)/(an average thickness of the copper-tin alloy layer) is 0.7 or more.

(15) The tin layer has an average thickness of not less than 0.2 m and not more than 1.2 m: a part of the copper-tin alloy layer is exposed from the surface of the tin layer. An exposure area ratio thereof is not less than 1% and not more than 60%.

(16) In the terminal material having such a structure, the interface between the copper-tin alloy layer and the tin layer is steep and uneven; there is a composite construction of the hard copper-tin alloy layer and the tin layer in a depth range of a few hundred nm from the surface of the tin layer; a part of the hard copper-tin alloy layer thereof is exposed a little from the tin layer; soft tin around them functions as lubricant: a low coefficient of kinetic friction as 0.3 or less is realized. The exposure area rate of the copper-tin alloy layer is the limited range of 1% to 60% (inclusive); an excellent electrical connection characteristic of the tin layer is not deteriorated.

(17) Next, a method for manufacturing the terminal material for connectors will be explained.

(18) A board material made of pure copper or copper alloy such as CuMgP type or the like is prepared as the substrate. Cleaning a surface of the board material by degreasing, pickling and the like, then a nickel plating treatment, a copper plating treatment and a tin plating treatment are performed in this order.

(19) For the nickel plating treatment, a general nickel plating bath can be used: for example, a sulphate bath that is mainly composed of sulfuric acid (H.sub.2SO.sub.4) and nickel sulfate (NiSO.sub.4) or the like can be used. Temperature of the plating bath is 20 C. to 60 C. (inclusive): current density is 5 to 60 A/dm.sup.2. The reason is that, if it is less than 5 A/dm.sup.2, the average crystal grain diameter of the nickel or nickel alloy layer is not minute, the arithmetic average roughness Ra of the surface being in contact with the copper-tin alloy layer is large, and a nickel content in (Cu, Ni).sub.6Sn.sub.5 alloy is small; so that the copper-tin alloy layer having the steep and uneven shape is not formed. A film thickness of this nickel-plating layer is 0.05 m to 1.0 m (inclusive). The reason is that, if it is less than 0.05 m, the nickel content in the (Cu, Ni).sub.6Sn.sub.5 alloy is small, and the copper-tin alloy layer having the steep and uneven shape is not formed: or if it is more than 1.0 m, it is difficult to perform a bending work and the like.

(20) For the copper plating treatment, a general copper plating bath can be used; for example, a copper sulfate bath that is mainly composed of copper sulfate (CuSO.sub.4) and sulfuric acid (H.sub.2SO.sub.4) or the like can be used. Temperature of the plating bath is 20 to 50 C.: current density is 1 to 30 A/dm.sup.2. A film thickness of a copper plating layer formed by this copper plating treatment is 0.05 m to 0.40 m (inclusive). The reason is that, if it is less than 0.05 m, the nickel content in the (Cu, Ni).sub.6Sn.sub.5 alloy is large, and a shape of copper-tin alloy is too minute: or if it is more than 0.4 m, the nickel content in (Cu, Ni).sub.6Sn.sub.5 alloy is small, and the copper-tin alloy layer having the steep and uneven shape is not formed.

(21) A general tin plating bath can be used as a plating bath for forming the tin-plating layer: for example, a sulphate bath that is mainly composed of sulfuric acid (H.sub.2SO.sub.4) and stannous sulphate (SnSO.sub.4) can be used. Temperature of the plating bath is 15 to 35 C.: current density is 1 to 30 A/dm.sup.2. A film thickness of the tin-plating layer is 0.5 m to 1.5 m (inclusive). If it is less than 0.5 m, the tin layer after reflowing is thin and the electrical connection characteristics is deteriorate: or if it is more than 1.5 m, an exposure of the copper-tin alloy layer from the surface is small; so that it is difficult to reduce the coefficient of kinetic friction to 0.3 or less.

(22) After the plating treatments, a reflow treatment is performed by heating.

(23) The reflow treatment includes a heating step heating an object after plating to a peak temperature 240 to 300 C. for 3 to 15 seconds with a heating rate 20 to 75 C./second in a heating furnace with a CO reducing atmosphere; a primary cooling step after reaching the peak temperature, cooling it with a cooling rate 30 C./second or less for 2 to 15 seconds; and a secondary cooling step after primarily cooling, cooling it with a cooling rate 100 to 300 C./second for 0.5 to 5 seconds. The primary cooling step is performed by air-cooling: the secondary cooling step is performed by water-cooling using water with temperature 10 to 90 C.

