Connector terminal material

Abstract

To provide a connector terminal material in which the heat-resistant property and processing followability of a connector terminal material having a copper-tin alloy layer and a tin layer is further improved.SOLUTION: Provided is a connector terminal material 1 in which a copper-tin alloy layer 3 and a tin layer 4 made of tin or a tin alloy are laminated in this order on a substrate 2 made of copper or a copper alloy, and in which, when the crystal orientation distribution function of the tin layer obtained from the aggregate texture analysis by EBSD is expressed by Euler angles (φ1, Φ, φ2) using the surface of the tin layer as an observation surface, the average value of orientation density in ranges of φ2=60°, φ1=60° to 75°, and Φ=0° to 15° is 0.05 or more and less than 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a terminal material for connectors provided with a coating useful for connecting electrical wiring in automobiles, consumer devices, etc. [Background technology]

[0002] Connectors used for connecting electrical wiring in automobiles and the like are known. These automotive connectors (in-vehicle terminals) include a terminal pair designed to be electrically connected when a contact portion provided on a female terminal comes into contact with a male terminal inserted into the female terminal with a predetermined contact pressure. Terminal materials widely used for such connectors (terminals) include a copper-tin (Cu-Sn) alloy layer formed below a surface tin layer by plating copper (Cu) and tin (Sn) on a substrate made of copper or a copper alloy and then performing a reflow process.

[0003] In recent years, for example, the rapid advancement of electrification and electronics in automobiles has led to a remarkable miniaturization of connectors used in response to the increasing currents and higher integration of electrical equipment. As connectors become smaller, more severe bending processes are required to form the terminals, and the heat generated in the connector during use cannot be sufficiently dissipated, which tends to increase the connector's temperature rise. Furthermore, as currents and voltages increase, more current is required to flow, which tends to increase the temperature rise due to heat generation. For this reason, automotive connectors are required to have excellent heat resistance and processability.

[0004] For example, Patent Document 1 discloses a terminal material in which a Ni layer, an intermediate layer made of a Cu-Sn alloy (Cu-Sn intermetallic compound layer), and a surface layer made of Sn or a Sn alloy are formed in this order on the surface of a Cu or Cu alloy substrate. In this case, the Ni layer is epitaxially grown on the substrate. The Ni layer has an average crystal grain size of 1 μm or more, a thickness of 0.1 to 1.0 μm, a thickness of the intermediate layer of 0.2 to 1.0 μm, and a thickness of the surface layer of 0.5 to 2.0 μm. This enhances the barrier properties against the underlying Cu or Cu alloy substrate, more reliably prevents Cu diffusion, and improves heat resistance. This results in a Sn-plated material that can maintain stable contact resistance even in high-temperature environments. However, because the Ni layer is required, if the Ni layer cannot be incorporated due to cost, heat resistance cannot be improved. Furthermore, because the Ni layer requires pretreatment of the substrate for epitaxial growth, the substrate for which heat resistance can be improved is limited.

[0005] On the other hand, Patent Document 2 discloses a connector terminal having a metal base material made of a Cu-Fe alloy, a base plating layer formed by heat-treating a Ni-based plating layer formed on the surface of the metal base material, and a top plating layer formed on the surface of the base plating layer. Because the base plating layer is formed by heat-treating the Ni-based plating layer formed on the surface of the metal base material, the terminal has superior elongation and is less likely to crack during bending compared to a base plating layer made of an unheat-treated Ni-based plating layer in its electrodeposited state. In this case, the heat treatment temperature is exemplified as 750 to 850°C, and the heat treatment time is exemplified as 0.5 to 3 hours. However, because the heat treatment temperature exceeds 700°C, it cannot be applied when strength is required for the copper alloy used as the base material. Furthermore, tin plating cannot improve processing followability because it is not possible to introduce a Ni layer or Ni alloy layer due to cost reasons. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-122403 [Patent Document 2] Japanese Patent Application Publication No. 2017-27705 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and has an object to further improve the heat resistance and processing followability of a terminal material for a connector having a copper-tin alloy layer and a tin layer. [Means for solving the problem]

[0008] The connector terminal material of the present invention is a connector terminal material comprising a copper-tin alloy layer and a tin layer made of tin or a tin alloy laminated in this order on a substrate made of copper or a copper alloy, and when the crystal orientation distribution function of the tin layer obtained by texture analysis using EBSD with the surface of the tin layer as the observation surface is expressed in terms of Euler angles (φ1, Φ, φ2), the average value of the orientation density in the ranges of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° is 0.05 or more and less than 50.