(24) By performing the reflow treatment in the reducing atmosphere, a tin-oxide film having high melting temperature is prevented from being generated on the tin plated surface; and it is possible to perform the reflow treatment at lower temperature and for shorter time, and easy to generate desired structure of intermetallic compound. Since two cooling steps are performed, copper atoms are mildly diffused in tin particles and the intended structure of the intermetallic compound is generated by performing the primary cooling step with the small cooling rate. By rapidly cooling after that, growth of an intermetallic compound layer is stopped and can be fixed at the intended structure. Copper and tin deposited by electrodeposition with high electric density are not stable, so that metal-alloying is occurred and crystal grains are bloated even in room temperature; it is difficult to make the intended structure of the intermetallic compound by the reflow treatment. Therefore, it is desirable to perform the reflow treatment immediately after the plating treatment. Specifically, it is necessary to perform the reflow treatment within 15 minutes, or desirably within 5 minutes after the tin-plating treatment. It is not a problem that a leaving time is short after the plating treatment; in a general treatment line, it is about 1 minute after because of the structure.

EXAMPLES

(25) On a substrate with a plate thickness 0.25 mm made of copper alloy (Mg 0.5 mass % to 0.9 mass % (inclusive)-P 0.04 mass % or lower), a nickel-plating treatment, a copper-plating treatment, and a tin-plating treatment were performed in order. In this case, conditions of the nickel-plating treatment, the copper-plating treatment and the tin-plating treatment were the same in Examples and Comparative Examples, as shown in Table 1. In Table 1, Dk is an abbreviation of current density of a cathode, and ASD is an abbreviation of A/dm.sup.2.

(26) TABLE-US-00001 TABLE 1 NICKEL PLATING COPPER PLATING TIN PLATING PLATING NICKEL SULFATE 300 g/L COPPER SULFATE 250 g/L TIN SULFATE 75 g/L BATH SULFURIC ACID 2 g/L SULFURIC ACID 50 g/L SULFURIC ACID 85 g/L COMPOSITION ADDITIVE 10 g/L BATH TEMPERATURE 45 C. 25 C. 25 C. Dk 20 ASD 5 ASD 2 ASD

(27) Performing the plating treatments, then the reflow treatment was performed by heating. This reflow treatment was performed 1 minute after the last tin-plating treatment; a heating step, the primary cooling step and the secondary cooling step were performed. Thicknesses and reflowing conditions of the respective plating layers were shown in Table 2.

(28) TABLE-US-00002 TABLE 2 REFLOWING CONDITION PRIMARY PRIMARY SECONDARY PLATING LAYER HEATING PEAK COOLING COOLING COOLING THICKNESS (m) RATE TEMPERATURE RATE TIME RATE Ni Cu Sn ( C./s) ( C.) ( C./s) (second) ( C./s) EXAMPLES 1 0.2 0.1 0.5 40 240 20 5 250 2 0.1 0.15 0.7 40 270 20 5 170 3 0.3 0.25 1 40 270 20 5 170 4 0.2 0.2 1.2 50 300 20 5 170 5 0.3 0.35 1.5 50 300 10 5 250 6 0.4 0.05 0.6 40 300 30 3 170 7 0.3 0.4 1.3 40 270 20 5 170 8 0.07 0.15 0.7 60 240 30 3 150 9 1 0.25 0.8 40 270 20 5 170 10 0.1 0.25 1.5 40 240 30 5 300 11 0.3 0.05 0.6 40 240 20 5 300 12 0.2 0.35 0.7 30 270 10 5 170 13 0.3 0.1 1.2 40 270 20 5 170 14 0.3 0.3 0.6 40 270 10 5 170 15 0.4 0.35 1.3 40 270 20 5 170 16 0.3 0.2 0.7 40 270 20 5 170 17 0.2 0.15 0.6 25 300 10 10 170 18 0.4 0.2 0.8 40 270 20 5 170 19 0.2 0.25 0.9 40 270 20 5 170 20 0.5 0.4 1 40 240 20 5 250 21 0.3 0.35 0.7 30 240 15 5 170 22 0.3 0.2 0.8 40 270 20 5 170 23 0.06 0.25 0.8 30 240 20 6 150 24 1 0.25 0.8 50 300 30 4 170 25 0.5 0.3 1.4 50 300 30 4 170 26 0.3 0.05 0.5 40 240 20 5 300 27 0.2 0.35 0.7 30 270 10 8 200 28 0.3 0.3 0.7 40 270 20 5 170 29 0.3 0.15 0.6 60 300 30 3 200 30 0.4 0.15 0.9 40 270 20 5 170 31 0.3 0.3 0.7 40 270 20 5 170 32 0.1 0.3 0.7 25 300 10 10 170 33 0.4 0.35 1 30 300 30 8 150 34 0.3 0.25 0.9 40 240 20 4 150 COMPARATIVE 1 0.3 0.2 0.4 40 270 20 5 170 EXAMPLES 2 0.3 0.2 1.7 40 270 20 5 170 3 0.5 0.03 0.5 40 270 20 5 170 4 0.3 0.5 1.2 40 270 20 5 170 5 0.02 0.2 0.9 40 270 20 5 170 6 0.3 0.05 0.6 80 320 30 3 250 7 0.3 0.4 0.9 30 330 20 8 170 8 0.15 0.25 0.9 18 250 10 10 150 9 0.3 0.15 0.6 20 320 20 5 170 10 0.3 0.1 0.7 25 330 10 11 200

(29) Regarding these respective test pieces, measured were: the thickness of the tin layers, the thickness of the nickel or nickel alloy layers, the surface roughness Ra of the nickel or nickel alloy layers, the crystal grain diameter of the nickel or nickel alloy layers, the crystal grain diameter of the copper-tin alloy layers, the nickel content in the (Cu, Ni).sub.6Sn.sub.5 alloy layers, the volume ratio of the Cu.sub.3Sn alloy layers with respect to the Cu.sub.6Sn.sub.5 alloy layers, the exposure area rate of the copper-tin alloy layer in the surface on the tin layers, the ratio (the average height Rc of the copper-tin alloy layer)/(the average thickness of the copper-tin alloy layer): and evaluated were the coefficient of kinetic friction, the abrasion resistance, glossiness, and electrical reliability.

(30) Measuring Method of the Thicknesses of the Layers

(31) The thickness of the nickel or nickel alloy layers, the thicknesses of the tin layers and the copper-tin alloy layers were measured with a fluorescent X-ray film thickness meter made by SII Nano Technology Inc. (SEA5120A). For measurement of the thickness of the tin layers and the thickness of the copper-tin alloy layers, at first, a whole thickness of a layer including tin of samples after the reflowing treatment was measured, then removing the tin layer by soaking in etching solution for peeling plating films which does not corrode the copper-tin alloy layer for 5 minutes so as to exposure the copper-tin alloy layer thereunder, a thickness of the copper-tin alloy layer was measured: the thickness of the tin layer was defined as (the whole thickness of layers including tin) minus (the thickness of the copper-tin alloy layer). For measurement of the thickness of the nickel or nickel alloy layer, removing the tin layer and the copper-tin alloy layer by soaking in etching solution for peeling plating films which does not corrode the nickel or nickel alloy layer for about 1 hour, to exposure the nickel or nickel alloy layer thereunder, and the thickness of the nickel or nickel alloy layer was measured.

(32) Measuring Method of the Nickel Contents and Presence of the Cu.sub.3Sn Alloy Layers in the (Cu, Ni).sub.6Sn.sub.5 Alloy Layer

(33) The nickel contents and the presence of the Cu.sub.3Sn alloy layers in the (Cu, Ni).sub.6Sn.sub.5 alloy layer were obtained as follows: specifying positions of alloy by area analysis by observation of sectional STEM images and EDS analysis so as to obtain the nickel contents in the (Cu, Ni).sub.6Sn.sub.5 alloy layers by point analysis; and the presence of the Cu.sub.3Sn alloy layers by linear analysis in a depth direction. Regarding the presence of the Cu.sub.3Sn alloy layers in broader area were judged by removing the tin layer by soaking in etching solution for peeling the tin plating films exposure the copper-tin alloy layer thereunder, and then measuring an X-ray diffraction pattern by CuK ray, in addition to by the cross-sectional observation. Measuring conditions are as follows.

(34) MPD1880HR made by PANalytical Ltd.