[0009] This connector terminal material has a tin layer on its surface, which provides the excellent electrical properties inherent to a tin layer. Furthermore, when the crystal orientation distribution function (ODF) obtained from EBSD texture analysis of the tin layer surface is expressed in terms of Euler angles (φ1, Φ, φ2), the average orientation density in the ranges of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° is 0.05 or more and less than 50. This suppresses the diffusion of copper elements into the tin layer surface, improving heat resistance and preventing cracking of the tin layer during bending, thereby demonstrating excellent bending conformability. If the average orientation density is less than 0.05, the diffusion of copper elements into the tin layer surface cannot be suppressed, resulting in reduced heat resistance. If the average orientation density is 50 or more, the anisotropy of the crystal orientation of the tin layer is too high, causing the tin layer to crack during bending, resulting in poor bending conformability. The average value of this orientation density is preferably 0.1 or more and less than 40, and more preferably 0.3 or more and less than 30. Even if no nickel layer is provided as an underlayer, the terminal material can have excellent heat resistance.

[0010] In the connector terminal material of the present invention, the maximum value of the orientation density in the ranges of φ2=0°, φ1=60°-75°, and φ=0°-15° in the crystal orientation distribution function of the tin layer may be 0.1 or more and less than 55.

[0011] By setting the maximum value of the orientation density in the ranges of φ2 = 0°, φ1 = 60° to 75°, and φ = 0° to 15° in the crystal orientation distribution function of the tin layer to be 0.1 or more and less than 55, the diffusion of copper elements into the tin layer surface can be further suppressed, heat resistance can be further improved, and cracking of the tin layer during bending can be further prevented, resulting in excellent bending followability. If the maximum value of the orientation density is less than 0.1, the diffusion of copper elements into the tin layer surface cannot be suppressed, and if the maximum value of the orientation density is 55 or more, the anisotropy of the crystal orientation of the tin layer is too high, so the tin layer may crack during bending, preventing good bending followability. The maximum value of this orientation density is preferably 0.2 or more and less than 45, and more preferably 0.5 or more and less than 35.

[0012] In the terminal material for a connector of the present invention, the tin layer may have an average thickness of 0.2 μm or more and 1.7 μm or less.

[0013] The reason why the average thickness of the tin layer is set to 0.2 μm or more and 1.7 μm or less is that if it is less than 0.2 μm, the reliability of the electrical connection may be reduced, and if it exceeds 1.7 μm, the contact resistance will not be reduced, the plating cost will increase, and the dynamic friction coefficient may increase. The upper limit of the thickness of the tin layer is preferably 1.6 μm or less, and more preferably 1.5 μm or less.

[0014] In the terminal material for a connector of the present invention, a part of the copper-tin alloy layer is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is preferably 50% or less.

[0015] When a portion of the copper-tin alloy layer is exposed on the surface of the tin layer, the interface between the copper-tin alloy layer and the tin layer is formed in a steep uneven shape, and the area near the surface has a structure in which the tin in the tin layer and the copper-tin alloy are combined, and the soft tin between the hard copper-tin alloy layers acts as a lubricant, reducing the coefficient of dynamic friction and improving wear resistance. In this case, if the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer exceeds 50%, the electrical connection properties may be degraded. The lower limit of the exposed area ratio is 1%, preferably 1.5% or more, and the upper limit is 40% or less.

[0016] In the connector terminal material of the present invention, a nickel layer made of nickel or a nickel alloy and having an average thickness of 0.05 μm to 3.0 μm may be provided between the substrate and the copper-tin alloy layer, which prevents copper from diffusing from the substrate and further improves heat resistance. [Effects of the Invention]

[0017] According to the present invention, it is possible to obtain a terminal material for a connector that can suppress a decrease in contact resistance in a high-temperature environment, improve heat resistance, and prevent peeling or cracking of the coating during bending. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view schematically showing a first embodiment of a film-coated copper terminal material of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a second embodiment of the film-coated copper terminal material of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of the tin layer of Example 15 analyzed by EBSD at φ2=60°. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the terminal material for a connector of the present invention will be described.

[0020] (First embodiment) As shown in FIG. 1, the terminal material 1 for a connector of the first embodiment has a substrate 2 made of copper or a copper alloy, on which a copper-tin alloy layer 3 made of an alloy of copper and tin and a tin layer 4 made of tin or a tin alloy are formed in this order as coatings.

[0021] The substrate 2 is a strip material formed in the shape of a strip plate, and its composition is not particularly limited as long as it is made of copper or a copper alloy.

[0022] The copper-tin alloy layer 3 and the tin layer 4 are formed by forming a copper plating layer and a tin plating layer in this order on the substrate 2 and then performing a reflow treatment, as will be described later. 1, the copper-tin alloy layer 3 is composed of a Cu3Sn layer 3a partially formed on the substrate 2 and a Cu6Sn5 layer 3b formed on the Cu3Sn layer 3a or on the substrate 2 where the Cu3Sn layer 3a is not present, or formed so as to straddle these. The average thickness of the copper-tin alloy layer 3 is 0.1 μm or more and 1.5 μm or less. If the average thickness of the copper-tin alloy layer 3 is less than 0.1 μm, the wear resistance may increase, and if it exceeds 1.5 μm, the heat resistance may decrease.

[0023] The average thickness of the tin layer 4 is 0.2 μm or more and 1.7 μm or less. The reason for specifying the average thickness of the tin layer 4 as 0.2 μm or more and 1.7 μm or less is that if it is less than 0.2 μm, the reliability of the electrical connection may be reduced, and if it exceeds 1.7 μm, the contact resistance may not be reduced, the plating cost may increase, and the dynamic friction coefficient may increase. The average thickness of the tin layer 4 is preferably 1.6 μm or less, and more preferably 1.5 μm or less.

[0024] When the crystal orientation distribution function (ODF) obtained from texture analysis by EBSD (Electron Backscatter Diffraction) using the surface of this tin layer 4 as the observation surface is expressed in terms of Euler angles (φ1, φ, φ2), the average value of the orientation density in the ranges of φ2=60°, φ1=60°-75°, and φ=0°-15° is 0.05 or more and less than 50. In addition, the maximum value of the orientation density in the ranges of φ2=0°, φ1=60°-75°, and φ=0°-15° is 0.1 or more and less than 55.

[0025] By setting the average value of the orientation density within the ranges of φ2 = 60°, φ1 = 60° to 75°, and φ = 0° to 15° to be 0.05 or more and less than 50, the diffusion of copper elements into the surface of the tin layer 4 is suppressed, improving heat resistance, preventing cracking of the tin layer during bending, and providing excellent formability. If the average value of the orientation density is less than 0.05, the diffusion of copper elements into the surface of the tin layer 4 cannot be suppressed, resulting in reduced heat resistance. If the average value of the orientation density is 50 or more, the anisotropy of the crystal orientation of the tin layer 4 is too high, resulting in reduced bendability and cracking of the tin layer 4 during bending, which is closely related to the anisotropy of the crystal orientation, and therefore poor formability. The average value of this orientation density is preferably 0.1 or more and less than 40, and more preferably 0.3 or more and less than 30.