(35) Vacuum Tube: CuK ray

(36) Voltage: 45 kV

(37) Current: 40 mA

(38) Measuring Method of Average Crystal Grain Diameters of Copper-Tin Alloy Layers

(39) The average crystal grain diameter of the copper-tin alloy layer was measured from results of the cross-sectional EBSD analysis after the reflow treatment. Sampling the materials after the reflow treatment and observing cross sections thereof orthogonal to a rolling direction, average values and standard deviations of the crystal grains were measured. After mechanical polishing using waterproof abrasive papers and diamond abrasive grains, final polishing was performed with colloidal silica solution. Using EBSD measuring equipment (S4300-SE made by Hitachi High-Technologies Corporation and OIM Data Collection made by EDAX/TSL (the present AMETEK) and analysis software (OIM Data Analysis ver. 5.2 made by EDAX/TSL (the present AMETEK), misorientation of the respective crystal grains was analyzed with electron rays at acceleration voltage 15 kV, measuring intervals 0.1 mm step and a measuring area 3.0 mm250 mm or more. CI values were calculated by the analysis software OIM: the crystal grain diameters having the CI value (Confidence Index) 0.1 or less were excluded from the analysis of the crystal grain diameters. From results of two-dimensional cross-section observation, a crystal grain boundary map was made regarding crystal grain boundaries between adjacent measuring points in which the misorientation of two crystal grains is 15 or more, excluding twin crystals. A measuring method of the crystal grain diameter: a mean value of a major axis (a length of a longest straight line which can be drawn inside the grain without being in contact with a grain boundary) and a minor axis (a length of a longest straight line in an orthogonal direction to the major axis, which can be drawn inside the grain without being in contact with a grain boundary) in a crystal grain was decided as the crystal grain diameter.

(40) Measuring Method of Average Crystal Grain Diameter in Nickel or Nickel Alloy Layer

(41) Regarding the average crystal grain diameter in the nickel or nickel alloy layer, a cross section was observed with a scanning ion microscope. A measuring method of the crystal grain diameter: a mean value of a major axis (a length of a longest straight line which can be drawn inside the grain without being in contact with a grain boundary) and a minor axis (a length of a longest straight line in an orthogonal direction to the major axis, which can be drawn inside the grain without being in contact with a grain boundary) in a crystal grain was decided as the crystal grain diameter.

(42) Measuring Method of Arithmetic Average Roughness Ra of Nickel or Nickel Alloy Layer

(43) The arithmetic average roughness Ra of a surface of the nickel or nickel alloy layer in contact with the copper-tin alloy layer was obtained as a mean value measured as follows: soaking in etching solution for peeling tin-plating films to remove the tin layer and the copper-tin alloy layer and exposing the nickel or nickel alloy layer thereunder, then measuring Ra at 7 points in a longitudinal direction and 7 points in a short direction (14 points in total) at a magnification of 100 with an objective lens (a measuring view field 128 m128 m), using a laser microscope (OLS3000) made by Olympus Corporation.

(44) Measuring Method of Exposure Area Rate of Copper-Tin Alloy Layer

(45) The exposure area rate of the copper-tin alloy layer was observed after removing a surface oxide film, with the scanning ion microscope at a field 100100 m. Using image processing software, a proportion of white areas to whole area of a measuring field was decided as the exposure area rate of the copper-tin alloy layer; because the Cu.sub.6Sn.sub.5 alloy is imaged white if it presences in a depth area from an outermost surface to about 20 nm according to a measurement principle.

(46) Measuring Method of Volume Ratio of Cu.sub.6Sn.sub.5 Alloy Layer to Cu.sub.3Sn Alloy Layer

(47) The volume ratio of the Cu.sub.6Sn.sub.5 alloy layer to the Cu.sub.3Sn alloy layer in the copper-tin alloy layer was by obtained by observing a cross section with the scanning ion microscope.

(48) Measuring Method of (Average Height Rc of Copper-Tin Alloy Layer)/(Average Thickness of Copper-Tin Alloy Layer

(49) The average height Rc of the copper-tin alloy layer was obtained as a mean value of Rc measured as follows: soaking in etching solution for peeling tin-plating films to remove the tin layer and exposing the copper-tin alloy layer thereunder, then measuring Rc at 7 points in a longitudinal direction and 7 points in a short direction (14 points in total) at a magnification of 100 with an objective lens (a measuring view field 128 m128 m), using the laser microscope (OLS3000) made by Olympus Corporation. The rate (the average height Rc of the copper-tin alloy layer)/(the average thickness of the copper-tin alloy layer) was calculated by dividing the average height Rc obtained by the above method by the average thickness of the copper-tin alloy layer.