[0026] Furthermore, by setting the maximum value of the orientation density within the ranges of φ2 = 0°, φ1 = 60° to 75°, and φ = 0° to 15° to be 0.1 or more and less than 55, diffusion of copper elements into the surface of the tin layer 4 is further suppressed, heat resistance is further improved, and cracking of the tin layer during bending is further prevented, resulting in excellent formability. If the maximum value of the orientation density is less than 0.1, the effect of suppressing diffusion of copper elements into the surface of the tin layer 4 is poor. If the maximum value of the orientation density is 55 or more, the anisotropy of the crystal orientation of the tin layer 4 is too high, so that the tin layer 4 may crack during bending, preventing good formability. The maximum value of this orientation density is preferably 0.2 or more and less than 45, and more preferably 0.5 or more and less than 35.

[0027] A method for manufacturing the terminal material for connector 1 configured as above will be described. As the substrate 2, a plate made of copper or a copper alloy is prepared, and the surface of this plate is cleaned by degreasing, pickling, or other treatments. This substrate 2 is continuously run through a rolling process or the like, or is wound into a coil and continuously run while the coil is unwound. Copper plating and tin plating are applied to the surface of the continuously running substrate 2 in this order, thereby forming a copper plating layer and a tin plating layer in this order.

[0028] Copper plating can be performed using a general copper plating bath, such as a copper sulfate bath containing copper sulfate (CuSO4) and sulfuric acid (H2SO4) as its main components. The plating bath temperature is 20 to 50°C, and the current density is 1 A / dm 2 More than 50A / dm 2 The thickness of the copper plating layer formed by this copper plating is set to 0.05 μm or more and 1.0 μm or less.

[0029] A typical tin plating bath can be used as the plating bath for forming the tin plating layer, for example, a sulfuric acid bath containing sulfuric acid (H2SO4) and stannous sulfate (SnSO4) as the main components. The plating bath temperature is 15 to 35°C, and the current density is 1 A / dm 2 More than 30A / dm 2The thickness of the tin plating layer formed by this tin plating is set to 0.5 μm or more and 2.0 μm or less. If the thickness of the tin plating layer is less than 0.5 μm, the tin layer 4 after reflow treatment will be thin and electrical connectivity will be impaired, and if the thickness exceeds 2.0 μm, it will be difficult to achieve an average orientation density of the crystal orientation distribution function of 0.05 or more in the ranges of φ2=60°, φ1=60° to 75°, and Φ=0° to 15°.

[0030] In the reflow treatment, the substrate 2 that has been subjected to various plating treatments is heated while being continuously transported, and the plating layer is melted once and then cooled. Specifically, the plated material obtained by applying various platings to the substrate 2 is subjected to a heating step in which the plated material is heated to a temperature of 240°C to 350°C in a heating furnace in a CO reducing atmosphere, followed by a primary cooling step in which the material is cooled from the peak temperature to 230°C at a cooling rate of 30°C / sec or faster, a secondary cooling step in which the material is cooled from below 230°C to a temperature of 200°C or higher at a cooling rate of 10°C / sec or slower after the primary cooling, and a tertiary cooling step in which the material is cooled to room temperature (25°C) at a cooling rate of 100°C to 300°C / sec after the secondary cooling. The time required for this tertiary cooling step is 0.5 seconds to 2 seconds.

[0031] In the heating step, the plated material is preferably heated to a temperature of 240°C to 350°C at a rate of 20°C / sec to 75°C / sec for 3 to 15 seconds.

[0032] The primary and secondary cooling steps are carried out by air cooling, and the tertiary cooling step is carried out by water cooling using water at a temperature of 10° C. to 90° C. The cooling rate in the secondary cooling step is preferably 5° C. / sec or less, and more preferably 3° C. / sec or less. The cooling process is performed in three stages to control the solidification structure of the tin layer 4, thereby controlling the crystal orientation density. Specifically, by performing the primary cooling process at a cooling rate of 30°C / sec or higher, excessive growth of the copper-tin alloy layer 3 can be suppressed, preventing an excessive increase in contact resistance. Furthermore, a secondary cooling rate of 10°C / sec or lower controls the tin solidification structure to be formed, resulting in a solidification structure in which the average value of the orientation density in the ranges of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° in the crystal orientation distribution function of the tin layer 4 is 0.05 or more and less than 50, thereby improving heat resistance. The cooling rate in this secondary cooling step is preferably 1°C / sec or more and 10°C / sec or less. By setting the cooling rate to 1°C / sec or more, the maximum orientation density in the ranges of φ2=0°, φ1=60° to 75°, and Φ=0° to 15° can be set to 0.1 or more and less than 55, further improving heat resistance.

[0033] By performing such a reflow process, tin (Sn) is heated above its melting point and then cooled in three stages under the above conditions, of which the primary and secondary cooling stages can be adjusted as described above. Furthermore, by carrying out this reflow treatment in a reducing atmosphere, it is possible to prevent the formation of a tin oxide film with a high melting temperature on the surface of the tin layer 4, and to carry out the reflow treatment at a lower temperature in a shorter time.

[0034] The connector terminal material 1 manufactured in this manner has good electrical properties due to the tin layer 4 on the surface, and by controlling the crystal orientation density on the surface of this tin layer 4 as described above, it is possible to improve heat resistance and prevent peeling and cracking of the coating during bending processing.

[0035] (Second embodiment) In contrast to the first embodiment described above, in the second embodiment of the terminal material for connector 11, as shown in FIG. 2, a nickel layer 13 made of nickel or a nickel alloy is formed between the substrate 2 and the copper-tin alloy layer 12, and a copper-tin alloy layer 12 and a tin layer 14 are formed on the nickel layer 13.

[0036] The nickel layer 13 is formed by electrolytic plating of nickel or a nickel alloy on the surface of the base material 2, and is formed to a thickness of 0.05 μm or more and 3.0 μm or less. The provision of this nickel layer 13 makes it possible to prevent copper (Cu) from the base material 2 from diffusing into the coating. If the thickness of this nickel layer 13 is less than 0.05 μm, it is not very effective in preventing the diffusion of copper (Cu) from the base material 2, and the effect of improving heat resistance by preventing copper diffusion cannot be expected. If the thickness of this nickel layer 13 exceeds 3.0 μm, followability in bending and the like is reduced, which may result in cracks.

[0037] The copper-tin alloy layer 12 is formed by sequentially forming a nickel-plated layer, a copper-plated layer, and a tin-plated layer on the substrate 2 and then performing a reflow treatment. Although not shown, similar to the case of FIG. 1, it is composed of a partially formed Cu3Sn layer and a Cu6Sn5 layer formed on either the Cu3Sn layer or the nickel layer 13 where the Cu3Sn layer is not present, or spanning these layers. The average thickness of the copper-tin alloy layer 12 is 0.1 μm or more and 1.5 μm or less. The volume ratio of the Cu3Sn alloy layer 12a to the Cu6Sn5 alloy layer 12b is preferably 20% or less. The Cu6Sn5 layer may also be a compound alloy layer in which some of the copper (Cu) is replaced with nickel (Ni).

[0038] The average thickness of the tin layer 14 is the same as in the first embodiment, but a portion of the copper-tin alloy layer 12 is exposed on the surface of the tin layer 14. In this embodiment, the interface between the copper-tin alloy layer 12 and the tin layer 14 is formed in a steeply uneven shape, and the vicinity of the interface forms a composite structure of the copper-tin alloy layer 12 and the tin layer 14, with a portion of the copper-tin alloy layer 12 exposed on the surface of the tin layer 14. Therefore, the soft tin layer 14 is supported by the hard copper-tin alloy layer 12, which reduces the coefficient of friction and improves the insertion and removal properties of the connector. The exposed area ratio of this copper-tin alloy layer 12 on the surface of the tin layer 14 is 50% or less. If the exposed area ratio of the copper-tin alloy layer 12 exceeds 50%, the electrical connection characteristics may be degraded. The lower limit of the exposed area ratio is 1%, preferably 1.5% or more, and the upper limit is 40% or less. Furthermore, when the crystal orientation distribution function of the tin layer 14 obtained from texture analysis by EBSD with the surface of the tin layer 14 as the observation surface is expressed in terms of Euler angles (φ1, Φ, φ2), the average value of the orientation density in the ranges of φ2=60°, φ1=60°-75°, and Φ=0°-15° is 0.05 or more and less than 50, and the maximum value of the orientation density in the ranges of φ2=0°, φ1=60°-75°, and Φ=0°-15° is 0.1 or more and less than 55, which is the same as in the first embodiment.