(50) Measuring results are shown in Table 3.

(51) Reference symbols A to H, J, and K in Table 3 denote as follows.

(52) A: the average thickness of the tin layer

(53) B: the average thickness of the nickel or nickel alloy layer

(54) C: the arithmetic average roughness Ra of the nickel or nickel alloy layer

(55) D: the average crystal grain diameter of the nickel or nickel alloy layer

(56) E: (the standard deviation of the crystal grain diameter)/(the average crystal grain diameter) in the nickel or nickel alloy layer

(57) F: the average crystal grain diameter of the copper-tin alloy layer

(58) G: (the average height Rc of the copper-tin alloy layer)/(the average thickness of the copper-tin alloy layer)

(59) H: the nickel content in the (Cu, Ni).sub.6Sn.sub.5

(60) J: the volume ratio of the Cu.sub.3Sn to the (Cu, Ni).sub.6Sn.sub.5

(61) K: the surface exposure rate of the copper-tin alloy layer

(62) TABLE-US-00003 TABLE 3 A B C D F H J K (m) (m) (m) (m) E (m) G (at %) (%) (%) EXAMPLES 1 0.21 0.18 0.04 0.04 0.68 0.72 0.92 13 1 51 2 0.34 0.09 0.07 0.09 0.74 0.74 1.23 9 4 34 3 0.65 0.29 0.21 0.22 0.83 0.91 1.46 3 12 21 4 0.92 0.19 0.16 0.14 0.7 0.81 1.51 8 9 25 5 1.07 0.29 0.1 0.18 0.76 1.34 1.52 3 14 4 6 0.3 0.36 0.21 0.2 0.8 0.42 0.81 23 1 14 7 0.79 0.3 0.01 0.16 0.65 1.18 1.35 3 18 16 8 0.36 0.05 0.07 0.11 0.6 0.7 1.21 2 6 28 9 0.43 0.97 0.34 0.21 0.86 0.82 1.44 18 8 35 10 1.16 0.08 0.07 0.25 0.66 0.64 1.1 9 8 3 11 0.39 0.26 0.24 0.19 0.77 0.31 0.73 22 0 7 12 0.28 0.19 0.04 0.04 0.64 1.47 1.55 5 14 41 13 0.87 0.28 0.05 0.12 0.63 0.74 1.35 11 3 2 14 0.26 0.29 0.08 0.06 0.67 1.03 1.42 5 10 59 15 0.91 0.39 0.02 0.02 0.68 1.21 1.48 14 4 11 16 0.41 0.29 0.39 0.49 0.9 0.68 1.07 4 12 21 17 0.28 0.19 0.41 0.3 0.96 0.65 0.98 9 9 16 18 0.47 0.39 0.008 0.16 0.63 0.79 1.36 3 5 38 19 0.56 0.19 0.48 0.31 0.87 0.92 1.47 10 7 24 20 0.64 0.49 0.22 0.18 0.72 1.16 0.94 4 21 8 21 0.3 0.29 0.09 0.08 0.65 1.12 0.68 4 15 12 22 0.44 0.28 0.11 0.19 0.76 0.79 1.36 11 3 39 23 0.28 0.05 0.12 0.34 0.81 1.39 0.64 1 19 8 24 0.41 0.95 0.08 0.12 0.75 0.95 1.62 27 4 40 25 1.15 0.46 0.15 0.14 0.72 1.12 1.5 26 6 7 26 0.29 0.23 0.19 0.18 0.83 0.29 0.56 21 1 8 27 0.26 0.19 0.38 0.41 0.9 1.44 0.83 3 22 5 28 0.35 0.29 0.21 0.22 0.85 1.07 0.74 0.5 17 3 29 0.28 0.277 0.05 0.04 0.64 0.83 1.57 27 2 57 30 0.53 0.36 0.01 0.02 0.65 0.72 1.46 26 3 16 31 0.36 0.29 0.42 0.47 0.86 1.1 0.65 2 21 8 32 0.09 0.31 0.37 0.33 0.94 1.24 0.71 2 21 8 33 0.59 0.4 0.43 0.42 0.87 1.31 0.74 0 31 5 34 0.57 0.29 0.47 0.33 0.89 0.99 0.83 3 21 9 COMPARATIVE 1 0.14 0.29 0.07 0.21 0.76 0.67 1.21 6 8 72 EXAMPLES 2 1.41 0.29 0.04 0.13 0.64 0.79 1.34 9 6 0 3 0.33 0.46 0.1 0.15 0.72 0.16 0.84 19 0 6 4 0.81 0.3 0.08 0.22 0.73 1.64 0.62 1 26 7 5 0.52 0.01 0.13 0.27 0.81 1.34 0.65 0 10 2 6 0.4 0.28 0.02 0.04 0.68 0.18 0.77 19 2 1 7 0.41 0.3 0.21 0.18 0.75 1.84 0.59 0.5 18 3 8 0.58 0.15 0.68 0.34 0.86 1.22 1.2 5 8 13 9 0.28 0.29 0.52 0.56 0.98 1.08 1.15 2 5 22 10 0.47 0.29 0.32 0.36 1.08 1.12 1.15 6 10 24