[0039] To manufacture the terminal material for connector 11 of the second embodiment, nickel plating, copper plating, and tin plating may be applied in this order to the substrate 2, followed by a reflow treatment. The plating bath for nickel plating can be a general nickel plating bath, such as a Watts bath whose main components are nickel sulfate (NiSO4), nickel chloride (NiCl2), and boric acid (H3BO3). The plating bath temperature is between 20°C and 60°C, and the current density is 5 A / dm 2 More than 60A / dm 2 The following is said to be true. The copper plating, tin plating and reflow treatment are carried out under the same conditions as in the first embodiment.

[0040] In the connector terminal material 11 of the second embodiment, the interface between the copper-tin alloy layer 12 and the tin layer 14 is formed in a steeply uneven shape, which results in a composite structure in the vicinity of the interface between the tin layer 14 and the copper-tin alloy layer 12, in which the hard copper-tin alloy layer 12 supports the tin layer 14 directly below the soft tin layer 14, thereby reducing the coefficient of dynamic friction. Of course, since the outermost surface is mainly made of the tin layer 14, it has excellent electrical connectivity. Such a composite structure of a tin layer and a copper-tin alloy layer can also be formed by using a copper alloy containing nickel as the substrate without forming a nickel layer. [Example]

[0041] A copper alloy plate with a thickness of 0.25 mm was used as the substrate, and various plating processes were carried out under the following plating bath conditions. The film thicknesses of these plating layers were as shown in Table 1.

[0042] (copper plating) Copper sulfate: 250g / L Sulfuric acid: 50g / L Liquid temperature: 25℃ Current density: 5ASD(A / dm 2 (abbreviation; the same applies below)

[0043] (tin plating) Tin sulfate: 75g / L Sulfuric acid: 85g / L Additive: 10g / L Liquid temperature: 25℃ Current density: 2 ASD

[0044] Next, the substrate with the plating layer was subjected to a reflow treatment under the conditions shown in Table 1. After the reflow treatment, the thickness of the copper-tin alloy layer and the tin layer, the exposed area ratio of the copper-tin alloy layer on the tin layer surface, and the crystal orientation density on the tin layer surface were measured, and the heat resistance and processability were evaluated.

[0045] (Method for measuring the average thickness of the copper-tin alloy layer and the tin layer) The thicknesses of the tin layer and copper-tin alloy layer were measured using a fluorescent X-ray film thickness gauge (SEA5120A) manufactured by SII Nanotechnology Inc. To measure the thickness of the tin layer and copper-tin alloy layer, the thickness of the entire tin-containing film (copper-tin alloy layer and tin layer) was first measured for the reflowed sample. The tin layer was then removed by immersing the sample for 5 minutes in an etching solution for stripping the plating film, which contained components that did not corrode the copper-tin alloy layer. The thickness of the copper-tin alloy layer underneath was then measured and the average thickness of the copper-tin alloy layer was calculated. The average thickness of the tin layer was then defined as (thickness of the entire film including the tin layer - average thickness of the copper-tin alloy layer). Each thickness shown in Table 1 is the average of measurements at five locations.

[0046] (Method for measuring exposed area ratio of copper-tin alloy layer) The exposed area ratio of the copper-tin alloy layer was measured by removing the surface oxide film and then observing a 100 x 100 μm area with a scanning ion microscope. In terms of measurement principle, if the Cu6Sn5 alloy is present in the area approximately 20 nm deep from the outermost surface, it will appear white in the image. Therefore, using image processing software, the ratio of the area of ​​the white area to the area of ​​the measurement area was regarded as the exposed area ratio of the copper-tin alloy layer.

[0047] (Method for measuring the crystal orientation density on the surface of a tin layer) The crystal orientation density was measured by EBSD (Electron Backscatter Diffraction) using a scanning electron microscope (SU7000) manufactured by Hitachi High-Tech Corporation. The measurement conditions were a set voltage of 15 kV, a probe current value of Hi80, an objective aperture diameter of φ70 μm, a measurement area of ​​1000 μm x 1000 μm containing at least 100 crystal grains, and a scan step of 2 μm. This measurement was performed in 20 fields of view. To analyze the crystal grains after the measurement, the orientation distribution function (ODF) of the crystal grains was analyzed using OIM Analysis, an analytical software made by TSL. The crystal orientation distribution function obtained by the analysis was displayed in Euler angles. From the cross-sectional view at φ2 = 0°, the maximum value of the orientation density was read out in the range of φ2 = 0°, φ1 = 60° to 75°, and Φ = 0° to 15° (this range is called range 1). In addition, from the cross-sectional view at φ2 = 60° displayed in Euler angles, the average value of the orientation density was calculated in the range of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° (this range is called range 2).

[0048] The orientation density of the texture in this invention is the ratio of the strength of each orientation to the random orientation. Here, "random" means a texture in which the crystal orientations are uniformly dispersed and not concentrated, and is equal to the magnitude of the orientation density (concentration strength) on the ODF diagram. A similar definition of random orientation is given in JP 2008-303455 A. ODF displays three Euler angle variables (φ1, Φ, φ2) in a three-dimensional orientation space with rectangular coordinate axes. The Euler angles are shown in three directions: RD (parallel to the rolling direction within the tin-plated surface), TD (sheet width direction), and ND (normal to the rolling surface). The azimuthal rotation of the RD axis is shown as Φ, the azimuthal rotation of the ND axis as φ1, and the azimuthal rotation of the TD axis as φ2. While ODF should ideally be displayed in three dimensions, it is difficult to accurately display it using an isopycnal surface. Therefore, two-dimensional cross sections with constant φ2 or φ1 are often displayed at appropriate intervals. To quantitatively discuss texture using ODF analysis, an orientation distribution function is used to extract three-dimensional information from multiple pole figures (two-dimensional information), allowing texture quantification. The Euler angles are defined using Bunge's definition, and the peak intensity ratio is the ratio to the peak obtained when measuring β-Sn with random orientation. For each test material, the maximum value of the orientation density in range 1 and the average value of the orientation density in range 2 were determined.

[0049] (Evaluation of heat resistance) The contact resistance was measured after exposure to high temperatures in the atmosphere. The exposure conditions were 120°C for up to 1000 hours. The measurement method was a four-terminal contact resistance tester (Yamazaki Seiki Kenkyusho: CRS-113-AU), with the contact resistance measured using a sliding type (1 mm) load varying from 0 to 100 g, and the contact resistance value at a load of 100 g was used for evaluation. Contact resistance that was 5 mΩ or less after 1000 hours was rated "A," contact resistance that was greater than 5 mΩ but less than 10 mΩ was rated "B," and contact resistance that exceeded 10 mΩ after 1000 hours was rated "C."

[0050] (Evaluation of processing followability) Test pieces 10 mm wide and 60 mm long (with the long axis perpendicular to the rolling direction) were cut from the test material and bent 180 degrees with a curvature radius R of 1 mm. The bent parts were observed under an optical microscope and rated as follows: "A" indicates no cracks, peeling, or wrinkles in the coating; "B" indicates no cracks or peeling on the coating surface but micro-wrinkles; "C" indicates cracks or peeling on the coating surface but coarse wrinkles; and "D" indicates cracks or peeling but the substrate was exposed due to the coating cracks or peeling. The surface of the bent part was examined with a laser microscope; if the wrinkle width in the bent part was 30 μm or less, it was rated as micro-wrinkles, and if it was greater than 30 μm, it was rated as coarse wrinkles.

[0051] These results are shown in Table 1.