(63) The coefficient of kinetic friction, the glossiness, and the electrical reliability were evaluated as follows.

(64) Measuring Method of Coefficient of Kinetic Friction

(65) The coefficient of kinetic friction was obtained as follows: for each of Examples or Comparative Examples, simulating a connector part of a female terminal and a male terminal of a fitting type connector, formed were a female test piece with a half-ball shape with an inner diameter 1.5 mm and a male test piece with a plate shape made of the same material, and a kinetic friction force was measured between the test pieces using a friction measuring device (a horizontal force tester, type M-2152ENR) made by Aikoh Engineering Co., Ltd. Explaining by FIG. 5, the male test piece 12 is fixed on a horizontal table 11 and the half-ball convex surface of the female test piece 13 is arranged on the male test piece 12 so that both plating surfaces are in contact with each other, and a load P 100 gf to 500 gf (inclusive) is applied on the female test piece 13 by a weight 14 to press the male test piece 12. In this state in which the load P was applied on, the male test piece 12 was drawn for 10 mm in a horizontal direction shown by an arrow with a sliding speed 80 mm/min, and a friction force F was measured by a load cell 15. From an average value Fav of the friction forces F and the load P, the coefficient of kinetic friction (=Fav/P) was obtained.

(66) Evaluation Method of Abrasion Resistance

(67) The abrasion resistance was obtained as follows: simulating a connection part of a female terminal and a male terminal of a fitting type connector, for each of Examples and Comparative Examples, formed were a female test piece with half-ball shape with an inner diameter 1.5 mm and a male test piece with a plate shape made of the same material, a repeated slide test was performed using a friction measuring device (the horizontal force tester, type M-2152ENR) made by Aikoh Engineering Co., Ltd. Explaining by FIG. 5, the male test piece 12 is fixed on the horizontal table 11 and the half-ball convex surface of the female test piece 13 is arranged on the male test piece 12 so that both the plating surfaces are in contact with each other, and the load P 100 gf to 500 gf (inclusive) is applied on the female test piece 13 by the weight 14 to press the male test piece 12. In this state in which the load P was applied on, the male test piece 12 was drawn back-and-forth for a distance 1 mm in the horizontal direction shown by the arrow with a sliding speed 80 mm/min. Sliding it repeatedly with counting a sliding number as one when it moved back-and-forth once, it was obtained from the sliding number when the substrate was exposed. If the substrate was not exposed even after the sliding number was 20 times or more, it was evaluated as o: or if the substrate was exposed before the sliding number was 20 times, it was evaluated as x.

(68) Measuring Method of Glossiness

(69) The glossiness was measured using a gloss meter (model No.: VG-2PD) made by Nippon Denshoku Industries Co., LTD, in accordance with JIS Z 8741, at an incident angle 60 degree.

(70) Measuring Method of Contact Resistance Value

(71) The contact resistance was measured by heating in the air at 150 C. for 500 hours to evaluate the electric reliability. The measuring method was in accordance with JIS-C-5402 with a four-connectors contact resistance tester (CRS-113-AU made by Yamasaki Seiki Institution), measuring a load variation from 0 to 50 g and a contact resistance in a sliding type (1 mm), the contact resistance value was evaluated at the load 50 g.

(72) Measuring results and evaluating results are shown in Table 4.

(73) TABLE-US-00004 TABLE 4 COEFFICIENT CONTACT OF KINETIC ABRASION GLOSSINESS RESISTANCE FRICTION RESISTANCE (10.sup.2 GU) (m) EXAMPLES 1 0.23 5.5 7.55 2 0.24 6.3 3.8 3 0.28 6.9 3.79 4 0.28 7.3 1.79 5 0.29 8 1.18 6 0.28 7.4 5.69 7 0.27 6.9 2.75 8 0.25 6.6 4.69 9 0.24 6.2 5.57 10 0.29 8.3 1.85 11 0.28 7.6 4.37 12 0.23 6.1 5.84 13 0.29 8.3 1.96 14 0.24 5.2 8.54 15 0.28 7.7 2.53 16 0.25 7.1 3.2 17 0.26 7.5 3.18 18 0.24 6.4 5.67 19 0.26 7.1 3.54 20 0.28 8.1 2.1 21 0.27 7.8 1.69 22 0.24 6.8 4.33 23 0.29 7.4 3.22 24 0.24 5.6 5.8 25 0.3 7.9 1.98 26 0.28 7.6 4.64 27 0.29 8.1 2.55 28 0.3 8.2 1.79 29 0.23 4.5 8.41 30 0.26 6.9 3.1 31 0.27 6.2 2.42 32 0.28 7.8 1.67 33 0.29 7.8 2.83 34 0.28 7.4 2.96 COMPARATIVE 1 0.23 4.6 14.38 EXAMPLES 2 0.46 8.1 1.13 3 0.33 7.5 12.77 4 0.31 7.2 5.76 5 0.38 7.3 1.51 6 0.41 8 12.49 7 0.4 6.9 2.06 8 0.3 6.5 3.49 9 0.26 5.9 2.45 10 0.28 6.3 4.48

(74) As clearly known from Table 3 and Table 4, the coefficients of kinetic friction were small as 0.3 or less in respective Examples, and the abrasion resistance and the contact resistance values were good.

(75) In Comparative Examples, the following defects were found.

(76) In Comparative Example 1, since the copper-tin alloy layer was too much exposed from the surface, the tin layer staying on the surface was too less, so that the contact resistance is deteriorated. In Comparative Example 2, since the copper-tin alloy layer was too less appeared on the surface, an effect of reducing the coefficient of kinetic friction cannot be obtained. In Comparative Examples 3 and 6, since the crystal grain diameters of the copper-tin alloy layer was too small, the copper-tin alloy layer appeared on the surface was small, so that the effect of reducing the coefficient of kinetic friction cannot be obtained and the contact resistance is deteriorated. In Comparative Examples 4, 5 and 7, the copper-tin alloy layer was not formed to be a steep and uneven shape, the effect of reducing the coefficient of kinetic friction is not obtained. In Comparative Examples 8, 9, and 10, since the arithmetic average roughness Ra at the surface being in contact with the copper-tin alloy layer of the nickel layer is too high, the substrate is exposed in the slide test, the abrasion durability is deteriorated.

(77) FIG. 1 is a microscopic photograph of a cross section of a copper alloy terminal material of Example 22: FIG. 2 is a microscopic photograph of a cross section of a copper alloy terminal of Comparative Example 7. As recognized by contrasting these photographs, in Examples the Cu.sub.6Sn.sub.5 alloy layers have the steep and uneven shape: in Comparative Examples the Cu.sub.6Sn.sub.5 alloy layer do not formed to be the rough uneven shape.

(78) FIG. 3 is a microscopic photograph of a sliding surface of the female terminal test piece after the slide test in Example 22: FIG. 4 is a microscopic photograph of a sliding surface of the female terminal test piece after the slide test in Comparative Example 10. As recognized by contrasting these photographs, in Example exposure of the substrate is not appeared: in Comparative Example some parts of the substrate are exposed.

INDUSTRIAL APPLICABILITY

(79) The present invention can be utilized as a terminal for connectors used for connecting electric wiring in vehicles, consumer products and the like, especially for terminals for multi-pin connectors.

REFERENCE SIGNS LIST

(80) 11 table 12 male test piece 13 female test piece 14 weight 15 load cell