[0052] [Table 1]

[0053] As can be seen from Table 1, in the examples in which the average orientation density in the range 2 of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° was 0.05 or more and less than 50, the contact resistance remained low at 10 mΩ or less even after heating, and therefore the heat resistance was excellent.Furthermore, the processing followability was also good, with no cracks or peeling of the coating, and only slight wrinkles being observed on the surface. Among these, Examples 1 to 9, in which the maximum value of the orientation density in the range 1 of φ2=0°, φ1=60° to 75°, and Φ=0° to 15° is 0.1 or more and less than 55, have excellent processing followability, with even the worst possible processing followability being such that minute wrinkles are observed. In contrast, the comparative examples had average orientation densities of less than 0.05 or greater than 50 in the range 2 of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15°, and the evaluation of heat resistance showed an increase in contact resistance and poor processing followability.

[0054] Next, a sample was also prepared in which a nickel layer was formed between the substrate and the copper-tin alloy layer. The substrate and copper and tin plating conditions were the same as those in the previous example. (nickel plating) Nickel sulfate: 300g / L Sulfuric acid: 2g / L Liquid temperature: 45℃ Current density: 20ASD The reflow treatment was carried out under the conditions shown in Table 2. For the obtained samples, after reflow treatment, the thicknesses of the copper-tin alloy layer and the tin layer were measured in the same manner as described above, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer and the crystal orientation density on the surface of the tin layer were measured, and the heat resistance and processing followability were evaluated. The thickness of the nickel layer was also measured using a fluorescent X-ray film thickness meter (SEA5120A) manufactured by SII NanoTechnology Inc. The average thickness of the nickel layer was determined by averaging the measurements taken at five locations. The results are shown in Table 2.

[0055] [Table 2]

[0056] As can be seen from Table 2, in the examples where the average orientation density in the range 2 of φ2 = 60°, φ1 = 60° to 75°, and φ = 0° to 15° was 0.05 or more and less than 50, many of the examples had even better heat resistance than the results in Table 1, indicating that the formation of a nickel layer can result in an even better terminal material. Note that Table 2 lists the thickness of the nickel plating layer, and the average thickness of the nickel layer as a terminal material was also 0.05 μm or more and 3.0 μm or less. 3 shows a cross section of the tin layer of Example 15 analyzed by EBSD at φ2=60°, where the horizontal axis is φ1, the vertical axis is φ, and the grid line interval is 15°. The maximum value of the orientation density is 0.1 or more and less than 55 in the range of φ1=60° to 75° and Φ=0° to 15°. [Explanation of symbols]

[0057] 1. Connector terminal material 2 Base material 3 Copper-tin alloy layer 4 tin layer 11 Connector terminal materials 12 Copper-tin alloy layer 12a Cu3Sn layer 12b Cu6Sn5 layer 13 Nickel layer 14 Tin layer

Claims

1. A terminal material for a connector, comprising a substrate made of copper or a copper alloy, on which a copper-tin alloy layer and a tin layer made of tin or a tin alloy are laminated in this order, wherein when the crystal orientation distribution function of the tin layer obtained by texture analysis by EBSD with the surface of the tin layer as the observation surface is expressed in terms of Euler angles (φ1, Φ, φ2), the average value of the orientation density in the ranges of φ2 = 60°, φ1 = 60° to 75°, and Φ = 0° to 15° is 0.05 or more and less than 50.

2. 2. A terminal material for a connector as described in claim 1, wherein the maximum value of the orientation density in the ranges of φ2 = 0°, φ1 = 60° to 75°, and Φ = 0° to 15° in the crystal orientation distribution function of the tin layer is 0.1 or more and less than 55.

3. 3. The terminal material for a connector according to claim 1, wherein the tin layer has an average thickness of 0.2 μm or more and 1.7 μm or less.

4. A terminal material for a connector described in any one of claims 1 to 3, characterized in that a portion of the copper-tin alloy layer is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is 50% or less.

5. 5. The terminal material for a connector according to claim 1, further comprising a nickel layer made of nickel or a nickel alloy and having an average thickness of 0.05 μm or more and 3.0 μm or less between the substrate and the copper-tin alloy layer.

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